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+
+
+**ITU-T**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+**E.101**
+
+(11/2009)
+
+SERIES E: OVERALL NETWORK OPERATION,  
+TELEPHONE SERVICE, SERVICE OPERATION  
+AND HUMAN FACTORS
+
+International operation – Definitions
+
+---
+
+**Definitions of terms used for identifiers  
+(names, numbers, addresses and other  
+identifiers) for public telecommunication  
+services and networks in the E-series  
+Recommendations**
+
+Recommendation ITU-T E.101
+
+# ITU-T E-SERIES RECOMMENDATIONS **OVERALL NETWORK OPERATION, TELEPHONE SERVICE, SERVICE OPERATION AND HUMAN FACTORS**
+
+|                                                                                                              |                    |
+|--------------------------------------------------------------------------------------------------------------|--------------------|
+| <b>INTERNATIONAL OPERATION</b>                                                                               |                    |
+| <b>Definitions</b>                                                                                           | <b>E.100–E.103</b> |
+| General provisions concerning Administrations                                                                | E.104–E.119        |
+| General provisions concerning users                                                                          | E.120–E.139        |
+| Operation of international telephone services                                                                | E.140–E.159        |
+| Numbering plan of the international telephone service                                                        | E.160–E.169        |
+| International routing plan                                                                                   | E.170–E.179        |
+| Tones in national signalling systems                                                                         | E.180–E.189        |
+| Numbering plan of the international telephone service                                                        | E.190–E.199        |
+| Maritime mobile service and public land mobile service                                                       | E.200–E.229        |
+| <b>OPERATIONAL PROVISIONS RELATING TO CHARGING AND ACCOUNTING IN THE<br/>INTERNATIONAL TELEPHONE SERVICE</b> |                    |
+| Charging in the international telephone service                                                              | E.230–E.249        |
+| Measuring and recording call durations for accounting purposes                                               | E.260–E.269        |
+| <b>UTILIZATION OF THE INTERNATIONAL TELEPHONE NETWORK FOR NON-<br/>TELEPHONY APPLICATIONS</b>                |                    |
+| General                                                                                                      | E.300–E.319        |
+| Phototelegraphy                                                                                              | E.320–E.329        |
+| <b>ISDN PROVISIONS CONCERNING USERS</b>                                                                      | E.330–E.349        |
+| <b>INTERNATIONAL ROUTING PLAN</b>                                                                            | E.350–E.399        |
+| <b>NETWORK MANAGEMENT</b>                                                                                    |                    |
+| International service statistics                                                                             | E.400–E.404        |
+| International network management                                                                             | E.405–E.419        |
+| Checking the quality of the international telephone service                                                  | E.420–E.489        |
+| <b>TRAFFIC ENGINEERING</b>                                                                                   |                    |
+| Measurement and recording of traffic                                                                         | E.490–E.505        |
+| Forecasting of traffic                                                                                       | E.506–E.509        |
+| Determination of the number of circuits in manual operation                                                  | E.510–E.519        |
+| Determination of the number of circuits in automatic and semi-automatic operation                            | E.520–E.539        |
+| Grade of service                                                                                             | E.540–E.599        |
+| Definitions                                                                                                  | E.600–E.649        |
+| Traffic engineering for IP-networks                                                                          | E.650–E.699        |
+| ISDN traffic engineering                                                                                     | E.700–E.749        |
+| Mobile network traffic engineering                                                                           | E.750–E.799        |
+| <b>QUALITY OF TELECOMMUNICATION SERVICES: CONCEPTS, MODELS, OBJECTIVES<br/>AND DEPENDABILITY PLANNING</b>    |                    |
+| Terms and definitions related to the quality of telecommunication services                                   | E.800–E.809        |
+| Models for telecommunication services                                                                        | E.810–E.844        |
+| Objectives for quality of service and related concepts of telecommunication services                         | E.845–E.859        |
+| Use of quality of service objectives for planning of telecommunication networks                              | E.860–E.879        |
+| Field data collection and evaluation on the performance of equipment, networks and services                  | E.880–E.899        |
+| <b>OTHER</b>                                                                                                 | E.900–E.999        |
+| <b>INTERNATIONAL OPERATION</b>                                                                               |                    |
+| Numbering plan of the international telephone service                                                        | E.1100–E.1199      |
+| <b>NETWORK MANAGEMENT</b>                                                                                    |                    |
+| International network management                                                                             | E.4100–E.4199      |
+
+*For further details, please refer to the list of ITU-T Recommendations.*
+
+## **Recommendation ITU-T E.101**
+
+# **Definitions of terms used for identifiers (names, numbers, addresses and other identifiers) for public telecommunication services and networks in the E-series Recommendations**
+
+## **Summary**
+
+The purpose of Recommendation ITU-T E.101 is to define basic terms in the area of identifiers covering names, numbers, addresses and other identifiers in the ITU-T E-series Recommendations.
+
+### **History**
+
+| Edition | Recommendation | Approval   | Study Group |
+|---------|----------------|------------|-------------|
+| 1.0     | ITU-T E.101    | 2009-11-24 | 2           |
+
+## FOREWORD
+
+The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis.
+
+The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics.
+
+The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1.
+
+In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC.
+
+### NOTE
+
+In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some other obligatory language such as "must" and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party.
+
+### INTELLECTUAL PROPERTY RIGHTS
+
+ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process.
+
+As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at <http://www.itu.int/ITU-T/ipr/>.
+
+© ITU 2010
+
+All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU.
+
+## CONTENTS
+
+|                                                                                       | Page |
+|---------------------------------------------------------------------------------------|------|
+| 1 Scope/Introduction.....                                                             | 1    |
+| 2 References.....                                                                     | 1    |
+| 3 Definitions of terms for the different types of plans.....                          | 2    |
+| 4 Definitions of terms for generic and specific resources used in the plans.....      | 3    |
+| 5 Definitions of terms for the structure and sub-parts of specific resources .....    | 5    |
+| 6 Definitions of terms concerning administrative aspects for plans and resources..... | 7    |
+| 7 Abbreviations.....                                                                  | 8    |
+| Bibliography.....                                                                     | 10   |
+
+
+
+### Recommendation ITU-T E.101
+
+## Definitions of terms used for identifiers (names, numbers, addresses and other identifiers) for public telecommunication services and networks in the E-series Recommendations
+
+### 1 Scope/Introduction
+
+This Recommendation provides terms and definitions for use in the field of identifiers (e.g., names, numbers, addresses and other identifiers (IDs)) for public telecommunication services and networks. The purpose of this set of definitions is to aid in the understanding of different IDs used in different telecommunication networks and related Recommendations. Consistent terminology is seen as an important factor in ITU-T Recommendations, especially in Recommendations having some form of regulatory implications. For the area covering *Identifiers*, there are important Recommendations in the E-/F-series, but also in the Q- and X-series. The E-/F-series Recommendations falls under the responsibility of Study Group 2 (SG 2) and the Q-series is under SG 11, and SG 13 covers the X-series Recommendations.
+
+These terms and definitions have been developed, for the most part, from the practice of the use of IDs in traditional telephone networks such as PSTN, ISDN and PLMN-based networks (e.g., 1G and 2G).
+
+These terms will continue to be applicable with their current definitions for other telecommunication networks like NGNs, 3G-based PLMNs and other IP-based networks.
+
+Alternatives for the preferred terms are given following a semi-colon.
+
+The listings of the terms contain the following:
+
+- Definition of terms for different types of plans (clause 3).
+- Definition of generic terms for resources used in the plans (clause 4).
+- Definition of terms for specific resources used in the plans (clause 4).
+- Definition of terms for the structure and sub-parts of specific resources (clause 5).
+- Definition of terms concerning administrative aspects for plans and resources (clause 6).
+
+Every time a new Recommendation within the E-series is developed or an existing Recommendation is modified or deleted, this Recommendation shall be reviewed accordingly to ensure the information is accurate and up to date.
+
+### 2 References
+
+The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation.
+
+[ITU-T E.118] Recommendation ITU-T E.118 (2006), *The international telecommunication charge card*.
+
+[ITU-T E.161.1] Recommendation ITU-T E.161.1 (2008), *Guidelines to select Emergency Number for public telecommunications networks*.
+
+- [ITU-T E.164] Recommendation ITU-T E.164 (2005), *The international public telecommunication numbering plan.*
+- [ITU-T E.190] Recommendation ITU-T E.190 (1997), *Principles and responsibilities for the management, assignment and reclamation of E-series international numbering resources.*
+- [ITU-T E.191] Recommendation ITU-T E.191 (2000), *B-ISDN addressing.*
+- [ITU-T E.191.1] Recommendation ITU-T E.191.1 (2001), *Criteria and procedures for the allocation of ITU-T International Network Designator addresses.*
+- [ITU-T E.195] Recommendation ITU-T E.195 (2000), *ITU-T International numbering resource administration.*
+- [ITU-T E.212] Recommendation ITU-T E.212 (2008), *The international identification plan for public networks and subscriptions.*
+- [ITU-T E.910] Recommendation ITU-T E.910 (2005), *Procedures for registration within the domain ".int".*
+- [ITU-T Y.2091] Recommendation ITU-T Y.2091 (2008), *Terms and definitions for Next Generation Networks.*
+- [WTSA-08 Res.2] WTSA-08 – Resolution 2, *ITU-T study group responsibility and mandates.*
+
+### 3 Definitions of terms for the different types of plans
+
+This clause consists of terms for different naming, numbering and addressing plans. The concept diagram below gives an example of some of these plans.
+
+![A hierarchical diagram showing the classification of plans. The root is 'Plan; Scheme', which branches into 'Numbering plan', 'Addressing plan', 'Naming plan', and 'Identification plan'. 'Numbering plan' branches into 'Private numbering plan', 'E.164 numbering plan', and 'X.121 numbering plan'. 'E.164 numbering plan' further branches into 'Dialling plan', which then branches into 'Closed dialling plan' and 'Open dialling plan'. 'Addressing plan' branches into 'Q.708 addressing plan'. 'Identification plan' branches into 'E.118 Identification plan' and 'E.212 Identification plan'.](d0abac95583b52a3b35f74a215567334_img.jpg)
+
+```
+
+graph TD
+    Root[Plan; Scheme] --> NP[Numbering plan]
+    Root --> AP[Addressing plan]
+    Root --> NamP[Naming plan]
+    Root --> IP[Identification plan]
+    NP --> PNP[Private numbering plan]
+    NP --> E164NP[E.164 numbering plan]
+    NP --> X121NP[X.121 numbering plan]
+    E164NP --> DP[Dialling plan]
+    DP --> CDP[Closed dialling plan]
+    DP --> ODP[Open dialling plan]
+    AP --> Q708AP[Q.708 addressing plan]
+    IP --> E118IP[E.118 Identification plan]
+    IP --> E212IP[E.212 Identification plan]
+  
+```
+
+A hierarchical diagram showing the classification of plans. The root is 'Plan; Scheme', which branches into 'Numbering plan', 'Addressing plan', 'Naming plan', and 'Identification plan'. 'Numbering plan' branches into 'Private numbering plan', 'E.164 numbering plan', and 'X.121 numbering plan'. 'E.164 numbering plan' further branches into 'Dialling plan', which then branches into 'Closed dialling plan' and 'Open dialling plan'. 'Addressing plan' branches into 'Q.708 addressing plan'. 'Identification plan' branches into 'E.118 Identification plan' and 'E.212 Identification plan'.
+
+F03.doc
+
+**3.1 addressing plan:** An addressing plan specifies the format and structure of addresses used within that plan.
+
+**3.2 closed dialling plan:** A dialling plan where the national (significant) numbers [N(S)N] are used when dialling geographic numbers.
+
+**3.3 dialling plan** [ITU-T E.164]: A string or combination of decimal digits, symbols, and additional information that defines the method by which the numbering plan is used. A dialling plan
+
+includes the use of prefixes, suffixes, and additional information, supplemental to the numbering plan, required to complete the call.
+
+**3.4 E.164 numbering plan:** A type of numbering plan that specifies the format and structure of the numbers used within that plan. It typically consists of decimal digits segmented into groups in order to identify specific elements used for identification, routing and charging capabilities, e.g., to identify countries, national destinations and subscribers. An E.164 numbering plan does not include prefixes, suffixes, and additional information required to complete a call. The national numbering plan (NNP) is the national implementation of the international E.164-numbering plan (also called the international public telecommunication numbering plan).
+
+**3.5 identification plan:** A plan that specifies the format and structure of non-dialable identifiers for telecommunication networks used for network functions/elements/equipment or used for other administrative aspects of networks.
+
+**3.6 naming plan:** A plan that specifies the format and structure of the names used within telecommunication networks.
+
+**3.7 numbering plan:** A plan that specifies the format and structure of the numbers used within telecommunication networks. The numbers in the plan can either have uniform length or variable length or include both numbers of uniform and variable lengths.
+
+**3.8 open dialling plan:** A dialling plan where both numbers on the local level (subscriber numbers (SN) without area code) and numbers on the national level are used when dialling geographic numbers.
+
+**3.9 plan; scheme:** A plan/scheme specifies the format and structure of identifiers used within a telecommunication network.
+
+**3.10 private numbering plan (PNP):** A numbering plan that specifies the format and structure of the numbers used within an organization's private/enterprise telecommunication network. PNPs may be wholly separate from the E.164 numbering plan or may overlap with it, e.g., in the case of direct-dial-in (DDI).
+
+### 4 Definitions of terms for generic and specific resources used in the plans
+
+This clause consists of terms for generic and specific resources used in the different plans. The concept diagram below gives an example of different identifiers mostly from the E.164 numbering plan.
+
+![A hierarchical diagram showing the classification of identifiers. The root is 'Identifier', which branches into 'Name', 'Number', and 'Address'. 'Name' branches to 'Domain name'. 'Number' branches into 'Telephone number' and '[X.121] Data number'. 'Telephone number' branches into 'E.164 number' and 'National-only number'. 'E.164 number' branches into 'International E.164 number' and 'National E.164 number'. 'National-only number' branches into 'e.g. 112, 116 in EU MS and EAC' and '...'. '[X.121] Data number' branches into 'International data number' and 'National data number'.](99bae07626f60f9ede10e2e387ef7051_img.jpg)
+
+```
+graph TD; Identifier --> Name; Identifier --> Number; Identifier --> Address; Name --> Domain_name[Domain name]; Number --> Telephone_number[Telephone number]; Number --> X121_Data_number["[X.121] Data number"]; Telephone_number --> E164_number[E.164 number]; Telephone_number --> National_only_number[National-only number]; E164_number --> International_E164_number[International E.164 number]; E164_number --> National_E164_number[National E.164 number]; National_only_number --> e112_116["e.g. 112, 116 in EU MS and EAC"]; National_only_number --> dots["..."]; X121_Data_number --> International_data_number[International data number]; X121_Data_number --> National_data_number[National data number];
+```
+
+A hierarchical diagram showing the classification of identifiers. The root is 'Identifier', which branches into 'Name', 'Number', and 'Address'. 'Name' branches to 'Domain name'. 'Number' branches into 'Telephone number' and '[X.121] Data number'. 'Telephone number' branches into 'E.164 number' and 'National-only number'. 'E.164 number' branches into 'International E.164 number' and 'National E.164 number'. 'National-only number' branches into 'e.g. 112, 116 in EU MS and EAC' and '...'. '[X.121] Data number' branches into 'International data number' and 'National data number'.
+
+F04.doc
+
+- 4.1 address:** An address identifies a specific network termination point and can be used for routing to this physical and logical termination point inside a public or private network.
+- 4.2 code:** A character or a sequence of characters, digits or symbols used as an identifier.
+- 4.3 domain name [ITU-T E.910]:** An alphanumeric name that, when combined with an Internet top level domain (TLD), represents a unique name which is the sequence of labels from the node at the root of the domain to the root of the whole tree, with dots separating the labels.
+- 4.4 E.164 number:** A string of decimal digits that satisfies the three characteristics of structure, number length and uniqueness specified in [ITU-T E.164]. The number contains the information necessary to route the call to the end user or to a point where a service is provided.
+- 4.5 emergency number:** A national-only number allocated in the national numbering plan to enable emergency calls. Normally, the emergency number is a short code. Countries with integrated numbering plans may have the same number allocated as an emergency number within each country.
+- 4.6 geographic number (GN) [b-ITU-T E.164-Sup.2]:** An E.164 number which corresponds to a discrete geographic area.
+- 4.7 global number:** NOTE – See "International E.164 number".
+- 4.8 identifier (ID):** A series of digits, characters and symbols used to identify uniquely a subscriber, a user, a network element, a function, a network entity, a service or an application. Identifiers can be used for registration or authorization. They can be either public to all networks or private to a specific network (private IDs are normally not disclosed to third parties).
+- 4.9 international E.164 number; international public telecommunication number; international number:** A string of decimal digits that, for a geographic country code, uniquely identifies a subscriber or a point where a service is provided. For the case of a global service code, it identifies the subscriber of the service. For Networks, it identifies a subscriber of the Network. An international E.164 number can act in the "role" of both a name and an address. Portability is reducing a number's role as an address. Numbers are increasingly acting in the role of a name only. The number, which includes the country code and subsequent digits, but not the international prefix, contains the information necessary to route the call to this termination point on a public network (it may also contain the supplementary information necessary to forward it on a private network). It is sometimes referred to as an "international number".
+- In [b-IETF RFC 3966], which defines tel URI notation for telephone numbers, an international E.164 number is referred to as a global number.
+- 4.10 international numbering resource [ITU-T E.190]:** A numbering resource derived from an international number plan and assigned by ITU-T, e.g., [ITU-T E.164] and [ITU-T E.212].
+- 4.11 local number:** NOTE – See "National E.164 number" and "National-only number".
+- 4.12 MSISDN; mobile directory number:** The mobile E.164 number used by the calling party to establish a call to the end user.
+- 4.13 name:** A name is a combination of characters and is used to identify entities (e.g., subscriber, network element) that may be resolved/translated into an address. Characters may include numbers, letters and symbols.
+- 4.14 national E.164 number:** The national numbering plan (NNP) and the national dialling plan are defined by the national Numbering Plan Administrator. These plans are based on and consistent with [ITU-T E.164] and define the prefixes, national-only numbers and how the national formats (both at the local and national level) of the international E.164 numbers are structured and allocated.
+- On the national level, the E.164 number is structured through the national (significant) number [N(S)N] format, i.e., the national destination code (NDC) and the subscriber number (SN), not
+
+including, if present, the national (trunk) prefix. In some cases, the NDC could be absent or form part of the SN, and in that case the N(S)N and the SN coincide.
+
+In [b-IETF RFC 3966], which defines tel URI notation for telephone numbers, a national E.164 number is referred to as one type of local number.
+
+**4.15 national-only number:** Any telephone number, defined inside a national numbering plan (NNP), which is only used and meaningful in the national dialling plan and is not reachable from abroad. Such numbers do not belong to the international E.164 numbering plan nor do they conform to the structure of international E.164 numbers, as defined in [ITU-T E.164]. Countries in an integrated numbering plan may have different national-only numbers.
+
+In [b-IETF RFC 3966], which defines tel URI notation for telephone numbers, a national-only number is referred to as one type of local number.
+
+**4.16 non-geographic number** [b-ITU-T E.164-Sup.2]: An E.164 number which has no geographic significance.
+
+**4.17 number** [ITU-T E.191]: A number is a string of decimal digits.
+
+**4.18 routing address; routing number:** An address/number, only used for routing purposes and not known by end users, that is derived and used by the public telecommunication network to route the call/session towards the network termination point. This address/number can also be used to route calls towards a ported number.
+
+**4.19 service number** [b-ITU-T E.164-Sup.2]; **universal service number:** A non-geographic E.164 number allocated to a specific category of services.
+
+**4.20 short code:** String of digits in the national numbering plan (NNP), as defined by the national Numbering Plan Administrator, which can be used as a complete dialling sequence on public networks to access a specific type of service/network. The length of a short code is normally shorter than a subscriber number. In some countries, or in countries in an integrated numbering plan, the short code could be a national-only number.
+
+**4.21 tel URI:** The tel URI is the representation of an E.164 number or national-only number with the context defined signalling information. This is one URI scheme that conveys telephone numbers in SIP context and defines an identifier associated to a network termination point (NTP) or a service/application.
+
+**4.22 telephone number; phone number; directory number (DN):** The number, derived from the E.164 numbering plan, used by the calling party to establish a call to an end user or a service. The number may also be used for presentation services like calling line identification presentation (CLIP) and connected line identification presentation (COLP) and may also be published in different directories and/or directory enquiry services.
+
+### 5 Definitions of terms for the structure and sub-parts of specific resources
+
+This clause consists of terms for the structure and sub-parts of specific resources. The concept diagram below gives an example of the relationship for the structure and sub-parts of an international E.164 number.
+
+![A hierarchical diagram showing the structure of an Identifier. At the top is 'Identifier', which branches into 'Name', 'Number', and 'Address'. 'Number' branches into 'Telephone number'. 'Telephone number' branches into 'E.164 number' and 'National-only number' (with an example 'e.g. 112, 116 in EU MS/EAC'). 'E.164 number' branches into 'International E.164 number' and 'National E.164 number'. 'International E.164 number' branches into 'Country code (CC)' and 'National (significant) number [N(S)N]'. 'National (significant) number [N(S)N]' branches into 'National destination code (NDC)' and 'Subscriber number (SN)'. 'National destination code (NDC)' branches into 'Trunk code (TC)' and 'Destination network code (DN)'. A label 'F05.doc' is in the bottom right.](d4af765160d04ecef538e5066006dc77_img.jpg)
+
+```
+
+graph TD
+    Identifier --> Name
+    Identifier --> Number
+    Identifier --> Address
+    Number --> Telephone_number[Telephone number]
+    Telephone_number --> E164_number[E.164 number]
+    Telephone_number --> National_only_number[National-only number]
+    National_only_number --> Example["e.g. 112, 116 in EU MS/EAC"]
+    National_only_number --> Dots["..."]
+    E164_number --> International_E164_number[International E.164 number]
+    E164_number --> National_E164_number[National E.164 number]
+    International_E164_number --> Country_code[Country code (CC)]
+    International_E164_number --> National_significant_number["National (significant) number [N(S)N]"]
+    National_significant_number --> National_destination_code[National destination code (NDC)]
+    National_significant_number --> Subscriber_number[Subscriber number (SN)]
+    National_destination_code --> Trunk_code[Trunk code (TC)]
+    National_destination_code --> Destination_network_code[Destination network code (DN)]
+  
+```
+
+F05.doc
+
+A hierarchical diagram showing the structure of an Identifier. At the top is 'Identifier', which branches into 'Name', 'Number', and 'Address'. 'Number' branches into 'Telephone number'. 'Telephone number' branches into 'E.164 number' and 'National-only number' (with an example 'e.g. 112, 116 in EU MS/EAC'). 'E.164 number' branches into 'International E.164 number' and 'National E.164 number'. 'International E.164 number' branches into 'Country code (CC)' and 'National (significant) number [N(S)N]'. 'National (significant) number [N(S)N]' branches into 'National destination code (NDC)' and 'Subscriber number (SN)'. 'National destination code (NDC)' branches into 'Trunk code (TC)' and 'Destination network code (DN)'. A label 'F05.doc' is in the bottom right.
+
+**5.1 area code:** The combination of the national (trunk) prefix and the trunk code (TC) that identifies a specific geographic region/numbering area of the national numbering plan (NNP).
+
+**5.2 country code (CC):** Country codes are used to identify either a specific country, countries in an integrated numbering plan, a specific geographic area, a group of countries, a Network or global services.
+
+**5.3 international prefix [ITU-T E.164]:** A digit or combination of digits used to indicate that the number following is an international E.164-number.
+
+**5.4 mobile country code (MCC) [ITU-T E.212]:** The MCC is the first field of the IMSI and is three digits in length and identifies a country. The Director of TSB may assign more than one MCC to a country. MCCs in the 90x range are administered by the Director of TSB.
+
+**5.5 national destination code (NDC):** A nationally optional code field, within the international public telecommunication numbering plan (hereafter referred to as the "international E.164-numbering plan"), which – combined with the subscriber's number (SN) – will constitute the national (significant) number of the international E.164-number for geographic areas.
+
+The NDC can be a decimal digit or a combination of decimal digits (not including any prefix) identifying a numbering area within a country (or group of countries included in one integrated numbering plan or a specific geographic area) and/or network/services.
+
+**5.6 national (significant) number [N(S)N]:** That portion of the international E.164 number that follows the country code for geographic areas and is defined in national numbering plans (NNP). The national (significant) number consists of the national destination code (NDC), if present, and the subscriber number (SN). In some cases, the NDC could be absent or form part of the SN, and in that case the N(S)N and the SN coincide. The function and format of the N(S)N is nationally determined.
+
+**5.7 national (trunk) prefix:** A digit or combination of digits defined in a dialling plan and used by a calling subscriber, making a call to a subscriber in his own country but outside his own numbering area.
+
+**5.8 prefix:** A prefix is an indicator consisting of one or more digits that allows the selection of different types of number formats, networks and/or services. Prefixes are part of the dialling plan and do not form part of the numbering plan.
+
+**5.9 subscriber number (SN):** The portion of the E.164 number that identifies a subscriber in a network or numbering area.
+
+**5.10 trunk code (TC) [ITU-T E.164]:** A digit or combination of digits, not including the national (trunk) prefix, identifying the numbering area within a country (or group of countries included in one integrated numbering plan or a specific geographic area).
+
+The trunk code has to be used before the called subscriber's number when the calling and called subscribers are in different numbering areas. The trunk code is a particular application of NDC.
+
+### **6 Definitions of terms concerning administrative aspects for plans and resources**
+
+**6.1 administrator:** The organization, on a global, regional or national level, entrusted with the administration of a resource derived from a numbering, naming or addressing plan.
+
+**6.2 allocation:** The process of opening a numbering, naming or addressing resource in a plan for the purpose of its use by a telecommunication service under specified conditions. The allocation in itself does not yet give rights for any user, whether an operator, service provider, user or someone else, to use the resource.
+
+**6.3 applicant:** The petitioner applying for the assignment of a resource derived from a numbering, naming or addressing plan.
+
+**6.4 assignee:** The applicant to whom numbering, naming or addressing resources have been assigned.
+
+**6.5 assignment:** Authorization given to an applicant for the right of use of number, naming or addressing resources under specified conditions.
+
+**6.6 country [b-ITU-T E.164-Sup.3]:** A specific country, a group of countries in an integrated numbering plan or a specific geographical area.
+
+**6.7 national numbering plan administrator [ITU-T E.212]:** The organization (e.g., National Regulatory Authority/Administration) in charge of the administration of national naming, numbering and addressing plans.
+
+**6.8 numbering area:** A geographic area covered by a national destination code (NDC) or area code inside a national numbering plan (NNP).
+
+**6.9 operator [ITU-T E.212]:** An operating agency providing public telecommunication networks or public telecommunication services.
+
+**6.10 range; series:** A set of contiguous numbers or addresses identified by the first digit(s) (e.g., the range 1XX).
+
+**6.11 reclamation:** The process through which the right of use given to the assignee for the assigned number, name or address is withdrawn. The resource may be used for future potential re-assignment.
+
+**6.12 resource:** Codes, numbers, names, addresses and identifiers used in the provisioning of telecommunication services or the operations of the telecommunication networks offering such services.
+
+### 7 Abbreviations
+
+This Recommendation uses the following abbreviations:
+
+|        |                                            |
+|--------|--------------------------------------------|
+| 1G     | First Generation mobile networks           |
+| 2G     | Second Generation mobile networks          |
+| 3G     | Third Generation mobile networks           |
+| CC     | Country Code                               |
+| CLIP   | Calling Line Identification Presentation   |
+| COLP   | Connected Line Identification Presentation |
+| DDI    | Direct-Dial-In                             |
+| DN     | Directory Number<br>Destination Network    |
+| EAC    | East Africa Community                      |
+| EU     | European Union                             |
+| GN     | Geographic Number                          |
+| ID     | Identifier                                 |
+| IMSI   | International Mobile Subscription Identity |
+| ISDN   | Integrated Services Digital Network        |
+| LSPN   | Local Special Purpose Number               |
+| MCC    | Mobile Country Code                        |
+| MNC    | Mobile Network Code                        |
+| MSISDN | Mobile Subscriber ISDN Number              |
+| NDC    | National Destination Code                  |
+| NGN    | Next Generation Networks                   |
+| NNP    | National Numbering Plan                    |
+| NPA    | Numbering Plan Administrator               |
+| NRA    | National Regulatory Authority              |
+| N(S)N  | National (Significant) Number              |
+| NTP    | Network Termination Point                  |
+| PLMN   | Public Land Mobile Network                 |
+| PNP    | Private Numbering Plan                     |
+| PSTN   | Public Switched Telephone Network          |
+| RFC    | Request For Comments                       |
+| SIP    | Session Initiation Protocol                |
+| SN     | Subscriber Number                          |
+| TC     | Trunk Code                                 |
+| URI    | Uniform Resource Identifier                |
+
+## Bibliography
+
+- [b-ITU-T E.164-Sup.2] Recommendation E.164 – Supplement 2 (2009), *Number Portability*.
+- [b-ITU-T E.164-Sup.3] Recommendation E.164 – Supplement 3 (2004), *Operational and administrative issues associated with national implementations of the ENUM functions*.
+- [b-ETSI TR 184 005] ETSI TR 184 005 V1.1.1 (2007-11), *Types of numbers used in an NGN environment*.
+- [b-ETSI TS 184 002] ETSI TS 184 002 V1.1.1 (2006-10), *Identifiers (IDs) in NGN*.
+- [b-3GPP TR 21.905] 3GPP TR 21.905 V8.0.0 (2007-03), *Vocabulary for 3GPP specifications*.
+- [b-3GPP TS 23.003] 3GPP TS 23.003 (2008-12), *Numbering, addressing and identification*.
+- [b-IETF RFC 3966] IETF RFC 3966 (2004), *The tel URI for Telephone Numbers*.
+
+
+
+
+
+## SERIES OF ITU-T RECOMMENDATIONS
+
+|                 |                                                                                             |
+|-----------------|---------------------------------------------------------------------------------------------|
+| Series A        | Organization of the work of ITU-T                                                           |
+| Series D        | General tariff principles                                                                   |
+| <b>Series E</b> | <b>Overall network operation, telephone service, service operation and human factors</b>    |
+| Series F        | Non-telephone telecommunication services                                                    |
+| Series G        | Transmission systems and media, digital systems and networks                                |
+| Series H        | Audiovisual and multimedia systems                                                          |
+| Series I        | Integrated services digital network                                                         |
+| Series J        | Cable networks and transmission of television, sound programme and other multimedia signals |
+| Series K        | Protection against interference                                                             |
+| Series L        | Construction, installation and protection of cables and other elements of outside plant     |
+| Series M        | Telecommunication management, including TMN and network maintenance                         |
+| Series N        | Maintenance: international sound programme and television transmission circuits             |
+| Series O        | Specifications of measuring equipment                                                       |
+| Series P        | Terminals and subjective and objective assessment methods                                   |
+| Series Q        | Switching and signalling                                                                    |
+| Series R        | Telegraph transmission                                                                      |
+| Series S        | Telegraph services terminal equipment                                                       |
+| Series T        | Terminals for telematic services                                                            |
+| Series U        | Telegraph switching                                                                         |
+| Series V        | Data communication over the telephone network                                               |
+| Series X        | Data networks, open system communications and security                                      |
+| Series Y        | Global information infrastructure, Internet protocol aspects and next-generation networks   |
+| Series Z        | Languages and general software aspects for telecommunication systems                        |

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+
+
+![ITU logo](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg)
+
+The logo of the International Telecommunication Union (ITU) features a globe with a lightning bolt striking through it, symbolizing global communication.
+
+ITU logo
+
+INTERNATIONAL TELECOMMUNICATION UNION
+
+**ITU-T**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+**E.104**
+
+(02/95)
+
+**TELEPHONE NETWORK AND ISDN  
+OPERATION, NUMBERING, ROUTING  
+AND MOBILE SERVICE**
+
+---
+
+**INTERNATIONAL TELEPHONE DIRECTORY  
+ASSISTANCE SERVICE AND PUBLIC ACCESS**
+
+**ITU-T Recommendation E.104**
+
+(Previously "CCITT Recommendation")
+
+---
+
+# FOREWORD
+
+The ITU-T (Telecommunication Standardization Sector) is a permanent organ of the International Telecommunication Union (ITU). The ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis.
+
+The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics.
+
+The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Resolution No. 1 (Helsinki, March 1-12, 1993).
+
+ITU-T Recommendation E.104 was prepared by ITU-T Study Group 1 (1993-1996) and was approved under the WTSC Resolution No. 1 procedure on the 21st of February 1995.
+
+---
+
+# NOTE
+
+In this Recommendation, the expression “Administration” is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+# CONTENTS
+
+|                                                                                       | <i>Page</i> |
+|---------------------------------------------------------------------------------------|-------------|
+| 1 Introduction.....                                                                   | 1           |
+| 2 Scope.....                                                                          | 1           |
+| 3 Methods of obtaining information.....                                               | 1           |
+| 4 General principles applicable to the various methods of obtaining information ..... | 2           |
+| 5 Charging and accounting.....                                                        | 2           |
+| 6 Quality of service .....                                                            | 2           |
+
+# **SUMMARY**
+
+This Recommendation gives an overview of methods and general principles to be followed in organizing an International Telephone Directory Assistance Service.
+
+# **INTERNATIONAL TELEPHONE DIRECTORY ASSISTANCE SERVICE AND PUBLIC ACCESS**
+
+*(Geneva, 1994)*
+
+# **1 Introduction**
+
+The exchange of information relating to lists of subscribers within the international service is becoming increasingly intensive given the growth of international traffic and the increase in the number of people travelling abroad (business, tourism, etc.).
+
+To facilitate customers' use of international telephone network ROAs should provide an International Telephone Directory Assistance Service.
+
+# **2 Scope**
+
+This Recommendation gives an overview of methods and general principles to be followed on organizing an International Telephone Directory Assistance Service.
+
+# **3 Methods of obtaining information**
+
+The method to be followed in providing the customers and operators in one country with information of the national significant telephone numbers (as specified in Recommendation E.160) of subscribers in another country, depends on:
+
+- the way the information service is organized in the country of destination, distance between the countries, operating procedures, etc.;
+- the improvement and rationalization, sought by several ROAs for their national and international information services.
+
+The operator in the country of origin dealing with international inquiries should be able to obtain information, depending on the organization of the inquiry service in each country, by one of the following methods:
+
+- a) from telephone directories (see Recommendation E.114);
+- b) from other information systems received from foreign ROAs and kept up to date (e.g. microfiches);
+- c) by calling the appropriate information service operator in the country of destination (see Recommendation E.141):
+  - outgoing operators should, where language and other conditions permit, have direct access to the appropriate foreign information centre(s) which hold, or are able to obtain from other centres, up-to-date information;
+  - where language and other conditions do not permit the outgoing operator to have direct access to the appropriate foreign information centre, the outgoing operator should call the operator in the appropriate international exchange of the country of destination;
+  - where a ROA has distributed its information service to a number of information centres, provision should be made for access to a centralized international information centre or assistance operator in case the originating operator encounters language or other difficulties;
+- d) by having access to foreign information service computers (see Recommendation E.115):
+  - either via a local computer using appropriate procedures; or
+  - in special circumstances, via direct access using dedicated or switched connections.
+
+# 4 General principles applicable to the various methods of obtaining information
+
+In any relation, ROAs should abide by the following general principles:
+
+- a) Inquiries from customers concerning foreign subscribers' numbers should normally be addressed to operators in the country of origin who will obtain the required information; it may be useful to keep the customer on line while this information is being sought.
+- b) In order to give operators in the country of origin ready access to the international telephone inquiry services in other countries, it is desirable that ROAs, in conformity with Recommendation E.149, provide common routing codes or abbreviated access numbers to the foreign computerized or manual telephone inquiry services.
+
+ROAs should not communicate these access numbers to their subscribers.
+
+- c) Subscribers in one country may be permitted to have access to the information service in another country subject to bilateral agreement between the ROAs concerned.
+- d) An international system should be able to provide:
+  - for the desired correspondent: his international number;
+  - for the locality in which this correspondent resides: the country code and the national destination code;
+  - special numbers for other services.
+- e) No secret numbers should be issued.
+
+# 5 Charging and accounting
+
+The provisions concerning charging and accounting for the International Telephone Directory Assistance Service, if any, may be found in the D-Series Recommendations.
+
+# 6 Quality of service
+
+Quality of service involves a large number of different aspects, seen as well from the customers' side as from the ROA side. All of these different aspects/factors have an impact on the result which is presented to the customers. Some factors are:
+
+- An accurate answer to the customer, i.e. that a correct number is retrieved. This can involve difficulty, because sometimes the customer does not know the exact wording, locality name, etc., of the wanted company/person.
+- A multiplication of the different types of telecommunication numbers, i.e. telephone, mobile, fax, MHS, different ROAs. The calling customer may even not know to which ROA network the wanted person/company is connected.
+- A quick answer, that means that the average dialogue time between the customer and the operator must be treated with acceptable duration.
+- An acceptable average answering time when the customer calls the service provider.
+- Expectations of follow-on services.
+- ROAs costs for the service must match economical possibilities.
+- A reasonable answering time in the different computer systems involved in the service.
+- Feedback functions of different types between ROAs concerned.
+
+Awaiting standards to be set, every ROA must provide:
+
+- a technical fault report point, available 24 hours a day, 7 days a week;
+- an operator assistance point available 24 hours a day, 7 days a week;
+- an administrative report point, available normal office opening hours;
+- a computer response time and computer up-time that does not differ significantly from standards used in domestic service.

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+
+
+**ITU-T**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+**E.108**
+
+(01/2016)
+
+SERIES E: OVERALL NETWORK OPERATION,  
+TELEPHONE SERVICE, SERVICE OPERATION AND  
+HUMAN FACTORS
+
+International operation – General provisions concerning  
+Administrations
+
+# --- **Requirements for a disaster relief mobile message service**
+
+Recommendation ITU-T E.108
+
+## OVERALL NETWORK OPERATION, TELEPHONE SERVICE, SERVICE OPERATION AND HUMAN FACTORS
+
+|                                                                                                   |                    |
+|---------------------------------------------------------------------------------------------------|--------------------|
+| INTERNATIONAL OPERATION                                                                           |                    |
+| Definitions                                                                                       | E.100–E.103        |
+| <b>General provisions concerning Administrations</b>                                              | <b>E.104–E.119</b> |
+| General provisions concerning users                                                               | E.120–E.139        |
+| Operation of international telephone services                                                     | E.140–E.159        |
+| Numbering plan of the international telephone service                                             | E.160–E.169        |
+| International routing plan                                                                        | E.170–E.179        |
+| Tones in national signalling systems                                                              | E.180–E.189        |
+| Numbering plan of the international telephone service                                             | E.190–E.199        |
+| Maritime mobile service and public land mobile service                                            | E.200–E.229        |
+| OPERATIONAL PROVISIONS RELATING TO CHARGING AND ACCOUNTING IN THE INTERNATIONAL TELEPHONE SERVICE |                    |
+| Charging in the international telephone service                                                   | E.230–E.249        |
+| Measuring and recording call durations for accounting purposes                                    | E.260–E.269        |
+| UTILIZATION OF THE INTERNATIONAL TELEPHONE NETWORK FOR NON-TELEPHONY APPLICATIONS                 |                    |
+| General                                                                                           | E.300–E.319        |
+| Phototelegraphy                                                                                   | E.320–E.329        |
+| ISDN PROVISIONS CONCERNING USERS                                                                  | E.330–E.349        |
+| INTERNATIONAL ROUTING PLAN                                                                        | E.350–E.399        |
+| NETWORK MANAGEMENT                                                                                |                    |
+| International service statistics                                                                  | E.400–E.404        |
+| International network management                                                                  | E.405–E.419        |
+| Checking the quality of the international telephone service                                       | E.420–E.489        |
+| TRAFFIC ENGINEERING                                                                               |                    |
+| Measurement and recording of traffic                                                              | E.490–E.505        |
+| Forecasting of traffic                                                                            | E.506–E.509        |
+| Determination of the number of circuits in manual operation                                       | E.510–E.519        |
+| Determination of the number of circuits in automatic and semi-automatic operation                 | E.520–E.539        |
+| Grade of service                                                                                  | E.540–E.599        |
+| Definitions                                                                                       | E.600–E.649        |
+| Traffic engineering for IP-networks                                                               | E.650–E.699        |
+| ISDN traffic engineering                                                                          | E.700–E.749        |
+| Mobile network traffic engineering                                                                | E.750–E.799        |
+| QUALITY OF TELECOMMUNICATION SERVICES: CONCEPTS, MODELS, OBJECTIVES AND DEPENDABILITY PLANNING    |                    |
+| Terms and definitions related to the quality of telecommunication services                        | E.800–E.809        |
+| Models for telecommunication services                                                             | E.810–E.844        |
+| Objectives for quality of service and related concepts of telecommunication services              | E.845–E.859        |
+| Use of quality of service objectives for planning of telecommunication networks                   | E.860–E.879        |
+| Field data collection and evaluation on the performance of equipment, networks and services       | E.880–E.899        |
+| OTHER                                                                                             | E.900–E.999        |
+| INTERNATIONAL OPERATION                                                                           |                    |
+| Numbering plan of the international telephone service                                             | E.1100–E.1199      |
+| NETWORK MANAGEMENT                                                                                |                    |
+| International network management                                                                  | E.4100–E.4199      |
+
+For further details, please refer to the list of ITU-T Recommendations.
+
+## Recommendation ITU-T E.108
+
+# Requirements for a disaster relief mobile message service
+
+## Summary
+
+Recommendation ITU-T E.108 specifies requirements for a disaster relief mobile message service. In the aftermath of a disaster, communication facilities are often overloaded due to many users attempting to contact friends or relatives to determine the safety of people who may have been affected by disasters. As a result, communication attempts often fail. The intent of a disaster messaging service is to allow an alternate method to communicate safety status information. Two approaches are presented. The first is a text-based messaging system, and the second is a voice-based messaging system.
+
+## History
+
+| Edition | Recommendation | Approval   | Study Group | Unique ID*                                                                |
+|---------|----------------|------------|-------------|---------------------------------------------------------------------------|
+| 1.0     | ITU-T E.108    | 2016-01-29 | 2           | <a href="http://handle.itu.int/11.1002/1000/12449">11.1002/1000/12449</a> |
+
+---
+
+\* To access the Recommendation, type the URL <http://handle.itu.int/> in the address field of your web browser, followed by the Recommendation's unique ID. For example, <http://handle.itu.int/11.1002/1000/11830-en>.
+
+## FOREWORD
+
+The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis.
+
+The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics.
+
+The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1.
+
+In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC.
+
+## NOTE
+
+In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some other obligatory language such as "must" and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party.
+
+## INTELLECTUAL PROPERTY RIGHTS
+
+ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process.
+
+As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at <http://www.itu.int/ITU-T/ipr/>.
+
+© ITU 2016
+
+All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU.
+
+## Table of Contents
+
+###### Page
+
+|     |                                                                            |   |
+|-----|----------------------------------------------------------------------------|---|
+| 1   | Scope.....                                                                 | 1 |
+| 2   | References.....                                                            | 1 |
+| 3   | Definitions .....                                                          | 1 |
+| 3.1 | Terms defined elsewhere .....                                              | 1 |
+| 3.2 | Terms defined in this Recommendation.....                                  | 1 |
+| 4   | Abbreviation and acronyms.....                                             | 2 |
+| 5   | Conventions .....                                                          | 2 |
+| 6   | Background and concept.....                                                | 2 |
+| 6.1 | Background.....                                                            | 2 |
+| 6.2 | Concept of an IP message-based service.....                                | 2 |
+| 6.3 | Concept of IP voice-based service .....                                    | 4 |
+| 7   | Requirements for disaster message board service .....                      | 5 |
+| 7.1 | Message registration function.....                                         | 5 |
+| 7.2 | Uploading function.....                                                    | 6 |
+| 7.3 | Searching and displaying function .....                                    | 6 |
+| 7.4 | Notification delivery function (recommended) .....                         | 6 |
+| 7.5 | Deletion function .....                                                    | 6 |
+| 7.6 | Language requirements .....                                                | 6 |
+| 7.7 | Supplementary function: Auto-registration of self-safety information ..... | 7 |
+| 8   | Requirements for a disaster voice message delivery service.....            | 7 |
+| 8.1 | Registration function .....                                                | 7 |
+| 8.2 | Upload function (required) .....                                           | 7 |
+| 8.3 | Confirmation of registration at a calling server (required).....           | 8 |
+| 8.4 | Interoperator usage function (recommended) .....                           | 8 |
+| 8.5 | Notification of received voice at a called server (required) .....         | 8 |
+| 8.6 | Receiving and reproducing a voice message.....                             | 8 |
+|     | Bibliography.....                                                          | 9 |
+
+
+
+## Recommendation ITU-T E.108
+
+# Requirements for a disaster relief mobile message service
+
+# 1 Scope
+
+This Recommendation specifies requirements for a disaster relief mobile message service.
+
+After a disaster occurs, many people want to contact their immediate family, relatives or friends to report their condition. In many cases, communication is via telephone over the mobile or fixed telephone network. However, due to a large population of users attempting to make similar calls, they often fail to get through due to heavy network congestion.
+
+In contrast, the characteristics of Internet protocol (IP) packet networks are such that, although localized congestion may occur, the user does not experience blocking to the extent that communication is fully cut off, but still has the ability to transfer information, although with possibly reduced throughput.
+
+As an alternative to using a mobile or fixed telephone network after disasters occur, an IP-based disaster relief message service provided through the mobile network enables people to inform their friends and family members of their safety or of damage conditions.
+
+## 2 References
+
+The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; all users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation.
+
+[ITU-T E.164] Recommendation ITU-T E.164 (2010), *The international public telecommunication numbering plan*.
+
+## 3 Definitions
+
+### 3.1 Terms defined elsewhere
+
+This Recommendation uses the following term defined elsewhere:
+
+**3.1.1 disaster** [b-UNISDR, 2009]: A serious disruption of the functioning of a community or a society involving widespread human, material, economic or environmental losses and impacts, which exceeds the ability of the affected community or society to cope using its own resources.
+
+### 3.2 Terms defined in this Recommendation
+
+This Recommendation defines the following terms:
+
+**3.2.1 disaster relief**: Information or action to be effective for reduction and suppression of a serious disruption of the functioning of society. The disruption may be caused by accidents, natural phenomena or human activity, and results in a significant widespread threat to human life, health, property or the environment.
+
+**3.2.2 disaster relief system**: A system that provides disaster relief (response) services to related parties, which include affected victims, rescue workers and systems.
+
+**3.2.3 disaster message board service:** A type of disaster relief service that enables people to input text messages into a network-based message board facility for delivery to or retrieval by other people.
+
+**3.2.4 disaster voice message delivery service:** A type of disaster relief service that enables people to put packetized voice messages on to network facilities for delivery to or retrieval by other people.
+
+## 4 Abbreviation and acronyms
+
+This Recommendation uses the following abbreviations and acronyms:
+
+|    |                   |
+|----|-------------------|
+| DB | Database          |
+| IP | Internet Protocol |
+| PC | Personal Computer |
+
+## 5 Conventions
+
+None.
+
+# 6 Background and concept
+
+### 6.1 Background
+
+After a disaster, victims generally want to inform their friends and family members of their safety or of the damage situation. At the same time, the friends and family members not directly affected may also try to directly confirm the safety of the possible victims. Normally, the first attempt by both parties is to try to contact each other using either a mobile or fixed voice telephone network.
+
+However, call attempts may fail due to heavy congestion caused by the sudden increase of traffic and the possible drop of network capacity if the network itself is damaged by the disaster.
+
+In comparison with a real-time voice call service, a packet service can be employed to transfer messages related to safety confirmation or the damage situation in off-peak hours (or even in busy hours), if the service is designed as a store and forward service. Also, as a packet-based system, a disaster message board service (see clause 3.2.3) generally requires less network capacity than a voice telephony based service.
+
+The current generation of mobile phones provides a packetized data service. As many victims often flee a disaster situation taking with them a device such as a mobile phone, smartphone or tablet, a message system operating in conjunction with the mobile network is appropriate.
+
+Considering these situations above, two types of disaster relief (see clause 3.2.1) mobile services are possible; one is an IP message-based service and the other is an IP voice-based service.
+
+In the case of an IP-message based service, with a mobile phone victims can easily inform their friends and family members of their safety or of the damage situation. After the victim provides safety information (or information related to the damage situation) to a packet-based disaster relief system (see clause 3.2.2), their friends and family members can independently retrieve this information from the system.
+
+Some people may prefer a live voice-based communication system. In some situations, voice-based calls may be the only option for some (such as the aged or infirm). In this case, the system can allow storage of a digitized voice message, which can then be accessed by their friends and family members through the IP network.
+
+NOTE – The word "victim" in this document is the person who might be affected by disaster.
+
+### 6.2 Concept of an IP message-based service
+
+For an IP message-based service, victims can input into their mobile phone the disaster relief message, which may include information such as confirmation of their safety and the damage situation. The mobile phone terminal transfers the message to a server called a disaster message board via the mobile network.
+
+Their friends and family members can then access the server and retrieve this information by accessing the web through a mobile phone or Internet terminal.
+
+In addition, the user (victim) can arrange to have the message automatically delivered to specific mobile phone numbers to notify his safety-confirmation and damage situation.
+
+The concept of a disaster message board service is shown in Figure 1.
+
+![Diagram illustrating the Disaster message board service concept.](367926125450c2bc3f4bdca9d59a62ba_img.jpg)
+
+The diagram illustrates the Disaster message board service concept. On the left, a building is labeled "Earthquake". A person is shown with speech bubbles: "I cannot come home... I want to contact my family..." and "It is hard to phone home". Another person is shown with a speech bubble: "I will register on the 'Disaster message board'". A mobile phone displays the "Disaster MSG Board ~ register ~ [condition]" screen with the following options:  I am safe,  I am not safe,  I am at home,  I am at the evacuation centre. A green arrow labeled "Disaster message" points from the phone to a server icon. From the server, a green arrow labeled "[notification mail] sending" points to a woman's phone. A dashed green arrow labeled "Confirmation of safety received [notification mail]" points back from the woman's phone to the server. The woman has a speech bubble: "I am relieved to read that he is safe." Below the server, a dashed green arrow labeled "Confirmation of safety" points to an older couple. The man has a speech bubble: "Good!". A text box at the bottom right states: "You can access the disaster message board service even through other mobile phone networks or Internet (e.g., http://xxxx-yyyyy/)". The code "E.108(16)\_F01" is in the bottom right corner.
+
+Diagram illustrating the Disaster message board service concept.
+
+Figure 1 – Disaster message board service
+
+In some countries, disaster message board services may be independently provided by each service operator. In this case, to minimize the inconvenience to users, the system is required to provide a cross-search function to allow searching, even by foreign users, of all databases (DBs) for safety information provided by the users. By inputting the phone number of friends and family members, the message-receiving users can identify the situations of friends and family members after cross-searching as shown in Figure 2.
+
+![Figure 2: Cross-searching function on databases of different message boards. A mobile phone on the left shows a 'Disaster Message Board ~ Confirmation ~' screen with a text input field containing '090XXXXXXX' and a 'Search' button. An arrow points from the phone to a central 'Searching' box. From 'Searching', four arrows point to four database cylinders labeled DB:A, DB:B, DB:C, and DB:D. Below these is the text 'Cross-searching function'. An arrow points from DB:D to a second mobile phone on the right. This phone shows a 'Disaster Message Board ~ Confirmation ~' screen with the text 'The safety information that you would like to see follows: To Disaster Message Board by B-operator. Please note that a communication fee applies. To top of Disaster Message Board'. The text 'E.108(16)_F02' is at the bottom right.](a5ee5c23b6dc52ec1d724b76d5a5f58f_img.jpg)
+
+Figure 2: Cross-searching function on databases of different message boards. A mobile phone on the left shows a 'Disaster Message Board ~ Confirmation ~' screen with a text input field containing '090XXXXXXX' and a 'Search' button. An arrow points from the phone to a central 'Searching' box. From 'Searching', four arrows point to four database cylinders labeled DB:A, DB:B, DB:C, and DB:D. Below these is the text 'Cross-searching function'. An arrow points from DB:D to a second mobile phone on the right. This phone shows a 'Disaster Message Board ~ Confirmation ~' screen with the text 'The safety information that you would like to see follows: To Disaster Message Board by B-operator. Please note that a communication fee applies. To top of Disaster Message Board'. The text 'E.108(16)\_F02' is at the bottom right.
+
+**Figure 2 – Cross-searching function on databases of different message boards**
+
+The requirements for a disaster message board service are specified in clause 7.
+
+### 6.3 Concept of IP voice-based service
+
+For a voice-based service, first the victim inputs into their mobile phone the called (recipient) telephone number and a voice message confirming their safety or providing information on the damage situation. The called number is generally that of friends or family members. The voice message is then packetized in the phone and transferred to the server. The packetized message is sent from the server to the called number during non-busy hours.
+
+As a result, friends and family members can be provided with safety confirmation and information about the damage situation. The concept of a disaster voice message delivery service (see clause 3.2.4) is shown in Figure 3.
+
+![Figure 3: Disaster voice message delivery service. A mobile phone on the left shows a 'Disaster Voice Message Board ~ Calling side ~' screen with a text input field containing '090XXXXXXX' and a 'Recording' button. A speech bubble from a person next to it says, 'It is hard to phone home. I will try to use the "Disaster voice message delivery Service"'. A green arrow points from the phone to a central yellow box labeled 'Server for packet voice'. Inside the box is a server icon and two 'Voice file' icons. Below the box is the text 'Packet network'. A green arrow points from the server to a second mobile phone on the right. A speech bubble from a person next to it says, 'Confirmation of safety received via voice message'. Below the server box is the text 'Voice message is recorded, packetized and then sent'. The text 'E.108(16)_F03' is at the bottom right.](053f1077d592e6622cd21dc4bb4cb366_img.jpg)
+
+Figure 3: Disaster voice message delivery service. A mobile phone on the left shows a 'Disaster Voice Message Board ~ Calling side ~' screen with a text input field containing '090XXXXXXX' and a 'Recording' button. A speech bubble from a person next to it says, 'It is hard to phone home. I will try to use the "Disaster voice message delivery Service"'. A green arrow points from the phone to a central yellow box labeled 'Server for packet voice'. Inside the box is a server icon and two 'Voice file' icons. Below the box is the text 'Packet network'. A green arrow points from the server to a second mobile phone on the right. A speech bubble from a person next to it says, 'Confirmation of safety received via voice message'. Below the server box is the text 'Voice message is recorded, packetized and then sent'. The text 'E.108(16)\_F03' is at the bottom right.
+
+**Figure 3 – Disaster voice message delivery service**
+
+In some countries, disaster voice message delivery services may be independently provided by each service operator. In order to prevent restricted access to a user if the receiving user subscribes to a different operator, the system is required to provide an interoperator usage function to allow access to a disaster voice message delivery service provided by other operators.
+
+This function will provide a URL to allow all users, even foreign users, access to the disaster voice message delivery service. All users can then hear voice messages, as shown in Figure 4.
+
+![Diagram illustrating the interoperator use between different disaster voice message delivery services. A mobile phone on the left (calling side) sends a 'Packetize' request to a 'Server at calling centre DB:A'. The server stores the 'p-voice' (packetized voice recording) in 'DB:B' and 'DB:C'. The server sends a 'Confirmation' to the calling phone. The 'Server at calling centre DB:A' also sends 'p-voice' to a 'Server at called centre DB:D', which stores it in 'DB:D'. The 'Server at called centre DB:D' sends a 'Confirmation' to the calling server. The 'Server at called centre DB:D' then sends the 'p-voice' to the mobile phone on the right (called side). The called phone displays the message: 'Disaster Voice Message Delivery ~ Called side ~ Message is coming yy/mm/dd 16:05:06 Calling number:XXXXX Please access http://otodoke.docomo.co.ip/rx_vmco?en co=ip Mobile operator'.](cfef993dcc8fb513de79eb1f93cf26ae_img.jpg)
+
+Diagram illustrating the interoperator use between different disaster voice message delivery services. A mobile phone on the left (calling side) sends a 'Packetize' request to a 'Server at calling centre DB:A'. The server stores the 'p-voice' (packetized voice recording) in 'DB:B' and 'DB:C'. The server sends a 'Confirmation' to the calling phone. The 'Server at calling centre DB:A' also sends 'p-voice' to a 'Server at called centre DB:D', which stores it in 'DB:D'. The 'Server at called centre DB:D' sends a 'Confirmation' to the calling server. The 'Server at called centre DB:D' then sends the 'p-voice' to the mobile phone on the right (called side). The called phone displays the message: 'Disaster Voice Message Delivery ~ Called side ~ Message is coming yy/mm/dd 16:05:06 Calling number:XXXXX Please access http://otodoke.docomo.co.ip/rx\_vmco?en co=ip Mobile operator'.
+
+p-voice: packetized voice recording
+
+**Figure 4 – Interoperator use between different disaster voice message delivery services**
+
+The requirements for a disaster voice message delivery service are found in clause 8.
+
+# 7 Requirements for disaster message board service
+
+A disaster message board service is required to meet the functions described in clauses 7.1 to 7.7.
+
+### 7.1 Message registration function
+
+The service is required to allow a user to generate his or her message and register the message to the network system for retrieval by other users (message-receiving users). For the sake of ease of handling, the service is required to present a set of pre-defined messages to the user to allow the user to choose the appropriate messages rather than having to type the messages.
+
+#### 1) Items for registration:
+
+#### 1.1) Fixed menu of relief messages (required)
+
+- I am safe
+- I am not safe
+- I am at home
+- I am at the evacuation centre
+- other
+
+##### 1.2) Free text message (recommended)
+
+##### 1.3) Voice message (optional)
+
+##### 1.4) Video message (optional)
+
+#### 2) Terminals for registration
+
+The message is registered via a mobile phone terminal with a telephone number conforming to the format specified in [ITU-T E.164] (required).
+
+#### 3) Identification of the user
+
+Mobile phone users normally will carry their terminals. The message from the mobile terminal can be identified to be registered by the user. The message is used for safety confirmation or recognition of the damage situation of the user.
+
+### 7.2 Uploading function
+
+The registered message, which is selected from the menu or typed by a user, is sent and uploaded to a server for the "disaster message board". The service is required to accept and store user-generated messages, which can later be retrieved by other users (message-receiving users).
+
+### 7.3 Searching and displaying function
+
+The service is required to allow users other than the message-generating user to discover and read the message. This condition should be satisfied even if the message-generating user and other users subscribe to different network operators.
+
+- 1) DB and type of searching (required)
+  - To search a safety confirmation or damage situation within a DB of the operator which provides service to a user terminal for registration (see Figure 2).
+  - To cross-search a safety confirmation or damage situation in DBs of other operators (see Figure 2)
+  - To cross-search a safety confirmation or damage situation in DBs with the same [ITU-T E.164] country code.
+- 2) Terminal for searching:
+  - 2.1) Mobile phone terminal with web-access function (required)
+  - 2.2) PC and tablet PC (required)
+  - 2.3) Display (required)  
+Searched message to be displayed at a terminal
+
+### 7.4 Notification delivery function (recommended)
+
+It is recommended that the message be automatically delivered to mobile phone numbers specified by the user in advance, to confirm his/her safety and provide information about the damage situation. For this, it is necessary to:
+
+- 1) Pre-register the mobile phone numbers to be called by a potential message-generating user through the terminal for registration.
+- 2) Send the message defined in clause 7.1 from a server for the disaster message board to the pre-registered phone numbers.
+
+## 7.5 Deletion function
+
+The service is required to allow the message-generating user to update or delete the message. This function allows the message-generating user to:
+
+- 1) delete safety confirmation or damage situation information only through the terminal for registration (required);
+- 2) update a safety confirmation or damage situation only through the terminal for registration (required).
+
+## 7.6 Language requirements
+
+- 1) Local languages (required)
+- 2) English (recommended)
+- 3) Other language (optional).
+
+## 7.7 Supplementary function: Auto-registration of self-safety information
+
+This function is optional, but it may be implemented in some countries as an important function of disaster-relief applications.
+
+According to experience from past disaster relief applications, users (i.e., victims in an affected area) are quite eager to take action to learn about the situation of others (and their posted messages) while failing to inform others of their own condition, causing concern for others outside the affected area. To collect the conditions of the victims more efficiently in a confused situation, the automatic registration of a user's condition is desirable. An application server such as the disaster message board server can know that users are alive simply from their actions of trying to confirm their family or friends' safety.
+
+It is recommended that the disaster message board system support automatic registration of users' conditions based on the users' interaction with the system and service. The actions that trigger automatic registration include retrieval of other user's messages. In this case, self-safety information is automatically sent to the server with the search query of the retrieval. This is based on the idea that receiving a search query from a user's device means that the owner of the device is alive.
+
+This function can apply to other disaster relief systems such as IP voice-based services.
+
+# 8 Requirements for a disaster voice message delivery service
+
+A disaster voice message delivery service is required to meet the functions in clauses 8.1 to 8.6.
+
+As a general requirement, the need for international interoperability and interworking of national systems should be addressed.
+
+### 8.1 Registration function
+
+Users who wish to deliver their voice message to other users are required to input the number of the user to be called into their terminal, followed by the message they wish to deliver.
+
+#### 1) Called number:
+
+According to the user's request, the system is required to deliver a voice message to a single terminal. In addition, it is recommended that the system handle multiple terminals. So, the systems are required:
+
+- 1.1) To register a single called number into a calling terminal (required)
+- 1.2) To register multiple called numbers into a calling terminal (recommended).
+
+#### 2) Recording message:
+
+The voice message is recorded and packetized at a calling terminal (required).
+
+### 3) Terminal for registration:
+
+The message is registered at a mobile phone terminal with a telephone number (with the number format according to [ITU-T E.164]).
+
+#### 4) Identification of the user:
+
+The mobile phone user normally carries his/her terminal. The voice message from the terminal can be identified as one registered by the user. The message is used for safety confirmation or recognition of damage situation of the user.
+
+### 8.2 Upload function (required)
+
+The registered message is sent and uploaded to a calling server to which the user subscribes. The service is required to accept and store user-generated messages, which should be later delivered to other users.
+
+### **8.3 Confirmation of registration at a calling server (required)**
+
+A confirmation message is sent to a calling terminal after a message is stored at the calling server.
+
+### **8.4 Interoperator usage function (recommended)**
+
+The service is required to allow users other than the message-generating user to receive the message. This condition should be satisfied even if the message-generating user and other users subscribe to different network operators.
+
+### **8.5 Notification of received voice at a called server (required)**
+
+The message is transferred from a calling server to a called server to which the message receiving user subscribes. After the message is accepted and stored at the called server, a notification message is sent to the called terminal.
+
+## **8.6 Receiving and reproducing a voice message**
+
+The service allows receiving users to hear the notification message as voice at their terminals.
+
+#### **1) Receiving (required)**
+
+A packetized voice message is received at a called terminal.
+
+### **2) Reproducing (required)**
+
+The received packetized voice message is reproduced at a called terminal.
+
+#### **3) Type of called terminal:**
+
+Smartphones (interoperable with the calling terminal) (required).
+
+## Bibliography
+
+- [b-UNISDR, 2009] United Nations International Strategy for Disaster Reduction, UNISDR (2009), *2009 UNISDR Terminology on disaster risk reduction*.  
+<<http://www.unisdr.org/we/inform/publications/7817>>
+
+
+
+
+
+## SERIES OF ITU-T RECOMMENDATIONS
+
+|                 |                                                                                                                                                           |
+|-----------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Series A        | Organization of the work of ITU-T                                                                                                                         |
+| Series D        | General tariff principles                                                                                                                                 |
+| <b>Series E</b> | <b>Overall network operation, telephone service, service operation and human factors</b>                                                                  |
+| Series F        | Non-telephone telecommunication services                                                                                                                  |
+| Series G        | Transmission systems and media, digital systems and networks                                                                                              |
+| Series H        | Audiovisual and multimedia systems                                                                                                                        |
+| Series I        | Integrated services digital network                                                                                                                       |
+| Series J        | Cable networks and transmission of television, sound programme and other multimedia signals                                                               |
+| Series K        | Protection against interference                                                                                                                           |
+| Series L        | Environment and ICTs, climate change, e-waste, energy efficiency; construction, installation and protection of cables and other elements of outside plant |
+| Series M        | Telecommunication management, including TMN and network maintenance                                                                                       |
+| Series N        | Maintenance: international sound programme and television transmission circuits                                                                           |
+| Series O        | Specifications of measuring equipment                                                                                                                     |
+| Series P        | Terminals and subjective and objective assessment methods                                                                                                 |
+| Series Q        | Switching and signalling                                                                                                                                  |
+| Series R        | Telegraph transmission                                                                                                                                    |
+| Series S        | Telegraph services terminal equipment                                                                                                                     |
+| Series T        | Terminals for telematic services                                                                                                                          |
+| Series U        | Telegraph switching                                                                                                                                       |
+| Series V        | Data communication over the telephone network                                                                                                             |
+| Series X        | Data networks, open system communications and security                                                                                                    |
+| Series Y        | Global information infrastructure, Internet protocol aspects and next-generation networks, Internet of Things and smart cities                            |
+| Series Z        | Languages and general software aspects for telecommunication systems                                                                                      |

marked/E/T-REC-E.116-199705-I_PDF-E/raw.md

@@ -0,0 +1,567 @@
+
+
+![ITU logo: A globe with a lightning bolt and the letters ITU.](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg)
+
+ITU logo: A globe with a lightning bolt and the letters ITU.
+
+INTERNATIONAL TELECOMMUNICATION UNION
+
+**ITU-T**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+**E.116**
+
+(05/97)
+
+SERIES E: OVERALL NETWORK OPERATION,  
+TELEPHONE SERVICE, SERVICE OPERATION AND  
+HUMAN FACTORS
+
+Operation, numbering, routing and mobile services –  
+International operation – General provisions concerning  
+Administrations
+
+---
+
+**International telecommunication charge card  
+service**
+
+ITU-T Recommendation E.116
+
+(Previously CCITT Recommendation)
+
+---
+
+# ITU-T E-SERIES RECOMMENDATIONS
+
+## OVERALL NETWORK OPERATION, TELEPHONE SERVICE, SERVICE OPERATION AND HUMAN FACTORS
+
+|                                                                                                   |                    |
+|---------------------------------------------------------------------------------------------------|--------------------|
+| <b><i>OPERATION, NUMBERING, ROUTING AND MOBILE SERVICES</i></b>                                   |                    |
+| INTERNATIONAL OPERATION                                                                           | E.100–E.229        |
+| Definitions                                                                                       | E.100–E.103        |
+| <b>General provisions concerning Administrations</b>                                              | <b>E.104–E.119</b> |
+| General provisions concerning users                                                               | E.120–E.139        |
+| Operation of international telephone services                                                     | E.140–E.159        |
+| Numbering plan of the international telephone service                                             | E.160–E.169        |
+| International routing plan                                                                        | E.170–E.179        |
+| Tones in national signalling systems                                                              | E.180–E.199        |
+| Maritime mobile service and public land mobile service                                            | E.200–E.229        |
+| OPERATIONAL PROVISIONS RELATING TO CHARGING AND ACCOUNTING IN THE INTERNATIONAL TELEPHONE SERVICE | E.230–E.299        |
+| Charging in the international telephone service                                                   | E.230–E.249        |
+| Procedures for remuneration of Administrations for facilities made available                      | E.250–E.259        |
+| Measuring and recording call durations for accounting purposes                                    | E.260–E.269        |
+| Establishment and exchange of international accounts                                              | E.270–E.299        |
+| UTILIZATION OF THE INTERNATIONAL TELEPHONE NETWORK FOR NON-TELEPHONY APPLICATIONS                 | E.300–E.329        |
+| General                                                                                           | E.300–E.319        |
+| Phototelegraphy                                                                                   | E.320–E.329        |
+| ISDN PROVISIONS CONCERNING USERS                                                                  | E.330–E.399        |
+| <b><i>QUALITY OF SERVICE, NETWORK MANAGEMENT AND TRAFFIC ENGINEERING</i></b>                      |                    |
+| NETWORK MANAGEMENT                                                                                | E.400–E.489        |
+| TRAFFIC ENGINEERING                                                                               | E.490–E.799        |
+| QUALITY OF TELECOMMUNICATION SERVICES: CONCEPTS, MODELS, OBJECTIVES AND DEPENDABILITY PLANNING    | E.800–E.899        |
+
+For further details, please refer to ITU-T List of Recommendations.
+
+## **ITU-T RECOMMENDATION E.116**
+
+# **INTERNATIONAL TELECOMMUNICATION CHARGE CARD SERVICE**
+
+## **Summary**
+
+The international telecommunication charge card service, and particularly its automated use throughout the world, will provide benefits to both users and Recognized Operating Agencies (ROAs). This is based on a recognition of:
+
+- 1) the ROAs' need for security against fraudulent use, simplified billing procedures and a reduction in the requirement for operator assistance when telephone calls are made other than on a direct payment basis;
+- 2) the current and anticipated charge card technology which could provide increased security and enhanced service to users;
+- 3) the growing requirement for charge cards to pay for a variety of telecommunications services.
+
+As a result, ROAs (with appropriate authorization and coordination of their Administrations) are encouraged to prepare for, and introduce, the international telecommunication charge card service using the guidance of this Recommendation.
+
+### **Source**
+
+ITU-T Recommendation E.116 was revised by ITU-T Study Group 2 (1997-2000) and was approved under the WTSC Resolution No. 1 procedure on the 26th of May 1997.
+
+## FOREWORD
+
+ITU (International Telecommunication Union) is the United Nations Specialized Agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the ITU. The ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis.
+
+The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics.
+
+The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Resolution No. 1.
+
+In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC.
+
+### NOTE
+
+In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+### INTELLECTUAL PROPERTY RIGHTS
+
+The ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. The ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process.
+
+As of the date of approval of this Recommendation, the ITU had/had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database.
+
+© ITU 1997
+
+All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU.
+
+## CONTENTS
+
+|                                                                                | <i>Page</i> |
+|--------------------------------------------------------------------------------|-------------|
+| 1 Preamble.....                                                                | 1           |
+| 1.1 References .....                                                           | 1           |
+| 2 Service definition and general description .....                             | 1           |
+| 2.1 Service definition.....                                                    | 1           |
+| 2.2 General description.....                                                   | 1           |
+| 3 Definitions.....                                                             | 2           |
+| 4 Service agreements between the Card Acceptor and Card Issuer .....           | 2           |
+| 5 Types of cards which may be used.....                                        | 2           |
+| 6 Operational procedures for the use of cards .....                            | 3           |
+| 6.1 Customer access procedures for use of the card .....                       | 3           |
+| 6.2 System functions.....                                                      | 4           |
+| 7 Operational procedures for charging, accounting and billing .....            | 5           |
+| 7.1 Charging and accounting .....                                              | 5           |
+| 7.2 Assessment of charges .....                                                | 5           |
+| 7.3 Billing information .....                                                  | 5           |
+| Annex A – Alphabetical list of abbreviations used in this Recommendation ..... | 5           |
+| Annex B – Procedure flow diagrams.....                                         | 6           |
+
+
+
+# **INTERNATIONAL TELECOMMUNICATION CHARGE CARD SERVICE**
+
+*(revised 1997)*
+
+## **1 Preamble**
+
+The international telecommunication charge card service, and particularly its automated use throughout the world, will provide benefits to both users and Recognized Operating Agencies (ROAs). This is based on a recognition of:
+
+- 1) the ROAs' need for security against fraudulent use, simplified billing procedures and a reduction in the requirement for operator assistance when telephone calls are made other than on a direct payment basis;
+- 2) the current and anticipated charge card technology which could provide increased security and enhanced service to users;
+- 3) the growing requirement for charge cards to pay for a variety of telecommunications services.
+
+As a result, ROAs (with appropriate authorization and coordination of their Administrations) are encouraged to prepare for, and introduce, the international telecommunication charge card service using the guidance of this Recommendation.
+
+### **1.1 References**
+
+The following ITU-T Recommendations, and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; all users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published.
+
+- [1] ITU-T Recommendation E.118 (1996), *The international telecommunication charge card*.
+- [2] ITU-T Recommendation E.113 (1997), *Validation procedures for the international telecommunications charge card service*.
+- [3] ISO/IEC 7813:1995, *Identification cards – Financial transaction cards*.
+
+## **2 Service definition and general description**
+
+### **2.1 Service definition**
+
+The **international telecommunication charge card** service allows a holder of a telecommunication charge card<sup>1</sup> to make use of a variety of telecommunication services provided by the card acceptor and have charges billed to the customer's account by the Card Issuer.
+
+### **2.2 General description**
+
+- a) The scope of services<sup>2</sup> for which the card applies will be subject to agreements between the Card Issuer and Card Acceptor.
+- b) The service may use either full or limited validation of the card.
+
+---
+
+<sup>1</sup> This Recommendation specifically entails the use of a telecommunication charge card (89 cards) issued by an ROA in compliance with Recommendation E.118 [1]. The acceptance of cards issued by banks or other companies is a national matter and not included in this Recommendation, although it is recognized that these cards could be accepted in a similar manner.
+
+<sup>2</sup> It is not the intention of this Recommendation to limit the charge card service to the telephone service.
+
+- c) Subject to agreement between Card Acceptor and Card Issuer, the service may enable the card holder (user) to communicate:
+  - back to the country of the Card Issuer;
+  - within the country of the Card Acceptor;
+  - between the country of the Card Acceptor and a third country.Use of the card within the country of issue is a national matter.
+- d) International telecommunication charge cards will conform to the relevant ITU-T (formerly CCITT) Recommendations.
+- e) The use of pre-paid or debit cards is not covered by this Recommendation.
+
+## 3 Definitions
+
+This Recommendation defines the following terms.
+
+**3.1 card issuer:** The ROA that issues the card. The Card Issuer is responsible for the collection of charges from the card holder and for making the appropriate payments for the service concerned to the Card Acceptor.
+
+**3.2 card acceptor:** The ROA that accepts the use of the card as payment for the provision of certain telecommunication services.
+
+**3.3 full validation:** A procedure by which the card information is checked in a comprehensive way either against a complete database containing all valid cards for a particular Card Issuer or using the processing capability available on some types of cards in their dialogue with the system or in the system itself.
+
+**3.4 limited validation:** One or more procedures to gain some assurance of the validity of the card. These procedures may include, but are not limited to, checks against a list of unacceptable cards and use of additional checking procedures which are based on the card number.
+
+**3.5 unbillable calls:** Calls for which insufficient or incorrect billing information is conveyed to the Card Issuer such that the billing information cannot be associated with any particular customer account.
+
+**3.6 uncollectable calls:** Calls for which billing is made to a particular customer account, but, for any of a variety of potential reasons, collection of the charge was not possible.
+
+## 4 Service agreements between the Card Acceptor and Card Issuer
+
+The international telecommunication charge card service depends on agreements between Card Acceptors and Card Issuers. Major items to be covered may include:
+
+- a) basis for settlement of service charges and surcharges;
+- b) exchange of billing and other information;
+- c) responsibility for fraudulent use of cards, and for uncollectable and unbillable calls;
+- d) validation procedures and any potential associated costs;
+- e) types of services for which cards may be used;
+- f) use of information contained in the discretionary data field, and default values used in the absence of specifically coded information on track 2;
+- g) use of data on tracks 1 and 3.
+
+## 5 Types of cards which may be used
+
+The types of cards which may be used are: the Integrated Circuit (IC) card (a card containing a microprocessor and memory in an IC chip), cards using the magnetic stripe technology and printed cards. (The cards are described/defined in Recommendation E.118 [1].)
+
+## 6 Operational procedures for the use of cards
+
+To derive the maximum benefit from the charge card, the card holder should not be required to show the card and should be able to invoke the service by simply providing the card information to the operator or associate system. The number on the card along with any additional validation checks should provide sufficient guarantee of the card's validity.
+
+### 6.1 Customer access procedures for use of the card
+
+The following subclauses describe the basic customer access procedures involved in using the charge card service. In addition, optional functions that may be invoked by the user are defined. Flow diagrams are provided in Annex B. These are guidelines and do not attempt to define the details required for service implementation.
+
+#### 6.1.1 Service invocation
+
+The customer will invoke the service by first lifting the handset (or taking an action equivalent to going off hook). The following sequence of information is then provided by the customer. The manner of entry may be by key-pad, voice, card reader or a combination of these methods:
+
+- service access number;
+- destination number (a);
+- Primary Account Number (PAN);
+- PIN;
+- destination number (b).
+
+NOTE 1 – If the service access number is dedicated to a specific Card Issuer, then the destination number may be placed by the customer in either location (a) or (b) in the sequence.
+
+NOTE 2 – If the service access number is shared by multiple Card Issuers, then the destination number may only be entered in position (b) and the first information entered by the customer after the service access number is the PAN.
+
+NOTE 3 – Prompts will be provided by the service as required; however, they may be optionally overridden (by keying ahead) by the customer.
+
+#### 6.1.2 Presentation of the card or the card information
+
+One or more possibilities are envisaged concerning the relevant information to the service provider, depending on the type of terminal available to the customer. These include but are not limited to:
+
+- automatically, via a card reader;
+- manually, via a key-pad;
+- orally, through an operator or a voice recognition system.
+
+Customers may be prompted, depending on the capabilities of the service provider (terminal or network), for information visually and orally.
+
+#### 6.1.3 Request for service
+
+The customer enters the desired destination number and/or other information to enable the system to provide the desired service.
+
+#### 6.1.4 Optional functions available to the customer, depending on the capabilities of the service provider or as defined by the service agreement between the Card Issuer and service provider
+
+- a) Operator fallback – The customer should be able to obtain operator assistance either by specific request or by timeout during an expected input action. Operator fallback may also be possible in the case of a customer making an input error.
+- b) In-language instructions – The customer should be able to request that instructions and prompts be given in a specified language. To be useful, the selection of language should be made available as early in the process as possible (e.g. after lifting the handset); actual placement may depend on the capabilities of the terminal used.
+- c) Help instructions – The customer should be able to request additional information to augment the instruction or prompt being given, most likely in the specific language requested.
+
+- d) Termination of input string – The customer should be able to press a key (or sequence of keys) to identify the end of an input string.
+- e) Error correction – The customer should be able to press a key (or sequence of keys) to restart an input sequence when an error is self-detected by the customer during the input process.
+- f) Customer service request – The customer should, when encountering trouble in using the card service, be able to contact, through the local operator of the Card Acceptor:
+  - the customer service organization of the Card Acceptor to obtain, for example, help with local dialling instructions or directory assistance;
+  - the customer service organization of the Card Issuer to obtain, for example, help for problems with lost/stolen cards, restricted usage, credit limits, or where the card is not honoured.
+
+The customer may also be able to directly contact the customer service organization of the Card Issuer by dialling a customer service number (normally without charge to the customer) that has been provided to the customer by the Card Issuer.
+
+- g) Follow-on call – The customer should be able to press a key (or sequence of keys) to enable a subsequent call to be made using the same charge card information.
+- h) Acceptance of other information – The system should be able to accept other discretionary information supplied by the user or contained on the card including, for example, other service or personal identification information.
+
+### 6.2 System functions
+
+The system providing the international telecommunication charge card service may be composed of several elements, including telecommunication terminals (e.g. card reading pay phones), operator systems, databases, signalling facilities, etc. However, configured to provide the necessary service functions to the customer, the following major systems functions should be enabled:
+
+#### 6.2.1 Card acceptance and reading
+
+Depending on the type of terminal available to the customer, the system may be able to accept, read, and if required, write information on one or more types of cards (magnetic stripe, IC, etc.) intended for use with the service. For systems to interface with magnetic stripe cards, they may be able to read and process any information encoded on track 2 of the magnetic stripe as defined by ISO/IEC 7813 [3]. Recommendation E.118 [1] contains further clarification on how this information should be interpreted for telecommunication charge cards.
+
+#### 6.2.2 Card validation
+
+The system should be able to determine whether a card or billing number is valid. Validation should take place for each call (or follow-on call, if provided) being attempted. These procedures should comply with Recommendation E.113 [2].
+
+#### 6.2.3 Information transfer
+
+The system should be able to accept user information for immediate use or later transfer to other system components.
+
+#### 6.2.4 Call records
+
+The system should be able to record accurate and complete call data (including validation indication) required for billing, accounting and administrative purposes.
+
+#### 6.2.5 User feedback
+
+The system should be able to provide guidance and error feedback to the user to make the system easy and convenient to use.
+
+#### 6.2.6 Information security
+
+The operation of the system should ensure that all reasonable precautions are taken to protect user information from disclosure to unauthorized parties.
+
+## **7 Operational procedures for charging, accounting and billing**
+
+### **7.1 Charging and accounting**
+
+Charging and accounting principles are contained in the appropriate D-Series Recommendations.
+
+### **7.2 Assessment of charges**
+
+The assessment of charges will be that applicable to the telecommunication service being used together with any service charges and/or surcharges that might be applicable to the international telecommunication charge card service.
+
+### **7.3 Billing information**
+
+Billing information will provide sufficient data to identify the customer (i.e. the primary account number<sup>3</sup>) and charges to be levied. In the case of telephone service it may include the following:
+
+- a) chargeable duration, chargeable number of units and/or charges as appropriate;
+- b) calling and called number, including country codes where appropriate;
+- c) time of day (hour and minutes) and date (day, month, year); and
+- d) other information as agreed between the ROAs concerned.
+
+Billing information required for other services is a matter for further study.
+
+## **Annex A**
+
+### **Alphabetical list of abbreviations used in this Recommendation**
+
+|     |                                |
+|-----|--------------------------------|
+| IC  | Integrated Circuit             |
+| PAN | Primary Account Number         |
+| PIN | Personal Identification Number |
+
+---
+
+<sup>3</sup> The Personal Identification Number (PIN) (or secret code) should not be provided to, nor should it appear in, the billing information.
+
+## Annex B
+
+### Procedure flow diagrams
+
+![Flowchart of Customer access procedures](042733dc5e8e7f5f30b60adba3266cde_img.jpg)
+
+```
+graph TD; START([START (1)]) --> LIFT[LIFT HANDSET (2)]; LIFT -- "(Note 1)" --> PROMPT[CUSTOMER PROMPTED TO DIAL ACCESS NO. OR USE CRD RDR (3)]; PROMPT -- "(Note 2)" --> DIALLED{AUTO ACCESS NO. DIALLED? (5)}; DIALLED -- Yes --> AUTO[AUTO ACCESS PROCEDURE (10)]; DIALLED -- No --> OPER{OPER. ACCESS NO. DIALLED? (6)}; OPER -- Yes --> OPER_PROC[OPERATOR ACCESS PROCEDURE (11)]; OPER -- No --> USED{CARD READER USED? (4)}; USED -- Yes --> CARD[CARD READER PROCEDURE (9)]; USED -- No --> TIMEOUT{TIMEOUT? (7)}; TIMEOUT -- Yes --> DISCONNECT[DISCONNECT LINE (8)]; TIMEOUT -- No --> DIALLED; AUTO --> END([END (12)]); OPER_PROC --> END; CARD --> END; DISCONNECT --> END;
+```
+
+The flowchart illustrates the customer access procedures. It begins with 'START (1)' leading to 'LIFT HANDSET (2)'. A note indicates this is equivalent to going offhook. The next step is 'CUSTOMER PROMPTED TO DIAL ACCESS NO. OR USE CRD RDR (3)'. A note indicates the prompt may include dial tone or visual/oral message. The flow then enters a decision loop: 'AUTO ACCESS NO. DIALLED? (5)'. If 'Yes', it proceeds to 'AUTO ACCESS PROCEDURE (10)'. If 'No', it proceeds to 'OPER. ACCESS NO. DIALLED? (6)'. If 'Yes', it proceeds to 'OPERATOR ACCESS PROCEDURE (11)'. If 'No', it proceeds to 'CARD READER USED? (4)'. If 'Yes', it proceeds to 'CARD READER PROCEDURE (9)'. If 'No', it proceeds to 'TIMEOUT? (7)'. If 'Yes', it proceeds to 'DISCONNECT LINE (8)'. If 'No', it loops back to 'AUTO ACCESS NO. DIALLED? (5)'. All procedure boxes (10, 11, 9) and the 'DISCONNECT LINE (8)' box lead to 'END (12)'.
+
+Flowchart of Customer access procedures
+
+T0105540-96/d01
+
+NOTE 1 – This is equivalent of going offhook.
+
+NOTE 2 – Prompt may include dial tone or visual/oral message.
+
+Figure B.1/E.116 – Customer access procedures
+
+![Flowchart of Card reader procedure (9). The process starts with START (9), followed by READ MAG STRIPE (13). A decision 'IS CARD 89? (13.5)' follows. If 'No', it goes to 'NON 89 CARD PROCEDURE (3)' which leads to connector C. If 'Yes', it goes to 'CARD DATA DEPENDENT ON ROA'S IMPLEMENTATION (14)'. From there, it goes to 'PROMPT FOR PIN (15)' (Note 4), then 'INPUT PIN (16)' (Note 1). A decision 'SUBSEQ. IDENT. ATTEMPT? (17)' follows. If 'No', it goes to 'CALLED NUMBER PROCEDURE (18)' (Note 6), then 'VALIDATION PROCEDURE Rec. E.113 (19)' (Note 5), which loops back to 'SUBSEQ. IDENT. ATTEMPT? (17)'. If 'Yes', it goes to 'IS CARD VALID? (20)'. If 'No', it goes to 'IDENT. ATTEMPTS EXCEEDED? (25)'. If 'Yes', it goes to connector B. If 'No', it goes to 'INCREMENT IDENTIFICATION ATTEMPTS COUNTER (26)', then 'PROMPT TO RE-ENTER CARD NUMBER (27)', which loops back to 'SUBSEQ. IDENT. ATTEMPT? (17)'. If 'Yes' to 'IS CARD VALID? (20)', it goes to 'MAKE CALL PROCEDURE (21)'. From 'MAKE CALL PROCEDURE (21)', it goes to 'FOLLOW ON CALLS ALLOWED? (22)'. If 'No', it goes to connector C. If 'Yes', it goes to 'FOLLOW ON CALLS REQUESTED? (22.1)'. If 'No', it goes to connector C. If 'Yes', it loops back to 'SUBSEQ. IDENT. ATTEMPT? (17)'. A connector B leads to 'OPERATOR FALLBACK AVAIL? (28)'. If 'Yes', it goes to 'MESSAGE (29)'. If 'No', it goes to 'OPERATOR ACCESS PROCEDURE (11)'. Both 'MESSAGE (29)' (Note 2) and 'OPERATOR ACCESS PROCEDURE (11)' lead to 'DISCONNECT (24)'. 'DISCONNECT (24)' leads to 'END (31)'. A connector C leads to 'MESSAGE: e.g. Thank you for using.. please replace handset (23)', which also leads to 'DISCONNECT (24)'.](af7916c89a458fdab6c3f443217388ae_img.jpg)
+
+```
+
+graph TD
+    START([START (9)]) --> READ[READ MAG STRIPE (13)]
+    READ --> IS89{IS CARD 89? (13.5)}
+    IS89 -- No --> NON89[NON 89 CARD PROCEDURE (3)]
+    NON89 --> C1((C))
+    IS89 -- Yes --> CARDATA[CARD DATA DEPENDENT ON ROA'S IMPLEMENTATION (14)]
+    CARDATA --> PROMPTPIN[PROMPT FOR PIN (15)]
+    PROMPTPIN -- (Note 4) --> INPUTPIN[INPUT PIN (16)]
+    INPUTPIN -- (Note 1) --> SUBSEQ{SUBSEQ. IDENT. ATTEMPT? (17)}
+    SUBSEQ -- No --> CALLED[CALLED NUMBER PROCEDURE (18)]
+    CALLED -- (Note 6) --> VALIDATION[VALIDATION PROCEDURE Rec. E.113 (19)]
+    VALIDATION -- (Note 5) --> SUBSEQ
+    SUBSEQ -- Yes --> ISVALID{IS CARD VALID? (20)}
+    ISVALID -- No --> IDENTEXCEEDED{IDENT. ATTEMPTS EXCEEDED? (25)}
+    IDENTEXCEEDED -- Yes --> B1((B))
+    IDENTEXCEEDED -- No --> INCREMENT[INCREMENT IDENTIFICATION ATTEMPTS COUNTER (26)]
+    INCREMENT --> PROMPTREENTER[PROMPT TO RE-ENTER CARD NUMBER (27)]
+    PROMPTREENTER --> SUBSEQ
+    ISVALID -- Yes --> MAKECALL[MAKE CALL PROCEDURE (21)]
+    MAKECALL --> FOLLOWALLOWED{FOLLOW ON CALLS ALLOWED? (22)}
+    FOLLOWALLOWED -- No --> C2((C))
+    FOLLOWALLOWED -- Yes --> FOLLOWREQUESTED{FOLLOW ON CALLS REQUESTED? (22.1)}
+    FOLLOWREQUESTED -- No --> C3((C))
+    FOLLOWREQUESTED -- Yes --> SUBSEQ
+    B1 --> OPERATORFALLBACK{OPERATOR FALLBACK AVAIL? (28)}
+    OPERATORFALLBACK -- Yes --> MESSAGE29[MESSAGE (29)]
+    OPERATORFALLBACK -- No --> OPERATORACCESS[OPERATOR ACCESS PROCEDURE (11)]
+    MESSAGE29 -- (Note 2) --> DISCONNECT[DISCONNECT (24)]
+    OPERATORACCESS --> DISCONNECT
+    DISCONNECT --> END([END (31)])
+    C2 --> MESSAGE23[MESSAGE: e.g. Thank you for using.. please replace handset (23)]
+    MESSAGE23 --> DISCONNECT
+  
+```
+
+Flowchart of Card reader procedure (9). The process starts with START (9), followed by READ MAG STRIPE (13). A decision 'IS CARD 89? (13.5)' follows. If 'No', it goes to 'NON 89 CARD PROCEDURE (3)' which leads to connector C. If 'Yes', it goes to 'CARD DATA DEPENDENT ON ROA'S IMPLEMENTATION (14)'. From there, it goes to 'PROMPT FOR PIN (15)' (Note 4), then 'INPUT PIN (16)' (Note 1). A decision 'SUBSEQ. IDENT. ATTEMPT? (17)' follows. If 'No', it goes to 'CALLED NUMBER PROCEDURE (18)' (Note 6), then 'VALIDATION PROCEDURE Rec. E.113 (19)' (Note 5), which loops back to 'SUBSEQ. IDENT. ATTEMPT? (17)'. If 'Yes', it goes to 'IS CARD VALID? (20)'. If 'No', it goes to 'IDENT. ATTEMPTS EXCEEDED? (25)'. If 'Yes', it goes to connector B. If 'No', it goes to 'INCREMENT IDENTIFICATION ATTEMPTS COUNTER (26)', then 'PROMPT TO RE-ENTER CARD NUMBER (27)', which loops back to 'SUBSEQ. IDENT. ATTEMPT? (17)'. If 'Yes' to 'IS CARD VALID? (20)', it goes to 'MAKE CALL PROCEDURE (21)'. From 'MAKE CALL PROCEDURE (21)', it goes to 'FOLLOW ON CALLS ALLOWED? (22)'. If 'No', it goes to connector C. If 'Yes', it goes to 'FOLLOW ON CALLS REQUESTED? (22.1)'. If 'No', it goes to connector C. If 'Yes', it loops back to 'SUBSEQ. IDENT. ATTEMPT? (17)'. A connector B leads to 'OPERATOR FALLBACK AVAIL? (28)'. If 'Yes', it goes to 'MESSAGE (29)'. If 'No', it goes to 'OPERATOR ACCESS PROCEDURE (11)'. Both 'MESSAGE (29)' (Note 2) and 'OPERATOR ACCESS PROCEDURE (11)' lead to 'DISCONNECT (24)'. 'DISCONNECT (24)' leads to 'END (31)'. A connector C leads to 'MESSAGE: e.g. Thank you for using.. please replace handset (23)', which also leads to 'DISCONNECT (24)'.
+
+T0105550-96/d02
+
+NOTE 1 – Indication of PIN entry should be shown (e.g. as \*\*\* for each digit keyed), but does not display actual PIN number.
+
+NOTE 2 – Message given to user may depend on type of error (e.g. if card is invalid "Please contact your charge card issuer").
+
+NOTE 3 – Use of non 89 cards is outside the scope of this Recommendation. It is envisaged that the procedure for such cards would be similar to those of 89 cards.
+
+NOTE 4 – Card reader procedure may prompt for retries.
+
+NOTE 5 – Number of PIN retries procedure will be dependent on the individual ROA's implementation.
+
+NOTE 6 – The manner of implementation will indicate the sequence of "validation" and "called number" procedures.
+
+**Figure B.2/E.116 – Card reader procedure (9)**
+
+![Flowchart of the Auto access procedure (10). The process starts at START (10), prompts for PAN (32), and inputs PAN (33). It then checks if the card is an '89' card (34). If not, it follows the NON 89 CARD PROCEDURE (C). If it is, it checks if PIN input with PAN is successful (35). If not, it prompts for PIN (36), inputs PIN (37), and checks if the subsequent identification attempt is successful (38). If successful, it follows the CALLED NUMBER PROCEDURE (14) to connector B. If not, it follows connector A. If PIN input is successful (35), it checks if a follow-on call is requested. If not, it follows connector C. If yes, it checks if follow-on calls are allowed (39). If not, it sends a message (41) and disconnects (42). If yes, it makes a call (21) and checks if the card is valid (38). If invalid, it checks if identification attempts have exceeded (43). If yes, it prompts to re-enter PAN (45) and follows connector A. If no, it increments the identification attempts counter (44) and follows connector B. If the card is valid (38), it makes a call (21) and checks if follow-on calls are allowed (39). If not, it sends a message (41) and disconnects (42). If yes, it checks if a follow-on call is requested. If not, it follows connector C. If yes, it checks if follow-on calls are allowed (39). If not, it sends a message (41) and disconnects (42). If yes, it checks if operator fallback is available (46). If not, it sends a message (47) and disconnects (42). If yes, it follows the OPERATOR ACCESS PROCEDURE (11) to END (48).](4801720824e4b5e2361a5564f91cfb70_img.jpg)
+
+```
+
+graph TD
+    START([START (10)]) --> PROMPT_PAN[PROMPT FOR PAN (32)]
+    PROMPT_PAN --> INPUT_PAN[INPUT PAN (33)]
+    INPUT_PAN --> IS_CARD_89{IS CARD '89? (34)}
+    IS_CARD_89 -- No --> NON_89_CARD[NON 89 CARD PROCEDURE]
+    NON_89_CARD --> C((C))
+    IS_CARD_89 -- Yes --> PIN_INPUT{PIN INPUT WITH PAN? (35)}
+    PIN_INPUT -- No --> PROMPT_PIN[PROMPT FOR PIN (36)]
+    PROMPT_PIN --> INPUT_PIN[INPUT PIN (37)]
+    INPUT_PIN --> SUBSEQ_IDENT{SUBSEQ. IDENT. ATTEMPT? (38)}
+    SUBSEQ_IDENT -- Yes --> B((B))
+    SUBSEQ_IDENT -- No --> CALLED_NUMBER[CALLED NUMBER PROCEDURE (14)]
+    CALLED_NUMBER --> B
+    PIN_INPUT -- Yes --> FOLLOW_CALL_REQUESTED{FOLLOW ON CALL REQUESTED?}
+    FOLLOW_CALL_REQUESTED -- No --> C
+    FOLLOW_CALL_REQUESTED -- Yes --> FOLLOW_CALLS_ALLOWED{FOLLOW ON CALLS ALLOWED? (39)}
+    FOLLOW_CALLS_ALLOWED -- No --> MESSAGE_41[MESSAGE "Thank you for using ... please replace handset" (41)]
+    MESSAGE_41 --> DISCONNECT[DISCONNECT (42)]
+    FOLLOW_CALLS_ALLOWED -- Yes --> MAKE_CALL[MAKE CALL (21)]
+    MAKE_CALL --> IS_CARD_VALID{IS CARD VALID? (38)}
+    IS_CARD_VALID -- No --> IDENT_ATTEMPTS{IDENT. ATTEMPTS EXCEEDED? (43)}
+    IDENT_ATTEMPTS -- Yes --> PROMPT_REENTER[PROMPT TO RE-ENTER PAN (45)]
+    PROMPT_REENTER --> A((A))
+    IDENT_ATTEMPTS -- No --> INCREMENT_COUNTER[INCREMENT IDENTIFICATION ATTEMPTS COUNTER (44)]
+    INCREMENT_COUNTER --> B
+    IS_CARD_VALID -- Yes --> MAKE_CALL
+    MESSAGE_41 --> DISCONNECT
+    DISCONNECT --> END([END (48)])
+    MESSAGE_41 --> MESSAGE_47[MESSAGE: (Note) (47)]
+    MESSAGE_47 --> OPERATOR_FALLBACK{OPERATOR FALLBACK AVAIL? (46)}
+    OPERATOR_FALLBACK -- No --> MESSAGE_47
+    OPERATOR_FALLBACK -- Yes --> OPERATOR_ACCESS[OPERATOR ACCESS PROCEDURE (11)]
+    OPERATOR_ACCESS --> END
+  
+```
+
+Flowchart of the Auto access procedure (10). The process starts at START (10), prompts for PAN (32), and inputs PAN (33). It then checks if the card is an '89' card (34). If not, it follows the NON 89 CARD PROCEDURE (C). If it is, it checks if PIN input with PAN is successful (35). If not, it prompts for PIN (36), inputs PIN (37), and checks if the subsequent identification attempt is successful (38). If successful, it follows the CALLED NUMBER PROCEDURE (14) to connector B. If not, it follows connector A. If PIN input is successful (35), it checks if a follow-on call is requested. If not, it follows connector C. If yes, it checks if follow-on calls are allowed (39). If not, it sends a message (41) and disconnects (42). If yes, it makes a call (21) and checks if the card is valid (38). If invalid, it checks if identification attempts have exceeded (43). If yes, it prompts to re-enter PAN (45) and follows connector A. If no, it increments the identification attempts counter (44) and follows connector B. If the card is valid (38), it makes a call (21) and checks if follow-on calls are allowed (39). If not, it sends a message (41) and disconnects (42). If yes, it checks if a follow-on call is requested. If not, it follows connector C. If yes, it checks if follow-on calls are allowed (39). If not, it sends a message (41) and disconnects (42). If yes, it checks if operator fallback is available (46). If not, it sends a message (47) and disconnects (42). If yes, it follows the OPERATOR ACCESS PROCEDURE (11) to END (48).
+
+NOTE – Message given to user may depend on type of error (e.g. if card is invalid "Please contact your charge card issuer").
+
+Figure B.3/E.116 – Auto access procedure (10)
+
+![Flowchart of Operator access procedure (11). The process starts with START (11), followed by OPERATOR REQUESTS PAN (49), CUSTOMER PROVIDES PAN (50), and a decision IS CARD 89? (51). If No, it goes to NON 89 PROCEDURE (30) and then to connector A (Note 1). If Yes, it goes to OPERATOR REQUESTS AUTHORIZATION CODE OR PIN (52), CUSTOMER PROVIDES AUTHORIZATION CODE OR PIN (53), OPERATOR KEYS PAN AND AUTHORIZATION CODE OR PIN (54), and CALLED NUMBER PROCEDURE. These lead to VALIDATION PROCEDURE Rec. E.113, then to decision IS CARD VALID? (55). If No, it goes to decision IDENT. ATTEMPTS EXCEEDED? (56). If Yes, it goes to ROA INFORMS CUSTOMER OF FAILURE. If No, it goes to INCREMENT IDENTIFICATION ATTEMPTS COUNTER (57). Both INCREMENT IDENTIFICATION ATTEMPTS COUNTER (57) and ROA INFORMS CUSTOMER OF FAILURE lead to connector A (Note 2). If IS CARD VALID? (55) is Yes, it goes to OPERATOR CONNECTS CALL (58). All three paths (from A, from ROA INFORMS CUSTOMER OF FAILURE, and from OPERATOR CONNECTS CALL (58)) lead to DISCONNECT (59), which ends at END (61).](33ed1f9b27c7c21c797aa928b0f06851_img.jpg)
+
+```
+
+graph TD
+    START([START (11)]) --> OPERATOR_REQUESTS_PAN[OPERATOR REQUESTS PAN (49)]
+    OPERATOR_REQUESTS_PAN --> CUSTOMER_PROVIDES_PAN[CUSTOMER PROVIDES PAN (50)]
+    CUSTOMER_PROVIDES_PAN --> IS_CARD_89{IS CARD 89? (51)}
+    IS_CARD_89 -- No --> NON_89_PROCEDURE[NON 89 PROCEDURE (30)]
+    NON_89_PROCEDURE --> A1((A (Note 1)))
+    IS_CARD_89 -- Yes --> OPERATOR_REQUESTS_AUTH[OPERATOR REQUESTS AUTHORIZATION CODE OR PIN (52)]
+    OPERATOR_REQUESTS_AUTH --> CUSTOMER_PROVIDES_AUTH[CUSTOMER PROVIDES AUTHORIZATION CODE OR PIN (53)]
+    CUSTOMER_PROVIDES_AUTH --> OPERATOR_KEYS[OPERATOR KEYS PAN AND AUTHORIZATION CODE OR PIN (54)]
+    OPERATOR_KEYS --> CALLED_NUMBER[CALLED NUMBER PROCEDURE]
+    CALLED_NUMBER --> VALIDATION[VALIDATION PROCEDURE Rec. E.113]
+    VALIDATION --> IS_CARD_VALID{IS CARD VALID? (55)}
+    IS_CARD_VALID -- No --> IDENT_ATTEMPTS{IDENT. ATTEMPTS EXCEEDED? (56)}
+    IDENT_ATTEMPTS -- Yes --> ROA_INFORMS[ROA INFORMS CUSTOMER OF FAILURE]
+    IDENT_ATTEMPTS -- No --> INCREMENT[INCREMENT IDENTIFICATION ATTEMPTS COUNTER (57)]
+    INCREMENT --> A2((A (Note 2)))
+    ROA_INFORMS --> A2
+    IS_CARD_VALID -- Yes --> OPERATOR_CONNECTS[OPERATOR CONNECTS CALL (58)]
+    OPERATOR_CONNECTS --> A2
+    A2 --> DISCONNECT[DISCONNECT (59)]
+    DISCONNECT --> END([END (61)])
+  
+```
+
+Flowchart of Operator access procedure (11). The process starts with START (11), followed by OPERATOR REQUESTS PAN (49), CUSTOMER PROVIDES PAN (50), and a decision IS CARD 89? (51). If No, it goes to NON 89 PROCEDURE (30) and then to connector A (Note 1). If Yes, it goes to OPERATOR REQUESTS AUTHORIZATION CODE OR PIN (52), CUSTOMER PROVIDES AUTHORIZATION CODE OR PIN (53), OPERATOR KEYS PAN AND AUTHORIZATION CODE OR PIN (54), and CALLED NUMBER PROCEDURE. These lead to VALIDATION PROCEDURE Rec. E.113, then to decision IS CARD VALID? (55). If No, it goes to decision IDENT. ATTEMPTS EXCEEDED? (56). If Yes, it goes to ROA INFORMS CUSTOMER OF FAILURE. If No, it goes to INCREMENT IDENTIFICATION ATTEMPTS COUNTER (57). Both INCREMENT IDENTIFICATION ATTEMPTS COUNTER (57) and ROA INFORMS CUSTOMER OF FAILURE lead to connector A (Note 2). If IS CARD VALID? (55) is Yes, it goes to OPERATOR CONNECTS CALL (58). All three paths (from A, from ROA INFORMS CUSTOMER OF FAILURE, and from OPERATOR CONNECTS CALL (58)) lead to DISCONNECT (59), which ends at END (61).
+
+NOTE 1 – Use of non 89 cards is outside the scope of this Recommendation. It is envisaged that the procedure for such cards would be similar to those of 89 cards.
+
+NOTE 2 – Detailed processes need to be agreed between the relevant ROAs.
+
+**Figure B.4/E.116 – Operator access procedure (11)**
+
+![Flowchart of the Called number procedure (18). The process starts with START (18), followed by PROMPT FOR CALLED NUMBER (62). It then enters a loop: INPUT DIALLED DIGITS (63) -> ALL DIGITS RECEIVED? (64). If 'Yes', it goes to END (99). If 'No', it checks TIMEOUT? (65). If 'No' at (65), it loops back to INPUT DIALLED DIGITS (63). If 'Yes' at (65) (with a Note), it checks OPERATOR FALLBACK AVAIL? (66). If 'Yes', it calls OPERATOR ACCESS PROCEDURE (11). If 'No', it sends MESSAGE 'ERROR' (67) and DISCONNECT (68). Both (11) and (68) lead to END (99).](fa859e4e468bfb2710a94527f2c504af_img.jpg)
+
+```
+
+graph TD
+    START([START  
+(18)]) --> PROMPT[PROMPT FOR  
+CALLED NUMBER  
+(62)]
+    PROMPT --> INPUT[INPUT DIALLED  
+DIGITS  
+(63)]
+    INPUT --> ALL_DIGITS{ALL DIGITS  
+RECEIVED?  
+(64)}
+    ALL_DIGITS -- Yes --> END([END  
+(99)])
+    ALL_DIGITS -- No --> TIMEOUT{TIMEOUT?  
+(65)}
+    TIMEOUT -- No --> INPUT
+    TIMEOUT -- Yes --> NOTE["(Note)"]
+    NOTE --> FALLBACK{OPERATOR  
+FALLBACK  
+AVAIL?  
+(66)}
+    FALLBACK -- Yes --> ACCESS[OPERATOR  
+ACCESS  
+PROCEDURE  
+(11)]
+    FALLBACK -- No --> MESSAGE["MESSAGE  
+'ERROR'  
+(67)"]
+    MESSAGE --> DISCONNECT[DISCONNECT  
+(68)]
+    ACCESS --> END
+    DISCONNECT --> END
+
+```
+
+Flowchart of the Called number procedure (18). The process starts with START (18), followed by PROMPT FOR CALLED NUMBER (62). It then enters a loop: INPUT DIALLED DIGITS (63) -> ALL DIGITS RECEIVED? (64). If 'Yes', it goes to END (99). If 'No', it checks TIMEOUT? (65). If 'No' at (65), it loops back to INPUT DIALLED DIGITS (63). If 'Yes' at (65) (with a Note), it checks OPERATOR FALLBACK AVAIL? (66). If 'Yes', it calls OPERATOR ACCESS PROCEDURE (11). If 'No', it sends MESSAGE 'ERROR' (67) and DISCONNECT (68). Both (11) and (68) lead to END (99).
+
+T0105580-96/d05
+
+NOTE – Retry possibilities may be allowed.
+
+**Figure B.5/E.116 – Called number procedure (18)**
+
+# ITU-T RECOMMENDATIONS SERIES
+
+|                 |                                                                                                                                |
+|-----------------|--------------------------------------------------------------------------------------------------------------------------------|
+| Series A        | Organization of the work of the ITU-T                                                                                          |
+| Series B        | Means of expression: definitions, symbols, classification                                                                      |
+| Series C        | General telecommunication statistics                                                                                           |
+| Series D        | General tariff principles                                                                                                      |
+| <b>Series E</b> | <b>Overall network operation, telephone service, service operation and human factors</b>                                       |
+| Series F        | Non-telephone telecommunication services                                                                                       |
+| Series G        | Transmission systems and media, digital systems and networks                                                                   |
+| Series H        | Audiovisual and multimedia systems                                                                                             |
+| Series I        | Integrated services digital network                                                                                            |
+| Series J        | Transmission of television, sound programme and other multimedia signals                                                       |
+| Series K        | Protection against interference                                                                                                |
+| Series L        | Construction, installation and protection of cables and other elements of outside plant                                        |
+| Series M        | TMN and network maintenance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits |
+| Series N        | Maintenance: international sound programme and television transmission circuits                                                |
+| Series O        | Specifications of measuring equipment                                                                                          |
+| Series P        | Telephone transmission quality, telephone installations, local line networks                                                   |
+| Series Q        | Switching and signalling                                                                                                       |
+| Series R        | Telegraph transmission                                                                                                         |
+| Series S        | Telegraph services terminal equipment                                                                                          |
+| Series T        | Terminals for telematic services                                                                                               |
+| Series U        | Telegraph switching                                                                                                            |
+| Series V        | Data communication over the telephone network                                                                                  |
+| Series X        | Data networks and open system communication                                                                                    |
+| Series Z        | Programming languages                                                                                                          |

marked/E/T-REC-E.118-200605-I_PDF-E/raw.md

@@ -0,0 +1,441 @@
+
+
+**ITU-T**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+**E.118**
+
+(05/2006)
+
+SERIES E: OVERALL NETWORK OPERATION,  
+TELEPHONE SERVICE, SERVICE OPERATION AND  
+HUMAN FACTORS
+
+International operation – General provisions concerning  
+Administrations
+
+---
+
+**The international telecommunication charge  
+card**
+
+ITU-T Recommendation E.118
+
+# ITU-T E-SERIES RECOMMENDATIONS
+
+# OVERALL NETWORK OPERATION, TELEPHONE SERVICE, SERVICE OPERATION AND HUMAN FACTORS
+
+|                                                                                                   |                    |
+|---------------------------------------------------------------------------------------------------|--------------------|
+| INTERNATIONAL OPERATION                                                                           |                    |
+| Definitions                                                                                       | E.100–E.103        |
+| <b>General provisions concerning Administrations</b>                                              | <b>E.104–E.119</b> |
+| General provisions concerning users                                                               | E.120–E.139        |
+| Operation of international telephone services                                                     | E.140–E.159        |
+| Numbering plan of the international telephone service                                             | E.160–E.169        |
+| International routing plan                                                                        | E.170–E.179        |
+| Tones in national signalling systems                                                              | E.180–E.189        |
+| Numbering plan of the international telephone service                                             | E.190–E.199        |
+| Maritime mobile service and public land mobile service                                            | E.200–E.229        |
+| OPERATIONAL PROVISIONS RELATING TO CHARGING AND ACCOUNTING IN THE INTERNATIONAL TELEPHONE SERVICE |                    |
+| Charging in the international telephone service                                                   | E.230–E.249        |
+| Measuring and recording call durations for accounting purposes                                    | E.260–E.269        |
+| UTILIZATION OF THE INTERNATIONAL TELEPHONE NETWORK FOR NON-TELEPHONY APPLICATIONS                 |                    |
+| General                                                                                           | E.300–E.319        |
+| Phototelegraphy                                                                                   | E.320–E.329        |
+| ISDN PROVISIONS CONCERNING USERS                                                                  | E.330–E.349        |
+| INTERNATIONAL ROUTING PLAN                                                                        | E.350–E.399        |
+| NETWORK MANAGEMENT                                                                                |                    |
+| International service statistics                                                                  | E.400–E.404        |
+| International network management                                                                  | E.405–E.419        |
+| Checking the quality of the international telephone service                                       | E.420–E.489        |
+| TRAFFIC ENGINEERING                                                                               |                    |
+| Measurement and recording of traffic                                                              | E.490–E.505        |
+| Forecasting of traffic                                                                            | E.506–E.509        |
+| Determination of the number of circuits in manual operation                                       | E.510–E.519        |
+| Determination of the number of circuits in automatic and semi-automatic operation                 | E.520–E.539        |
+| Grade of service                                                                                  | E.540–E.599        |
+| Definitions                                                                                       | E.600–E.649        |
+| Traffic engineering for IP-networks                                                               | E.650–E.699        |
+| ISDN traffic engineering                                                                          | E.700–E.749        |
+| Mobile network traffic engineering                                                                | E.750–E.799        |
+| QUALITY OF TELECOMMUNICATION SERVICES: CONCEPTS, MODELS, OBJECTIVES AND DEPENDABILITY PLANNING    |                    |
+| Terms and definitions related to the quality of telecommunication services                        | E.800–E.809        |
+| Models for telecommunication services                                                             | E.810–E.844        |
+| Objectives for quality of service and related concepts of telecommunication services              | E.845–E.859        |
+| Use of quality of service objectives for planning of telecommunication networks                   | E.860–E.879        |
+| Field data collection and evaluation on the performance of equipment, networks and services       | E.880–E.899        |
+| OTHER                                                                                             | E.900–E.999        |
+
+For further details, please refer to the list of ITU-T Recommendations.
+
+## **ITU-T Recommendation E.118**
+
+## **The international telecommunication charge card**
+
+## **Summary**
+
+Telecommunication charge cards may be issued by Operating Agencies (OAs) to allow customers to use their card in connection with various international services at appropriate charges for each transaction and have the charges billed to their account in the country where the OA issued the charge card. Cards issued by OAs in accordance with this Recommendation conform to the appropriate ISO standards.
+
+This Recommendation has been revised to allow alternative, application-specific standards for IC cards where unique form factors require such alternatives.
+
+## **Source**
+
+ITU-T Recommendation E.118 was approved on 11 May 2006 by ITU-T Study Group 2 (2005-2008) under the Resolution 1 approval process.
+
+## **History**
+
+|     |       |            |
+|-----|-------|------------|
+| 1.0 | E.118 | 1988-11-25 |
+| 2.0 | E.118 | 1992-08-04 |
+| 3.0 | E.118 | 1996-07-19 |
+| 4.0 | E.118 | 2001-02-02 |
+| 5.0 | E.118 | 2006-05-11 |
+
+## FOREWORD
+
+The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis.
+
+The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics.
+
+The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1.
+
+In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC.
+
+### NOTE
+
+In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure e.g. interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some other obligatory language such as "must" and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party.
+
+## INTELLECTUAL PROPERTY RIGHTS
+
+ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process.
+
+As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database.
+
+© ITU 2006
+
+All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU.
+
+## CONTENTS
+
+|                                                                                              | Page |
+|----------------------------------------------------------------------------------------------|------|
+| 1 Scope .....                                                                                | 1    |
+| 2 References.....                                                                            | 1    |
+| 3 Abbreviations.....                                                                         | 1    |
+| 4 Numbering system.....                                                                      | 1    |
+| 4.1 Card numbering structure .....                                                           | 1    |
+| 4.2 Issuer identifier number assignment and registration procedure.....                      | 2    |
+| 4.3 Information content .....                                                                | 5    |
+| 5 Printed cards .....                                                                        | 5    |
+| 6 Magnetic stripe cards.....                                                                 | 5    |
+| 6.1 Encoding requirements.....                                                               | 5    |
+| 6.2 Expiration date.....                                                                     | 6    |
+| 6.3 Service code.....                                                                        | 6    |
+| 6.4 Discretionary data.....                                                                  | 6    |
+| 7 Integrated Circuit (IC) cards.....                                                         | 6    |
+| Annex A – Service code assignments .....                                                     | 7    |
+| Appendix I – Implementation guidelines for the assignment of issuer identifier numbers ..... | 8    |
+
+
+
+## The international telecommunication charge card
+
+## 1 Scope
+
+Telecommunication charge cards may be issued by Operating Agencies (OAs) to allow customers to use their card in connection with various international services at appropriate charges for each transaction and have the charges billed to their account in the country where the OA issued the charge card. Cards issued by OAs in accordance with this Recommendation conform to the appropriate ISO Standards.
+
+## 2 References
+
+The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation.
+
+- [1] ISO/IEC 7812-1:2000, *Identification cards – Identification of issuers – Part 1: Numbering system*.
+- [2] ITU-T Recommendation E.164 (2005), *The international public telecommunication numbering plan*.
+- [3] ISO/IEC 7812-2:2000, *Identification cards – Identification of issuers – Part 2: Application and registration procedures*.
+
+## 3 Abbreviations
+
+This Recommendation uses the following abbreviations:
+
+- IC Integrated Circuit
+- IIN Issuer Identifier Number
+- MII Major Industry Identifier
+
+## 4 Numbering system
+
+### 4.1 Card numbering structure
+
+The numbering of the card to be issued by OAs shall be as follows based on ISO/IEC 7812-1 [1] (Identification cards – Identification of issuers – Part 1: Numbering system) and ISO/IEC 7812-2 [3] (Identification cards – Identification of issuers – Part 2: Application and registration procedures).
+
+The maximum length of the visible card number (primary account number) shall be 19 characters and is composed of the following subparts (see Figure 1):
+
+- Major Industry Identifier (MII);
+- country code;
+- issuer identifier;
+- individual account identification number;
+- parity check digit computed according to the Luhn formula (see ISO/IEC 7812-1, Annex B [1]). In addition to the parity check digit, OAs may incorporate a validation check device in some location on the card which could be changed when new cards are issued.
+
+NOTE – Major industry and issuer identifier numbers of the form 66xxxx have already been assigned to some Administrations as a transitional measure. Charge cards of this type are fully compatible with ISO Standards.
+
+![Diagram of the charge card numbering system showing the structure of the 19-digit primary account number. The diagram is a horizontal bar divided into 19 cells. The first cell contains '8', the second contains '9'. Brackets above the bar label the first two cells as 'Issuer identification number (digits variable, maximum 7)'. A bracket above the entire 19-cell bar is labeled 'Primary account number 19 visible characters (maximum)'. Below the bar, arrows point from descriptive text to specific parts: 'Major industry identifier (MII) (ISO/IEC 7812-1) [1] "89" is assigned for telecommunication purposes' points to the first cell; 'Country code: ITU-T Rec. E.164 [2] (variable, 1 to 3 digits)' points to the second cell; 'Issuer identifier number (variable, but fixed number of digits within a country or world zone where appropriate)' points to a group of cells following the country code; 'Individual account identification number (variable, but fixed number of digits for each particular issuer identifier number)' points to the middle section of cells; and 'Luhn check digit' points to the final cell. The label 'E.118_F01' is in the bottom right.](d0abac95583b52a3b35f74a215567334_img.jpg)
+
+Diagram of the charge card numbering system showing the structure of the 19-digit primary account number. The diagram is a horizontal bar divided into 19 cells. The first cell contains '8', the second contains '9'. Brackets above the bar label the first two cells as 'Issuer identification number (digits variable, maximum 7)'. A bracket above the entire 19-cell bar is labeled 'Primary account number 19 visible characters (maximum)'. Below the bar, arrows point from descriptive text to specific parts: 'Major industry identifier (MII) (ISO/IEC 7812-1) [1] "89" is assigned for telecommunication purposes' points to the first cell; 'Country code: ITU-T Rec. E.164 [2] (variable, 1 to 3 digits)' points to the second cell; 'Issuer identifier number (variable, but fixed number of digits within a country or world zone where appropriate)' points to a group of cells following the country code; 'Individual account identification number (variable, but fixed number of digits for each particular issuer identifier number)' points to the middle section of cells; and 'Luhn check digit' points to the final cell. The label 'E.118\_F01' is in the bottom right.
+
+**Figure 1/E.118 – Charge card numbering system**
+
+### 4.2 Issuer identifier number assignment and registration procedure
+
+- The assignment of specific issuer identifier numbers should be the responsibility of a country or group of countries as appropriate. These numbers should only be assigned to OAs with the agreement of their Administrations.
+- These issuer identifier numbers are normally used to distinguish among multiple OAs who issue cards within a country. However, these numbers may also be used to distinguish individual countries sharing the same country code (as defined in ITU-T Rec. E.164 [2]) or, if appropriate, to distinguish both countries and issuers.
+- The Director of TSB is responsible for the registration and/or cancellation of issuer identifier numbers (IINs) for OAs with the approval of their Administrations. An illustrative registration form is contained in Figure 2.
+
+- d) A one-time fee shall be collected in order for an IIN to be assigned and registered by TSB. Applications shall be accompanied by evidence of payment to ITU of the one-time fee.
+- e) In the event of technical or operational difficulties in allocating an IIN, the Director of TSB should consult the Chairman of Study Group 2.
+- f) The TSB shall maintain a list of the allocated IINs.
+- g) Additions, deletions and changes to this list should be published in the first available ITU Operational Bulletin.
+- h) The consolidated list of allocated IINs should be published periodically in the ITU Operational Bulletin.
+
+#### Registration form for a single Issuer Identifier Number for the international telecommunication charge card
+
+To be returned with registration fee to:
+
+INTERNATIONAL TELECOMMUNICATION UNION  
+TELECOMMUNICATION STANDARDIZATION BUREAU  
+PLACE DES NATIONS, CH - 1211 GENEVE 20, SWITZERLAND  
+FAX: +41 22 730 5853
+
+##### A. TO BE COMPLETED BY APPLICANT (Card Issuer)
+
+|                                                                                                                                                          |           |                 |
+|----------------------------------------------------------------------------------------------------------------------------------------------------------|-----------|-----------------|
+| Name or organization                                                                                                                                     |           |                 |
+| Address to be registered (maximum two lines, 30 characters per line)                                                                                     |           |                 |
+| Principal contact in organization                                                                                                                        |           |                 |
+| Telephone number<br>+                                                                                                                                    | E-mail    | Fax number<br>+ |
+| Address for correspondence                                                                                                                               |           |                 |
+| Effective date of usage or cancellation                                                                                                                  |           |                 |
+| Date                                                                                                                                                     | Signature |                 |
+| In signing this form, the applicant accepts that further IINs will not be assigned to identify products, services, technologies or geographic locations. |           |                 |
+
+##### B. TO BE COMPLETED AND APPROVED BY THE TELECOMMUNICATIONS ADMINISTRATION<sup>a)</sup> OR DULY AUTHORIZED COORDINATING ORGANIZATION
+
+- a) Action requested (check appropriate box)   Registration    or Cancellation
+- b) Major industry identifier (MII): 89
+- c) Country code (CC): (according to the List, Complement to ITU-T Rec. E.164)
+- d) Issuer identifier number: (according to ITU-T Rec. E.118)
+
+|                                |           |
+|--------------------------------|-----------|
+| Name of approving organization |           |
+| Date                           | Signature |
+
+##### C. TO BE COMPLETED BY ITU (CENTRAL REGISTRATION AUTHORITY)
+
+|                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |   |   |  |  |  |  |  |       |
+|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---|---|--|--|--|--|--|-------|
+| Issuer Identification Number registered or cancelled<br><table style="width: 100%; border-collapse: collapse;"> <tr> <td style="border: 1px solid black; width: 14.28%; text-align: center; padding: 2px;">8</td> <td style="border: 1px solid black; width: 14.28%; text-align: center; padding: 2px;">9</td> <td style="border: 1px solid black; width: 14.28%;"></td> <td style="border: 1px solid black; width: 14.28%;"></td> <td style="border: 1px solid black; width: 14.28%;"></td> <td style="border: 1px solid black; width: 14.28%;"></td> <td style="border: 1px solid black; width: 14.28%;"></td> </tr> </table> | 8 | 9 |  |  |  |  |  | Date: |
+| 8                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               | 9 |   |  |  |  |  |  |       |
+
+a) and/or Operating Agency (OA).
+
+#### METHOD OF PAYMENT (Please specify the form of payment used)
+
+- Switzerland: to ITU's current postal account, Geneva 12-50-3;
+- All other countries:   - by international money order, or  
+  - by bank transfer to UBS SA, ITU Geneva, Geneva (Switzerland)  
+  ITU Account No. 240-C8765565.0
+
+(Payment may also be effected by a cheque made out in another currency freely convertible into Swiss francs, provided that the cheque, when cashed and converted, will cover the amount of the registration fee in Swiss francs.)
+
+- By credit card   EUROCARD-MASTERCARD  VISA  AMERICAN EXPRESS
+
+Credit card number: Valid date:  
+Holder's name: Signature:
+
+(This form must be signed if you pay by credit card.) **Please note:** Letters of credit are not accepted.
+
+**Figure 2/E.118 – Illustrative registration form**
+
+### 4.3 Information content
+
+The information on an international telecommunication charge card shall clearly include:
+
+- 1) the card number (on a combined national/international card, the national number, if different, should be appropriately designated);
+
+and should optionally include:
+
+- 2) the name of the issuing OA<sup>1</sup> and, where appropriate, the country of issue;
+- 3) the card holder's name and signature;
+- 4) the date of expiry, in the format of either "MM/YY" or "MM-YY";
+- 5) instructions on how the card should be used. (Some OAs may prefer to issue instructions separately.)
+
+In addition, the logo of the ITU may, at the card issuer's option, appear somewhere on the card to facilitate recognition of the card by card acceptors where presentation of the card is required as a part of the service (i.e., bureau services).
+
+## 5 Printed cards
+
+The charge card should be designed to be conveniently carried. Current ISO Standards define the dimensions of financial transaction cards to be 85.60 mm × 53.98 mm (3.370 × 2.125 inches) and the ITU-T considers that telephone charge cards issued by OAs should have similar dimensions.
+
+## 6 Magnetic stripe cards
+
+For maximum flexibility, convenience of use and economic benefits, the magnetic stripe cards to be issued by OAs should conform to the relevant ISO Standards concerning materials, recording techniques, physical dimensions and the type and format of embossed information.
+
+These are:
+
+- ISO/IEC 7810: Identification cards – Physical characteristics.
+- ISO/IEC 7811-1: Identification cards – Recording technique – Part 1: Embossing.
+- ISO/IEC 7811-2: Identification cards – Recording technique – Part 2: Magnetic stripe – Low coercivity.
+- ISO/IEC 7811-6: Identification cards – Recording technique – Part 6: Magnetic stripe – High coercivity.
+- ISO/IEC 7813: Identification cards – Financial transaction cards.
+
+### 6.1 Encoding requirements
+
+Track 2 of the magnetic stripe on the telecommunication charge card shall be used as a primary means of communicating data encoded on the magnetic stripe. The Primary Account Number (PAN) is the only field that is required to be encoded. An example of the encoding of this minimum information is contained in Table 1.
+
+---
+
+<sup>1</sup> Although optional, card issuer OAs are encouraged to include their name, where possible, to avoid problems when the card is presented to an operator.
+
+**Table 1/E.118 – Minimum encoding requirements**
+
+|     |                               |                                |
+|-----|-------------------------------|--------------------------------|
+| STX | Start Sentinel                | BCD 11                         |
+| PAN | Primary Account Number        | 89...(e.g., 8912538360010000L) |
+| FS  | Field Separator               | BCD 13                         |
+| ED  | Expiration Date               | BCD 13                         |
+| SC  | Service Code                  | BCD 13                         |
+| DD  | Discretionary Data            | null                           |
+| ETX | End Sentinel                  | BCD 15                         |
+| LRC | Longitudinal Redundancy Check | [1 digit]                      |
+
+Card issuers may, at their own discretion, encode data on track 2 of the telecommunication charge card in addition to the required information. This data is defined below. An example of the encoding of all such information (except discretionary data) is contained in Table 2.
+
+**Table 2/E.118 – Full encoding requirements**
+
+|     |                               |                                                                                                                                        |
+|-----|-------------------------------|----------------------------------------------------------------------------------------------------------------------------------------|
+| STX | Start Sentinel                | BCD 11                                                                                                                                 |
+| PAN | Primary Account Number        | 89...(e.g., 9812538360010000L)                                                                                                         |
+| FS  | Field Separator               | BCD 13                                                                                                                                 |
+| ED  | Expiration Date               | YYMM (e.g., "9612" for December 1996)                                                                                                  |
+| SC  | Service Code                  | XXX (e.g., "125" – International use, positive authorization is mandatory, telecommunications services only with a PIN being required) |
+| DD  | Discretionary Data            | ...                                                                                                                                    |
+| ETX | End Sentinel                  | BCD 15                                                                                                                                 |
+| LRC | Longitudinal Redundancy Check | [1 digit]                                                                                                                              |
+
+### 6.2 Expiration date
+
+If the expiration date is embossed on the front of the telecommunication charge card, it should also be encoded on track 2 of the magnetic stripe. The format is defined by ISO/IEC 7813 as YYMM. The position of the expiration date is shown in Table 2 and is dependent on encoding requirements and service agreements. If the expiration date is not embossed on the front of the card and it is not encoded on the magnetic stripe, a field separator shall be encoded in its place (see Table 1).
+
+### 6.3 Service code
+
+OAs are encouraged to encode information within the service code field. If it is not encoded on the magnetic stripe, a field separator shall be encoded in its place (see Table 1). There are three positions to the service code field. The positions and the interpretation for each of the possible values are contained in Annex A.
+
+### 6.4 Discretionary data
+
+Any information contained in the discretionary data field is for further study.
+
+## 7 Integrated Circuit (IC) cards
+
+The standard for the IC card is to be established by ISO/IEC JTC 1/SC 17. In addition, specific applications (e.g., SIM cards in GSM applications and USIM cards in UMTS/IMT-2000 applications) may make use of alternative standards to address unique form factors of their application.
+
+## Annex A
+
+### Service code assignments
+
+Tables A.1 to A.3 describe the various values that may be used in each of the three positions of the service code field. For each value, the second column of each table describes how the value is interpreted specifically for cards defined by this Recommendation.
+
+The first digit of the service code describes the type of interchange permissible for the card. The second digit describes the level of authorization processing required to validate the card. For this Recommendation, this value is only interpreted for card systems using fully automated validation (see ITU-T Rec. E.113). The third digit describes the types of services allowable by the card holder.
+
+**Table A.1/E.118 – Permissible interchange values – Position 1**
+
+| Values | Telecommunication usage                                                   |
+|--------|---------------------------------------------------------------------------|
+| 0      | Not used                                                                  |
+| 1      | International use is permitted                                            |
+| 2      | International use is permitted for integrated circuit cards               |
+| 3      | Not used                                                                  |
+| 4      | Not used                                                                  |
+| 5      | Restricted to use on national networks only                               |
+| 6      | Restricted to use on national networks only, for integrated circuit cards |
+| 7      | Restricted for use only on the card issuer's network                      |
+| 8      | Not used                                                                  |
+| 9      | Usable for test purposes only                                             |
+
+**Table A.2/E.118 – Level of authorization – Position 2**
+
+| Values | Telecommunication usage                                                                                                                            |
+|--------|----------------------------------------------------------------------------------------------------------------------------------------------------|
+| 0      | No specific authorization defined                                                                                                                  |
+| 1      | Not used                                                                                                                                           |
+| 2      | Positive authorization is required when used in a full validation environment                                                                      |
+| 3      | Not used                                                                                                                                           |
+| 4      | Positive authorization is required when used in a full validation environment but special backup arrangements are defined in the service agreement |
+| 5      | Not used                                                                                                                                           |
+| 6      | Not used                                                                                                                                           |
+| 7      | Not used                                                                                                                                           |
+| 8      | Not used                                                                                                                                           |
+| 9      | Not used                                                                                                                                           |
+
+**Table A.3/E.118 – Service availability – Position 3**
+
+| <b>Values</b> | <b>Telecommunication usage</b>                                      |
+|---------------|---------------------------------------------------------------------|
+| 0             | Card not restricted to telecommunication services; PIN required     |
+| 1             | Card not restricted to telecommunication services                   |
+| 2             | Can be used to charge telecommunication services only               |
+| 3             | Not used within the scope of ITU-T Rec. E.116                       |
+| 4             | Not used within the scope of ITU-T Rec. E.116                       |
+| 5             | Can be used to charge telecommunication services only; PIN required |
+| 6             | Not used                                                            |
+| 7             | Not used                                                            |
+| 8             | Not used                                                            |
+| 9             | Not used                                                            |
+
+## **Appendix I**
+
+### **Implementation guidelines for the assignment of issuer identifier numbers**
+
+Card issuers will be assigned a single Issuer Identifier Number (IIN) from the ITU's block of "89" IINs. To assist card issuers in effectively planning card services and the TSB in processing applications, the following information may be helpful:
+
+- a) Separate Issuer Identifier Numbers should not be used to differentiate between different products or services for which the card may be used.
+- b) Separate Issuer Identifier Numbers should not be used to differentiate between technologies implemented in the card (e.g., magnetic stripe versus integrated circuit cards) or for products and services based on or implemented using different technologies (e.g., IP-based voice services versus circuit switched voice services).
+- c) Separate Issuer Identifier Numbers should not be used to differentiate between different branches or subsidiaries of the same corporation. However, situations where card issuers operating in different countries or regulatory environments where different accounting or settlement rates exist, the assignment of additional IINs to a specific card issuer may be justified.
+
+If card issuers need to make such differentiation, different values within the leading digits of the Individual Account Identification should be used.
+
+
+
+## SERIES OF ITU-T RECOMMENDATIONS
+
+|                 |                                                                                             |
+|-----------------|---------------------------------------------------------------------------------------------|
+| Series A        | Organization of the work of ITU-T                                                           |
+| Series D        | General tariff principles                                                                   |
+| <b>Series E</b> | <b>Overall network operation, telephone service, service operation and human factors</b>    |
+| Series F        | Non-telephone telecommunication services                                                    |
+| Series G        | Transmission systems and media, digital systems and networks                                |
+| Series H        | Audiovisual and multimedia systems                                                          |
+| Series I        | Integrated services digital network                                                         |
+| Series J        | Cable networks and transmission of television, sound programme and other multimedia signals |
+| Series K        | Protection against interference                                                             |
+| Series L        | Construction, installation and protection of cables and other elements of outside plant     |
+| Series M        | Telecommunication management, including TMN and network maintenance                         |
+| Series N        | Maintenance: international sound programme and television transmission circuits             |
+| Series O        | Specifications of measuring equipment                                                       |
+| Series P        | Telephone transmission quality, telephone installations, local line networks                |
+| Series Q        | Switching and signalling                                                                    |
+| Series R        | Telegraph transmission                                                                      |
+| Series S        | Telegraph services terminal equipment                                                       |
+| Series T        | Terminals for telematic services                                                            |
+| Series U        | Telegraph switching                                                                         |
+| Series V        | Data communication over the telephone network                                               |
+| Series X        | Data networks, open system communications and security                                      |
+| Series Y        | Global information infrastructure, Internet protocol aspects and next-generation networks   |
+| Series Z        | Languages and general software aspects for telecommunication systems                        |

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+
+
+![ITU logo](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg)
+
+The logo of the International Telecommunication Union (ITU) features the letters 'ITU' in a bold, sans-serif font, superimposed on a stylized globe with latitude and longitude lines.
+
+ITU logo
+
+INTERNATIONAL TELECOMMUNICATION UNION
+
+**ITU-T**
+
+**E.122**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+**TELEPHONE NETWORK AND ISDN**
+
+**OPERATION, NUMBERING, ROUTING  
+AND MOBILE SERVICE**
+
+---
+
+**MEASURES TO REDUCE CUSTOMER  
+DIFFICULTIES IN THE INTERNATIONAL  
+TELEPHONE SERVICE**
+
+**ITU-T Recommendation E.122**
+
+(Extract from the *Blue Book*)
+
+---
+
+# NOTES
+
+1 ITU-T Recommendation E.122 was published in Fascicle II.2 of the *Blue Book*. This file is an extract from the *Blue Book*. While the presentation and layout of the text might be slightly different from the *Blue Book* version, the contents of the file are identical to the *Blue Book* version and copyright conditions remain unchanged (see below).
+
+2 In this Recommendation, the expression “Administration” is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+## **MEASURES TO REDUCE CUSTOMER DIFFICULTIES IN THE INTERNATIONAL TELEPHONE SERVICE**
+
+## **1 General**
+
+A common problem in customer dialling in the international automatic telephone service is the erroneous dialling of the trunk prefix of the country of destination. In the international service, this trunk prefix must not be dialled. The following measures have been tried and have proven very effective; they are recommended to reduce this problem.
+
+## **2 Recorded announcement**
+
+2.1 It is recommended that, at International Switching Centres (ISCs) where the trunk prefix can be detected, the call should be blocked and automatically routed to a recorded announcement which would instruct the customer to dial the call again without dialling the trunk prefix (see also Recommendation E.182, § A.2.8).
+
+2.2 An example of such an announcement is: "Please do not dial a zero after the country code when calling this country. Please hang up and try your call again".
+
+2.3 The call is blocked and the announcement given from either the outgoing ISC<sup>1)</sup> or the incoming ISC<sup>1)</sup>. The announcement should be in the language of either the originating or terminating country. It is not known whether the language of the originating or of the terminating country is most acceptable to the customers<sup>2)</sup>.
+
+2.4 When applying this method at an outgoing ISC, care must be exercised in selecting the countries to which this measure is applied, as the trunk prefix which is to be blocked might be a valid trunk code for some countries. The employment of this measure should be preceded by a review of the pertinent information including national numbering plans and tests, as well as operator access codes, and by an explanation to the other Administrations involved of the plan to block calls having an erroneous trunk prefix.
+
+## **3 Customer instructions**
+
+3.1 To avoid premature abandonment of attempted calls, customers should be advised to wait longer than usual for a call to be established.
+
+3.2 It is recommended that when Administrations prepare dialling instructions for their customers they emphasize that the trunk prefix should not be dialled in the international automatic telephone service.
+
+This is necessary when the destination country conventionally writes its telephone numbers such that the trunk prefix appears with the trunk code (in parentheses). To compose a comprehensible and accurate statement can prove difficult: suitable forms are given below.
+
+3.2.1 The first form is suitable for explanation. It could be accompanied by numerical examples of complete international telephone numbers:
+
+---
+
+1) The exact source of the announcements would be any suitable place, although it is preferable in traffic terms to use a source as close to the call origin as possible.
+
+2) In using the language of the originating country at an incoming international switching centre, Administrations should beware of using an inappropriate language in cases where calls are routed through a transit country.
+
+“The trunk prefix zero that precedes the national trunk code in several countries should be omitted after the country code in international dialling. For example, to call Amsterdam (020) from another country, you dial 20 after the country code for the Netherlands, which is 31. Some countries have a different trunk prefix that should be omitted in international dialling. For example, in Finland the trunk prefix is 9, while the trunk code for Helsinki is 0; to call Helsinki (90) from another country, you dial 0 after the country code for Finland, which is 358.”
+
+“Other countries do not normally include their trunk prefix with the trunk code when writing telephone numbers: in such cases you should not omit the first digits in international calling.”
+
+An example of the use of this statement is given in Recommendation E.126, Annex A.
+
+#### 3.2.2 The second form may be more suitable in some contexts:
+
+“In many countries, a special prefix (often a zero) is normally printed in telephone numbers with the trunk code, because it must always be dialled for long-distance calls within that country. This prefix must *not* be dialled when making international calls to such countries. If your international call is not *successful*, you should check to see if the first digit of the (apparent) trunk code is a prefix that must not be dialled.”
+
+3.3 It is believed that widespread use of the notation given in Recommendation E.123 for national and international telephone numbers would lead to a reduction in the incidence of erroneous dialling of the foreign national trunk prefix, and of other errors, in international dialling. Administrations should encourage the use of this notation.

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+
+
+![ITU logo: A globe with a lightning bolt and the letters ITU.](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg)
+
+ITU logo: A globe with a lightning bolt and the letters ITU.
+
+INTERNATIONAL TELECOMMUNICATION UNION
+
+**ITU-T**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+**E.123**
+
+(02/2001)
+
+SERIES E: OVERALL NETWORK OPERATION,  
+TELEPHONE SERVICE, SERVICE OPERATION AND  
+HUMAN FACTORS
+
+International operation – General provisions concerning  
+users
+
+---
+
+**Notation for national and international  
+telephone numbers, e-mail addresses and  
+Web addresses**
+
+ITU-T Recommendation E.123
+
+(Formerly CCITT Recommendation)
+
+---
+
+# **OVERALL NETWORK OPERATION, TELEPHONE SERVICE, SERVICE OPERATION AND HUMAN FACTORS**
+
+|                                                                                                          |                    |
+|----------------------------------------------------------------------------------------------------------|--------------------|
+| <b>INTERNATIONAL OPERATION</b>                                                                           |                    |
+| Definitions                                                                                              | E.100–E.103        |
+| General provisions concerning Administrations                                                            | E.104–E.119        |
+| <b>General provisions concerning users</b>                                                               | <b>E.120–E.139</b> |
+| Operation of international telephone services                                                            | E.140–E.159        |
+| Numbering plan of the international telephone service                                                    | E.160–E.169        |
+| International routing plan                                                                               | E.170–E.179        |
+| Tones in national signalling systems                                                                     | E.180–E.189        |
+| Numbering plan of the international telephone service                                                    | E.190–E.199        |
+| Maritime mobile service and public land mobile service                                                   | E.200–E.229        |
+| <b>OPERATIONAL PROVISIONS RELATING TO CHARGING AND ACCOUNTING IN THE INTERNATIONAL TELEPHONE SERVICE</b> |                    |
+| Charging in the international telephone service                                                          | E.230–E.249        |
+| Measuring and recording call durations for accounting purposes                                           | E.260–E.269        |
+| <b>UTILIZATION OF THE INTERNATIONAL TELEPHONE NETWORK FOR NON-TELEPHONY APPLICATIONS</b>                 |                    |
+| General                                                                                                  | E.300–E.319        |
+| Phototelegraphy                                                                                          | E.320–E.329        |
+| <b>ISDN PROVISIONS CONCERNING USERS</b>                                                                  | <b>E.330–E.349</b> |
+| <b>INTERNATIONAL ROUTING PLAN</b>                                                                        | <b>E.350–E.399</b> |
+| <b>NETWORK MANAGEMENT</b>                                                                                |                    |
+| International service statistics                                                                         | E.400–E.409        |
+| International network management                                                                         | E.410–E.419        |
+| Checking the quality of the international telephone service                                              | E.420–E.489        |
+| <b>TRAFFIC ENGINEERING</b>                                                                               |                    |
+| Measurement and recording of traffic                                                                     | E.490–E.505        |
+| Forecasting of traffic                                                                                   | E.506–E.509        |
+| Determination of the number of circuits in manual operation                                              | E.510–E.519        |
+| Determination of the number of circuits in automatic and semi-automatic operation                        | E.520–E.539        |
+| Grade of service                                                                                         | E.540–E.599        |
+| Definitions                                                                                              | E.600–E.649        |
+| Traffic engineering for IP-networks                                                                      | E.650–E.699        |
+| ISDN traffic engineering                                                                                 | E.700–E.749        |
+| Mobile network traffic engineering                                                                       | E.750–E.799        |
+| <b>QUALITY OF TELECOMMUNICATION SERVICES: CONCEPTS, MODELS, OBJECTIVES AND DEPENDABILITY PLANNING</b>    |                    |
+| Terms and definitions related to the quality of telecommunication services                               | E.800–E.809        |
+| Models for telecommunication services                                                                    | E.810–E.844        |
+| Objectives for quality of service and related concepts of telecommunication services                     | E.845–E.859        |
+| Use of quality of service objectives for planning of telecommunication networks                          | E.860–E.879        |
+| Field data collection and evaluation on the performance of equipment, networks and services              | E.880–E.899        |
+
+*For further details, please refer to the list of ITU-T Recommendations.*
+
+## **Notation for national and international telephone numbers, e-mail addresses and Web addresses**
+
+## **Summary**
+
+This Recommendation applies specifically to the printing of national and international telephone numbers, electronic mail addresses and Web addresses on letterheads, business cards, bills, etc. Regard has been given to the printing of existing telephone directories. The standard notation for printing telephone numbers, E-mail addresses and Web addresses helps to reduce difficulties and errors, since this address information must be entered exactly to be effective.
+
+###### **Source**
+
+ITU-T Recommendation E.123 was revised by ITU-T Study Group 2 (2001-2004) and approved under the WTSA Resolution 1 procedure on 2 February 2001.
+
+## FOREWORD
+
+The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis.
+
+The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics.
+
+The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1.
+
+In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC.
+
+### NOTE
+
+In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+### INTELLECTUAL PROPERTY RIGHTS
+
+ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process.
+
+As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database.
+
+© ITU 2001
+
+All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from ITU.
+
+## CONTENTS
+
+###### Page
+
+|     |                                                                   |   |
+|-----|-------------------------------------------------------------------|---|
+| 1   | General.....                                                      | 1 |
+| 2   | Notation for National and International Telephone Numbers .....   | 1 |
+| 3   | Notation for Electronic Mail Addresses .....                      | 2 |
+| 4   | Notation for Web Addresses.....                                   | 2 |
+| 5   | Classes of symbols.....                                           | 2 |
+| 6   | Diallable symbols .....                                           | 3 |
+| 7   | Procedural symbols.....                                           | 3 |
+| 7.1 | International prefix symbol.....                                  | 3 |
+| 7.2 | Use of parentheses .....                                          | 3 |
+| 7.3 | Multiple numbers reached through automatic search .....           | 3 |
+| 7.4 | Multiple numbers without automatic search.....                    | 4 |
+| 7.5 | In-dialling.....                                                  | 4 |
+| 7.6 | Symbol to indicate the existence of an additional dial tone ..... | 4 |
+| 8   | Information symbols .....                                         | 5 |
+| 9   | Spacing symbols .....                                             | 5 |
+| 10  | Facsimile number notation.....                                    | 5 |
+|     | Annex A .....                                                     | 6 |
+|     | Desirable properties of diallable symbols .....                   | 6 |
+| A.1 | Distinct from other diallable symbols.....                        | 6 |
+| A.2 | Widely known name .....                                           | 6 |
+| A.3 | Reproducible .....                                                | 6 |
+| A.4 | ITU-T-ISO compatible .....                                        | 6 |
+| A.5 | Made up of a single character .....                               | 6 |
+| A.6 | Abstract .....                                                    | 6 |
+| A.7 | Immediately recognizable as a diallable character .....           | 6 |
+
+
+
+## **Notation for national and international telephone numbers, e-mail addresses and Web addresses**
+
+## 1 General
+
+The statements below apply specifically to the printing of national and international telephone numbers, electronic mail addresses and Web addresses on letterheads, business cards, bills, etc. Regard has been given to the printing of existing telephone directories. The standard notation for printing telephone numbers, e-mail addresses and Web addresses helps to reduce difficulties and errors, since this address information must be entered exactly to be effective<sup>1</sup>.
+
+## 2 Notation for National and International Telephone Numbers
+
+2.1 The international number should be printed below the national number, with corresponding digits lined up one under the other to facilitate understanding of the composition of the international number as shown in the examples in 2.3 and 2.4 below.
+
+2.2 The words "National" and "International" in the appropriate language should be placed to the left of the national and international numbers, and these should be separated by a horizontal line.
+
+2.3 Either the symbol for telephone given in ITU-T E.121 or the word "Telephone" in the appropriate language should be placed to the left of (or above) the national and international numbers (to avoid confusion with other letterhead numbers). The + (plus) signifies the international prefix (see 7.1).
+
+|                 |           |               |                   |
+|-----------------|-----------|---------------|-------------------|
+| <i>Example:</i> | Telephone | National      | (607) 123 4567    |
+|                 |           | International | + 22 607 123 4567 |
+
+(Additional examples are shown in clause 6 below.)
+
+2.4 Because the countries of World Numbering Zone 1 (North America) have the country code 1, the same number as is used for the trunk prefix, and because dialling between these countries is the same as long-distance dialling within them, subscriber difficulties are avoided by using an alternative notation that has been found superior for use within these countries and equally good for subscribers in other countries dialling to Zone 1. This is to substitute for "National" on the upper line the phrase "Within N. Amer. zone".
+
+|                 |           |                      |                 |
+|-----------------|-----------|----------------------|-----------------|
+| <i>Example:</i> | Telephone | Within N. Amer. zone | (302) 123 4567  |
+|                 |           | International        | + 1302 123 4567 |
+
+2.5 If it is desirable to write only the international number, it should be written in the form:
+
+Telephone International      +22 607 123 4567
+
+2.6 If it is desirable, for example, to save space to accommodate printing several different numbers for FAX, mobile, etc. as well as an ordinary telephone number, each number should be printed as a short label (e.g., "Tel") followed by the number in the desired domestic or international format. The domestic format should be the same as used on the top line shown in 2.3, and the international format should be that shown on the bottom line in the same paragraph, but omitting the words "National" or "International" in each case.
+
+Example 1:                      Tel.                      (0607) 123 4567
+
+<sup>1</sup> It is also desirable that the printing of other information on letterheads, etc. such as telex and telegraph numbers and postal codes should not cause subscriber confusion with the telephone number.
+
+|                   |        |                  |
+|-------------------|--------|------------------|
+|                   | Fax    | (0607) 123 4568  |
+|                   | Mobile | (0607) 321 9876  |
+| <i>Example 2:</i> | Tel.   | +22 607 123 4567 |
+|                   | Fax    | +22 607 123 4568 |
+|                   | Mobile | +22 607 321 9876 |
+
+2.7 To show an extension number of a PABX without direct in-dialling, the nationally used word or abbreviation for "extension" should be written immediately after the telephone numbers and on the same line as the word "telephone", followed by the extension number itself.
+
+|                   |           |                      |                 |          |
+|-------------------|-----------|----------------------|-----------------|----------|
+| <i>Example 1:</i> | Telephone | Within N. Amer. zone | (302) 123 4567  | ext. 876 |
+|                   |           | International        | +1 302 123 4567 |          |
+
+|                   |                         |                  |          |
+|-------------------|-------------------------|------------------|----------|
+| <i>Example 2:</i> | Telephone international | +22 607 123 4567 | ext. 876 |
+|-------------------|-------------------------|------------------|----------|
+
+In this way, the extension number is separated from the digits to be dialled and, where it must be typed onto a letterhead, for example, it need be typed only once.
+
+2.8 It is often necessary to draw the attention of subscribers to the need to omit the foreign national trunk prefix when dialling an international call. This need occurs when the destination country conventionally writes its telephone numbers such that the trunk prefix appears with the trunk code (in parentheses). To compose a comprehensible and accurate statement can prove difficult: suitable forms are given in 3.2/E.122.
+
+2.9 Grouping the digits of a telephone number is advisable for reasons of memorizing, oral presentation, and printing.
+
+## 3 Notation for Electronic Mail Addresses
+
+3.1 An electronic mail address, if present, should be printed in the SMTP style below the telephone number information, and denoted by the label "E-mail" or some easily recognized variation such as "email," or the equivalent in the appropriate language.
+
+|                 |            |               |                  |
+|-----------------|------------|---------------|------------------|
+| <i>Example:</i> | Telephone: | National      | (0609) 123 4567  |
+|                 |            | International | +22 609 123 4567 |
+|                 | E-mail:    | jdeo@isp.com  |                  |
+
+3.2 If necessary to save space, it is permissible to omit the label "E-mail."
+
+## 4 Notation for Web Addresses
+
+4.1 A Web address, if present, should be printed without the prefix http:// near the e-mail address information, and denoted by the label "Web" or the equivalent in the appropriate language.
+
+|                 |            |                 |                  |
+|-----------------|------------|-----------------|------------------|
+| <i>Example:</i> | Telephone: | National        | (0609) 123 4567  |
+|                 |            | International   | +22 609 123 4567 |
+|                 | E-mail:    | jdeo@isp.com    |                  |
+|                 | Web:       | www.doecorp.com |                  |
+
+## 5 Classes of symbols
+
+5.1 There are four classes of symbols in national or international numbers. No symbol should be used in more than one class, nor should any symbol within a class have more than one meaning.
+
+5.2 These classes are:
+
+- diallable symbols (in French: *symboles servant à la composition du numéro*);
+- procedural symbols (in French: *symboles opératoires*);
+- information symbols (in French: *symboles d'information*);
+- spacing symbols (in French: *symboles d'espacement*).
+
+## 6 Diallable symbols
+
+A *diallable* symbol is a symbol which is to be dialled and appears on a telephone set to designate either a finger hole of a dial or a push button of a keyset<sup>2</sup>. These symbols can be digits, letters, or other signs. Some desirable properties to be considered when selecting diallable symbols are listed in Annex A.
+
+## 7 Procedural symbols
+
+A *procedural* symbol is a symbol which tells the subscriber how to dial. Such symbols should not appear in a finger hole or on a push button because they are not to be dialled.
+
+### 7.1 International prefix symbol
+
+The *international prefix symbol* should be + (plus) and should precede the country code in the international number. It serves to remind the subscriber to dial the international prefix which differs from country to country and also serves to identify the number following as the international telephone number.
+
+### 7.2 Use of parentheses
+
+The symbol ( ) (parentheses) should be used to indicate that the digits within the ( ) are not always dialled.
+
+The ( ) should enclose:
+
+- the trunk prefix and trunk code in a national number<sup>3</sup>;
+- the trunk code when the trunk prefix is not in universal use within a country.
+
+This is done to remind the user not to dial the enclosed digits for calls within the same numbering area.
+
+The ( ) should not be used in an international number.
+
+### 7.3 Multiple numbers reached through automatic search
+
+For a subscriber with multiple numbers reached through automatic search from the main number, only the main number should be printed, without any symbol to denote the existence of the multiple numbers. This avoids encouraging subscribers to dial other numbers in a group immediately after finding the main number busy, a problem that is particularly important when only calls to the main number are capable of triggering automatic search.
+
+---
+
+<sup>2</sup> Specific recommendations on the symbol for buttons 11 to 16 of a telephone keyset are contained in clause 3/E.161.
+
+<sup>3</sup> It should be noted that certain Administrations, for national purposes, use a hyphen between the trunk code and subscriber number as a substitute for the symbol ( ) parentheses in national numbers.
+
+### 7.4 Multiple numbers without automatic search
+
+For a subscriber with multiple numbers who does not have automatic search, the symbol / (oblique stroke, solidus, or slant) may be used to separate the alternative numbers.
+
+*Example A:* (0607) 123 4567 / 123 7272 / 627 1876  
+(0607) 123 4567 / 393 9844 / 564 1692  
++ 22 607 123 4567 / 393 9844
+
+To avoid dialling confusion in Example A, it is especially important that there be a space on either side of the symbol /.
+
+When it is desired to abbreviate the alternative numbers and they are consecutive, only the last digit should be shown for the alternative numbers.
+
+*Example B:* (0607) 123 4567 / 8 / 9
+
+To avoid dialling confusion in Example B, it is especially important that there be *no* space on either side of the symbol /.
+
+The general use of / is to indicate a choice when dialling. It may therefore also be used to indicate a choice of prefix codes as, for example, the choice of dialling personal or station calls.
+
+### 7.5 In-dialling
+
+In the national and international number no symbol should be used to show that a subscriber number is an in-dialling number of a PBX. Where it is desired to indicate the existence of in-dialling within a PBX and to indicate the in-dialling access code the following format is recommended:
+
+(0607) 123 ...  
+(0607) 1 23 4...
+
+The number of dots (periods) is equal to the number of digits in the extension number of the PBX. The spacing between numbers and dots should conform to national standards.
+
+On letterheads, subscribers could insert their own in-dialling numbers in the dotted spaces. Presentation of the main listed number should conform to 1.3 above.
+
+### 7.6 Symbol to indicate the existence of an additional dial tone<sup>4</sup>
+
+Some Administrations use one or more additional dial tone responses as procedural elements, after the calling customer obtains access to the public network. Where a symbol is needed to indicate the existence of an additional dial tone, that symbol should be the graphical representation of a full cycle of a sine wave, or a close approximation to such a representation. It should be placed at the point in the number where it is expected to occur, and it should be preceded and followed by a space to avoid confusion with a hyphen used as a spacing symbol (6.1). Its meaning is to tell the user to wait for the additional dial tone.
+
+*Example:* { Handwritten character: ![Handwritten sine wave symbol](cf907b6581366ac39ee91719072e5253_img.jpg)  
+Typewriter character "tilde": ~
+
+<sup>4</sup> In some countries, a horizontal line element (-), e.g. a hyphen in North America or a dash in some European countries, is used in national telephone numbers as a spacing character. Therefore, such an element is not available to designate an additional dial tone. Some Administrations, e.g. the Netherlands Administration, on the other hand, uses the dash to indicate an additional dial tone and foresees a continuation of this use for some time.
+
+**8 Information symbols**
+
+An information symbol is a symbol associated with the subscriber number describing special features of the subscriber telephone service, e.g. the symbol ⌕, where used, indicates that the subscriber has an answering device attached to his telephone (reference should be made to clause 2a) and b)/E.117).
+
+**8.1** Such symbols are not to be dialled and therefore should not appear in a finger hole or on a push button, nor can such symbols be procedural in instructing the subscriber how to dial.
+
+**8.2** Information symbols should be associated with the word "Telephone". To avoid confusion in dialling, they should not appear either as prefixes or suffixes to the telephone number.
+
+*Example:* Telephone (0607) 123 4567 or Telephone ⌕,  
+⌕, (0607) 123 4567
+
+See also the example below<sup>5</sup>.
+
+**9 Spacing symbols**
+
+Spacing symbols are symbols which are used solely to separate parts of a telephone number from each other. They cannot be diallable, procedural or information symbols.
+
+**9.1** Grouping of digits in a telephone number<sup>5</sup> should be accomplished by means or spaces<sup>6</sup> unless an agreed upon explicit symbol (e.g. hyphen) is necessary for procedural purposes. Only spaces should be used in an international number.
+
+**9.2** In the international number, spacing shall occur between the country code and the trunk code and between the trunk code and the subscriber number.
+
+**9.3** The major separation among digits in a telephone number (national or international) should occur between trunk code and subscriber number. This separation should therefore always be wider than any other separation within the number. This requirement is automatically met in the notation recommended, as in the examples<sup>5</sup>.
+
+**10 Facsimile number notation**
+
+The printed format for facsimile numbers should follow the conventions set forth for voice telephone numbers except that facsimile numbers should be clearly labelled with the uppercase letters FAX printed to the left of the numbers as illustrated here:
+
+|     |               |                 |
+|-----|---------------|-----------------|
+| FAX | National      | (06) 65 43 21   |
+|     | International | + 49 6 65 43 21 |
+
+The recommended appearance of the printed facsimile symbol (FAX) is specified in ITU-T E.121.
+
+<sup>5</sup> Some commonly used existing groupings are:
+
+|              |               |                |
+|--------------|---------------|----------------|
+| 📞            | National      | (0211) 5432    |
+|              | International | +39 211 5432   |
+| ⌕, Telephone | National      | (071) 78 901   |
+|              | International | +41 71 78 901  |
+| Telephone    | National      | (06) 65 43 21  |
+|              | International | +49 6 65 43 21 |
+
+<sup>6</sup> Administrations using dots or hyphens as separators nationally may require time to determine the consequences of discontinuing their use.
+
+**ITU-T E.123 (02/2001)**      5
+
+## ANNEX A
+
+### Desirable properties of diallable symbols
+
+This annex lists some desirable properties to be considered by the ITU-T when this body standardizes new diallable symbols. There are a large number of properties which are desirable for such symbols, and those indicated below seem particularly relevant. However, their relative importance has not been evaluated, and it is recognized that it may not always be possible to fulfil all these conditions when selecting symbols.
+
+The properties of diallable symbols should be:
+
+#### **A.1 Distinct from other diallable symbols**
+
+As used here, "distinct" refers to dissimilarity from other symbols compared with them visually, or aurally. The dissimilarity should be evident in low probability of confusion with other symbols under degraded perceptual conditions.
+
+**A.1.1** The symbols should be visually distinct in their designated form as well as in typewritten, handwritten, or printed form, including variations which might occur in each.
+
+**A.1.2** The symbols should be aurally distinct in naming them in at least the official languages of the ITU.
+
+#### **A.2 Widely known name**
+
+The name of the symbol should be as widely known as possible and be constant over as wide a range of population as possible.
+
+#### **A.3 Reproducible**
+
+The symbol should be easily reproducible in handwritten and typewritten form.
+
+#### **A.4 ITU-T-ISO compatible**
+
+The symbol should be one which is given as a member of the ITU-T Alphabet No. 5 and the ISO (International Organization for Standardization) standard code for information interchange.
+
+#### **A.5 Made up of a single character**
+
+The symbol should not be composed of more than one individually valid symbol; nor should more than one key operation on a typewriter, for example, be required to produce it.
+
+#### **A.6 Abstract**
+
+The symbol should not already have intrinsic meaning resulting from other specialized usage.
+
+#### **A.7 Immediately recognizable as a diallable character**
+
+The symbol should not be one which is used for procedural or information purposes.
+
+
+
+## SERIES OF ITU-T RECOMMENDATIONS
+
+|                 |                                                                                                                                |
+|-----------------|--------------------------------------------------------------------------------------------------------------------------------|
+| Series A        | Organization of the work of ITU-T                                                                                              |
+| Series B        | Means of expression: definitions, symbols, classification                                                                      |
+| Series C        | General telecommunication statistics                                                                                           |
+| Series D        | General tariff principles                                                                                                      |
+| <b>Series E</b> | <b>Overall network operation, telephone service, service operation and human factors</b>                                       |
+| Series F        | Non-telephone telecommunication services                                                                                       |
+| Series G        | Transmission systems and media, digital systems and networks                                                                   |
+| Series H        | Audiovisual and multimedia systems                                                                                             |
+| Series I        | Integrated services digital network                                                                                            |
+| Series J        | Cable networks and transmission of television, sound programme and other multimedia signals                                    |
+| Series K        | Protection against interference                                                                                                |
+| Series L        | Construction, installation and protection of cables and other elements of outside plant                                        |
+| Series M        | TMN and network maintenance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits |
+| Series N        | Maintenance: international sound programme and television transmission circuits                                                |
+| Series O        | Specifications of measuring equipment                                                                                          |
+| Series P        | Telephone transmission quality, telephone installations, local line networks                                                   |
+| Series Q        | Switching and signalling                                                                                                       |
+| Series R        | Telegraph transmission                                                                                                         |
+| Series S        | Telegraph services terminal equipment                                                                                          |
+| Series T        | Terminals for telematic services                                                                                               |
+| Series U        | Telegraph switching                                                                                                            |
+| Series V        | Data communication over the telephone network                                                                                  |
+| Series X        | Data networks and open system communications                                                                                   |
+| Series Y        | Global information infrastructure and Internet protocol aspects                                                                |
+| Series Z        | Languages and general software aspects for telecommunication systems                                                           |

marked/E/T-REC-E.124-198811-I_PDF-E/raw.md

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+
+
+![ITU logo](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg)
+
+The logo of the International Telecommunication Union (ITU) features the letters 'ITU' in a bold, sans-serif font, superimposed on a stylized globe with intersecting lines.
+
+ITU logo
+
+INTERNATIONAL TELECOMMUNICATION UNION
+
+**ITU-T**
+
+**E.124**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+**TELEPHONE NETWORK AND ISDN  
+OPERATION, NUMBERING, ROUTING  
+AND MOBILE SERVICE**
+
+---
+
+**DISCOURAGEMENT OF FRIVOLOUS  
+INTERNATIONAL CALLING TO UNASSIGNED  
+OR VACANT NUMBERS ANSWERED BY  
+RECORDED ANNOUNCEMENTS WITHOUT  
+CHARGE**
+
+**ITU-T Recommendation E.124**
+
+(Extract from the *Blue Book*)
+
+---
+
+# NOTES
+
+1 ITU-T Recommendation E.124 was published in Fascicle II.2 of the *Blue Book*. This file is an extract from the *Blue Book*. While the presentation and layout of the text might be slightly different from the *Blue Book* version, the contents of the file are identical to the *Blue Book* version and copyright conditions remain unchanged (see below).
+
+2 In this Recommendation, the expression “Administration” is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+# **DISCOURAGEMENT OF FRIVOLOUS INTERNATIONAL CALLING TO UNASSIGNED OR VACANT NUMBERS ANSWERED BY RECORDED ANNOUNCEMENTS WITHOUT CHARGE**
+
+## **1 Preamble**
+
+It sometimes happens that there is a severe outbreak of international calling to telephone numbers that answer with recorded announcements without charge. It seems that some subscribers make such calls merely for free amusement. Frivolous calling can occur unnoticed by an Administration unless it is deliberately looked for, and serious degradation of quality of service can result.
+
+This Recommendation concerns prevention and abatement of frivolous international calling.
+
+## **2 Monitoring**
+
+Administrations should be alert to changes in the rate of call completion, or in the rate of calls completed without charge, or in any other direct or indirect measures that could indicate the growth of a significant amount of frivolous calling<sup>1)</sup>. Direct investigation may be necessary to confirm the existence of this problem.
+
+### **3 Prevention<sup>2)</sup>**
+
+The following practices in one country may reduce the likelihood of becoming the destination for frivolous calls from another country:
+
+- limiting the number of cycles of an announcement;
+- disconnecting when the limit is reached;
+- offering no lengthy information without charge.
+
+## **4 Abatement**
+
+4.1 When frivolous calls can be identified as originating from the network of a particular Administration, the Administrations concerned should arrange bilaterally to implement the most appropriate prevention and abatement measures for the particular case. This bilateral arrangement may include measures not recommended for general application.
+
+4.2 In general, vacant subscriber number announcements should not be replaced by non-standard tones to reduce frivolous calling because the use of unfamiliar tones might cause increased repeat attempts by serious callers. Where particular numbers have been identified as the targets of frivolous callers, replacing announcements by tones for a limited period should not degrade the service for serious callers. For this purpose only, a special information tone is recommended.
+
+---
+
+1) The problem was first discovered in Japan after KDD noticed a large number of calls lasting longer than one minute without an answer signal being returned.
+
+2) Where the signalling systems permit, the use of a backward unallocated-number signal will allow an appropriate tone or announcement to be returned to the caller according to Recommendation E. 181, § 2.
+
+4.3 When frivolous calling has been identified as causing quality of service problems, it is desirable to detect the calls and direct them to an appropriate announcement as close to the calling subscriber as practicable. The administrative and technical difficulties of updating such arrangements for changes in many different numbering plans make the incoming international switching centre the practical limit in most cases. By bilateral agreement, however, frivolous calls might be blocked at the outgoing international switching centre instead.
+
+4.4 In accordance with Recommendation E. 231, no charge should be made for calls to subscribers whose service has been suspended, cancelled or transferred. When calls to certain of these out-of-use numbers have been identified as predominantly frivolous, the provisions of Recommendation E. 231 may be temporarily ignored for only the particular numbers involved, until the problem is abated<sup>3)</sup>, and subject to the agreement of the Administrations concerned. Calls to these numbers would then have an answer signal returned and would be charged<sup>4)</sup>. Calls to unassigned numbers may be handled similarly. This measure would be immediately effective when frivolous calls originate from payphones.
+
+---
+
+3) Administrations should take care not to apply this measure to non-frivolous telephone calls.
+
+4) Some exchanges may require the addition of a function to handle such calls in this manner.

marked/E/T-REC-E.131-198811-I_PDF-E/raw.md

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+
+
+![ITU logo](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg)
+
+The logo of the International Telecommunication Union (ITU) features a globe with a lightning bolt superimposed on it, and the letters 'ITU' in a bold, sans-serif font.
+
+ITU logo
+
+INTERNATIONAL TELECOMMUNICATION UNION
+
+**ITU-T**
+
+**E.131**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+**TELEPHONE NETWORK AND ISDN**
+
+**OPERATION, NUMBERING, ROUTING  
+AND MOBILE SERVICE**
+
+---
+
+**SUBSCRIBER CONTROL PROCEDURES FOR  
+SUPPLEMENTARY TELEPHONE SERVICES**
+
+**ITU-T Recommendation E.131**
+
+(Extract from the *Blue Book*)
+
+---
+
+# NOTES
+
+1 ITU-T Recommendation E.131 was published in Fascicle II.2 of the *Blue Book*. This file is an extract from the *Blue Book*. While the presentation and layout of the text might be slightly different from the *Blue Book* version, the contents of the file are identical to the *Blue Book* version and copyright conditions remain unchanged (see below).
+
+2 In this Recommendation, the expression “Administration” is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+# **SUBSCRIBER CONTROL PROCEDURES FOR SUPPLEMENTARY TELEPHONE SERVICES**
+
+## **1 General**
+
+1.1 Many Administrations are planning to introduce supplementary telephone services which are likely to be viable only if controlled by the user (a list of possible supplementary telephone services is given in Supplement No. 1 at the end of this fascicle). It is therefore necessary to consider means of providing users with procedures by which such control can be achieved. The purpose of this Recommendation is to prevent an undesirable proliferation, in various countries, of subscriber control procedures for such services. Descriptions are given below of three control procedures schemes now in use or in various stages of evolution. Guidelines are offered to Administrations planning to offer subscriber controlled supplementary services. Reference is made to Annex A for a glossary of terms used in this Recommendation.
+
+1.2 It is recognized that not all aspects of all supplementary services will affect the international telephone service, but a degree of international coordination is considered necessary because:
+
+- a) the same or similar supplementary services will exist on national and international networks; it is desirable to have similar control procedures for both applications;
+- b) a supplementary service which is only national now may be international in the future; in that case changes in control procedures might be impossible or expensive;
+- c) subscribers who travel or move will be less inconvenienced if control procedures for supplementary services do not change from one country to another;
+- d) compatibility between control procedures for telephone services and simple parallel end-to-end data transmission is highly desirable, because the same telephone instrument is used in both cases;
+- e) standardized control procedures make possible lower equipment and customer instruction costs.
+
+1.3 Access to individual services requires that the supplementary service numbering plan have a sufficient capacity to meet all reasonable future needs; control of the services requires the ability to define functional requirements to the system.
+
+The introduction of push-button telephones providing signals in addition to the normal decimal range (0-9) offers a means of providing the necessary function signals. Since the 12-button instrument is likely to be used by most subscribers, only two additional non-numerical signals will be available for control purposes. Study therefore has been directed towards evolving schemes for control procedures which are acceptable both from the human factors and technical aspects and do not require more than two non-numerical signals.
+
+1.4 The same push-button telephone set that is used in dedicated telephone networks may be used as a subscriber instrument in service integrated networks. It is desirable that in this case the control procedures for a given supplementary telephone service still apply.
+
+Where the normal 12-button telephone set is also used for services other than telephony, e.g. for data, video-telephone, etc., the control procedures used for these services should be compatible with the control procedures used for supplementary telephone services.
+
+## **2 Schemes for control procedures**
+
+Recognizing that:
+
+- the CCITT has not as yet recommended a unique scheme of subscriber control procedures for supplementary telephone services;
+- the CCITT is still studying such control procedures;
+- further proliferation of schemes is undesirable because this would result in subscriber confusion, less efficient use of the telephone network and might make it more difficult to work towards an optimum scheme;
+
+it is recommended that:
+
+- Administrations contemplating the introduction of services which require new control procedures join actively with the ongoing study;
+- Administrations wishing to adopt a scheme of subscriber control procedures should apply one of those detailed below to the maximum extent feasible rather than establish a new scheme.
+
+## **3 Description and analysis of code schemes for supplementary telephone services**
+
+### **3.1 General**
+
+3.1.1 Three code schemes for supplementary telephone services, currently in use or under study will be briefly described and analyzed. They are:
+
+- 1) AT&T code scheme (USA);
+- 2) CEPT code scheme (Europe);
+- 3) NTT code scheme (Japan).
+
+3.1.2 It is intended that Recommendation E.131 should be reviewed when experience of the three code schemes is available. It may then be possible to determine if one of them, or perhaps a fourth which incorporates the best features of all three, is to be preferred.
+
+3.1.3 These schemes are still evolving and are liable to changes in details as study progresses or experience is gained. The information presented is an outline only and presents the position at a point in time when the Recommendation is published. Administrations considering the implementation of supplementary services requiring control procedures should approach the appropriate Administration or authority to seek detailed and up-to-date information.
+
+### **3.2 Description of the code schemes**
+
+3.2.1 The information sent by the subscriber to the exchange for the control of a service is made up of a number of basic functional elements, some or all of which may appear explicitly in a particular message. These basic functional elements are (see the glossary in Annex A):
+
+- 1) mode or type of communication identification,
+- 2) access to supplementary services,
+- 3) service identification,
+- 4) function identification,
+- 5) supplementary information,
+- 6) block separation,
+- 7) message suffix.
+
+3.2.2 The mode or type of communication identification element is unlikely to be used for telephone services and allocation of codes for this purpose within these schemes is tentative. This element is therefore excluded from consideration for the present.
+
+3.2.3 The main differences between the three code schemes are in the methods used to encode the various functional elements and the order in which they must be presented. In all code schemes a separate code is used for the dialling of abbreviated numbers.
+
+3.2.4 For each of the three code schemes, Table 1/E.131 gives the format of the information sent by the subscriber to the exchange:
+
+- i) without supplementary information,
+- ii) with one block of supplementary information,
+- iii) for the dialling of abbreviated numbers.
+
+In the Table 1/E.131, the digits below each message identify the functional elements as listed in § 3.2.1 above.
+
+TABLE 1/E.131
+
+#### *AT&T*
+
+|                                |         |         |     |    |     |
+|--------------------------------|---------|---------|-----|----|-----|
+| i) Information<br>Element No.  | * or 11 | NN      |     |    |     |
+|                                | 2       | 3 and 4 |     |    |     |
+| ii) Information<br>Element No. | * or 11 | NN      | SDT | SI | (#) |
+|                                | 2 and 4 | 3 and 4 |     | 5  | 7   |
+| iii) Abbreviated dialing       | N(N)    | (#)     |     |    |     |
+
+#### *CEPT*
+
+|                                 |             |           |          |    |   |
+|---------------------------------|-------------|-----------|----------|----|---|
+| i) Information<br>Element No.   | * or #      | NN(N)     | #        |    |   |
+|                                 | 2 and 4     | 3         | 7        |    |   |
+| ii) Information<br>Element No.  | * or #      | NN(N)     | * $\phi$ | SI | # |
+|                                 | 2 and 4     | 3         | 6        | 5  | 7 |
+| iii) Abbreviated dialling<br>or | N(N)<br>* * | #<br>N(N) |          |    |   |
+
+#### *NTT*
+
+|                                |        |    |         |     |    |     |
+|--------------------------------|--------|----|---------|-----|----|-----|
+| i) Information<br>Element No.  | 1 or # | NN | (SDT N) | (#) |    |     |
+|                                | 2      | 3  | 4       | 7   |    |     |
+| ii) Information<br>Element No. | 1 or # | NN | (SDT N) | (*) | SI | (#) |
+|                                | 2      | 3  | 4       | 6   | 5  | 7   |
+| iii) Abbreviated dialing       | *      | NN |         |     |    |     |
+
+For  $\phi$ , see § 3.2.5 (element 6, CEPT).
+
+The symbols used in Table 1/E.131 are as follows:
+
+|       |   |                                                                      |
+|-------|---|----------------------------------------------------------------------|
+| N     | = | a digit;                                                             |
+| SI    | = | supplementary information;                                           |
+| SDT   | = | second dial tone;                                                    |
+| (...) | = | not always used. For detailed explanations, see § 3.2.5 below;       |
+| *     | = | “star” button of telephone set as defined in Recommendation E.161;   |
+| #     | = | “square” button of telephone set as defined in Recommendation E.161. |
+
+3.2.5 In the three code schemes the basic functional elements are realized in the following way:
+
+*Access to supplementary services (element 2)*
+
+AT&T: access prefix \*. (Customers are permitted to dial the digits 11 in place of \*.)
+
+CEPT: service code prefix \* or #.
+
+NTT: prefix digit 1 for services available from both dial and push-button telephones, prefix # for services available from push-button telephones only.
+
+#### *Service identification (element 3)*
+
+AT&T: a two-digit service code that is also used to indicate the function: codes 72-79.
+
+CEPT: two-digit (or exceptionally, three digit) service codes beginning with 1-9 and 0 are reserved for CEPT allocation in both PABX and public exchange fields.
+
+NTT: two-digit service codes.
+
+#### *Function identification (element 4)*
+
+AT&T: the function is expressed in the service code, different functions for the same service use consecutive codes.
+
+CEPT: service code prefix \*: activation and registration;  
+service code prefix #: deactivation and erasure.
+
+NTT: a numerical function code that is only required for certain services. (If a function code is needed, the subscriber is informed by means of a dial tone).
+
+0 = deactivation,
+
+1 = activation,
+
+2 = registration.
+
+#### *Block separation (element 6)*
+
+AT&T: no block separation required.
+
+CEPT: the standard CEPT control procedure will assume the use of a block separator \* after the service code and between blocks of supplementary information. As a national option, the deletion of the block separator after the service code is allowed; however, if in this case the subscriber dials a block separator after the service code, the exchange should accept the message.
+
+NTT: the block separator \* may be used between the function code and the first block of supplementary information, and between successive blocks of supplementary information for push-button telephones only.
+
+#### *Message suffix (element 7)*
+
+AT&T: the message suffix # may be replaced by a time-out.
+
+CEPT: the message suffix # is mandatory.
+
+NTT: the message suffix # is used for push-button telephones only.
+
+#### *Abbreviated dialling*
+
+AT&T: abbreviated numbers: 2-9 and 20-49 available.
+
+CEPT: N(N) # abbreviated numbers: 0-9 and 00-99 available;  
+\*\*N(N) abbreviated numbers: 0-9 or 00-99 available.
+
+NTT: abbreviated numbers: 00-99 available.
+
+### 3.3 Features of each of the code schemes
+
+The features of each of the code schemes compared with one or both of the other two are given below.
+
+#### 3.3.1 AT&T code scheme
+
+- 1) The \* symbol is used for access to supplementary services.
+
+- 2) Control procedures from rotary dial and push-button telephones are compatible.
+- 3) The messages sent by the subscriber to the exchange are short.
+- 4) Some two-digit codes have been reserved so as to permit three- digit (or longer) service codes to be introduced in the future without changes in the existing service codes.
+- 5) The message suffix is not essential.
+- 6) One, two and more digit abbreviated numbers are possible without the need to use different initial digits.
+
+#### 3.3.2 *CEPT code scheme*
+
+- 1) When only prefixes are used, the telephone numbering plan is not influenced by the code scheme for supplementary services.
+- 2) When only prefixes are used, exchange logic is simplified.
+- 3) When only prefixes are used, the use of similar control procedures in PABXs and the public network is facilitated.
+- 4) The abbreviated dialling numbering plan is divorced from the service code numbering plan and does not impose restrictions on it.
+- 5) The service code remains the same irrespective of the function required.
+- 6) Each important function is defined by a unique prefix.
+- 7) Other prefixes are available for new service functions.
+- 8) A mandatory message suffix avoids the need for time-out, fixed message length or complex programming.
+- 9) When the message suffix method for abbreviated dialling is used, one, two and more digit abbreviated numbers are possible without the need to use different initial digits.
+
+#### 3.3.3 *NTT code scheme*
+
+- 1) The use of a prefix simplifies exchange logic.
+- 2) The use of a prefix facilitates the use of similar control procedures in PABXs and the public network.
+- 3) Other prefixes are available for future use.
+- 4) A measure of compatibility between the control procedures from rotary dial and push-button telephones is possible.
+- 5) The abbreviated dialling numbering plan is divorced from the service code numbering plan and does not impose restrictions on it.
+- 6) The service code remains the same irrespective of the function required.
+- 7) Each important function is defined by a unique function code.
+- 8) Ten function codes are available.
+- 9) Allocating a function code after a service code makes it possible to separate basic switching functions from supplementary service processing functions. This facilitates the application of new services to an existing old-type exchange.
+- 10) The control procedures are similar to the control procedures in the NTT end-to-end communication services.
+- 11) The function code can be deleted if not required.
+
+## ANNEX A
+
+(to Recommendation E.131)
+
+### Glossary of terms
+
+This glossary gives the meanings currently allocated to various terms to facilitate the study and evaluation of control procedures. They are subject to review as the code schemes evolve.
+
+### A.1 **supplementary telephone service**
+
+*F: service téléphonique supplémentaire*
+
+*S: servicio telefónico suplementario*
+
+Any service provided by the telephone network in addition to the fundamental telephone service.
+
+### A.2 **control procedure**
+
+*F: procédure de commande*
+
+*S: procedimiento de control*
+
+A method in which information is exchanged in a predetermined forward order and backward order between subscriber and exchange to effect control of a service.
+
+### A.3 **command**
+
+*F: commande*
+
+*S: instrucción (de control)*
+
+A single specific manipulation at the subscriber set causing transmission of a signal which specifically indicates the manipulation to the exchange. For certain control procedures either one single command or a succession of commands are required.
+
+### A.4 **character**
+
+*F: caractère*
+
+*S: carácter*
+
+A single specific symbol, number or letter used to designate the diallable signal caused by a command.
+
+### A.5 **message**
+
+*F: message*
+
+*S: mensaje*
+
+A defined entity of information from the subscriber to the exchange pertaining to a call or a control operation for a service sent in one sequence over the signalling medium. A message may consist of one or more characters transmitted in one or more blocks.
+
+### A.6 **code**
+
+*F: code*
+
+*S: código*
+
+One character or a sequence of characters forming a part, or the whole, of a message with a specific meaning.
+
+### A.7 **mode or type of communication identification**
+
+*F: identification du type ou du mode de la communication*
+
+*S: identificación del tipo o del modo de la comunicación*
+
+Information used to give an instruction to the switching equipment to select the required network or mode of communication, for example in the use of a multifunction terminal (video-telephone, 48 kbit/s wideband switched-network service, etc.).
+
+### **A.8 access to supplementary services**
+
+*F: accès aux services supplémentaires*
+
+*S: acceso a servicios suplementarios*
+
+Information used to instruct the switching equipment that the associated information relates to a supplementary service.
+
+### **A.9 service identification**
+
+*F: identification de service*
+
+*S: identificación de servicio*
+
+Information designating a supplementary service.
+
+### **A.10 function identification**
+
+*F: identification de fonction*
+
+*S: identificación de función*
+
+Information indicating the type or types of process to be applied to the service.
+
+### **A.11 block separation**
+
+*F: séparation des blocs*
+
+*S: separación de bloques*
+
+Information indicating that the next character is the first character of a block of supplementary information.
+
+### **A.12 supplementary information**
+
+*F: information supplémentaire*
+
+*S: información suplementaria*
+
+Any information, except the mode or type of communication identification, access to supplementary services, service identification, function identification, block separation and message suffix, which is required to be sent by the subscriber to the exchange for the performance of a control operation. The supplementary information may consist of one or more blocks.
+
+### **A.13 service code**
+
+*F: code de service*
+
+*S: código de servicio*
+
+A numerical code designating a supplementary service.
+
+### **A.14 service code prefix**
+
+*F: préfixe de code de service*
+
+*S: prefijo de código de servicio*
+
+A non-numerical code preceding the service code and indicating the type or types of process to be applied to the service.
+
+### A.15 **function code**
+
+*F: code de fonction*
+
+*S: código de función*
+
+A code indicating the type or types of process to be applied to the service.
+
+### A.16 **block separator**
+
+*F: séparateur de blocs*
+
+*S: separador de bloques*
+
+The character indicating that the next character is the first of a block of supplementary information.
+
+### A.17 **message suffix**
+
+*F: suffixe de message*
+
+*S: sufijo de mensaje*
+
+The character indicating the end of the message.
+
+### A.18 **abbreviated number**
+
+*F: numéro abrégé*
+
+*S: número abreviado*
+
+The numerical code sent by a caller using the Abbreviated Dialling Service which identifies the telephone number of the party to whom he wishes to be connected.
+
+### A.19 **abbreviated dialling prefix**
+
+*F: préfixe de numérotation abrégée*
+
+*S: prefijo de marcación abreviada*
+
+The non-numerical code indicating that the information following is an abbreviated number.
+
+## ANNEX B
+
+(to Recommendation E.131)
+
+During the Study Period 1977-80, an international laboratory experiment comparing subscriber performance using two of the recommended code schemes and a previous code scheme of AT&T, which was defined in Volume II.2 of the *Orange Book*, was carried out under the auspices of Working Party II/2 (Human Factors). The experiment was conducted in five countries, Canada, Japan, Sweden, the United Kingdom and the United States of America. In the experiment, a sample of subscribers were brought into the laboratory and asked to carry out a number of tasks involving the use of three supplementary services. These tasks were carried out using a pushbutton telephone connected to a simulated telephone exchange. A different group of subscribers was tested using each of the code schemes. Errors committed while carrying out the tasks and the time required to complete them were recorded.
+
+The results of this experiment revealed that there are no large differences in subscriber performance using the three code schemes. The experimental results did, however, reveal rather large differences among tasks. Those tasks that required entry of supplementary information blocks produced higher error rates. This suggests that guidance announcements may be required to help subscribers at each step in complex control procedures. However, it should be pointed out that prior to carrying out the tasks only a brief explanation of the required manipulations was given. It would be desirable for experienced users to be able to override guidance announcements by dialling. One particular task, ordering an alarm call, produced quite high error rates in the entry of the time of day. These errors resulted from the use of a 24 hours clock format for entry of this information. This result suggests that a specific positive recorded announcement with supplementary information may be required to give the subscriber feedback on this point.

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+
+
+![ITU logo](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg)
+
+The logo of the International Telecommunication Union (ITU) features the letters 'ITU' in a bold, sans-serif font, superimposed on a stylized globe with intersecting lines.
+
+ITU logo
+
+INTERNATIONAL TELECOMMUNICATION UNION
+
+**ITU-T**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+**E.138**
+
+(06/2002)
+
+SERIES E: OVERALL NETWORK OPERATION,  
+TELEPHONE SERVICE, SERVICE OPERATION AND  
+HUMAN FACTORS
+
+International operation – General provisions concerning  
+users
+
+---
+
+**Human factors aspects of public telephones to  
+improve their usability for older people**
+
+ITU-T Recommendation E.138
+
+---
+
+# ITU-T E-SERIES RECOMMENDATIONS
+
+# OVERALL NETWORK OPERATION, TELEPHONE SERVICE, SERVICE OPERATION AND HUMAN FACTORS
+
+|                                                                                                   |                    |
+|---------------------------------------------------------------------------------------------------|--------------------|
+| INTERNATIONAL OPERATION                                                                           |                    |
+| Definitions                                                                                       | E.100–E.103        |
+| General provisions concerning Administrations                                                     | E.104–E.119        |
+| <b>General provisions concerning users</b>                                                        | <b>E.120–E.139</b> |
+| Operation of international telephone services                                                     | E.140–E.159        |
+| Numbering plan of the international telephone service                                             | E.160–E.169        |
+| International routing plan                                                                        | E.170–E.179        |
+| Tones in national signalling systems                                                              | E.180–E.189        |
+| Numbering plan of the international telephone service                                             | E.190–E.199        |
+| Maritime mobile service and public land mobile service                                            | E.200–E.229        |
+| OPERATIONAL PROVISIONS RELATING TO CHARGING AND ACCOUNTING IN THE INTERNATIONAL TELEPHONE SERVICE |                    |
+| Charging in the international telephone service                                                   | E.230–E.249        |
+| Measuring and recording call durations for accounting purposes                                    | E.260–E.269        |
+| UTILIZATION OF THE INTERNATIONAL TELEPHONE NETWORK FOR NON-TELEPHONY APPLICATIONS                 |                    |
+| General                                                                                           | E.300–E.319        |
+| Phototelegraphy                                                                                   | E.320–E.329        |
+| ISDN PROVISIONS CONCERNING USERS                                                                  | E.330–E.349        |
+| INTERNATIONAL ROUTING PLAN                                                                        | E.350–E.399        |
+| NETWORK MANAGEMENT                                                                                |                    |
+| International service statistics                                                                  | E.400–E.409        |
+| International network management                                                                  | E.410–E.419        |
+| Checking the quality of the international telephone service                                       | E.420–E.489        |
+| TRAFFIC ENGINEERING                                                                               |                    |
+| Measurement and recording of traffic                                                              | E.490–E.505        |
+| Forecasting of traffic                                                                            | E.506–E.509        |
+| Determination of the number of circuits in manual operation                                       | E.510–E.519        |
+| Determination of the number of circuits in automatic and semi-automatic operation                 | E.520–E.539        |
+| Grade of service                                                                                  | E.540–E.599        |
+| Definitions                                                                                       | E.600–E.649        |
+| Traffic engineering for IP-networks                                                               | E.650–E.699        |
+| ISDN traffic engineering                                                                          | E.700–E.749        |
+| Mobile network traffic engineering                                                                | E.750–E.799        |
+| QUALITY OF TELECOMMUNICATION SERVICES: CONCEPTS, MODELS, OBJECTIVES AND DEPENDABILITY PLANNING    |                    |
+| Terms and definitions related to the quality of telecommunication services                        | E.800–E.809        |
+| Models for telecommunication services                                                             | E.810–E.844        |
+| Objectives for quality of service and related concepts of telecommunication services              | E.845–E.859        |
+| Use of quality of service objectives for planning of telecommunication networks                   | E.860–E.879        |
+| Field data collection and evaluation on the performance of equipment, networks and services       | E.880–E.899        |
+
+For further details, please refer to the list of ITU-T Recommendations.
+
+# **ITU-T Recommendation E.138**
+
+# **Human factors aspects of public telephones to improve their usability for older people**
+
+## **Summary**
+
+This Recommendation contains guidelines for the design of public telephone terminals for voice communication to make them more usable for older people, whose sensory, cognitive and motor functions may have deteriorated. "Public telephones" include all telephones that are not in private offices or households, but that are generally accessible to many people. These guidelines are derived from the requirements of older people that can be identified for each of the steps connected to using a public telecommunication terminal: locating it; initiating a call; providing payment; identifying oneself and the communication counterpart; actually communicating; possibly setting up a further call; terminating the communication.
+
+###### **Source**
+
+ITU-T Recommendation E.138 was prepared by ITU-T Study Group 2 (2001-2004) and approved under the WTSA Resolution 1 procedure on 29 June 2002.
+
+## FOREWORD
+
+The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis.
+
+The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics.
+
+The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1.
+
+In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC.
+
+### NOTE
+
+In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+### INTELLECTUAL PROPERTY RIGHTS
+
+ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process.
+
+As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database.
+
+© ITU 2002
+
+All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU.
+
+## CONTENTS
+
+###### Page
+
+|      |                                                                                             |    |
+|------|---------------------------------------------------------------------------------------------|----|
+| 1    | Scope .....                                                                                 | 1  |
+| 2    | References.....                                                                             | 1  |
+| 3    | Terms and definitions .....                                                                 | 2  |
+| 4    | Abbreviations.....                                                                          | 2  |
+| 5    | Characteristics of older people .....                                                       | 3  |
+| 6    | Organization of this Recommendation .....                                                   | 5  |
+| 7    | Locating and accessing a telephone: Visual requirements .....                               | 6  |
+| 7.1  | Terminal identification signs .....                                                         | 6  |
+| 7.2  | Lighting .....                                                                              | 6  |
+| 7.3  | Operating instructions .....                                                                | 6  |
+| 7.4  | Information displays and visual indicators.....                                             | 8  |
+| 8    | Locating and accessing a telephone: Hearing requirements.....                               | 9  |
+| 9    | Locating and accessing a telephone: Strength, mobility and dexterity requirements...        | 9  |
+| 9.1  | Space surrounding the telephone.....                                                        | 9  |
+| 9.2  | Area immediately around the telephone.....                                                  | 9  |
+| 10   | Initialization step: Call set-up: Visual, tactile and dexterity requirements.....           | 10 |
+| 10.1 | Keypads .....                                                                               | 10 |
+| 11   | Initialization step – Call set-up: Hearing requirements .....                               | 11 |
+| 12   | Initialization step – Call set-up: Cognitive requirements .....                             | 12 |
+| 13   | Initialization step – Call set-up: Mobility requirements .....                              | 12 |
+| 14   | Initialization step – Payment: Visual requirements .....                                    | 12 |
+| 14.1 | Cards.....                                                                                  | 12 |
+| 15   | Initialization step – Payment: Hearing requirements.....                                    | 13 |
+| 16   | Initialization step – Payment: Tactile, strength, mobility and dexterity requirements ..... | 13 |
+| 16.1 | Location of coin, card and token slots.....                                                 | 13 |
+| 16.2 | Cards to be inserted .....                                                                  | 13 |
+| 16.3 | Cards to be swiped.....                                                                     | 13 |
+| 17   | Communication step: Tactile, strength, mobility and dexterity requirements .....            | 13 |
+| 17.1 | The cord connecting handset and terminal .....                                              | 13 |
+| 17.2 | The handset: location, weight and shape.....                                                | 14 |
+
+|                                                                                                                 | Page |
+|-----------------------------------------------------------------------------------------------------------------|------|
+| 17.3 Hands-free operation .....                                                                                 | 14   |
+| 18 Communication phase .....                                                                                    | 14   |
+| 18.1 Mildly hard of hearing (some high frequency loss) .....                                                    | 14   |
+| 18.2 Moderately hard of hearing (significant loss of high frequencies and some loss of middle frequencies)..... | 14   |
+| 18.3 Severe hearing loss (significant loss of high and middle frequencies) .....                                | 15   |
+| 18.4 Profoundly deaf (cannot use hearing for any form of verbal communication).....                             | 15   |
+| 19 Next call (follow-on call): Visual, tactile, strength, mobility and dexterity requirements .....             | 15   |
+| 19.1 Redial.....                                                                                                | 16   |
+| 19.2 New number call.....                                                                                       | 16   |
+| 20 Terminate call: Visual requirements.....                                                                     | 16   |
+| 20.1 Receipts .....                                                                                             | 16   |
+| 21 Terminate call: Hearing requirements .....                                                                   | 16   |
+| 22 Terminate call: Tactile, strength, mobility and dexterity requirements.....                                  | 16   |
+| 22.1 Retrieving remaining coins.....                                                                            | 16   |
+| 22.2 Card retrieval.....                                                                                        | 16   |
+| 23 Bibliography .....                                                                                           | 17   |
+
+## Introduction
+
+Throughout the Western world, as well as in parts of Asia, life expectancy has changed significantly during the 20th century [Dall, 1992]; [Collins *et al.*, 1992]. Not only are more people getting older, they also tend to be better educated and in better health than their forbears, which means that they lead much longer active lives. This activity includes the use of telecommunication facilities. But, many older people find it difficult to use many of today's telephones, and other telecommunication terminals. This is because sensory, cognitive and motor faculties deteriorate with advancing age. Such reductions in severe cases lead to impairments or even disabilities, but it would be misleading to equate older people with disabled people – although this is often done. In fact, provided that proper measures are taken, the majority of older users of telecommunications need not experience serious hindrances. It is important to society as a whole to enable older people to remain active as long as possible, and to participate in activities such as travelling and to communicate via public telecommunication terminals [Collins *et al.*, 1992]. This means that available data on changes in human faculties with progressing age must be taken into account. Missing information in this field must be compiled through appropriate research [Garbe *et al.*, 1992]. It should be realized that any adaptations of public telephones that increase their usability for older people, such as larger font size and higher contrast on visual displays, will normally also benefit younger users [Blaich, 1992].
+
+# **Human factors aspects of public telephones to improve their usability for older people**
+
+## **1 Scope**
+
+This Recommendation proposes guidelines for the design of public telephone terminals for voice communication to make them simpler to use for older people whose sight, hearing, information processing and motor functions have deteriorated. This Recommendation provides information on the requirements of older people and how telephones can be adapted for their use. This Recommendation addresses manufacturers, designers, procurers, network operators, regulatory authorities, and those who deploy telecommunication terminals intended for general (public) use. In this Recommendation the term '*public telephone*' shall include all telephones that are not in private offices or households, but that are generally accessible to many people, for instance, public payphones, telephones for general use in hotels, airports, hospitals, shopping malls, universities, schools, official agencies, etc.
+
+This Recommendation is regarded as necessary, next to the already-existing ITU-T Rec. E.135: Human factors aspects of public telecommunication terminals for people with disabilities, because:
+
+- i) although older people are frequently associated with the disabled in literature and general opinion, this is incorrect and misleading in terms of specific user requirements;
+- ii) by ITU-T Rec. E.138's restriction to public telephones, as opposed to public terminals, its scope in this respect may seem to be narrower than that of ITU-T Rec. E.135, but on the other hand is wider because all types of 'public places' such as hotels, airports, hospitals and shopping malls are included, with the available telephones that are there.
+
+It is of interest to everybody involved in the telecommunication business to be informed about the relation between their products and the needs of an ever-increasing proportion of their customers, i.e., older people.
+
+## **2 References**
+
+The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation.
+
+- ITU-T Recommendation E.121 (1996), *Pictograms, symbols and icons to assist users of the telephone*.
+- ITU-T Recommendation E.134 (1993), *Human factors aspects of public terminals: Generic operating procedures*.
+- ITU-T Recommendation E.135 (1995), *Human factors aspects of public telecommunication terminals for people with disabilities*.
+- ITU-T Recommendation E.136 (1997), *Specification of a tactile identifier for use with telecommunication cards*.
+- ITU-T Recommendation E.137 (1997), *User instructions for payphones*.
+
+- ITU-T Recommendation E.161 (2001), *Arrangement of digits, letters and symbols on telephones and other devices that can be used for gaining access to a telephone network.*
+- ITU-T Recommendation E.180/Q.35 (1998), *Technical characteristics of tones for the telephone service.*
+- ITU-T Recommendation F.901 (1993), *Usability evaluation of telecommunication services.*
+- ITU-T Recommendation P.370 (1996), *Coupling of hearing aids to telephone sets.*
+- ITU-T Recommendation V.18 (2000), *Operational and interworking requirements for DCEs operating in the text telephone mode.*
+- ISO 13406-2:2001, *Ergonomic requirements for work with visual displays based on flat panels – Part 2: Ergonomic requirements for flat panel displays.*
+- EN 1332-4, *Machine-readable cards, related device interfaces, and operations. Part 4: Coding of user requirements for people with special needs.*
+- ETSI EN 301 462 (2000), *Human Factors (HF); Symbols to identify telecommunications facilities for deaf and hard of hearing people.*
+- JIS S 0012:2000, *Guidelines for all people including older people and people with disabilities – Usability of consumer products.*
+
+## 3 Terms and definitions
+
+This Recommendation defines the following terms:
+
+**3.1 older people:** This term has succeeded 'the elderly' and equally should be understood in a broad sense. 'Older people' are often, but by no means always, characterized by deterioration of their sensory, cognitive and motor facilities.
+
+**3.2 public telephones:** This term shall include all telephones that are not in private offices or households, but that are generally accessible to many people, for instance, public payphones, telephones for general use in hotels, airports, hospitals, shopping malls, universities, schools, official agencies, etc.
+
+## 4 Abbreviations
+
+This Recommendation uses the following abbreviations:
+
+|      |                                                                                    |
+|------|------------------------------------------------------------------------------------|
+| CEN  | Comité Européen de Normalisation ( <i>European Committee for Standardization</i> ) |
+| EN   | European Norm                                                                      |
+| ES   | European Standard                                                                  |
+| ETR  | ETSI Technical Report                                                              |
+| ETS  | European Technical Standard                                                        |
+| ETSI | European Telecommunications Standards Institute                                    |
+| ISO  | International Organization for Standardization                                     |
+| LCD  | Liquid Crystal Display                                                             |
+| LED  | Light-Emitting Diode                                                               |
+| lux  | Unit of illumination strength                                                      |
+| N    | Newton (the SI unit for force, and weight)                                         |
+| PIN  | Personal Identification Number                                                     |
+
+point            Typographical unit of character font size; 1 point = 0.376 mm
+
+SI               Système International d'Unités (*International System Of Units*)
+
+## 5            Characteristics of older people
+
+Older people may suffer to varying degrees from any of the following impairments or from any combination thereof (based on [Gill, 1997]):
+
+- **Visual impairments.** Blindness implies a total or near total loss of the ability to perceive form visually. Low vision implies an ability to utilize some aspects of visual perception, but with a greater dependency on information received from other senses. For everybody, near visual acuity starts to diminish around age 40, and continues to do so through the 50s and 60s (presbyopia). Other visual impairments arise in older people, including cataracts, clouding of the optical media, glaucoma, macular degeneration and retinopathy as a result of diabetes.
+
+The use of colours to identify various functions or services may confuse older people. As vision deteriorates with age, so does colour perception. Bear also in mind that at least 7% of all males are colour-blind (protanopes and deuteranopes) and at least another 7% of all males are colour anomalous (protanomalous and deuteranomalous) to some degree. Less than 1% of women are colour-blind or colour-anomalous. Colour should therefore never be used alone to identify any function, but always in addition to some other information (the principle of redundancy).
+
+- **Hearing impairments.** The sense of hearing starts to deteriorate early in life and this continues throughout life, slowly at first, but faster in old age. However, hearing in older people may deteriorate at very different rates. One must not make the fallacy of perpetuating the popular myth that all older people are hard of hearing – the deterioration rate may vary significantly and some 80-year-olds may actually have better hearing than some 50-year-olds. The most typical characteristic of old-age hearing impairment is the continuous loss of high frequencies, eventually spreading downwards to the middle frequencies and sometimes afflicting the lower frequencies. The hearing losses may vary from slightly hard of hearing (some high frequency loss) to profoundly deaf. A second type of effect is that a significant, but as yet undefined number of older people have decreased ability to tune out background noise and thus have more difficulty hearing in noisy settings than younger people with otherwise comparable hearing ability [ETSI ETR 334, 1996]. This can be a significant factor in choosing a site for a public phone. In addition to any practical problems caused by a hearing disorder, a hearing loss first and foremost obstructs interpersonal speech communication, both face-to-face and over the telephone. To compensate for different degrees of hearing loss, various changes in telephone terminals should be implemented according to the severity of the hearing impairment. These actions are listed below under each call procedure.
+
+Hearing impairment can affect the whole range or only part of the auditory spectrum of which, for speech perception, the important region is between 250 and 4000 Hz – which, more or less, corresponds to the regular telephone bandwidth of 300 to 3400 Hz. The term "deaf" is used to describe people with profound hearing loss such that they cannot benefit from amplification, while "hard of hearing" is used for those with mild to severe hearing loss but who can benefit from amplification.
+
+- **Cognitive impairments.** What we sometimes call 'intelligence' changes very little with ageing, when neural and psychiatric conditions (e.g., Alzheimer, dementias, and other debilitating conditions) are not counted. The intellectual capabilities of older people should not preclude their use of telecommunications.
+
+Timing of control acts may be a critical issue for older people, since they often require more time than younger people for activities such as locating, reading and understanding descriptions of these control acts. Consequently, the transaction process may be halted before it is even properly started, through an assumed lower default time-out period.
+
+Memory impairments can cause significant problems in remembering numbers in the correct order, such as a telephone number or a personal identification number (PIN code). The sequence of steps to be taken in setting up the communication process should be clearly indicated on the terminal, for example by describing them in text blocks with differing letter or background colours. People with a cognitive impairment can often function well in familiar environments, but can easily be confused when required to respond to instructions or prompts quickly.
+
+Because of memory impairments and the need for more time to locate, read and comprehend, the ability to learn new procedures declines with increasing age. Also, the ability to divide attention, e.g. to perform more than one task simultaneously, declines with increasing age. Older people must often attend to one action at a time.
+
+- **Speech and language impairments.** Speech impairment may influence speech in a general way, or only certain aspects of it, such as fluency or voice volume.
+- **Mobility impairments.** Reduced function of legs and feet may lead to people depending on aids for walking or on a wheelchair for locomotion.
+- **Motor impairments.** Reduced handgrip strength may make it difficult to grab, hold and handle objects. Old age may lead to reduced stamina, which will make it difficult to stand unsupported for any length of time.
+- **Dexterity impairments.** Reduced function of arms, hands and fingers makes activities related to moving, turning or pressing objects difficult or impossible. Accurate, fine movements, for instance of the fingers, are more difficult to perform, and tactile feedback may be diminished due to a reduced sensitivity of touch.
+
+Table 1 illustrates to what degree people tend to be affected at different ages in their lifespan (from [Charness & Brosman, 1992], Age and human factors.
+
+**Table 1/E.138 – Age and human factors**
+
+|                   | <b>Middle age (45-64)</b>                                                                                                                                                                                                          | <b>Old age (65-74)</b>                                                                                                                                                                                                                                                                                                                      | <b>Late old age (75+)</b>                                                                                                                                                                                 |
+|-------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| <b>Perceptual</b> |                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                           |
+| Vision            | Near focus declining, hence needs reading glasses or bifocals. Increased susceptibility to glare. Less successful dark adaptation. Some decline in static and dynamic visual acuity. Some loss in ability to discriminate colours. | Little focusing ability left, and loss of acuity even with corrective lenses. Less (1/3 compared with young adult) transmission of light through to the retina. Greater susceptibility to glare. Slow dark adaptation. Significant declines in static and dynamic visual acuity, in useful visual field, and colour discrimination ability. | Significant loss of visual acuity (dynamic and static), colour discrimination, and extent of the visual field. Significant risk of visual dysfunction from cataracts, glaucoma, and macular degeneration. |
+| Hearing           | Some loss at high frequencies.                                                                                                                                                                                                     | Significant loss at high frequencies and some loss at middle frequencies. Can be helped by hearing aid. Greater susceptibility to masking by noise.                                                                                                                                                                                         | Significant loss at high and middle frequencies. Likely needs a hearing aid.                                                                                                                              |
+
+**Table 1/E.138 – Age and human factors**
+
+|                                     | <b>Middle age (45-64)</b>                                                                     | <b>Old age (65-74)</b>                                                                                | <b>Late old age (75+)</b>                                                                                   |
+|-------------------------------------|-----------------------------------------------------------------------------------------------|-------------------------------------------------------------------------------------------------------|-------------------------------------------------------------------------------------------------------------|
+| <b>Perceptual</b>                   |                                                                                               |                                                                                                       |                                                                                                             |
+| Taste, smell, cutaneous sensitivity | Minimal loss.                                                                                 | Minor loss.                                                                                           | Significant loss.                                                                                           |
+| <b>Cognitive</b>                    |                                                                                               |                                                                                                       |                                                                                                             |
+| Response time                       | Some slowing in response time.                                                                | Significant slowing in response time.                                                                 | Pronounced slowing in response time.                                                                        |
+| Working memory/attention            | Minor decline in learning ability and ability to divide attention.                            | Moderate slowing in learning rate and ability to divide attention.                                    | Learning rate is halved from the twenties, and significant declines are observed for dual task performance. |
+| Knowledge base                      | Little change in fluid intelligence, and stability or increases in crystallized intelligence. | Some decline in fluid intelligence and stability or slight decreases in crystallized intelligence.    | Significant declines in fluid and crystallized intelligence.                                                |
+| <b>Physical and motoric</b>         |                                                                                               |                                                                                                       |                                                                                                             |
+| Size changes                        | Limited height loss and some weight gain.                                                     | Significant height and weight loss coupled with cohort differences that exaggerate these effects.     | Cohort is significantly smaller and there is significant loss of height and weight.                         |
+| Physical strength                   | Modest decline in strength and aerobic capacity.                                              | Moderate decline in strength and aerobic capacity. Some bone density loss.                            | Significant declines in physical strength and aerobic capacity. Significant bone density loss.              |
+| Balance and mobility                | Slight declines in balance ability with little mobility loss.                                 | Significant declines in balance ability and some difficulties with mobility.                          | Balance likely to be impaired and mobility likely to be restricted.                                         |
+| Health                              | Fairly robust.                                                                                | Greater susceptibility to chronic conditions (e.g., arthritis, diabetes, osteoporosis, hypertension). | The presence of multiple chronic conditions is highly likely.                                               |
+
+## 6 Organization of this Recommendation
+
+The process of using a public telecommunication terminal may be divided into steps:
+
+- Locating and accessing the telephone;
+- Arranging conditions for the call;
+- Initiating a call;
+- Providing payment (when applicable);
+- Identifying oneself and the communication counterpart;
+- Performing the communication;
+- Possibly setting up a further call;
+- Terminating the communication.
+
+Before, in between and during these steps there may be a need for further instructions. For each step, user requirements, often age-dependent, may be identified. These requirements will be dealt with below; they are, for each step, split up in the categories:
+
+- Visual (where appropriate, this category is combined with the tactile and dexterity categories);
+- Hearing;
+- Tactile and haptic (touch and movement);
+- Cognitive, speech and language;
+- Dexterity, strength and mobility.
+
+## **7 Locating and accessing a telephone: Visual requirements**
+
+### **7.1 Terminal identification signs**
+
+In public and often busy (and visually cluttered) places, locating a telephone can be difficult – particularly for people who are blind or have low vision. A standardized sign with accompanying text, displayed in sufficient size (letter size to maximum viewing distance at least 1/200) and placed in close context with the telephone (i.e. immediately above it or with further indications like arrows indicating its location) helps a visually impaired person to locate the telephone. In addition, the sign should be high contrast (preferably white or yellow characters on a dark background) and well illuminated.
+
+When people have located the telephone, they need to know what type of telephone it is, what it will do and how they can interact with it. The initial instructions are usually in the form of labels and signs applied to the surface of the casing or as messages on the screen.
+
+Labels should be placed where they can be easily read. If labels are positioned near the keyboard, it is important that the labels are not easily scuffed or worn away. If this is likely, then the labels should be replaced periodically.
+
+On outdoor terminals, Braille has limited value in cold weather since tactual sensitivity is dramatically reduced at low temperatures. Given that only a minority of blind people are capable of reading Braille, relying solely on Braille is not a good solution.
+
+Please refer to ITU-T Rec. E.137 for additional information.
+
+### **7.2 Lighting**
+
+The illumination on the interactive areas of the telephone should be at least 200 lux. The lighting should not cause any direct glare to the eyes of the users, or reflections from, for instance, the screen. It is recommended that the illumination at the floor level is at least 50 lux so that dropped objects can easily be located.
+
+### **7.3 Operating instructions**
+
+#### **7.3.1 General**
+
+For Latin alphabets, the guidelines on user instructions for public telecommunications services in ITU-T Rec. E.137 and [Gill, 1997] apply. For Japanese characters, JIS S 0012-2000 "Guidelines for all people including older people and people with disabilities – Usability of consumer products" contains some general, qualitative guidelines. Good standards of legibility help all users, but for many people with low vision the issue is crucial as to whether they can use the telephone.
+
+All instructions should be at least in the national language(s) [Brandt, 1995].
+
+Instructions placed on a wall behind the telephone should be placed rather low to make it easier for people in wheelchairs or for people reading through the lower part of their bifocals to read the text.
+
+#### **7.3.2 Type size and type weight**
+
+Up to a certain point, larger type will significantly improve legibility for most people with low vision. Beyond that point, further increases in type size will decrease legibility. Sixteen-point type can be recommended as the minimum type size that will help low vision users. Larger type size may partly, but only partly, compensate for low contrast and may therefore be used if contrast cannot be made high enough; see 7.3.4. For Japanese characters, the Kyoyo-Hin Foundation recommends at least 23-point text size in instruction manuals for older people or people with low vision. See <http://kyoyohin.org/eng/02kyoyohin/specifications.html>.
+
+Type weight is very important in determining legibility. Light-weight typefaces should be avoided. Regular weight type is sometimes not sufficiently legible, and it is recommended that medium or bold typefaces are used to give maximum legibility. Extra bold typeface is not recommended because the inner spaces of the letters get very small and become blurred for many people with low vision.
+
+For Japanese characters, it is also advisable to use fonts that have bold horizontal lines instead of thin ones; that is to say, rather Gothic than Minchou fonts.
+
+#### **7.3.3 Contrast**
+
+An important factor affecting legibility is contrast between the type and the background. For dark print on bright backgrounds, the contrast ratio should be at least 1:3. However, for light print on dark backgrounds, the contrast is considerably more critical and should be at least 9:1. It should be taken into account that the above limits for contrast values are inclusive of any reflections in the monitor screen [Peli, 1996]; [Roelofs, 1997].
+
+For LCD screens, contrast also depends strongly on the viewing angle [ISO 13406-2]. Older people often report having trouble with LCD screens, and there are many reasons besides ambient light and glare problems – parallax, poorly formed letters and dirty screens all add to the problems. Other flat panel display technologies may cause similar problems for older people.
+
+#### **7.3.4 Contrast reversal**
+
+For older people with clouded optical media, white or yellow type on black or a dark colour is more legible providing that the typeface weight and size are suitable. With reversed contrast line weight should be slightly less and font size slightly greater for equal legibility.
+
+#### **7.3.5 Visual confusion**
+
+Text should not run across photographs, illustrations, or patterned backgrounds. This will usually limit the contrast and confuse the eye.
+
+#### **7.3.6 Typeface styles**
+
+Most typefaces in common use are legible. Many people with low vision find contrast, size and weight more important than the choice of typeface. However, bizarre and indistinct typefaces should be avoided.
+
+When choosing a typeface it is very important to consider the numerals and choose a typeface that has an open design. Many people with low vision can easily misread the numerals 3, 5, 6, 8, 9 and 0. For example, on some typefaces the tails of the numerals curl over and thus can appear to join up, making a 3, 6 and 9 look like an 8.
+
+In general, a sans serif typeface text (e.g. Arial) is easier to read by people with low vision. The "Tiresias" typeface has been specially designed to provide high legibility and low confusion risk for people with low vision.
+
+#### **7.3.7 Capital letters**
+
+Text set in upper and lower case type is easier to read than text set in all capital letters, although a few words in capitals may present no serious difficulties.
+
+#### **7.3.8 Spacing and line length**
+
+Many readers are daunted by large amounts of close-set type. Space between lines of type should be as open as possible. Word spacing on screens should be even and slightly more open than on printed documents. Unjustified right hand margins are helpful to persons with low vision – as well as to persons with normal visual acuity – because they permit even word spacing. Avoid splitting words at the ends of lines.
+
+The width of text columns is an important factor that affects legibility. If lines of type are too long or the interline spacing is too small, the eyes have difficulties finding their way back to the beginning of the next line. A maximum of 12 words per line has been recommended for continuous text [Bouma, 1989]; as a rule of thumb, lines should be kept short, i.e. 6-7 words.
+
+#### **7.3.9 Layout**
+
+Good 'navigational' aids such as bullet points, differentiated headings and rules to separate lines in lists or unrelated sections will improve legibility significantly.
+
+If type is set in two or more columns, the margins should be wide enough to clearly separate the columns. If space is limited, then a vertical rule can help. Moving text on a screen can be very difficult to read with even a mild visual impairment, and should thus be avoided.
+
+#### **7.3.10 Diagrams**
+
+It is recommended that illustrative and clear diagrams are included where appropriate [Brandt, 1995]; [ETSI ETR 167].
+
+### **7.4 Information displays and visual indicators**
+
+On many telephones, the visual instructions on the screen are the main guide for the user. There is a large number of factors that determine whether reading the screen will be difficult or easy for older people. People who wear bifocal glasses find it difficult to read the screen of many public access telephones, since the screen may not be at a suitable distance for neither the near nor far segments of their spectacles. In addition many people leave their spectacles in their car or do not wear them in public out of vanity. So the number of people who have problems in reading the screen is many times more than the 1.5% of the population considered to be blind or to have very low vision [Gill, 1997].
+
+Therefore, the characters must be large enough (at least 9 mm high), correctly proportioned, and there must be a strong contrast between characters and background. As an alternative, it may be very useful when, early in the transaction process, the user can select the letter size in an easy way. In addition, the display should be set at an angle to enable the greatest possible legibility and to avoid light reflections [Brandt, 1995].
+
+Any visual indicators, such as LED indicators of line state, LCD payment prompts, etc., must be located in an easily visible place, for instance, on the upper front surface of the terminal and the indicator lights should be bright.
+
+#### **7.4.1 Colour blindness**
+
+Total colour blindness is rare (less than 0.003% of the population) but problems with discriminating red and green are common (over 7% of the male population). Sunlight can degrade the legibility of colour displays for all users.
+
+The ocular media (i.e. the cornea, lens and vitreous) turn more yellow with increasing age. This will reduce certain colour contrasts. Pale colours or subtle colour contrasts should therefore be avoided.
+
+#### **7.4.2 The position of information displays**
+
+Displays that are not designed for viewing in bright light should be shielded from direct or reflected sunlight or other bright light sources. They should not be positioned so that bright sources behind the display (large windows or bright spot lights) will dazzle the viewer. The display should be viewable from the eye level of a person sitting in a wheelchair. It should be possible for people with low vision to bring their eyes close to the screen (e.g., to be able to use a magnifier or other optical aid).
+
+The conflicting requirements of tall pedestrian users and wheelchair users can lead to a significant group of users having parallax problems when lining up the function keys with their displayed options. Clear lines drawn from the key to the information on the surface of the display can alleviate this problem [Gill, 1997].
+
+## **8 Locating and accessing a telephone: Hearing requirements**
+
+Hearing-impaired people do not normally encounter any hearing-related problems in locating and physically accessing a telephone terminal. However, we should note that hearing-impaired people may wish to access terminals that have special features for hearing-impaired people (e.g., inductive coupling to hearing aids, text telephones, video-telephones for sign language or lip reading), which can be indicated by symbols, icons and signs. It is important that older people with hearing impairments understand the meaning of these icons. See ITU-T Rec. E.121 and also ETSI EN 301 462 (2000) "Symbols to identify telecommunications facilities for deaf and hard of hearing people".
+
+## **9 Locating and accessing a telephone: Strength, mobility and dexterity requirements**
+
+### **9.1 Space surrounding the telephone**
+
+Public telephones should be accessible to all individuals, including older people with mobility impairments. The physical location should be such that mobility-impaired users have free and unimpeded access. Furthermore, public telephones should be located and designed in such a manner that they can be easily operated by someone in a wheelchair, using a walker or a cane. See ITU-T Rec. E.135. Thus, to allow easy approach "The floor surface should be level in the direction parallel to the facia of the terminal. The gradient of any "crossfall" should not exceed 1 in 20." [Gill, 1997].
+
+### **9.2 Area immediately around the telephone**
+
+There should be sufficient room under and around the public terminal equipment for wheelchair access and temporary parking of walking aids. A clear floor or ground space of at least 760 mm deep by 1220 mm wide that allows for a wheelchair to approach either perpendicular or parallel to the wall where the terminal is mounted should be required. Knee space required for forward approach should also be taken into account when determining clear floor and ground space. The minimum knee clearance should be 685 mm.
+
+The height of the highest operable part of the public terminal equipment should be within reach of people in wheelchairs as well as standing persons. If the clear floor space only allows for forward approach, the maximum high forward reach should be 1220 mm from the floor. If parallel approach is used, the maximum high sideward reach allowed should be 1370 mm from the floor (from 3.3/E.135). The height of the lowest operable part should not be less than 700 mm from the floor.
+
+To cater for older people with reduced stamina, some support for sitting or at least for leaning is desirable.
+
+## 10 Initialization step: Call set-up: Visual, tactile and dexterity requirements
+
+### 10.1 Keypads
+
+#### 10.1.1 Arrangement of keys
+
+A standard arrangement of the keys, in particular the numeric dialling keys, is essential for blind people and helpful for all others, especially under conditions of poor illumination. Therefore, the numeric keys shall be arranged in a four-row by three-column pattern as recommended in ITU-T Rec. E.161. To aid the orientation on the numeric keypad, in particular for blind people, a single raised dot should be used on the '5' key, as indicated in ITU-T Rec. E.161. This should be positioned so as not to reduce legibility.
+
+Possible other function keys should preferably be located to the right of the numeric keys, to reduce the chance of confusion with those keys for people with low visual acuity, and of accidentally being touched during number entry. The latter happens more easily where special function keys are positioned beneath the numeric keys.
+
+#### 10.1.2 Inter-key distance
+
+All keys, and especially groups of keys, should be spaced far enough from each other to avoid users with reduced dexterity from depressing several keys simultaneously. For the same reason, none of the procedures necessary should actually require the simultaneous pressing of more than one key. The inter-key distance (from the edge of one key top to the near edge of its neighbour) within a key group, such as the numeric dialling keys, should be 5.6-7.5 mm [Brandt, 1995]. The distance between the numeric part and the other part(s) of the keypad should preferably be larger than the inter-key distance within the numeric part, in order to aid people with low vision and blind people to identify the various key groups.
+
+#### 10.1.3 Key characteristics
+
+*Key shape.* To help differentiate keys from the numeric dialling key group from those of other groups, the shapes (and/or sizes) of the keys from the various key groups should, preferably, be clearly different [ETSI ETR 166, 1995]. As to the transversal shape of the top of the key caps, there are three possibilities: convex, flat, and concave. The latter is preferable, since such caps guide trembling, fingertips to the key centres. Convex caps should not be used since:
+
+- i) they may cause the fingers to slip off the keys; and
+- ii) specular reflections can make it difficult to read the characters on the key tops.
+
+This also holds for key caps made of glossy material [ETSI ETR 345, 1997].
+
+*Key size.* Keys should be large enough:
+
+- i) to enable people with a mild finger tremor to depress them comfortably; and
+- ii) to allow for key labels of sufficient size to be legible.
+
+The area of the tops of the numeric dialling keys should ideally be approximately 150 mm<sup>2</sup> (i.e. 12 × 12.5 mm), whereas the tops of the function keys should be 165 to 350 mm<sup>2</sup> [Brandt, 1995].
+
+*Key luminance and colour.* The luminance contrast between individual keys and control buttons and their background should be sufficient to enable visually impaired people to distinguish them. Keys and control buttons should, therefore, have another colour than the telephone [Brandt, 1995], which itself also should stand out from its surrounding. Colour may be used to distinguish between the keys from different key groups. The important thing is that the markings of the keys are clearly legible with the chosen colour.
+
+*Key illumination.* Ideally, keys should be internally illuminated when the terminal is waiting for input from the relevant keypad.
+
+#### **10.1.4 Key activation force and tactile feedback**
+
+The force to activate a key should neither be too light (to avoid accidental activation, for instance through tremor of the hands), nor too high (to avoid difficulties to activate by people with little strength). Activation forces between 0.25 and 1.5 N are recommended for general use [LUSI, 1996] – but a smaller range has been recommended for disabled and older people, namely 0.5 and 0.9 N [Brandt, 1995].
+
+Keys that actually move down when depressed provide tactile feedback during key travel. This feedback is clearest when the required force for depressing first gradually increases, and then sharply decreases during key travel (a clearly perceived "break-point").
+
+#### **10.1.5 Legibility of key labels**
+
+The keypads of desktop telephones should be tilted at an angle of 10° to 20° with the horizontal plane [Brandt, 1995]. Such keypads show less symbol shape deformities when viewed from above, and also are in general less subject to glare.
+
+Wall-mounted telephones must be usable by people in wheelchairs; therefore, they should have vertical or nearly-vertical keypads.
+
+Keys and control buttons should be labelled by means of numbers, text in the national language(s), and well-known and widely used symbols – see ITU-T Rec. E.121 and also [Brandt, 1995].
+
+People with reduced visual acuity find some numeric characters are easy to confuse. It is important that a typeface is used that has numerals with open shapes (i.e. the 'six' and 'nine' should look like 6 and 9, not like 6 and 9, which can be confused with 8 and 3).
+
+Characters on keys should be of a sufficient size, correctly proportioned and in high luminance contrast, not colour contrast, with their background [Brandt, 1995]. They should be wear-resistant, for instance engraved in the key surface. In addition:
+
+- characters must have a height of at least 7.5 mm;
+- the ratio of a character's height and line thickness should be approx. 7:1;
+- characters should be in a sans-serif font;
+- there should be at least 1 mm between the edge of the key and the character.
+
+## **11 Initialization step – Call set-up: Hearing requirements**
+
+Most hearing-impaired people capable of communicating over the telephone should be able to hear the call progress tones which are generally of lower frequencies. It should be noted that the telephone system itself has an inherent amplification compared to face-to-face communication. It is only the deaf (who would be using a text-telephone) who would require visible call progress indications. However, if a deaf person communicates with people on ordinary telephones, telecommunications relay service is used; in the USA this means that a live operator is interposed who can pass along the call progress signals.
+
+A volume control can assist people with significant hearing disability who are not using a hearing aid but it should be noted that stepped volume controls which give an X dB increase per step should work on a per-call basis, to protect the hearing of the next user of the telephone. Those using in-the-ear aids may require volume reduction to avoid overloading the aid.
+
+## **12 Initialization step – Call set-up: Cognitive requirements**
+
+Because older people may require more time to carry out dialling tasks, time-outs in the call set-up procedure should not be too short. Time must be allowed for the older person to look at a reference, such as a telephone directory, to memorize part of a number, and then to dial that bit of the number, with this process repeated possibly three or four times to dial long numbers. A shelf, reasonably near the keypad, to rest any reference material may provide assistance, although such a shelf brings with it the risk that users may forget and leave behind articles placed on it. To accommodate the difficulty some older people experience if required to divide attention between two tasks, the call set-up procedure should be as simple and linear as possible. For example, the dialling procedure should not require reference to instructions after starting and before ending. Off-line, or *en bloc* dialling, in which the entire number is entered and can be checked before any digits are sent to the network (as in mobile phones), can be helpful by avoiding the need to encounter network time-outs.
+
+## **13 Initialization step – Call set-up: Mobility requirements**
+
+All keys and buttons as well as the handset should be located so that they are easily accessible by people with mobility and/or dexterity impairments. A person using a walking aid should find an easy way to park this aid while dialling, without the danger of it falling to the ground.
+
+## **14 Initialization step – Payment: Visual requirements**
+
+### **14.1 Cards**
+
+#### **14.1.1 Smart cards**
+
+"A smart card is a credit-card-sized plastic card incorporating an integrated circuit. This circuit holds information that can be securely and accurately read by all sorts of terminals. Smart cards are able to carry larger amounts of information than magnetic stripe cards. Smart cards provide the opportunity to make machines much more 'user friendly' than they have ever been before. For older people, a smart card can carry information that tells a telephone to show larger text prompts, give prompts as audible comments or allow the user more time. Many older people and those with a cognitive impairment do not like to be rushed or to think that they are likely to be 'timed out' by the machine, so it is necessary to allow for these people to use the terminal at their own pace:
+
+- To simplify the choices such as issuing a pre-set amount of money,
+- To use larger characters for people with low vision, and
+- To use audio output of non-confidential information." [Gill, 1997]:
+
+The specification of user requirements can be found in ETSI EN 1332-4.
+
+#### **14.1.2 Embossing on cards**
+
+Blind persons face the problem of selecting the right card from their wallet. It is recommended that cards incorporate up to four embossed symbols such as capital letters with a maximum height of 7 mm, a maximum width of 7 mm, a spacing of 5 mm and a relief height of embossing between 0.45 and 0.48 mm. For further details, see [Gill and Devine-Wright, 1999].
+
+#### **14.1.3 Contactless smart cards**
+
+"A contactless card, working at a distance of up to 10 cm, will help those who have problems inserting a card in a slot. This is of particular importance to wheelchair users, those with Parkinson's disease or arthritis, and people with a visual disability." [Gill, 1997].
+
+#### **14.1.4 Card orientation**
+
+"Blind persons, and many older persons, have problems in inserting the card in the correct orientation; this is a particular problem with cards which are not embossed." [Gill, 1997]. ITU-T Rec. E.136 gives a precise recommendation on a tactile marker to facilitate the use of telecommunications cards by older and visually impaired people. The orientation problem can of course be avoided by the general introduction of card readers that accept cards in any orientation
+
+## **15 Initialization step – Payment: Hearing requirements**
+
+Hearing-impaired people should have no major problems in paying for calls in public payphones (by coins, pre-paid phone-cards or credit cards). The exception is if they cannot hear acoustic warning signals, e.g. to inform that more coins must be inserted, that a phone-card has expired, or prompts to authorize a credit card by entering a PIN code, etc. A visual display of the auditory message as text should be provided.
+
+## **16 Initialization step – Payment: Tactile, strength, mobility and dexterity requirements**
+
+### **16.1 Location of coin, card and token slots**
+
+All coin, card and token slots should be located so that they are easily accessible by people with mobility and/or dexterity impairments. Clause 9.2 describes the physical dimensions recommended to this aim. For coins this includes the space where these fall if rejected by the machine; their retrieval should not be unduly difficult.
+
+### **16.2 Cards to be inserted**
+
+Inserting cards, in particular thin flexible ones, is often more difficult than inserting coins. Insertion may be helped, especially for users with hand tremor, when the card reader entrance is somewhat funnel-shaped [Gill, 1997].
+
+### **16.3 Cards to be swiped**
+
+Swipe card readers only function at a particular, not-too-low speed of swiping and if the card is moved smoothly. This is known to present difficulties to many users without strength or dexterity impairments, and may be even more problematic for users with such impairments. To reduce the chance for those difficulties, swipe card readers should accept a range of swipe speeds, from fairly low onwards. In addition, their location is especially critical, since they need not only to be reached, but also to be operated, with sufficient grip in the hand holding the swiped card [Gill, 1997].
+
+## **17 Communication step: Tactile, strength, mobility and dexterity requirements**
+
+### **17.1 The cord connecting handset and terminal**
+
+The cord connecting the handset to the telephone should have sufficient length so that the handset can easily be used by people in wheelchairs (as well as by very short or very tall users). The cord should therefore be at least 1.7 m long [ETR 166, section 1.2.1]. It should be attached so that it will not be in the way when the handset is replaced. If it is armoured the combination of cable and armour should not be too stiff, and the armoured cable plus handset should not be too heavy. If the cord is coiled, stretching it should not require too much effort.
+
+### **17.2 The handset: location, weight and shape**
+
+Clauses 9.2 and 13 describe the location requirements for the handset. As to its shape, reduced handgrip strength may make it difficult to grab, handle and hold the handset, especially to hold it for an extended period. This applies in particular to heavy handsets and very wide ones. The shape of the handle's cross-section should not be (more or less) triangular, because that prevents "cradling" the handset between head and shoulder, but rather rectangular (without sharp edges), or oval. Handles with round cross-sections can be difficult to orient. Preferably, the weight of the handset and the part of the possibly armoured cable that has to be lifted by the user should be between 150 and 175 g [ETR 166, section 1.2.6]. Furthermore, the handset should be balanced in the hand. The earpiece should not be substantially heavier than the mouthpiece, or vice versa.
+
+### **17.3 Hands-free operation**
+
+The availability of a hands-free mode is a clear advantage to older people. The hands-free operation key should be easily accessible, for instance in the bottom or right-hand row of non-numerical keys. The volume should be adjustable. If the microphone can be switched off there should be unmistakable visual and audible indication as to whether the microphone is switched on or off. The design of the handset holder should facilitate cradling; in particular, it should ensure that the handset relocates correctly under its own weight. A tilted empty space to support a note pad may be provided; tilted to prevent people from forgetting belongings on it.
+
+## **18 Communication phase**
+
+Many older people experience a gradual loss of hearing, while the capability to speak remains more or less unaffected. Even when the ability to speak is retained, hearing loss is the loss that interferes most with speech communication, either face-to-face or over the telephone. Speech communication is impeded to various degrees depending on the severity of the hearing impairment, from problems with perceiving some speech sounds, to not being able to hear any speech at all. Below the problems and solutions have been organized according to severity of hearing loss.
+
+### **18.1 Mildly hard of hearing (some high frequency loss)**
+
+This condition normally does not warrant any special provisions other than a good acoustic treatment of the phone booth or of the environment around the telephone. The ordinary telephone usually provides several dB of amplification and does actually provide some measure of compensation for a slight hearing loss compared to face-to-face communication. Some people in this group may benefit from a telephone with a high-quality earphone, but otherwise there is little that needs to be done for this group.
+
+### **18.2 Moderately hard of hearing (significant loss of high frequencies and some loss of middle frequencies)**
+
+This group should be the main users of hearing aids, but unfortunately pride and vanity often turn many older people with hearing losses away from using them because hearing aids are considered to be more stigmatising than, for instance, spectacles.
+
+In former times, the electromagnetic field around the coil in the earphone (actually electromagnetic pollution) provided an inductive field that could be picked up by hearing aids with a 'T' setting (for use in rooms with amplifier and induction loop). As the new piezoelectric earphones were introduced, and quickly became predominant, people using hearing aids lost this special advantage, and there was soon a demand for telephones that provided inductive coupling.
+
+Various national and regional standards bodies have responded by creating standards for inductive coupling between telephones and hearing aids. It is not particularly expensive to provide inductive coupling to a telephone (a special handset), and it provides a great benefit to users of hearing aids. ITU-T Rec. P.370; (The Coupling of hearing aids to telephone sets), gives figures for the sensitivity and frequency characteristics of coupling coils intended to couple to hearing aids equipped with induction pick-up coils. An annex describes measurement methods. The provision of additional receiver amplification and electrical coupling are also dealt with in ITU-T Rec. P.370.
+
+Low signal-to-noise ratio will create problems with failing hearing. In this case it is difficult to pick out the acoustic signal from the background noise. This becomes even more difficult if there is a large difference in hearing loss between the two ears (which is not unusual). It is then important to exclude all unwanted noise. One way is to occlude the weaker ear, but a better way is to provide the acoustic signal to both ears. The provision for an extra handset is often of significant help to hard-of-hearing people. The extra handset can also be used by a second person to 'repeat' or 'shadow' the speech in the phone to help the hard-of-hearing or deaf person to lip-read.
+
+Extra amplification is often seen as an important measure for dealing with the hard-of-hearing. However, we should note that extra amplification might often put hard-of-hearing people worse off than not having the extra amplification. The reason for this is that neural hearing loss is usually accompanied by *recruitment* or *over-recruitment*. Recruitment means that the experienced sound intensity (loudness) grows faster with increasing acoustic intensity than for people with normal hearing. With over-recruitment, even just a few dB of amplification can render a sound unbearably loud and distort the sound (speech) so much that it becomes unintelligible.
+
+Extra amplification is therefore not always the first choice for many people with middle to serious hearing loss. Again, a good acoustic environment with no distorting echoes and low ambient noise, and an extra handset to exclude extraneous noise, are the best option.
+
+### **18.3 Severe hearing loss (significant loss of high and middle frequencies)**
+
+People suffering from this have very great problems communicating verbally, either face-to-face or via telephone. Many of these people have to get support from lip-reading, which means that they must be able to see the other party. The video-telephone provides this possibility, but most ordinary video-telephones have too low picture quality to support lip-reading.
+
+### **18.4 Profoundly deaf (cannot use hearing for any form of verbal communication)**
+
+Profoundly deaf people cannot communicate acoustically at all and must rely on other forms of communication (sign language, text telephones, internet chat, instant messaging, SMS (short message service)). Video-telephones for sign language do not need to have as high spatial and temporal resolution as video-telephones used for lip-reading. To provide video-telephones and text telephones for this group will eventually be necessary. It may be noted that some countries already require a proportion of payphones to have text-telephone facilities. Text-telephones provided should comply with ITU-T Rec. V.18: (Operational and interworking requirements for modems operating in the text telephone mode). Also, some countries already require that a relay service should be provided to enable communication with deaf people without a text-telephone. ETSI TR 101 806 gives "Guidelines for telecommunication relay services for text telephones".
+
+## **19 Next call (follow-on call): Visual, tactile, strength, mobility and dexterity requirements**
+
+In general, the same issues apply here as in the steps on Initialization: Call set-up, and in Initialization: Payment (see above). In particular, the following issues should be mentioned:
+
+### **19.1 Redial**
+
+For older people with motor impairments, blind and visually impaired people and people with poor memory, it is an advantage that the telephone terminal is equipped with an automatic redial facility. This saves them from many keystrokes and from having to remember a telephone number when they need to redial e.g. in the case of busy line. It is important that the redial facility is easy to use and only requires pressing one key, and that the redial key is accessible (e.g. in the bottom or right-hand row) and easy to locate and identify. The redial facility should be labelled in the national language of the country in question or a widely recognized symbol or icon, See also 6.11-6.13/E.137.
+
+### **19.2 New number call**
+
+The 'next call' key (for a new number) when and if provided should be located so that it is easily accessible by persons who are mobility impaired. Clauses 9.2 and 13 describe the physical dimensions recommended for easy accessibility.
+
+## **20 Terminate call: Visual requirements**
+
+### **20.1 Receipts**
+
+To aid users with low vision, receipts should be printed with a minimum type size of 12 points with a sans serif typeface with upper- and lower-case text. If space permits, 16-point type would be preferable. It is important that the print has good contrast on opaque paper with a minimum of background pattern. A common complaint is poor print quality on receipts; often this is the result of the printer ribbon not being replaced regularly.
+
+## **21 Terminate call: Hearing requirements**
+
+There should be no special problems to terminate a call for hearing-impaired people except for any warning prompt to take the phonecard or any remaining unused coins or change given by the payphone. Since deaf and hard-of-hearing people cannot hear any warning tones to advise them to take the card, some alternative means must be found, for instance, a flashing light or optical message.
+
+## **22 Terminate call: Tactile, strength, mobility and dexterity requirements**
+
+### **22.1 Retrieving remaining coins**
+
+As described in 16.1, coin retrieval at the end of making a call should not be unduly difficult. This implies that, first, the space where these remaining coins are held should be within easy reach, also for wheelchair users; see clauses 16.1, 9.2 and 13. But, secondly, the flap or lid that may be used to close the space for the remaining coins, to prevent them from falling to the ground and hiding them from view, should not be too difficult to open for people with low dexterity and finger strength, possibly having to do this from an awkward position.
+
+### **22.2 Card retrieval**
+
+As with the remaining coins-space, described in 22.1, the card exit slot should be located within easy reach for everybody; see clauses 9.2 and 13. In addition, when the card has come out it should protrude at least 2 cm from the slot, and only a small force should be needed to pull the protruding card out of the terminal [Gill, 1997].
+
+## 23 Bibliography
+
+- BLAICH (R.I.): Taming technology for the benefit of the aging – and everyone else. *Gerontechnology, IOS Press*, H. Bouma and J.A.M. Graafmans: Editors. Amsterdam 1992.
+- BOUMA (H.): Goed leesbaar drukwerk op papier en beeldscherm. *Oog en Werk, SDU uitgeverij*, pp. 91-103, J.J. Vos and Ch.P. Legein: Editors. The Hague 1989.
+- BRANDT (Å.): Telephones for All – Nordic Design guidelines. *Åarhus: The Nordic Committee on Disability*, 1995.
+- CHARNESS (N.), BROSMAN (E. A.): Age and human factors. *The handbook of aging and cognition*, pp. 495-551, F.I.M. Craik and T.A. Salthouse: Editors. Lawrence Erlbaum Associates, New Jersey 1992.
+- COLLINS (S.C.), BHATTI [J.Z.], DEXTER [S.L.], RABBITT [P.M.A.]: Elderly people in a new world: Attitudes to advanced communication technologies. *Gerontechnology, IOS Press*, H. Bouma and J.A.M. Graafmans: Editors. Amsterdam 1992.
+- DALL [J.L.C.]: The demography of Europe. *Gerontechnology, IOS Press*, H. Bouma and J.A.M. Graafmans: Editors. Amsterdam 1992.
+- GILL [J.]: Access prohibited? Information for designers of public access terminals. *Royal National Institute for the Blind*, London 1997.
+- GILL (J.), DEVINE-WRIGHT (H.): Selecting cards by touch. *Royal National Institute for the Blind*, ISBN 1 86048 5, London 1999.
+- LUSI Project: Human Factors Guidelines for Designers of Telecommunication Services for Non-Expert Users, *HUSAT Research Institute* (for LUSI Consortium) Loughborough, UK 1996.
+- PELI [E.]: Test of a model of foveal vision by using simulations. *Journal of the Optical Society of America*, A **13**, pp. 1131-1138, 1996.
+- ROELOFS (T.): Image Enhancement for Low Vision. *Ph.D. thesis, Eindhoven University of Technology TU/e*, Eindhoven 1977.
+- ETSI ES 201 381 (1998), *Human Factors (HF); Telecommunications keypads and keyboards; Tactile identifiers*.
+- ETSI ETR 029 (1991), *Human Factors (HF); Access to telecommunications for people with special needs; Recommendations for improving and adapting telecommunications terminals and services for people with impairments*.
+- ETSI ETR 068 (1993), *Human Factors (HF); European standardization situation of telecommunications facilities for people with special needs*.
+- ETSI ETR 165 (1995), *Human Factors (HF); Recommendation for a tactile identifier on machine readable cards for telecommunication terminals*.
+- ETSI ETR 166 (1995), *Human Factors (HF); User instructions for public telecommunications services; Design guidelines*.
+- ETSI ETR 167 (1995) *Human Factors (HF); User instructions for public telecommunications services; Design guidelines*.
+- ETSI ETR 333 (1997) and (1998), *Human Factors (HF); Text Telephony; Basic user requirements and recommendations*.
+- ETSI ETR 334 (1996), *Human Factors (HF); The implications of human ageing for the design of telephone terminals*.
+- ETSI ETR 345 (1997), *Human Factors (HF); Characteristics of telephone keypads and keyboards. Requirements of elderly and disabled people*.
+
+- ETSI TR 101 806 (2000), *Human Factors (HF); Guidelines for Telecommunication Relay Services for Text Telephones*.
+
+## SERIES OF ITU-T RECOMMENDATIONS
+
+|                 |                                                                                                                                |
+|-----------------|--------------------------------------------------------------------------------------------------------------------------------|
+| Series A        | Organization of the work of ITU-T                                                                                              |
+| Series B        | Means of expression: definitions, symbols, classification                                                                      |
+| Series C        | General telecommunication statistics                                                                                           |
+| Series D        | General tariff principles                                                                                                      |
+| <b>Series E</b> | <b>Overall network operation, telephone service, service operation and human factors</b>                                       |
+| Series F        | Non-telephone telecommunication services                                                                                       |
+| Series G        | Transmission systems and media, digital systems and networks                                                                   |
+| Series H        | Audiovisual and multimedia systems                                                                                             |
+| Series I        | Integrated services digital network                                                                                            |
+| Series J        | Cable networks and transmission of television, sound programme and other multimedia signals                                    |
+| Series K        | Protection against interference                                                                                                |
+| Series L        | Construction, installation and protection of cables and other elements of outside plant                                        |
+| Series M        | TMN and network maintenance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits |
+| Series N        | Maintenance: international sound programme and television transmission circuits                                                |
+| Series O        | Specifications of measuring equipment                                                                                          |
+| Series P        | Telephone transmission quality, telephone installations, local line networks                                                   |
+| Series Q        | Switching and signalling                                                                                                       |
+| Series R        | Telegraph transmission                                                                                                         |
+| Series S        | Telegraph services terminal equipment                                                                                          |
+| Series T        | Terminals for telematic services                                                                                               |
+| Series U        | Telegraph switching                                                                                                            |
+| Series V        | Data communication over the telephone network                                                                                  |
+| Series X        | Data networks and open system communications                                                                                   |
+| Series Y        | Global information infrastructure and Internet protocol aspects                                                                |
+| Series Z        | Languages and general software aspects for telecommunication systems                                                           |

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+
+
+![ITU logo](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg)
+
+The logo of the International Telecommunication Union (ITU) features a globe with a lightning bolt and the letters 'ITU'.
+
+ITU logo
+
+INTERNATIONAL TELECOMMUNICATION UNION
+
+**ITU-T**
+
+**E.148**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+**TELEPHONE NETWORK AND ISDN  
+OPERATION, NUMBERING, ROUTING  
+AND MOBILE SERVICE**
+
+---
+
+**ROUTING OF TRAFFIC BY AUTOMATIC  
+TRANSIT EXCHANGES**
+
+**ITU-T Recommendation E.148**
+
+(Extract from the *Blue Book*)
+
+---
+
+# NOTES
+
+1 ITU-T Recommendation E.148 was published in Fascicle II.2 of the *Blue Book*. This file is an extract from the *Blue Book*. While the presentation and layout of the text might be slightly different from the *Blue Book* version, the contents of the file are identical to the *Blue Book* version and copyright conditions remain unchanged (see below).
+
+2 In this Recommendation, the expression “Administration” is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+# **ROUTING OF TRAFFIC BY AUTOMATIC TRANSIT EXCHANGES**
+
+In the two cases mentioned hereafter it may be advantageous from a general economic point of view (taking into account the loss probability and cost) to route traffic by automatic transit exchanges:
+
+## *Case 1*
+
+Where there is a light traffic load between two countries, it may be desirable to route this traffic through an automatic transit exchange, rather than to provide a small group of direct circuits.
+
+The considerations normally apply to the case where the introduction of semiautomatic operation is considered, but they should be equally valid for traffic which terminates on a manual international trunk exchange, reached through an automatic transit exchange.
+
+*Note* – The purely economic point of view from which these conclusions are drawn excludes all other considerations, particularly the following:
+
+- a) It is necessary that the transit exchanges through which it is desired to route the traffic should be prepared to accept the transit traffic which would be offered to them and Administrations involved should design their circuit groups to satisfy the requirements of Part II of Fascicle II.3 in so far as loss probability is concerned.
+- b) The provision of direct circuits may be preferred to a routing entirely via a transit centre for other reasons, e.g. the provision of broadcast programme circuits, control circuits for these transmissions, voice-frequency telegraph circuits, etc.
+
+## *Case 2*
+
+In certain cases, particularly where the traffic between two countries is heavy, and when, for instance, it may lead to the deferment of a new installation, it may be advantageous to route a certain proportion of the additional traffic (peak traffic) by way of a transit automatic centre.

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+
+
+**ITU-T**
+
+**E.169.1**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+(02/2019)
+
+SERIES E: OVERALL NETWORK OPERATION,  
+TELEPHONE SERVICE, SERVICE OPERATION AND  
+HUMAN FACTORS
+
+International operation – Numbering plan of the  
+international telephone service
+
+---
+
+**Application of Recommendation ITU-T E.164  
+numbering plan for universal international  
+freephone numbers for international freephone  
+service**
+
+Recommendation ITU-T E.169.1
+
+# **OVERALL NETWORK OPERATION, TELEPHONE SERVICE, SERVICE OPERATION AND HUMAN FACTORS**
+
+|                                                                                                   |                    |
+|---------------------------------------------------------------------------------------------------|--------------------|
+| INTERNATIONAL OPERATION                                                                           |                    |
+| Definitions                                                                                       | E.100–E.103        |
+| General provisions concerning Administrations                                                     | E.104–E.119        |
+| General provisions concerning users                                                               | E.120–E.139        |
+| Operation of international telephone services                                                     | E.140–E.159        |
+| <b>Numbering plan of the international telephone service</b>                                      | <b>E.160–E.169</b> |
+| International routing plan                                                                        | E.170–E.179        |
+| Tones in national signalling systems                                                              | E.180–E.189        |
+| Numbering plan of the international telephone service                                             | E.190–E.199        |
+| Maritime mobile service and public land mobile service                                            | E.200–E.229        |
+| OPERATIONAL PROVISIONS RELATING TO CHARGING AND ACCOUNTING IN THE INTERNATIONAL TELEPHONE SERVICE |                    |
+| Charging in the international telephone service                                                   | E.230–E.249        |
+| Measuring and recording call durations for accounting purposes                                    | E.260–E.269        |
+| UTILIZATION OF THE INTERNATIONAL TELEPHONE NETWORK FOR NON-TELEPHONY APPLICATIONS                 |                    |
+| General                                                                                           | E.300–E.319        |
+| Phototelegraphy                                                                                   | E.320–E.329        |
+| ISDN PROVISIONS CONCERNING USERS                                                                  | E.330–E.349        |
+| INTERNATIONAL ROUTING PLAN                                                                        | E.350–E.399        |
+| NETWORK MANAGEMENT                                                                                |                    |
+| International service statistics                                                                  | E.400–E.404        |
+| International network management                                                                  | E.405–E.419        |
+| Checking the quality of the international telephone service                                       | E.420–E.489        |
+| TRAFFIC ENGINEERING                                                                               |                    |
+| Measurement and recording of traffic                                                              | E.490–E.505        |
+| Forecasting of traffic                                                                            | E.506–E.509        |
+| Determination of the number of circuits in manual operation                                       | E.510–E.519        |
+| Determination of the number of circuits in automatic and semi-automatic operation                 | E.520–E.539        |
+| Grade of service                                                                                  | E.540–E.599        |
+| Definitions                                                                                       | E.600–E.649        |
+| Traffic engineering for IP-networks                                                               | E.650–E.699        |
+| ISDN traffic engineering                                                                          | E.700–E.749        |
+| Mobile network traffic engineering                                                                | E.750–E.799        |
+| QUALITY OF TELECOMMUNICATION SERVICES: CONCEPTS, MODELS, OBJECTIVES AND DEPENDABILITY PLANNING    |                    |
+| Terms and definitions related to the quality of telecommunication services                        | E.800–E.809        |
+| Models for telecommunication services                                                             | E.810–E.844        |
+| Objectives for quality of service and related concepts of telecommunication services              | E.845–E.859        |
+| Use of quality of service objectives for planning of telecommunication networks                   | E.860–E.879        |
+| Field data collection and evaluation on the performance of equipment, networks and services       | E.880–E.899        |
+| OTHER                                                                                             | E.900–E.999        |
+| INTERNATIONAL OPERATION                                                                           |                    |
+| Numbering plan of the international telephone service                                             | E.1100–E.1199      |
+| NETWORK MANAGEMENT                                                                                |                    |
+| International network management                                                                  | E.4100–E.4199      |
+
+*For further details, please refer to the list of ITU-T Recommendations.*
+
+## Recommendation ITU-T E.169.1
+
+## Application of Recommendation ITU-T E.164 numbering plan for universal international freephone numbers for international freephone service
+
+## Summary
+
+Recommendation ITU-T E.169.1 details the application of the ITU-T E.164 Numbering Plan for the Universal International Freephone Numbers (UIFN) in the provisioning of International Freephone Service (IFS) as defined in Recommendation ITU-T E.152. It has been amended and refined in the light of experience gained by service providers and the UIFN Registrar since the inauguration of the UIFN in early 1997.
+
+This Recommendation was previously numbered ITU-T E.169. It has been renumbered as ITU-T E.169.1, and forms part of the ITU-T 169.x-series Recommendations describing the numbering plans and assignment procedures for various international services.
+
+## History
+
+| Edition | Recommendation | Approval   | Study Group | Unique ID*                                                                |
+|---------|----------------|------------|-------------|---------------------------------------------------------------------------|
+| 1.0     | ITU-T E.169    | 1996-02-19 | 2           | <a href="http://handle.itu.int/11.1002/1000/3309">11.1002/1000/3309</a>   |
+| 2.0     | ITU-T E.169    | 1998-11-13 | 2           | <a href="http://handle.itu.int/11.1002/1000/4527">11.1002/1000/4527</a>   |
+| 3.0     | ITU-T E.169.1  | 2001-09-14 | 2           | <a href="http://handle.itu.int/11.1002/1000/5484">11.1002/1000/5484</a>   |
+| 4.0     | ITU-T E.169.1  | 2019-02-28 | 2           | <a href="http://handle.itu.int/11.1002/1000/13736">11.1002/1000/13736</a> |
+
+---
+
+\* To access the Recommendation, type the URL <http://handle.itu.int/> in the address field of your web browser, followed by the Recommendation's unique ID. For example, <http://handle.itu.int/11.1002/1000/11830-en>.
+
+## FOREWORD
+
+The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis.
+
+The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics.
+
+The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1.
+
+In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC.
+
+### NOTE
+
+In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some other obligatory language such as "must" and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party.
+
+## INTELLECTUAL PROPERTY RIGHTS
+
+ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process.
+
+As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at <http://www.itu.int/ITU-T/ipr/>.
+
+© ITU 2019
+
+All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU.
+
+## Table of Contents
+
+|     |                                                                                                    | Page |
+|-----|----------------------------------------------------------------------------------------------------|------|
+| 1   | Scope.....                                                                                         | 1    |
+| 2   | References.....                                                                                    | 1    |
+| 3   | Definitions .....                                                                                  | 1    |
+| 3.1 | Terms defined elsewhere .....                                                                      | 1    |
+| 3.2 | Terms defined in this Recommendation.....                                                          | 1    |
+| 4   | Abbreviations and acronyms .....                                                                   | 2    |
+| 5   | UIFN principles and format.....                                                                    | 3    |
+| 5.1 | UIFN principles .....                                                                              | 3    |
+| 5.2 | UIFN format .....                                                                                  | 3    |
+| 6   | Number assignment principles .....                                                                 | 3    |
+| 7   | Applicant procedures .....                                                                         | 4    |
+| 8   | Registrar procedures .....                                                                         | 4    |
+| 9   | Change request procedures .....                                                                    | 4    |
+| 10  | Registrar start-up and duplicate request procedures.....                                           | 4    |
+| 11  | Preparation of Universal International Freephone Number request form .....                         | 4    |
+| 12  | Preparation of Universal International Freephone Number status notification form ...               | 4    |
+| 13  | Preparation of UIFN Multiple ROAs notification form .....                                          | 4    |
+|     | Annex A – Applicant procedures.....                                                                | 5    |
+|     | Annex B – Registrar procedures .....                                                               | 7    |
+|     | Annex C – Change request procedures .....                                                          | 9    |
+| C.1 | Change request procedures.....                                                                     | 9    |
+|     | Annex D – Registrar start-up and duplicate request procedures.....                                 | 10   |
+| D.1 | Registrar procedures .....                                                                         | 10   |
+| D.2 | Duplicate requests procedures .....                                                                | 10   |
+|     | Annex E – Preparation of Universal International Freephone Number Request Form .....               | 13   |
+| E.1 | Preparation of Universal International Freephone Number<br>Request Form – Part A .....             | 13   |
+| E.2 | Preparation of Universal International Freephone Number<br>Request Form – Part B .....             | 13   |
+|     | Annex F – Preparation of Universal International Freephone Number Status Notification<br>Form..... | 16   |
+| F.1 | Preparation of Universal International Freephone Number Status<br>Notification Form –Part A .....  | 16   |
+| F.2 | Preparation of Universal International Freephone Number Status<br>Notification Form – Part B ..... | 16   |
+|     | Annex G – Preparation of UIFN Multiple RoAs Notification Form .....                                | 18   |
+| G.1 | Preparation of UIFN Multiple ROAs Notification Form – Part A .....                                 | 18   |
+
+|                                                                           | <b>Page</b> |
+|---------------------------------------------------------------------------|-------------|
+| G.2    Preparation of UIFN Multiple ROAs Notification Form – Part B ..... | 18          |
+| Appendix I – Applicant procedure.....                                     | 20          |
+| Appendix II – Registrar procedure.....                                    | 21          |
+| Appendix III – Duplicate request procedure.....                           | 22          |
+
+## Recommendation ITU-T E.169.1
+
+## Application of Recommendation ITU-T E.164 numbering plan for universal international freephone numbers for international freephone service
+
+# 1 Scope
+
+This Recommendation details the application of the ITU-T E.164 Numbering Plan for Universal International Freephone Numbers (UIFN) in the provisioning of International Freephone Service (IFS) as defined in [ITU-T E.152]. The assignment of numbering resources to applicants under ITU-T E.169.1 is the function/responsibility of the centralized ITU Numbering Administration Group (ITU-NAG) within the ITU-T Telecommunication Standardization Bureau (TSB).
+
+## 2 References
+
+The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation.
+
+- [ITU-T E.152] Recommendation ITU-T E.152 (2006), *International freephone service*.
+- [ITU-T E.164] Recommendation ITU-T E.164 (2010), *The international public telecommunication numbering plan*.
+- [ITU-T E.164.1] Recommendation ITU-T E.164.1 (2008), *Criteria and procedures for the reservation, assignment and reclamation of E.164 country codes and associated identification codes (ICs)*.
+- [ITU-T E.190] Recommendation ITU-T E.190 (1997), *Principles and responsibilities for the management, assignment and reclamation of E-series international numbering resources*.
+- [ITU-T E.195] Recommendation ITU-T E.195 (2000), *ITU-T International numbering resource administration*.
+
+## 3 Definitions
+
+### 3.1 Terms defined elsewhere
+
+None.
+
+### 3.2 Terms defined in this Recommendation
+
+This Recommendation defines the following terms:
+
+**3.2.1 ageing period:** A nominal six-month period of time when a previously assigned UIFN remains idle before being reassigned. A UIFN may be reassigned after it has been aged for three months, if requested by an applicant.
+
+**3.2.2 applicant<sup>1</sup>:** The service provider, an ROA, as defined in the Annex of the ITU Constitution (Geneva, 1992) that submits an application for a Global Subscriber Number (GSN) of the UIFN on behalf of the IFS customer in accordance with this Recommendation and with [ITU-T E.152].
+
+**3.2.3 Freephone Subscriber Number (FSN):** Freephone subscriber number is the subscriber number portion of the national ITU-T E.164 freephone number as shown in Figure 1. The subscriber number length is in accordance with the national number plan and does not include prefixes, suffixes, access codes, or any additional digits used in promoting the number. This is the entire and only portion of a national freephone number that qualifies for priority when embedded in a UIFN.
+
+![Diagram of a national freephone number structure showing NDC and SN components.](990567efebf979be51f56d1150012c9d_img.jpg)
+
+The diagram illustrates the structure of a national freephone number. It consists of two rectangular boxes labeled 'NDC' and 'SN'. Below the 'SN' box, a double-headed arrow points to the text 'Freephone Subscriber Number'. Below the 'NDC' box, a longer double-headed arrow points to the text 'National Freephone Number, including the freephone indicator'. Below the diagram, a note states: 'NOTE – The freephone indicator may be a prefix, according to national agreements.'
+
+Diagram of a national freephone number structure showing NDC and SN components.
+
+E.169.1(19)\_F01
+
+**Figure 1 – Freephone Subscriber Number as part of the national ITU-T E.164 freephone number**
+
+**3.2.4 IFS caller:** The person who places a call to a UIFN.
+
+**3.2.5 IFS customer:** The individual or entity that obtains a UIFN from an IFS service provider.
+
+**3.2.6 IFS service provider:** The recognized operating agency (ROA) that provides the international freephone service (IFS).
+
+**3.2.7 number embedding:** A method by which an international freephone service (IFS) customer's existing national Freephone Subscriber Number (FSN) is integrated as part of the Global Subscriber Number (GSN) portion of the new Universal International Freephone Number (UIFN).
+
+**3.2.8 registrar:** The entity responsible for processing registration requests, and assignment of the GSN portion of the UIFN in accordance with this Recommendation and with [ITU-T E.152].
+
+**3.2.9 Universal International Freephone Number:** The Universal International Freephone Number (UIFN) enables an IFS customer to be allocated a unique freephone number(s) that is the same throughout the world. A UIFN is composed of a 3-digit country code for a global service application, 800 and an 8-digit GSN.
+
+## 4 Abbreviations and acronyms
+
+This Recommendation uses the following abbreviations and acronyms:
+
+|     |                                 |
+|-----|---------------------------------|
+| CC  | Country Code                    |
+| FSN | Freephone Subscriber Number     |
+| GSN | Global Subscriber Number        |
+| IFS | International Freephone Service |
+| NDC | National Destination Code       |
+| ROA | Recognized Operating Agency     |
+| SN  | Subscriber Number               |
+
+---
+
+<sup>1</sup> National Administrations may, as a national matter, choose to co-ordinate applications from their ROAs, or to be the Applicant on behalf of their ROAs.
+
+TSB Telecommunication Standardization Bureau
+
+UIFN Universal International Freephone Number
+
+## 5 UIFN principles and format
+
+### 5.1 UIFN principles
+
+The following principles were used in the development of the UIFN format and assignment procedures, and should be considered with the use of UIFNs.
+
+**5.1.1** To ensure full IFS customer flexibility, the UIFN should be portable, giving the IFS customers the ability to retain their assigned UIFNs and change their service providers. The Global Subscriber Number (GSN) portion of the UIFN does not contain any identification of country (origin or destination), administrative code or service provider code.
+
+**5.1.2** The structure of UIFN should offer IFS customers freedom in choosing the digits to form a particular UIFN that suits their purposes.
+
+**5.1.3** The format of the UIFN should facilitate proper and efficient routing of individual calls by service providers.
+
+**5.1.4** To ensure fair and unbiased treatment of all UIFNs related activities among nations, IFS service providers and IFS customers.
+
+### 5.2 UIFN format
+
+A UIFN is composed of a 3-digit country code (CC) for a global service application, 800 and an 8-digit GSN, resulting in an 11-digit fixed format<sup>2</sup> (see Figure 2):
+
+As an example, an IFS customer's UIFN could be 800 12345678, where 12345678 is the IFS customer's GSN.
+
+An IFS caller must dial an international prefix prior to the UIFN.
+
+![Diagram illustrating the UIFN format. It shows two boxes: '800' (3 digits) and 'GSN' (8 digits). Below the boxes, arrows indicate the 'Global Subscriber Number (GSN)' for the 8-digit part and the 'Universal International Freephone Number (UIFN)' for the entire 11-digit number. The text 'E.169.1(19)_F02' is in the bottom right corner.](65550960f5c5afd9d27706aaeddb0638_img.jpg)
+
+The diagram shows two rectangular boxes side-by-side. The left box contains the number '800' and is labeled '3 digits' below it. The right box contains the letters 'GSN' and is labeled '8 digits' below it. Below the boxes, there are two horizontal double-headed arrows. The top arrow spans the width of the 'GSN' box and is labeled 'Global Subscriber Number (GSN)'. The bottom arrow spans the combined width of both the '800' box and the 'GSN' box and is labeled 'Universal International Freephone Number (UIFN)'. In the bottom right corner of the diagram area, the text 'E.169.1(19)\_F02' is present.
+
+Diagram illustrating the UIFN format. It shows two boxes: '800' (3 digits) and 'GSN' (8 digits). Below the boxes, arrows indicate the 'Global Subscriber Number (GSN)' for the 8-digit part and the 'Universal International Freephone Number (UIFN)' for the entire 11-digit number. The text 'E.169.1(19)\_F02' is in the bottom right corner.
+
+**Figure 2 – UIFN format**
+
+## 6 Number assignment principles
+
+**6.1** All assigned UIFNs must be used in conformance with this Recommendation.
+
+**6.2** Applications for UIFNs will only be considered when a valid, see c) and d) below, and complete UIFN Request Form has been received from an eligible Applicant by the Registrar.
+
+**6.3** UIFNs will be assigned to IFS customers who will use the IFS service between two or more countries, i.e., IFS customers offering a service that is only accessed from within a single national, or integrated numbering plan, will not be considered eligible.
+
+---
+
+<sup>2</sup> The network operator should be aware that more than eleven digits may be dialled for commercial reasons. These calls should not be blocked for that reason.
+
+6.4 UIFNs can only be assigned to IFS customers committed to implement the UIFN within 180 days of the date of reservation.
+
+6.5 UIFNs may not be sold, licensed, or traded. Nor may they be transferred, except in the case of a merger, acquisition or joint venture. Any such transfer shall be notified to the Registrar.
+
+6.6 The assignment of a UIFN by the Registrar does not create an ownership interest, right or claim to the UIFN on the part of the IFS customer or IFS service provider. Its use shall be subject to the terms set forth herein.
+
+6.7 UIFNs are classified as reserved until the Applicant notifies the Registrar that the UIFN is implemented (180 days maximum).
+
+6.8 The UIFN shall be unique to an IFS customer.
+
+6.9 Any violation of these principles by the IFS customer or IFS service provider of a UIFN will result in the Registrar reclaiming the assigned number.
+
+## **7 Applicant procedures**
+
+The procedures, which the Applicant is to follow, are contained in Annex A.
+
+## **8 Registrar procedures**
+
+The procedures, which the Registrar is to follow, are contained in Annex B.
+
+## **9 Change request procedures**
+
+The procedures which the Registrar, the Applicant, and recognized operating agencies (ROAs) are to follow in order for the Registrar to maintain correct customer and ROA information in the UIFN database are contained in Annex C.
+
+## **10 Registrar start-up and duplicate request procedures**
+
+The Registrar start-up procedures and duplicate request procedures used in initiating this service are included in Annex D.
+
+## **11 Preparation of Universal International Freephone Number request form**
+
+The procedure for preparation of the Universal International Freephone Number request form is included in Annex E.
+
+## **12 Preparation of Universal International Freephone Number status notification form**
+
+The procedure for preparation of the Universal International Freephone Number status notification form is included in Annex F.
+
+## **13 Preparation of UIFN Multiple ROAs notification form**
+
+The procedure for preparation of the UIFN Multiple ROAs notification form is included in Annex G.
+
+## Annex A
+
+### Applicant procedures
+
+(This annex forms an integral part of this Recommendation.)
+
+The Applicant has the responsibility for the following:
+
+- a) The processing of all applications received on behalf of their IFS customers. The Applicant is the sole interface with the IFS customer.
+- b) The submission of valid requests for a UIFN in accordance with this Recommendation, using the particular UIFN format as described in clause 5. Invalid requests will be returned by the Registrar.
+- c) The sending of the UIFN request form, Part A, on behalf of the IFS customer, by facsimile to the Registrar. The Applicant submits only one form per number request, but allows an IFS customer to list acceptable alternative numbers. However, the IFS customer may have no preference for a specific number, in this case, any number may be assigned from the available unassigned numbers. In order to indicate to the Registrar that the Applicant has no preference for a specific number, the Applicant is to place an asterisk "\*" instead of a number on the request form. The UIFN request form should be accompanied by evidence of payment of the registration application fee for the reservation and assignment of the UIFN by the Registrar and the annual maintenance fee for the current calendar year if the applicant is non ITU-T or ITU-R Sector Member. The ITU will notify Administrations of the amount of the registration application fee in the current Operational Bulletin of the ITU.
+
+A registration application fee and annual maintenance fee can be paid by each Applicant based on the number of projected applications expected. The Registrar debits each Applicant's account for each UIFN Request Form received and requests additional funds for the account when the balance approaches depletion. The advance payment can be made:
+
+- by bank transfer to ITU Account IBAN: CH96 0024 0240 C87655650, UBS SA, Geneva (Switzerland);
+  - major credit card.
+- d) Ensuring that all requested UIFNs are numeric; alpha characters will NOT be accepted.
+  - e) Specifying up to 10 UIFNs, which are acceptable to their IFS customer in order of priority, to limit interaction with the Registrar if their early choices are unavailable.
+  - f) Consulting with the IFS customer for additional choices if the UIFNs are either assigned, reserved, in six-month ageing period, or pending conflict resolution.
+  - g) Accepting the UIFN Request Form, Part B, as the UIFN reservation confirmation from the Registrar, and then notifying the IFS customer.
+  - h) Ensuring that the UIFN is implemented within 180 days and notify the Registrar via the UIFN Status Notification Form, Part A.
+  - i) Upon advice from the Registrar of non-conforming use with this Recommendation the Applicant will be afforded 90 days to either bring the UIFN into conformance or explain why the current use is conforming. If conformance is not achieved by 90 days, the UIFN will be reclaimed by the Registrar. The UIFN will immediately be disconnected and enter the ageing period. The IFS service provider(s) will withdraw the IFS customer's service.
+  - j) Notifying the Registrar of changes in information associated with UIFNs, e.g., change of name, address, using the UIFN Request Form, Part A.
+  - k) Notifying the Registrar via the UIFN Request Form, Part A, of a disconnection of a UIFN.
+
+- l) Receiving advice from the Registrar of confirmation of number assignment via the UIFN, Status Notification Form, Part B, as confirmation of number assignment, and forwarding a copy of this form to their IFS customer.
+- m) Ensuring the payment of an annual maintenance fee.
+
+## Annex B
+
+### Registrar procedures
+
+(This annex forms an integral part of this Recommendation.)
+
+The function of the Registrar will be performed under the auspices of the ITU. The Registrar has the responsibility for the processing, and associated administrative functions, of registration requests from Applicants. The processing of registration requests will be performed in close co-operation and consultation with national Administrations, as required by national Administrations. This Recommendation does not include the legal responsibilities of the Registrar. The Registrar will:
+
+- a) Assign all UIFNs in a fair and unbiased manner.
+- b) Validate the request for a UIFN in accordance with this Recommendation, and the particular UIFN format as described in clause 5. The Registrar shall return request to the Applicant if the application is not valid.
+- c) Administer a single pool of UIFNs in a single database. The database requirements include:
+  - an entry for each UIFN;
+  - the IFS customer name;
+  - the Applicant;
+  - the status of the UIFN (available, reserved, ageing with maturity date);
+  - historical information;
+  - allowing for administering change information;
+  - allow for an online view-only capability of number status to Applicants;
+  - the information necessary to conduct a security investigation, from the UIFN records contained in the Registrar's database, to Administrations (details to be determined by each affected Administration and the ITU-T TSB). This information will be substantiated as being security-based by the agency authorized by the Administration to request the information, and will be provided by the Registrar in a timely and appropriate manner, e.g., as soon as possible, but not later than two days from receipt of the request by the TSB by facsimile or by electronic means.
+- d) Receive all application requests by the Applicant on behalf of the IFS customer by facsimile or email with a UIFN Request Form, Part A. Inclusive payment of the registration application fee and annual maintenance fee.
+- e) Reserve UIFNs on a "first come first served" basis. This means that the UIFN application forms received via facsimile or email by the Registrar will be processed in order of receipt, based on the local time stamp of the Registrar's facsimile or email.
+- f) Register all applications when received, with details of the time and date, using the standard time of the Registrar.
+- g) Determine whether the requested UIFN is available for assignment. If the UIFN requested is unavailable for assignment, the Registrar will see if an alternate UIFN was specified; if not, the Registrar will return the application request to the Applicant to allow another choice.
+- h) Accept no verbal requests or inquiries, for available UIFNs.
+- i) Accept only one IFS customer per UIFN Request Form.
+- j) Respond with a reservation to the Applicant, within two working days of receipt of request, via facsimile or e-mail, with a UIFN Request Form, Part B, to acknowledge the reservation confirmation. Where a request for a specific number is refused or delayed, the Applicant
+
+should be informed of the reason, e.g., assigned, reserved, in six-month ageing period, or pending conflict resolution.
+
+- k) Accept confirmation of service implementation via the UIFN Status Notification Form, Part A, from the Applicant.
+- l) If the UIFN Status Notification Form, Part A, is not received within 180 days, the UIFN is no longer reserved. However, a reasonable extension beyond the 180 days is authorized, at the Registrar's discretion, for compelling reasons, e.g., a service provider inability to complete interconnection with a network operator involved in the IFS service. A reserved UIFN that has not been activated will immediately go back into the pool of numbers available for assignment and no ageing period is required.
+- m) Respond to confirmation of service implementation via the UIFN Status Notification Form, Part B, and assign the UIFN accordingly.
+- n) Update the UIFN database.
+- o) Provide information to Applicants on the application process.
+- p) Upon recognising a non-conforming use, will inform the Applicant of the alleged misuse. The Applicant will be afforded 90 days to either bring the UIFN into conformance or to explain why the current use is conforming. If conformance is not achieved by 90 days, the UIFN will be reclaimed by the Registrar. The UIFN will immediately enter the ageing period. The Registrar will also immediately reclaim a UIFN upon the request of all the Administrations of the countries in which the service is provided when the request is the result of a security investigation.
+- q) Accept notice of disconnection from the Applicant via the UIFN Request Form, Part A. The UIFN will be placed in the ageing period on the date the Registrar receives the notification of disconnect.
+- r) When an existing UIFN is completely disconnected, the UIFN can be assigned to another IFS customer normally after a six-month ageing period. If, however, an Applicant requests the assignment of a UIFN which is in the ageing period, then the UIFN may be assigned if it has been in ageing for at least three months.
+- s) Send confirmation of the disconnection of the UIFN to the Applicant, via the UIFN Status Notification Form, Part B.
+- t) Accept changes of information associated with UIFNs (e.g., change of name, address), via the UIFN Request Form, Part A and UIFN Multiple ROA Notification Form (see Annex G).
+- u) Periodically confirm that assigned UIFNs are in use and exercise authority to take appropriate action regarding inactive UIFNs.
+- v) Monitor and audit the status of the UIFN resource and produce reports to the appropriate Study Group, which shall include actual quantity of numbers assigned and growth statistics associated with those assignments.
+- w) Publish a list of assigned numbers using an agreed method.
+- x) If a UIFN is inadvertently assigned to multiple IFS customers, the Applicant with the earliest dated application will be the Applicant of record.
+- y) Reclaim the number if there is a non-payment of an annual maintenance fee.
+
+## Annex C
+
+### Change request procedures
+
+(This annex forms an integral part of this Recommendation.)
+
+### C.1 Change request procedures
+
+This annex details the procedures that the Registrar, the Applicant, and ROAs are to follow in order for the Registrar to maintain correct customer and ROA information in the UIFN database.
+
+#### C.1.1 Multiple ROAs documentation procedures
+
+- a) The Registrar will maintain within their UIFN database multiple ROAs associated with a single UIFN.
+- b) The Applicant and/or the additional ROAs will provide information on the addition or deletion of ROAs to the Registrar via the UIFN Multiple ROAs Notification Form (see Annex G).
+
+#### C.1.2 Applicant change procedures
+
+- a) If the Registrar receives a Disconnect request from an Applicant and there are other ROAs within the Registrar's database associated with that particular UIFN, then the Registrar will default assign a new Applicant to that UIFN, unless otherwise requested by the IFS customer. The default Applicant will be initially selected by the Registrar based on the earliest registered additional ROA.
+- b) The default Applicant shall notify the Registrar if he accepts the assignment of the Applicant for that particular UIFN. If one of the other ROAs is the customer's choice as its Applicant, then that other ROA shall notify the Registrar with proof of change from that customer.
+- c) If all the other ROAs associated with that UIFN respond back to the Registrar that the UIFN has been disconnected, then the Registrar will place the UIFN in the Ageing state.
+
+#### C.1.3 Change of Applicant
+
+- a) The customer may change Applicants while its UIFN is the Reserved/Assigned Status.
+- b) The new Applicant will notify the Registrar of the change via Annex G.
+- c) The new Applicant will have 180 days to activate the UIFN and must inform the Registrar of service implementation via the UIFN Status Notification Form, Part A.
+- d) Even if the customer transfers to other Applicants, an UIFN can only remain in a reserved status for a maximum of 360 days in order to prevent the misuse of UIFNs. If the customer has changed Applicants, but has not activated the UIFN within the 360 days, the UIFN will be reclaimed by the Registrar.
+
+## Annex D
+
+### Registrar start-up and duplicate request procedures
+
+(This annex forms an integral part of this Recommendation.)
+
+### D.1 Registrar procedures
+
+The purpose of the registrar start-up procedures is to start the assignment of numbers out of the UIFN resource pool in an efficient and fair manner. The administration of UIFNs is divided into two phases:
+
+- 1) start-up phase: receipt and validation of applications;
+- 2) ongoing phase: the administration of the UIFN assignment process after the start-up phase.
+
+NOTE – Although the "start-up phase" is not expected to be required in the future, the text is being retained for historical purposes.
+
+#### D.1.1 Start-up phase
+
+The purpose of the start-up phase is to outline the procedures for receipt and validation of UIFN applications.
+
+The following are the procedures to be adhered to during the start-up phase (see Figure D.1):
+
+- T1 90 days prior to the Registrar's acceptance of applications, the Registrar will announce UIFN availability.
+- T2 30 days prior to the reservation of UIFNs by the Registrar, receipt and validation of UIFN applications will be accomplished. All valid requests received during this time period are considered to be received at the same time to assure that all Applicants can be treated equally.
+- T3 There will be an additional three days after the 30 days acceptance of applications (T2), for the Registrar to amend invalid requests with the Applicants.
+- T4 At expiration of T3, the Registrar will make UIFN assignments and resolve conflict resolutions received during the start-up period.
+
+![Timeline diagram showing the start-up phase procedures. Below the table, two horizontal double-headed arrows indicate time periods. The top arrow, labeled 'First come first served period', spans from the start of T2 to the end of T3. The bottom arrow, labeled 'Validation period', spans from the start of T1 to the end of T3.](96b0240f56d14453b5da05ec30fd5c6e_img.jpg)
+
+| T1                       | T2                         | T3                                     | T4                                                                      |
+|--------------------------|----------------------------|----------------------------------------|-------------------------------------------------------------------------|
+| Advertising notification | Collection of applications | 3-day period to amend invalid requests | Conflict resolution and assigning UIFNs to Applicants received in T1-T3 |
+
+E.169.1(19)\_FD.1
+
+Timeline diagram showing the start-up phase procedures. Below the table, two horizontal double-headed arrows indicate time periods. The top arrow, labeled 'First come first served period', spans from the start of T2 to the end of T3. The bottom arrow, labeled 'Validation period', spans from the start of T1 to the end of T3.
+
+Figure D.1 – Registrar start-up phase procedures
+
+#### D.1.2 Ongoing phase
+
+The ongoing phase of UIFN administration is detailed in clauses 7 and 8. Applications during the ongoing period will be accepted from the first day of T3. However, number reservations will not be made until all conflict resolutions are complete; see clause 9 for details and time-related activities for conflict resolution.
+
+### D.2 Duplicate requests procedures
+
+#### D.2.1 Duplicate requests
+
+The purpose of these procedures is to resolve UIFN conflicts, e.g., when more than one applicant applies for the same UIFN at the same time.
+
+- a) The Registrar should advise only the involved Applicants, and Administrations if so required by those Administrations, when problems are identified, and provide advice to them and co-operate in problem resolution.
+- b) The Registrar shall give priority to those Applicants embedding their IFS customer's existing entire national FSN: this is known as priority assignment. The service provider, which provides the national freephone service, may be different than the applicant that is embedding the IFS customer's FSN in the UIFN.
+
+#### **D.2.2 Specific procedures**
+
+- a) The Applicant can only request and receive priority assignment based on the intent to embed the entire existing FSN. The embedding can only be requested by adding trailing or leading filler digits to the entire existing FSN, in the manner illustrated below.
+
+For example:
+
+- IFS customer A's 7-digit FSN is 234 5678:
+  - embedding by adding leading filler digit: UIFN requested: 800 X2345678;
+  - embedding by adding trailing filler digit: UIFN requested: 800 2345678X;
+- IFS customer B's 6-digit FSN is 654 321:
+  - embedding by adding leading filler digits: UIFN requested: 800 XX654321;
+  - embedding by adding trailing filler digits: UIFN requested: 800 654321XX;
+  - embedding by adding one leading and one trailing digit: UIFN requested: 800 X654321X;
+
+where X = 0-9.
+
+Similar principles apply for IFS customers with fewer than 6-digit FSNs.
+
+- b) When two or more Applicants request the same UIFN, and only one of the Applicants request a priority assignment, the Registrar will assign the UIFN to the Applicant who requested priority assignment. The Registrar will then assign the stated alternative choices, or solicit alternative choices, to the other Applicants.
+- c) When two or more Applicants request the same UIFN based on embedding their entire national FSN, and if only one of the Applicants' national FSN was in service prior to 1 December 1994, and request priority assignment, the Registrar will assign the UIFN to that Applicant. The Registrar will then assign the stated alternative choices, or solicit alternative choices, to the other Applicants.
+- d) When two or more Applicants requesting the same UIFN based on their entire national FSN and two or more of the Applicant's national FSNs were in service prior to 1 December 1994, and request priority assignment, the Registrar will communicate with the Applicants and notify them of the duplicate request and attempt to resolve the duplicate request by having the Applicant(s) change their filler digits to eliminate the duplication. During this procedure, the Registrar will inform the Applicants that they are in contention for their selected UIFN. Identities of other Applicants involved in the contention will only be divulged with the consent of all the involved Applicants, for the purpose of resolving the contention.
+- e) When two or more Applicants requesting the same UIFN based on their entire national FSN, request priority assignment, the Registrar will communicate with the Applicants and notify them of the duplicate request and attempt to resolve the duplicate request by having the Applicant(s) change their filler digits to eliminate the duplication. During this procedure, the Registrar will inform the Applicants that they are in contention for their selected UIFN. Identities of other Applicants involved in the contention will only be divulged with the consent of all the involved Applicants, for the purpose of resolving the contention.
+
+- f) When two or more Applicants requested the same UIFN, and none have requested priority assignment, the Registrar will communicate with the Applicants and notify them of the duplicate request and attempt to resolve the duplicate request by having the Applicant(s) choose an alternate UIFN if applicable. During this procedure, the Registrar will inform the Applicants that they are in contention for their selected UIFN. Identities of other Applicants involved in the contention will only be divulged with the consent of all the involved Applicants, for the purpose of resolving the contention.
+- g) In the absence of an agreement to resolve the duplicate request with the Applicants, the Registrar will, after 15 days, perform a random selection to resolve the duplicate request. The Applicants not receiving the UIFN will be assigned one of their alternate choices or the Registrar will solicit another choice, if not provided.
+
+## Annex E
+
+### Preparation of Universal International Freephone Number Request Form
+
+(This annex forms an integral part of this Recommendation.)
+
+### E.1 Preparation of Universal International Freephone Number Request Form – Part A
+
+The Universal International Freephone Number request form, Part A, is completed by the Applicant. The fields are as follows:
+
+- a) Transmittal date: date the form was sent.
+- b) Company name (Applicant): as defined in 3.2.2.
+- c) Contact name and address: the contact name and address of the Applicant.
+- d) Telephone, fax numbers, and e-mail address: the telephone, fax numbers and e-mail address of the Applicant.
+- e) Request type:
+  - **new**: a new service involving a new UIFN is established, or an additional service provider will be providing IFS service with the existing number to the IFS customer;
+  - **change**: an existing service requires modification (i.e., change of name, or address);
+  - **disconnect**: an existing service is completely disconnected. The number can be assigned to another IFS customer only after a six-month ageing period;
+  - **cancel**: the service does not exist yet, and the IFS customer decides not to use this number, the number automatically goes into the pool of available numbers for immediate assignment.
+- f) Reason for change: indicate the type of change.
+- g) Universal International Freephone Number: indicate either:
+  - IFS customer requests one of the numbers listed below (in order of preference); or
+  - IFS customer requests any available number with no specific preference.
+- h) IFS customer name and address: name of IFS customer required, address of customer optional.
+- i) Expected due date: service will be expected to officially commence on this date.
+- j) Is IFS customer embedding entire existing national FSN?
+- k) Existing national FSN that is being embedded and the CC under which this FSN is in use.
+- l) Was existing national FSN implemented prior to 1 December 1994?
+- m) Countries with which the UIFN will be initially implemented.
+- n) Co-ordination (reference) number: a reference number assigned by the service provider to identify the number request. This number should be used as a cross-reference on the Universal International Freephone Number Request Form, and the Universal International Freephone Number Status Notification Form.
+- o) Payment of the registration application fee and annual maintenance fee: Indicate the method of payment used.
+
+### E.2 Preparation of Universal International Freephone Number Request Form – Part B
+
+The Universal International Freephone Number Request Form, Part B, is completed by the Registrar to confirm UIFN reservation. The fields are as follows:
+
+- a) Transmittal date: date the form was sent.
+
+- b) Universal International Freephone Number: the number reserved, based on its priority and availability, subject to the payment of the registration application fee and annual maintenance fee.
+- c) Reason for number denial: when a request for a specific number is refused, the Applicant should be informed of the reason for each number listed in Part A of the UIFN Request Form, for example:
+  - assigned;
+  - reserved;
+  - in a six-month ageing period;
+  - pending conflict resolution.
+
+## Universal International Freephone Number request form
+
+**Part A filled out by the Applicant**
+
+(Applicant):  
+ Company name: (b)   
+ Contact name: (c)   
+ Address:   
+ Telephone number: (d)   
+ Fax number:   
+ E-mail:
+
+Transmittal date: (a)   
+ Send to:  
+ UIFN Registrar  
+ International Telecommunication Union  
+ Telecommunication Standardization Bureau  
+ CH-1211 GENEVA 20, Switzerland  
+ Fax: +41 22 730 6200  
+ Tel: +41 22 730 6220  
+ E-mail: [universalnumbers@itu.int](mailto:universalnumbers@itu.int)
+
+Request type (mark with an X): (e) 
+ New  
+ Change  
+ Disconnect  
+ Cancel
+
+Reason for change: (f)
+
+Universal International Freephone Number Requests, acceptable alternatives in order of priority: (g)
+
+1) +800   
+ 2) +800   
+ 3) +800   
+ 4) +800   
+ 5) +800
+
+6) +800   
+ 7) +800   
+ 8) +800   
+ 9) +800   
+ 10) +800
+
+IFS customer name: (h) 
+ Expected IFS customer due date: (i)
+
+IFS customer address:
+
+Is IFS customer embedding entire existing national FSN? (j) 
+ Yes  
+ No
+
+Existing national FSN that is being embedded: (k) CC FSN
+
+Existing national FSN implemented prior to 1 December 1994 (l) 
+ Yes  
+ No
+
+Country(ies) with which the IFS will be implemented initially: (m)
+
+Co-ordination (reference) number: (n)
+
+Payment of the registration application fee: (o) Swiss francs
+
+Payment of the annual maintenance fee: (o) (for non ITU-T or ITU-R Sector Member) Swiss francs
+
+Specify the method of payment use:
+
+- [ ] – by bank transfer to: UBS Switzerland AG; Bank address : Case postale, 1211 Geneva 2;
+- Account holder: Union internationale des télécommunications;
+- IBAN: CH96 0024 0240 C876 5565 0
+- Account number: 0240-C8765565.0; Swift: UBSWCHZH80A; Bank clearing: 0240
+- [ ] – deduction from the applicant's prepaid account
+- [ ] – major credit card
+
+**Part B filled out by the Registrar to be returned to Applicant** Transmittal date: (a)
+
+This UIFN is reserved for 180 days: (b) +800
+
+The UIFN(s) listed above in Part A, were denied reservation, with reason: (c)
+
+1)   
+ 2)   
+ 3)   
+ 4)   
+ 5)
+
+6)   
+ 7)   
+ 8)   
+ 9)   
+ 10)
+
+Remarks:
+
+Signature:
+
+**Rec. ITU-T E.169.1 (02/2019)** 15
+
+## Annex F
+
+### Preparation of Universal International Freephone Number Status Notification Form
+
+(This annex forms an integral part of this Recommendation.)
+
+### F.1 Preparation of Universal International Freephone Number Status Notification Form – Part A
+
+The Universal International Freephone Number Status Notification Form, Part A, is completed by the Applicant to change the reserved UIFN to assigned. The fields are as follows:
+
+- a) Transmittal date: date the form was sent.
+- b) Company name (Applicant): as defined in clause 3.2.2.
+- c) Contact name and address: the contact name and address of the Applicant.
+- d) Telephone, fax numbers and e-mail address: the telephone, fax numbers and e-mail address of the Applicant.
+- e) Universal International Freephone Number.
+- f) Date of activation: the date that the first number was activated in their network.
+- g) Co-ordination (reference) number: a reference number assigned by the service provider to identify the number request. This number should be used as a cross-reference on the Universal International Freephone Number Request Form, and the Universal International Freephone Number Status Notification Form.
+- h) IFS customer name: name of IFS customer and address (optional field).
+
+### F.2 Preparation of Universal International Freephone Number Status Notification Form – Part B
+
+The Universal International Freephone Number Status Notification Form, Part B, is completed by the Registrar to confirm the freephone assignment to Applicant. The fields are as follows:
+
+- a) Transmittal date: date the form was sent.
+- b) Universal International Freephone Number: the UIFN, which the Registrar has changed from, reserved, to assigned, from assigned to disconnected, or updated change information.
+
+#### **Universal International Freephone Number Status Notification Form**
+
+##### **Part A filled out by the Applicant**
+
+Transmittal date: (a) \_\_\_\_\_
+
+(Applicant): \_\_\_\_\_
+
+Send to: \_\_\_\_\_
+
+Company name: (b) \_\_\_\_\_
+
+UIFN Registrar
+
+Contact name: (c) \_\_\_\_\_
+
+International Telecommunication Union
+
+Address: \_\_\_\_\_
+
+Telecommunication Standardization Bureau
+
+CH-1211 GENEVA 20, Switzerland
+
+Telephone number: (d) \_\_\_\_\_
+
+Fax: +41 22 730 6200
+
+Fax number: \_\_\_\_\_
+
+Tel: +41 22 730 6220
+
+E-mail: \_\_\_\_\_
+
+The following UIFN was implemented: (e)
+
++800 \_\_\_\_\_
+
+The date of activation is: (f) \_\_\_\_\_
+
+Day
+
+Month
+
+Year
+
+Co-ordination (reference) number: (g) \_\_\_\_\_
+
+IFS customer name: (h) \_\_\_\_\_
+
+Customer address: \_\_\_\_\_
+
+##### **Part B filled out by the Registrar to be returned to Applicant**
+
+The below UIFN was assigned: \_\_\_\_\_
+
+Transmittal date: (a) \_\_\_\_\_
+
+(b) +800 \_\_\_\_\_
+
+The below UIFN was disconnected  or cancelled : \_\_\_\_\_
+
+(b) +800 \_\_\_\_\_
+
+Remarks: \_\_\_\_\_
+
+Signature: \_\_\_\_\_
+
+## Annex G
+
+### Preparation of UIFN Multiple RoAs Notification Form
+
+(This annex forms an integral part of this Recommendation.)
+
+### G.1 Preparation of UIFN Multiple ROAs Notification Form – Part A
+
+The Universal International Freephone Number Multiple ROAs Notification Form is to be completed by the Applicant or additional ROAs to report additions or deletions of ROAs to the Registrar. The fields are as follows:
+
+- a) Transmittal date: date the form was sent to the Registrar.
+- b) Company Name/ROA: ROA name and contact information.
+- c) UIFN number: specific UIFN number associated with this request.
+- d) IFS customer name: the exact name of the IFS customer. The registrar will not record any change of information if the customer's name is not the same as the one recorded in the registrar's database.
+- e) Customer address: this is an optional field. If included, it should be the address of the main office of the IFS customer or the address recorded in the Registrar's database.
+- f) UIFN status: indicate whether the UIFN has been implemented or was disconnected.
+- g) Reasons: provide any comments deemed necessary.
+
+### G.2 Preparation of UIFN Multiple ROAs Notification Form – Part B
+
+The UIFN Multiple ROAs Notification Form is completed by the Registrar to confirm the premium rate number assignment/disconnect for the additional ROA(s). The fields are as follows:
+
+- a) Transmittal date: date the form was sent.
+- b) Universal International Free Phone Number: the UIFN that the Registrar has changed from "reserved", to "assigned", and from "assigned" to "disconnected" or "updated change information".
+
+
+
+## Appendix I
+
+### Applicant procedure
+
+(This appendix does not form an integral part of this Recommendation.)
+
+![Flowchart of the Applicant procedure for UIFN registration.](90ddb84c323b956e2d50a54d3f870566_img.jpg)
+
+```
+graph TD; Idle1([Idle]) --> Request{Request for UIFN received from Subscriber}; Request --> Valid{Request valid?}; Valid -- No --> Consult[Consult Subscriber]; Consult --> Alternate{Can alternate request be made?}; Alternate -- Yes --> Request; Alternate -- No --> Idle2([Idle]); Valid -- Yes --> Process[Process request]; Process --> Transmit{Transmit request for UIFN to Registrar on behalf of Subscriber}; Transmit --> Returned{Application returned?}; Returned -- Yes --> Inform[Inform Subscriber UIFN is not available]; Returned -- No --> Available{Is UIFN available?}; Available -- No --> Inform; Available -- Yes --> Confirm[Process Reservation Confirmation of UIFN for Subscriber]; Confirm --> Idle2; Inform --> Idle2;
+```
+
+The flowchart illustrates the applicant procedure for UIFN registration. It begins with an 'Idle' state, followed by the receipt of a 'Request for UIFN received from Subscriber'. A decision point 'Request valid?' follows. If 'No', the process moves to 'Consult Subscriber', which leads to another decision 'Can alternate request be made?'. If 'Yes', it loops back to the request receipt. If 'No', it ends at 'Idle'. If 'Yes' at the first decision, it proceeds to 'Process request', then 'Transmit request for UIFN to Registrar on behalf of Subscriber'. A decision 'Application returned?' follows. If 'Yes', it goes to 'Inform Subscriber UIFN is not available'. If 'No', it goes to 'Is UIFN available?'. If 'No' here, it also goes to 'Inform Subscriber UIFN is not available'. If 'Yes', it proceeds to 'Process Reservation Confirmation of UIFN for Subscriber', which then leads to the final 'Idle' state. Both 'Inform Subscriber UIFN is not available' and 'Process Reservation Confirmation of UIFN for Subscriber' lead to the final 'Idle' state.
+
+Flowchart of the Applicant procedure for UIFN registration.
+
+E.169.1(19)\_FI.1
+
+The text within this Recommendation will take precedence over the flow diagrams in Appendices I, II and III if any discrepancies are identified.
+
+## Appendix II
+
+### Registrar procedure
+
+(This appendix does not form an integral part of this Recommendation.)
+
+![Flowchart of Registrar procedure](2ae3eae1bd80a90f192f568ae246a9a6_img.jpg)
+
+```
+
+graph TD
+    Idle1([Idle]) --> Req[Request for UIFN received from Applicant]
+    Req --> Valid{Request valid?}
+    Valid -- No --> Return[Return application to Applicant]
+    Valid -- Yes --> Avail{Is UIFN available?}
+    
+    Avail -- No --> Alt{Is alternate UIFN specified?}
+    Alt -- No --> InformNotAvail[Inform Applicant UIFN is not available]
+    Alt -- Yes --> Conn1((1  
+App. III))
+    Conn1 --> Avail
+    
+    Avail -- Yes --> Conflict{Is UIFN in conflict?}
+    Conflict -- Yes --> Conn2((2  
+App. III))
+    Conflict -- No --> MarkRes[Mark UIFN "reserved" for Subscriber]
+    
+    MarkRes --> Conn3((3  
+App. III))
+    MarkRes --> InformRes[Inform Applicant UIFN is reserved]
+    InformRes --> StartTimer[Start reservation time (180 days)]
+    StartTimer --> Expired{Reservation timer expired?}
+    
+    Expired -- Yes --> InformCan[Inform Applicant reservation is cancelled]
+    Expired -- No --> ActRec[Activation notification received]
+    
+    ActRec --> MarkAssigned[Mark UIFN as assigned]
+    MarkAssigned --> StopTimer[Stop Reservation Timer]
+    StopTimer --> InformAssigned[Inform Applicant that UIFN is assigned]
+    
+    Return --> Idle2([Idle])
+    InformNotAvail --> Idle2
+    InformCan --> Idle2
+    InformAssigned --> Idle2
+  
+```
+
+The flowchart illustrates the Registrar procedure for UIFN allocation. It begins with an 'Idle' state, followed by a 'Request for UIFN received from Applicant'. A decision 'Request valid?' follows. If 'No', the application is returned to the applicant. If 'Yes', it checks 'Is UIFN available?'. If 'No', it checks 'Is alternate UIFN specified?'. If 'No', it informs the applicant that the UIFN is not available. If 'Yes', it loops back via connector '1 (App. III)' to check availability again. If 'Is UIFN available?' is 'Yes', it checks 'Is UIFN in conflict?'. If 'Yes', it leads to connector '2 (App. III)'. If 'No', it marks the UIFN as 'reserved' for the subscriber (also outputting to connector '3 (App. III)'), informs the applicant, and starts a 180-day reservation timer. If the timer expires (Yes), it informs the applicant that the reservation is cancelled. If not (No), it waits for an 'Activation notification received'. Once received, it marks the UIFN as 'assigned', stops the reservation timer, and informs the applicant that the UIFN is assigned. All terminal paths lead back to the 'Idle' state.
+
+Flowchart of Registrar procedure
+
+E.169.1(19)\_FII.1
+
+## Appendix III
+
+### Duplicate request procedure
+
+(This appendix does not form an integral part of this Recommendation.)
+
+![Flowchart of the Duplicate request procedure](9c1d3678db4a12d5864cb2a4def1135d_img.jpg)
+
+```
+graph TD; Start((2 (App. II))) --> Q1{Any priority requests?}; Q1 -- No --> Inform[Inform applicant UIFN is in conflict]; Inform --> Q2{Involved applicants agree to divulge entities?}; Q1 -- Yes --> Q3{Only one priority request?}; Q3 -- Yes --> Q4{Is applicant the one with priority?}; Q3 -- No --> Q5{For each application is this a priority request?}; Q4 -- Yes --> End1((1 (App. II))); Q4 -- No --> End3((3 (App. II))); Q5 -- No --> End1; Q5 -- Yes --> Inform; Q2 -- Yes --> Negotiate1[Applicants negotiate with each other]; Q2 -- No --> Negotiate2[Applicants negotiate through registrar]; Negotiate1 --> Q6{Conflict resolved?}; Negotiate2 --> Q6; Q6 -- Yes --> Q7{Applicant receives UIFN?}; Q6 -- No --> Random[Perform random selection]; Random --> Q7; Q7 -- Yes --> End3; Q7 -- No --> End1;
+```
+
+The flowchart illustrates the 'Duplicate request procedure'. It begins at node '2 (App. II)' and proceeds to a decision diamond 'Any priority requests?'. If 'No', it goes to 'Inform applicant UIFN is in conflict', which then leads to 'Involved applicants agree to divulge entities?'. If 'Yes' to 'Any priority requests?', it goes to 'Only one priority request?'. If 'Yes', it goes to 'Is applicant the one with priority?'. If 'Yes', it ends at '1 (App. II)'; if 'No', it ends at '3 (App. II)'. If 'No' to 'Only one priority request?', it goes to 'For each application is this a priority request?'. If 'No', it ends at '1 (App. II)'; if 'Yes', it goes to 'Inform applicant UIFN is in conflict'. From 'Involved applicants agree to divulge entities?', if 'Yes', it goes to 'Applicants negotiate with each other'; if 'No', it goes to 'Applicants negotiate through registrar'. Both lead to 'Conflict resolved?'. If 'Yes', it goes to 'Applicant receives UIFN?'. If 'Yes', it ends at '3 (App. II)'; if 'No', it ends at '1 (App. II)'. If 'No' to 'Conflict resolved?', it goes to 'Perform random selection', which then leads to 'Applicant receives UIFN?'.
+
+Flowchart of the Duplicate request procedure
+
+E.169.1(19)\_FIII.1
+
+
+
+# SERIES OF ITU-T RECOMMENDATIONS
+
+|                 |                                                                                                                                                           |
+|-----------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Series A        | Organization of the work of ITU-T                                                                                                                         |
+| Series D        | Tariff and accounting principles and international telecommunication/ICT economic and policy issues                                                       |
+| <b>Series E</b> | <b>Overall network operation, telephone service, service operation and human factors</b>                                                                  |
+| Series F        | Non-telephone telecommunication services                                                                                                                  |
+| Series G        | Transmission systems and media, digital systems and networks                                                                                              |
+| Series H        | Audiovisual and multimedia systems                                                                                                                        |
+| Series I        | Integrated services digital network                                                                                                                       |
+| Series J        | Cable networks and transmission of television, sound programme and other multimedia signals                                                               |
+| Series K        | Protection against interference                                                                                                                           |
+| Series L        | Environment and ICTs, climate change, e-waste, energy efficiency; construction, installation and protection of cables and other elements of outside plant |
+| Series M        | Telecommunication management, including TMN and network maintenance                                                                                       |
+| Series N        | Maintenance: international sound programme and television transmission circuits                                                                           |
+| Series O        | Specifications of measuring equipment                                                                                                                     |
+| Series P        | Telephone transmission quality, telephone installations, local line networks                                                                              |
+| Series Q        | Switching and signalling, and associated measurements and tests                                                                                           |
+| Series R        | Telegraph transmission                                                                                                                                    |
+| Series S        | Telegraph services terminal equipment                                                                                                                     |
+| Series T        | Terminals for telematic services                                                                                                                          |
+| Series U        | Telegraph switching                                                                                                                                       |
+| Series V        | Data communication over the telephone network                                                                                                             |
+| Series X        | Data networks, open system communications and security                                                                                                    |
+| Series Y        | Global information infrastructure, Internet protocol aspects, next-generation networks, Internet of Things and smart cities                               |
+| Series Z        | Languages and general software aspects for telecommunication systems                                                                                      |

marked/E/T-REC-E.169.3-200010-I_PDF-E/raw.md

@@ -0,0 +1,841 @@
+
+
+![ITU logo: A globe with a lightning bolt and the letters ITU.](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg)
+
+ITU logo: A globe with a lightning bolt and the letters ITU.
+
+INTERNATIONAL TELECOMMUNICATION UNION
+
+**ITU-T**
+
+**E.169.3**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+(09/2000)
+
+SERIES E: OVERALL NETWORK OPERATION,  
+TELEPHONE SERVICE, SERVICE OPERATION AND  
+HUMAN FACTORS
+
+International operation – Numbering plan of the  
+international telephone service
+
+---
+
+**Application of Recommendation E.164  
+numbering plan for universal international  
+shared cost numbers for the international  
+shared cost service**
+
+ITU-T Recommendation E.169.3
+
+(Formerly CCITT Recommendation)
+
+---
+
+# **OVERALL NETWORK OPERATION, TELEPHONE SERVICE, SERVICE OPERATION AND HUMAN FACTORS**
+
+|                                                                                                          |                    |
+|----------------------------------------------------------------------------------------------------------|--------------------|
+| <b>INTERNATIONAL OPERATION</b>                                                                           |                    |
+| Definitions                                                                                              | E.100–E.103        |
+| General provisions concerning Administrations                                                            | E.104–E.119        |
+| General provisions concerning users                                                                      | E.120–E.139        |
+| Operation of international telephone services                                                            | E.140–E.159        |
+| <b>Numbering plan of the international telephone service</b>                                             | <b>E.160–E.169</b> |
+| International routing plan                                                                               | E.170–E.179        |
+| Tones in national signalling systems                                                                     | E.180–E.189        |
+| Numbering plan of the international telephone service                                                    | E.190–E.199        |
+| Maritime mobile service and public land mobile service                                                   | E.200–E.229        |
+| <b>OPERATIONAL PROVISIONS RELATING TO CHARGING AND ACCOUNTING IN THE INTERNATIONAL TELEPHONE SERVICE</b> |                    |
+| Charging in the international telephone service                                                          | E.230–E.249        |
+| Measuring and recording call durations for accounting purposes                                           | E.260–E.269        |
+| <b>UTILIZATION OF THE INTERNATIONAL TELEPHONE NETWORK FOR NON-TELEPHONY APPLICATIONS</b>                 |                    |
+| General                                                                                                  | E.300–E.319        |
+| Phototelegraphy                                                                                          | E.320–E.329        |
+| <b>ISDN PROVISIONS CONCERNING USERS</b>                                                                  | <b>E.330–E.349</b> |
+| <b>INTERNATIONAL ROUTING PLAN</b>                                                                        | <b>E.350–E.399</b> |
+| <b>NETWORK MANAGEMENT</b>                                                                                |                    |
+| International service statistics                                                                         | E.400–E.409        |
+| International network management                                                                         | E.410–E.419        |
+| Checking the quality of the international telephone service                                              | E.420–E.489        |
+| <b>TRAFFIC ENGINEERING</b>                                                                               |                    |
+| Measurement and recording of traffic                                                                     | E.490–E.505        |
+| Forecasting of traffic                                                                                   | E.506–E.509        |
+| Determination of the number of circuits in manual operation                                              | E.510–E.519        |
+| Determination of the number of circuits in automatic and semi-automatic operation                        | E.520–E.539        |
+| Grade of service                                                                                         | E.540–E.599        |
+| Definitions                                                                                              | E.600–E.649        |
+| Traffic engineering for IP-networks                                                                      | E.650–E.699        |
+| ISDN traffic engineering                                                                                 | E.700–E.749        |
+| Mobile network traffic engineering                                                                       | E.750–E.799        |
+| <b>QUALITY OF TELECOMMUNICATION SERVICES: CONCEPTS, MODELS, OBJECTIVES AND DEPENDABILITY PLANNING</b>    |                    |
+| Terms and definitions related to the quality of telecommunication services                               | E.800–E.809        |
+| Models for telecommunication services                                                                    | E.810–E.844        |
+| Objectives for quality of service and related concepts of telecommunication services                     | E.845–E.859        |
+| Use of quality of service objectives for planning of telecommunication networks                          | E.860–E.879        |
+| Field data collection and evaluation on the performance of equipment, networks and services              | E.880–E.899        |
+
+*For further details, please refer to the list of ITU-T Recommendations.*
+
+# **Application of Recommendation E.164 numbering plan for universal international shared cost numbers for the international shared cost service**
+
+## **Summary**
+
+This Recommendation details the application of the Recommendation E.164 Numbering Plan for Universal International Shared Cost Numbers (UISCN) in the provisioning of the International Shared Cost Service (ISCS) as defined in ITU-T Recommendation E.154.
+
+###### **Source**
+
+ITU-T Recommendation E.169.3 was prepared by ITU-T Study Group 2 (1997-2000) and approved by the World Telecommunication Standardization Assembly (Montreal, 27 September – 6 October 2000).
+
+## FOREWORD
+
+The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis.
+
+The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics.
+
+The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1.
+
+In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC.
+
+### NOTE
+
+In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+### INTELLECTUAL PROPERTY RIGHTS
+
+ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process.
+
+As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database.
+
+© ITU 2001
+
+All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU.
+
+## CONTENTS
+
+|       |                                                                                                | Page |
+|-------|------------------------------------------------------------------------------------------------|------|
+| 1     | Scope.....                                                                                     | 1    |
+| 2     | References.....                                                                                | 1    |
+| 3     | Definitions .....                                                                              | 1    |
+| 4     | Abbreviations.....                                                                             | 2    |
+| 5     | UISCN principles and format .....                                                              | 2    |
+| 5.1   | UISCN principles.....                                                                          | 2    |
+| 5.2   | UISCN format.....                                                                              | 3    |
+| 6     | Number assignment principles.....                                                              | 3    |
+| 7     | Applicant procedures .....                                                                     | 3    |
+| 8     | Registrar procedures .....                                                                     | 4    |
+| 9     | Change request procedures .....                                                                | 4    |
+| 10    | Registrar start-up and duplicate request procedures .....                                      | 4    |
+| 11    | Preparation of Universal International Shared Cost Number Request Form.....                    | 4    |
+| 12    | Preparation of Universal International Shared Cost Number Status Notification Form.....        | 4    |
+| 13    | Preparation of Universal International Shared Cost Number Multiple ROA Notification Form ..... | 4    |
+|       | Annex A – Applicant procedures.....                                                            | 4    |
+|       | Annex B – Registrar procedures .....                                                           | 5    |
+|       | Annex C – Change request procedures .....                                                      | 7    |
+| C.1   | Multiple ROAs documentation procedures .....                                                   | 7    |
+| C.2   | Applicant change procedures.....                                                               | 8    |
+| C.3   | Change of Applicant .....                                                                      | 8    |
+|       | Annex D – Registrar start-up and duplicate request procedures.....                             | 8    |
+| D.1   | Registrar procedures .....                                                                     | 8    |
+| D.1.1 | Start-up phase .....                                                                           | 8    |
+| D.1.2 | Ongoing phase .....                                                                            | 9    |
+| D.2   | Duplicate requests procedures .....                                                            | 9    |
+| D.2.1 | Duplicate requests.....                                                                        | 9    |
+| D.2.2 | Specific procedures.....                                                                       | 9    |
+|       | Annex E – Preparation of Universal International Shared Cost Number Request Form.....          | 10   |
+| E.1   | Preparation of UISCN Request Form, Part A .....                                                | 10   |
+
+|                                                                                                             | <b>Page</b> |
+|-------------------------------------------------------------------------------------------------------------|-------------|
+| E.2    Preparation of UISCN Request Form, Part B .....                                                      | 11          |
+| Annex E (Form) – Universal International Shared Cost Number Request Form .....                              | 12          |
+| Annex F – Preparation of Universal International Shared Cost Number Status Notification<br>Form.....        | 13          |
+| F.1    Preparation of UISCN Status Notification Form, Part A.....                                           | 13          |
+| F.2    Preparation of UISCN Status Notification Form, Part B.....                                           | 13          |
+| Annex F (Form) – Universal International Shared Cost Number Status Notification Form ...                    | 14          |
+| Annex G – Preparation of Universal International Shared Cost Number Multiple ROA<br>Notification Form ..... | 15          |
+| G.1    Preparation of UISCN Multiple ROA Notification Form, Part A .....                                    | 15          |
+| G.2    Preparation of UISCN Multiple ROA Notification Form, Part B.....                                     | 15          |
+| Annex G (Form) – Universal International Shared Cost Number Multiple ROA<br>Notification Form .....         | 16          |
+| Appendix I – Applicant procedure.....                                                                       | 17          |
+| Appendix II – Registrar procedure.....                                                                      | 18          |
+| Appendix III – Duplicate request procedure .....                                                            | 19          |
+
+## ITU-T Recommendation E.169.3
+
+# Application of Recommendation E.164 numbering plan for universal international shared cost numbers for the international shared cost service
+
+(Montreal, 2000)
+
+## 1 Scope
+
+This Recommendation details the application of the Recommendation E.164 Numbering Plan for Universal International Shared Cost Numbers (UISCN) in the provisioning of the International Shared Cost Service (ISCS) as defined in ITU-T Recommendation E.154.
+
+## 2 References
+
+The following Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; all users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published.
+
+- ITU-T Recommendation E.154 (1998), *International shared cost service*.
+- ITU-T Recommendation E.164 (1997), *The international public telecommunication numbering plan*.
+- ITU-T Recommendation E.164.1 (1998), *Criteria and procedures for the reservation, assignment, and reclamation of E.164 country codes and associated Identification Codes (ICs)*.
+- ITU-T Recommendation E.190 (1997), *Principles and responsibilities for the management, assignment and reclamation of e-series international numbering resources*.
+
+## 3 Definitions
+
+This Recommendation defines the following terms:
+
+**3.1 ageing period:** A six-month period of time when a previously assigned UISCN remains idle before being reassigned.
+
+**3.2 applicant:** The service provider, an ROA, as defined in the Annex of the ITU Constitution (Geneva, 1992) that submits an application for a Global Subscriber Number (GSN) of the UISCN on behalf of the ISCS customer in accordance with this ITU-T Recommendation.
+
+**3.3 ISCS service provider:** The ROA which provides the ISCS.
+
+**3.4 number embedding:** A method by which an ISCS customer's existing national shared cost number is integrated as part of the GSN portion of the new UISCN.
+
+**3.5 national shared cost number:** The existing national shared cost number (or portion of) that will be embedded in the UISCN.
+
+**3.6 registrar:** The Administrator responsible for processing registration requests, and assignment of the GSN portion of the UISCN in accordance with this ITU-T Recommendation.
+
+**3.7 ISCS customer:** The individual or entity that obtains a UISCN from an ISCS service provider(s).
+
+**3.8 universal international shared cost number:** The Universal International Shared Cost Number (UISCN) is a unique number assigned to an Applicant for its ISCS customer that is the same throughout the world. A UISCN is composed of a 3-digit CC (808) for a global service application and an 8-digit GSN.
+
+## **4 Abbreviations**
+
+This Recommendation uses the following abbreviations:
+
+|       |                                            |
+|-------|--------------------------------------------|
+| CC    | Country Code                               |
+| GSN   | Global Subscriber Number                   |
+| ISCS  | International Shared Cost Service          |
+| ROA   | Recognized Operating Agency                |
+| SCN   | Shared Cost Number                         |
+| SN    | Subscriber Number                          |
+| TSB   | Telecommunication Standardization Bureau   |
+| UISCN | Universal International Shared Cost Number |
+
+## **5 UISCN principles and format**
+
+### **5.1 UISCN principles<sup>1</sup>**
+
+The following principles were used in the development of the UISCN format and assignment procedures, and should be considered with the use of UISCNs.
+
+**5.1.1** To ensure full ISCS customer flexibility, the UISCN should be portable, giving the ISCS customers the ability to retain their assigned UISCNs and change their service providers. The GSN portion of the UISCN does not contain any identification of country (origin or destination), administrative code or service provider code.
+
+**5.1.2** The structure of the UISCN should offer ISCS customers freedom in choosing the digits to form a particular UISCN that suits their purposes.
+
+**5.1.3** The treatment of all UISCNs related activities, among nations, ISCS service providers and ISCS customers should be fair and unbiased.
+
+---
+
+<sup>1</sup> Reference should also be made to ITU-T Recommendation E.190.
+
+### 5.2 UISCN format
+
+A UISCN is composed of a 3-digit CC (808) for a global service application and an 8-digit Global Subscriber Number (GSN), resulting in an 11-digit fixed format<sup>2</sup> (see Figure 1):
+
+![Diagram of UISCN format showing the combination of a 3-digit CC (808) and an 8-digit GSN to form an 11-digit UISCN.](562f471e8153729557e6a4ee6343c32c_img.jpg)
+
+The diagram illustrates the structure of a UISCN. It shows two boxes: the first contains '808' with '3 digits' written below it, and the second contains 'GSN' with '8 digits' written below it. A dashed arrow points from the GSN box to the text 'Global Subscriber Number (GSN)'. A longer dashed arrow points from the 808 box to the text 'Universal International Shared Cost Number (UISCN)'.
+
+Diagram of UISCN format showing the combination of a 3-digit CC (808) and an 8-digit GSN to form an 11-digit UISCN.
+
+**Figure 1/E.169.3**
+
+As an example, an ISCS customer's UISCN could be 808 12345678, where 12345678 is the ISCS customer's GSN.
+
+All calls to a UISCN must be preceded by an international prefix.
+
+## 6 Number assignment principles<sup>3</sup>
+
+6.1 All assigned UISCNs must be used in conformance with ITU-T Recommendation E.154.
+
+6.2 Applications for UISCNs will only be considered when a valid (see 6.3 and 6.4) and complete UISCN Request Form has been received from an eligible Applicant by the Registrar.
+
+6.3 UISCNs will be assigned to ISCS customers who will use the ISCS service between two or more countries, i.e. ISCS customers offering a service that is only accessed from within a single national, or integrated numbering plan, will not be considered eligible.
+
+6.4 UISCNs can only be assigned to ISCS customers where implementation will be within 180 days of the date of reservation.
+
+6.5 The assignment of a UISCN by the Registrar does not create an ownership interest, right or claim to the UISCN on the part of the ISCS customer or ISCS service provider. Its use shall be subject to the terms set forth herein.
+
+6.6 UISCNs may not be sold, licensed, or traded. Nor may they be transferred, except in the case of a merger, acquisition or joint venture. Any such transfer shall be notified to the Registrar within 30 days.
+
+6.7 UISCNs are classified as reserved until the Applicant notifies the Registrar that the UISCN is implemented (180 day maximum).
+
+6.8 The UISCN shall be unique to an ISCS customer.
+
+6.9 Any violation of these principles by the ISCS customer or ISCS service provider of a UISCN will result in the Registrar reclaiming the assigned number.
+
+## 7 Applicant procedures
+
+The procedures which the Applicant is to follow are contained in Annex A.
+
+<sup>2</sup> Service Providers should be aware that more than 12 digits may be dialled for commercial reasons. Commercial advertisements may contain more letters than the comparable digits in a telephone number and be inadvertently dialled by a customer. These calls should not be blocked for that reason.
+
+<sup>3</sup> Reference should also be made to ITU-T Recommendation E.164 and E.164.1.
+
+## **8 Registrar procedures**
+
+The procedures which the Registrar is to follow are contained in Annex B.
+
+## **9 Change request procedures**
+
+The procedures which the Registrar, the Applicant, and ROAs are to follow in order for the Registrar to maintain correct customer and ROA information in the UISCN database are contained in Annex C.
+
+## **10 Registrar start-up and duplicate request procedures**
+
+The Registrar start-up procedures and duplicate request procedures which were used are in Annex D.
+
+## **11 Preparation of Universal International Shared Cost Number Request Form**
+
+The procedure for preparation of the Universal International Shared Cost Number Request Form is included in Annex E.
+
+## **12 Preparation of Universal International Shared Cost Number Status Notification Form**
+
+The procedure for preparation of the Universal International Shared Cost Number Status Notification Form is included in Annex F.
+
+## **13 Preparation of Universal International Shared Cost Number Multiple ROA Notification Form**
+
+The procedure for preparation of the Universal International Shared Cost Numbered Multiple ROA Notification Form is included in Annex G. An Applicant may have an ISCS customer who may also be an ISCS customer of one or more ROAs in different countries or for other service reasons
+
+## **ANNEX A**
+
+### **Applicant procedures**
+
+The Applicant has the responsibility for the following:
+
+- a) processing all applications received on behalf of their ISCS customers, and of being the sole interface with the ISCS customer.
+
+NOTE 1 – National Administrations may, as a national matter, choose to coordinate applications from their ROAs, or to be the Applicant on behalf of their ROAs.
+
+- b) submitting valid requests for a UISCN in accordance with this ITU-T Recommendation, using the particular UISCN format as described in clause 5. Invalid requests will be returned by the Registrar.
+
+NOTE 2 – An Applicant may request, where possible, when submitting requests for both a UISCN and a UIFN (or where a UIFN has already been assigned), that the same number be assigned. However, no priority shall be given for the assignments. (Enter a remark indicating the dual request and indicate number as first choice.)
+
+- c) sending a UISCN request form, Part A (see Annex E), on behalf of the ISCS customer, by facsimile to the Registrar. The Applicant submits only one number request per form, but allows an ISCS customer to list acceptable alternative numbers. However, the ISCS
+
+customer may have no preference for a specific number; in this case, any number may be assigned from the available unassigned numbers. In order to indicate to the Registrar that the Applicant has no preference for a specific number, the Applicant is to place an asterisk "\*" instead of number on the Request Form. The UISCN Request Form should be accompanied by evidence of payment of the registration application fee for the reservation and assignment of the UISCN by the Registrar. The ITU will notify Administrations of the amount of the registration application fee in the current Operational Bulletin of ITU.
+
+A registration application fee can be paid by each Applicant based on the number of projected applications expected. The Registrar debits each Applicant's account for each UISCN Request Form received and requests additional funds for the account when the balance approaches depletion. The advance payment can be made:
+
+- by bank transfer to ITU Account No. C8-108.400.1, UBS SA, Geneva (Switzerland) SWIFT No. UBSWCHZH12A.
+  - via a major credit card.
+- d) ensuring that all requested UISCNs are numeric; alpha characters will NOT be accepted.
+  - e) specifying up to 10 UISCNs, which are acceptable to their ISCS customer in order of priority, to limit interaction with the Registrar if their early choices are unavailable.
+  - f) consulting with the ISCS customer for additional choices if the UISCNs are either assigned, reserved, in six-month ageing period, or pending conflict resolution.
+  - g) accepting UISCN Request Form, Part B (see Annex E), as the UISCN reservation confirmation from the Registrar, and notifying the ISCS customer.
+  - h) ensuring that the UISCN is implemented within 180 days and notifying the Registrar via the UISCN Status Notification Form, Part A (see Annex F).
+  - i) Upon advice from the Registrar of use not in conformance with this ITU-T Recommendation, the Applicant will be afforded 90 days to either bring the UISCN into conformance or explain why the current use is conforming. If conformance is not achieved by 90 days, the UISCN will be reclaimed by the Registrar. The UISCN will immediately be disconnected and enter the ageing period. The ISCS service provider(s) will withdraw the ISCS customer's service.
+  - j) notifying the Registrar of changes in information associated with UISCNs, e.g. change of name, address, using the UISCN Request Form, Part A (see Annex E).
+  - k) notifying the Registrar via the UISCN Request Form, Part A (see Annex E), of a disconnection of a UISCN at the time of disconnect.
+  - l) receiving advice from the Registrar of confirmation of number assignment via the UISCN, Status Notification Form, Part B (see Annex F), as confirmation of number assignment, and forwarding a copy of this form to their ISCS customer.
+
+## ANNEX B
+
+### **Registrar procedures**
+
+The function of the Registrar will be performed under the auspices of the ITU. The Registrar has the responsibility for the processing, and associated administrative functions, of registration requests from Applicants. The processing of registration requests will be performed in close cooperation and consultation with national Administrations, as required by national Administrations. This ITU-T Recommendation does not include the legal responsibilities of the Registrar.
+
+The Registrar will:
+
+- a) assign all UISCNs in a fair and unbiased manner.
+- b) validate the request for a UISCN in accordance with this ITU-T Recommendation, and the particular UISCN format as described in clause 5. The Registrar will return the request to the Applicant if the application is not valid.
+- c) administer a single pool of UISCNs in a single database. The database requirements include:
+  - an entry for each UISCN;
+  - the ISCS customer name;
+  - the Applicant;
+  - the status of the UISCN (available, reserved, ageing with maturity date);
+  - historical information;
+  - allow for administering change information;
+  - allow an online view only capability of number status to Applicants;
+  - providing the information necessary to conduct a security investigation, from the UISCN records contained in the registrar's database, to Administrations (details to be arranged per bilateral agreements reached by TSB and the Administrations). This information will be substantiated as being security-based by the agency authorized by the Administration to request the information, and will be provided by the Registrar in a timely and appropriate manner, e.g. as soon as possible, but not later than two days from receipt of the request by the TSB by facsimile or electronic means.
+- d) receive all application requests by the Applicant on behalf of the ISCS customer by facsimile with a UISCN Request Form, Part A (see Annex E), including the registration application payment fee.
+- e) reserve UISCNs on a "first come first served" basis. This means that the UISCN application forms received via facsimile by the Registrar will be processed in order of receipt, based on the local time stamp of the Registrar's facsimile.
+
+NOTE – An Applicant may request, where possible, when submitting requests for both a UISCN and a UIFN (or where a UIFN has already been assigned), that the same number be assigned. However, no priority shall be given for the assignments. Note remarks entered on the form according to item g) 3) of Annex E.
+
+- f) register all applications when received with details of the time and date, using the standard time of the Registrar.
+- g) determine whether the requested UISCN is available for assignment. If the UISCN requested is unavailable for assignment, see if an alternate UISCN was specified; if not, the Registrar will return the request to the Applicant for another choice.
+- h) accept no verbal requests or inquiries, for available UISCNs.
+- i) accept only one ISCS customer per UISCN Request Form.
+- j) respond with a reservation to the Applicant, within two working days of receipt of request, via facsimile, with a UISCN Request Form, Part B (see Annex E), to acknowledge the reservation confirmation and update the UISCN database with the appropriate notation. Where a request for a specific number is refused or delayed, the Applicant should be informed of the reason, e.g. assigned, reserved, in six-month ageing period, or pending conflict resolution.
+- k) accept confirmation of service implementation via the UISCN Status Notification Form, Part A (see Annex F), from the Applicant.
+
+- l) If the UISCN Status Notification Form, Part A (see Annex F) is not received within 180 days, the UISCN is no longer reserved. However, a reasonable extension beyond the 180 days is authorized, at the Registrar's discretion, for compelling reasons, e.g. a service provider inability to complete interconnection with a network operator involved in the ISCS service. A reserved UISCN that has not been activated will immediately go back into the pool of numbers available for assignment and no ageing period is required.
+- m) respond to confirmation of service implementation via the UISCN Status Notification Form, Part B (see Annex F), and assign the UISCN accordingly.
+- n) update the UISCN database accordingly.
+- o) provide information to Applicants on the application process.
+- p) upon recognizing a non-conforming use, inform the Applicant of the alleged misuse. The Applicant will be afforded 90 days to either bring the UISCN into conformance or explain why the current use is conforming. If conformance is not achieved by 90 days, the UISCN will be reclaimed by the Registrar. The UISCN will immediately enter the ageing period. The Registrar will also immediately reclaim a UISCN upon request of all Administrations of the countries in which the service is provided when the request is the result of a security investigation.
+- q) accept notice of disconnection from the Applicant via the UISCN Request Form, Part A (see Annex E). The UISCN will be placed in the ageing period on the date the Registrar receives the notification of disconnect.
+- r) When an existing UISCN is completely disconnected, the UISCN can be assigned to another ISCS customer normally after a six-month ageing period. If, however, an applicant requests the assignment of a UISCN which is in the ageing period, then the UISCN may be assigned if it has been in ageing for at least three months.
+- s) The Registrar will send confirmation of the disconnection of the UISCN to the Applicant, via the UISCN Status Notification Form, Part B (see Annex F).
+- t) accept changes of information associated with UISCNs (e.g. change of name, address), via the UISCN Request Form, Part A (see Annex E) and UISCN Multiple ROA Notification Form (Annex G).
+- u) periodically confirm that assigned UISCNs are in use, at least between two countries, and exercise authority to take appropriate action regarding inactive UISCNs.
+- v) monitor and audit the status of the UISCN resource and produce reports to the appropriate Study Group. These reports will include the actual quantity of numbers assigned and growth statistics associated with those assignments.
+- w) publish a list of assigned numbers using an agreed method.
+- x) If a UISCN is inadvertently assigned to multiple ISCS customers, the Applicant with the earliest dated application will be the Applicant of record.
+
+## ANNEX C
+
+### **Change request procedures**
+
+### **C.1 Multiple ROAs documentation procedures**
+
+- a) The Registrar will maintain within the UISCN database multiple ROAs associated with a single UISCN.
+- b) The Applicant and/or the Additional ROAs will provide information on the addition or deletion of ROAs to the Registrar via the UISCN Multiple ROAs Notification Form (see Annex G).
+
+### **C.2 Applicant change procedures**
+
+- a) If the Registrar receives a Disconnect Request from an Applicant and there are other ROAs within the Registrar's database associated with that particular UISCN, then the Registrar will assign a new default Applicant to that UISCN, unless otherwise requested by the ISCS customer via their preferred ROA. The default Applicant will be initially selected and notified by the Registrar based on the earliest registered additional ROA.
+- b) The default Applicant shall notify the Registrar if he accepts the assignment as the Applicant for that particular UISCN. If one of the other ROAs is the customer's choice as its Applicant, then that other ROA shall notify the Registrar with proof of change from that customer.
+- c) If all the other ROAs associated with that UISCN respond back to the Registrar that the UISCN has been disconnected, then the Registrar will place the UISCN in the ageing state.
+
+### **C.3 Change of Applicant**
+
+- a) The customer may change Applicant while its UISCN is in the Reserved/Assigned Status.
+- b) The new Applicant will notify the Registrar of the change via Annex G.
+- c) The new Applicant will have 180 days to activate the UISCN and must inform the Registrar of service implementation via the UISCN Status Notification Form, Part A (see Annex F).
+- d) Even if the customer transfers to another Applicant, a UISCN can only remain in a reserved status for a maximum of 360 days in order to prevent the misuse of UISCNs. If the customer has changed Applicant, but has not activated the UISCN within the 360 days, the UISCN will be reclaimed by the Registrar.
+
+## **ANNEX D**
+
+### **Registrar start-up and duplicate request procedures**
+
+### **D.1 Registrar procedures**
+
+The purpose of the Registrar start-up procedures is to start the assignment of numbers out of the UISCN resource pool in an efficient and fair manner. The administration of UISCNs is divided into two phases: the start-up phase and receipt and validation of applications. The ongoing phase is the administration of the UISCN assignment process after the start-up phase.
+
+#### **D.1.1 Start-up phase**
+
+The purpose of the start-up phase is to outline the procedures for receipt and validation of UISCN applications.
+
+The following are the procedures to be adhered to during the start-up phase:
+
+- a) (T1) 90 days prior to the Registrar acceptance of applications, the Registrar will announce UISCN availability.
+- b) (T2) 30 days prior to the reservation of UISCNs by the Registrar, receipt and validation of UISCN applications will be accomplished. All valid requests received during this time period are considered to be received at the same time to assure that all Applicants can be treated equally.
+- c) (T3) There will be an additional three days after the 30 days acceptance of applications (T2) for the Registrar to amend invalid requests with the Applicants.
+- d) (T4) At expiration of T3, the Registrar will make UISCN assignments and resolve conflict resolutions received during the start-up period.
+
+| T1                       | T2                         | T3                                     | T4                                                                       |
+|--------------------------|----------------------------|----------------------------------------|--------------------------------------------------------------------------|
+| Advertising notification | Collection of applications | 3-day period to amend invalid requests | Conflict resolution and assigning UISCNs to Applicants received in T1-T3 |
+
+----->  
+First come first served period
+
+----->  
+Validation period
+
+#### D.1.2 Ongoing phase
+
+The ongoing phase of UISCN administration is detailed in Annexes A and B. Applications during the ongoing period will be accepted from the first day of T3. However, number reservations will not be made until ALL conflict resolutions are complete; see D.2 for details and time-related activities for conflict resolution.
+
+### D.2 Duplicate requests procedures
+
+#### D.2.1 Duplicate requests
+
+The purpose of these procedures is to resolve UISCN conflicts, e.g. when more than one Applicant applies for the same UISCN at the same time.
+
+- The Registrar should advise only the involved Applicants, and Administrations if so required by those Administrations, when problems are identified, and provide advice to them and cooperate in problem resolution.
+- The Registrar shall give priority to the Applicants embedding their ISCS customer's existing national SCSN; this is known as priority assignment. The service provider that provides the national shared cost service may be different than the Applicant that is embedding the ISCS customer's SCSN in the UISCN.
+
+#### D.2.2 Specific procedures
+
+- The Applicant can only request and receive priority assignment based on the intent to embed the existing national shared cost number (or a portion of that number). The embedding can only be requested by adding trailing or leading filler digits to the existing national shared cost number (or portion of that number), in the manner illustrated below.
+
+For example:
+
+- ISCS customer A's 7-digit national shared cost number is 234 5678:
+  - embedding by adding leading filler digit: UISCN requested: 808 Y2345678;
+  - embedding by adding trailing filler digit: UISCN requested: 808 2345678Y;
+- ISCS customer B's 6-digit national shared cost number is 654 321:
+  - embedding by adding leading filler digits: UISCN requested: 808 YY654321;
+  - embedding by adding trailing filler digits: UISCN requested: 808 654321YY;
+  - embedding by adding one leading and one trailing digit: UISCN requested: 808 Y654321Y;
+
+where X = 0-9, Y = 0-9.
+
+Similar principles apply for ISCS customers with fewer than 6-digit national shared cost numbers.
+
+- b) When two or more Applicants request the same UISCN, and only one of the Applicants request a priority assignment, the Registrar will assign the UISCN to the Applicant which requested priority assignment. The Registrar will then assign the stated alternative choices, or solicit alternative choices, to the other Applicants.
+- c) When two or more Applicants request the same UISCN based on embedding their national shared cost number, and if only one of the Applicants national shared cost number was in service prior to 1 February 1999 and request priority assignment, the Registrar will assign the UISCN to that Applicant. The Registrar will then assign the stated alternative choices, or solicit alternative choices, to the other Applicants.
+- d) When two or more Applicants requesting the same UISCN based on their national shared cost number and two or more of the Applicant's national shared cost numbers were in service prior to 1 February 1999, and request priority assignment, the Registrar will communicate with the Applicants and notify them of the duplicate request and attempt to resolve the duplicate request by having the Applicant(s) change their filler digits to eliminate the duplication. During this procedure, the Registrar will inform the Applicants that they are in contention for their selected UISCN. Identities of other Applicants involved in the contention will only be divulged with the consent of all the involved Applicants, for the purpose of resolving the contention.
+- e) When two or more Applicants requesting the same UISCN based on their national shared cost number, request priority assignment, the Registrar will communicate with the Applicants and notify them of the duplicate request and attempt to resolve the duplicate request by having the Applicant(s) change their filler digits to eliminate the duplication. During this procedure, the Registrar will inform the Applicants that they are in contention for their selected UISCN. Identities of other Applicants involved in the contention will only be divulged with the consent of all the involved Applicants, for the purpose of resolving the contention.
+- f) When two or more Applicants requested the same UISCN, and none have requested priority assignment, the Registrar will communicate with the Applicants and notify them of the duplicate request and attempt to resolve the duplicate request by having the Applicant(s) choose an alternate UISCN if applicable. During this procedure, the Registrar will inform the Applicants that they are in contention for their selected UISCN. Identities of other Applicants involved in the contention will only be divulged with the consent of all the involved Applicants, for the purpose of resolving the contention.
+- g) In the absence of an agreement to resolve the duplicate request with the Applicants, the Registrar will, after 15 days, perform a random selection to resolve the duplicate request. The Applicants not receiving the UISCN will be assigned one of their alternate choices or the Registrar will solicit another choice, if not provided.
+
+## ANNEX E
+
+### **Preparation of Universal International Shared Cost Number Request Form**
+
+### **E.1 Preparation of UISCN Request Form, Part A**
+
+The Universal International Shared Cost Number Request Form, Part A, is completed by the Applicant. The fields are as follows:
+
+- a) Transmittal date: Date the form was sent to the Registrar.
+- b) Company name (Applicant): As defined in 3.2, Applicant.
+- c) Contact name and address: The contact name and address of the Applicant.
+
+- d) Telephone, fax numbers, and e-mail address: The telephone, fax numbers and e-mail address of the Applicant.
+- e) Request type:
+  - **New:** A new service involving a new UISCN is established, or an additional service provider will be providing ISCS service with the existing number to the ISCS customer.
+  - **Change:** An existing service requires modification (i.e. change of name, or address).
+  - **Disconnect:** An existing service is completely disconnected. The number can be assigned to another ISCS customer only after a six-month ageing period.
+  - **Cancel:** The service does not exist yet, and the ISCS customer decides not to use this number; the number automatically goes into the pool of available numbers for immediate assignment.
+- f) Reason for change: Indicate the type of change.
+- g) Universal International Shared Cost Number: Indicate either:
+  - 1) ISCS customer requests one of the numbers listed below (in order of preference); or
+  - 2) ISCS customer requests any available number with no specific preference;
+  - 3) ISCS customer requests the same number for both UIFN and UISCN [see item b) in Annex A] – Enter remark.
+- h) ISCS customer name and address: Name of ISCS customer required, address optional.
+- i) Expected due date: Service will be expected to officially commence on this date.
+- j) Is ISCS customer embedding entire existing national SCSN?
+- k) Existing national SCSN that is being embedded and the CC under which this SCSN is in use.
+- l) Was existing national SCSN implemented prior to 1 February 1999?
+- m) Countries with which the UISCN will be initially implemented.
+- n) Coordination (reference) number: A reference number assigned by the service provider to identify the number request. This number should be used as a cross-reference on the Universal International Shared Cost Number Request Form, and the Universal International Shared Cost Number Status Notification Form.
+- o) Payment of the registration application fee: Indicate the method of payment used.
+
+### **E.2 Preparation of UISCN Request Form, Part B**
+
+The Universal International Shared Cost Number Request Form is completed by the Registrar to confirm UISCN reservation. The fields are as follows:
+
+- a) Transmittal date: Date the form was returned.
+- b) Universal International Shared Cost Number: The number reserved, based on its priority and availability, subject to the payment of the registration application fee.
+- c) Reason for number denial: When a request for a specific number is refused, the Applicant should be informed of the reason for each number listed in Part A of the UISCN Request Form, e.g.:
+  - 1) assigned;
+  - 2) reserved;
+  - 3) in a six-month ageing period;
+  - 4) pending conflict resolution.
+
+## ANNEX E (FORM)
+
+(One number request per form)
+
+### **Universal International Shared Cost Number Request Form**
+
+#### **Part A filled out by the Applicant**
+
+Transmittal date: (a)
+
+(Applicant)
+
+Send to:
+
+Company name (b)
+
+UISCN Registrar
+
+Contact name (c)
+
+International Telecommunication Union
+
+Address
+
+Telecommunication Standardization Bureau
+
+Telephone number (d)
+
+CH-1211 GENEVA 20, Switzerland
+
+Fax number
+
+Fax: +41 22 730 6200
+
+E-mail address
+
+Tel: +41 22 730 6220
+
+Request type (mark with an X): (e) New  Change  Disconnect  Cancel
+
+Reason for change: (f)
+
+Universal International Shared Cost Number Requests, acceptable alternatives in order of priority: (g)
+
+1) +808 6) +808   
+ 2) +808 7) +808   
+ 3) +808 8) +808   
+ 4) +808 9) +808   
+ 5) +808 10) +808
+
+Remark: (g3)
+
+ISCS customer name: (h) Expected ISCS customer due date: (i)
+
+ISCS customer address (Optional):
+
+Is ISCS customer embedding existing national SCN? (j) Yes  No
+
+Existing national SCN that is being embedded: (k) CC SCN
+
+Existing national SCN implemented prior to 1 February, 1999 (l) Yes  No
+
+Country(ies) with which the ISCS will be implemented initially (m)
+
+Coordination (reference) number: (n)
+
+Payment of the registration application fee: (o) Swiss francs
+
+Specify the method of payment use:
+
+by bank transfer to ITU account No. C8-108.400.1
+
+UBS SA
+
+Geneva, Switzerland
+
+SWIFT No. UBSWCHZH12A
+
+major credit card
+
+##### **Part B filled out by the Registrar to be returned to Applicant**
+
+Transmittal date: (a)
+
+This UISCN is reserved for 180 days: (b) +808
+
+The UISCN(s) listed above in Part A, were denied reservation, with reason: (c)
+
+1) 6)   
+ 2) 7)   
+ 3) 8)   
+ 4) 9)   
+ 5) 10)
+
+Remarks:
+
+Signature (Applicant/Registrar)
+
+## ANNEX F
+
+### **Preparation of Universal International Shared Cost Number Status Notification Form**
+
+### **F.1 Preparation of UISCN Status Notification Form, Part A**
+
+The Universal International Shared Cost Number Status Notification Form is completed by the Applicant to change the reserved UISCN to assigned. The fields are as follows:
+
+- a) Transmittal date: Date the form was sent to Registrar.
+- b) Company name (Applicant): As defined in 3.2, Applicant.
+- c) Contact name and address: The contact name and address of the Applicant.
+- d) Telephone, fax numbers and E-mail address: The telephone, fax numbers and E-mail address of the Applicant.
+- e) Universal International Shared Cost Number.
+- f) Date of activation: The date that the number was activated internationally.
+- g) Coordination (reference) number: A reference number assigned by the service provider to identify the number request. This number should be used as a cross-reference on the Universal International Shared Cost Number Request Form, and the Universal International Shared Cost Number Status Notification Form.
+- h) ISCS customer name: Name of ISCS customer is required; address is optional.
+- i) Enter appropriate remark if an ISCS customer is making a change in their Applicant [or in Items b), c), or d)].
+
+### **F.2 Preparation of UISCN Status Notification Form, Part B**
+
+The Universal International Shared Cost Number Status Notification Form is completed by the Registrar to confirm the shared cost assignment to Applicant. The fields are as follows:
+
+- a) Transmittal date: Date the form was returned.
+- b) Universal international shared cost number: The UISCN which the registrar has changed from reserved, to assigned, from assigned to disconnected.
+- c) Updated change information.
+
+## ANNEX F (FORM)
+
+### Universal International Shared Cost Number Status Notification Form
+
+#### **Part A filled out by the Applicant**
+
+Transmittal date: (a)
+
+(Applicant)
+
+Send to:
+
+Company name (b) UISCN Registrar  
+Contact name (c) International Telecommunication Union  
+Address Telecommunication Standardization Bureau  
+Telephone number (d) CH-1211 GENEVA 20, Switzerland  
+Fax number Fax: +41 22 730 6200  
+E-mail address Tel: +41 22 730 6220
+
+The following UISCN was implemented:
+
+(e) +808
+
+The date of international activation is: (f)
+
+Day Month Year
+
+Coordination (reference number: (g)
+
+ISCS customer name: (h)
+
+Customer address:
+
+Remarks: (i)
+
+#### **Part B filled out by the Registrar to be returned to Applicant**
+
+The below UISCN was assigned:
+
+Transmittal date: (a)
+
+(b) +808
+
+The below UISCN was disconnected  or cancelled :
+
+(b) +808
+
+Remarks: (c)
+
+Signature: (Applicant/Registrar)
+
+## ANNEX G
+
+### **Preparation of Universal International Shared Cost Number Multiple ROA Notification Form**
+
+### **G.1 Preparation of UISCN Multiple ROA Notification Form, Part A**
+
+The form is to be completed by the new Applicant or additional ROA to report additions or deletions of ROA to the Registrar. The fields are as follows:
+
+- a) Transmittal date: Date the form was sent to the Registrar.
+- b) Company Name/ROA: ROA name and contact information.
+- c) UISCN number: Specific UISCN number associated with this request.
+- d) ISCS customer name: The exact name of the ISCS customer. The Registrar will not record any change of information if the customer's name is not the same as the one recorded in the Registrar's database.
+- e) Customer address: This is an optional field. If included it should be the address of the Main office of the ISCS customer or the address recorded in the Registrar's database.
+- f) Indicate whether the UISCN has been implemented or was disconnected.
+- g) Reasons: Provide any comments deemed necessary.
+
+### **G.2 Preparation of UISCN Multiple ROA Notification Form, Part B**
+
+The UISCN Multiple ROA Notification Form is completed by the Registrar to confirm the premium rate number assignment/disconnect for the additional ROA(s). The fields are as follows:
+
+- a) Transmittal date: Date the form was returned.
+- b) Universal International Shared Cost Number: the UISCN that the Registrar has changed from "reserved", to "assigned", and from "assigned" to "disconnected".
+- c) Updated change information.
+
+## ANNEX G (FORM)
+
+### **Universal International Shared Cost Number Multiple ROA Notification Form**
+
+**To be returned to:** International Telecommunication Union  
+ Telecommunication Standardization Bureau  
+ Place des Nations  
+ CH-1211 GENEVA 20, Switzerland  
+ Fax: +41 22 730 6200 Tel: +41 22 730 6220
+
+**Part A to be filled out by the Recognized Operating Agency (ROA)** Transmittal date: (a)
+
+Company name/ROA (b)
+
+Contact name
+
+Address
+
+Telephone number +
+
+Fax number +
+
+E-mail
+
+UISCN number (c) +808
+
+ISCS customer name (d)
+
+Customers address (e)
+
+(Check appropriate box) (f)
+
+- The above UISCN has been implemented or is in the Reserved State.
+- The above UISCN was disconnected
+
+Reasons: (g)
+
+#### **Part B filled out by the Registrar to be returned to Applicant**
+
+The below UISCN was assigned: Transmittal date: (a)
+
+(b) +808
+
+The below UISCN was disconnected:
+
+(b) +808
+
+Remarks: (c)
+
+Signature: (Applicant/Registrar)
+
+## APPENDIX I **Applicant procedure**
+
+![Flowchart of Applicant procedure for UISCN request.](365b54f616aff249b4e6c0edafdcb9b3_img.jpg)
+
+```
+graph TD; Idle1([Idle]) --> Request{Request for UISCN received from Subscriber}; Request --> Valid{Request valid}; Valid -- No --> Consult{Consult Subscriber}; Valid -- Yes --> Process[Process request]; Process --> Transmit{Transmit request for UISCN to Registrar on behalf of Subscriber}; Transmit --> Returned{Application returned}; Returned -- Yes --> Consult; Returned -- No --> Available{Is UISCN available}; Available -- No --> Consult; Available -- Yes --> ProcessRes[Process Reservation Confirmation of UISCN for Subscriber]; ProcessRes --> EndIdle([Idle]); Consult --> CanAlternate{Can alternate request be made}; CanAlternate -- Yes --> Request; CanAlternate -- No --> EndIdle;
+```
+
+The flowchart illustrates the applicant procedure for a UISCN request. It begins with an 'Idle' state, leading to a decision point 'Request for UISCN received from Subscriber'. If the request is not valid ('No'), the process moves to 'Consult Subscriber'. If valid ('Yes'), it proceeds to 'Process request', then 'Transmit request for UISCN to Registrar on behalf of Subscriber'. From there, a decision 'Application returned' is made. If 'Yes', it goes to 'Consult Subscriber'; if 'No', it checks 'Is UISCN available'. If 'No' to availability, it goes to 'Consult Subscriber'; if 'Yes', it proceeds to 'Process Reservation Confirmation of UISCN for Subscriber'. All three paths ('Consult Subscriber', 'Is UISCN available' - No, and 'Process Reservation Confirmation') lead to a decision 'Can alternate request be made'. If 'Yes', it loops back to the initial request; if 'No', it ends at an 'Idle' state. A small code 'T0208570-00' is present at the bottom right of the diagram.
+
+Flowchart of Applicant procedure for UISCN request.
+
+The text within this Recommendation will take precedence over the flow diagrams in this appendix and in Appendices II and III, if any discrepancies are identified.
+
+## APPENDIX II Registrar procedure
+
+![Flowchart of Registrar procedure](73b5cce955ba9415a98791db7b0080ad_img.jpg)
+
+```
+graph TD; Idle1([Idle]) --> Request{Request for UISCN received from Applicant}; Request --> Valid{Request valid}; Valid -- No --> Return[Return application to Applicant]; Valid -- Yes --> Available{Is UISCN available}; Available -- No --> Alternate{Is alternate UISCN specified}; Alternate -- No --> InformNotAvail[Inform Applicant UISCN is not available]; Alternate -- Yes --> Valid; Available -- Yes --> Conflict{Is UISCN in conflict}; Conflict -- Yes --> C1((1 App. III)); C1 --> C2((2 App. III)); C2 --> Conflict; Conflict -- No --> MarkReserved[Mark UISCN "reserved" for Subscriber]; MarkReserved --> InformReserved[Inform Applicant UISCN is reserved]; InformReserved --> StartTimer[Start reservation time 180 days]; StartTimer --> TimerExpired{Reservation timer expired}; TimerExpired -- Yes --> InformCancelled[Inform Applicant reservation is cancelled]; TimerExpired -- No --> Activation[Activation notification received]; Activation --> MarkAssigned[Mark UISCN as assigned]; MarkAssigned --> StopTimer[Stop Reservation Timer]; StopTimer --> InformAssigned[Inform Applicant that UISCN is assigned]; InformAssigned --> Idle2([Idle]); InformNotAvail --> Idle2; InformCancelled --> Idle2;
+```
+
+The flowchart illustrates the Registrar procedure. It begins with an 'Idle' state, leading to a 'Request for UISCN received from Applicant'. A decision 'Request valid' follows. If 'No', the application is returned. If 'Yes', it checks if the UISCN is available. If 'No', it checks if an alternate UISCN is specified. If 'No', it informs the applicant that the UISCN is not available. If 'Yes', it loops back to the 'Request valid' decision. If 'Yes', it checks if the UISCN is in conflict. If 'Yes', it leads to connector '1 (App. III)', which then leads to connector '2 (App. III)', which loops back to the 'Is UISCN in conflict' decision. If 'No', it marks the UISCN as 'reserved' for the subscriber, informs the applicant, and starts a 180-day reservation timer. After the timer expires, if 'Yes', it informs the applicant that the reservation is cancelled. If 'No', it checks for an activation notification. If received, it marks the UISCN as assigned, stops the reservation timer, informs the applicant, and returns to the 'Idle' state. Both 'Inform Applicant UISCN is not available' and 'Inform Applicant reservation is cancelled' lead to the final 'Idle' state.
+
+Flowchart of Registrar procedure
+
+T0208580-00
+
+## APPENDIX III
+
+### Duplicate request procedure
+
+![Flowchart for Duplicate request procedure](552265bdbcf6d43d341fd018a9076269_img.jpg)
+
+```
+graph TD; Start((2 (App. II))) --> D1{Any priority requests}; D1 -- No --> Inform[Inform Applicant UISCN is in conflict]; D1 -- Yes --> D2{Only one priority request}; D2 -- Yes --> D3{Is Applicant the one with priority}; D2 -- No --> D4{For each application is this a priority request}; D3 -- No --> End3((3 (App. II))); D3 -- Yes --> End1_1((1 (App. II))); D4 -- No --> End1_2((1 (App. II))); D4 -- Yes --> Inform; Inform --> D5{Involved Applicants agree to divulge identities}; D5 -- No --> Reg[Applicants negotiate through Registrar]; D5 -- Yes --> Negotiate[Applicants negotiate with each other]; Reg --> D6{Conflict resolved}; Negotiate --> D6; D6 -- No --> Random[Perform random selection]; D6 -- Yes --> D7{Applicant receives UISCN}; Random --> D7; D7 -- Yes --> End3_2((3 (App. II))); D7 -- No --> End1_3((1 (App. II))); T0208590-00
+```
+
+The flowchart illustrates the 'Duplicate request procedure'. It begins at node '2 (App. II)' leading to a decision 'Any priority requests'. If 'No', it proceeds to 'Inform Applicant UISCN is in conflict'. If 'Yes', it checks 'Only one priority request'. If 'Yes', it checks 'Is Applicant the one with priority'; if 'No', it ends at '3 (App. II)', if 'Yes', it ends at '1 (App. II)'. If 'No' to 'Only one priority request', it checks 'For each application is this a priority request'; if 'No', it ends at '1 (App. II)', if 'Yes', it proceeds to 'Inform Applicant UISCN is in conflict'. From 'Inform Applicant UISCN is in conflict', it checks 'Involved Applicants agree to divulge identities'; if 'No', it goes to 'Applicants negotiate through Registrar', if 'Yes', it goes to 'Applicants negotiate with each other'. Both lead to 'Conflict resolved'; if 'No', it goes to 'Perform random selection', if 'Yes', it checks 'Applicant receives UISCN'. 'Perform random selection' also leads to 'Applicant receives UISCN'; if 'Yes', it ends at '3 (App. II)', if 'No', it ends at '1 (App. II)'. A code 'T0208590-00' is at the bottom right.
+
+Flowchart for Duplicate request procedure
+
+
+
+
+
+# **SERIES OF ITU-T RECOMMENDATIONS**
+
+|                 |                                                                                                                                |
+|-----------------|--------------------------------------------------------------------------------------------------------------------------------|
+| Series A        | Organization of the work of ITU-T                                                                                              |
+| Series B        | Means of expression: definitions, symbols, classification                                                                      |
+| Series C        | General telecommunication statistics                                                                                           |
+| Series D        | General tariff principles                                                                                                      |
+| <b>Series E</b> | <b>Overall network operation, telephone service, service operation and human factors</b>                                       |
+| Series F        | Non-telephone telecommunication services                                                                                       |
+| Series G        | Transmission systems and media, digital systems and networks                                                                   |
+| Series H        | Audiovisual and multimedia systems                                                                                             |
+| Series I        | Integrated services digital network                                                                                            |
+| Series J        | Transmission of television, sound programme and other multimedia signals                                                       |
+| Series K        | Protection against interference                                                                                                |
+| Series L        | Construction, installation and protection of cables and other elements of outside plant                                        |
+| Series M        | TMN and network maintenance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits |
+| Series N        | Maintenance: international sound programme and television transmission circuits                                                |
+| Series O        | Specifications of measuring equipment                                                                                          |
+| Series P        | Telephone transmission quality, telephone installations, local line networks                                                   |
+| Series Q        | Switching and signalling                                                                                                       |
+| Series R        | Telegraph transmission                                                                                                         |
+| Series S        | Telegraph services terminal equipment                                                                                          |
+| Series T        | Terminals for telematic services                                                                                               |
+| Series U        | Telegraph switching                                                                                                            |
+| Series V        | Data communication over the telephone network                                                                                  |
+| Series X        | Data networks and open system communications                                                                                   |
+| Series Y        | Global information infrastructure and Internet protocol aspects                                                                |
+| Series Z        | Languages and general software aspects for telecommunication systems                                                           |

marked/E/T-REC-E.182-199803-I_PDF-E/raw.md

@@ -0,0 +1,561 @@
+
+
+![ITU logo](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg)
+
+The logo of the International Telecommunication Union (ITU) features the letters 'ITU' in a bold, sans-serif font, superimposed on a stylized globe with intersecting lines.
+
+ITU logo
+
+INTERNATIONAL TELECOMMUNICATION UNION
+
+**ITU-T**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+**E.182**
+
+(03/98)
+
+SERIES E: OVERALL NETWORK OPERATION,  
+TELEPHONE SERVICE, SERVICE OPERATION AND  
+HUMAN FACTORS
+
+Operation, numbering, routing and mobile services –  
+International operation – Tones in national signalling  
+systems
+
+---
+
+**Application of tones and recorded  
+announcements in telephone services**
+
+ITU-T Recommendation E.182
+
+(Previously CCITT Recommendation)
+
+---
+
+# ITU-T E-SERIES RECOMMENDATIONS
+
+## **OVERALL NETWORK OPERATION, TELEPHONE SERVICE, SERVICE OPERATION AND HUMAN FACTORS**
+
+***OPERATION, NUMBERING, ROUTING AND MOBILE SERVICES***
+
+**INTERNATIONAL OPERATION**
+
+|                                                       |             |
+|-------------------------------------------------------|-------------|
+| Definitions                                           | E.100–E.103 |
+| General provisions concerning Administrations         | E.104–E.119 |
+| General provisions concerning users                   | E.120–E.139 |
+| Operation of international telephone services         | E.140–E.159 |
+| Numbering plan of the international telephone service | E.160–E.169 |
+| International routing plan                            | E.170–E.179 |
+
+|                                             |                    |
+|---------------------------------------------|--------------------|
+| <b>Tones in national signalling systems</b> | <b>E.180–E.199</b> |
+|---------------------------------------------|--------------------|
+
+|                                                        |             |
+|--------------------------------------------------------|-------------|
+| Maritime mobile service and public land mobile service | E.200–E.229 |
+|--------------------------------------------------------|-------------|
+
+**OPERATIONAL PROVISIONS RELATING TO CHARGING AND ACCOUNTING IN THE INTERNATIONAL TELEPHONE SERVICE**
+
+**UTILIZATION OF THE INTERNATIONAL TELEPHONE NETWORK FOR NON-TELEPHONY APPLICATIONS**
+
+|                                  |             |
+|----------------------------------|-------------|
+| ISDN PROVISIONS CONCERNING USERS | E.330–E.399 |
+|----------------------------------|-------------|
+
+***QUALITY OF SERVICE, NETWORK MANAGEMENT AND TRAFFIC ENGINEERING***
+
+**NETWORK MANAGEMENT**
+
+**TRAFFIC ENGINEERING**
+
+**QUALITY OF TELECOMMUNICATION SERVICES: CONCEPTS, MODELS, OBJECTIVES AND DEPENDABILITY PLANNING**
+
+*For further details, please refer to ITU-T List of Recommendations.*
+
+## **ITU-T RECOMMENDATION E.182**
+
+# **APPLICATION OF TONES AND RECORDED ANNOUNCEMENTS IN TELEPHONE SERVICES**
+
+## **Summary**
+
+This Recommendation states some provisions and conditions for the applicability of tones and recorded announcements for user information.
+
+###### **Source**
+
+ITU-T Recommendation E.182 was revised by ITU-T Study Group 2 (1997-2000) and was approved under the WTSC Resolution No. 1 procedure on the 9th of March 1998.
+
+## FOREWORD
+
+ITU (International Telecommunication Union) is the United Nations Specialized Agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the ITU. The ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis.
+
+The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics.
+
+The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Resolution No. 1.
+
+In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC.
+
+## NOTE
+
+In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+## INTELLECTUAL PROPERTY RIGHTS
+
+The ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. The ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process.
+
+As of the date of approval of this Recommendation, the ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database.
+
+© ITU 1998
+
+All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU.
+
+## CONTENTS
+
+|                                                                                              | <i>Page</i> |
+|----------------------------------------------------------------------------------------------|-------------|
+| Introduction .....                                                                           | 1           |
+| Annex A – List of tones and announcements used as indications to telephone subscribers ..... | 4           |
+| A.1    Basic terms .....                                                                     | 4           |
+| A.2    Tones .....                                                                           | 5           |
+| A.3    Recorded announcements .....                                                          | 7           |
+
+
+
+# **APPLICATION OF TONES AND RECORDED ANNOUNCEMENTS IN TELEPHONE SERVICES**
+
+*(revised in 1998)*
+
+## **Introduction**
+
+1 This Recommendation gives the responses that telephone networks should provide to subscribers in the operation of both basic and supplementary telephone services. Three levels of response may be given:
+
+- preferred responses based solely upon subscriber requirements;
+- accepted responses to be used where technical or economic reasons inhibit the use of preferred responses;
+- exceptional responses to be used where severe technical or economic constraints prevent the use of preferred or accepted responses.
+
+2 It has not been possible in some cases to state a universally applicable preference between recorded announcements and tones. The factors influencing such a choice vary widely between Administrations in their relative importance. Some features which make recorded announcements attractive are:
+
+- They can reduce the level of calls to operators thus saving considerable expense.
+- From a human factors point of view the use of an excessive number of different tones can be confusing to the user. Recorded announcements give an opportunity to present a far greater spectrum of information.
+- They can impart more detailed and specific information than tones.
+- They can have less chance of being misunderstood than tones in situations encountered infrequently.
+
+Nevertheless recorded announcements have certain drawbacks also:
+
+- They require more time to convey simple information than a tone indication would.
+- They are meaningless to people who do not understand the language used. This fact may make their application in multilingual countries impractical.
+- Technical and economic constraints might inhibit their use in some networks.
+- Subscribers might not always listen long enough to distinguish between different announcements.
+
+3 In this Recommendation, where no preference is stated between alternative responses, individual Administrations should evaluate the situation in their own networks taking the above factors into account. Additional studies will be undertaken to better evaluate the relative merits of tones and recorded announcements.
+
+4 A list of tones and announcements used as indications to telephone subscribers is given in Annex A.
+
+The ITU-T,
+
+*considering*
+
+- a) that subscribers set up telephone calls and control supplementary telephone services by means of an interchange of information between the subscriber and the telephone system;
+- b) that information sent by the subscriber to the exchange is standardized in several Recommendations, e.g., Recommendation E.164 for country codes;
+- c) that information from the telephone system to the subscriber can be sent in the form of tones or recorded announcements;
+
+- d) that the technical characteristics of the dial tone, the ringing tone, the busy tone, the congestion tone, the special information tone and the warning tone are specified in Recommendation E.180 and that the specification of other tones is studied by the ITU-T;
+- e) that a certain tone or recorded announcement should unambiguously indicate the desired subscriber action without requiring subscriber knowledge of the operation of the telephone system;
+- f) that a standardized application of tones and recorded announcements will improve subscriber performance and will lead to a more efficient use of the telephone network;
+- g) that for normal telephone calls and supplementary telephone services an identical application of tones and recorded announcements is desirable;
+- h) that it is easy to implement standardization of the application of tones and recorded announcements for new supplementary telephone services, but this is more difficult for existing telephone systems and should be regarded as a long-term objective;
+- i) that to avoid abuse of the transfer charge service it is desirable that an operator should be advised when connecting calls to a payphone;
+- j) that only tones and announcements are covered in this Recommendation although it can be seen that in some cases a visual indication may be an alternative,
+
+### *recommends*
+
+- 1 that this Recommendation shall apply to all telephone services and telephone networks. PABXs should, with certain indicated exceptions, use the same tones as the network in the country in which it is located;
+  - 2 that all tones and recorded announcements should be given as soon as the information received by the telephone network is sufficient to decide which tone or recorded announcement applies, unless there is an established subscriber need for the indication to be given later;
+  - 3 that when a subscriber should wait for a network reaction, no tones or announcement should be given. This condition applies during, e.g., dial-tone delay and post-dialling delay. Exceptionally when a post-dialling delay on an outgoing international automatic call occurs that is likely to cause a subscriber to abandon the call, an appropriate announcement or a *comfort tone* may be used if it has been shown to reduce premature abandonment;
+  - 4 that when a subscriber should start dialling, a *dial tone* should be given. At PABXs this tone may be different from that at the public exchange and in this case the tone is named PABX *internal dial tone*;
+  - 5 that when a subscriber should start dialling and a special condition applies to his line, a *special dial tone* may be given. This condition applies, for example, during activated diversion of calls to another number;
+  - 6 that, except for PABXs and supplementary services, a second dial tone should not be used and a second application of dial tone should also be avoided;
+  - 7 that when a subscriber should wait until the called party answers and no special condition applies to the line, a *ringing tone* should be given;
+  - 8 that when the called number is busy and no special condition applies to the called line, a *busy tone* should be given to the calling subscriber;
+  - 9 that when a special condition of either "call waiting" or "call diversion" applies to a called line, the calling subscriber may be informed about the special condition. The responses should therefore be either a *specific recorded announcement* or *caller waiting tone* or *ringing tone*. In PABXs a *special ringing tone* may be used for the "call waiting" service.
+- In the case of "call diversion", if an announcement is given, it is necessary to give the announcement before the call is diverted. This especially applies if additional call charges have to be paid by the calling party.
+- 10 that a subscriber should be informed when the network has accepted a control order for a supplementary service, e.g., activation, deactivation, registration, erasure. The responses to be given should be either a *specific recorded announcement*, e.g., "alarm call booked for 7.18", a *general positive recorded announcement*, e.g. "order executed" or a *positive indication tone*;
+
+11 that a subscriber – after having applied a valid *interrogation order* for a supplementary service – should be informed by the network whether the service is activated or not (status check) or, if the information dialled is identical to the stored information (data check) or, specifically what information is stored (data request).
+
+If a status check or data check applies, the responses to be given should be:
+
+- either a *positive or negative general recorded announcement* e.g., "service (not) active" or "information dialled (not) identical to information stored",
+- or an appropriate *positive indication tone*,
+- or an appropriate *negative indication tone*.
+
+If a data request applies, the response should be a *specific recorded announcement* e.g. "alarm call booked for 7.18, 9.30 and 12.35" or "no alarm call booked".
+
+12 that a busy subscriber, having the service "call waiting" activated, should be informed that an incoming call is waiting. The response is *call waiting tone*;
+
+13 that when the called number cannot be reached or a control order for activation, registration, deactivation, interrogation, or erasure for a supplementary service cannot be executed by the network in one attempt, due to "short-term system nonavailability" but a repeated attempt within a short time may be successful, a *congestion tone* should be given. This condition applies, for example, if short-term congestion of switching equipment, circuits or memory storage capacity occurs;
+
+14 that when the called number cannot be reached or a control order for a supplementary service cannot be executed in one attempt due to "recognized long-term nonavailability" and a repeated attempt would have no or small probability of success for a longer period of time (e.g., a few hours), the preferred response is a *specific recorded announcement*, e.g., "the called number is not obtainable because of a network fault, please call again after (1) hour". Alternatively, a *general recorded announcement* or *special information tone* may be used.
+
+This condition applies when:
+
+- a number is out of order for technical reasons;
+- where switching equipment or circuits or memory storage capacity will not be available for at least a few hours.
+
+15 that when the called number cannot be reached in one attempt because of an unresolved condition of the called number due to administrative reasons, the preferred response is a *specific recorded announcement* e.g., "the number has been changed, the new number is 12345". Alternatively, a *general recorded announcement* or *special information tone* may be used.
+
+This condition applies when:
+
+- a number is out of order for administrative reasons;
+- a number is not yet connected;
+- a number has changed.
+
+16 that when the information dialled by the subscriber, for set-up of an ordinary telephone call or to order a supplementary service, is not valid or cannot be accepted by the network from that particular line and the subscriber should check his information and/or his instructions before making a new attempt:
+
+- the preferred response is a *specific recorded announcement*, e.g., "In international dialling to this country the trunk prefix 0 should be deleted";
+- the accepted response is a general negative announcement, e.g., "You have dialled incorrect information, please consult your instructions". For PABXs a *negative indication tone* may be used;
+- the exceptional response is a special information tone.
+
+This condition applies when the number dialled:
+
+- is non-existing,
+- is barred for calls from a particular line,
+
+- contains an incorrect prefix,
+  - is a control order for a service which is not provided to the particular line.
+- 17 that when it is desirable to inform the subscriber to continue dialling during the ordering of a supplementary service in the conversational mode, the response to be given should be either a *specific recorded announcement* followed by the appropriate dial tone, or a *second dial tone*;
+- 18 that an indication should be given when a payphone user is required to make a payment during a call. The response to be given should be either a *specific recorded announcement* or a *pay tone*;
+- 19 that an indication should be given to a public network operator when handling a call from or to a payphone, and that where a tone is used:
+- the preferred response is *payphone recognition tone*.
+- 20 that when a subscriber is asked to speak so as to be recorded by a recording machine, a tone should be given to inform him when to begin to speak; the response to be used is the *record tone*;
+- 21 that when the privacy of a conversation on a call cannot be ensured, e.g., because of the intrusion of an operator, the preferred response is the *intrusion tone* given to both subscribers;
+- 22 that when the privacy of a conversation on a call cannot be ensured, e.g., because of the presence of a recording machine, the preferred response is the *warning tone*;
+- 23 that all the above-mentioned tones should be different.
+
+## Annex A
+
+### List of tones and announcements used as indications to telephone subscribers
+
+NOTE – This annex is provided to explain the terms in this Recommendation and some related terms. It is not a definitive list and additional refinement will be undertaken as part of future studies.
+
+### A.1 Basic terms
+
+#### A.1.1 audible indication
+
+*F: indication audible*
+
+*S: indicación audible*
+
+An audible indication is understood to be a sound composed of frequencies within the range 300-3400 Hz which is used to inform the user about the state of a telephone call or supplementary service.
+
+#### A.1.2 tone
+
+*F: tonalité*
+
+*S: tono*
+
+A tone is an audible indication comprising a small number of discrete frequencies, but excluding speech.
+
+#### A.1.3 recorded announcement
+
+*F: annonce enregistrée*
+
+*S: anuncio grabado*
+
+An audible indication in the form of speech.
+
+#### **A.1.4 call information**
+
+*F: information d'appel*
+
+*S: información de llamada*
+
+Call information includes normal address information, control codes for supplementary services, and other information dialled or keyed by the subscriber.
+
+### **A.2 Tones**
+
+#### **A.2.1 dial tone**
+
+*F: tonalité d'invitation*
+
+*S: tono de invitación a marcar*
+
+A tone advising that the exchange is ready to receive call information and inviting the user to start sending call information.
+
+#### **A.2.2 PABX internal dial tone**
+
+*F: tonalité d'invitation interne de commutateur privé*
+
+*S: tono de marcar interno de centralita privada automática, tono de invitación a marcar interno de centralita privada automática conectadas a la red pública*
+
+A tone advising that the PABX is ready to receive call information and inviting the user to start sending call information.
+
+#### **A.2.3 special dial tone**
+
+*F: tonalité d'invitation spéciale*
+
+*S: tono especial de invitación a marcar*
+
+A tone advising that the exchange is ready to receive call information and inviting the user to start sending call information, at the same time reminding the user that special conditions apply to the termination from which the call is being made.
+
+#### **A.2.4 second dial tone**
+
+*F: seconde tonalité d'invitation*
+
+*S: segundo tono de invitación a marcar*
+
+A tone advising the caller that the network has accepted the call information already sent and asking the caller to provide more information.
+
+#### **A.2.5 ringing tone**
+
+*F: tonalité de retour d'appel*
+
+*S: tono de llamada*
+
+A tone advising the caller that a connection has been made and that a calling signal is being applied to a telephone number or service point.
+
+#### **A.2.6 special ringing tone**
+
+*F: tonalité spéciale de retour d'appel*
+
+*S: tono especial de llamada*
+
+A tone advising the caller that the exchange of the called number has some special service in effect (such as Call Forwarding of Call Waiting) and that an appropriate calling signal is being applied and therefore the caller should wait for an answer.
+
+#### **A.2.7 busy tone**
+
+*F: tonalité d'occupation*
+
+*S: tono de ocupado*
+
+A tone advising the caller that the telephone number is busy.
+
+#### **A.2.8 congestion tone**
+
+*F: tonalité d'encombremment*
+
+*S: tono de congestión*
+
+A tone advising the caller that the groups of lines or switching equipment necessary for the setting-up of the required call or for the use of a specific service are temporarily engaged.
+
+#### **A.2.9 special information tone**
+
+*F: tonalité spéciale d'information*
+
+*S: tono especial de información*
+
+A tone advising the caller that the called number cannot be reached for reasons other than "subscriber busy" or "congestion".
+
+The tone may also be used in conjunction with recorded announcements to signify that what the caller is about to hear is a recording. It should always be used to precede all call failure announcements.
+
+#### **A.2.10 warning tone**
+
+*F: tonalité d'avertissement*
+
+*S: tono de aviso*
+
+A tone warning participants in a call that privacy of a conversation cannot be ensured where a recording machine is being used.
+
+#### **A.2.11 intrusion tone**
+
+*F: tonalité d'intrusion*
+
+*S: tono de intervención*
+
+A tone advising participants during a call that the privacy of the conversation has been breached, e.g. by the intervention of an operator.
+
+#### **A.2.12 call waiting tone**
+
+*F: tonalité d'appel en instance*
+
+*S: tono de indicación de llamada en espera*
+
+A tone advising the user of the call waiting supplementary service who is engaged on a call that someone is attempting to call his number.
+
+#### **A.2.13 pay tone**
+
+*F: tonalité de paiement*
+
+*S: tono de pago*
+
+A tone advising users of a payphone that a payment is required.
+
+#### **A.2.14 payphone recognition tone**
+
+*F: tonalité d'identification de publiphone*
+
+*S: tono de identificación de teléfono de previo pago*
+
+A tone advising a public exchange operator that the termination to or from which connection is sought is identified as a payphone.
+
+#### **A.2.15 comfort tone**
+
+*F: tonalité d'attente*
+
+*S: tono de paciencia*
+
+A tone advising that the call is being processed and that the caller should wait.
+
+#### **A.2.16 tone on hold**
+
+*F: tonalité de garde*
+
+*S: tono de retención*
+
+A tone used to reassure a calling subscriber who has been placed on "hold" by a subscriber with PBX or other facilities.
+
+#### **A.2.17 record tone**
+
+*F: tonalité d'enregistrement*
+
+*S: tono de grabación*
+
+A tone generated by automatic answering equipment to inform the calling subscriber when to begin a message which will be recorded.
+
+#### **A.2.18 caller waiting tone**
+
+*F: tonalité d'attente de l'appelant*
+
+*S: tono de indicación de llamada en espera para el llamande*
+
+A tone advising a caller that a called station, though busy, has a call waiting service active.
+
+#### **A.2.19 positive indication tone**
+
+*F: tonalité d'indication positive*
+
+*S: tono de indicación positivo*
+
+A tone telling a subscriber controlling a supplementary service that the control procedure has been successfully completed and accepted.
+
+#### **A.2.20 negative indication tone**
+
+*F: tonalité d'indication négative*
+
+*S: tono de indicación negativo*
+
+A tone advising a subscriber that the request for service cannot be accepted.
+
+### **A.3 Recorded announcements**
+
+#### **A.3.1 general recorded announcement**
+
+*F: annonce enregistrée générale*
+
+*S: anuncio grabado general*
+
+A recorded announcement giving general information about a call attempt or control order.
+
+#### **A.3.2 general positive recorded announcement**
+
+*F: annonce enregistrée générale positive*
+
+*S: anuncio grabado general positivo*
+
+A recorded announcement given to the user of a supplementary service to advise that the request has been accepted.
+
+*Example*
+
+"Your order has been executed."
+
+#### **A.3.3 general negative recorded announcement**
+
+*F: annonce enregistrée générale négative*
+
+*S: anuncio grabado general negativo*
+
+A recorded announcement given to the user of a supplementary service to advise that the request cannot be executed or that the call cannot be completed.
+
+##### *Examples*
+
+"Your order cannot be executed."
+
+"Your call cannot be completed at this time."
+
+"Please try again."
+
+#### **A.3.4 specific recorded announcement**
+
+*F: annonce enregistrée spécifique*
+
+*S: anuncio grabado específico*
+
+A recorded announcement giving specific information about a call attempt or control order.
+
+#### **A.3.5 specific positive recorded announcement without supplementary information**
+
+*F: annonce enregistrée spécifique positive sans information supplémentaire*
+
+*S: anuncio grabado específico positivo sin información suplementaria*
+
+A recorded announcement indicating to the user that the request for a particular supplementary service has been accepted.
+
+##### *Example*
+
+"The call barring service is now in operation."
+
+#### **A.3.6 specific negative recorded announcement without supplementary information**
+
+*F: annonce enregistrée spécifique négative sans information supplémentaire*
+
+*S: anuncio grabado específico negativo sin información suplementaria*
+
+A recorded announcement indicating to the user that the request for a particular supplementary service cannot be executed or that the call cannot be completed.
+
+##### *Examples*
+
+"Your order for call transfer cannot be executed."
+
+"The called number is not obtainable because of a network fault."
+
+#### **A.3.7 specific positive recorded announcement with supplementary information**
+
+*F: annonce enregistrée spécifique positive avec information supplémentaire*
+
+*S: anuncio grabado específico positivo con información suplementaria*
+
+A recorded announcement complete with the supplementary information received indicating to the user that a certain condition is being established.
+
+##### *Example*
+
+"An alarm call is booked for 6.30."
+
+# ITU-T RECOMMENDATIONS SERIES
+
+|                 |                                                                                                                                |
+|-----------------|--------------------------------------------------------------------------------------------------------------------------------|
+| Series A        | Organization of the work of the ITU-T                                                                                          |
+| Series B        | Means of expression: definitions, symbols, classification                                                                      |
+| Series C        | General telecommunication statistics                                                                                           |
+| Series D        | General tariff principles                                                                                                      |
+| <b>Series E</b> | <b>Overall network operation, telephone service, service operation and human factors</b>                                       |
+| Series F        | Non-telephone telecommunication services                                                                                       |
+| Series G        | Transmission systems and media, digital systems and networks                                                                   |
+| Series H        | Audiovisual and multimedia systems                                                                                             |
+| Series I        | Integrated services digital network                                                                                            |
+| Series J        | Transmission of television, sound programme and other multimedia signals                                                       |
+| Series K        | Protection against interference                                                                                                |
+| Series L        | Construction, installation and protection of cables and other elements of outside plant                                        |
+| Series M        | TMN and network maintenance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits |
+| Series N        | Maintenance: international sound programme and television transmission circuits                                                |
+| Series O        | Specifications of measuring equipment                                                                                          |
+| Series P        | Telephone transmission quality, telephone installations, local line networks                                                   |
+| Series Q        | Switching and signalling                                                                                                       |
+| Series R        | Telegraph transmission                                                                                                         |
+| Series S        | Telegraph services terminal equipment                                                                                          |
+| Series T        | Terminals for telematic services                                                                                               |
+| Series U        | Telegraph switching                                                                                                            |
+| Series V        | Data communication over the telephone network                                                                                  |
+| Series X        | Data networks and open system communications                                                                                   |
+| Series Y        | Global information infrastructure                                                                                              |
+| Series Z        | Programming languages                                                                                                          |

marked/E/T-REC-E.190-202502-I_PDF-E/raw.md

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+
+
+## Recommendation**ITU-T E.190 (02/2025)**
+
+SERIES E: Overall network operation, telephone service, service operation and human factors
+
+International operation – Numbering plan of the international telephone service
+
+---
+
+**Principles and responsibilities for the allocation, reservation, assignment, reclamation and management of international telecommunication numbering, naming, addressing and identification (NNAI) resources**
+
+![ITU logo](0538daaa5583c23e17db3a12f2281a55_img.jpg)
+
+The logo of the International Telecommunication Union (ITU) is located in the bottom right corner. It features the letters "ITU" in a bold, blue, sans-serif font, superimposed on a stylized globe icon with intersecting lines.
+
+ITU logo
+
+## ITU-T E-SERIES RECOMMENDATIONS
+
+### Overall network operation, telephone service, service operation and human factors
+
+|                                                                                                      |                    |
+|------------------------------------------------------------------------------------------------------|--------------------|
+| INTERNATIONAL OPERATION                                                                              | E.100-E.229        |
+| Definitions                                                                                          | E.100-E.103        |
+| General provisions concerning Administrations                                                        | E.104-E.119        |
+| General provisions concerning users                                                                  | E.120-E.139        |
+| Operation of international telephone services                                                        | E.140-E.159        |
+| Numbering plan of the international telephone service                                                | E.160-E.169        |
+| International routing plan                                                                           | E.170-E.179        |
+| Tones in national signalling systems                                                                 | E.180-E.189        |
+| <b>Numbering plan of the international telephone service</b>                                         | <b>E.190-E.199</b> |
+| Maritime mobile service and public land mobile service                                               | E.200-E.229        |
+| OPERATIONAL PROVISIONS RELATING TO CHARGING AND ACCOUNTING IN THE<br>INTERNATIONAL TELEPHONE SERVICE | E.230-E.299        |
+| UTILIZATION OF THE INTERNATIONAL TELEPHONE NETWORK FOR NON-<br>TELEPHONY APPLICATIONS                | E.300-E.329        |
+| ISDN PROVISIONS CONCERNING USERS                                                                     | E.330-E.349        |
+| INTERNATIONAL ROUTING PLAN                                                                           | E.350-E.399        |
+| NETWORK MANAGEMENT                                                                                   | E.400-E.489        |
+| TRAFFIC ENGINEERING                                                                                  | E.490-E.799        |
+| QUALITY OF TELECOMMUNICATION SERVICES: CONCEPTS, MODELS,<br>OBJECTIVES AND DEPENDABILITY PLANNING    | E.800-E.899        |
+| OTHER                                                                                                | E.900-E.999        |
+| INTERNATIONAL OPERATION                                                                              | E.1000-E.1999      |
+| NETWORK MANAGEMENT                                                                                   | E.4000-E.4999      |
+
+For further details, please refer to the list of ITU-T Recommendations.
+
+## Recommendation ITU-T E.190
+
+# **Principles and responsibilities for the allocation, reservation, assignment, reclamation and management of international telecommunication numbering, naming, addressing and identification (NNAI) resources**
+
+## Summary
+
+Recommendation ITU-T E.190 contains the principles and responsibilities used in the allocation, assignment, reclamation and management of international telecommunication numbering, naming addressing and identification resources, e.g., Recommendations ITU-T E.164, ITU-T E.118.1, ITU-T E.218 and ITU-T E.212, under the auspices of the appropriate ITU-T study group.
+
+## History \*
+
+| Edition | Recommendation            | Approval   | Study Group | Unique ID          |
+|---------|---------------------------|------------|-------------|--------------------|
+| 1.0     | ITU-T E.190               | 1997-05-30 | 2           | 11.1002/1000/4045  |
+| 1.1     | ITU-T E.190 (1997) Amd. 1 | 2009-11-24 | 2           | 11.1002/1000/8784  |
+| 2.0     | ITU-T E.190               | 2025-02-14 | 2           | 11.1002/1000/16023 |
+
+## Keywords
+
+Allocation, assignment, management, principles, reclamation, reservation, responsibilities, NNAI resources.
+
+---
+
+\* To access the Recommendation, type the URL <https://handle.itu.int/> in the address field of your web browser, followed by the Recommendation's unique ID.
+
+## FOREWORD
+
+The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, and information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis.
+
+The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics.
+
+The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1.
+
+In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC.
+
+### NOTE
+
+In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some other obligatory language such as "must" and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party.
+
+## INTELLECTUAL PROPERTY RIGHTS
+
+ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process.
+
+As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents/software copyrights, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the appropriate ITU-T databases available via the ITU-T website at <https://www.itu.int/ITU-T/ipr/>.
+
+© ITU 2025
+
+All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU.
+
+## Table of Contents
+
+|                                                                                                                                             | Page |
+|---------------------------------------------------------------------------------------------------------------------------------------------|------|
+| 1 Introduction .....                                                                                                                        | 1    |
+| 2 Background.....                                                                                                                           | 1    |
+| 3 Scope .....                                                                                                                               | 1    |
+| 4 References.....                                                                                                                           | 2    |
+| 5 Definitions .....                                                                                                                         | 2    |
+| 6 Principles for the allocation, reservation, assignment, reclamation and management of international telecommunication NNAI resources..... | 3    |
+| 6.1 General .....                                                                                                                           | 3    |
+| 6.2 Principles .....                                                                                                                        | 3    |
+| 7 Responsibilities.....                                                                                                                     | 5    |
+| 7.1 Director of TSB .....                                                                                                                   | 5    |
+| 7.2 Appropriate ITU-T Study Group.....                                                                                                      | 5    |
+| 7.3 Administrator.....                                                                                                                      | 5    |
+| 7.4 Applicant .....                                                                                                                         | 6    |
+| 7.5 Assignee .....                                                                                                                          | 6    |
+| 8 Reconsideration process .....                                                                                                             | 6    |
+| 9 Rules relating to responsibilities.....                                                                                                   | 6    |
+
+
+
+## **Recommendation ITU-T E.190**
+
+# **Principles and responsibilities for the allocation, reservation, assignment, reclamation and management of international telecommunication numbering, naming, addressing and identification (NNAI) resources**
+
+## **1 Introduction**
+
+**1.1** This Recommendation will guide and assist the appropriate ITU-T Study Groups in finding a balance between the following interrelated issues:
+
+- the need for numbering resources both for geographic and non-geographic applications;
+- the need for efficient and effective use of numbering, naming, addressing and identification (NNAI) resources recognizing their finite nature;
+- the need for an agreed expansion plan for NNAI resources;
+- the need to ensure that adequate NNAI resources are guaranteed for current and future requirements.
+
+**1.2** International telecommunication numbering, naming, addressing and identification (NNAI) resources are assigned by the Director of TSB, following consultation with the appropriate ITU-T Study Groups and applicants concerned. The assignment of national numbers remains a national matter.
+
+**1.3** The NNAI principles included in this Recommendation serve as a framework on which to base NNAI assignment decisions for NNAI resources.
+
+**1.4** The development and maintenance of responsibilities and procedures for the management of international telecommunication NNAI resources are the shared responsibilities of the ITU-TSB and the technical/operational experts of the appropriate ITU-T Study Group.
+
+## **2 Background**
+
+**2.1** [WTSA Res.20] recognizes the responsibility of the Director of TSB and the relevant Member States for the allocation and assignment of future international telecommunication NNAI resources and related codes. The Director of TSB and the relevant ITU-T Study Groups are to ensure that procedures governing the allocation, reservation, assignment, management and reclamation of NNAI resources meet current and foreseeable operational considerations.
+
+Careful study has led to the determination that:
+
+**2.1.1** A set of NNAI principles for the management and assignment of international telecommunication NNAI resources under the auspices of the appropriate ITU-T Study Group is required.
+
+**2.1.2** Due to the introduction of new services, new applications for geographic and non-geographic NNAI resources, and changes in national boundaries, allocation, reservation, assignment, management and reclamation of international telecommunication NNAI resources for different applications are required.
+
+## **3 Scope**
+
+This Recommendation contains the principles used by the Director of TSB and the appropriate ITU-T Study Group in the allocation, reservation, assignment, management and reclamation of international telecommunication NNAI resources (e.g., [ITU-T E.164], [ITU-T E.212], [ITU-T E.218] and [ITU-T E.118.1]). Criteria for the assignment of NNAI resources are specified in the appropriate
+
+ITU-T Recommendations, including [ITU-T E.164.1], [ITU-T E.1120], [ITU-T E.169] and [ITU-T E.212].
+
+## 4 References
+
+The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation.
+
+- [ITU-T E.101] Recommendation ITU-T E.101 (2009), *Definitions of terms used for identifiers (names, numbers, addresses and other identifiers) for public telecommunication services and networks in the E-series Recommendations.*
+- [ITU-T E.118.1] Recommendation ITU-T E.118.1 (2023), *Allocation, assignment and management of global Issuer Identifier Numbers (IINs).*
+- [ITU-T E.152] Recommendation ITU-T E.152 (2006), *International freephone service.*
+- [ITU-T E.154] Recommendation ITU-T E.154 (1998), *International Shared Cost Service.*
+- [ITU-T E.155] Recommendation ITU-T E.155 (1998), *International Premium Rate Service.*
+- [ITU-T E.164] Recommendation ITU-T E.164 (2010), *The international public telecommunication numbering plan.*
+- [ITU-T E.164.1] Recommendation ITU-T E.164.1 (2008), *Criteria and procedures for the reservation, assignment and reclamation of E.164 country codes and associated identification codes (ICs).*
+- [ITU-T E.169] Recommendation ITU-T E.169 (2002), *Application of Recommendation E.164 numbering plan for universal international numbers for international telecommunications services using country codes for global services.*
+- [ITU-T E.191] Recommendation ITU-T E.191 (2000), *B-ISDN addressing.*
+- [ITU-T E.212] Recommendation ITU-T E.212 (2024), *The international identification plan for public networks and subscriptions.*
+- [ITU-T E.218] Recommendation ITU-T E.218 (2024), *Management of the allocation of terrestrial trunk radio Mobile Country Codes.*
+- [ITU-T E.1120] Recommendation ITU-T E.1120 (2025), *Assignment procedures for international telecommunications Numbering, Naming, Addressing and Identification (NNAI) resources.*
+- [ITU-T E.1121] Recommendation ITU-T E.1121 (2024), *Mechanisms and processes for audits of assigned ITU-T international naming, numbering, addressing and identification (NNAI) resources.*
+- [WTSA Res.20] WTSA Resolution 20 (Rev. New Delhi, 2024), *Procedures for allocation and management of international telecommunication numbering, naming, addressing and identification resources.*
+
+## 5 Definitions
+
+Definitions for terms used can be found in [ITU-T E.101].
+
+## **6 Principles for the allocation, reservation, assignment, reclamation and management of international telecommunication NNAI resources**
+
+### **6.1 General**
+
+The purpose of the principles, presented in clause 6.2, is to establish the consistent and fair management and assignment of international telecommunication NNAI resources. All these principles should be utilized by the Director of TSB, the appropriate ITU-T Study Groups, the resource administrator (e.g., the national numbering plan administrator (NPA)), the resource applicant and the resource assignee.
+
+If the NNAI resource(s) is provided:
+
+- i) nationally;
+- ii) within an integrated numbering plan; or
+- iii) across multiple countries with diverse or integrated numbering plans,
+
+then the application for NNAI, and of these principles, shall be addressed respectively to:
+
+- i) the national numbering plan administrator (NPA);
+- ii) the integrated numbering plan administrator;
+- iii) the Director of TSB.
+
+All principles listed in clause 6.2 have equal importance.
+
+### **6.2 Principles**
+
+#### **6.2.1 Principle 1: Adequate NNAI resources must be available to enable the provision of public telecommunications services**
+
+The appropriate ITU-T Study Group has the responsibility to ensure that there is an adequate supply of international telecommunication NNAI resources available to meet the needs of the telecommunications market, the provisioning of services, and to enable the development of telecommunications.
+
+Conservation, unto itself, is not a valid reason to deny valid applications for numbering resources.
+
+#### **6.2.2 Principle 2: NNAI resources are assigned to facilitate the provisioning of public telecommunications services**
+
+International telecommunication NNAI resources exist for, and should be assigned to, serve the needs of the telecommunications market for the evolution of services, the introduction of geographic and non-geographic applications, and changes in national boundaries.
+
+#### **6.2.3 Principle 3: NNAI resources are to be efficiently utilized and managed**
+
+International telecommunication NNAI resources must be assigned and used in a manner that is effective for the telecommunications market and efficient to ensure that finite resources are not unduly wasted. The appropriate ITU-T Study Group shall ensure that any ITU-T Recommendation it approves in respect of NNAI resource assignment is effective for the telecommunications market and efficiently utilizes finite resources to prevent unnecessary wastage. In addition, the appropriate ITU-T Study Group should also minimize the cost to, and impact on, the telecommunications market while facilitating suitable NNAI capacity.
+
+International telecommunication NNAI resources will not be allocated to the same service for which there is an existing international telecommunication NNAI resource already allocated from the same NNAI plan, for example, no country code should be allocated for a service for which a country code already exists unless the country code has been exhausted.
+
+International telecommunication NNAI resources will not be assigned to an applicant for use that duplicates an existing international telecommunication NNAI resource that has already been allocated, for example, an applicant for a code for networks intended to be used for freephone would duplicate the universal international freephone number (UIFN) and therefore not be acceptable.
+
+International telecommunication NNAI resources shall be assigned in accordance with the extent of service provision for which those resources are required, and by the appropriate NPA.
+
+The Director of TSB shall undertake regular audits of international telecommunication NNAI resources that are managed by the Director of TSB and appropriate study group.
+
+#### **6.2.4 Principle 4: NNAI resources are to be assigned with fairness and equity**
+
+International telecommunication NNAI resources shall be assigned in a fair and impartial manner to any applicant who conforms to the conditions established by this and other relevant E-series Recommendations.
+
+The Director of TSB in consultation with the appropriate ITU-T Study Group will be fair and equitable in the assignment of international telecommunication NNAI resources and will not discriminate among or between applicants or global services. Assignments will be in accordance with the criteria and procedures as specified in the relevant Recommendations and other means of publications provided by the appropriate ITU-T Study Group.
+
+#### **6.2.5 Principle 5: Assignment confers right of use of the resource but does not imply ownership by the assignee**
+
+International telecommunication NNAI resources are to be administered for the overall good and use of the telecommunications market, and as such, are not to be considered "owned" by the assignee. Assignment of the numbering resource by the Director of TSB confers right of use of the resources only for the specific application.
+
+Additionally, there may be circumstances when the ITU-T must modify the assigned numbering resource in the interest of the telecommunications market, e.g., need to expand the resource.
+
+#### **6.2.6 Principle 6: Use of international telecommunication NNAI resources**
+
+International telecommunication NNAI resources will only be utilized by the assignee for the specific application for which they have been assigned by the Director of TSB.
+
+Country codes shall only be assigned from the list of country codes identified as spare codes.
+
+Upon request for NNAI resources, the assignee is obliged to demonstrate to the administrator, the Director of TSB, in consultation with the appropriate ITU-T Study Group that NNAI resources are or will be properly used, that is, the service(s) has been or will be established within the time stated in the application for the NNAI resource, and the NNAI resource is or will be used for the specific application quoted in the applicant's request.
+
+International telecommunication NNAI resources, assigned by the Director of TSB, may not be sold, licensed or traded. Nor may they be transferred, except in the case of a merger, acquisition, or joint venture. Any such transfer shall be agreed by the Director of TSB in accordance with relevant ITU-T Recommendations.
+
+#### **6.2.7 Principle 7: Reclamation of assigned international telecommunication NNAI resources**
+
+The assigned NNAI resource will be subject to reclamation by the Director of TSB, if:
+
+- it is being used in a different way from that for which it was assigned;
+- service(s) has not been established at the time stated in the applicant's request;
+- the resources are being used by other than the assignee in a manner contrary to the relevant ITU-T Recommendations;
+
+- the assigned numbering resource is no longer required or in use by the assignee;
+- the assignee has not provided an annual confirmation of use where this is specified as part of the assignment in the relevant Recommendations;
+- annual membership fees are not paid by the initial payment due date<sup>1</sup>;
+- the relevant ITU-T Recommendation that describes either the assignment process and criteria, or the service description, or both, for which the NNAI resource was assigned, is suppressed;
+- the result of an audit carried out by the Director of TSB, in consultation with the appropriate Study Group experts, confirms the results of said audit that in some instances result in reclamation being instigated and in conformance with rules within ITU-T Recommendations with regard to audits of NNAI resources;
+- the assignee does not conform to requests for material for an audit received from the Director of TSB.
+
+Partial reclamation of an assigned resource may also be considered if the amount of NNAI resource initially assigned is deemed by the Study Group to be far greater than those numbers through which the specific service is provided. In such cases, future growth of the service can be provided as a mitigation factor to reclamation, but this must be substantiated within a period set by the Study Group and backed up through audit figures provide annually throughout the designated period.
+
+## 7 Responsibilities
+
+The following responsibilities are general in nature. Specific responsibilities are further complemented in relevant Recommendations and documents (e.g., [WTSA Res.20]).
+
+The responsibilities also apply to those NNAI resources that are administered by a national NPA.
+
+### 7.1 Director of TSB
+
+Allocation, reservation, assignment, management and reclamation of NNAI resources are the responsibility of the Director of TSB in consultation with the relevant ITU-T Study Group, the relevant applicant, the relevant assignee, and if required, the relevant national NPAs.
+
+The Director of TSB also has the responsibility of undertaking audits of the assignee's use and management of NNAI resources assigned to entities other than Member States to ensure that the assigned resources are being used in accordance with the principles of this Recommendation. Such audits should be periodic or undertaken as a result of concerns advised to the Director of TSB by the appropriate Study Group, or directly from Sector Members and Member States.
+
+### 7.2 Appropriate ITU-T Study Group
+
+The Study Group shall be responsible for defining the recommendations related to procedures, actions or processes to manage telecommunication/ICT services and networks. This includes technical and operational advice to the Director of TSB relative to the allocation, reservation, assignment, management and reclamation of that resource. The appropriate ITU-T Study Group should also ensure that development and planning of NNAI activities facilitate operational needs.
+
+### 7.3 Administrator
+
+It is the responsibility of the administrator to perform all administration functions in a timely manner, including the validation and processing of applications, numbering resource reclamation procedures when appropriate and periodically publishing an up-to-date list of assignments and reclamations. The
+
+---
+
+<sup>1</sup> At the time of publication, the initial due date for payment of ITU membership fees is 31 March each year.
+
+administrator of the resource must also be prepared to accept and handle proprietary information in a confidential manner.
+
+The Director of TSB is the administrator for NNAI resources that are assigned to entities other than Member States.
+
+### **7.4 Applicant**
+
+The applicant must comply with the assignment criteria and conditions. This includes adherence to all ITU-T Recommendations relative to each service and the criteria assignment of the specific NNAI resource being applied for. The NNAI resource administrator shall be notified of any changes in information associated with the resource assignment immediately as they occur.
+
+The applicant shall also ensure they are entitled per the appropriate national regulations to operate in the area(s) they intend to provide service.
+
+The applicant shall notify the Director of TSB of any intention to sub-assign a resource to a third-party entity prior to making that assignment. In such cases the Director of TSB shall seek advice from the NCT (Numbering Coordination Team as defined in Appendix I of [ITU-T E.1120]) before responding back.
+
+### **7.5 Assignee**
+
+The assignee is responsible for the effective and efficient management and use of that part of the NNAI resource which is under their responsibility. The international telecommunication NNAI resource will be subject to reclamation if there is no longer a recognized need, or the resource is being used in a manner which differs from the stated purpose or assignment criteria, or the Recommendation under which the assignment was made is suppressed, or where the results of an audit indicate reclamation.
+
+## **8 Reconsideration process**
+
+**8.1** If a request for an NNAI resource assignment is subject to denial or the NNAI resource is subject to reclamation from an assignee, then the process for reclamation shall be followed for reconsideration of the Director of TSB's decision.
+
+**8.2** The applicant shall be afforded the rationale for the request denial or notification of reclamation, and shall be given the opportunity to amend and re-submit an application to address the denial or reclamation rationale.
+
+**8.3** If the applicant chooses to initiate the reconsideration process, the steps are:
+
+- direct communication between the Director of TSB, in consultation with the Chair of the relevant SG and their advisors, e.g., NCT and the applicant, if unresolved in a reasonable period of time;
+- consultation between the Director of TSB and the appropriate ITU-T Study Group;
+- contributing to, and participation at, the relevant Study Group meeting.
+
+## **9 Rules relating to responsibilities**
+
+This clause details specific rules that relate to the responsibilities set out in clause 7.
+
+Required audits as specified under Principle 3 shall be conducted in conformance with rules within ITU-T Recommendations with regard to audits of NNAI resources.
+
+The following information must be maintained by all entities responsible for the management of NNAI resources:
+
+- The total amount of numbers assigned.
+
+- The total amount of numbers through which the agreed services are being provided.
+- Confirmation that the numbers assigned are only being used for the services agreed for use when the numbers were originally assigned to the applicant, or as agreed with the Director of TSB at a later date.
+- Details of any third-party entity who have been sub-assigned numbers from that range and if so, details of when those numbers were sub-assigned, the numbering range sub-assigned and confirmation that they are only providing services for which the original assignment made by the Director of TSB specified.
+
+
+
+
+
+## SERIES OF ITU-T RECOMMENDATIONS
+
+|                 |                                                                                                                                                           |
+|-----------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Series A        | Organization of the work of ITU-T                                                                                                                         |
+| Series D        | Tariff and accounting principles and international telecommunication/ICT economic and policy issues                                                       |
+| <b>Series E</b> | <b>Overall network operation, telephone service, service operation and human factors</b>                                                                  |
+| Series F        | Non-telephone telecommunication services                                                                                                                  |
+| Series G        | Transmission systems and media, digital systems and networks                                                                                              |
+| Series H        | Audiovisual and multimedia systems                                                                                                                        |
+| Series I        | Integrated services digital network                                                                                                                       |
+| Series J        | Cable networks and transmission of television, sound programme and other multimedia signals                                                               |
+| Series K        | Protection against interference                                                                                                                           |
+| Series L        | Environment and ICTs, climate change, e-waste, energy efficiency; construction, installation and protection of cables and other elements of outside plant |
+| Series M        | Telecommunication management, including TMN and network maintenance                                                                                       |
+| Series N        | Maintenance: international sound programme and television transmission circuits                                                                           |
+| Series O        | Specifications of measuring equipment                                                                                                                     |
+| Series P        | Telephone transmission quality, telephone installations, local line networks                                                                              |
+| Series Q        | Switching and signalling, and associated measurements and tests                                                                                           |
+| Series R        | Telegraph transmission                                                                                                                                    |
+| Series S        | Telegraph services terminal equipment                                                                                                                     |
+| Series T        | Terminals for telematic services                                                                                                                          |
+| Series U        | Telegraph switching                                                                                                                                       |
+| Series V        | Data communication over the telephone network                                                                                                             |
+| Series X        | Data networks, open system communications and security                                                                                                    |
+| Series Y        | Global information infrastructure, Internet protocol aspects, next-generation networks, Internet of Things and smart cities                               |
+| Series Z        | Languages and general software aspects for telecommunication systems                                                                                      |

marked/E/T-REC-E.191.1-200102-I_PDF-E/raw.md

@@ -0,0 +1,394 @@
+
+
+![ITU logo: A globe with a lightning bolt and the letters ITU.](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg)
+
+ITU logo: A globe with a lightning bolt and the letters ITU.
+
+INTERNATIONAL TELECOMMUNICATION UNION
+
+**ITU-T**
+
+**E.191.1**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+(02/2001)
+
+SERIES E: OVERALL NETWORK OPERATION,  
+TELEPHONE SERVICE, SERVICE OPERATION AND  
+HUMAN FACTORS
+
+International operation – Numbering plan of the  
+international telephone service
+
+---
+
+**Criteria and procedures for the allocation of the  
+ITU-T International Network Designator  
+addresses**
+
+ITU-T Recommendation E.191.1
+
+---
+
+# **OVERALL NETWORK OPERATION, TELEPHONE SERVICE, SERVICE OPERATION AND HUMAN FACTORS**
+
+|                                                                                                          |                    |
+|----------------------------------------------------------------------------------------------------------|--------------------|
+| <b>INTERNATIONAL OPERATION</b>                                                                           |                    |
+| Definitions                                                                                              | E.100–E.103        |
+| General provisions concerning Administrations                                                            | E.104–E.119        |
+| General provisions concerning users                                                                      | E.120–E.139        |
+| Operation of international telephone services                                                            | E.140–E.159        |
+| Numbering plan of the international telephone service                                                    | E.160–E.169        |
+| International routing plan                                                                               | E.170–E.179        |
+| Tones in national signalling systems                                                                     | E.180–E.189        |
+| <b>Numbering plan of the international telephone service</b>                                             | <b>E.190–E.199</b> |
+| Maritime mobile service and public land mobile service                                                   | E.200–E.229        |
+| <b>OPERATIONAL PROVISIONS RELATING TO CHARGING AND ACCOUNTING IN THE INTERNATIONAL TELEPHONE SERVICE</b> |                    |
+| Charging in the international telephone service                                                          | E.230–E.249        |
+| Measuring and recording call durations for accounting purposes                                           | E.260–E.269        |
+| <b>UTILIZATION OF THE INTERNATIONAL TELEPHONE NETWORK FOR NON-TELEPHONY APPLICATIONS</b>                 |                    |
+| General                                                                                                  | E.300–E.319        |
+| Phototelegraphy                                                                                          | E.320–E.329        |
+| <b>ISDN PROVISIONS CONCERNING USERS</b>                                                                  | E.330–E.349        |
+| <b>INTERNATIONAL ROUTING PLAN</b>                                                                        | E.350–E.399        |
+| <b>NETWORK MANAGEMENT</b>                                                                                |                    |
+| International service statistics                                                                         | E.400–E.409        |
+| International network management                                                                         | E.410–E.419        |
+| Checking the quality of the international telephone service                                              | E.420–E.489        |
+| <b>TRAFFIC ENGINEERING</b>                                                                               |                    |
+| Measurement and recording of traffic                                                                     | E.490–E.505        |
+| Forecasting of traffic                                                                                   | E.506–E.509        |
+| Determination of the number of circuits in manual operation                                              | E.510–E.519        |
+| Determination of the number of circuits in automatic and semi-automatic operation                        | E.520–E.539        |
+| Grade of service                                                                                         | E.540–E.599        |
+| Definitions                                                                                              | E.600–E.649        |
+| Traffic engineering for IP-networks                                                                      | E.650–E.699        |
+| ISDN traffic engineering                                                                                 | E.700–E.749        |
+| Mobile network traffic engineering                                                                       | E.750–E.799        |
+| <b>QUALITY OF TELECOMMUNICATION SERVICES: CONCEPTS, MODELS, OBJECTIVES AND DEPENDABILITY PLANNING</b>    |                    |
+| Terms and definitions related to the quality of telecommunication services                               | E.800–E.809        |
+| Models for telecommunication services                                                                    | E.810–E.844        |
+| Objectives for quality of service and related concepts of telecommunication services                     | E.845–E.859        |
+| Use of quality of service objectives for planning of telecommunication networks                          | E.860–E.879        |
+| Field data collection and evaluation on the performance of equipment, networks and services              | E.880–E.899        |
+
+*For further details, please refer to the list of ITU-T Recommendations.*
+
+# **ITU-T Recommendation E.191.1**
+
+## **Criteria and procedures for the allocation of the ITU-T International Network Designator addresses**
+
+## **Summary**
+
+This Recommendation details the criteria and procedures for the allocation of the ITU-T International Network Designator (IND) addresses to ATM Services Providers (ASPs) for ATM End System Addresses (AESAs).
+
+### **Source**
+
+ITU-T Recommendation E.191.1 was prepared by ITU-T Study Group 2 (2001-2004) and approved under the WTSA Resolution 1 procedure on 2 February 2001.
+
+## FOREWORD
+
+The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis.
+
+The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics.
+
+The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1.
+
+In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC.
+
+## NOTE
+
+In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+## INTELLECTUAL PROPERTY RIGHTS
+
+ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process.
+
+As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database.
+
+© ITU 2002
+
+All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU.
+
+## CONTENTS
+
+###### Page
+
+|     |                                                                                                                |   |
+|-----|----------------------------------------------------------------------------------------------------------------|---|
+| 1   | Scope.....                                                                                                     | 1 |
+| 2   | References.....                                                                                                | 1 |
+| 3   | Definitions .....                                                                                              | 1 |
+| 4   | Abbreviations.....                                                                                             | 1 |
+| 5   | ITU IND AESA principles and format.....                                                                        | 2 |
+| 5.1 | ITU IND AESA format .....                                                                                      | 2 |
+| 5.2 | ITU IND AESA principles .....                                                                                  | 2 |
+| 6   | AESA identifier code assignment principles .....                                                               | 3 |
+| 7   | Applicant procedures .....                                                                                     | 3 |
+| 8   | Registrar procedures .....                                                                                     | 3 |
+|     | Annex A – IND Request Form (One IND request per form) .....                                                    | 5 |
+|     | Annex B – Eligibility criteria and procedures for the allocation of INDs to organizations other than ASP ..... | 6 |
+| B.1 | General guidelines .....                                                                                       | 6 |
+| B.2 | Eligibility criteria.....                                                                                      | 6 |
+| B.3 | Procedures for the allocation of INDs to other organizations .....                                             | 7 |
+| B.4 | Reclamation of INDs assigned to non-ASPs.....                                                                  | 7 |
+
+
+
+# ITU-T Recommendation E.191.1
+
+## Criteria and procedures for the allocation of the ITU-T International Network Designator addresses
+
+## 1 Scope
+
+This Recommendation details the criteria and procedures for the allocation of the ITU-T International Network Designator (IND) addresses to ATM Services Providers (ASPs) for ATM End System Addresses (AESA).
+
+# 2 References
+
+The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published.
+
+- ITU-T Recommendation E.191 (2000), *B-ISDN addressing*.
+- ITU-T Recommendation X.213 (1995) ISO/IEC 8348:1996, *Information technology – Open Systems Interconnection – Network Service Definition. Annex A: Network Layer Addressing*.
+- ATM Forum AF-RA-0106.000 (1999), *ATM Forum Addressing: Reference Guide*.
+
+## 3 Definitions
+
+This Recommendation defines the following terms:
+
+- 3.1 AESA:** An ATM End System Address as described in ITU-T E.191.
+- 3.2 ITU IND AESA:** A type of AESA that has been defined by ITU.
+- 3.3 ATM service provider (ASP):** Provides public correspondence services between end users, private networks or other ATM Service Providers, using an ATM network.
+- 3.4 an applicant:** Includes any company, corporation or governmental organization that operates a public correspondence service. Whilst the ITU IND is typically allocated to an ASP, it may also be allocated to other organizations who are able to demonstrate that the other AESA formats do not meet their addressing requirements and who affirm that the ITU IND will be used to facilitate interworking with the public network.
+
+## 4 Abbreviations
+
+This Recommendation uses the following abbreviations:
+
+|      |                                 |
+|------|---------------------------------|
+| AESA | ATM End System Address          |
+| AFI  | Authority and Format Identifier |
+| ASP  | ATM Service Provider            |
+| ATM  | Asynchronous Transfer Mode      |
+| DSP  | Domain Specific Part            |
+| IDI  | Initial Domain Identifier       |
+
+|       |                                                                                   |
+|-------|-----------------------------------------------------------------------------------|
+| IND   | International Network Designator                                                  |
+| ISO   | International Organization for Standardization                                    |
+| ITU-T | International Telecommunication Union – Telecommunications Standardization Sector |
+| TSB   | Telecommunication Standardization Bureau                                          |
+
+## 5 ITU IND AESA principles and format
+
+### 5.1 ITU IND AESA format
+
+Figure 1 describes the format of an ITU IND AESA. The whole AESA is 20 octets or 40 hex (0-F) characters.
+
+![Diagram of ITU IND AESA format showing AFI (1 octet), IDI = IND (3 octets), and DSP (16 octets) fields, totaling 20 octets (40 hex).](35a7554182eb055209552843f341a1ae_img.jpg)
+
+|     |           |            |
+|-----|-----------|------------|
+| AFI | IDI = IND | <u>DSP</u> |
+|-----|-----------|------------|
+
+1 octet      3 octets  
+ └─ 20 octets (40 hex) ─┘  
+ T0208420-02
+
+Diagram of ITU IND AESA format showing AFI (1 octet), IDI = IND (3 octets), and DSP (16 octets) fields, totaling 20 octets (40 hex).
+
+**Figure 1/E.191.1 – An ITU IND AESA**
+
+Authority and Format Identifier (AFI) – is described in ITU-T E.191 and is a one octet (2-digits) field allocated jointly by ISO and ITU-T to denote an ITU IND AESA. The value of this field is 76 and 77 for individual addresses and E2 and E3 for group addresses (See ITU-T X.213, Table A.2), where 76 and E2 indicates decimal encoding of the DSP and 77 and E3 indicates binary encoding of the DSP.
+
+Initial Domain Identifier (IDI) – is described in ITU-T E.191 and is the AESA International Network Designator (IND) field allocated by the ITU-T to the applicant. The length of this field is three octets (6 digits).
+
+Domain Specific Part (DSP) – is described in ITU-T E.191 and is for allocation by the applicant. The length on this field is 16 octets.
+
+### 5.2 ITU IND AESA principles
+
+The following principles were used in the development of the ITU IND AESA format and assignment procedures, and should be considered with the use of ITU IND AESAs. For the remainder of this Recommendation, the term ITU-T IND will be referred to as IND:
+
+- an IND is allocated to an ASP;
+- a single IND is allocated to an ASP for their networks. One IND code should be used for all networks owned by that ASP. In unusual circumstances another code may be allocated to the ASP but it is up to the applicant to prove the requirement for more than one code. Due to the nature of the resource, no reservation period is required. Consequently, once the application is approved, the IND resource will be assigned;
+- once an IND is allocated it should not be transferred to another ASP;
+- an ASP need not be providing an ATM interface service directly to their customers in order to qualify for an ASP code.
+
+## **6 AESA identifier code assignment principles**
+
+- a) All assigned INDs must be used in conformance with this Recommendation.
+- b) Applications for an IND will only be considered when a valid and complete IND Request Form (see Annex A) has been received from an Applicant by the Registrar.
+- c) INDs will be allocated in a sequential fashion, i.e. the applicant may not request a certain code.
+- d) INDs may not be sold, licensed, or traded. Nor may they be transferred, except in the case of a merger, acquisition, or joint venture. Any such transfer shall be notified to the Registrar.
+- e) The assignment of an IND by the Registrar does not create an ownership interest, right or claim to the IND on the part of the ASP. Its use shall be subject to the terms set forth herein.
+- f) The IND shall be unique to an ASP.
+- g) Any violation of these principles by the ASP of an IND will result in the Registrar reclaiming the assigned number.
+
+## **7 Applicant procedures**
+
+In most cases, the applicant would be the ASP. However, there may be circumstances when the applicant would apply on behalf of an ASP due to national requirements.
+
+- a) Submit valid requests for an IND in accordance with this Recommendation, using the particular ITU-T AESA format as described in 5.1. Invalid requests will be returned by the Registrar.
+- b) Send an IND Request Form, Part A (see Annex A), on behalf of the ASP, by facsimile or E-mail to the Registrar. The IND Request Form should be accompanied by evidence of payment of the registration application fee for the assignment of the IND by the Registrar. The ITU will notify Administrations of the amount of the registration application fee in the current Operational Bulletin of the ITU. Payment can be made either by accompanying each IND Request Form with payment of the registration application fee.
+- c) Accept IND Request Form, Part B, as the IND assignment confirmation from the Registrar, and notify the applicant.
+- d) Notify the Registrar of changes in information associated with the IND, e.g. change of name, address, using the IND Request Form, Part A.
+- e) The assignee will notify the Registrar via the IND Request Form, Part A, of the discontinued use of an IND.
+
+## **8 Registrar procedures**
+
+The function of the Registrar will be performed under the auspices of ITU. The Registrar has the responsibility for the processing, and associated administrative functions, of registration requests from applicants. The processing of registration requests will be performed in close cooperation and consultation with national Administrations, as required by national administrations. This Recommendation does not include the legal responsibilities of the Registrar. The Registrar will:
+
+- a) assign all INDs in a fair and unbiased manner;
+- b) allocate INDs in a sequential fashion;
+- c) validate the request for an IND in accordance with this Recommendation. Return request to the applicant if the application is not valid;
+
+- d) administer a single pool of INDs in a single database. The database requirements include:
+  - an entry for each assigned IND;
+  - the assignee's name;
+  - the applicant's contact name;
+  - date of assignment;
+  - historical information;
+  - allow for administering change information;
+  - allow an online view only capability to applicants.
+- e) receive all application requests by the applicant by facsimile with an IND Request Form, Part A or via E-mail. Inclusive payment of the registration application fee;
+- f) assign INDs on a "first come first served" basis. This means that the IND Application Forms received via facsimile or E-mail by the registrar, will be processed in order of receipt;
+- g) accept no verbal requests or inquiries, for available INDs;
+- h) allocate only one IND per ASP;
+- i) respond with an assignment to the applicant, within two working days of receipt of request with an IND request form, Part B, to acknowledge the assignment confirmation. Where a request for an IND is refused or delayed, the applicant should be informed of the reason;
+- j) update the IND database;
+- k) provide information to applicants on the application process;
+- l) recognizing a non-conforming use, the registrar will inform the applicant of the alleged misuse. The applicant will be afforded 30 days to either bring the IND into conformance or explain why the current use is conforming. If conformance is not achieved within 30 days, the IND will be reclaimed by the Registrar. The IND will immediately be disconnected and enter the ageing period;
+- m) accept notice of return of an IND via the IND Request Form, Part A. The IND will be placed in the ageing period on the date the Registrar receives the notification of disconnect;
+- n) when an existing IND is completely returned, the IND can be assigned to another ASP normally after a six-month ageing period;
+- o) the Registrar will send confirmation of the return of the IND to the applicant, via the IND Status Notification Form, Part B;
+- p) accept changes of information associated with INDs (e.g. change of name, address), via the IND Request Form, Part A;
+- q) monitor and audit the status of the IND resource and produce reports to the appropriate Study Group, including actual quantity of INDs assigned and growth statistics associated with those assignments;
+- r) publish a list of assigned INDs using an agreed method.
+
+## Annex A
+
+### IND Request Form
+
+(One IND request per form)
+
+#### Part A filled out by the Applicant
+
+|                      |       |                                          |       |
+|----------------------|-------|------------------------------------------|-------|
+| (Applicant)          | _____ | Transmittal date: (a)                    | _____ |
+| Company name (b)     | _____ | Send to:                                 |       |
+| Contact name (c)     | _____ | IND Registrar                            |       |
+| Address              | _____ | International Telecommunication Union    |       |
+| Telephone number (d) | _____ | Telecommunication Standardization Bureau |       |
+| Fax number           | _____ | CH-1211 GENEVA 20, Switzerland           |       |
+| E-mail address       | _____ | Fax: +41 22 730 6200                     |       |
+
+Request type (mark with an X): (e)      New       Change       Cancel
+
+Reason for change: (f) \_\_\_\_\_
+
+Proposed use of IND (Applicant must indicate that the IND is to be used or plans to be used in the provision of public correspondence services) \_\_\_\_\_
+
+Payment of the registration application fee: (o) \_\_\_\_\_ Swiss francs
+
+Specify the method of payment used:
+
+by bank transfer to ITU account No. [ ]
+
+major credit card
+
+#### Part B filled out by the Registrar to be returned to Applicant
+
+This IND is assigned: (b) \_\_\_\_\_ Transmittal date (a) \_\_\_\_\_
+
+The IND assignment was denied for the following reason: (c)
+
+Remarks: \_\_\_\_\_
+
+Signature (Applicant/Registrar)
+
+## Annex B
+
+### Eligibility criteria and procedures for the allocation of INDs to organizations other than ASP
+
+### B.1 General guidelines
+
+This annex defines eligibility criteria and procedures for the allocation of International Network Designator (IND) codes to organizations other than ATM service providers, in order that the ITU may efficiently and objectively handle applications for the assignment of such INDs in a timely manner. The IND codes are a common asset and not the property of any individual network operator, ITU Member state or other organization. Accordingly the INDs cannot be resold, traded or transferred and shall only be used for the purpose of network addressing.
+
+The ITU is responsible for the allocation of INDs. The ITU determines the eligibility criteria for the allocation of such INDs. The eligibility criteria may be modified, withdrawn, added to or further modified at any time, as needed, in accordance with the changing telecommunications environment.
+
+### B.2 Eligibility criteria
+
+Organizations other than ASPs requiring an IND code are required to demonstrate that they meet the eligibility criteria. No precedent should be attributed to any particular assignment for the purpose of supporting new assignments. As the number of available INDs is finite (1 000 000), it is important that the technical alternatives to the assignment of an IND code be ascertained. The technical alternatives to the assignment of an IND are given in ITU-T E.191. Organizations, which meet the following criteria, are eligible for consideration for the allocation of an IND code.
+
+#### a) *The status of the organization*
+
+The allocation may only be made to an organization (e.g. a registered business or public company). It may not be made to an individual.
+
+#### b) *Ability to interwork with public networks*
+
+The applicant should provide evidence that the allocated IND will be used to identify an existing or planned network. The organization's network must interwork or be connected with public networks. The application should be supported by the ATM Service Providers to whom the network is connected or interworks. However, it should be carefully noted that the allocation of a code to a non-ASP organization does not mandate that such codes will be used by other ASPs as the basis for routing of traffic across public networks.
+
+#### c) *Compliance with national regulations*
+
+The organization requesting an assignment must confirm that the use of the IND code would be in accordance with national laws and regulations where applicable.
+
+#### d) *Technical and operational considerations*
+
+There is a technical and operational benefit in using an IND code and, in particular, its use would facilitate interworking with the public network. The applicant must demonstrate the manner in which the network interworks (or plans to interwork) with ATM service provider's networks. It should be demonstrated that the use of an IND code is the most efficient and effective manner for providing addressing within the network and that the use of the other addressing schemes (e.g. ICD, DCC, IOTA) are seen as imposing limitations on the future technical development or commercial relationships that the network may wish to have with ASPs. In particular, issues such as the long-term stability of the network's addressing structure should be considered.
+
+### **B.3 Procedures for the allocation of INDs to other organizations**
+
+The assignment of an IND to an organization other than an ASP is administered by ITU.
+
+The process for the allocation of an IND is initiated by a written request to the Director of TSB from the organization and must be supported by the ATM Service Providers to whom the organization's network interwork or plans to interwork.
+
+The application procedures are detailed in clause 7 and the applicant must also submit the IND Request Form (Annex A).
+
+The allocation of an IND to a non-ASP may not be a straightforward matter. It may raise a number of technical issues. Accordingly, when the ITU-T TSB receives an application from a non-ASP, the TSB will ensure that appropriate discussion takes place between the TSB, the organization requesting the allocation, the relevant ASPs and Study Group experts, to ensure that any technical and operational requirements have been taken into consideration before the final assignment of the code is made. It is important that technical alternatives to the assignment of an IND code be ascertained. The onus is placed on the organization applying for an IND code to demonstrate that there is a technical and operational benefit to identify the network with an IND.
+
+If the TSB and the expert group (as detailed above) it has assembled, determine that the request for the assignment of an IND code meets the eligibility criteria in B.2, the relevant Study Group will advise the Director of TSB to approve the assignment.
+
+### **B.4 Reclamation of INDs assigned to non-ASPs**
+
+The IND codes will be recovered if not used, or no longer required by the assignee, or not used in accordance with these guidelines.
+
+
+
+
+
+# SERIES OF ITU-T RECOMMENDATIONS
+
+|                 |                                                                                                                                |
+|-----------------|--------------------------------------------------------------------------------------------------------------------------------|
+| Series A        | Organization of the work of ITU-T                                                                                              |
+| Series B        | Means of expression: definitions, symbols, classification                                                                      |
+| Series C        | General telecommunication statistics                                                                                           |
+| Series D        | General tariff principles                                                                                                      |
+| <b>Series E</b> | <b>Overall network operation, telephone service, service operation and human factors</b>                                       |
+| Series F        | Non-telephone telecommunication services                                                                                       |
+| Series G        | Transmission systems and media, digital systems and networks                                                                   |
+| Series H        | Audiovisual and multimedia systems                                                                                             |
+| Series I        | Integrated services digital network                                                                                            |
+| Series J        | Cable networks and transmission of television, sound programme and other multimedia signals                                    |
+| Series K        | Protection against interference                                                                                                |
+| Series L        | Construction, installation and protection of cables and other elements of outside plant                                        |
+| Series M        | TMN and network maintenance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits |
+| Series N        | Maintenance: international sound programme and television transmission circuits                                                |
+| Series O        | Specifications of measuring equipment                                                                                          |
+| Series P        | Telephone transmission quality, telephone installations, local line networks                                                   |
+| Series Q        | Switching and signalling                                                                                                       |
+| Series R        | Telegraph transmission                                                                                                         |
+| Series S        | Telegraph services terminal equipment                                                                                          |
+| Series T        | Terminals for telematic services                                                                                               |
+| Series U        | Telegraph switching                                                                                                            |
+| Series V        | Data communication over the telephone network                                                                                  |
+| Series X        | Data networks and open system communications                                                                                   |
+| Series Y        | Global information infrastructure and Internet protocol aspects                                                                |
+| Series Z        | Languages and general software aspects for telecommunication systems                                                           |

marked/E/T-REC-E.212-202406-I_PDF-E/raw.md

@@ -0,0 +1,917 @@
+
+
+# Recommendation**ITU-T E.212 (06/2024)**
+
+SERIES E: Overall network operation, telephone service, service operation and human factors
+
+International operation – Maritime mobile service and public land mobile service
+
+---
+
+### **The international identification plan for public networks and subscriptions**
+
+![ITU logo](0538daaa5583c23e17db3a12f2281a55_img.jpg)
+
+The logo of the International Telecommunication Union (ITU) is located in the bottom right corner. It features a blue globe with white lines representing latitude and longitude, and the letters 'ITU' in a bold, blue, sans-serif font overlaid on the globe.
+
+ITU logo
+
+## ITU-T E-SERIES RECOMMENDATIONS
+
+### Overall network operation, telephone service, service operation and human factors
+
+|                                                                                                   |                    |
+|---------------------------------------------------------------------------------------------------|--------------------|
+| INTERNATIONAL OPERATION                                                                           | E.100-E.229        |
+| Definitions                                                                                       | E.100-E.103        |
+| General provisions concerning Administrations                                                     | E.104-E.119        |
+| General provisions concerning users                                                               | E.120-E.139        |
+| Operation of international telephone services                                                     | E.140-E.159        |
+| Numbering plan of the international telephone service                                             | E.160-E.169        |
+| International routing plan                                                                        | E.170-E.179        |
+| Tones in national signalling systems                                                              | E.180-E.189        |
+| Numbering plan of the international telephone service                                             | E.190-E.199        |
+| <b>Maritime mobile service and public land mobile service</b>                                     | <b>E.200-E.229</b> |
+| OPERATIONAL PROVISIONS RELATING TO CHARGING AND ACCOUNTING IN THE INTERNATIONAL TELEPHONE SERVICE | E.230-E.299        |
+| UTILIZATION OF THE INTERNATIONAL TELEPHONE NETWORK FOR NON-TELEPHONY APPLICATIONS                 | E.300-E.329        |
+| ISDN PROVISIONS CONCERNING USERS                                                                  | E.330-E.349        |
+| INTERNATIONAL ROUTING PLAN                                                                        | E.350-E.399        |
+| NETWORK MANAGEMENT                                                                                | E.400-E.489        |
+| TRAFFIC ENGINEERING                                                                               | E.490-E.799        |
+| QUALITY OF TELECOMMUNICATION SERVICES: CONCEPTS, MODELS, OBJECTIVES AND DEPENDABILITY PLANNING    | E.800-E.899        |
+| OTHER                                                                                             | E.900-E.999        |
+| INTERNATIONAL OPERATION                                                                           | E.1000-E.1999      |
+| NETWORK MANAGEMENT                                                                                | E.4000-E.4999      |
+
+For further details, please refer to the list of ITU-T Recommendations.
+
+## Recommendation ITU-T E.212
+
+# The international identification plan for public networks and subscriptions
+
+## Summary
+
+Recommendation ITU-T E.212 defines a unique international identification plan for public fixed and mobile networks providing users with access to public telecommunication services. The ITU-T E.212 identification plan was originally developed for use in public land mobile networks (PLMNs). The plan is hierarchical and identifies geographical areas, networks and subscriptions. The main body of this Recommendation describes the pure identification plan.
+
+The 2024 revision of this Recommendation clarifies the conditions for reclamation in the case of non-payment of membership fees for mobile network codes (MNCs) under shared ITU-T E.212 mobile country codes (MCC).
+
+## History \*
+
+| Edition | Recommendation            | Approval   | Study Group | Unique ID          |
+|---------|---------------------------|------------|-------------|--------------------|
+| 1.0     | ITU-T E.212               | 1984-10-19 |             | 11.1002/1000/3197  |
+| 2.0     | ITU-T E.212               | 1988-11-25 |             | 11.1002/1000/440   |
+| 3.0     | ITU-T E.212               | 1998-11-13 | 2           | 11.1002/1000/4528  |
+| 3.1     | ITU-T E.212 (1998) Amd. 1 | 2003-05-02 | 2           | 11.1002/1000/6245  |
+| 4.0     | ITU-T E.212               | 2004-05-28 | 2           | 11.1002/1000/7186  |
+| 4.1     | ITU-T E.212 (2004) Amd. 1 | 2007-02-08 | 2           | 11.1002/1000/8849  |
+| 5.0     | ITU-T E.212               | 2008-05-15 | 2           | 11.1002/1000/9300  |
+| 5.1     | ITU-T E.212 (2008) Amd. 1 | 2008-09-23 | 2           | 11.1002/1000/9523  |
+| 5.3     | ITU-T E.212 (2008) Amd. 2 | 2010-11-18 | 2           | 11.1002/1000/9114  |
+| 5.4     | ITU-T E.212 (2008) Amd. 3 | 2011-06-10 | 2           | 11.1002/1000/11032 |
+| 6.0     | ITU-T E.212               | 2016-09-23 | 2           | 11.1002/1000/12831 |
+| 6.1     | ITU-T E.212 (2016) Amd. 1 | 2018-07-13 | 2           | 11.1002/1000/13868 |
+| 6.2     | ITU-T E.212 (2016) Amd. 2 | 2020-06-05 | 2           | 11.1002/1000/14179 |
+| 6.3     | ITU-T E.212 (2016) Amd. 3 | 2020-12-18 | 2           | 11.1002/1000/14315 |
+| 7.0     | ITU-T E.212               | 2024-06-28 | 2           | 11.1002/1000/15788 |
+
+## Keywords
+
+E.212, MNC, MCC.
+
+---
+
+\* To access the Recommendation, type the URL <https://handle.itu.int/> in the address field of your web browser, followed by the Recommendation's unique ID.
+
+## FOREWORD
+
+The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis.
+
+The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics.
+
+The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1.
+
+In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC.
+
+### NOTE
+
+In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some other obligatory language such as "must" and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party.
+
+## INTELLECTUAL PROPERTY RIGHTS
+
+ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process.
+
+As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents/software copyrights, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the appropriate ITU-T databases available via the ITU-T website at <http://www.itu.int/ITU-T/ipr/>.
+
+© ITU 2024
+
+All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU.
+
+## Table of Contents
+
+###### Page
+
+|         |                                                                                                                                                                                 |    |
+|---------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|----|
+| 1       | Scope .....                                                                                                                                                                     | 1  |
+| 2       | References.....                                                                                                                                                                 | 1  |
+| 3       | Definitions .....                                                                                                                                                               | 1  |
+| 4       | Abbreviations and acronyms.....                                                                                                                                                 | 2  |
+| 5       | Considerations .....                                                                                                                                                            | 2  |
+| 6       | IMSI structure, format and assignment procedures .....                                                                                                                          | 3  |
+| 6.1     | Structure and format of the IMSI.....                                                                                                                                           | 3  |
+| 6.2     | IMSI assignment procedures .....                                                                                                                                                | 3  |
+| Annex A | Criteria and procedures for the assignment and reclamation of shared ITU-T E.212 mobile country codes (MCC) for networks and their respective mobile network codes (MNCs) ..... | 4  |
+| A.1     | Introduction .....                                                                                                                                                              | 4  |
+| A.2     | Scope .....                                                                                                                                                                     | 4  |
+| A.3     | Principles for assignment .....                                                                                                                                                 | 4  |
+| A.4     | Criteria for assignment .....                                                                                                                                                   | 4  |
+| A.5     | Assignment .....                                                                                                                                                                | 5  |
+| A.6     | Voluntary return of unused MNCs .....                                                                                                                                           | 6  |
+| A.7     | Criteria for reclamation.....                                                                                                                                                   | 6  |
+| A.8     | Reclamation.....                                                                                                                                                                | 6  |
+| A.9     | Reconsideration process .....                                                                                                                                                   | 7  |
+| Annex B | Principles for the assignment of mobile network codes (MNCs) within geographic MCCs .....                                                                                       | 8  |
+| Annex C | Procedures for the assignment of an additional MCC to a country .....                                                                                                           | 10 |
+| Annex D | Use of mobile subscription identification number (MSIN).....                                                                                                                    | 11 |
+| Annex E | The use of an MCC+MNC in a country other than the country to which the MCC has been assigned by the Director of TSB .....                                                       | 12 |
+| E.1     | Introduction .....                                                                                                                                                              | 12 |
+| E.2     | Procedure to be followed for implementation of the extra-territorial use of an MCC+MNC .....                                                                                    | 12 |
+| E.3     | Voluntary return of an MNC.....                                                                                                                                                 | 13 |
+| E.4     | Criteria for cancellation of extra-territorial use .....                                                                                                                        | 13 |
+| E.5     | Cancellation procedures .....                                                                                                                                                   | 13 |
+| Annex F | Illustration of uses of ITU-T E.212 resources.....                                                                                                                              | 14 |
+| F.1     | Introduction .....                                                                                                                                                              | 14 |
+| F.2     | Mobile networks (PLMN).....                                                                                                                                                     | 14 |
+| F.3     | Fixed networks (PSTN).....                                                                                                                                                      | 14 |
+| F.4     | Satellite and non-terrestrial networks .....                                                                                                                                    | 14 |
+| F.5     | Services used globally .....                                                                                                                                                    | 14 |
+
+|                                                                                                                                                                                                                                       | Page |
+|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|------|
+| F.6 Networks .....                                                                                                                                                                                                                    | 15   |
+| Annex G Assignment of shared ITU-T E.212 mobile country codes (MCC) for trials .....                                                                                                                                                  | 16   |
+| G.1 Introduction .....                                                                                                                                                                                                                | 16   |
+| G.2 Scope .....                                                                                                                                                                                                                       | 16   |
+| G.3 General .....                                                                                                                                                                                                                     | 16   |
+| G.4 Criteria for the temporary assignment of a trial MCC+Trial-MNC .....                                                                                                                                                              | 16   |
+| G.5 Procedures for temporary assignment.....                                                                                                                                                                                          | 17   |
+| Annex H Criteria and procedures for the assignment and reclamation of shared ITU-T E.212 mobile country codes (MCC) for regional and other international organizations (ROIO)/standards development organization (SDO)-specified..... | 19   |
+| H.1 Introduction .....                                                                                                                                                                                                                | 19   |
+| H.2 Scope .....                                                                                                                                                                                                                       | 19   |
+| H.3 Principles for assignment .....                                                                                                                                                                                                   | 19   |
+| H.4 Criteria for assignment .....                                                                                                                                                                                                     | 19   |
+| H.5 Assignment.....                                                                                                                                                                                                                   | 21   |
+| H.6 Voluntary return of unused MNCs .....                                                                                                                                                                                             | 21   |
+| H.7 Criteria for reclamation.....                                                                                                                                                                                                     | 22   |
+| H.8 Reclamation.....                                                                                                                                                                                                                  | 22   |
+| H.9 Reconsideration process .....                                                                                                                                                                                                     | 22   |
+| Appendix I Form A: Notification of the use of an MCC/MNC extra-territorially.....                                                                                                                                                     | 24   |
+| Appendix II Form B: Notification of the cancellation of use of an MCC/MNC extra-territorially .....                                                                                                                                   | 25   |
+| Appendix III Shared ITU-T E.212 mobile country code (MCC) 999 for internal use within a private network .....                                                                                                                         | 26   |
+| III.1 Introduction .....                                                                                                                                                                                                              | 26   |
+| III.2 Principles.....                                                                                                                                                                                                                 | 26   |
+| Bibliography.....                                                                                                                                                                                                                     | 27   |
+
+# Recommendation ITU-T E.212
+
+# The international identification plan for public networks and subscriptions
+
+## 1 Scope
+
+This Recommendation describes a unique and unambiguous identification plan for subscriptions and the format of the international mobile subscription identity (IMSI). It establishes procedures for the assignment of fields of the IMSI in a manner that prevents duplication.
+
+## 2 References
+
+The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation.
+
+- [ITU-T E.101] Recommendation ITU-T E.101 (2009), *Definitions of terms used for identifiers (names, numbers, addresses and other identifiers) for public telecommunication services and networks in the E-series Recommendations.*
+- [ITU-T E.164] Recommendation ITU-T E.164 (2010), *The international public telecommunication numbering plan.*
+- [ITU-T E.164.1] Recommendation ITU-T E.164.1 (2008), *Criteria and procedures for the reservation, assignment and reclamation of E.164 country codes and associated identification codes (ICs).*
+- [ITU-T E.190] Recommendation ITU-T E.190 (1997), *Principles and responsibilities for the management, assignment and reclamation of E-series international numbering resources.*
+
+## 3 Definitions
+
+Whenever the term "country", "destination country" or "originating country" is used in this Recommendation, it identifies a specific country, a group of countries in an integrated numbering plan or a specific geographical area.
+
+The terms "operator" and "national numbering plan administrator" are defined in [ITU-T E.101]. This Recommendation defines the following terms:
+
+**3.1 home network:** The network responsible for the subscription identified by the elements within the IMSI.
+
+**3.2 international mobile subscription identity (IMSI):** The IMSI is a string of decimal digits, up to a maximum length of 15 digits, which identifies a unique subscription. The IMSI consists of three fields: the mobile country code (MCC), the mobile network code (MNC), and the mobile subscription identification number (MSIN).
+
+**3.3 mobile country code (MCC):** The MCC is the first field of the IMSI, is three digits in length and identifies a country. The Director of TSB may assign more than one MCC to a country. MCCs in the 90x range are non-geographic MCCs (country-agnostic) and are administered by the Director of TSB.
+
+**3.4 mobile network code (MNC):** The MNC is the second field of the IMSI, is two or three digits in length and is administered by the respective national NPA. MNCs under MCC ranges 90x are administered by the Director of TSB. The MNC, in combination with the MCC, provides sufficient information to identify the home network.
+
+**3.5 mobile subscription identification number (MSIN):** The MSIN is the third field of the IMSI, is up to 10 digits in length and is administered by the relevant MNC assignee to identify individual subscriptions.
+
+## **4 Abbreviations and acronyms**
+
+This Recommendation uses the following abbreviations and acronyms:
+
+|       |                                                   |
+|-------|---------------------------------------------------|
+| FN    | Future Network                                    |
+| GSM-R | Global System for Mobile communications – Railway |
+| IMSI  | International Mobile Subscription Identity        |
+| MCC   | Mobile Country Code                               |
+| MNC   | Mobile Network Code                               |
+| MSIN  | Mobile Subscription Identification Number         |
+| NGN   | Next Generation Network                           |
+| NPA   | Numbering Plan Administrator                      |
+| PLMN  | Public Land Mobile Network                        |
+| PSTN  | Public Switched Telephone Network                 |
+| ROIO  | Regional and Other International Organizations    |
+| SDO   | Standards Development Organization                |
+| SIM   | Subscriber Identity Module                        |
+| TIES  | Telecommunication Information Exchange Service    |
+| TSB   | Telecommunication Standardization Bureau          |
+| UICC  | Universal Integrated Circuit Card                 |
+| USIM  | Universal Subscriber Identity Module              |
+
+## **5 Considerations**
+
+The considerations that form the basis for this international identification plan for networks and subscriptions are as follows:
+
+- a) The assignment of E.212 resources is in conformance with the principles in [ITU-T E.190].
+- b) There may be more than one public network offering such services in a country.
+- c) The MNC consists of 2 or 3 digits and the length of the MNC is a national matter.
+- d) The number of digits of the MSINs is determined by the relevant MNC assignee in accordance with the national policy.
+- e) The IMSI shall not exceed 15 digits in length.
+- f) For 90x MCCs, the length of MNCs is determined by the Director of the Telecommunication Standardization Bureau (TSB) and the length of the MSINs is determined by the relevant MNC assignee in accordance with the relevant ITU-T Recommendations.
+
+- g) The IMSI assigned to a subscription under this identification plan should not be directly related to numbers assigned to that same subscription under "The international public telecommunications numbering plan" [ITU-T E.164].
+- h) The IMSI should, if necessary, enable:
+  - 1) determination of the home network;
+  - 2) identification of subscriptions, when information about a specific subscription is exchanged between networks;
+  - 3) identification of subscriptions for charging and billing purposes;
+  - 4) identification and management of subscription, e.g., for registering, authenticating, signalling, retrieving, providing, changing and updating of subscription data.
+- i) The IMSI is not intended to be used for dialling purposes. This list is not exhaustive.
+
+## 6 IMSI structure, format and assignment procedures
+
+### 6.1 Structure and format of the IMSI
+
+The IMSI structure and format are as shown in Figure 1.
+
+![Diagram showing the structure of the IMSI, composed of MCC (Mobile Country Code), MNC (Mobile Network Code), and MSIN (Mobile Subscription Identification Number).](7a0db9703b68b3d06cdaeefc084c0006_img.jpg)
+
+The diagram illustrates the structure of the IMSI. It is divided into three main components: MCC (Mobile Country Code), MNC (Mobile Network Code), and MSIN (Mobile Subscription Identification Number). The MCC is 3 digits long, the MNC is 2 to 3 digits long, and the MSIN is a maximum of 10 digits long. The total length of the IMSI is a maximum of 15 digits. The diagram shows the MCC, MNC, and MSIN as separate boxes, with arrows indicating their respective digit counts. Below the boxes, the labels 'Three digits', 'Two to three digits', and 'Maximum of ten digits' are present. A long arrow at the bottom indicates the total length of the IMSI as 'Maximum of fifteen digits'.
+
+|                           |                     |                       |
+|---------------------------|---------------------|-----------------------|
+| MCC                       | MNC                 | MSIN                  |
+| Three digits              | Two to three digits | Maximum of ten digits |
+| IMSI                      |                     |                       |
+| Maximum of fifteen digits |                     |                       |
+
+Diagram showing the structure of the IMSI, composed of MCC (Mobile Country Code), MNC (Mobile Network Code), and MSIN (Mobile Subscription Identification Number).
+
+MCC Mobile country code  
+ MNC Mobile network code  
+ MSIN Mobile subscription identification number  
+ IMSI International mobile subscription identity
+
+E.212(16)\_F01
+
+**Figure 1 – Structure and format of the IMSI**
+
+### 6.2 IMSI assignment procedures
+
+- 6.2.1 The Director of TSB assigns MCCs in accordance with Annexes A, C and H.
+- 6.2.2 MNCs associated with geographical MCCs are administered by the national NPA within each country in accordance with the principle in Annex B.
+- 6.2.3 MSINs are administered by the relevant MNC assignee in accordance with relevant national legal and regulatory environments or ITU-T Recommendations.
+- 6.2.4 In principle, only one IMSI should be assigned to each subscription, although multiple subscriptions may be associated with a SIM/USIM/UICC/embedded SIM card.
+
+## Annex A
+
+### Criteria and procedures for the assignment and reclamation of shared ITU-T E.212 mobile country codes (MCC) for networks and their respective mobile network codes (MNCs)
+
+(This annex forms an integral part of this Recommendation.)
+
+### A.1 Introduction
+
+The Director of TSB assigns and reclaims E.212 mobile country codes (MCCs) for countries and shared MCCs for networks according to this Recommendation. The Director of TSB is also responsible for the assignment and reclamation of mobile network codes (MNCs) for shared MCCs for networks. Mobile subscription identification numbers (MSINs) are administered by the MNC assignee.
+
+### A.2 Scope
+
+This annex describes the procedures and criteria to be utilized by the Director of TSB for the assignment and reclamation of mobile network codes (MNCs) associated with shared MCCs for networks.
+
+### A.3 Principles for assignment
+
+**A.3.1** In accordance with this Recommendation, the shared MCC resources assigned to networks shall consist of a 3-digit shared MCC for networks followed by a 2- or 3-digit MNC.
+
+**A.3.2** For a specific shared MCC for networks, the length of all MNCs within that MCC shall be the same.
+
+**A.3.3** Both the shared MCC(s) for networks, and the specific MNC(s) associated with a shared MCC for networks, will be assigned by the Director of TSB.
+
+**A.3.4** Subsequent shared MCCs for networks and/or MNCs that are part of shared MCCs for networks can be assigned by the Director of TSB in the event of exhaustion or another substantiated reason.
+
+### A.4 Criteria for assignment
+
+Throughout the following clauses, when using the term "applicant", it is assumed that the applicant is either an operator or is a group of operators. However, it should be noted that many national NPAs require that applicants correspond with ITU-TSB only via that national NPA. It should also be recognized that it may be a national NPA presenting an application on behalf of an applicant rather than the applicant making a direct approach to the Director of TSB.
+
+**A.4.1** The applicant must be a Member State or a Sector Member of the ITU or an Associate Member of the relevant ITU-T Study Group and must maintain its membership as long as it has reserved or is assigned the requested resource. If annual membership fees are not paid by the initial payment due date<sup>1</sup> the resources will be reclaimed.
+
+**A.4.2** The Director of TSB receives a written request from an applicant for assignment.
+
+**A.4.3** The applicant requesting the numbering resource must affirm that it has overall responsibility, or contract with the entity that has overall responsibility, for the management, operation and maintenance of the network that will utilize the requested resource.
+
+---
+
+<sup>1</sup> At the time of publication, the initial due date for payment of ITU membership fees is 31 March each year.
+
+**A.4.4** It is a national matter whether requests for codes require national NPA review or approval. The applicant shall certify that it has met all of its country's national, legal and/or regulatory requirements for submission of the application.
+
+**A.4.5** The applicant must also affirm that all national, regulatory, and legal requirements of the countries in which the applicant's network will operate and provide service are met at the time of network implementation.
+
+**A.4.6** If an applicant has been granted a shared E.164 country code resource per [ITU-T E.164.1] for the network cited in the application, it can be assumed that it has fulfilled the following criteria for assignment (see clauses A.4.1, A.4.3 and A.4.7). The applicant must certify that it continues to meet these criteria. However, if the application is for a network that is not associated with a shared E.164 country code resource, all of the criteria must be addressed.
+
+**A.4.7** The applicant must demonstrate that the international network infrastructure it intends to use will contain connecting physical nodes in two or more countries. In the case of satellite terminals, serving mobile terminals in two or more countries will satisfy this requirement.
+
+**A.4.8** The applicant is required to state the planned date of commercial implementation in at least two countries, or in geographical areas in two different countries.
+
+**A.4.9** The applicant will affirm that the requested resources will be used for offering public telecommunication services between two or more countries within a maximum of 1 year from the date of assignment.
+
+**A.4.10** The applicant must demonstrate that the use of a MNC under a shared MCC for networks is an appropriate, efficient and effective method to identify terminals or users of the network for routing, addressing and billing purposes. The applicant must attach substantiating documentation justifying this fact. The applicant will affirm that it complies with interworking requirements among public networks.
+
+**A.4.11** The applicant must demonstrate that other reasonable technical and operational alternatives (e.g., use of national resources) are not appropriate. The applicant must attach substantiating documentation justifying this fact.
+
+**A.4.12** The applicant may apply for a subsequent MNC under the following circumstances:
+
+- The current assignment is approaching exhaustion.
+- The applicant can demonstrate that the resource will be utilized by a distinct shared network. Such a request will be treated as a new application.
+- Other substantiated reasons with proper justification.
+
+**A.4.13** Additional assignments of MNCs will be based on confirmation that the existing resource is being used in an efficient manner (e.g., that the format and length of the numbering plan is appropriate). The applicant must provide substantiated information that the resource is approaching exhaustion. The terms and conditions of the original assignment must be met.
+
+**A.4.14** The applicant will annually certify that the resource which has been assigned to it continues to be in operation and will also reaffirm its prime contact details through the submission of a status notification to the Director of TSB.
+
+### **A.5 Assignment**
+
+**A.5.1** Requests for the assignment of a shared MCC+MNC to a network will be addressed in writing to the Director of TSB. The written request should be submitted on official company letterhead and signed by an appropriate company representative. The signature of the appropriate company representative affirms that, in the applicant's view, all the criteria are met. This written request shall include:
+
+- a) A planned code activation date in order to determine the relevant urgency of the request;
+- b) Sufficient information so that the request can be analysed to satisfy the criteria given in clause A.4 (e.g., provide evidence that criteria will be complied with by the activation date, planned network architecture and call flows);
+- c) Evidence of payment of any applicable fee.
+
+**A.5.2** In making decisions, the Director of TSB consults with the appropriate ITU-T Study Group, if necessary.
+
+**A.5.3** Provided the criteria in clause A.4 are met, an applicant's request for assignment of a MNC under a shared MCC for networks will be granted by the Director of TSB and, if necessary, with consultation of the relevant ITU-T Study Group.
+
+**A.5.4** Within a given shared MCC for networks, applicants will receive MNCs in sequential order.
+
+**A.5.5** After the assignment has been made, the Director of TSB will respond in writing to the applicant and include appropriate information for their ongoing responsibility as contained in this Recommendation and [ITU-T E.190]. In addition, the assignment will be published in the appropriate media (e.g., the ITU Website (TIES) and in the Operational Bulletin).
+
+**A.5.6** An assignment can be requested for non-commercial trials or testing purposes for a period of up to two years. The code subsequently assigned can be used only for non-commercial trial and testing purposes.
+
+### **A.6 Voluntary return of unused MNCs**
+
+**A.6.1** If an applicant or assignee determines that a MNC assigned to its network is no longer required, the Director of TSB shall be notified of that fact in writing.
+
+**A.6.2** The Director of TSB will respond in writing to the applicant acknowledging the return of the MNC.
+
+**A.6.3** The Director of TSB is to publish the date of the return of the MNC in the appropriate media (e.g., ITU website (TIES) and in the Operational Bulletin).
+
+**A.6.4** The returned MNC(s) should not be reassigned for a period of 2 years.
+
+**A.6.5** At the end of the ageing two-year period, the Director of TSB will return a code to spare status.
+
+### **A.7 Criteria for reclamation**
+
+**A.7.1** The assigned MNC is subject to reclamation if any of the following occurs:
+
+- the assigned MNC is not implemented;
+- the network no longer satisfies the assignment criteria;
+- the network is not operational between at least two countries;
+- the MNC is not in use for a period of 2 years; or
+- annual membership fees are not paid by the initial payment due date.
+
+### **A.8 Reclamation**
+
+**A.8.1** If a shared MCC+MNC for networks meets the reclamation criteria provided in clause A.7.1, the Director of TSB will notify the assignee in writing that the code is subject to reclamation.
+
+**A.8.2** At the time of reclamation of an assigned MNC code under a shared MCC for networks, the Director of TSB shall publish the date of MNC reclamation via the appropriate media (e.g., ITU website (TIES), and in the Operational Bulletin).
+
+**A.8.3** The returned MNCs should not be reassigned for a period of 2 years from the date of reclamation.
+
+**A.8.4** At the end of the two-year period, the Director of TSB will return a code to spare status.
+
+**A.8.5** A code is to be reclaimed if the applicant has not certified on an annual basis that the code is being used in accordance with the reservation or assignment request or has not also provided the applicant's prime contact details and an affirmation that the applicant is a Member State, a Sector Member or an Associate Member of the relevant ITU-T Study Group which has paid its membership fees by the initial payment due date.
+
+### **A.9 Reconsideration process**
+
+An applicant for a MNC associated with a shared MCC for networks who has been denied an assignment can request a reconsideration of the denial to the Director of TSB in the following manner. The reconsideration could include a presentation by the applicant to the relevant ITU-T Study Group.
+
+**A.9.1** In response to a letter of denial from the Director of TSB, the applicant can submit a supplement to its original application that responds to the reason(s) for denial contained in the letter. The applicant should submit its request for reconsideration, in writing, to the Director of TSB. In order to be considered by the Director of TSB, the response must include new or clarifying information. The submission should present the position of the applicant regarding the application and its denial, including its justification for this reconsideration. The applicant must attach to the submission a copy of the original application, the supplement to it, and the letter of denial from the Director of TSB. The applicant may also present the reconsideration at the Study Group meeting. If the reconsideration is to be presented to the relevant ITU-T Study Group, it should be submitted at least two months prior to the ITU-T Study Group meeting.
+
+**A.9.2** The Director of TSB will consult with the relevant ITU-T Study Group and/or its delegated representatives. The relevant ITU-T Study Group and/or its delegated representatives will then provide advice to the Director of TSB regarding the amended application and the contents of the submitted supplement to the original application.
+
+**A.9.3** If the Director of TSB determines that, based on the new information, the reservation or assignment should be made, the applicant will be so informed per the procedures in clause A.5.5.
+
+**A.9.4** If the Director of TSB determines that the application is still to be denied after proper consultation with the concerned Study Group, the applicant will be so informed and the reason(s) for the denial will be provided.
+
+## Annex B
+
+### Principles for the assignment of mobile network codes (MNCs) within geographical MCCs
+
+(This annex forms an integral part of this Recommendation.)
+
+- 1) MNCs under geographical MCCs are administered by the respective national numbering plan administrator who has responsibility for specifying criteria for assignment, conditions of use and procedures for reclamation at the national level in accordance with this Recommendation.
+- 2) The applicant must demonstrate a need for the resource and must further demonstrate that other reasonable technical and operational alternatives (e.g., use of already assigned MNCs, use of national allocated or assigned shared MNCs, use of embedded SIM) are not appropriate. The applicant must attach substantiating documentation justifying this fact.
+- 3) As required, applicants for MNCs must comply with applicable standards and national regulations relative to the provisioning of public telecommunication services. The applicant will affirm that it complies with interworking requirements among public networks.
+- 4) MNCs are to be assigned to permit the most effective and efficient use of a finite resource in order to defer, as long as practical, the need to request additional MCC resources. For networks and services to be provided in more than one country, excluding mobile roaming services, an applicant for an MNC under a geographical MCC should be encouraged to apply to the ITU for the assignment of an MNC under a shared MCC (Annex A) to avoid the need for multiple assignments of MNCs under different geographical MCCs.
+- 5) A country's national numbering plan administrator may assign one MNC within an MCC assigned to that country by the Director of TSB to the applicant if the applicant demonstrates compliance with the criteria established by the administrator including the respective right to apply for an MNC. The administrator may assign additional MNCs if the applicant meets the criteria for additional assignments established by the national numbering plan administrator, e.g., testing, national roaming, another mobile system.
+- 6) MNCs are to be assigned to applicants and used by assignees for public networks offering public telecommunication services. In addition, MNCs may be assigned to other applicants (e.g., for GSM-R networks) and these assignments are to be made according to procedure and criteria established by the national numbering plan administrator.
+- 7) The assignment of MNCs to small geographical areas within a country is not recommended because it is not an efficient or effective use of the MNC resource.
+- 8) MSINs are to be assigned by the MNC assignee to their subscribed users. A user may have multiple IMSIs.
+- 9) IMSIs are a public resource. The assignment of any portion of an IMSI (i.e., MNC, MSIN) does not imply ownership of the resource by either the entity to which it is assigned or by the national numbering plan administrator.
+- 10) Should an assignee transfer control of all or a portion of its business using its assigned MNC under an existing arrangement, then the use of the assigned MNC may be transferable by the national numbering plan administrator.
+- 11) The national numbering plan administrator should:
+  - a) Assign MNCs in a fair, timely and impartial manner to any applicant that meets the criteria for assignment.
+  - b) Assign MNCs on a first-come, first-served basis from the available pool of unassigned MNCs.
+
+- c) Make all assignments based on the procedures and criteria as detailed in the assignment guidelines/conventions/regulations/laws.
+  - d) Notify the Director of TSB of the assignment of an MNC within 90 days, using the MNC notification form available on the ITU website.
+- 12) MNC reclamation principles:
+- a) The national numbering plan administrator may reclaim the resource if any of the principles or criteria for assignment is no longer fulfilled.
+  - b) An MNC resource that is reclaimed may be available for assignment within a specified period of time. The MNC may be reassigned, if feasible, if a limited number of MSINs have been assigned by the former operator. Duplicate MSINs within a reassigned MNC should not be permitted.
+  - c) Notify the Director of TSB of the withdrawal of an MNC within 90 days, using the MNC notification form available on the ITU website.
+
+## Annex C
+
+### Procedures for the assignment of an additional MCC to a country
+
+(This annex forms an integral part of this Recommendation.)
+
+- 1) A national numbering plan administrator may request the assignment of an additional mobile country code (MCC) in writing to the Director of TSB.
+- 2) A national numbering plan administrator may apply for a subsequent MCC when an existing MCC is approaching exhaustion. Exhaustion is defined as having less than 20% of the MNC resource available within an MCC, and the administrator should notify the Director of TSB. When a country has less than 30% of the MNC resource available, the national numbering plan administrator is encouraged to provide information about its present usage and assignments of MNCs to the Director of TSB.
+- 3) The national numbering plan administrator must provide substantiated information that this resource is approaching exhaustion.
+- 4) An additional assignment will be based on confirmation that the existing resource is being used in an efficient and effective manner.
+- 5) The written request should be submitted and signed by the national numbering plan administrator. This written request should include a planned date of implementation so that the ITU Operational Bulletin can be updated accordingly.
+- 6) At the time of application, an Administration may also request the reservation of up to one additional MCC for future use. This reservation should be on an exception basis and the Administration should provide compelling evidence for the need for such a reservation. The evidence should demonstrate why the additional assigned MCC is not sufficient to address the emerging need for ITU-T E.212 resources.
+- 7) These procedures may be updated depending on the future needs and requirements of national numbering plan administrators, the telecommunications industry and the availability of unassigned ITU-T E.212 MCC resources.
+- 8) National numbering plan administrators can notify the Director of TSB of MNC assignments using the form published on <http://www.itu.int/ITU-T/inr/forms/mnc.html>.
+
+## Annex D
+
+### Use of mobile subscription identification number (MSIN)
+
+(This annex forms an integral part of this Recommendation.)
+
+As a general practice, the initial or leading digits of the MSIN may be used to provide for example:
+
+- operational efficiencies;
+- internal numbering planning;
+- regulatory compliance;
+- hardware and software accommodation;
+- sharing the MNC resource among providers;
+- identification of HLRs, HSSs, etc;
+- identification of geographical areas.
+
+## Annex E
+
+### The use of an MCC+MNC in a country other than the country to which the MCC has been assigned by the Director of TSB
+
+(This annex forms an integral part of this Recommendation.)
+
+### E.1 Introduction
+
+Extraterritorial use of an MCC+MNC is the term used to describe the situation where an MCC+MNC that has been assigned to an operator in one country, Country A, is used in another country, Country B, through a base station established in Country B. Extraterritorial use does not include situations where a subscriber in one country receives services from a base station in another country, nor does it address roaming issues.
+
+The extraterritorial use of an MCC+MNC:
+
+- should not negatively impact services being provided by any other operators,
+- is on an exceptional basis and is subject to this annex,
+- is not intended to include situations where a subscriber in one country receives service from a base station located in another country (e.g., cross-border coverage leakage), or roaming,
+- must comply with all national regulations of each of the Administrations.
+
+The operator using an MCC+MNC extra-territorially must provide unique and unambiguous information to its roaming partners in order to allow them to identify the location of their subscribers. The extraterritorial use of an MCC+MNC should be communicated to the international community by those Administrations which have permitted such usage.
+
+### E.2 Procedure to be followed for implementation of the extraterritorial use of an MCC+MNC
+
+In the event that an operator wishes to implement the extraterritorial use of an MCC+MNC, it will seek the approval of the Administrations of both Country A and Country B.
+
+The operator will apply to each of the Administrations, providing the information required by these Administrations. It is suggested that the Administrations should obtain from the operator the information they will need to complete Form A (see Appendix I), in addition to any other documentation required.
+
+The Administrations should confer together on the extraterritorial use of the MCC+MNC. On reaching a decision, they should notify the operator that applied for extraterritorial use of the MCC+MNC, and all other PLMNs operating in either or both of Country A and Country B, accordingly.
+
+In the event that both of the Administrations agree that an operator can use the MCC+MNC extra-territorially, then each of the Administrations will advise the Director of TSB of the following:
+
+- the MCC+MNC that is to be used extra-territorially;
+- the countries where an MCC+MNC is being used extra-territorially;
+- the name of the operator(s) that are using an MCC+MNC extra-territorially;
+- the MSIN range used by the operator in each country.
+
+It is expected that normal roaming practices, tariffing and other country identification mechanisms of Country B, will be followed.
+
+Each of the Administrations will notify the Director of TSB of the extraterritorial use of an MCC+MNC by completing Form A.
+
+The Director of TSB shall publish the extraterritorial use via the appropriate media (e.g., ITU website, Operational Bulletin).
+
+### **E.3 Voluntary return of an MNC**
+
+If an operator determines that the part of an MCC+MNC resource being used extraterritorially is no longer required, then the operator will notify the National Administration of the MCC (Country A) of that fact in writing.
+
+The National Administration of the MCC will respond in writing to the applicant acknowledging the return of that part of the MCC+MNC and, in turn, notify the Director of TSB and all PLMNs operating in either Country A or Country B, or in both.
+
+The Director of TSB is to publish the date of the return of the part of the MCC+MNC for extraterritorial use in the appropriate media (e.g., ITU website (TIES), and in the Operational Bulletin).
+
+### **E.4 Criteria for cancellation of extraterritorial use**
+
+The assigned part of the MCC+MNC is subject to cancellation by either the National Administration of Country A or of Country B if, for example, any of the following occurs:
+
+- The assigned part of the MCC+MNC is not implemented;
+- The network no longer satisfies the assignment criteria;
+- The network is not operational; or
+- The assigned part of the MCC+MNC is not in use for a period of two years.
+
+### **E.5 Cancellation procedures**
+
+The operator will cease to use that portion of the MCC+MNC for extraterritorial use upon the request of either Country A or Country B. If either country initiates the cancellation, then it should formally notify the other country of this request. Upon notification, the countries should collaborate to cancel the authorization that has been issued to the operator for the extraterritorial use.
+
+Upon agreement, both countries will notify the Director of TSB by completing Form B (see Appendix II). They should also notify all PLMNs operating in either Country A or Country B, or in both.
+
+The Director of TSB shall publish the date of cancellation of the extraterritorial use via the appropriate media (e.g., ITU website (TIES), and in the Operational Bulletin).
+
+## Annex F
+
+### Illustration of uses of ITU-T E.212 resources
+
+(This annex forms an integral part of this Recommendation.)
+
+### F.1 Introduction
+
+The purpose of this annex is to illustrate some of the uses of the identification resources described and defined in this Recommendation. The identification plan was originally devised for use by the national cellular radio systems known as public land mobile networks (PLMNs). The identification resources are essential to the operation of cellular radio systems. The identification resources are also essential for fixed and global networks (e.g., global satellite networks, maritime, aeronautical) to provide innovative services (e.g., nomadic service, messaging service, authentication, presence), above all in next-generation networks (NGNs) and for other future networks (FNs).
+
+Maintaining and extending the use of a unique and unambiguous international identification plan allows the identification of resources to be used within national networks, between networks in the same country and between networks in different countries to facilitate access to international communication services and their applications.
+
+### F.2 Mobile networks (PLMN)
+
+The use of the ITU-T E.212 identification resources and its associated component parts permit the identification at country, network and user levels. The resource identifies the subscription and billing relationships.
+
+### F.3 Fixed networks (PSTN)
+
+The use of the ITU-T E.212 identification resource in the fixed network facilitates:
+
+- aspects of personal mobility whereby a user may move between compatible terminals and retain its subscribed access to service;
+- the authentication and verification of a user request for service which may be used on the basis of manual entry or automated reading device;
+- fixed networks emulating applications of the cellular mobile networks such as SMS or TEXT messaging;
+- interaction between users of fixed and mobile networks.
+
+### F.4 Satellite and non-terrestrial networks
+
+The initial requirements were for global mobile-satellite systems, but these have been expanded to cover regional satellite systems and other non-terrestrial networks. An MCC (i.e., 901) is allocated and assignment of MNCs are made by the Director of TSB and this resource is shared on the basis of MNCs being assigned to successful applicants. For the international telephone service, this shared identification resource can be associated with the corresponding ITU-T E.164 Country Code plus Identification Code (CC + IC).
+
+### F.5 Services used globally
+
+The ITU-T E.212 identification resource may be used by services in more than one country by the network which has been assigned the International shared ITU-T E.212 resources in accordance with the assignment criteria. The applicant should affirm:
+
+- a) that the identification resource will be used to support global services that are based on well recognized and implemented international standards;
+- b) the relevant international standards on which the service is based;
+
+- c) a description of the proposed service;
+- d) acceptance that any infringement of the reservation and assignment criteria and directly related ITU-T Recommendations, by any third party which the applicant through a contract subsequently subassigns part of the assigned resource to, may result in the total assigned resource being reclaimed.
+
+### **F.6 Networks**
+
+Networks in this clause are defined in [ITU-T E.164]. The ITU-T E.212 identification resource may be used in support of the service offered by the applicant.
+
+## Annex G
+
+### Assignment of shared ITU-T E.212 mobile country codes (MCC) for trials
+
+(This annex forms an integral part of this Recommendation.)
+
+### G.1 Introduction
+
+ITU-T has determined that a shared ITU-T E.212 mobile country code (i.e., MCC 991) is allocated to enable the conduct of trials of new international telecommunication service. Furthermore, it has been determined that two-digit mobile network codes (MNC) for trials (trial-MNC) will be temporarily assigned to successful applicants for the duration of their specified trial activity. This annex defines the use and limitations of such a resource as well as the criteria and procedures for the temporary assignment and reclamation of trial-MNCs.
+
+### G.2 Scope
+
+This annex contains the criteria and procedures for an applicant to be temporarily assigned a two-digit MNC within the shared ITU-T E.212 MCC 991 for the purpose of conducting an international non-commercial trial. The purpose of the trial will be to determine the viability of a proposed new international telecommunication service.
+
+### G.3 General
+
+A trial is the temporary implementation of a proposed new international service implemented in more than one country for the purpose of determining its technical, operational and business viability.
+
+In a **non-commercial trial**, the service provided in the trial is accessible to a limited set of users, the purpose of the trial is not for commercial offerings, and there may be a charge to the users.
+
+**G.3.1** The format of the ITU-T E.212 resources to be assigned for the purpose of an international trial is:
+
+MCC Trial-MNC where:
+
+MCC = Shared ITU-T E.212 mobile country code 991.
+
+Trial-MNC = 2-digit trial mobile network code, in the format XX, where X = 0 to 9.
+
+**G.3.2** Mobile country code 991 has been allocated the mobile shared country code for this purpose. Successful resource applicants will be assigned a 2-digit trial-MNC following the shared MCC 991 for its use during the trial period.
+
+**G.3.3** The temporary resource assignment will be for a one-year period from the start date of the trial. Prior to the end of the one-year trial period, the applicant may request an extension in writing to ITU Telecommunication Standardization Bureau (TSB) and be automatically granted a one-year extension. At the end of the trial the MCC+Trial-MNC combination shall be reclaimed by ITU TSB for reassignment.
+
+**G.3.4** The ITU TSB may reclaim an assigned MCC+Trial-MNC, prior to completion of the trial, if it is determined that any of the assignment criteria in the following clause are not being adhered to by the resource assignee.
+
+### G.4 Criteria for the temporary assignment of a trial MCC+Trial-MNC
+
+Throughout clauses G.4.1 to G.5.7, when using the term "applicant", it is assumed that the applicant is either an operator or a group of operators. However, it should be noted that many national numbering plan administrators require that any such applicant correspond with the ITU TSB only via that national numbering plan administrator. It should be recognized that it may be a national
+
+numbering plan administrator presenting an application on behalf of an applicant rather than the applicant making a direct approach to the Director of TSB.
+
+**G.4.1** The applicant must be a Member State or a Sector Member of the ITU or an Associate Member of the relevant ITU-T Study Group and must maintain its membership as long as it has reserved or is assigned the requested resource. If annual membership fees are not paid by the initial payment due date the resources will be reclaimed.
+
+**G.4.2** The Director of TSB receives a written request from an applicant for assignment.
+
+**G.4.3** The applicant requesting the numbering resource must affirm that it has overall responsibility for the management, operation and maintenance of the network that will utilize the requested resource.
+
+**G.4.4** It is a national matter whether requests for codes require national numbering plan administrator review or approval. The applicant shall certify that it has met all of its country's national, legal and/or regulatory requirements for submission of the application.
+
+**G.4.5** The applicant must also affirm that all national, regulatory, and legal requirements of the countries in which the applicant's network will operate and provide service are met at the time of network implementation.
+
+**G.4.6** If an applicant has been granted a trial E.164 resource according to [ITU-T E.164.2] for the network cited in the application, it can be assumed that it has fulfilled the following criteria for assignment: G.4.1, G.4.3 and G.4.7. The applicant must certify that it continues to meet these criteria. However, if the application is for a network that is not associated with a shared E.164 country code resource, all of the criteria must be addressed.
+
+**G.4.7** The applicant must demonstrate that its international network infrastructure will contain connecting physical nodes in two or more countries. In the case of satellite terminals, serving mobile terminals in two or more countries will satisfy this requirement.
+
+**G.4.8** Assignment and use of a trial-MNC does not prejudge in any way a possible future assignment in accordance with the provisions of Annex A of this Recommendation (i.e., ITU-T E.212).
+
+**G.4.9** The MCC+ Trial-MNC will be used to test a proposed new international service.
+
+**G.4.10** The MCC+Trial-MNC will be assigned for a non-commercial international trial between two or more countries that do not belong to the same integrated numbering plan.
+
+**G.4.11** The applicant will discontinue the use of the MCC+Trial-MNC and will return it to TSB at the end of the temporary assignment period.
+
+**G.4.12** The applicant and the entities participating in the trial will not promote the trial-MNC per se but they may promote the service subject to the trial.
+
+**G.4.13** The applicant must provide a description of the service/capability to be tested during the trial. This information will be treated as proprietary by TSB.
+
+**G.4.14** The applicant must provide the proposed start date for the trial. The trial start date must be within six months of the application date.
+
+**G.4.15** The applicant shall identify all service providers to participate in the trial.
+
+### **G.5 Procedures for temporary assignment**
+
+**G.5.1** The resource applicant will submit a written application affirming that it conforms to each of the assignment criteria contained in clause G.4.
+
+**G.5.2** ITU TSB will review the application for criteria compliance and provide a written response to the applicant within 10 business days indicating the results of the application or the request for additional information.
+
+**G.5.3** If the resource is assigned, the written response will contain the specific resource assigned and a reiteration of the conditions under which it is assigned, including the specific reclamation date, in accordance with this Recommendation. The assigned resource will be the next available resource in sequence – no request for a specific trial-MNC will be accommodated.
+
+**G.5.4** If the resource is denied, a written explanation will be provided.
+
+**G.5.4.1** ITU TSB will afford the applicant an opportunity to submit a revised application that addresses the deficiencies contained in the denial correspondence.
+
+**G.5.4.2** If the applicant feels that the denial is unjustified, it may appeal the denial to the appropriate ITU-T Study Group (the study group that maintains this Recommendation) for consideration.
+
+**G.5.5** Prior to the end of the initial one-year trial period, the applicant may request, in writing to the ITU TSB, and be automatically granted a one-year extension of the assignment. The request need not contain a reason for the extension, but the extension must be for the same trial for which the temporary resource was originally assigned.
+
+**G.5.6** At the end of the trial period (either one or two years from initial assignment, depending on whether an extension was granted), the ITU TSB will reclaim the assigned resource and will inform the assignee in writing of the imminent reclamation two months in advance of the reclamation. No action is required by assignee other than the termination of the use of the resource.
+
+**G.5.7** A reclaimed MCC+Trial-MNC may be reassigned after a 12-month idle period. At the end of the idle period, the reclaimed MCC+ Trial-MNC will become the next resource in sequence for assignment. The reclaimed resource, or any other MCC+Trial-MNC, may not be assigned or reassigned to the previous assignee (or trial co-participants) for the continuing/additional trial of the same service for which it was previously assigned.
+
+## Annex H
+
+### **Criteria and procedures for the assignment and reclamation of shared ITU-T E.212 mobile country codes (MCC) for regional and other international organizations (ROIO)/standards development organization (SDO)-specified networks and their respective mobile network codes (MNCs)**
+
+(This annex forms an integral part of this Recommendation.)
+
+### **H.1 Introduction**
+
+The Director of TSB assigns and reclaims E.212 shared mobile country codes (MCCs) for regional and other international organizations (ROIO)/standard development organization (SDO)-specified networks for specific use cases according to this Recommendation. The Director of TSB is also responsible for the assignment and reclamation of mobile network codes (MNCs) for shared MCCs for ROIO/SDO-specified networks for specific use cases.
+
+### **H.2 Scope**
+
+This annex describes the procedures and criteria to be utilized by the Director of TSB for the assignment and reclamation of MNCs associated with shared MCCs for ROIO/SDO-specified networks for specific use cases.
+
+**H.2.1** For the purposes of this annex, a regional or other international organization (ROIO) is an organization already admitted to participate in the work of the ITU pursuant to No. 231 of the ITU Convention and that has not been exempted from payment of membership fees.
+
+**H.2.2** For the purposes of this annex, an SDO is an entity that is recognized or accredited by a Member State as a national standards organization and that has not been exempted from payment of membership fees.
+
+**H.2.3** For the purposes of this annex, an ROIO/SDO-specified network for specific use cases is a network that can be implemented for that use case on the basis of a technical standard or specification developed and approved by the ROIO or the SDO.
+
+### **H.3 Principles for assignment**
+
+**H.3.1** In accordance with this Recommendation, the shared MCC resources assigned to ROIO/SDO-specified networks for specific use cases shall consist of a 3-digit shared MCC for ROIO/SDO-specified networks for specific use cases followed by a 2- or 3-digit MNC.
+
+**H.3.2** For a specific shared MCC for ROIO/SDO-specified networks for specific use cases, the length of all MNCs within that MCC shall be the same.
+
+**H.3.3** Both the shared MCC(s) for ROIO/SDO-specified networks for specific use cases, and the specific MNC(s) associated with a shared MCC for ROIO/SDO-specified networks for specific use cases, will be assigned by the Director of TSB.
+
+**H.3.4** Subsequent shared MCCs for ROIO/SDO-specified networks for specific use cases and/or MNCs that are part of shared MCCs for ROIO/SDO-specified networks for specific use cases can be assigned by the Director of TSB in the event of exhaustion or another substantiated reason.
+
+### **H.4 Criteria for assignment**
+
+Throughout the following clauses, when using the term "applicant", it is assumed that the applicant is an ROIO or an SDO.
+
+**H.4.1** The applicant must be an ROIO or an SDO that is either a Sector Member or an Associate of the relevant ITU-T Study Group and it must maintain that status as long as it is assigned the requested
+
+resource. If annual membership fees are not paid by the initial payment due date, the resources will be reclaimed.
+
+**H.4.2** The Director of TSB receives a written request from an applicant for assignment. If the applicant is an ROIO that has not been exempted from payment of membership fee it must so state. If the application in an SDO, it must include a letter from an Administration certifying that it is an SDO.
+
+**H.4.3** If the requested resources will be used in networks that are based on technical standards or specifications developed by another ROIO/SDO, the applicant shall affirm and provide evidence that there exists mutual consent between the applicant and the other ROIO/SDO regarding the usage of the requested resources for the ROIO/SDO-specified networks.
+
+**H.4.4** The applicant requesting the numbering resource shall affirm and provide evidence regarding how and who will have overall responsibility for the management, operation, and maintenance of the network/networks that will utilize the requested resource for specific use cases. The applicant shall also affirm and provide evidence regarding the relationship between the applicant and the entity identified to have overall responsibility and how it will exercise control over the utilizing networks with respect to the use of the requested E.212 resource. The applicant shall provide substantiated justifying information to the effect that it has overall control of the requested resource.
+
+**H.4.5** The applicant shall also affirm that the application for resources is being made on behalf of all its members and shall provide substantiated information showing that the application is formally endorsed by its members, in accordance with its decision-making process.
+
+**H.4.6** The applicant shall provide substantiated information to demonstrate that the resource can be used by all its members.
+
+**H.4.7** It is a national matter whether requests for codes require national numbering plan administrator review or approval. The applicant shall affirm that it has met all its country's national, legal and/or regulatory requirements for submission of the application. If approval of the national numbering plan administrator is needed in its Member State, the applicant shall also provide evidence regarding the approval.
+
+**H.4.8** The applicant shall also affirm that all national, regulatory, and legal requirements of the countries in which the network/networks will operate and provide service are met at the time of network implementation.
+
+**H.4.9** The applicant shall demonstrate that the intended network infrastructure of its members will contain physical nodes in two or more countries. In the case of satellite terminals, serving mobile terminals in two or more countries will satisfy this requirement.
+
+**H.4.10** The applicant shall state the planned date of implementation by its members in at least two countries, or in geographical areas in two different countries.
+
+**H.4.11** The applicant shall affirm that the requested resources will be used by its members, who will use those numbers as specified by the ROIO/SDO in two or more countries within a maximum of one year from the date of assignment.
+
+**H.4.12** The applicant shall demonstrate that the use of an MNC under a shared MCC for ROIO/SDO-specified networks for specific use cases is an appropriate, efficient and effective use of requested E.212 resources. The applicant shall attach substantiated information justifying this fact.
+
+**H.4.13** The applicant shall affirm that it complies with interworking requirements among public networks, if applicable.
+
+**H.4.14** The applicant shall demonstrate that other reasonable technical and operational alternatives (e.g., use of shared or national resources) are not appropriate. The applicant shall attach substantiated information justifying this fact.
+
+**H.4.15** The applicant may apply for a subsequent MNC under the following circumstances; such requests will be treated as a new application:
+
+- the applicant can demonstrate that the resource will be utilized for a distinct use case;
+- other substantiated reasons with proper justification.
+
+**H.4.16** The applicant may apply for a subsequent assignment if the current assignment is approaching exhaustion. Such a request shall be made in writing to the Director of TSB. Subsequent assignments of MNCs will be based on confirmation that the existing resource is being used in an efficient manner (e.g., that the format and length of the numbering plan is appropriate and describes the reuse of resources). The applicant shall provide substantiated information that the resource is approaching exhaustion. The terms and conditions of the original assignment must be met.
+
+**H.4.17** The applicant shall annually affirm that the resource which has been assigned to it continues to be in operation and shall also reaffirm its prime contact details through the submission of a status notification to the Director of TSB.
+
+**H.4.18** For a possible reclamation of the requested E.212 resource, the applicant shall affirm how it is able to ensure that use of the reclaimed E.212 resource is stopped as soon as possible and no later than two years from the date of reclamation.
+
+### **H.5 Assignment**
+
+**H.5.1** Requests for the assignment of a shared MCC+MNC to an ROIO/SDO-specified for specific use cases network shall be addressed in writing to the Director of TSB. The written request should be submitted on official ROIO/SDO letterhead and signed by an appropriate ROIO/SDO representative. The signature of the appropriate company representative affirms that, in the applicant's view, all the criteria are met. This written request shall include:
+
+- a) A planned code activation date in order to determine the relevant urgency of the request;
+- b) Sufficient information so that the request can be analysed to satisfy the criteria given in clause H.4 (e.g., provide evidence that criteria will be complied with by the activation date, planned network architecture and call flows);
+- c) Evidence of payment of any applicable fee.
+
+**H.5.2** In making decisions, the Director of TSB consults with the appropriate ITU-T Study Group, if necessary.
+
+**H.5.3** Provided the criteria in clause H.4 are met, an applicant's request for assignment of a MNC under a shared MCC for networks will be granted by the Director of TSB and, if necessary, with consultation of the relevant ITU-T Study Group.
+
+**H.5.4** Within a given shared MCC for ROIO/SDO-specified networks for specific use cases, applicants will receive MNCs in sequential order.
+
+**H.5.5** After the assignment has been made, the Director of TSB will respond in writing to the applicant and include appropriate information for their ongoing responsibility as contained in this Recommendation and [ITU-T E.190]. In addition, the assignment will be published in the appropriate media (e.g., the ITU Website (TIES) and in the Operational Bulletin).
+
+**H.5.6** An assignment can be requested for non-commercial trials or testing purposes for a period of up to two years. The code subsequently assigned can be used only for non-commercial trial and testing purposes.
+
+### **H.6 Voluntary return of unused MNCs**
+
+**H.6.1** If an applicant or assignee determines that a MNC assigned to its use case is no longer required, the Director of TSB shall be notified of that fact in writing.
+
+**H.6.2** The Director of TSB will respond in writing to the applicant acknowledging the return of the MNC.
+
+**H.6.3** The Director of TSB is to publish the date of the return of the MNC in the appropriate media (e.g., ITU website (TIES) and in the Operational Bulletin).
+
+**H.6.4** The returned MNC(s) should not be reassigned for a period of two years.
+
+**H.6.5** At the end of the ageing two-year period, the Director of TSB will return a code to spare status.
+
+### **H.7 Criteria for reclamation**
+
+**H.7.1** The assigned MNC is subject to reclamation if any of the following occurs:
+
+- the assigned MNC is not implemented;
+- the ROIO/SDO-specified network for specific use cases no longer satisfies the assignment criteria;
+- the assigned resource is not operational at least in two countries;
+- the MNC is not in use for a period of two years; or
+- annual membership fees are not paid by the initial payment due date.
+
+### **H.8 Reclamation**
+
+**H.8.1** If a shared MCC+MNC for ROIO/SDO-specified networks for specific use cases meets the reclamation criteria provided in clause H.7.1, the Director of TSB will notify the assignee in writing that the code is subject to reclamation.
+
+**H.8.2** At the time of reclamation of an assigned MNC code under a shared MCC for ROIO/SDO-specified networks for specific use cases, the Director of TSB shall publish the date of MNC reclamation via the appropriate media (e.g., ITU website (TIES), and in the Operational Bulletin).
+
+**H.8.3** The returned MNCs should not be reassigned for a period of two years from the date of reclamation.
+
+**H.8.4** At the end of the two-year period, the Director of TSB will return a code to spare status.
+
+**H.8.5** A code is to be reclaimed if the applicant has not certified on an annual basis that the code is being used in accordance with the assignment request or has not also provided the applicant's prime contact details and an affirmation that the applicant is an ROIO or an SDO that is either a Sector Member or an Associate of the relevant ITU-T Study Group.
+
+### **H.9 Reconsideration process**
+
+An applicant for a MNC associated with a shared MCC for ROIO/SDO-specified networks for specific use cases who has been denied an assignment can request a reconsideration of the denial to the Director of TSB in the following manner. The reconsideration could include a presentation by the applicant to the relevant ITU-T Study Group.
+
+**H.9.1** In response to a letter of denial from the Director of TSB, the applicant can submit a supplement to its original application that responds to the reason(s) for denial contained in the letter. The applicant should submit its request for reconsideration, in writing, to the Director of TSB. In order to be considered by the Director of TSB, the response must include new or clarifying information. The submission should present the position of the applicant regarding the application and its denial, including its justification for this reconsideration. The applicant must attach to the submission a copy of the original application, the supplement to it and the letter of denial from the Director of TSB. The applicant may also present the reconsideration at the Study Group meeting. If the reconsideration is to be presented to the relevant ITU-T Study Group, it should be submitted at least two months prior to the ITU-T Study Group meeting.
+
+**H.9.2** The Director of TSB will consult with the relevant ITU-T Study Group. The relevant ITU-T Study Group will then provide advice to the Director of TSB regarding the amended application and the contents of the submitted supplement to the original application.
+
+**H.9.3** If the Director of TSB determines that, based on the new information, the reservation or assignment should be made, the applicant will be so informed as per the procedures in clause H.5.5.
+
+**H.9.4** If the Director of TSB determines that the application is still to be denied after proper consultation with the concerned Study Group, the applicant will be so informed and the reason(s) for the denial will be provided.
+
+## Appendix I
+
+### Form A: Notification of the use of an MCC/MNC extra-territorially
+
+(This appendix does not form an integral part of this Recommendation.)
+
+To be returned to the Director of TSB Fax No.: +41 22 730 5853 or E-mail: tsbtson@itu.int
+
+This form should be used by each of the Administrations to notify the Director of TSB that the Administration has agreed that an operator can use an MCC+MNC of Country A in Country B.
+
+**MCC/MNC:**
+
+**Administration Contact-Person Name:** \_\_\_\_\_
+
+**Address:**
+
+**Telephone:** \_\_\_\_\_ **Fax:** \_\_\_\_\_ **Email:** \_\_\_\_\_
+
+| MCC/MNC | Operator(s) name | Country B – Where the MCC/MNC is to be used extra-territorially | MSIN range to be used in Country A | MSIN range to be used in Country B |
+|---------|------------------|-----------------------------------------------------------------|------------------------------------|------------------------------------|
+|         |                  |                                                                 |                                    |                                    |
+|         |                  |                                                                 |                                    |                                    |
+
+## Appendix II
+
+### Form B: Notification of the cancellation of use of an MCC/MNC extra-territorially
+
+(This appendix does not form an integral part of this Recommendation.)
+
+To be returned to the Director of TSB Fax No.: +41 22 730 5853 or E-mail: tsbtson@itu.int
+
+This form should be used by each of the Administrations to notify the Director of TSB that the Administration has agreed that an operator can cancel the use of an MCC+MNC of Country A in Country B.
+
+**MCC/MNC:**
+
+**Administration Contact-Person Name:** \_\_\_\_\_
+
+**Address:**
+
+**Telephone:** \_\_\_\_\_ **Fax:** \_\_\_\_\_ **Email:** \_\_\_\_\_
+
+| MCC/MNC | Operator(s) name | Country B – Where the MCC/MNC is used extra-territorially | MSIN range used in Country A | MSIN range used in Country B |
+|---------|------------------|-----------------------------------------------------------|------------------------------|------------------------------|
+|         |                  |                                                           |                              |                              |
+|         |                  |                                                           |                              |                              |
+
+## Appendix III
+
+### Shared ITU-T E.212 mobile country code (MCC) 999 for internal use within a private network
+
+(This appendix does not form an integral part of this Recommendation.)
+
+### III.1 Introduction
+
+This appendix clarifies the principles associated with the shared ITU-T E.212 mobile country code (MCC) 999 for internal use within a private network.
+
+### III.2 Principles
+
+**III.2.1** The ITU-T E.212 MCC 999 is allocated for internal use within a private network.
+
+**III.2.2** Mobile network codes (MNCs) under this MCC are not subject to assignment and therefore may not be globally unique. No interaction with ITU is required for using a MNC value under this MCC for internal use within a private network.
+
+**III.2.3** Any MNC value under this MCC used in a network has significance only within that network. The MNCs under this MCC are not routable between networks. The MNCs under this MCC shall not be used for roaming.
+
+**III.2.4** For the purposes of testing and examples using this MCC, it is encouraged to use MNC value 99 or 999.
+
+**III.2.5** MNCs under this MCC cannot be used outside of the network for which they apply.
+
+**III.2.6** MNCs under this MCC may be 2- or 3-digit.
+
+## Bibliography
+
+- [b-ITU-T D.93] Recommendation ITU-T D.93 (2009), *Charging and accounting in the international land mobile telephone service (provided via cellular radio systems)*.
+- [b-ITU-T Q.1001] Recommendation ITU-T Q.1001 (1988), (Extract from the Blue Book), *General aspects of public land mobile networks*.
+
+
+
+
+
+## SERIES OF ITU-T RECOMMENDATIONS
+
+|                 |                                                                                                                                                           |
+|-----------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Series A        | Organization of the work of ITU-T                                                                                                                         |
+| Series D        | Tariff and accounting principles and international telecommunication/ICT economic and policy issues                                                       |
+| <b>Series E</b> | <b>Overall network operation, telephone service, service operation and human factors</b>                                                                  |
+| Series F        | Non-telephone telecommunication services                                                                                                                  |
+| Series G        | Transmission systems and media, digital systems and networks                                                                                              |
+| Series H        | Audiovisual and multimedia systems                                                                                                                        |
+| Series I        | Integrated services digital network                                                                                                                       |
+| Series J        | Cable networks and transmission of television, sound programme and other multimedia signals                                                               |
+| Series K        | Protection against interference                                                                                                                           |
+| Series L        | Environment and ICTs, climate change, e-waste, energy efficiency; construction, installation and protection of cables and other elements of outside plant |
+| Series M        | Telecommunication management, including TMN and network maintenance                                                                                       |
+| Series N        | Maintenance: international sound programme and television transmission circuits                                                                           |
+| Series O        | Specifications of measuring equipment                                                                                                                     |
+| Series P        | Telephone transmission quality, telephone installations, local line networks                                                                              |
+| Series Q        | Switching and signalling, and associated measurements and tests                                                                                           |
+| Series R        | Telegraph transmission                                                                                                                                    |
+| Series S        | Telegraph services terminal equipment                                                                                                                     |
+| Series T        | Terminals for telematic services                                                                                                                          |
+| Series U        | Telegraph switching                                                                                                                                       |
+| Series V        | Data communication over the telephone network                                                                                                             |
+| Series X        | Data networks, open system communications and security                                                                                                    |
+| Series Y        | Global information infrastructure, Internet protocol aspects, next-generation networks, Internet of Things and smart cities                               |
+| Series Z        | Languages and general software aspects for telecommunication systems                                                                                      |

marked/E/T-REC-E.260-198811-I_PDF-E/raw.md

@@ -0,0 +1,147 @@
+
+
+![ITU logo](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg)
+
+The logo of the International Telecommunication Union (ITU) features the letters 'ITU' in a bold, sans-serif font, superimposed on a stylized globe with intersecting lines.
+
+ITU logo
+
+INTERNATIONAL TELECOMMUNICATION UNION
+
+**ITU-T**
+
+**E.260**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+**TELEPHONE NETWORK AND ISDN**
+
+**OPERATION, NUMBERING, ROUTING  
+AND MOBILE SERVICE**
+
+---
+
+**BASIC TECHNICAL PROBLEMS  
+CONCERNING THE MEASUREMENT  
+AND RECORDING OF CALL DURATIONS**
+
+**ITU-T Recommendation E.260**
+
+(Extract from the *Blue Book*)
+
+---
+
+# NOTES
+
+1 ITU-T Recommendation E.260 was published in Fascicle II.2 of the *Blue Book*. This file is an extract from the *Blue Book*. While the presentation and layout of the text might be slightly different from the *Blue Book* version, the contents of the file are identical to the *Blue Book* version and copyright conditions remain unchanged (see below).
+
+2 In this Recommendation, the expression “Administration” is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+# BASIC TECHNICAL PROBLEMS CONCERNING THE MEASUREMENT AND RECORDING OF CALL DURATIONS
+
+## 1 Recording call duration
+
+1.1 Technically *call duration* is the interval that elapses between:
+
+- the moment when the clear condition is detected at the point where the recording of the call duration takes place, and
+- the moment when the clear condition (clear forward signal) is detected at the same point.
+
+It follows that the apparatus used to record call duration of automatic calls must be capable of detecting the two moments mentioned above and of measuring the interval between them.
+
+1.2 When an Administration using a simplified signalling system has recourse to recording holding times for the establishment of international accounts, it is necessary to have a conversion factor making it possible to obtain the call duration from the holding time. The determination of this conversion factor requires fairly close observation. The ratio of holding time to call duration may not be the same for all the circuits of a single group, so that a fairly large number of circuits must be observed in order to find a reliable conversion factor. Moreover, the holding time also depends on the availability of switching equipment in the incoming country, as well as the reaction of subscribers when they hear ringing tone, busy tone, etc.; the holding time for a given call duration may thus be extremely variable<sup>1)</sup>.
+
+## 2 Discrimination between automatic and semiautomatic calls
+
+Since different accounting procedures are used for automatic and semiautomatic calls, the recording apparatus must be capable of distinguishing between these two types of calls and must record the call duration of automatic calls only.
+
+Discrimination can be effected by one of the following methods:
+
+- a) by connecting the measuring apparatus to a point in the exchange through which only automatic traffic is routed;
+- b) by recording call durations only for calls containing the *discriminating* digit 0 used in automatic working (see the Recommendation Q.104 cited in [2]).
+
+Method b) may be particularly useful when both automatic and semiautomatic calls originate at exchanges within the national network and are routed to the outgoing international exchange over a common group of circuits.
+
+## 3 Omission of international transit traffic from the records of call duration
+
+All records of call duration will be taken in the outgoing country and will relate to calls originating in that country. It will therefore be necessary, in an international exchange which routes both terminal and international transit traffic, to exclude the call duration of international transit calls passing through the exchange.
+
+It will be difficult to discriminate between originated calls and transit calls on the outgoing international circuits and it may therefore be necessary to segregate this traffic within the exchange and connect the recording apparatus at a point in the exchange where transit traffic is not encountered.
+
+---
+
+1) In Recommendation D.150, § 4.1.4 [1] holding time is not recommended because of the wide variations between chargeable time and holding time in different relations and in different call types, which makes the use of holding time inappropriate for remunerating Administrations of countries of destination.
+
+## **4 Discrimination according to destination**
+
+4.1 The records of call durations obtained by the recording apparatus must be related to particular countries of destination and, if required, to the charging areas of the country of destination; the recording apparatus should therefore be capable of identifying the destination of a call and of associating the measured call duration with this destination.
+
+*Note* – For drawing up international accounts (apart from frontier relations) it is not necessary to know the origin of the call or the charging zone from which it comes. The differences in shares resulting from different outgoing charging zones in a given country are kept by that country.
+
+### **4.2 *Incoming country constituting a single charging zone***
+
+Where the recording apparatus is connected to a circuit group carrying only terminal traffic, no discrimination is required. Where, however, a circuit group carries traffic to more than one country, discrimination between these countries must be effected from an examination of the international code for the country and/or the type of seizing signal (terminal or transit) which is sent over the international circuits.
+
+### **4.3 *Incoming country consisting of several charging zones***
+
+If the accounting procedure agreed between two countries demands the production of separate records of call durations for calls made to each charging zone in an incoming country, the recording apparatus must be arranged to discriminate between the calls to the different charging zones according to the first one or first two digits of the called station's national (significant) number<sup>2)</sup> (see Recommendation E.163).
+
+### **4.4 *Special frontier arrangements***
+
+To take account of the special system of charging for frontier relations (reduced charges between neighbouring frontier zones), special steps will have to be taken to discriminate between automatic calls in frontier relations and other automatic calls. This discrimination will be made every time that frontier traffic is routed wholly or partly (overflow) by long-distance international circuits having devices for measuring call duration.
+
+This discrimination will in general necessitate:
+
+- a) further analysis of the national (significant) number of the called subscriber than the one which is quoted in Recommendation E.163, and
+- b) the determination of the origin of the call, since frontier charges depend on the distance between the outgoing and the incoming frontier zones.
+
+## **5 Discrimination according to route and destination**
+
+In general there will be little difficulty in determining the route taken by a call on leaving the outgoing international exchange. If the recording apparatus is connected to the international circuits, then of course the recordings obtained will be appropriate to the route in question. If, however, the recording apparatus is connected to a point in the exchange remote from the outgoing circuits and the call to a particular country has the choice of more than one route, then information in respect of the actual route taken by the call must be supplied to the recording apparatus.
+
+## **6 Distribution of traffic in an international exchange for the purpose of measuring call durations**
+
+By way of example, Figure 1/E.260 is given hereafter showing how traffic should be distributed in an international exchange so as to take account of the provisions above.
+
+---
+
+2) See the definition of the national (significant) number in Recommendation E.160.
+
+![Diagram of traffic distribution in an international exchange showing four groups of calls and their routing paths.](f9a14fbfecbd7d059226cc93677d721b_img.jpg)
+
+The diagram illustrates the traffic distribution in an international exchange, showing four groups of calls and their respective routing paths:
+
+- (i) Calls from international circuits:** These calls enter through a **Transit link circuit**. They are connected to **To transit registers** and also pass through a **Selector (route and destination)** to the **International circuit**.
+- (ii) Calls from local networks linked to the international exchange:** These calls enter through an **Outgoing link circuit**. They are connected to an **International outgoing register** and also pass through a **Selector (route and destination)** to the **International circuit**. This path also includes **Metering equipment**.
+- (iii) Calls from operators in the international exchange:** These calls enter through an **"Operators" outgoing link circuit**. They are connected to **To "operators" outgoing registers** and also pass through a **Selector (route and destination)** to the **International circuit**.
+- (iv) Calls from provincial exchanges:** These calls enter through a **Link circuit**. They are connected to **To registers for provincial calls** and also pass through a **Selector (route and destination)** to the **International circuit**.
+
+All four groups of calls converge on a common **Selector (route and destination)** which directs them to the **International circuit**. The diagram is labeled **CCITT - 47971**.
+
+Diagram of traffic distribution in an international exchange showing four groups of calls and their routing paths.
+
+FIGURE 1/E.260  
+**Diagram giving an example of traffic distribution in an international exchange**
+
+The traffic passing through the international exchange is divided into the following four groups, as shown on the figure:
+
+- i) international transit traffic;
+- ii) automatic traffic (originated locally);
+- iii) semiautomatic traffic (originated locally);
+- iv) combined automatic and semiautomatic traffic from provincial exchanges.
+
+These groups would employ independent groups of link circuits and registers. Only group ii) and possibly group iv) would be involved in measuring call duration.
+
+The following auxiliary equipment is envisaged:
+
+- a) for each link circuit in groups ii) and iv), a selecting device capable of dealing with every possible combination of route/country or *charging zone* destination;
+- b) for each link circuit in group iv), a device to take care of the discrimination between semiautomatic and automatic traffic;
+- c) for registers in groups ii) and iv), equipment for analyzing country codes and if necessary an appropriate number of digits of the national (significant) number of the called subscriber in order to discriminate between charging zones (see Recommendation E.163, § 1.2);
+- d) for registers in group iv), a device to recognize the discriminating digit 0 used for automatic working;
+- e) a means of recording the call duration for each combination of route/country or charging zone destination.
+
+# References
+
+- [1] CCITT Recommendation *New system for accounting in international telephony*, Rec. D.150, § 4.1.4.
+- [2] CCITT Recommendation *Language digit or discrimination digit*, Rec. Q.104, § 1.4.2.

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+
+
+![ITU logo](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg)
+
+The logo of the International Telecommunication Union (ITU) features a globe with a lightning bolt superimposed on it, and the letters 'ITU' in a bold, sans-serif font.
+
+ITU logo
+
+INTERNATIONAL TELECOMMUNICATION UNION
+
+**ITU-T**
+
+**E.300**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+**TELEPHONE NETWORK AND ISDN**
+
+**OPERATION, NUMBERING, ROUTING  
+AND MOBILE SERVICE**
+
+---
+
+**SPECIAL USES OF CIRCUITS NORMALLY  
+EMPLOYED FOR AUTOMATIC TELEPHONE  
+TRAFFIC**
+
+**ITU-T Recommendation E.300**
+
+(Extract from the *Blue Book*)
+
+---
+
+# NOTES
+
+1 ITU-T Recommendation E.300 was published in Fascicle II.2 of the *Blue Book*. This file is an extract from the *Blue Book*. While the presentation and layout of the text might be slightly different from the *Blue Book* version, the contents of the file are identical to the *Blue Book* version and copyright conditions remain unchanged (see below).
+
+2 In this Recommendation, the expression “Administration” is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+# **SPECIAL USES OF CIRCUITS NORMALLY EMPLOYED FOR AUTOMATIC TELEPHONE TRAFFIC**
+
+The CCITT
+
+*considering*
+
+- (a) that special services exist which occasionally require the provision of telephone circuits for uses such as:
+  - reserve circuits for VF telegraphy,
+  - circuits for phototelegraph transmissions,
+  - control circuits for programme transmissions,
+  - leased circuits (other than permanent full-time leases);
+- (b) that the international telephone service is becoming more and more automatic, and that only a few manual circuits will be kept to form a reserve network;
+- (c) that it is therefore necessary to provide automatic circuits for special uses other than telephony;
+- (d) that telephone circuits assigned for special uses must, when needed, be made available to the special services as rapidly as possible;
+- (e) that it must be guaranteed that, after the circuits have been used for a special purpose, they will be returned to the telephone service without delay;
+- (f) that the switching of circuits for special purposes should not disturb the operation of telephone service.
+
+*recommends*
+
+that the following provisions be observed:
+
+- 1 In an international telephone relation, the number of automatic circuits assigned for special purposes should be in reasonable proportion to the total number of circuits, so that their occupation will not hamper the flow of automatic telephone traffic.
+- 2 Circuits to be used for special purposes should be passed at the outgoing and incoming ends through transfer panels on which the wanted circuit is disconnected manually from the telephone equipment and connected to the terminal of the special service concerned.  
+Alternatively, circuits assigned for special uses should be fitted, in the telephone equipment, with a device for automatic switching to the transfer panel of the special service, the operation being commanded by the latter. (This method is preferable because with the first method a telephone call could be interrupted if proper care is not exercised.)
+- 3 The switching operations should take place under the control of the outgoing international maintenance centre (IMC). The IMC may delay or limit the provision of telephone circuits for other purposes, particularly when restrictions are imposed on the telephone traffic.
+- 4 The following arrangements should be followed when special connections are set up and cleared:
+  - a) The occupation of a telephone circuit for a special purpose should be marked on the transfer panel at the outgoing end; conversely, if such a circuit is in fact engaged, it must be marked busy in the telephone switching equipment.
+  - b) A circuit assigned to a special use may not be taken for the service in question if a telephone call is in progress. However, arrangements should be made to ensure that the circuit cannot be engaged by another telephone call when the call is over (*preliminary blocking*).
+  - c) The circuits in a group of telephone circuits that are reserved for special uses should be last-choice circuits, to reduce the risk of finding them busy when required.
+
+- d) When a circuit is free, the supervisor in charge of the transfer panel at the outgoing end takes the necessary steps to withdraw the circuit from the telephone service. The responsible supervisor at the incoming end is then asked to make the necessary operations if the telephone equipment is not disconnectable by remote control.
+- e) While awaiting notification from the incoming end of completion of transfer to the special service, the outgoing supervisor tests the connection before making it available for its new functions.
+- f) The same procedure is followed at the outgoing end when the circuit is restored to the telephone service. To prevent a subsequent telephone call from being ineffective, care must be taken to clear the special call at the incoming end first.
+
+5 Bookings of leased circuits or order lines for programme transmissions are arranged in advance and are not urgent. The delays required by the connection of two circuits in tandem when a connection is operated entirely in automatic transit give rise to no particular difficulties.
+
+6 Where telegraph systems are concerned, the primary requirement is rapid replacement of the faulty VF bearer circuit. In view of the delay which would occur in employing two separate links to form a reserve circuit, it appears that in relations in which automatic transit switching is the normal method of operation, a direct circuit should be retained.
+
+Such a direct circuit could be manual or automatic. An automatic circuit would normally be used to carry the telephone traffic. It should be noted that this will then be used as a first-choice route and will thus carry the heaviest load. The risk of finding it busy, when needed, will therefore be at its maximum.
+
+In such circumstances, preliminary blocking of the wanted circuit should be effected (see § 4b) above). As long as the equipment is unable to perform this operation it will be preferable to keep one manual direct circuit.
+
+7 The delay in establishing phototelegraph calls via an international phototelegraph position transit centre (transit IPP) is not so critical. In this case, application of Recommendation E.320 will speed up the placing of two circuits end to end at the transit centre to establish the connection, and it will not be necessary to keep direct circuits in relations where automatic switching is the method normally used for telephone calls in transit.
+
+8 The same circuit should not be assigned to more than one special service, so that the various transfer panels for such services may be placed separate from one another should the terminal country so wish.

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+
+
+![ITU logo](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg)
+
+The logo of the International Telecommunication Union (ITU) features a globe with a lightning bolt superimposed on it, and the letters 'ITU' written across the center.
+
+ITU logo
+
+INTERNATIONAL TELECOMMUNICATION UNION
+
+**ITU-T**
+
+**E.360.5**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+(05/2002)
+
+SERIES E: OVERALL NETWORK OPERATION,  
+TELEPHONE SERVICE, SERVICE OPERATION AND  
+HUMAN FACTORS
+
+International routing plan
+
+---
+
+**QoS routing and related traffic engineering  
+methods – Transport routing methods**
+
+ITU-T Recommendation E.360.5
+
+---
+
+# ITU-T E-SERIES RECOMMENDATIONS
+
+# OVERALL NETWORK OPERATION, TELEPHONE SERVICE, SERVICE OPERATION AND HUMAN FACTORS
+
+|                                                                                                          |                    |
+|----------------------------------------------------------------------------------------------------------|--------------------|
+| <b>INTERNATIONAL OPERATION</b>                                                                           |                    |
+| Definitions                                                                                              | E.100–E.103        |
+| General provisions concerning Administrations                                                            | E.104–E.119        |
+| General provisions concerning users                                                                      | E.120–E.139        |
+| Operation of international telephone services                                                            | E.140–E.159        |
+| Numbering plan of the international telephone service                                                    | E.160–E.169        |
+| International routing plan                                                                               | E.170–E.179        |
+| Tones in national signalling systems                                                                     | E.180–E.189        |
+| Numbering plan of the international telephone service                                                    | E.190–E.199        |
+| Maritime mobile service and public land mobile service                                                   | E.200–E.229        |
+| <b>OPERATIONAL PROVISIONS RELATING TO CHARGING AND ACCOUNTING IN THE INTERNATIONAL TELEPHONE SERVICE</b> |                    |
+| Charging in the international telephone service                                                          | E.230–E.249        |
+| Measuring and recording call durations for accounting purposes                                           | E.260–E.269        |
+| <b>UTILIZATION OF THE INTERNATIONAL TELEPHONE NETWORK FOR NON-TELEPHONY APPLICATIONS</b>                 |                    |
+| General                                                                                                  | E.300–E.319        |
+| Phototelegraphy                                                                                          | E.320–E.329        |
+| ISDN PROVISIONS CONCERNING USERS                                                                         | E.330–E.349        |
+| <b>INTERNATIONAL ROUTING PLAN</b>                                                                        | <b>E.350–E.399</b> |
+| <b>NETWORK MANAGEMENT</b>                                                                                |                    |
+| International service statistics                                                                         | E.400–E.409        |
+| International network management                                                                         | E.410–E.419        |
+| Checking the quality of the international telephone service                                              | E.420–E.489        |
+| <b>TRAFFIC ENGINEERING</b>                                                                               |                    |
+| Measurement and recording of traffic                                                                     | E.490–E.505        |
+| Forecasting of traffic                                                                                   | E.506–E.509        |
+| Determination of the number of circuits in manual operation                                              | E.510–E.519        |
+| Determination of the number of circuits in automatic and semi-automatic operation                        | E.520–E.539        |
+| Grade of service                                                                                         | E.540–E.599        |
+| Definitions                                                                                              | E.600–E.649        |
+| Traffic engineering for IP-networks                                                                      | E.650–E.699        |
+| ISDN traffic engineering                                                                                 | E.700–E.749        |
+| Mobile network traffic engineering                                                                       | E.750–E.799        |
+| <b>QUALITY OF TELECOMMUNICATION SERVICES: CONCEPTS, MODELS, OBJECTIVES AND DEPENDABILITY PLANNING</b>    |                    |
+| Terms and definitions related to the quality of telecommunication services                               | E.800–E.809        |
+| Models for telecommunication services                                                                    | E.810–E.844        |
+| Objectives for quality of service and related concepts of telecommunication services                     | E.845–E.859        |
+| Use of quality of service objectives for planning of telecommunication networks                          | E.860–E.879        |
+| Field data collection and evaluation on the performance of equipment, networks and services              | E.880–E.899        |
+
+For further details, please refer to the list of ITU-T Recommendations.
+
+## **QoS routing and related traffic engineering methods –Transport routing methods**
+
+## **Summary**
+
+The E.360.x series of Recommendations describes, analyzes, and recommends methods which control a network's response to traffic demands and other stimuli, such as link failures or node failures. The functions discussed, and recommendations made, related to traffic engineering (TE), are consistent with the definition given in the Framework document of the Traffic Engineering Working Group (TEWG) within the Internet Engineering Task Force (IETF):
+
+Internet Traffic Engineering is concerned with the performance optimization of operational networks. It encompasses the measurement, modelling, characterization, and control of Internet traffic, and the application of techniques to achieve specific performance objectives, including the reliable and expeditious movement of traffic through the network, the efficient utilization of network resources, and the planning of network capacity.
+
+The methods addressed in the E.360.x series include call and connection routing, QoS resource management, routing table management, dynamic transport routing, capacity management, and operational requirements. Some of the methods proposed herein are also addressed in, or are closely related to, those proposed in ITU-T Recs E.170 to E.179 and E.350 to E.353 for routing, E.410 to E.419 for network management and E.490 to E.780 for other traffic engineering issues.
+
+The recommended methods are meant to apply to IP-based, ATM-based, and TDM-based networks, as well as the interworking between these network technologies. Essentially, all of the methods recommended are already widely applied in operational networks worldwide, particularly in PSTN networks employing TDM-based technology. However, these methods are shown to be extensible to packet-based technologies, that is, to IP-based and ATM-based technologies, and it is important that networks which evolve to employ these packet technologies have a sound foundation of methods to apply. Hence, it is the intent that the methods recommended in this series of Recommendations be used as a basis for requirements for specific methods, and, as needed, for protocol development in IP-based, ATM-based, and TDM-based networks to implement the methods.
+
+The methods encompassed in this Recommendation include traffic management through control of routing functions, which include QoS resource management. Results of analysis models are presented which illustrate the tradeoffs between various approaches. Based on the results of these studies as well as established practice and experience, methods are recommended for consideration in network evolution to IP-based, ATM-based, and/or TDM-based technologies.
+
+###### **Source**
+
+ITU-T Recommendation E.360.5 was prepared by ITU-T Study Group 2 (2001-2004) and approved under the WTSA Resolution 1 procedure on 16 May 2002.
+
+# FOREWORD
+
+The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis.
+
+The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics.
+
+The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1.
+
+In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC.
+
+## NOTE
+
+In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+## INTELLECTUAL PROPERTY RIGHTS
+
+ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process.
+
+As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database.
+
+© ITU 2003
+
+All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU.
+
+## CONTENTS
+
+###### Page
+
+|                                                          |                                                 |    |
+|----------------------------------------------------------|-------------------------------------------------|----|
+| 1                                                        | Scope .....                                     | 1  |
+| 2                                                        | References.....                                 | 1  |
+| 3                                                        | Definitions .....                               | 2  |
+| 4                                                        | Abbreviations.....                              | 2  |
+| 5                                                        | Dynamic transport routing principles .....      | 2  |
+| 6                                                        | Dynamic transport routing examples.....         | 6  |
+| 7                                                        | Reliable transport network design .....         | 11 |
+| 7.1                                                      | Transport link design models .....              | 13 |
+| 7.2                                                      | Node design models .....                        | 14 |
+| 8                                                        | Conclusions/recommendations .....               | 15 |
+| Annex A – Modelling of traffic engineering methods ..... |                                                 | 16 |
+| A.1                                                      | Dynamic transport routing capacity design.....  | 16 |
+| A.2                                                      | Performance for network failures.....           | 17 |
+| A.3                                                      | Performance for general traffic overloads ..... | 19 |
+| A.4                                                      | Performance for unexpected overloads .....      | 19 |
+| A.5                                                      | Performance for peak-day traffic loads .....    | 20 |
+
+# Introduction
+
+This Recommendation describes and analyzes transport network architectures in light of evolving technology for integrated broadband networks. Dynamic transport routing offers advantages of simplicity of design and robustness to load variations and network failures. Dynamic transport routing can combine with dynamic traffic routing to shift transport bandwidth among node pairs and services through use of flexible transport switching technology. Dynamic transport routing can provide automatic link provisioning, diverse link routing, and rapid link restoration for improved transport capacity utilization and performance under stress.
+
+We present reliable transport routing models to achieve reliable network design, so as to provide service for predefined restoration objectives for any transport link or node failure in the network and continue to provide connections to customers with essentially no perceived interruption of service. We show that robust routing techniques such as dynamic traffic routing, multiple ingress/egress routing, and logical link diversity routing improve response to node or transport failures.
+
+Cross-connect devices, such as optical cross-connects (OXCs), are able to node transport channels, for example OC48 channels, onto different higher-capacity transport links such as an individual WDM channel on a fiberoptic cable. Transport paths can be rearranged at high speed using OXCs, typically within tens of milliseconds switching times. These OXCs can reconfigure logical transport capacity on demand, such as for peak day traffic, weekly redesign of link capacity, or emergency restoration of capacity under node or transport failure. Rearrangement of logical link capacity involves reallocating both transport bandwidth and node terminations to different links. OXC technology is amenable to centralized traffic management.
+
+There is recent work in extending MPLS control capabilities to the setup of layer 2 logical links through OXCs, this effort dubbed multiprotocol lambda switching, after the switching of wavelengths in dense wavelength division multiplexing (DWDM) technology [ARDC99].
+
+## **QoS routing and related traffic engineering methods –Transport routing methods**
+
+# **1 Scope**
+
+The E.360.x series of Recommendations describes, analyzes, and recommends methods which control a network's response to traffic demands and other stimuli, such as link failures or node failures. The functions discussed, and recommendations made, related to traffic engineering (TE) are consistent with the definitions given in the Framework document of the Traffic Engineering Working Group (TEWG) within the Internet Engineering Task Force (IETF):
+
+Internet Traffic Engineering is concerned with the performance optimization of operational networks. It encompasses the measurement, modelling, characterization, and control of Internet traffic, and the application of techniques to achieve specific performance objectives, including the reliable and expeditious movement of traffic through the network, the efficient utilization of network resources, and the planning of network capacity.
+
+The methods addressed in the E.360.x series include call and connection routing, QoS resource management, routing table management, dynamic transport routing, capacity management, and operational requirements. Some of the methods proposed herein are also addressed in, or are closely related to, those proposed in ITU-T Recs E.170 to E.179 and E.350 to E.353 for routing, E.410 to E.419 for network management and E.490 to E.780 for other traffic engineering issues.
+
+The recommended methods are meant to apply to IP-based, ATM-based, and TDM-based networks, as well as the interworking between these network technologies. Essentially all of the methods recommended are already widely applied in operational networks worldwide, particularly in PSTN networks employing TDM-based technology. However, these methods are shown to be extensible to packet-based technologies, that is, to IP-based and ATM-based technologies, and it is important that networks which evolve to employ these packet technologies have a sound foundation of methods to apply. Hence, it is the intent that the methods recommended in this series of Recommendations be used as a basis for requirements for specific methods, and, as needed, for protocol development in IP-based, ATM-based, and TDM-based networks to implement the methods.
+
+Hence the methods encompassed in this series of Recommendations include:
+
+- traffic management through control of routing functions, which include call routing (number/name translation to routing address), connection routing, QoS resource management, routing table management, and dynamic transport routing.
+- capacity management through control of network design, including routing design.
+- operational requirements for traffic management and capacity management, including forecasting, performance monitoring, and short-term network adjustment.
+
+Results of analysis models are presented which illustrate the tradeoffs between various approaches. Based on the results of these studies as well as established practice and experience, TE methods are recommended for consideration in network evolution to IP-based, ATM-based, and/or TDM-based technologies.
+
+# **2 References**
+
+See clause 2 of ITU-T Rec. E.360.1.
+
+# 3 Definitions
+
+See clause 3 of ITU-T Rec. E.360.1.
+
+# 4 Abbreviations
+
+See clause 4 of ITU-T Rec. E.360.1.
+
+# 5 Dynamic transport routing principles
+
+An important element of network architecture is the relationship between the transport network and the traffic network. An illustration of a transport network is shown in Figures 1 and 2 illustrates the mapping of layer-2 logical links in the traffic network onto the layer-1 physical transport network of Figure 1. Some logical links overlay two or more fiber-backbone links. For example, in Figure 1, logical link AD traverses fiber-backbone links AB, BC, and CD.
+
+![Figure 1/E.360.5 – Transport network model. A map of the United States showing a network of nodes (black squares) and links. Solid lines represent fiber backbone links (layer 1), and dashed lines represent logical links (layer 2). Nodes are labeled A, B, C, D, E, and F. A logical link AD is shown as a dashed line connecting node A to node D, passing through nodes B and C. The map is labeled E.360.5_F1.](5860ad6bd2a2dd8d1ab12864b8f90f37_img.jpg)
+
+- Node (traffic switch and transport switch)
+- Fibre backbone links (layer 1)
+- - ■— Logical link (layer 2)
+
+Figure 1/E.360.5 – Transport network model. A map of the United States showing a network of nodes (black squares) and links. Solid lines represent fiber backbone links (layer 1), and dashed lines represent logical links (layer 2). Nodes are labeled A, B, C, D, E, and F. A logical link AD is shown as a dashed line connecting node A to node D, passing through nodes B and C. The map is labeled E.360.5\_F1.
+
+**Figure 1/E.360.5 – Transport network model**
+
+Figure 2 further illustrates the difference between the physical transport network (layer 1) and the logical transport network (layer 2). Logical links are individual logical connections between network nodes, which make up the logical link connections and are routed on the physical transport network. Logical links can be provisioned at given rates, such as T1, OC3, OC12, OC48, OC192, etc., and is dependent on the level of traffic demand between nodes.
+
+![Figure 2/E.360.5 – Logical (layer 2) and physical (layer 1) transport networks. The diagram is split into two views. The left view, 'Logical (layer 2) transport network view', shows four nodes (A, B, C, D) in a diamond shape. Node A is connected to B and C. Node B is connected to D. Node C is connected to D. A 'Traffic router' is connected to node B, and a 'Logical link' is shown between node B and node D. The right view, 'Physical (layer 1) transport network view', shows the same four nodes. Node A is connected to node B by a single line. Node B is connected to node D by a single line. Node C is connected to node D by a single line. Node A is connected to node C by a bundle of lines. Node B is connected to node C by a bundle of lines. Node A is connected to node D by a bundle of lines. Node B is connected to node D by a bundle of lines. Node C is connected to node D by a bundle of lines. An 'OXC transport switch' is connected to node B, and a 'Fibre link' is shown between node B and node D. The diagram is labeled E.360.5_F2.](731f533b0599c8e42a063f06e4332045_img.jpg)
+
+Figure 2/E.360.5 – Logical (layer 2) and physical (layer 1) transport networks. The diagram is split into two views. The left view, 'Logical (layer 2) transport network view', shows four nodes (A, B, C, D) in a diamond shape. Node A is connected to B and C. Node B is connected to D. Node C is connected to D. A 'Traffic router' is connected to node B, and a 'Logical link' is shown between node B and node D. The right view, 'Physical (layer 1) transport network view', shows the same four nodes. Node A is connected to node B by a single line. Node B is connected to node D by a single line. Node C is connected to node D by a single line. Node A is connected to node C by a bundle of lines. Node B is connected to node C by a bundle of lines. Node A is connected to node D by a bundle of lines. Node B is connected to node D by a bundle of lines. Node C is connected to node D by a bundle of lines. An 'OXC transport switch' is connected to node B, and a 'Fibre link' is shown between node B and node D. The diagram is labeled E.360.5\_F2.
+
+**Figure 2/E.360.5 – Logical (layer 2) and physical (layer 1) transport networks**
+
+Figure 2 indicates that a direct logical link is obtained by cross-connecting through a transport switching location. Thus, the traffic network is a logical network overlaid on a sparse physical one. A cross-connect device is traversed at each network node on a given logical link path over layer-1 physical transport links, as illustrated in Figure 2. This is particularly promising when such a device has low cost.
+
+It is clear from Figures 1 and 2 that in a highly interconnected traffic network, or logical transport network, many node pairs may have a "direct" logical link connection where none exists in the physical transport network. In this case, a direct logical link is obtained by cross-connecting through a transport switching location, such as an OXC. This is distinct from the traffic routing situation in which a bearer connection is actually switched at an intermediate location. This distinction between cross-connecting and switching is a bit subtle, but it is fundamental to traffic routing of calls and transport routing of logical links. Referring to Figure 2, we illustrate one of the logical inconsistencies we encounter when we design the traffic network to be essentially separate from the transport network. On the alternative traffic path from node B to node D through A, the physical path is, in fact, up and back from B to A (a phenomenon known as "backhauling") and then across from B to D. The sharing of capacity by various traffic loads in this way actually increases the efficiency of the network because the backhauled capacity to and from B and A is only used when no direct A-to-B or A-to-D traffic wants to use it. It is conceivable that under certain conditions, capacity could be put to more efficient use, and this is studied in this Recommendation.
+
+Hence, a logical link connection is obtained by cross-connecting through transport switching devices, such as OXCs, and this is distinct from per-flow routing, which switches a call on the logical links at each node in the call path. In this way, the logical transport network is overlaid on a sparser physical transport network. In ITU-T Rec. E.360.2 we discussed a wide variety of dynamic traffic routing methods. Dynamic transport routing methods incorporate dynamic path selection which seeks out and uses idle network capacity by using frequent, perhaps call-by-call, traffic and transport routing table update decisions. The trend in both traffic and transport routing architecture is toward greater flexibility in resource allocation, which includes transport and switching resource allocation. A fixed transport routing architecture may have dynamic traffic routing but fixed transport routing of logical link capacity. In a dynamic transport routing architecture, however, the logical link capacities can be rapidly rearranged that is, they are not fixed.
+
+With dynamic transport routing, the logical transport bandwidth is shifted rapidly at layer 2 among node pairs and services through the use of dynamic cross-connect devices. In this case, the layer-1 physical fiber-link bandwidth is allocated among the layer-2 logical links. Bandwidth allocation at layer 3 also creates the equivalent of direct links, and we refer to these links as traffic trunks, which in turn comprise virtual networks (VNETs) as described in ITU-T Rec. E.360.3. Traffic trunks can be implemented, for example, by using MPLS label switched paths (LSPs). Bandwidth is allocated to traffic trunks in accordance with traffic demands, and normally not all logical link bandwidth is assigned; thus, there is a pool of unassigned bandwidth. In cases of traffic overload for a given node pair, the node first sets up calls on the traffic trunk that connects the node pair. If that is not possible, the node then sets up calls on the available pool of bandwidth. If there is available bandwidth, then the bandwidth is allocated to the traffic trunk and used to set up the call. If bandwidth is not available, then the layer-2 logical link bandwidth might be dynamically increased by the bandwidth broker, and then allocated to the traffic trunk and finally, the call. In a similar manner, in the event that bandwidth is underutilized in a traffic trunk, excess bandwidth is released to the available pool of bandwidth and then becomes available for assignment to other node pairs. If logical link bandwidth is sufficiently underutilized, the bandwidth might be returned to the available pool of layer-1 fiber-link bandwidth. The bandwidth broker reassigns network resources on a dynamic basis, through analysis of traffic data collected from the individual nodes.
+
+In the dynamic transport architecture, we allow logical link between the various nodes to be rearranged rapidly, such as by hour of the day, or perhaps in real time. Dynamic transport routing capability enables rearrangement of the logical link capacities on demand. This capability appears
+
+most desirable for use in relatively slow rearrangement of capacity, such as for busy-hour traffic, weekend traffic, peak-day traffic, weekly redesign of logical link capacities, or for emergency restoration of capacity under node or transport failure. At various times, the demands for node and transport capacity by the various node pairs and services that ride on the same optical fibers will differ. In this network, if a given demand for logical link capacity between a certain node pair decreases and a second goes up, we allow the logical link capacity to be reassigned to the second node pair. The ability to rearrange logical link capacity dynamically and automatically results in cost savings. Large segments of bandwidth can be provided on fiber routes, and then the transport capacity can be allocated at will with the rearrangement mechanism. This ability for simplified capacity management is discussed further in ITU-T Rec. E.360.6.
+
+Figure 3 illustrates the concept of dynamic traffic (layer 3) and transport routing (layer 2) from a generalized switching node point of view.
+
+![Diagram of a switching node showing dynamic routing methods for layer 2 and layer 3.](cfda9df1319e04207eb28bcefd1dab7b_img.jpg)
+
+The diagram illustrates a 'Switching node' represented by a dashed rectangular box. Inside the box, there are three main components connected vertically by upward-pointing arrows:
+
+- Traffic demands** (at the bottom) point to a box labeled 'Traffic router traffic trunk and connection switching (layer 3 routing)'.
+- This box points to a box labeled 'OXC Logical link switching (layer 2 routing)'.
+- The OXC box points to an arrow labeled 'Fibre link (layer 1 routing)' (at the top).
+
+To the right of the diagram, under the heading 'Dynamic routing method', there are two text blocks:
+
+- 'Dynamic routing of logical link bandwidth (T1, OC3, OC12, OC48, ..., wavelength) on fibre bandwidth; logical link restoration'
+- 'Dynamic routing of traffic trunk bandwidth on logical link bandwidth and connections on traffic trunk bandwidth; traffic trunk restoration'
+
+The label 'E.360.5\_F3' is located near the bottom right of the switching node box.
+
+Diagram of a switching node showing dynamic routing methods for layer 2 and layer 3.
+
+**Figure 3/E.360.5 – Dynamic transport (layer 2) routing and dynamic connection (layer 3) routing**
+
+Figure 3 illustrates the relationship of the call-level and transport-level dynamic routing methods used in the dynamic transport routing network. Dynamic connection routing, such as discussed in ITU-T Rec. E.360.2, is used to route calls comprising the underlying traffic demand. Traffic trunk capacity allocations are made for each VNET on the transport link capacity. For each call the originating node analyzes the called number and determines the terminating node, class-of-service, and virtual network. The originating node tries to set up the call on the traffic trunk to the terminating node and, if unavailable, dynamic routing is used at to rearrange the traffic trunk capacity as required to match the traffic demands and to achieve inter-node diversity, access diversity, and traffic trunk restoration following node, OXC, or fiber transport failures. The traffic trunk capacities are allocated by the traffic router to the logical link bandwidth, and the logical link bandwidth allocated by the bandwidth broker to the fiber-link bandwidth, such that the bandwidth is efficiently used according to the level of traffic demand between the nodes.
+
+At the traffic demand level in the transmission hierarchy, flow requests are switched using dynamic traffic routing on the logical link network by node routing logic. At the OC3 and higher demand levels in the transmission hierarchy, logical link demands are switched using OXC systems, which allow dynamic transport routing to route transport demands in accordance with traffic levels. Real-time logical link and real-time response to traffic congestion can be provided by OXC dynamic transport routing to improve network performance.
+
+As illustrated in Figure 4, the dynamic transport routing network concept includes backbone routers (BRs), access routers (ARs), and OXCs. Access routers could route traffic from local offices, access tandems, customer premises equipment, and overseas international switching centers. Here a logical link transmission channel could consist, for example, of OC3-, OC12-, OC48-, or OCx-level bandwidth allocation. An OXC can cross-connect (or "switch") a logical link transmission channel within one terminating fiber wavelength channel in a dense wavelength division multiplexing (DWDM) system to a like-channel within another fiber DWDM system. In the example illustrated, access routers connect to the OXC by means of transport links such as link AX1, and BRs connect to OXCs by means of transport links such as BX1. A number of backbone fiber/DWDM transport links interconnect the OXC network elements, such as links XX1 and XX2. Backbone logical links are terminated at each end by OXCs and are routed over fiber/DWDM spans on the physical transport network on the shortest physical paths. Inter-BR logical links are formed by cross-connecting the bandwidth channels through OXCs between a pair of BRs.
+
+![Diagram of a dynamic transport routing network showing four access routers (AR1-AR4), four optical cross-connections (OXC1-OXC4), and four backbone routers (BR1-BR4) connected via fiber links (AX, BX, XX).](5b4e774d63e0e0ed73801a9247755e5f_img.jpg)
+
+The diagram illustrates a network architecture with four access routers (AR<sub>1</sub>, AR<sub>2</sub>, AR<sub>3</sub>, AR<sub>4</sub>) at the top, each connected to an optical cross-connect (OXC) via an access link (AX<sub>1</sub>, AX<sub>2</sub>, AX<sub>3</sub>, AX<sub>4</sub>). The OXCs (OXC<sub>1</sub>, OXC<sub>2</sub>, OXC<sub>3</sub>, OXC<sub>4</sub>) are arranged horizontally and interconnected by backbone fiber links (XX<sub>1</sub>, XX<sub>2</sub>, XX<sub>3</sub>). Below each OXC is a backbone router (BR<sub>1</sub>, BR<sub>2</sub>, BR<sub>3</sub>, BR<sub>4</sub>) connected via a transport link (BX<sub>1</sub>, BX<sub>2</sub>, BX<sub>3</sub>, BX<sub>4</sub>). Logical links are shown as dashed lines within the OXCs and BRs. Access logical links (A) connect ARs to BRs through OXCs. Backbone logical links (B) connect BRs to each other through the OXC network. A legend at the bottom left defines the symbols: AR (Access router), OXC (Optical cross-connect), BR (Backbone router), A (Access logical link), and B (Backbone logical link (BLL)). A second legend on the right lists specific logical links: B1 (BLL BR<sub>1</sub> - BR<sub>2</sub>), B2 (BLL BR<sub>1</sub> - BR<sub>3</sub>), B3 (BLL BR<sub>1</sub> - BR<sub>4</sub>), B4 (BLL BR<sub>2</sub> - BR<sub>3</sub>), B5 (BLL BR<sub>2</sub> - BR<sub>4</sub>), and B6 (BLL BR<sub>3</sub> - BR<sub>4</sub>). The diagram is labeled E.360.5\_F4.
+
+Diagram of a dynamic transport routing network showing four access routers (AR1-AR4), four optical cross-connections (OXC1-OXC4), and four backbone routers (BR1-BR4) connected via fiber links (AX, BX, XX).
+
+**Figure 4/E.360.5 – Dynamic transport routing network**
+
+For example, the backbone logical link B2 from BR<sub>1</sub> to BR<sub>3</sub> is formed by connecting between BR<sub>1</sub> and BR<sub>3</sub> through fiber/DWDM links BX<sub>1</sub>, XX<sub>1</sub>, XX<sub>2</sub>, and BX<sub>3</sub> by making appropriate cross-connects through OXC<sub>1</sub>, OXC<sub>2</sub>, and OXC<sub>3</sub>. Logical links have variable bandwidth capacity controlled by the bandwidth broker implementing the dynamic transport routing network. Access logical links are formed by cross-connecting between ARs and BRs, for example, access router AR<sub>1</sub> connected on fiber/DWDM links AX<sub>1</sub> and BX<sub>1</sub> through OXC<sub>1</sub> to BR<sub>1</sub> or, alternatively, access router AR<sub>1</sub> connected on fiber/DWDM links AX<sub>1</sub>, XX<sub>1</sub>, and BX<sub>2</sub> cross-connected through OXC<sub>1</sub> and OXC<sub>2</sub> to BR<sub>2</sub>. For additional network reliability, backbone routers and access routers may be dual-homed to two OXCs, possibly in different building locations.
+
+# 6 Dynamic transport routing examples
+
+There are significant network design opportunities with dynamic transport routing and, in this clause, we give examples of dynamic transport routing over different time scales. These examples illustrate the network efficiency and performance improvements possible with seasonal, weekly, daily, and real-time transport rearrangement.
+
+An illustration of dynamic transport routing for varying seasonal traffic demands is given in Figure 5. As seasonal demands shift, the dynamic transport network is better able to match demands to routed transport capacity, thus gaining efficiencies in transport requirements. Figure 5 illustrates how dynamic transport routing achieves network capacity reductions, and shows how transport demand is routed according to varying seasonal requirements. As seasonal demands shift, the dynamic transport network is better able to match demands to routed transport capacity, thus gaining efficiencies in transport requirements. Figure 5 illustrates the variation of winter and summer capacity demands. With fixed transport routing, the maximum termination capacity and transport capacity are provided across the seasonal variations because, in a manual environment without dynamic transport rearrangement, it is not possible to disconnect and reconnect capacity on such short cycle times. When transport rearrangement is automated with dynamic transport routing, however, the termination and transport design can be changed on a weekly, daily, or, with high-speed packet switching, real-time basis to exactly match the termination and transport design with the actual network demands. Notice that in the fixed transport network, there is unused termination and transport capacity that cannot be used by any demands; sometimes this is called "trapped capacity" because it is available, but cannot be accessed by any actual demand. The dynamic transport network, in contrast, follows the capacity demand with flexible transport routing and, together with transport network design, it reduces the trapped capacity.
+
+![Figure 5/E.360.5 – Dynamic transport routing vs. fixed transport routing. The figure is divided into three horizontal sections. The top section shows 'Node-to node capacity demand' for Winter and Summer. In Winter, LA to NY is 50, LA to FL is 50, and NY to FL is 100. In Summer, LA to NY is 50, LA to FL is 100, and NY to FL is 50. The middle section shows 'Fixed transport routing' for both seasons. It features a network with 500 terminations and 350 transport capacity units. The bottom section shows 'Dynamic transport routing' for both seasons. It features a network with 450 terminations and 300 transport capacity units. Both sections include diagrams for Winter and Summer showing node connections and capacity values.](42ff8b598a0818ca8b6ef30850ad5f4e_img.jpg)
+
+Node-to node capacity demand
+
+Fixed transport routing
+
+500 Terminations; 350 Transport capacity units
+
+Dynamic transport routing
+
+450 Terminations; 300 Transport capacity units
+
+E.360.5\_F5
+
+Figure 5/E.360.5 – Dynamic transport routing vs. fixed transport routing. The figure is divided into three horizontal sections. The top section shows 'Node-to node capacity demand' for Winter and Summer. In Winter, LA to NY is 50, LA to FL is 50, and NY to FL is 100. In Summer, LA to NY is 50, LA to FL is 100, and NY to FL is 50. The middle section shows 'Fixed transport routing' for both seasons. It features a network with 500 terminations and 350 transport capacity units. The bottom section shows 'Dynamic transport routing' for both seasons. It features a network with 450 terminations and 300 transport capacity units. Both sections include diagrams for Winter and Summer showing node connections and capacity values.
+
+**Figure 5/E.360.5 – Dynamic transport routing vs. fixed transport routing**
+
+Therefore, the variation of demands leads to capacity-sharing efficiencies which, in the example of Figure 5, reduce termination capacity requirements by 50 node terminations, or approximately 10 percent compared with the fixed transport network, and by 50 transport capacity requirements, or approximately 14 percent. Therefore, with dynamic transport routing capacity utilization can be made more efficient in comparison with fixed transport routing because, with dynamic transport network design, the link sizes can be matched to the network load.
+
+With dynamic traffic routing and dynamic transport routing design models, reserve capacity can be reduced in comparison with fixed transport routing. In-place capacity that exceeds the capacity required to exactly meet the design loads with the objective performance is called reserve capacity. Reserve capacity comes about because load uncertainties, such as forecast errors, tend to cause capacity buildup in excess of the network design that exactly matches the forecast loads. Reluctance to disconnect and rearrange traffic trunk and transport capacity contributes to this reserve capacity buildup. Typical ranges for reserve capacity are from 15 to 25 percent or more of network cost. Models show that dynamic traffic routing compared with fixed traffic routing provides a potential 5 percent reduction in reserve capacity while retaining a low level of short-term capacity design [A98].
+
+With dynamic transport network design, the link sizes can be matched to the network load. With dynamic transport routing, the link capacity disconnect policy becomes, in effect, one in which link capacity is always disconnected when not needed for the current traffic loads. Models given in [FHH79] predict reserve capacity reductions of 10% or more under this policy, and the results presented in Annex A, based on weekly dynamic transport design, substantiate this conclusion.
+
+Weekly design and rearrangement of logical link capacity can approach zero reserve capacity designs. Figures 6 and 7 illustrate the changing of routed transport capacity on a weekly basis between node pairs A-B, C-D, and B-E, as demands between these node pairs change on a weekly basis.
+
+![Diagram of a dynamic transport routing network showing nodes A, B, C, D, and E. Nodes A, C, and E are traffic routers (diamonds), while B and D are optical cross-connections (circles). The network consists of three main links: C-B, B-A, and A-E. The C-B link is labeled '1-OC3' at both ends. The B-A link is labeled '2-OC3s' at both ends. The A-E link is labeled '3-OC3s' at both ends. There are also intermediate nodes on the links between B and A, and between A and E. A legend at the bottom identifies the diamond as a 'Traffic router' and the circle as an 'Optical cross-connect (OXC)'. The diagram is labeled 'E.360.5_F6'.](cab0834804fb031b43865554cc8d06ab_img.jpg)
+
+Diagram of a dynamic transport routing network showing nodes A, B, C, D, and E. Nodes A, C, and E are traffic routers (diamonds), while B and D are optical cross-connections (circles). The network consists of three main links: C-B, B-A, and A-E. The C-B link is labeled '1-OC3' at both ends. The B-A link is labeled '2-OC3s' at both ends. The A-E link is labeled '3-OC3s' at both ends. There are also intermediate nodes on the links between B and A, and between A and E. A legend at the bottom identifies the diamond as a 'Traffic router' and the circle as an 'Optical cross-connect (OXC)'. The diagram is labeled 'E.360.5\_F6'.
+
+**Figure 6/E.360.5 – Dynamic transport routing network weekly arrangement (week 1 load pattern)**
+
+
+
+![Diagram of dynamic transport routing peak day design showing four access routers (AR1-AR4) connected to optical cross-connections (OXC1-OXC4) and digital cross-connections (DCS3). The diagram illustrates various logical links (A, B1-B6, BX1-BX4) and their interconnections between backbone routers (BR1-BR4).](33ed1f9b27c7c21c797aa928b0f06851_img.jpg)
+
+The diagram illustrates a network architecture for dynamic transport routing. At the top, four access routers (AR<sub>1</sub>, AR<sub>2</sub>, AR<sub>3</sub>, AR<sub>4</sub>) are shown, each connected to an access logical link (AX<sub>1</sub>, AX<sub>2</sub>, AX<sub>3</sub>, AX<sub>4</sub>). These links connect to optical cross-connections (OXC<sub>1</sub>, OXC<sub>2</sub>, OXC<sub>4</sub>) and a digital cross-connection (DCS<sub>3</sub>). The OXC<sub>1</sub> is connected to a backbone router (BR<sub>1</sub>) via logical links A, B1, B2, and B3. The OXC<sub>2</sub> is connected to BR<sub>2</sub> via links A, B1, B4, B5, and BX<sub>2</sub>. The DCS<sub>3</sub> is connected to BR<sub>3</sub> via links A, B2, B4, B6, and BX<sub>3</sub>. The OXC<sub>4</sub> is connected to BR<sub>4</sub> via links A, B3, B5, B6, and BX<sub>4</sub>. The backbone routers (BR<sub>1</sub>, BR<sub>2</sub>, BR<sub>3</sub>, BR<sub>4</sub>) are interconnected by backbone logical links (BLL): B1 (BR<sub>1</sub>-BR<sub>2</sub>), B2 (BR<sub>1</sub>-BR<sub>3</sub>), B3 (BR<sub>1</sub>-BR<sub>4</sub>), B4 (BR<sub>2</sub>-BR<sub>3</sub>), B5 (BR<sub>2</sub>-BR<sub>4</sub>), and B6 (BR<sub>3</sub>-BR<sub>4</sub>). The diagram also shows intermediate logical links (XX<sub>1</sub>, XX<sub>2</sub>, XX<sub>3</sub>) and various other connections (B1, B2, B3, B4, B5, B6) within the network segments.
+
+Diagram of dynamic transport routing peak day design showing four access routers (AR1-AR4) connected to optical cross-connections (OXC1-OXC4) and digital cross-connections (DCS3). The diagram illustrates various logical links (A, B1-B6, BX1-BX4) and their interconnections between backbone routers (BR1-BR4).
+
+E.360.5\_F8
+
+AR Access router  
+ OXC Optical cross-connect  
+ DCS Digital cross-connect  
+ BR Backbone router  
+ A Access logical link  
+ B Backbone logical link (BLL)
+
+B1 BLL BR<sub>1</sub> - BR<sub>2</sub>  
+ B2 BLL BR<sub>1</sub> - BR<sub>3</sub>  
+ B3 BLL BR<sub>1</sub> - BR<sub>4</sub>  
+ B4 BLL BR<sub>2</sub> - BR<sub>3</sub>  
+ B5 BLL BR<sub>2</sub> - BR<sub>4</sub>  
+ B6 BLL BR<sub>3</sub> - BR<sub>4</sub>
+
+**Figure 8/E.360.5 – Dynamic transport routing peak day design**
+
+Dynamic transport routing can provide dynamic restoration of failed capacity, such as that due to fiber cuts, onto spare or backup transport capacity. Dynamic transport routing provides a self-healing network capability to ensure a networkwide path selection and immediate adaptation to failure.
+
+![Figure 9/E.360.5 – Dynamic transport routing peak day design. The diagram shows a network topology with four access routers (AR1, AR2, AR3, AR4) connected to optical cross-connections (OXC1, OXC2, OXC3, OXC4) via access logical links (AX1, AX2, AX3, AX4). The OXCs are interconnected by backbone logical links (BLL) labeled B1 through B6. Each OXC is also connected to a backbone router (BR1, BR2, BR3, BR4) via a set of logical links (A, B1, B2, B3, B4, B5, B6). The diagram illustrates the dynamic transport routing paths for peak day design, showing how traffic is distributed across the network elements.](fa859e4e468bfb2710a94527f2c504af_img.jpg)
+
+Figure 9/E.360.5 – Dynamic transport routing peak day design. The diagram shows a network topology with four access routers (AR1, AR2, AR3, AR4) connected to optical cross-connections (OXC1, OXC2, OXC3, OXC4) via access logical links (AX1, AX2, AX3, AX4). The OXCs are interconnected by backbone logical links (BLL) labeled B1 through B6. Each OXC is also connected to a backbone router (BR1, BR2, BR3, BR4) via a set of logical links (A, B1, B2, B3, B4, B5, B6). The diagram illustrates the dynamic transport routing paths for peak day design, showing how traffic is distributed across the network elements.
+
+E.360.5\_F9
+
+AR Access router  
+ OXC Optical cross-connect  
+ BR Backbone router  
+ A Access logical link  
+ B Backbone logical link (BLL)
+
+B1 BLL BR<sub>1</sub> - BR<sub>2</sub>  
+ B2 BLL BR<sub>1</sub> - BR<sub>3</sub>  
+ B3 BLL BR<sub>1</sub> - BR<sub>4</sub>  
+ B4 BLL BR<sub>2</sub> - BR<sub>3</sub>  
+ B5 BLL BR<sub>2</sub> - BR<sub>4</sub>  
+ B6 BLL BR<sub>3</sub> - BR<sub>4</sub>
+
+**Figure 9/E.360.5 – Dynamic transport routing peak day design**
+
+FASTAR [CED91], for example, implements central automatic control of transport switching devices to quickly restore service following a transport failure. As illustrated in Figure 10, a fiber cut can disrupt large traffic trunk capacities, and dynamic transport restoration can quickly restore transport capacity. Dynamic transport routing provides a self-healing network capability to ensure a networkwide path selection and immediate adaptation to failure. As illustrated in Figure 10, a fiber cut near the Nashville node severed 8.576 Gbit/s of traffic trunk capacity of switched-network traffic (there was also private-line traffic), and after dynamic transport restoration a total of 3.84 Gbit/s of traffic trunk capacity was still out of service in the switched network. In the example, dynamic transport restoration is implemented by centralized automatic control of transport cross-connect devices to quickly restore service following a transport failure, such as caused by a cable cut. Over the duration of this event, more than 12 000 calls were blocked in the switched network, almost all of them originating or terminating at the Nashville node, and it is noteworthy that the blocking in the network returned to zero after the 4.736 Gbit/s of traffic trunk capacity was restored in the first 11 minutes, even though there was still 3.84 Gbit/s of traffic trunk capacity still out of service.
+
+Dynamic traffic routing was able to find paths on which to complete traffic even though there was far less logical link capacity than normal, even after the dynamic transport restoration. Hence, dynamic traffic routing, in combination with dynamic transport restoration, provides a self-healing network capability, and even though the cable was repaired two hours after the cable cut, degradation of service was minimal. In this example, dynamic traffic routing also provided priority routing for selected customers and services, as described in ITU-T Rec. E.360.3, which permits priority calls to be routed in preference to other calls, and blocking of the priority services is essentially zero throughout the whole event.
+
+Over the duration of an event, calls are blocked until sufficient capacity is restored for the network to return to zero blocking. That is, both dynamic transport routing and dynamic traffic routing are able to find available paths on which to restore the failed traffic. Hence, this example clearly illustrates how real-time dynamic traffic routing in combination with real-time dynamic transport routing can provide a self-healing network capability, and even if the cable is repaired two hours after the cut, degradation of service is minimal. This improved network performance provides additional service revenues as formerly blocked calls are completed, and it improves service quality to the customer.
+
+![Figure 10/E.360.5: Line graph showing blocking percentage at Nashville node over time following a fibre cut and subsequent restoration. The graph shows two lines: 'Normal services' which peak at 25% blocking at 10 minutes, and 'Priority services' which peak at 5% blocking at 10 minutes. Both lines return to 0% blocking after 20 minutes. The x-axis is 'Minutes' from 0 to 120. The y-axis is 'Blocking at Nashville node (%)' from 0 to 30. Key events marked: Fibre cut (4:25 PM) at 0 minutes, Dynamic transport restoration at 10 minutes, and Fibre repaired at 120 minutes. Below the graph, a table provides capacity details.](af06598cfb31b517e79b50d74f72a0ca_img.jpg)
+
+| Event / Feature               | Capacity / Status                                                                          |
+|-------------------------------|--------------------------------------------------------------------------------------------|
+| Fibre cut (4:25 PM)           | 15.44 Gbit/s logical link capacity<br>8.576 Gbit/s traffic trunk capacity                  |
+| Dynamic transport restoration | 10.4 Gbit/s logical link capacity restored<br>4.736 Gbit/s traffic trunk capacity restored |
+| Fibre repaired                | Normal services restored                                                                   |
+
+Figure 10/E.360.5: Line graph showing blocking percentage at Nashville node over time following a fibre cut and subsequent restoration. The graph shows two lines: 'Normal services' which peak at 25% blocking at 10 minutes, and 'Priority services' which peak at 5% blocking at 10 minutes. Both lines return to 0% blocking after 20 minutes. The x-axis is 'Minutes' from 0 to 120. The y-axis is 'Blocking at Nashville node (%)' from 0 to 30. Key events marked: Fibre cut (4:25 PM) at 0 minutes, Dynamic transport restoration at 10 minutes, and Fibre repaired at 120 minutes. Below the graph, a table provides capacity details.
+
+**Figure 10/E.360.5 – Fibre cut example with dynamic traffic routing and dynamic transport routing**
+
+These examples illustrate that implementation of dynamic transport routing provides better network performance at reduced cost. These benefits are similar to those achieved by dynamic traffic routing and, as shown, the combination of dynamic traffic and transport routing provides synergistic reinforcement to achieve these network improvements.
+
+The implementation of a dynamic transport routing network allows significant reductions in capital costs and network management and design expense with rearrangeable transport capacity design methods. Automated logical link provisioning and rearrangement lead to annual operations expense savings. Other network management and design impacts, leading to additional reduction in operations expense, are to simplify logical link provisioning systems; automate preservice logical-link testing, and simplify maintenance systems; integrate logical-link capacity forecasting, administration, and bandwidth allocation into capacity planning and delivery; simplify node and transport planning; and automate inventory tracking.
+
+# 7 Reliable transport network design
+
+In the event of link, node, or other network failure, the network design needs to provide sufficient surviving capacity to meet the required performance levels. For example, if a major fiber link fails, it could have a catastrophic effect on the network because traffic for many node pairs could not use the failed link. Similarly, if one of the nodes fails, it could isolate a whole geographic area until the node is restored to service.
+
+With these two kinds of major failures in mind, we present here reliable transport routing models to achieve reliable network design, so as to provide service for predefined restoration objectives for
+
+any transport link or node failure in the network, and continue to provide connections to customers with essentially no perceived interruption of service. This approach tries to integrate capabilities in both the traffic and transport networks to make the network robust, or insensitive to failure. The basic aims of these models are to provide link diversity and protective capacity augmentation where needed so that specific "network robustness" objectives, such as traffic restoration level objectives, are met under failure events. This means that the network is designed so that it carries at least the fraction of traffic known as the traffic restoration level (TRL) under the failure event. For example, a traffic restoration level objective of 70% means that under any single transport link failure in the transport network, at least 70% of the original traffic for any affected node pair is still carried after the failure; for the unaffected node pairs, the traffic is carried at the normal blocking probability grade-of-service objective. These design models provide designs that address the network response immediately after a network event. It is also desirable to have transport restoration respond after the occurrence of the network event to bring service back to normal. Transport restoration is also addressed in this Recommendation.
+
+Reliable network performance objectives may require, for example, the network to carry 50% of its busy-hour load on each link within five minutes after a major network failure, in order to eliminate isolations among node pairs. Such performance may be provided through traffic restoration techniques, which include link diversity, traffic restoration capacity and dynamic traffic routing. Reliable network performance objectives might also require a further reduction of connection setup blocking level to less than 5% within, say, 30 minutes to limit the duration of degraded service. This is possible through transport restoration methods that utilize transport nodes along with centralized transport restoration control. A further objective may be to restore at least 50% of severed trunks in affected links within this time period.
+
+The transport restoration process restores capacity for switched, as well as dedicated ("private-line"), services in the event of link failures. In one implementation, transport restoration is conducted via a centralized system that restores the affected transport capacity until all available restoration capacity is exhausted. Optimization of the total cost of transport restoration capacity is possible through a design that increases sharing opportunities of the restoration capacity among different failure scenarios. Real-time transport restoration may also require the use of dedicated restoration capacity for each link and, thus, a lesser opportunity for sharing the restoration capacity. For the purpose of this analysis, we assume that all network transport may be protected with an objective level of restoration capacity. Transport restoration level (TPRL) is the term used to specify the minimal percentage of capacity on each transport link that is restorable. A transport restoration level is implemented in the model by restoring each affected link in a failure to a specified level. Here, we further distinguish between transport restoration level for switched circuits and dedicated circuits and designate them by TPRLs and TPRLp, respectively.
+
+We now describe logical transport routing design models for survivable networks. Before we describe the models, we discuss the distinction between the traffic and transport networks and the concept of link diversity.
+
+To distinguish between the traffic and transport networks, consider the example of a three-node network in Figure 2. The physical transport network is depicted at the bottom of the figure, and the corresponding logical transport (traffic) network at the top. For example, the direct logical link for connecting nodes A and B may ride the path A-C-D-B in the physical transport network. There is not a logical link between nodes B and C, which means there is no direct traffic trunk capacity from node B to C. A single physical transport link failure may affect more than one logical link. For example, in Figure 2, the failure of the physical transport link C-D affects logical links A-D, C-D, and A-B. Logical link diversity refers to a logical link design in which direct capacity for a logical link is split on two or more different physical transport paths. For example, in Figure 1, the direct logical link capacity for the link A-D may be split on to the two physical transport paths A-B-C-D and a physically diverse path A-E-F-D. A link diversity policy, say, of 70/30 corresponds to the fact that no more than 70% of the direct logical link (traffic trunk) capacity is routed on a single physical
+
+transport link for the different transport paths for that logical link. The advantage of logical link diversity is that if a physical transport link fails, the traffic for a particular node pair can still use the direct logical link capacity that survived on the physical transport path not on the failed link.
+
+We now present models for transport routing design for physical transport link failure and node failure.
+
+## 7.1 Transport link design models
+
+We assume that we have two distinct transport paths for direct logical link capacity for each node pair. In the model, traffic demand is converted to virtual trunk demand, such as based on direct and overflow logical transport capacity, as illustrated in Figure 1 of E.360.6. Let  $v$  be the virtual trunk requirement for the traffic demand for a particular node pair. Let  $d$  be the virtual trunk capacity to be put on the primary physical transport path and  $s$  be the virtual trunk capacity to be put on the alternate physical transport paths for the direct logical link of the given node pair. Let  $b$  be the number of trunks for this traffic link that are designed by the network design model. Let  $t$  be the traffic restoration level (TRL) objective under a link failure scenario. Let  $\Delta_b$  be the link capacity augmentation that may be needed for this logical link.
+
+What we would like in a failure event is to carry a portion  $tv$  of the total virtual trunk demand for the affected node pairs. Thus, if  $tv \leq b/2$ , we set  $\Delta_b = 0$  (no augmentation) with  $d = b - tv$  and  $s = tv$ . In this way, if either transport path fails, we can carry at least  $tv$  of the virtual trunk demand. On the other hand, if  $tv > b/2$ , then we want:
+
+$$(b + \Delta_b)/2 = tv$$
+
+which implies:  $\Delta_b = 2tv - b$
+
+In this case, we set  $d = s = (b + \Delta_b)/2$ . The above procedure is repeated for every demand pair in the network. The incremental cost of the network is the cost of trunk augmentation, and routing the direct logical link capacity for each node pair, if any, on two transport paths.
+
+The above procedure can be extended to the general case of  $k$  distinct physical transport paths. So, for  $k$  distinct physical transport paths, if:
+
+$$tv \leq \frac{k-1}{k} b$$
+
+then  $\Delta_b = 0$  with  $d = b - tv$  on the first physical transport path, and  $tv/(k - 1)$  on each of the other  $(k - 1)$  transport paths. If:
+
+$$tv > \frac{k-1}{k} b$$
+
+$$\text{then: } \Delta_b = \frac{k}{k-1} tv - b$$
+
+with each of the  $k$  transport paths having  $(b + \Delta_b)/k$  trunks.
+
+A transport link model is illustrated in Figure 11, where each transport cross section is assumed on the average to contain certain fractions of switched ( $N$ ) and dedicated ( $M$ ) circuits. A portion of the switched and dedicated circuits is further presumed to be restorable in real time, such as with ring or dual-feed transmission arrangements (lowercase  $n$  and  $m$  values).
+
+Circuits that are not restored in real time are restored with transport restoration to a specified transport restoration level (TPRL) value. The lower part of Figure 11 demonstrates the interaction between the switched and dedicated capacity in the restoration process. The restoration process is assumed to restore the first unit of transport capacity (e.g. OC3) after  $x$  seconds, with  $y$  seconds to
+
+restore each additional unit of transport capacity. The restoration times are illustrative and are not critical to the reliable network design principles being discussed. SONET ring restoration can occur in about 50-200 milliseconds, and such real-time restoration is included in the model. A prioritization method is assumed, whereby transport links that carry higher-priority dedicated services are restored first. Because switched and dedicated capacity is often mixed at the logical link level, some switched capacity is also restored.
+
+Different levels of transport restoration may also be assigned for the dedicated (TPRLp) and switched (TPRLs) networks. Each type of circuit demand is then restored to the corresponding level of restoration. Figure 11 also shows how the restoration level for switched circuits varies as a function of time. Some level of traffic circuits is restored in real time (n). After x seconds, transport restoration is initiated with one unit of transport capacity being restored in each y seconds, and with a smaller fraction of each transport capacity unit being switched traffic. The switched portion in each transport capacity unit subsequently increases to a larger fraction after dedicated traffic is restored to its designated level TPRLp. Transport restoration stops after both the TPRLp and TPRLs objectives are met.
+
+![Figure 11/E.360.5 – Transport restoration model. The figure consists of two parts. The top part is a schematic diagram of a network link showing 'Real-time restoration', 'Switched trans. cap.', and 'Dedicated trans. cap.' with parameters N, n, M, and m. The bottom part is a graph of 'Restored switched transport capacity' vs 'Time (seconds)' showing a piecewise linear increase from n to TPRLs * (N - n) over time, with key time points X, TPRLd met, and TPRLs met.](96a7eac66ef72bb016c280278506ac63_img.jpg)
+
+The top diagram illustrates a network link with two parallel transport capacity paths. The upper path is labeled 'Switched trans. cap.' and has a total capacity of N. The lower path is labeled 'Dedicated trans. cap.' and has a total capacity of M. A 'Real-time restoration' arrow indicates an initial restoration level of n for the switched capacity. A parameter m is also shown for the dedicated capacity.
+
+The bottom graph plots 'Restored switched transport capacity' on the y-axis against 'Time (seconds)' on the x-axis. The y-axis has labels for n and  $TPRL_s \cdot (N - n)$ . The x-axis has labels for X,  $TPRL_d \text{ met}$ , and  $TPRL_s \text{ met}$ . The graph shows a piecewise linear increase in restored switched capacity: it starts at n, remains constant until time X, then increases linearly until  $TPRL_d \text{ met}$ , and finally increases linearly until it reaches the plateau  $TPRL_s \cdot (N - n)$  at time  $TPRL_s \text{ met}$ .
+
+$TPRL_s$  Transport restoration level for switched transport capacity  
+ $TPRL_d$  Transport restoration level for dedicated transport capacity
+
+Figure 11/E.360.5 – Transport restoration model. The figure consists of two parts. The top part is a schematic diagram of a network link showing 'Real-time restoration', 'Switched trans. cap.', and 'Dedicated trans. cap.' with parameters N, n, M, and m. The bottom part is a graph of 'Restored switched transport capacity' vs 'Time (seconds)' showing a piecewise linear increase from n to TPRLs \* (N - n) over time, with key time points X, TPRLd met, and TPRLs met.
+
+**Figure 11/E.360.5 – Transport restoration model**
+
+## 7.2 Node design models
+
+Node failure restoration design incorporates the concept of dual homing, as discussed in ITU-T Rec. E.360.2, along with multiple ingress/egress routing. With single homing, the traffic from a particular geographical area normally goes to the single node nearest to it in order to carry the ingress and egress traffic. For example, in Figure 12 the traffic from the served area A1 enters the network through node B, and, similarly, the served area A2 traffic enters the network through node C. Now, if node B fails, then area A1 gets isolated. To protect against such an event, areas A1 and A2 are homed to more than one node (to nodes A and B in this case (Figure 12, bottom)). This
+
+is the concept of dual homing, in which we address the issue of designing a reliable network when one of the nodes may fail.
+
+For every node to be protected, we assign a dual-homed node. Before failure, we assume that any load from a node to the protected node and its dual-homed node is equally divided; that is, if the original load between area A1 and node A is  $a_1$ , and between A and the dual-homed node, B, is  $a_2$ , then we assume that under normal network conditions, the load between nodes A and B is  $(a_1 + a_2)/2$ , and the same for the load between nodes A and C. We refer to this concept as balanced load. Then, under a failure event such as a node B failure, we carry load equal to  $(a_1 + a_2)/2$  between nodes A and C. (See Figure 12, bottom.) We call this design objective a 50% traffic restoration level objective in a manner quite similar to the link failure event. As we can see from the lower part of Figure 12, this restoration level of traffic from or to area A1 is then still carried.
+
+In the restoration model, the node pairs that are going to be considered for the node failure design scenarios are determined. Next, the dual-homing nodes are determined for each node and the balanced-load traffic routed accordingly. Then the  $v_k$  virtual trunks are computed for the balanced loads. For each node pair, one of the nodes is assumed to fail (say, node B). Then this node cannot have any incoming or outgoing traffic and, also, cannot be a via node for any two-link traffic between other node pairs. Using these constraints, we solve a linear programming model that minimizes the incremental augmentation cost. Then, we reverse the roles of the nodes for this pair and solve the linear programming model again with the above-mentioned constraints. This design process is repeated for every pair of candidate nodes for each node failure scenario.
+
+![Figure 12/E.360.5 – Illustration of dual homing. The diagram consists of two cloud-like network representations. The left cloud shows three diamond-shaped nodes labeled A (top), B (left), and C (right). A link between A and B is labeled a1, and a link between A and C is labeled a2. Node B is connected to 'Area A1' and node C is connected to 'Area A2'. The right cloud shows the same nodes. Node B is bypassed. Links from Area A1 and Area A2 now connect to both nodes A and C. The links between A and B, and A and C, are both labeled with the fraction (a1 + a2)/2. A small identifier 'E.360.5_F12' is in the bottom right corner.](79e1709a7317ead45379cbb8ff3ba802_img.jpg)
+
+Figure 12/E.360.5 – Illustration of dual homing. The diagram consists of two cloud-like network representations. The left cloud shows three diamond-shaped nodes labeled A (top), B (left), and C (right). A link between A and B is labeled a1, and a link between A and C is labeled a2. Node B is connected to 'Area A1' and node C is connected to 'Area A2'. The right cloud shows the same nodes. Node B is bypassed. Links from Area A1 and Area A2 now connect to both nodes A and C. The links between A and B, and A and C, are both labeled with the fraction (a1 + a2)/2. A small identifier 'E.360.5\_F12' is in the bottom right corner.
+
+**Figure 12/E.360.5 – Illustration of dual homing**
+
+# 8 Conclusions/recommendations
+
+In this Recommendation, we present and analyze dynamic transport network architectures. Dynamic transport routing is a routing and bandwidth allocation method, which combines dynamic traffic routing with dynamic transport routing and for which we provide associated network design methods. We find that networks benefit more in efficiency and performance as the ability to reassign transport bandwidth is increased, and can simplify network management and design. We present results of a number of analysis, design, and simulation studies related to dynamic transport network architectures.
+
+Models are used to measure the performance of the network for dynamic transport routing network design in comparison with the fixed transport network design, under a variety of network conditions including normal daily load patterns, unpredictable traffic load patterns such as caused by a hurricane, known traffic overload patterns such as occur on Christmas Day, and a network failure conditions such as a large fiber cut.
+
+The conclusions/recommendations reached in this Recommendation are as follows:
+
+- Dynamic transport routing is recommended and provides greater network throughput and, consequently, enhanced revenue, and at the same time capital savings should result, as discussed in ITU-T Rec. E.360.6.
+  - a) Dynamic transport routing network design enhances network performance under failure, which arises from automatic inter-backbone-router and access logical-link diversity in combination with the dynamic traffic routing and transport restoration of logical links.
+  - b) Dynamic transport routing network design is recommended and improves network performance in comparison with fixed transport routing for all network conditions simulated, which include abnormal and unpredictable traffic load patterns.
+- Traffic and transport restoration level design is recommended and allows for link diversity to ensure a minimum level of performance under failure.
+- Robust routing techniques are recommended, which include dynamic traffic routing, multiple ingress/egress routing, and logical link diversity routing; these methods improve response to node or transport failures.
+
+## Annex A
+
+## Modelling of traffic engineering methods
+
+In this annex we give modelling results for dynamic transport routing capacity design, performance under network failure, and performance under various network overload scenarios.
+
+### A.1 Dynamic transport routing capacity design
+
+Design for traffic loads with week-to-week traffic variation. Dynamic transport routing network design allows more efficient use of node capacity and transport capacity and can lead to a reduction of network reserve trunk capacity by about 10%, while improving network performance. Table A.1 illustrates a comparative forecast of a national intercity network's normalized logical-link capacity requirements for the base case without dynamic transport routing and the network requirements with dynamic transport routing network design. When week-to-week traffic variations, which reflect seasonal variations, are taken into account, as in this analysis, the dynamic transport routing design can provide a reduction in network reserve capacity. As shown in Table A.1, the traffic trunk savings always exceed 10%, which translates into a significant reduction in capital expenditures.
+
+**Table A.1/E.360.5 – Dynamic transport routing capacity savings with week-to-week seasonal traffic variations (normalized capacity)**
+
+| Forecast period | Capacity fixed transport routing design | Capacity dynamic transport routing design | Capacity savings (%) |
+|-----------------|-----------------------------------------|-------------------------------------------|----------------------|
+| Year 1          | 1.000                                   | 0.873                                     | 12.7                 |
+| Year 2          | 1.048                                   | 0.919                                     | 12.3                 |
+| Year 3          | 1.087                                   | 0.968                                     | 11.0                 |
+| Year 4          | 1.138                                   | 1.019                                     | 10.4                 |
+
+Dynamic transport routing network design for transport capacity achieves higher fiber link fill rates, which further reduces transport costs. The dynamic transport routing network implements automated inter-BR and access logical-link diversity, logical-link restoration, and node backup restoration to enhance the network survivability over a wide range of network failure conditions. We now illustrate dynamic transport routing network performance under design for normal traffic
+
+loads, fiber transport failure events, unpredictable traffic load patterns, and peak-day traffic load patterns.
+
+### A.2 Performance for network failures
+
+Simulations are performed for the fixed transport and dynamic transport network performance for a fiber cut in Newark, New Jersey, in which approximately 8.96 Gbit/s of traffic trunk capacity was lost. The results are shown in Table A.2. Here, a threshold of 50 percent or more node-pair blocking is used to identify node pairs that are essentially isolated; hence, the rearrangeable transport network design eliminates all isolations during this network failure event.
+
+**Table A.2/E.360.5 – Network performance for fiber cut in Newark, NJ**
+
+|                           | Traffic lost/delayed (%) | Number of node pairs with lost/delayed > 50% |
+|---------------------------|--------------------------|----------------------------------------------|
+| Fixed transport routing   | 14.4                     | 963                                          |
+| Dynamic transport routing | 4.2                      | 0                                            |
+
+An analysis is also performed for the network performance after transport restoration, in which the fixed and dynamic transport network designs are simulated after 29 percent of the lost trunks are restored. The results are shown in Table A.3. Again, the dynamic transport network design eliminates all network isolations, some of which still exist in the base network after traffic trunk restoration.
+
+**Table A.3/E.360.5 – Network performance for fiber cut in Newark, NJ  
+(after logical-link restoration)**
+
+|                           | Traffic lost/delayed (%) | Number of node pairs with lost/delayed > 50% |
+|---------------------------|--------------------------|----------------------------------------------|
+| Fixed transport routing   | 7.0                      | 106                                          |
+| Dynamic transport routing | 0.6                      | 0                                            |
+
+From this analysis we conclude that the combination of dynamic traffic routing, logical-link diversity design, and transport restoration provides synergistic network survivability benefits. Dynamic transport network design automates and maintains logical-link diversity, as well as access network diversity in an efficient manner, and provides automatic transport restoration after failure.
+
+A network reliability example is given for dual-homing transport demands on various OXC transport nodes. In one example, an OXC failure at the Littleton, MA node, in the model illustrated in Figure 1 is analyzed, and results given in Table A.4. Because transport demands are diversely routed between nodes and dual-homed between access nodes and OXC devices, this provides additional network robustness and resilience to traffic node and transport node failures. When the network is designed for load balancing between access and internode demands, and traffic trunk restoration is performed, the performance of the dynamic transport routing network is further improved.
+
+**Table A.4/E.360.5 – Dynamic transport network performance under OXC failure**
+
+|                                                                                  | Traffic lost/delayed (%) | Number of node pairs with lost/delayed > 50% |
+|----------------------------------------------------------------------------------|--------------------------|----------------------------------------------|
+| Fixed transport routing                                                          | 4.1                      | 231                                          |
+| Dynamic transport routing, dual-homing                                           | 1.3                      | 0                                            |
+| Dynamic transport routing, dual-homing, load balancing, logical-link restoration | 0.6                      | 0                                            |
+
+Figure A.1 illustrates a typical instance of network design with traffic restoration level objectives and transport restoration level objectives, as compared with the base network with no TRL or TPRL design objectives. In the example, a fiber link failure occurs in the model network  $f$  seconds after the beginning of the simulation, severing a large amount of transport capacity in the network and cutting off thousands of existing connections. Therefore, in the simulation results shown in Figure A.1, we see a large jump in the blocking at the instant of the cut. A transient flurry of reattempts follows as cut-off customers redial and reestablish their calls. This call restoration process is aided by the traffic restoration level design which provides link diversity, and protective transport capacity, to meet the TRL objectives immediately following a failure. This TRL design, together with the ability of dynamic traffic routing to find surviving capacity wherever it exists, quickly reduces the transient blocking level which then remains roughly constant for about  $x$  seconds until the transport restoration process begins. At  $x$  seconds after the link failure, the transport restoration process begins to restore capacity that was lost due to the failure. Blocking then continues to drop during that period when transport restoration takes place until it reaches essentially a level of zero blocking. Figure A.1 illustrates the comparison between network performances with and without the traffic and transport restoration design techniques presented in this Recommendation.
+
+This traffic restoration level design allows for varying levels of diversity on different links to ensure a minimum level of performance. Robust routing techniques such as dynamic traffic routing, multiple ingress/egress routing, and logical link diversity routing further improve response to node or transport failures. Transport restoration is necessary to reduce network blocking to low levels. Given, for example, a 50 percent traffic restoration level design, it is observed that this, combined with transport restoration of 50 percent of the failed transport capacity in affected links, is sufficient to restore the traffic to low blocking levels. Therefore, the combination of traffic restoration level design and transport restoration level design is seen both to be cost-effective and to provide fast and reliable performance. The traffic restoration level design eliminates isolations between node pairs, and transport restoration level is used to reduce the duration of poor service in the network. Traffic restoration techniques combined with transport restoration techniques provide the network with independent means to achieve reliability against multiple failures and other unexpected events and are perceived to be a valuable part of a reliable network design.
+
+![Line graph showing network congestion (lost/delayed traffic) over time for two scenarios: 'No traffic or transport restoration design' and 'Traffic and transport restoration design to meet network performance objectives'. The graph shows a sharp spike at time 'f' followed by a sustained high level for the first scenario and a rapid recovery for the second.](645bea0b27d63e4a9a300af5793ae7d2_img.jpg)
+
+The graph plots 'Network congestion (lost/delayed traffic)' on the y-axis (ranging from 0.0 to 0.5) against 'Time' on the x-axis. A vertical line at time 'f' marks the point of failure. 
+   
+Two data series are shown:
+   
+1. 'No traffic or transport restoration design': This line spikes to approximately 0.48 at time 'f', then drops to about 0.3 and remains relatively flat with minor oscillations.
+   
+2. 'Traffic and transport restoration design to meet network performance objectives': This line spikes to approximately 0.25 at time 'f', then drops sharply, reaching near zero by time 'f' + some duration, indicating a successful restoration.
+   
+The label 'E.360.5\_F13' is present in the bottom right corner of the graph area.
+
+Line graph showing network congestion (lost/delayed traffic) over time for two scenarios: 'No traffic or transport restoration design' and 'Traffic and transport restoration design to meet network performance objectives'. The graph shows a sharp spike at time 'f' followed by a sustained high level for the first scenario and a rapid recovery for the second.
+
+**Figure A.1/E.360.5 – Network performance for link failure with traffic and transport restoration design**
+
+### A.3 Performance for general traffic overloads
+
+The national network model is designed for dynamic transport routing with normal engineered traffic loads using the discrete event flow optimization (DEFO) model described in ITU-T Rec. E.360.6, and it results in a 15 percent savings in reserve trunk capacity over the fixed transport routing model. In addition to this large savings in network capacity, the network performance under a 10 percent overload results in the performance comparison illustrated in Table A.5. Hence, dynamic transport routing network designs achieve significant capital savings while also achieving superior network performance.
+
+**Table A.5/E.360.5 – Network performance for 10% traffic overload**
+
+|                           | Traffic lost/delayed (%) | Node pair maximum lost/delayed (%) |
+|---------------------------|--------------------------|------------------------------------|
+| Fixed transport routing   | 0.11                     | 17.3                               |
+| Dynamic transport routing | 0                        | 0                                  |
+
+### A.4 Performance for unexpected overloads
+
+Dynamic transport routing network design provides load balancing of node traffic load and logical-link capacity so that sufficient reserve capacity is provided throughout the network to meet unexpected demands on the network. The advantage of such design is illustrated in Table A.6, which compares the simulated network blocking for the fixed transport routing network design and dynamic transport routing network design during a hurricane-caused focused traffic overload in the northeastern United States. Such unexpected focused overloads are not unusual in a switched network, and the additional robustness provided by dynamic transport routing network design to the unexpected traffic overload patterns is clear from these results.
+
+**Table A.6/E.360.5 – Network performance for unexpected traffic overload  
+(focused overload in Northeastern US caused by hurricane)**
+
+|                           | Traffic lost/delayed (%) | Node pair maximum lost/delayed (%) |
+|---------------------------|--------------------------|------------------------------------|
+| Fixed transport routing   | 0.43                     | 22.7                               |
+| Dynamic transport routing | 0.28                     | 13.3                               |
+
+Another illustration of the benefits of load balancing is given in Figure A.2, in which a 25% traffic overload is focused on a node in Jackson, Mississippi.
+
+![Figure A.2/E.360.5: A line graph showing 'Hourly calls blocked' on the y-axis (0 to 15,000) versus 'Hour' on the x-axis (19 h to 24 h). Two lines are plotted: a solid line for 'Fixed transport routing' and a dashed line for 'Dynamic trans. rtg.'. The solid line peaks at approximately 15,000 calls blocked at 20 h, while the dashed line remains near zero. Annotations indicate logical-link capacities of 138.3 Gbit/s for fixed routing and 116.4 Gbit/s for dynamic routing. The graph is labeled E.360.5_F14.](c17eaf807acd5faec68da19dd16929be_img.jpg)
+
+| Hour | Fixed transport routing (calls blocked) | Dynamic transport routing (calls blocked) |
+|------|-----------------------------------------|-------------------------------------------|
+| 19 h | 0                                       | 0                                         |
+| 20 h | ~15,000                                 | ~1,000                                    |
+| 21 h | ~11,000                                 | ~1,000                                    |
+| 22 h | 0                                       | 0                                         |
+| 23 h | 0                                       | 0                                         |
+| 24 h | 0                                       | 0                                         |
+
+Figure A.2/E.360.5: A line graph showing 'Hourly calls blocked' on the y-axis (0 to 15,000) versus 'Hour' on the x-axis (19 h to 24 h). Two lines are plotted: a solid line for 'Fixed transport routing' and a dashed line for 'Dynamic trans. rtg.'. The solid line peaks at approximately 15,000 calls blocked at 20 h, while the dashed line remains near zero. Annotations indicate logical-link capacities of 138.3 Gbit/s for fixed routing and 116.4 Gbit/s for dynamic routing. The graph is labeled E.360.5\_F14.
+
+**Figure A.2/E.360.5 – Dynamic transport routing performance for 25% overload  
+on Jackson, Mississippi, node**
+
+Because the dynamic transport network is load balanced between access demands and inter-BR demands, this provides additional network robustness and resilience to unexpected traffic overloads, even though the dynamic transport routing network in this model has more than 15 percent less capacity than the fixed transport routing network. In this example, blocking-triggered rearrangement is allowed in the dynamic transport network. That is, as soon as node-pair blocking is detected, additional logical-link capacity is added to the affected links by cross-connecting spare node-termination capacity and spare logical-link capacity, which has been freed up as a result of the more efficient dynamic transport network design. As can be seen from Figure A.2, this greatly improves the network response to the overload.
+
+### A.5 Performance for peak-day traffic loads
+
+A dynamic transport network design is performed for the Christmas traffic loads, and simulations performed for the base network and rearrangeable transport network design for the Christmas Day traffic. Results for the inter-BR blocking are summarized in Table A.7. Clearly, the rearrangeable transport network design eliminates the inter-BR network blocking, although the access node to BR blocking may still exist but is not quantified in the model. In addition to increased revenue, customer perception of network quality is also improved for these peak-day situations.
+
+**Table A.7/E.360.5 – Network performance for christmas day traffic overload**
+
+| <b>Hour of day</b> | <b>Fixed transport network traffic lost/delayed (%)</b> | <b>Dynamic transport network traffic lost/delayed (%)</b> |
+|--------------------|---------------------------------------------------------|-----------------------------------------------------------|
+| 9 to 10 am         | 17.2                                                    | 0                                                         |
+| 10 to 11 am        | 22.2                                                    | 0                                                         |
+| 11 to 12 am        | 29.7                                                    | 0                                                         |
+
+
+
+
+
+# SERIES OF ITU-T RECOMMENDATIONS
+
+|                 |                                                                                                                                |
+|-----------------|--------------------------------------------------------------------------------------------------------------------------------|
+| Series A        | Organization of the work of ITU-T                                                                                              |
+| Series B        | Means of expression: definitions, symbols, classification                                                                      |
+| Series C        | General telecommunication statistics                                                                                           |
+| Series D        | General tariff principles                                                                                                      |
+| <b>Series E</b> | <b>Overall network operation, telephone service, service operation and human factors</b>                                       |
+| Series F        | Non-telephone telecommunication services                                                                                       |
+| Series G        | Transmission systems and media, digital systems and networks                                                                   |
+| Series H        | Audiovisual and multimedia systems                                                                                             |
+| Series I        | Integrated services digital network                                                                                            |
+| Series J        | Cable networks and transmission of television, sound programme and other multimedia signals                                    |
+| Series K        | Protection against interference                                                                                                |
+| Series L        | Construction, installation and protection of cables and other elements of outside plant                                        |
+| Series M        | TMN and network maintenance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits |
+| Series N        | Maintenance: international sound programme and television transmission circuits                                                |
+| Series O        | Specifications of measuring equipment                                                                                          |
+| Series P        | Telephone transmission quality, telephone installations, local line networks                                                   |
+| Series Q        | Switching and signalling                                                                                                       |
+| Series R        | Telegraph transmission                                                                                                         |
+| Series S        | Telegraph services terminal equipment                                                                                          |
+| Series T        | Terminals for telematic services                                                                                               |
+| Series U        | Telegraph switching                                                                                                            |
+| Series V        | Data communication over the telephone network                                                                                  |
+| Series X        | Data networks and open system communications                                                                                   |
+| Series Y        | Global information infrastructure and Internet protocol aspects                                                                |
+| Series Z        | Languages and general software aspects for telecommunication systems                                                           |

marked/E/T-REC-E.370-200102-I_PDF-E/raw.md

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+
+
+![ITU logo: A globe with a lightning bolt and the letters ITU.](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg)
+
+ITU logo: A globe with a lightning bolt and the letters ITU.
+
+INTERNATIONAL TELECOMMUNICATION UNION
+
+**ITU-T**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+**E.370**
+
+(02/2001)
+
+SERIES E: OVERALL NETWORK OPERATION,  
+TELEPHONE SERVICE, SERVICE OPERATION AND  
+HUMAN FACTORS
+
+International routing plan
+
+---
+
+**Service principles when public circuit-switched  
+international telecommunication networks  
+interwork with IP-based networks**
+
+ITU-T Recommendation E.370
+
+(Formerly CCITT Recommendation)
+
+---
+
+# **OVERALL NETWORK OPERATION, TELEPHONE SERVICE, SERVICE OPERATION AND HUMAN FACTORS**
+
+|                                                                                                          |                    |
+|----------------------------------------------------------------------------------------------------------|--------------------|
+| <b>INTERNATIONAL OPERATION</b>                                                                           |                    |
+| Definitions                                                                                              | E.100–E.103        |
+| General provisions concerning Administrations                                                            | E.104–E.119        |
+| General provisions concerning users                                                                      | E.120–E.139        |
+| Operation of international telephone services                                                            | E.140–E.159        |
+| Numbering plan of the international telephone service                                                    | E.160–E.169        |
+| International routing plan                                                                               | E.170–E.179        |
+| Tones in national signalling systems                                                                     | E.180–E.189        |
+| Numbering plan of the international telephone service                                                    | E.190–E.199        |
+| Maritime mobile service and public land mobile service                                                   | E.200–E.229        |
+| <b>OPERATIONAL PROVISIONS RELATING TO CHARGING AND ACCOUNTING IN THE INTERNATIONAL TELEPHONE SERVICE</b> |                    |
+| Charging in the international telephone service                                                          | E.230–E.249        |
+| Measuring and recording call durations for accounting purposes                                           | E.260–E.269        |
+| <b>UTILIZATION OF THE INTERNATIONAL TELEPHONE NETWORK FOR NON-TELEPHONY APPLICATIONS</b>                 |                    |
+| General                                                                                                  | E.300–E.319        |
+| Phototelegraphy                                                                                          | E.320–E.329        |
+| ISDN PROVISIONS CONCERNING USERS                                                                         | E.330–E.349        |
+| <b>INTERNATIONAL ROUTING PLAN</b>                                                                        | <b>E.350–E.399</b> |
+| <b>NETWORK MANAGEMENT</b>                                                                                |                    |
+| International service statistics                                                                         | E.400–E.409        |
+| International network management                                                                         | E.410–E.419        |
+| Checking the quality of the international telephone service                                              | E.420–E.489        |
+| <b>TRAFFIC ENGINEERING</b>                                                                               |                    |
+| Measurement and recording of traffic                                                                     | E.490–E.505        |
+| Forecasting of traffic                                                                                   | E.506–E.509        |
+| Determination of the number of circuits in manual operation                                              | E.510–E.519        |
+| Determination of the number of circuits in automatic and semi-automatic operation                        | E.520–E.539        |
+| Grade of service                                                                                         | E.540–E.599        |
+| Definitions                                                                                              | E.600–E.649        |
+| Traffic engineering for IP-networks                                                                      | E.650–E.699        |
+| ISDN traffic engineering                                                                                 | E.700–E.749        |
+| Mobile network traffic engineering                                                                       | E.750–E.799        |
+| <b>QUALITY OF TELECOMMUNICATION SERVICES: CONCEPTS, MODELS, OBJECTIVES AND DEPENDABILITY PLANNING</b>    |                    |
+| Terms and definitions related to the quality of telecommunication services                               | E.800–E.809        |
+| Models for telecommunication services                                                                    | E.810–E.844        |
+| Objectives for quality of service and related concepts of telecommunication services                     | E.845–E.859        |
+| Use of quality of service objectives for planning of telecommunication networks                          | E.860–E.879        |
+| Field data collection and evaluation on the performance of equipment, networks and services              | E.880–E.899        |
+
+*For further details, please refer to the list of ITU-T Recommendations.*
+
+# **Service principles when public circuit-switched international telecommunication networks interwork with IP-based networks**
+
+## **Summary**
+
+This Recommendation defines the principles applicable to international public correspondence services provided by IP-based networks interworking with the ITU-defined, circuit-switched, public, international telecommunication networks (for example, the PSTN, ISDN and PLMN).
+
+This Recommendation is applicable to those cases where the IP-based network is implemented by a separate service provider (e.g. ROA) from the service provider of the public, circuit-switched international telecommunication network. It does not cover the case where IP technology is integrated within the international telecommunication network of a single service provider.
+
+### **Source**
+
+ITU-T Recommendation E.370 was prepared by ITU-T Study Group 2 (2001-2004) and approved under the WTSA Resolution 1 procedure on 2 February 2001.
+
+## FOREWORD
+
+The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis.
+
+The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics.
+
+The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1.
+
+In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC.
+
+## NOTE
+
+In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+## INTELLECTUAL PROPERTY RIGHTS
+
+ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process.
+
+As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database.
+
+© ITU 2001
+
+All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from ITU.
+
+## CONTENTS
+
+|                                                                                                               | Page |
+|---------------------------------------------------------------------------------------------------------------|------|
+| 1 Introduction.....                                                                                           | 1    |
+| 2 Scope.....                                                                                                  | 1    |
+| 3 References.....                                                                                             | 1    |
+| 4 Definitions .....                                                                                           | 1    |
+| 5 Abbreviations.....                                                                                          | 2    |
+| 6 General principles of interconnection.....                                                                  | 2    |
+| 7 Services.....                                                                                               | 3    |
+| 8 Service scenarios.....                                                                                      | 3    |
+| 8.1 General cases .....                                                                                       | 3    |
+| 8.2 Call from IP-based network to international telecommunication networks<br>(Scenario 1).....               | 4    |
+| 8.3 Call from international telecommunication networks to IP-based network<br>(Scenario 2).....               | 4    |
+| 8.4 Interconnection of international telecommunication networks using IP-based<br>network (Scenario 3).....   | 5    |
+| 8.5 Interconnection of IP-based networks using International Telecommunication<br>Networks (Scenario 4) ..... | 5    |
+| 9 Operation .....                                                                                             | 6    |
+| 10 Quality of service.....                                                                                    | 6    |
+| Appendix I – Bibliography .....                                                                               | 7    |
+
+## Service principles when public circuit-switched international telecommunication networks interwork with IP-based networks
+
+# 1 Introduction
+
+There is an increased availability of Internet Protocol (IP)-based networks on an international and a national basis. Users of these IP-based networks expect to be able to be connected with users of public, circuit-switched, international telecommunications networks. In order to ensure that the needs of both IP-based network users and circuit-switched, international telecommunication network users are met, principles of interworking between IP-based networks and the circuit-switched, international telecommunication networks are presented in this Recommendation.
+
+## 2 Scope
+
+This Recommendation defines the principles applicable to IP-based networks interworking with the ITU-defined, circuit-switched, international telecommunication networks (for example, the PSTN, ISDN and PLMN) for the purposes of providing international telecommunications services.
+
+This Recommendation does not cover the case where IP is used as a transport technology within the international telecommunication network of a single service provider.
+
+## 3 References
+
+The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published.
+
+- ITU-T E.105 (1992), *International telephone service*.
+- ITU-T E.106 (2000), *Description of an international emergency preference scheme (IEPS)*.
+- ITU-T E.164 (1997), *The international public telecommunication numbering plan*.
+- ITU-T H.323 (2000), *Packet-based multimedia communications systems*.
+
+# 4 Definitions
+
+This Recommendation defines the following term:
+
+**IP-based network:** a network in which the Internet Protocol is used as the ISO layer 3 protocol (OSI Reference Model).
+
+# 5 Abbreviations
+
+This Recommendation uses the following abbreviations:
+
+|       |                                                                                  |
+|-------|----------------------------------------------------------------------------------|
+| DTMF  | Dual Tone Multi-Frequency                                                        |
+| IP    | Internet Protocol                                                                |
+| ISDN  | Integrated Services Digital Network                                              |
+| ISO   | International Organization for Standardization                                   |
+| ITU   | International Telecommunication Union                                            |
+| ITU-T | International Telecommunication Union – Telecommunication Standardization Sector |
+| IWF   | Interworking Facility                                                            |
+| OSI   | Open Systems Interconnection                                                     |
+| PLMN  | Public Land Mobile Network                                                       |
+| PSTN  | Public Switched Telephone Network                                                |
+| ROA   | Recognized Operating Agency                                                      |
+| SIP   | Session Initiation Protocol                                                      |
+
+# 6 General principles of interconnection
+
+**6.1** In general, the interconnection of an IP-based network to an existing international telecommunication network should not impose any requirement for additional functionality in the international telecommunication network, nor any restriction in the normal operation of the international telecommunication network. Any added functionality should be provided in the IP-based network, unless otherwise agreed between the operators of the IP-based and international telecommunication networks. The international telecommunication network should not have to be specially engineered to compensate for possible performance variation of services supported by the IP-based network interconnected to it in order to match the performance of similar services fully supported by the international telecommunication network.
+
+**6.2** The interconnection arrangements could be formalized by an agreement between the operators of the two networks. The agreement could cover the following areas:
+
+- network topology;
+- interface specifications, including signalling systems;
+- provisioning procedures;
+- operations and maintenance procedures;
+- performance monitoring (quality of service, grade of service, traffic measurement, etc.);
+- growth management (forecasts, network planning, etc.);
+- charging and accounting arrangements.
+
+Interconnection arrangements should enable calls to be set up:
+
+- a) which originate at a terminal on an IP-based network and terminate at terminals on PSTN/ISDN/PLMN networks;
+- b) which originate at terminals on PSTN/ISDN/PLMN networks and terminate at a terminal on an IP-based network; and
+- c) which allow for backward and forward call clearing.
+
+The detection of a non-recoverable failure of any of the critical resources involved in the call shall initiate the clearing of the call.
+
+User services, which make use of end-to-end bidirectional and unidirectional DTMF signalling, should be supported, e.g. voicemail applications, conference bridge applications, etc.
+
+An inability to complete the call within the PSTN/ISDN/PLMN network should be detected and communicated to the calling party (e.g. busy tone).
+
+The ability for inband audio tones and announcements to be received by the caller should be supported (e.g. special information tones, referral messages, etc.).
+
+In order to preserve existing PSTN/ISDN/PLMN service features the following should be supported:
+
+- a) presentation of a number in ITU-T E.164 format identifying the Calling Party for Calling Line Identification Presentation;
+- b) transport of calling line identification;
+- c) transport of calling line identification restriction;
+- d) malicious call tracing;
+- e) emergency calling;
+- f) International Emergency Preference Scheme (see ITU-T E.106);
+- g) E.164 number portability.
+
+# 7 Services
+
+The services, including any supplementary services, offered by IP-based networks (voice, data, etc.) when interworking with the international telecommunication networks to provide public correspondence services should be similar to those provided on international telecommunication networks and work on an end-to-end basis unless otherwise agreed. For example, when interworking with users on the PSTN, ITU-T E.105 defines the requirements of the International Telephone Service. While it is recognized that the manner in which the services, including any supplementary services, are presented to users on an IP-based network may be different from the way in which those services are presented to users of the PSTN, ISDN and PLMN; the basic functions, as defined in the appropriate ITU-T Recommendation, should still operate across the various networks.
+
+# 8 Service scenarios
+
+## 8.1 General cases
+
+A number of scenarios may be deployed to reflect particular configurations of networks, namely:
+
+**Scenario 1:** communication between IP-based network users and International Telecommunication Network users, in which the call set-up is originated by the IP network user.
+
+**Scenario 2:** communication between IP-based network users and International Telecommunication Network users, in which the call set-up is originated by the International Telecommunication Network user.
+
+**Scenario 3:** communication between International Telecommunication Network users, using IP-based networks for the connection/trunking between the involved users.
+
+**Scenario 4:** communication between IP-based network users, using International Telecommunication Networks for the connection/trunking between the involved users.
+
+In principle the interworking between the IP-based network and the international telecommunication network can be at any level in the international telecommunication network hierarchy, e.g. local exchange, transit exchange, international exchange.
+
+## 8.2 Call from IP-based network to international telecommunication networks (Scenario 1)
+
+In this configuration, the call is established within the IP-based network towards the international telecommunication networks (see Figure 1). Any added functionality to enable interworking should be provided in the IP-based network, unless otherwise agreed between the operators of the IP-based and international telecommunication networks.
+
+![Diagram of Scenario 1: Call from IP-based network to international telecommunication networks.](562f471e8153729557e6a4ee6343c32c_img.jpg)
+
+The diagram illustrates Scenario 1. On the left, an 'H.323 or SIP [1] terminal' (represented by a computer and monitor icon) is connected to an 'IP Access' node (circle). This node is connected to an 'IP Network' cloud. A dashed orange line encloses the 'IP Network' cloud, an 'IWF' (Interworking Function) box, and a 'PSTN/ISDN/PLMN' cloud. A label 'Local or distributed function' is next to the IWF. Below the dashed line, text indicates 'Call initiated from IP Network to PSTN/ISDN/PLMN'. The 'PSTN/ISDN/PLMN' cloud is connected to a mobile phone and a desktop telephone. The identifier 'T0208480-00' is at the bottom right.
+
+Diagram of Scenario 1: Call from IP-based network to international telecommunication networks.
+
+Figure 1/E.370 – Call from IP network user to the international telecommunication network
+
+## 8.3 Call from international telecommunication networks to IP-based network (Scenario 2)
+
+In this configuration, a call is established from the international telecommunication networks towards the IP-based Network user (see Figure 2). Any added functionality to enable interworking should be provided in the IP-based network, unless otherwise agreed between the operators of the IP-based and international telecommunication networks.
+
+![Diagram of Scenario 2: Call from international telecommunication networks to IP-based network.](dbe553cf16dd14073b89a8263a428664_img.jpg)
+
+The diagram illustrates Scenario 2. On the right, an 'H.323 or SIP terminal' (represented by a computer and monitor icon) is connected to an 'IP Access' node (circle), which is connected to an 'IP Network' cloud. On the left, a mobile phone and a desktop telephone are connected to a 'PSTN/ISDN/PLMN' cloud, which is connected to an 'IWF' (Interworking Function) box. A label 'Local or distributed function' is next to the IWF. The 'IWF' is connected to the 'IP Network' cloud. A dashed orange line encloses the 'PSTN/ISDN/PLMN' cloud, the 'IWF' box, and the 'IP Network' cloud. A label 'Call initiated from PSTN/ISDN/PLMN to IP Network' is inside the dashed line. The identifier 'T0208490-00' is at the bottom right.
+
+Diagram of Scenario 2: Call from international telecommunication networks to IP-based network.
+
+Figure 2/E.370 – Call from international telecommunication networks to an IP-based network user
+
+## 8.4 Interconnection of international telecommunication networks using IP-based network (Scenario 3)
+
+In this case, the IP-based network is provided by a separate entity (e.g. ROA) from the international telecommunication network (see Figure 3). It does not cover the case where IP technology is integrated within the international telecommunication network of a single service provider.
+
+The traffic, technical, economical, and administrative advantages/disadvantages should be considered before such interconnection is proposed by network operators.
+
+Any added functionality to enable interworking should be provided in the IP-based network, unless otherwise agreed between the operators of the IP-based and international telecommunication networks.
+
+![Diagram of Scenario 3: Call from international telecommunication network to another international telecommunication network via an IP-based network.](daa4a6fa7e2ba1954258f86b4928eb32_img.jpg)
+
+The diagram illustrates the network architecture for Scenario 3. At the top, a 'Terminating Network' cloud labeled 'PSTN/ISDN/PLMN' is connected to a mobile phone and a desktop telephone. Below this, an 'IP Network' cloud is connected to the terminating network via an 'IWF' (Interworking Function) block labeled 'Local or distributed function'. At the bottom, an 'Originating Network' cloud labeled 'PSTN/ISDN/PLMN' is connected to a mobile phone and a desktop telephone. This originating network is connected to the 'IP Network' via another 'IWF' block, also labeled 'Local or distributed function'. A dashed orange line with an arrow at the right end, labeled 'Call initiated from PSTN/ISDN/PLMN to PSTN/ISDN/PLMN', indicates the call path. The code 'T0208500-00' is visible in the bottom right corner of the diagram area.
+
+Diagram of Scenario 3: Call from international telecommunication network to another international telecommunication network via an IP-based network.
+
+Figure 3/E.370 – Call from international telecommunication network to another international telecommunication network via an IP-based network
+
+## 8.5 Interconnection of IP-based networks using International Telecommunication Networks (Scenario 4)
+
+In this case, the IP-based network is provided by a separate entity (e.g. ROA) from the international telecommunication network (see Figure 4). It does not cover the case where IP technology is integrated within the international telecommunication network of a single service provider.
+
+Any added functionality to enable interworking should be provided in the IP-based network, unless otherwise agreed between the operators of the IP-based and international telecommunication networks.
+
+![Diagram illustrating a call from an IP-based network user to another IP-based network user via an international telecommunication network. The diagram shows two H.323 or SIP terminals connected to IP Access nodes, which are connected to IP Networks. These IP Networks are connected to IWF (Interworking Function) nodes, which are then connected to a PSTN/ISDN/PLMN network. The PSTN/ISDN/PLMN network is connected to another IWF node, which is connected to another IP Network, which is connected to another IP Access node, which is connected to another H.323 or SIP terminal. A dashed orange line indicates the call path from the first IP Network to the PSTN/ISDN/PLMN network. The text 'Local or distributed function' is associated with each IWF node. The text 'Call initiated from IP Network to PSTN/ISDN/PLMN' is placed near the first IWF node. The text 'TO208510-00' is at the bottom right.](cfef993dcc8fb513de79eb1f93cf26ae_img.jpg)
+
+Diagram illustrating a call from an IP-based network user to another IP-based network user via an international telecommunication network. The diagram shows two H.323 or SIP terminals connected to IP Access nodes, which are connected to IP Networks. These IP Networks are connected to IWF (Interworking Function) nodes, which are then connected to a PSTN/ISDN/PLMN network. The PSTN/ISDN/PLMN network is connected to another IWF node, which is connected to another IP Network, which is connected to another IP Access node, which is connected to another H.323 or SIP terminal. A dashed orange line indicates the call path from the first IP Network to the PSTN/ISDN/PLMN network. The text 'Local or distributed function' is associated with each IWF node. The text 'Call initiated from IP Network to PSTN/ISDN/PLMN' is placed near the first IWF node. The text 'TO208510-00' is at the bottom right.
+
+**Figure 4/E.370 – Call from an IP-based network user to another IP-based network user via an international telecommunication network**
+
+# 9 Operation
+
+**9.1** When interworking between IP-based networks and international telecommunication networks the operational procedures for services should, wherever possible, be the same as for those on the international telecommunication networks. The same tones, announcements, service codes and signals, etc., used in the international telecommunication services should be recognized and where appropriate returned by the IP-based network. For interworking between IP-based networks and international telecommunication networks, User-to-Network signalling (where a user on one network is accessing functionality supplied on the other network), Network-to-Network signalling, and User-to-User signalling must be consistently interpreted across the various networks. The latter case is particularly important when users must interact with interactive voice response systems.
+
+**9.2** For users on the international telecommunication networks to reach users on IP-based networks, terminals on the IP-based network should be addressable using the international numbering plan applicable to the international telecommunication services (i.e. ITU-T E.164).
+
+**9.3** There should be mechanisms in place to cater for the needs of any call recording, billing and international accounting functions that might be required. For example, an answer supervisory signal should be returned by the terminating network when an incoming call is established.
+
+# 10 Quality of service
+
+When international telecommunication networks interwork with IP-based networks, the quality of service experienced by the users should, as far as practicable, be the same as if there had been no interworking involved.<sup>1</sup>
+
+<sup>1</sup> Categories of speech quality are defined in ITU-T G.109 [2].
+
+## APPENDIX I
+
+### **Bibliography**
+
+- [1] HANDLEY (M.), SCHULZRINNE (H.), SCHOOLER (E.), and ROSENBERG (J.):  
+SIP: session initiation protocol, *Request for Comments 2543, Internet Engineering Task Force* 1999.
+- [2] ITU-T G.109 (1999), *Definition of categories of speech transmission quality*.
+
+### SERIES OF ITU-T RECOMMENDATIONS
+
+|                 |                                                                                                                                |
+|-----------------|--------------------------------------------------------------------------------------------------------------------------------|
+| Series A        | Organization of the work of ITU-T                                                                                              |
+| Series B        | Means of expression: definitions, symbols, classification                                                                      |
+| Series C        | General telecommunication statistics                                                                                           |
+| Series D        | General tariff principles                                                                                                      |
+| <b>Series E</b> | <b>Overall network operation, telephone service, service operation and human factors</b>                                       |
+| Series F        | Non-telephone telecommunication services                                                                                       |
+| Series G        | Transmission systems and media, digital systems and networks                                                                   |
+| Series H        | Audiovisual and multimedia systems                                                                                             |
+| Series I        | Integrated services digital network                                                                                            |
+| Series J        | Cable networks and transmission of television, sound programme and other multimedia signals                                    |
+| Series K        | Protection against interference                                                                                                |
+| Series L        | Construction, installation and protection of cables and other elements of outside plant                                        |
+| Series M        | TMN and network maintenance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits |
+| Series N        | Maintenance: international sound programme and television transmission circuits                                                |
+| Series O        | Specifications of measuring equipment                                                                                          |
+| Series P        | Telephone transmission quality, telephone installations, local line networks                                                   |
+| Series Q        | Switching and signalling                                                                                                       |
+| Series R        | Telegraph transmission                                                                                                         |
+| Series S        | Telegraph services terminal equipment                                                                                          |
+| Series T        | Terminals for telematic services                                                                                               |
+| Series U        | Telegraph switching                                                                                                            |
+| Series V        | Data communication over the telephone network                                                                                  |
+| Series X        | Data networks and open system communications                                                                                   |
+| Series Y        | Global information infrastructure and Internet protocol aspects                                                                |
+| Series Z        | Languages and general software aspects for telecommunication systems                                                           |

marked/E/T-REC-E.417-200502-I_PDF-E/raw.md

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+
+
+**ITU-T**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+**E.417**
+
+(02/2005)
+
+SERIES E: OVERALL NETWORK OPERATION,  
+TELEPHONE SERVICE, SERVICE OPERATION AND  
+HUMAN FACTORS
+
+Network management – International network  
+management
+
+# --- **Framework for the network management of IP-based networks**
+
+ITU-T Recommendation E.417
+
+## ITU-T E-SERIES RECOMMENDATIONS
+
+## OVERALL NETWORK OPERATION, TELEPHONE SERVICE, SERVICE OPERATION AND HUMAN FACTORS
+
+## INTERNATIONAL OPERATION
+
+|                                                        |             |
+|--------------------------------------------------------|-------------|
+| Definitions                                            | E.100–E.103 |
+| General provisions concerning Administrations          | E.104–E.119 |
+| General provisions concerning users                    | E.120–E.139 |
+| Operation of international telephone services          | E.140–E.159 |
+| Numbering plan of the international telephone service  | E.160–E.169 |
+| International routing plan                             | E.170–E.179 |
+| Tones in national signalling systems                   | E.180–E.189 |
+| Numbering plan of the international telephone service  | E.190–E.199 |
+| Maritime mobile service and public land mobile service | E.200–E.229 |
+
+## OPERATIONAL PROVISIONS RELATING TO CHARGING AND ACCOUNTING IN THE INTERNATIONAL TELEPHONE SERVICE
+
+|                                                                |             |
+|----------------------------------------------------------------|-------------|
+| Charging in the international telephone service                | E.230–E.249 |
+| Measuring and recording call durations for accounting purposes | E.260–E.269 |
+
+## UTILIZATION OF THE INTERNATIONAL TELEPHONE NETWORK FOR NON-TELEPHONY APPLICATIONS
+
+|                 |             |
+|-----------------|-------------|
+| General         | E.300–E.319 |
+| Phototelegraphy | E.320–E.329 |
+
+## ISDN PROVISIONS CONCERNING USERS
+
+E.330–E.349
+
+## INTERNATIONAL ROUTING PLAN
+
+E.350–E.399
+
+## NETWORK MANAGEMENT
+
+|                                         |                    |
+|-----------------------------------------|--------------------|
+| International service statistics        | E.400–E.404        |
+| <b>International network management</b> | <b>E.405–E.419</b> |
+
+|                                                             |             |
+|-------------------------------------------------------------|-------------|
+| Checking the quality of the international telephone service | E.420–E.489 |
+|-------------------------------------------------------------|-------------|
+
+## TRAFFIC ENGINEERING
+
+|                                                                                   |             |
+|-----------------------------------------------------------------------------------|-------------|
+| Measurement and recording of traffic                                              | E.490–E.505 |
+| Forecasting of traffic                                                            | E.506–E.509 |
+| Determination of the number of circuits in manual operation                       | E.510–E.519 |
+| Determination of the number of circuits in automatic and semi-automatic operation | E.520–E.539 |
+| Grade of service                                                                  | E.540–E.599 |
+| Definitions                                                                       | E.600–E.649 |
+| Traffic engineering for IP-networks                                               | E.650–E.699 |
+| ISDN traffic engineering                                                          | E.700–E.749 |
+| Mobile network traffic engineering                                                | E.750–E.799 |
+
+## QUALITY OF TELECOMMUNICATION SERVICES: CONCEPTS, MODELS, OBJECTIVES AND DEPENDABILITY PLANNING
+
+|                                                                                             |             |
+|---------------------------------------------------------------------------------------------|-------------|
+| Terms and definitions related to the quality of telecommunication services                  | E.800–E.809 |
+| Models for telecommunication services                                                       | E.810–E.844 |
+| Objectives for quality of service and related concepts of telecommunication services        | E.845–E.859 |
+| Use of quality of service objectives for planning of telecommunication networks             | E.860–E.879 |
+| Field data collection and evaluation on the performance of equipment, networks and services | E.880–E.899 |
+
+For further details, please refer to the list of ITU-T Recommendations.
+
+## **ITU-T Recommendation E.417**
+
+# **Framework for the network management of IP-based networks**
+
+## **Summary**
+
+This Recommendation lays down a framework for supporting and defining the role of network management in IP-based telecommunications networks. IP-based networks generally make use of various telecommunications technologies that support a range of multimedia services such as voice, data, still image and video. Such IP-based networks are referred to here as converged networks. Network Management (NM) goals, principles and functions that are intended for use with IP-based equipment are defined. The major part of this Recommendation suggests ways to monitor traffic and provides some indication of parameters for promptly detecting abnormal network traffic conditions. After detection of an abnormal condition, automatic and possibly manual controls must be temporarily applied to the network to alleviate the problem until it is resolved. It is also necessary to frequently check the performance of the network after applying the NM controls to note whether the control is mitigating the problem and to determine when to modify or remove it from the network.
+
+## **Source**
+
+ITU-T Recommendation E.417 was approved on 24 February 2005 by ITU-T Study Group 2 (2005-2008) under the Resolution 1.
+
+## **History**
+
+|     |       |            |
+|-----|-------|------------|
+| 1.0 | E.417 | 2001-02-02 |
+| 2.0 | E.417 | 2005-02-24 |
+
+## FOREWORD
+
+The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis.
+
+The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics.
+
+The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1.
+
+In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC.
+
+## NOTE
+
+In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure e.g. interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some other obligatory language such as "must" and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party.
+
+## INTELLECTUAL PROPERTY RIGHTS
+
+ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process.
+
+As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database.
+
+© ITU 2005
+
+All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU.
+
+## CONTENTS
+
+|                                                         | Page |
+|---------------------------------------------------------|------|
+| 1 Scope .....                                           | 1    |
+| 2 References.....                                       | 1    |
+| 3 Definitions .....                                     | 2    |
+| 4 Abbreviations.....                                    | 3    |
+| 5 Introduction .....                                    | 4    |
+| 6 Network management goals, concerns and policies ..... | 4    |
+| 6.1 Network management goals .....                      | 5    |
+| 6.2 Network management concerns .....                   | 6    |
+| 6.3 Network management policies .....                   | 7    |
+| 7 Network management functions .....                    | 8    |
+| 8 Network status and performance data.....              | 9    |
+| 8.1 Network status of IP-based traffic .....            | 9    |
+| 8.2 Measurements.....                                   | 9    |
+| 8.3 Alarms and notifications.....                       | 11   |
+| 9 Network management controls .....                     | 11   |
+| 9.1 Information-transfer-based controls .....           | 12   |
+| 9.2 Routing-based controls .....                        | 12   |
+| 9.3 Address-based controls.....                         | 12   |
+| 9.4 Flow admission control .....                        | 12   |
+| 9.5 Other NM controls.....                              | 13   |
+
+
+
+# Framework for the network management of IP-based networks
+
+# 1 Scope
+
+This Recommendation is intended to support and define the role of network management in IP-based telecommunications networks. IP-based networks generally make use of various telecommunications technologies that support a range of multimedia services such as voice, data, still image and video. In this Recommendation, such IP-based networks are referred to as *converged networks*. Addressed here are the Network Management (NM) goals, principles and functions intended for use with IP-based equipment operating in such converged networks or in dedicated IP networks.
+
+This Recommendation lays down a framework for IP network management. It shall, however, be enhanced as the research in the field of IP network management is progressed. The major part of this Recommendation suggests ways to monitor traffic and provides some indication of parameters for promptly detecting abnormal network traffic conditions. After detection of an abnormal condition, automatic and possibly manual controls must be temporarily applied to the network to alleviate the problem until it is resolved. It is also necessary to frequently check the effects of the NM controls to note whether the control is mitigating the problem and to determine when to modify or remove it from the network.
+
+## 2 References
+
+The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation
+
+- ITU-T Recommendation E.370 (2001), *Service principles when public circuit-switched international telecommunication networks interwork with IP-based networks*.
+- ITU-T Recommendation E.410 (1998), *International network management – General information*.
+- ITU-T Recommendation E.411 (2000), *International network management – Operational guidance*.
+- ITU-T Recommendation E.412 (2003), *Network management controls*.
+- ITU-T Recommendation E.413 (1988), *International network management – Planning*.
+- ITU-T Recommendation E.414 (1988), *International network management – Organization*.
+- ITU-T Recommendation E.415 (1991), *International network management guidance for common channel signalling system No. 7*.
+- ITU-T Recommendation E.416 (2000), *Network management principles and functions for B-ISDN traffic*.
+- ITU-T Recommendation E.800 (1994), *Terms and definitions related to quality of service and network performance including dependability*.
+- ITU-T Recommendation H.245 (2005), *Control protocol for multimedia communication*.
+
+- ITU-T Recommendation H.323 (2003), *Packet-based multimedia communications systems*.
+- ITU-T Recommendation I.371 (2004), *Traffic control and congestion control in B-ISDN*.
+- ITU-T Recommendation M.3000 (2000), *Overview of TMN Recommendations*.
+- ITU-T Recommendation Y.1540 (2002), *Internet protocol data communication service – IP packet transfer and availability performance parameters*.
+
+In addition, other standards bodies such as the Internet Engineering Task Force (IETF) have been working in related areas such as IP Quality of Service. These include the following:
+
+- IETF RFC 2330 (1998), *Framework for IP Performance Metrics*.
+- IETF RFC 2386 (1998), *A Framework for QoS-based Routing in the Internet*.
+
+# 3 Definitions
+
+This Recommendation defines the following terms:
+
+**3.1 call:** An association between two or more users or between a user and a network entity within a telecommunications network for the purpose of exchanging information. The call begins with the call set-up procedure and ends with the call termination procedure.
+
+**3.2 class of service:** Any of the network-oriented designations or features that can distinguish between various services, or application-layer uses, of lower-layer telecommunications capabilities for the purpose of more effectively accommodating the specialized network performance needs of specific services.
+
+**3.3 connection-oriented:** Connection-oriented refers to the transfer of information between two entities by first establishing a path (or connection) for the information transfer. The communication proceeds through three well-defined phases: connection establishment, information transfer, and connection release. The most common example of connection-oriented information transfer is a telephone call over a circuit-switched network. Other examples of connection-oriented information exchange are networks based on ITU-T Rec. X.25, Frame Relay (FR), Transmission Control Protocol (TCP) and Asynchronous Transfer Mode (ATM).
+
+**3.4 connectionless:** Connectionless refers to the transfer of information between two entities without first establishing a path (or connection) for the information transfer. Examples of connectionless transport include the Internet Protocol (IP) and User Datagram Protocol (UDP).
+
+**3.5 converged network:** IP-based networks that generally make use of various telecommunications technologies to support a range of multimedia services such as voice, data, still image and video.
+
+**3.6 gateway:** A network element that enables real-time communication between other network elements and/or customer premises equipments (CPE) that have dissimilar protocols. This includes supporting voice communication between terminals on a packet network, e.g., IP network, and terminals on a circuit-switched network.
+
+**3.7 link:** A point-to-point (physical or virtual) connection used for transporting information between two nodes. A link could, for example, be a leased line, or it could be implemented as a logical connection over an Ethernet, a frame relay network, an ATM network, or any other network technology that functions below the network layer of the Open Systems Interconnection (OSI) model.
+
+**3.8 multimedia service:** A telecommunications service that supports the simultaneous use of multiple media types (e.g., voice, data, video).
+
+- 3.9 network performance:** The performance of a portion of a telecommunications network that is measured between a pair of network-user or network-network interfaces using objectively defined and observed performance parameters.
+- 3.10 quality of service (QoS):** QoS is defined in ITU-T Rec. E.800 as "collective effect of service performance, which determine the degree of satisfaction of a user of the service".
+- 3.11 router:** In the broadest sense, any communications equipment that forwards information on a connectionless basis. Typically, routers are special purpose computers, which operate at Layer 3 of the OSI reference model and forward information based on a Layer 3 address which has network-wide significance. For example, Internet routers forward IP packets based on their destination addresses. Routers operate without using connections, as opposed to switches which do establish connections.
+- 3.12 switch:** A switch is a device that dynamically interconnects physical or virtual links to form a connection for information transfer.
+- 3.13 virtual connection:** A type of connection used for packet data transfer in which apparent connections are established through appropriate correlation of link-layer addresses.
+
+## 4 Abbreviations
+
+This Recommendation uses the following abbreviations:
+
+|        |                                                 |
+|--------|-------------------------------------------------|
+| APS    | Automatic Protection Switching                  |
+| ATM    | Asynchronous Transfer Mode                      |
+| B-ISDN | Broadband Integrated Services Digital Network   |
+| CPE    | Customer Premises Equipment                     |
+| FR     | Frame Relay                                     |
+| IETF   | Internet Engineering Task Force                 |
+| IP     | Internet Protocol                               |
+| ISP    | Internet Service Provider                       |
+| LAN    | Local Area Network                              |
+| NE     | Network Element                                 |
+| N-ISDN | Narrow-band Integrated Services Digital Network |
+| NM     | Network Management                              |
+| NTM    | Network Traffic Management                      |
+| OAM    | Operation, Administration and Maintenance       |
+| OSI    | Open Systems Interconnection                    |
+| PDH    | Plesiochronous Digital Hierarchy                |
+| PSTN   | Public Switched Telephone Network               |
+| QoS    | Quality of Service                              |
+| SDH    | Synchronous Digital Hierarchy                   |
+| SLA    | Service Level Agreement                         |
+| TCP    | Transmission Control Protocol                   |
+| TMN    | Telecommunications Management Network           |
+
+|     |                                  |
+|-----|----------------------------------|
+| UDP | User Datagram Protocol           |
+| UNI | User Network Interface           |
+| URL | Uniform Resource Locator         |
+| WAN | Wide Area Network                |
+| WDM | Wavelength Division Multiplexing |
+
+# 5 Introduction
+
+This Recommendation presents a framework for extending the network management aspects given by ITU-T Recs E.410, E.411 and E.412 to the services based on the Internet Protocol (IP). It also establishes a direction for further study in the important area of Network Traffic Management (NTM) for IP. Extension of these Network Management aspects to IP requires consideration of the IP transfer capabilities, the multiple Quality of Service (QoS) classes, Service Level Agreements (SLAs) and automated routing control procedures that can exist in IP-based networks. This Recommendation also describes some network management functions of the IP-based network. These IP network management functions are intended to interwork with traffic and congestion controls and the measurements of traffic and performance that exist in IP routing equipment for the purpose of maintaining adequate network performance under abnormal conditions.
+
+Significant differences exist between connectionless and connection-oriented networks. For connection-oriented networks, both the physical connections that support circuit-switched telephony and the virtual connections that support other forms of packet-oriented telecommunications, such as Asynchronous Transfer Mode (ATM) and Frame Relay (FR), provide an end-to-end path that remains associated with a telecommunications session (for example, a phone call) throughout the life of that session. For connectionless IP-based networks, all of the IP packets associated with a particular session can be sent without reference to any such underlying end-to-end path. However, practical experience in managing converged networks is showing the desirability of establishing, at least in some cases, associations between the IP packets relating to a particular session and a path provided by means of accompanying technologies such as ATM, SDH or WDM.
+
+To assure a satisfactory level of network performance, a robust and fast network management capability is desired to promptly detect any traffic-related problem in the network and try to resolve it as quickly as possible. The role of manual controls has been minimized due to specific IP-based network characteristics such as:
+
+- a) the capabilities of a connectionless network to manage most situations automatically;
+- b) volatility of congestion-related incidents and the minimal time scale available for human intervention;
+- c) complexity of IP-based networks due to the implementation of various service categories.
+
+Before a definitive synthesis of NM principles and solutions for IP-based networks can occur, further technical information is needed concerning the characterization of IP performance (including the impacts of performance impairments on IP-based services) and the resource management problems facing IP equipment in a converged network context. Accordingly, this Recommendation is properly viewed as a framework Recommendation that will guide further research in this field.
+
+# 6 Network management goals, concerns and policies
+
+Network management concerns itself with the maintenance of adequate network performance under a variety of conditions, which can include exceptional traffic loads within some network portions, system failure, element outage, etc. The overall process of network management involves the observation of relevant traffic and performance data, suitable analysis of that data, and the resulting
+
+implementation of appropriate network management controls. The effectiveness of an implemented set of network management controls is then evaluated based on new observations of traffic and performance data, which are then analysed and used as a basis to remove or further modify, if necessary, the current set of network management controls.
+
+## 6.1 Network management goals
+
+IP-based applications are most effectively managed in the context of converged voice and data networks, which typically involve substantial amounts of both IP-specific and non-IP-specific equipment types. As an example, Figure 1 illustrates some of the generic equipment types often found in these converged networks.
+
+![Diagram of a converged voice and data network (Figure 1/E.417).](5a4e62bead259c258d069fd3663ea670_img.jpg)
+
+The diagram illustrates a network architecture with various components. On the left, a 'TCP/IP terminal' is connected to an 'Access (wireless, cable, circuit switch, etc.)' box. This box is connected to an 'IP router' (shaded grey). Below this 'IP router' is an 'Add-Drop multiplexer' (white). The 'IP router' is also connected to an 'ATM switch' (white) via an 'IP/ATM' link. The 'Add-Drop multiplexer' is connected to another 'IP router' (shaded grey) via an 'IP/SDH' link. This second 'IP router' is connected to a 'Frame relay switch' (white) via an 'IP/Frame Relay' link. The 'Frame relay switch' is connected to a third 'IP router' (shaded grey). This third 'IP router' is connected to an 'ISP host' (shaded grey). A label 'E.417\_F1' is present near the ISP host. A legend at the bottom left indicates that shaded grey boxes represent 'IP-specific equipment' and white boxes represent 'Non-IP-specific equipment'.
+
+Diagram of a converged voice and data network (Figure 1/E.417).
+
+**Figure 1/E.417 – An example of a converged voice and data network**
+
+General network management goals for circuit-switched telephony have been described in ITU-T Rec. E.410. Although they have been defined for international network management based on circuit switching, they can be extended and may be applied to other networks. With some modifications and enhancements, such goals are still valid for IP applications in converged networks. The enhanced set will constitute the initial set of IP network management goals. Further study and experience will be needed to validate the application of these principles to IP-based networks. The following is the initial set of network management goals for converged networks:
+
+- utilize all possible network resources when dealing with a network traffic problem;
+- inhibit traffic congestion and prevent its spread;
+- make economically efficient use of network resources by rejecting attempts that have a poor chance of succeeding;
+- when the offered load is approaching the network capacity limit, favour completing those communication attempts that require the least amount of resources.
+
+## 6.2 Network management concerns
+
+Network management concerns can be resolved by automatic or manual detection of the problem and then the network manager may take appropriate actions to resolve the problem in order to provide adequate network performance to customers. Such action in a converged network must be done in the shortest time possible by the network manager or preferably by a support system. Some IP-based services such as Voice over IP require special attention due to their low tolerance for delay and delay variation.
+
+The following are some of the major concerns of IP network management.
+
+### 6.2.1 Transmission failure
+
+When a transmission failure occurs (e.g., when a cable is cut or extremely damaged), network performance may become degraded unless the failure can be quickly detected and an alternate path found (e.g., via Automatic Protection Switching (APS)).
+
+The impact of a transmission failure can have different effects in connection-oriented and connectionless networks. Such effects are listed in Table 1 below:
+
+**Table 1/E.417 – The effect of transmission failure on connection-oriented and connectionless networks**
+
+|                                                      | Connection-oriented                                                                                                                                                                                                                                                                            | Connectionless                                                                                                                                                     |
+|------------------------------------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| At the time of failure                               | <ul style="list-style-type: none"><li>With APS, a short interruption until connectivity is restored on an alternate path<sup>a)</sup></li><li>Without APS, existing connections are lost; no impact on new connections</li><li>Without APS, potential congestion on alternate routes</li></ul> | <ul style="list-style-type: none"><li>Effectively no break as packets are rerouted around the failure</li><li>Potential congestion on the alternate path</li></ul> |
+| At the time of restoration to "normal" configuration | <ul style="list-style-type: none"><li>With APS, a short break</li><li>Without APS, no impact on switched services</li></ul>                                                                                                                                                                    | <ul style="list-style-type: none"><li>Buffer overflow due to packets arriving from both alternate and normal paths</li><li>Packets out of sequence</li></ul>       |
+
+<sup>a)</sup> For a physical layer APS, the typical interruption is of the order of tens of milliseconds, and no connection is lost.
+
+### 6.2.2 Network node failure
+
+There may be occasions when a node (e.g., IP router module, gateway, switch, etc.) fails, adversely impacting the Network Performance. In such cases, network managers require near real-time status of node availability thus enabling the affected node to be quickly identified and the appropriate action rapidly undertaken.
+
+### 6.2.3 Network node overload
+
+A network node such as a router or a switch can be overloaded, that is, when the capacity of a network node has been exceeded by the demand, because, for example:
+
+- more IP packets are entering the node than can be effectively processed and transmitted (for example, resulting in buffer overflows);
+- more call requests are being offered to a switch within the IP-based network than can be supported by that switching fabric;
+- more signalling messages are being offered to a switch than can be processed.
+
+### **6.2.4 Network overload**
+
+There are occasions when the network becomes overloaded, that is, when the capacity of the network has been exceeded by the demand. This may be caused by, for example:
+
+- peak days;
+- natural disasters;
+- focused overloads;
+- node or transmission failures which have widespread impact.
+
+### **6.2.5 Interference among services**
+
+In a converged network there is the potential for interference between different services that share common network resources. Some of the services may be of a critical nature (e.g., emergency services, business services and government services) and may need to be given special attention by network management in a manner consistent with an Administration's policies.
+
+### **6.2.6 Inter-networking**
+
+Inter-networking between different network operators and technologies must be addressed to ensure that adequate network performance is achieved for all IP-based applications. Such inter-networking can be within an operator's network using multiple technologies or between two network operators.
+
+- Within an operator's network:
+
+On an end-to-end basis, IP packets may be transported over multiple network technologies such as ATM or wireless. It is appropriate for network management to correlate NM functions, measurements and actions among distinct network technologies in order to monitor and control the overall network.
+
+- Between network operators:
+
+It is appropriate that NM methods and procedures be developed between various network operators to ensure the adequate service performance of the IP connections.
+
+## **6.3 Network management policies**
+
+Based on network management goals and concerns, a set of NM policies needs to be devised. Besides NM goals listed in 6.1, individual network operators may have additional network management policies that support their business objectives. Such policies may, for example, include:
+
+- meeting service and performance standards set by regulatory bodies, where applicable;
+- meeting a network operator's own service and performance objectives;
+- meeting service level agreements established with individual customers and other groups;
+- protecting the performance, stability and operating margins of network equipment;
+- minimizing the interference by one customer, product or service upon another.
+
+NTM policies can be stated in an internal company policy document.
+
+## 7 Network management functions
+
+In the ITU-T M.3000-series Recommendations, ITU-T has categorized the functional areas supported by the Telecommunications Management Network (TMN) as performance, fault, configuration, accounting and security management. The focus of network traffic management is mostly on performance management and some fault management. Network management functions include the following:
+
+### - **Status and performance monitoring on a near real-time basis**
+
+This task is based on the use of periodically collected measurements, alarms (i.e., major, minor, critical) and notifications generated upon occurrence of significant events. These are sent from the network elements to the NM systems in a NM centre. The measurements may be used directly or they may be processed by a NM tool in order to provide useful parameters. Relevant measurements and parameters are discussed in clause 8.
+
+### - **Detecting abnormal conditions**
+
+This is performed through analysis of the collected and derived parameters, e.g., measurements, alarms, notifications and correlation with other data. Abnormal conditions can also be detected with the help of statistical algorithms and thresholding procedures.
+
+### - **Investigating and identifying abnormal network conditions**
+
+This task should provide a diagnosis of the situation that may lead to a corrective control (see clause 9). The abnormal condition is usually expressed in terms of service or traffic identifiers with their traffic characteristics.
+
+### - **Initiating corrective actions and/or controls**
+
+Once an abnormal situation has been detected and its causes identified, traffic control actions should be executed. Actions may include controls to bypass a congested or overloaded portion of the network.
+
+### - **Operational relationship**
+
+In an increasingly complex and competitive telecommunications market, it is unlikely that one network operator will be solely responsible for end-to-end delivery of traffic. Network operators will need to develop and maintain strong operational relationships with interconnecting networks, carriers or operators who deliver traffic to, or receive traffic from them and their customers.
+
+There may be opportunities to understand the sorts of interactions required to fulfil these relationships by considering the interactions which form a regular part of International operations, or inter-carrier operations in competitive markets. The following three items signify this importance:
+
+### - **Cooperating and coordinating actions with other NM centres**
+
+Different applications (e.g., telephony service) may have distinct NM centres. Cooperation between the centres may be necessary to meet a global, regional and/or customer network performance target.
+
+### - **Cooperating and coordinating with other work areas**
+
+As in the PSTN, information coming from equipment surveillance and maintenance is important. Since IP packets in a converged network may traverse through other networks such as ATM, strong cooperation must be established between all work centres.
+
+### - **Cooperating and coordinating with other network operators**
+
+IP packets may traverse from one operator's network to another. Cooperation and coordination between network operators will strengthen the network management support of IP-based network services.
+
+### - **Issuing reports about network traffic management activities**
+
+As in the PSTN, these reports are important for managers, training and planning network performance improvements.
+
+### - **Provide advanced planning for known or predictable network situations**
+
+This planning should take into consideration the impact of abnormal or special events on network traffic flows, and should also consider the requirements of particular service and traffic categories.
+
+TMN ITU-T Rec. M.3000 provides a framework for considering the functions described in this clause.
+
+# 8 Network status and performance data
+
+Network status and performance data is required to establish a rational basis for guiding the application of network management actions (e.g., applying controls and contacting other centres), and to provide a means of evaluating the effectiveness of previously applied network management controls.
+
+## 8.1 Network status of IP-based traffic
+
+A network traffic manager may be directly involved in mitigating the effect of failures, errors or external events, such as mass calling, that impacts the traffic load or pattern. It is desirable that most network traffic-related problems be detected and resolved automatically. However, network traffic managers must be informed of such automatic actions and should be able to intervene and change or override the controls.
+
+Monitoring the network is one of the primary tasks of network management that should be done in near real-time in order to observe and protect network performance. As the network is enhanced and more services are supported, the need for real-time collection and analysis of data becomes more significant. The time to deliver the data to NM systems should be minimized, and a balance should be developed between the measurement interval and the statistical significance of data. For example, a balance is needed between immediately reporting each individual lost packet and the integration of packet loss data over a measurement interval chosen to give a statistically meaningful performance estimate. Research is needed concerning time correlation in packet flows and their impacts on optimum measurement intervals for packet loss performance. In general, this monitoring function should provide network traffic managers with the current operational status of the network and its components, the traffic load, and the resulting performance.
+
+NM controls (see clause 9) must also be reviewed in conjunction with current network status data by network traffic managers to observe whether the problem has ceased or lessened in severity. Based on such review, a network traffic manager can determine whether to retain, modify or remove previously applied NM controls. Network traffic managers must also review the duration of controls. It is also necessary to investigate the amount of affected traffic to verify that traffic is properly controlled.
+
+## 8.2 Measurements
+
+To detect and isolate a problem, various data must be collected or derived. The data may, for example, come directly from NEs, or from independent measurement systems. These measurements can assist network traffic managers in controlling the traffic and safeguarding network performance and service level agreements.
+
+In this clause, measurements have been categorized into three different areas: the *network-level*, the *link-level* and the *node-level*.
+
+### 8.2.1 Some network-level measurement examples
+
+Network-level measurements provide information concerning the health of the network. Some examples of the network-level measurements include (note that the measurement interval for the following must be defined):
+
+*Attempted call count:* Total number of call attempts made to the network during the measurement interval.
+
+*Accepted call count:* The number of call attempts that are successfully completed by the network during the measurement interval.
+
+*Failed call count:* Number of call attempts that are not successfully completed by the network during the measurement interval. Calls may fail due to limited resources or any other reason.
+
+*Usage:* A measure of the intensity of calls, packets or bytes sent on the network.
+
+*Average packet count:* This parameter provides the average number of packets entering the network during the measurement interval.
+
+*Ingress packet count (IPC):* Total number of packets entering the network during the measurement interval.
+
+*Egress packet count (EPC):* Total number of packets departing from the network during the measurement interval.
+
+*Average cross-network delay:* The average difference between the time that a packet enters a network and the time it leaves the same network.
+
+*Cross-network delay variation:* A measure of the variation in cross-network delay.
+
+It is anticipated that the measurements given in this framework Recommendation will be expanded based upon further research and operating experience.
+
+### 8.2.2 Some link-level measurement examples
+
+Link-level measurements provide information about the inter-nodal activities. By having such parameters available to the network management, a possible problem can be isolated to the node or the link with abnormal parameters. Some examples of the link-level measurements include the following (note that the measurement interval for the following must be defined):
+
+*Attempted call count:* The number of call attempts on a link during the measurement interval.
+
+*Accepted call count:* The number of call attempts that are successfully placed on a link during the measurement interval.
+
+*Failed call count:* The number of call attempts that are not placed on a link during the measurement interval. The reasons for which call attempts may not be placed on this link include failures, overflows and other reasons.
+
+*Usage:* A measure of the intensity of calls, packets or bytes sent on a link.
+
+As this framework expands, additional measurements will be defined.
+
+### 8.2.3 Some node-level measurement examples
+
+Node-level measurements characterize traffic and performance from the view of a specific network node (e.g., switch, and router). Some examples of these measurements are as follows (note that the measurement interval for the following must be defined):
+
+*Attempted call count:* The number of call attempts processed by a node during the measurement interval.
+
+*Accepted call count:* The number of call attempts that are successfully completed by a node during the measurement interval.
+
+*Failed call count:* The number of call attempts that are not successfully completed by a node during the measurement interval.
+
+*Usage:* A measure of the intensity of calls, packets or bytes processed by a node.
+
+*Ingress packet count (IPC):* Total number of packets arriving at the switch or router during the measurement interval.
+
+*Egress packet count (EPC):* Total number of packets departing from the switch or router during the measurement interval.
+
+*Per cent packet loss:*  $[1 - (EPC/IPC)] \times 100$
+
+*Average cross-node delay:* The average difference between the time that a packet enters a switch or router and the time that it leaves the same switch or router.
+
+As this framework expands, additional measurements will be defined.
+
+## 8.3 Alarms and notifications
+
+A notification provides an indication of a change in status of the network or network elements. Alarms are a subset of notifications and indicate abnormal network conditions. Some alarms are generated upon violation of a pre-set condition. For example, a predefined threshold may be reached, in which case an alarm will notify the network manager of such an abnormal condition. Such alarms must be sent to the network management centre on occurrence. Some examples of the conditions under which an alarm can be generated are as follows:
+
+- when the NE is in congestion or overload condition;
+- when the NE is no longer in congestion or overload condition;
+- when a failure is detected in the NE (i.e., node or link);
+- when the failure in the NE is resolved.
+
+# 9 Network management controls
+
+To resolve network management problems pertaining to equipment handling IP packets in a converged network, a network manager should be able to apply appropriate NM controls, or such NM controls should be applied automatically. If NM controls are applied automatically, then the network manager must have the capability to remove or modify them manually. This is feasible only if proper tools are built in the network or are available to network traffic managers. Such tools can be utilized to, for example, set parameters, re-route traffic, block traffic and set thresholds.
+
+ITU-T Recommendations cover NM controls for various networks – for example ITU-T Rec. E.412 for N-ISDN and ITU-T Rec. I.371 for B-ISDN. A comparable set of NM controls for IP-based networks is needed. Some considerations and issues pertaining to the development of NM controls for IP-based networks are now described.
+
+The traditional NM concept of applying controls as close to source as possible is equally valid for IP-based networks. This may mean applying controls in an access network to protect a downstream IP network, by blocking or diverting traffic before it enters that IP network.
+
+An important class of NM controls for the PSTN includes the alterations to normal call routing procedures. Such controls are based upon a thorough knowledge of the underlying approaches for PSTN call routing under normal conditions. While ITU-T Rec. I.371 focuses on controls for ATM networks, such controls have not been standardized for IP-based networks.
+
+The development of appropriate NM controls for converged networks will likely extend those controls from the PSTN that are based upon the destination address (e.g., code blocking and call gapping). Such controls are categorized here as address-based controls.
+
+The process for developing such NM controls consists of:
+
+- a) adequately characterizing IP-related performance (see clause 8);
+- b) developing in-depth understanding of the resource management problems facing IP equipment in a converged network context;
+- c) synthesizing NM goals and principles (see clauses 6 and 7) and solutions based upon such performance characterization and in-depth understanding.
+
+In the following, some examples of possible NM controls are discussed.
+
+## **9.1 Information-transfer-based controls**
+
+A set of controls at the information-transfer level is desired for automated activation by appropriate NEs handling IP packets in a converged network. It is noted that ITU-T Rec. I.371 provides such controls for ATM equipment.
+
+With additional research and operating experience, it is possible that a basis can be established for modifying this Recommendation to establish IP information-transfer-based controls, which would better support the network management of converged networks.
+
+## **9.2 Routing-based controls**
+
+NM controls that alter the normal call routing procedures in response to congestion or to non-typical traffic loads can be valuable tools for network management. Such controls have been standardized for circuit-switched networks. When considering the operation of equipment handling IP packets in a converged network, it may be feasible to exploit the routing-based controls in circuit switches to alter the routing of at least some IP packet traffic in support of network management needs.
+
+It is generally useful to consider both expansive and restrictive NM controls based upon temporary alterations of normal routing procedures.
+
+## **9.3 Address-based controls**
+
+Restrictive NM controls can be based upon destination and/or source address (e.g., URL, IP address, sub-net address, E.164 address and e-mail address). Examples of destination address-based NM controls from the circuit-switched networks include code blocking controls and call gapping controls. These controls have proven to be effective and selective in managing focussed overloads in circuit-switched networks. An address-based control is required which limits the amount of traffic forwarded to a specified destination address or set of destination addresses. To provide additional selectivity, a source address or set of addresses may also be specified.
+
+## **9.4 Flow admission control**
+
+Though, in a best effort IP network, there is no such thing as a connection, traffic between any source destination pair of hosts typically follow the same path. It is useful to model traffic at a network element on this path in terms of "flows" where by flow we designate the set of packets using that element and relating to a particular instance of some user application. If we wish additionally to perform traffic control actions at flow level, it is necessary to introduce a more formal definition. For present purposes, an IP flow consists of a succession of packets sharing common header address attributes such as IP source and destination addresses and transport protocol port numbers and occurring with an inter-packet spacing less than a certain threshold, typically of a few seconds.
+
+The considered address attributes determine the flow identifier. A minimal flow identifier for present purposes would be the combination of the origin and destination addresses. At a much finer scale, a so-called microflow is specified by the values of the 5-tuple: IP addresses, transport protocol and port numbers. In this case the flow would typically be confined to a single TCP or UDP connection. It would be useful for traffic control to allow more flexible flow identification where, for example, the multiple components of a single Web page could be considered as a single entity. This would be possible with an adapted use of the IPv6 flow label. The feasibility of such use remains for further study.
+
+The semantics of an IP flow are comparable to those of a call in terms of the level at which quality of service is perceived. It is suggested in the present section that traffic control actions typically applied to calls in a connection-oriented network could usefully be applied to flows in an IP network. In particular, it is natural to consider the use of network management operations where admission control is applied selectively to individual flows.
+
+Admission control appears as a basic requirement to maintain network efficiency in times of network overload. In situations of overload, admission control blocks new IP flows, which would otherwise cause performance degradation to existing flows. The precise definition of overload depends on the nature of offered traffic and performance requirements. For best effort traffic with no specific performance guarantees (e.g., class 5 in ITU-T Rec. Y.1541), a link may be said to be in overload whenever demand (i.e., flow arrival rate  $\times$  mean flow size) exceeds currently available capacity over a prolonged period. For traffic with more stringent requirements (generated by audio and video applications, for example), a link will be considered to be in overload whenever demand is such that these requirements are not fulfilled. Overloads occur for a variety of reasons including equipment failures and forecasting errors.
+
+In some network architectures, admission control can be applied to connections materialized by an exchange of signals. In the present text, scope is restricted to the case of a best effort Internet. In this case, admission control can be applied to IP flows using an implicit procedure with no signalling or nominal resource reservation. Application of admission control in other IP networking architectures is for further study.
+
+In overload, an accumulation of flows due to the excess of traffic leads to very poor flow performance, causing some users or protocols to prematurely interrupt the underlying transfers. Applying admission control to IP flows to a congested link preserves the quality of service of admitted flows by ensuring them sufficient throughput even in situations of overload.
+
+In the envisaged approach, new flows are detected on the fly and implicitly rejected, when necessary, by discarding their first packets. Admitted flows acquire the status of protected flow and are stored in a list. Any packet belonging to a protected flow is forwarded and the last packet emission time is updated. Any packet not belonging to a protected flow corresponds to a new flow and will be discarded if the admissibility conditions are not satisfied. Otherwise, the packet is forwarded and the corresponding flow added to the list. Flows are removed from the list when the time since the last packet exceeds the inactivity period.
+
+The admissibility conditions to be applied may depend on the value of packet header fields such as the traffic class or the source and destination addresses or fields explicitly designating a class of service (as defined in ITU-T Rec. Y.1541). Hence, different admissibility conditions can be defined to realize effective class of service differentiation. High priority flows are blocked only in extreme congestion but all admitted flows receive excellent quality.
+
+## 9.5 Other NM controls
+
+Since the operation of equipment handling IP packets in converged networks is relatively new, it is likely that additional NM controls may be identified in the future. Other NM controls are for further study.
+
+
+
+
+
+## SERIES OF ITU-T RECOMMENDATIONS
+
+|                 |                                                                                             |
+|-----------------|---------------------------------------------------------------------------------------------|
+| Series A        | Organization of the work of ITU-T                                                           |
+| Series D        | General tariff principles                                                                   |
+| <b>Series E</b> | <b>Overall network operation, telephone service, service operation and human factors</b>    |
+| Series F        | Non-telephone telecommunication services                                                    |
+| Series G        | Transmission systems and media, digital systems and networks                                |
+| Series H        | Audiovisual and multimedia systems                                                          |
+| Series I        | Integrated services digital network                                                         |
+| Series J        | Cable networks and transmission of television, sound programme and other multimedia signals |
+| Series K        | Protection against interference                                                             |
+| Series L        | Construction, installation and protection of cables and other elements of outside plant     |
+| Series M        | Telecommunication management, including TMN and network maintenance                         |
+| Series N        | Maintenance: international sound programme and television transmission circuits             |
+| Series O        | Specifications of measuring equipment                                                       |
+| Series P        | Telephone transmission quality, telephone installations, local line networks                |
+| Series Q        | Switching and signalling                                                                    |
+| Series R        | Telegraph transmission                                                                      |
+| Series S        | Telegraph services terminal equipment                                                       |
+| Series T        | Terminals for telematic services                                                            |
+| Series U        | Telegraph switching                                                                         |
+| Series V        | Data communication over the telephone network                                               |
+| Series X        | Data networks, open system communications and security                                      |
+| Series Y        | Global information infrastructure, Internet protocol aspects and next-generation networks   |
+| Series Z        | Languages and general software aspects for telecommunication systems                        |

marked/E/T-REC-E.420-198811-I_PDF-E/raw.md

@@ -0,0 +1,417 @@
+
+
+![ITU logo](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg)
+
+The logo of the International Telecommunication Union (ITU) features the letters 'ITU' in a bold, sans-serif font, superimposed on a stylized globe with intersecting lines.
+
+ITU logo
+
+INTERNATIONAL TELECOMMUNICATION UNION
+
+**ITU-T**
+
+**E.420**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+**TELEPHONE NETWORK AND ISDN**
+
+**QUALITY OF SERVICE, NETWORK MANAGEMENT  
+AND TRAFFIC ENGINEERING**
+
+---
+
+**CHECKING THE QUALITY OF THE  
+INTERNATIONAL TELEPHONE SERVICE -  
+GENERAL CONSIDERATIONS**
+
+**ITU-T Recommendation E.420**
+
+(Extract from the *Blue Book*)
+
+---
+
+# NOTES
+
+1 ITU-T Recommendation E.420 was published in Fascicle II.3 of the *Blue Book*. This file is an extract from the *Blue Book*. While the presentation and layout of the text might be slightly different from the *Blue Book* version, the contents of the file are identical to the *Blue Book* version and copyright conditions remain unchanged (see below).
+
+2 In this Recommendation, the expression “Administration” is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+## **CHECKING THE QUALITY OF THE INTERNATIONAL TELEPHONE SERVICE – GENERAL CONSIDERATIONS**
+
+## **1 Quality of service parameters**
+
+An adequate picture of the level of quality of service (QOS) in the network can be defined by a set of parameters which are measured, registered and data processed.
+
+In Recommendation E.800 a set of performance concepts is defined in order to provide a satisfactory description of the quality of service, and the interconnection of those concepts is shown. Each performance concept can be impaired by a number of particular causes. These causes, either singly or in groups, lie behind the failure symptoms observed by the user.
+
+A user views the provided service from outside the network and his perception can be described in observed quality of service parameters. The link between the observed quality of service parameters and the impairment causes can be indicated in the form of tables.<sup>1)</sup>
+
+Five main observed quality of service parameters are derived; they reflect the quality of:
+
+- i) providing the customer with the ability to use the desired services;
+- ii) furnishing a desired level of service for:
+  - connection establishment,
+  - connection retention,
+  - connection quality,
+  - billing integrity.
+
+These main parameters can be supervised by quality of service indicators (e.g. efficiency rate, call cut-off rate, etc.).
+
+Objectives can be set for these indicators and can be revised at regular intervals.
+
+When a deterioration of these supervision indicators is detected, or when an improvement programme is started, more data must be collected by measurements to permit a more detailed analysis in order to locate the impairment causes which lie behind the observed problem areas.
+
+## **2 Methods of measuring the quality of service**
+
+2.1 The following methods of measuring the quality of service are described:
+
+- 1) service observations by external means;
+- 2) test call (simulated traffic);
+- 3) customer interviews;
+- 4) internal automatic observations.
+
+2.2 Administrations are recommended to draw up a programme for observations and tests designed for assessment of circuits and equipment, supervision of operators and evaluation of the quality of service given to subscribers. It would be desirable if telephone Administrations were to exchange statistics on quality of service.
+
+2.3 Table 1/E.422 relates to the manual and semi-automatic observations of the quality of international automatic and/or semi-automatic service. It provides in particular a check of the percentage of unsuccessful calls due to technical faults (equipment shortages or failures).
+
+Table 2/E.422 relates the same information as Table 1/E.422 but does not include information which can only be obtained by operators listening in (automatic observation).
+
+---
+
+<sup>1)</sup> Such tables can be found in the handbook cited in [1].
+
+Table 1/E.423 relates to observations on traffic set up by operators. It provides, in manual and semi-automatic service, a means of determining the efficiency of international circuits, of assessing the work of operators and the quality of transmission.
+
+Table 2/E.423 summarizes observations of the time-to-answer by operators. The table is compiled by automatic means.
+
+Table 1/E.424 is used to record the results of test calls undertaken especially when the observations shown in Table 1/E.422 make it clear that the percentage of faults is too high.
+
+The use of customer interviews as a method of measuring telephone service quality is the subject of Recommendation E.125 which is particularly concerned with the determination of sources of user difficulty which may arise when making an international automatic telephone call.
+
+Recommendation E.426 contains a general guide to the expected percentage of effective international call attempts.
+
+Table 1/E.427 may be used to supplement the information contained in Table 1/E.422 when the observations shown in that table make it clear that the percentage of faults due to customer difficulties is too high or the outcome of the application of Recommendation E.125 demonstrates the need for additional information.
+
+Recommendation E.425 describes the data that might be taken from the switching centres with respect to quality of service, and the exchange of that data.
+
+2.4 Paying attention to the quality of service of the incoming traffic stream is of major importance, since the incoming Administration is in a better position to improve the situation.
+
+In the past less attention has been paid by several Administrations to the quality of service (QOS) on incoming calls than on outgoing calls. This situation should not persist in the future.
+
+Therefore, in addition to the measurement of QOS of the outgoing traffic stream which is described in this series of Recommendations, Administrations are strongly advised to observe the incoming traffic stream with the aim to improve the QOS.
+
+## **3 Other sources of information on the quality of service**
+
+The following sources are useful to consider when trying to improve the quality of service:
+
+- subscriber complaints (see Annex B);
+- other Administrations or organizations such as INTELSAT (SPADE reports);
+- operators contacting maintenance staff for direct action;
+- operators giving information on QOS: if operator traffic is significant one might consider organizing the flow of this type of information by establishing "trouble codes", e.g. echo, no tone, no answer, etc.;
+- reports from "national" switching centres: the QOS as experienced by the subscriber does not only depend on the international network and the network of the country of destination but also on the national network of the country of origin;
+- user organizations/large companies: as large companies have much to gain from an improved QOS they might be willing to cooperate with Administrations;
+- holding time versus conversation time measurements;
+- average conversation time;
+- traffic measurements;
+- transmission measurements.
+
+## ANNEX A
+
+(to Recommendation E.420)
+
+### **A possible approach to integrate activities measuring the quality of service into an overall problem-investigating process**
+
+The flowcharts of the resource allocation process and a typical problem identification procedure are given in Figures A-1/E.420 and A-2/E.420. The numbers 1) through 10) in the figures correspond to the processes described below.
+
+- 1) The exception threshold is set to detect possible isolated destinations. It is up to the individual Administration to set the value.
+- 2) A destination could be regarded as being under isolated condition when the bid frequency is significant enough to show that there is some demand to the destination (e.g. 20 attempts per day) without or nearly without answer.
+- 3) The most practical way to find out whether improvements may be possible is "consultation with other Administrations".
+- 4) Apply, if possible, network management actions, e.g. alternative routing.
+- 5) The destination priority,  $P$ , for each destination is calculated as follows:
+
+$$P = BID^{2)} \times (TABR - MABR)$$
+
+where
+
+$BID^{2)}$  is the number of total bids to the destination during a certain period of time (for example, 1 month);
+
+$TABR$  is the target  $ABR^{3)}$  (answer bid ratio) performance which is expected as the result of the service improvement activities;
+
+$MABR$  is the measured  $ABR^{3)}$  to the destination during the same period with  $BID$ .
+
+The  $TABR$  is set for each destination and can be based on the average historic  $ABR$  and should be higher than that value.
+
+In order to comply with Recommendation E.426, § 2.2, the  $TABR$  to be used in the formula for  $P$  given above should not be lower than the  $MABR$  experienced one period earlier.
+
+- 6) In order to comply with § 2.4, it is suggested to consider also the *total* international incoming traffic stream as one of the elements which require QOS improvements. It should be noted that the procedure can be well applied to domestic destinations, for example, on an area code basis, and can be applied on an incoming route basis.
+- 7) Perform detailed analysis: when possible, monitor circuit group performance and do analyses on a destination code basis. It is essential to be aware of "killer trunks" (though observation of the QOS is not directly intended to discover killer trunks).
+- 8) Discuss possible improvements with counterpart.
+- 9) In Recommendation M.710 (General maintenance organization for the international automatic and semi-automatic service) the basic maintenance elements, their functions and the cooperation between the elements are described. Recommendation M.1230 (Assessment of the performance of the international telephone network) gives guidance on the relationship between service quality observations, network performance assessment and maintenance procedures. It should be noted that the QOS very much depends on the proper operation of maintenance elements and maintenance procedures. Therefore, Administrations faced with QOS problems are strongly advised to be attentive to the maintenance Recommendations contained in Volume IV.
+- 10) If this procedure does not lead to a successful conclusion, then an escalation procedure may be required (see Recommendation M.711).
+
+---
+
+<sup>2)</sup> Paid minutes or the revenues can be used.
+
+<sup>3)</sup> In case  $ABR$  cannot be used,  $ASR$  (answer seizure ratio) is considered to be an acceptable substitute. Seizures,  $TASR$  and  $MASR$  are then applicable.
+
+![Flowchart for PROCESS ResourceAllocation. It starts with DCL Clearances Natural : = 0; and branches into two main paths: one for clearing isolation conditions and another for revenue improvement. The isolation path checks for destinations with unweighted ABR < exception threshold, then checks if any more are found. If not, it checks if the destination is isolated. If isolated, it checks if improvements are possible. If not possible, it informs entities. If possible, it identifies problems. The revenue path calculates destination priorities and chooses the highest priority destination, then checks if further resource commitment is justified. If not justified, it identifies problems. The right side of the diagram shows a sub-process for 'Wait Clearances', 'Trouble Clearance', and 'Clearances : = Clearances - 1', followed by a decision 'Effective rate normal/improved?'. If not normal/improved, it identifies problems. If normal/improved, it checks if 'Clearances = 0'. If not zero, it loops back to 'Wait Clearances'. If zero, it ends. Annotations include /*1)*/ through /*6)*/ and references to Fig. A-2/E.420. A label T0201270-88 is at the bottom right.](a7d78d22e465dea388b31d0739f9d0cd_img.jpg)
+
+```
+
+graph TD
+    Start([ ]) --> Init["DCL Clearances Natural : = 0;"]
+    Init --> Step1["Choose (next) destination with unweighted ABR < exception threshold"]
+    Step1 --> Decision1{"any more found?"}
+    Decision1 -- "no" --> Step5["Calculate destination priorities based on targets, blds, ABR"]
+    Decision1 -- "yes" --> Decision2{"is destination isolated?"}
+    Step5 --> Step6["Choose (next) highest priority destination"]
+    Step6 --> Decision3{"Further resource commitment justified?"}
+    Decision3 -- "no" --> Problem1[["Problem identification (Clearances)  
+/*Fig. A-2/E.420*/"]]
+    Problem1 --> Step1
+    Decision3 -- "yes" --> Problem2[["Problem identification (Clearances)  
+/*Fig. A-2/E.420*/"]]
+    Problem2 --> Step1
+    Decision2 -- "no" --> Step1
+    Decision2 -- "yes" --> Decision4{"improvements possible?"}
+    Decision4 -- "no" --> Inform[["Inform appropriate entities"]]
+    Inform --> Step1
+    Decision4 -- "yes" --> Problem3[["Problem identification (Clearances)  
+/*Fig. A-2/E.420*/"]]
+    Problem3 --> Step1
+
+    subgraph RightSide [ ]
+        Start2([ ]) --> Wait["Wait Clearances"]
+        Wait --> Trouble[["Trouble Clearance"]]
+        Trouble --> DecClear["Clearances : = Clearances - 1"]
+        DecClear --> Effective{"Effective rate normal/improved?"}
+        Effective -- "no" --> Problem4[["Problem identification (Clearances)  
+/*Fig. A-2/E.420*/"]]
+        Problem4 --> Wait
+        Effective -- "yes" --> Zero{"Clearances = 0"}
+        Zero -- "no" --> Wait
+        Zero -- "yes" --> End([X])
+    end
+    Problem4 --> End
+    
+```
+
+/\*CLEARING OF POTENTIAL CONDITIONS OF ISOLATION\*/
+
+/\*REVENUE IMPROVEMENT\*/
+
+T0201270-88
+
+Flowchart for PROCESS ResourceAllocation. It starts with DCL Clearances Natural : = 0; and branches into two main paths: one for clearing isolation conditions and another for revenue improvement. The isolation path checks for destinations with unweighted ABR < exception threshold, then checks if any more are found. If not, it checks if the destination is isolated. If isolated, it checks if improvements are possible. If not possible, it informs entities. If possible, it identifies problems. The revenue path calculates destination priorities and chooses the highest priority destination, then checks if further resource commitment is justified. If not justified, it identifies problems. The right side of the diagram shows a sub-process for 'Wait Clearances', 'Trouble Clearance', and 'Clearances : = Clearances - 1', followed by a decision 'Effective rate normal/improved?'. If not normal/improved, it identifies problems. If normal/improved, it checks if 'Clearances = 0'. If not zero, it loops back to 'Wait Clearances'. If zero, it ends. Annotations include /\*1)\*/ through /\*6)\*/ and references to Fig. A-2/E.420. A label T0201270-88 is at the bottom right.
+
+FIGURE A-1/E.420  
+Process resource allocation
+
+Problemidentification
+
+![Flowchart of the problem identification procedure.](1956f44611abd5c3c41049836aa78ad8_img.jpg)
+
+```
+
+    graph TD
+    Start([ ]) --> D1{Is detailed data available for analysis?}
+    D1 --|no| P1["Make arrangements to get detailed data e.g.  
+— Recommendation E.422  
+— destination code analysis  
+— daily profile"]
+    P1 --> D2
+    D1 --|yes| D2{Is there a shift in ineffective call categories compared to historical data?}
+    D2 --|no| D4
+    D2 --|yes| C1((Analysis))
+    C1 --> D3{Does data analysis identify a possible trouble?}
+    D3 --|no| D4{Are data sources considered adequate for trouble identification?}
+    D4 --|no| P2["Consult with other Administrations for possible trouble identification"]
+    P2 --> C2((Pos. Trouble Id))
+    D4 --|yes| P3["Continue data collection, a larger sample may be required for analysis"]
+    P3 --> C3((Analyze))
+    D3 --|yes| C4((Pos. Trouble Id))
+    C4 --> D5{Does trouble appear to be a network malfunction?}
+    D5 --|no| C5((No Mal-function))
+    C5 --> P3
+    D5 --|yes| P4["preliminary investigation"]
+    P4 --> D6{Does a malfunction exist?}
+    D6 --|no| C6((No Mal-function))
+    C6 --> P5["Clearances := Clearances + 1"]
+    P5 --> P6[Locate and correct malfunction]
+    P6 --> End1((X))
+    D6 --|yes| P6
+    D5 --> P7[QOS Improvement]
+    P7 --> End2((X))
+  
+```
+
+Flowchart of the problem identification procedure.
+
+/\*7)  
+Detailed  
+Analysis\*/
+
+"Is detailed  
+data available  
+for analysis?"
+
+"no"
+
+"Make arrangements to get  
+detailed data e.g.  
+— Recommendation E.422  
+— destination code analysis  
+— daily profile"
+
+"yes"
+
+"Is there a shift  
+in ineffective call  
+categories compared  
+to historical data?"
+
+"no"
+
+Analysis
+
+"yes"
+
+Pos-  
+Trouble  
+Id
+
+"yes"
+
+"Does data analysis  
+identify a possible  
+trouble?"
+
+"no"
+
+/\*9)\*/
+
+"yes"
+
+"Does trouble appear  
+to be a network  
+malfunction?"
+
+"yes"
+
+"Are data sources  
+considered adequate  
+for trouble  
+identification?"
+
+"no"
+
+"preliminary  
+investigation"
+
+/\*10)\*/
+
+"Does  
+a malfunction  
+exist?"
+
+No  
+Mal-  
+function
+
+"no"
+
+No  
+Mal-  
+function
+
+"Continue data  
+collection, a larger  
+sample may be required  
+for analysis"
+
+"Consult with other  
+Administrations  
+for possible trouble  
+identification"
+
+Clearances : =  
+Clearances + 1
+
+/\*9) 10)\*/
+
+/\*8)\*/
+
+Analyze
+
+Pos.  
+Trouble  
+Id
+
+Locate and correct  
+malfunction
+
+QOS Improvement
+
+T0201280-88
+
+FIGURE A-2/E.420
+
+Problem identification procedure
+
+**Fascicle II.3 - Rec. E.420**
+
+5
+
+(to Recommendation E.420)
+
+### Utilization of customer complaints to improve the quality of service for international traffic
+
+It is possible to use subscriber complaints to control processes if the organization of an Administration provides possibilities for centralized collection of these complaints.
+
+The collected data can be processed statistically to provide useful indications for the operations and maintenance staff to correct problems and, in so doing, improve the quality of service.
+
+Three aspects are relevant in the processing of the data:
+
+- the data itself;
+- the statistical processes;
+- the analysis of complaints.
+
+#### B.1 *Data to be collected*
+
+The trouble report of an individual customer may be subjective and unqualified since it is usually made by a person, who is not well trained for observation of quality of service. Therefore it will be necessary to make sure that the information about the complaint is as reliable as possible and useful for identifying the possible impairment of the network that caused the complaint.
+
+Examples (see also the handbook cited in [1]):
+
+- data concerning the subscriber numbers involved (route, destination);
+- data concerning the observations during the unsuccessful call attempt(s), or the disturbed call;
+- time of the observation by the customer.
+
+#### B.2 *Statistical processes to improve the reliability of the data*
+
+Reliable data is obtained by statistical processing of large numbers of complaints (e.g. an average value during a certain period of time). In order to achieve this, the following methods are considered to be useful:
+
+- 1) choose complaints whose possible causes seem to relate to *impairments* of the network;
+- 2) *accumulate* complaints for a certain period of time, for example, one month or one week, depending on the number of complaints;
+- 3) calculate the *ratio of complaints statistically* from accumulated data, for example, *complaint-to-completion ratio (CTCR)*, for the chosen period of time:
+
+$$\text{CTCR} = \frac{\text{Number of complaints}}{\text{Number of effective call attempts}} \times 100\%$$
+
+It is practical to use the CTCR in combination with one or more classification aspects (see § B.3) such as "per destination".
+
+#### B.3 *Analysis of complaints*
+
+It is necessary to identify the possible impairment of the network causing the complaint and smoothly clear this impairment in order to actually improve the quality of service. To accomplish this, the complaint needs to be processed into data useful to network maintenance organizations in localizing the possible impairment. The following methods are considered useful:
+
+- 1) classifying complaints by category of failure;
+- 2) classifying complaints by destination, route (or circuit group) and/or area code;
+
+- 3) time of day analysis. This may be effective in identifying impairments that may not be apparent when looked at on a total day basis;
+- 4) highlighting relative changes or trends in the statistical data. These changes are likely to reflect a change of the network status and are useful indications along with the values themselves. For example, a rapid increase in the statistical value (e.g. the ratio of complaints) may reflect a new impairment of the network.
+
+## **Reference**
+
+- [1] CCITT Manual *Quality of service, network management and network maintenance*, ITU, Geneva, 1984.

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+
+
+![ITU logo](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg)
+
+The logo of the International Telecommunication Union (ITU) features the letters 'ITU' in a bold, sans-serif font, superimposed on a stylized globe with intersecting lines.
+
+ITU logo
+
+INTERNATIONAL TELECOMMUNICATION UNION
+
+**ITU-T**
+
+**E.421**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+**TELEPHONE NETWORK AND ISDN**
+
+**QUALITY OF SERVICE, NETWORK MANAGEMENT  
+AND TRAFFIC ENGINEERING**
+
+---
+
+**SERVICE QUALITY OBSERVATIONS  
+ON A STATISTICAL BASIS**
+
+**ITU-T Recommendation E.421**
+
+(Extract from the *Blue Book*)
+
+---
+
+# NOTES
+
+1 ITU-T Recommendation E.421 was published in Fascicle II.3 of the *Blue Book*. This file is an extract from the *Blue Book*. While the presentation and layout of the text might be slightly different from the *Blue Book* version, the contents of the file are identical to the *Blue Book* version and copyright conditions remain unchanged (see below).
+
+2 In this Recommendation, the expression “Administration” is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+# **SERVICE QUALITY OBSERVATIONS ON A STATISTICAL BASIS**
+
+## **1 Definitions**
+
+### **1.1 service observation**
+
+*F: observation de la qualité de service*
+
+*S: observación de la calidad del servicio*
+
+Monitoring to obtain a complete or partial assessment of the quality of telephone calls, excluding test calls.
+
+### **1.2 manual observation**
+
+*F: observation manuelle*
+
+*S: observación manual*
+
+Monitoring of telephone calls by an observer without using any automatic data-recording machine.
+
+### **1.3 automatic observation**
+
+*F: observation automatique*
+
+*S: observación automática*
+
+Monitoring of telephone calls without an observer.
+
+### **1.4 semi-automatic observation**
+
+*F: observation semi-automatique*
+
+*S: observación semiautomática*
+
+Monitoring of telephone calls using equipment which records some data automatically. For example, equipment in which information, such as exchange being observed, number dialled by the subscriber, metering pulses and time of call, is recorded automatically on some means suitable for data processing. The observer merely has to key in a code indicating the condition observed.
+
+## **2 Relative merits of manual, automatic and semi-automatic observations**
+
+2.1 The three methods mentioned above in §§ 1.2, 1.3 and 1.4 are not exclusive; for example, automatic observations may be used to supplement observations taken by an operator. It was considered in 1968 that the need for automatic observations would increase in view of the heavy cost associated with manual or semiautomatic observations on the rapidly expanding international network. It was also considered that automatic observations would not entirely supersede observations taken by an observer within the foreseeable future.
+
+The relative merits of the three methods can be assessed as follows:
+
+### **2.2 Manual observation**
+
+Provides all the data required in Tables 1/E.422 and 1/E.423.
+
+Observations can be carried out with a minimum of equipment.
+
+Observations can permit the detection of a number of abnormalities which cannot be detected automatically, e.g. very poor speech transmission (item 5.2 of Table 1/E.422), or difficulty with audible tones encountered in the international service (item 6.4 of Table 1/E.422).
+
+### **2.3 Semi-automatic observation**
+
+Provides all the data required in Tables 1/E.422 and 1/E.423.
+
+There is a saving in staffing costs compared with manual observation.
+
+Greater accuracy compared with manual observation is possible due to the fact that there is an automatic recording of the number dialled, the time of the call, etc.
+
+It is possible for the observer to devote greater attention to the more critical conditions being checked during observations of calls.
+
+The results are produced in a form suitable for subsequent mechanized analysis.
+
+Owing to the reduction of costs it is possible to obtain a larger sample for the same expenditure.
+
+Semi-automatic equipment may be converted, during certain hours of the day, to automatic operation.
+
+### 2.4 *Automatic observation*
+
+Operating cost is minimum (staff reduction).
+
+Continuous observation is possible.
+
+It is possible to have a larger sample.
+
+Human error is eliminated.
+
+Automatic processing of data is facilitated.
+
+Conversational privacy is ensured.
+
+Control of the time at which observations are made is facilitated.
+
+Some of the differences between internal and external automatic observations are given below:
+
+2.4.1 Internal automatic observations can be made in the switching centre itself, on the incoming side or the outgoing side or in between, according to the way the switching centre is engineered:
+
+- a) Only line signals, such as seizure, answer, etc. can be monitored, and also register signals as long as they do not pass through the exchange in an end-to-end signalling procedure.
+- b) Signals received are only monitored if the exchange itself operates correctly in that respect.
+- c) Item b) applies also to outgoing signals. If there is a fault in the exchange it can happen that signals have not been sent in the appropriate way without the exchange being aware of it.
+
+More information on this type of observation technique is given in Recommendation E.425.
+
+2.4.2 External automatic observations are made by means of monitoring equipment which is supervising the traffic on incoming or outgoing lines:
+
+- All signalling signals can be monitored.
+- The detection of tones, speech and data is possible if advanced equipment is used.
+- This observation technique provides all the data required in Table 2/E.422 and Table 2/E.423.
+- The application is very flexible and can be used instead of manual or semi-automatic observation techniques.
+
+## 3 Time of observations
+
+The results of all observations taken over the whole day should be recorded in Table 1/E.422 or Table 2/E.422.
+
+In the case where observations are not taken over the whole day the observation period is recorded under the heading "Time of observations" and should include the three busiest hours of the day.
+
+## 4 Observation access points
+
+4.1 Observations for Table 1/E.422 or Table 2/E.422 should be carried out from access points as close as possible to the outgoing international exchange.
+
+The following access points can be considered:
+
+- i) outgoing relay set of an international circuit ("exchange" side), i.e. *international circuit access point*<sup>1)</sup>;
+- ii) incoming relay set of a national circuit;
+- iii) link circuits of the international exchange.
+
+Observations will be made only while the call is being set up, and a few seconds after the called subscriber's reply.
+
+When the circuit access point<sup>1)</sup> is used for observation of international calls it is possible that the service quality of the international exchange may not be checked by either international or national observation programmes.
+
+Preferably, and where technically feasible for the most complete results, observations for Table 1/E.422 should be carried out as close as possible to the international exchange on the national side. This would be more representative of service to the subscriber, and allows observation of call failure at the outgoing international exchange. Where it is not possible to make the distinction between failures in the outgoing international exchange, and failures beyond this exchange, or where there is a meaningful advantage in doing so, observations should be taken on the outgoing side.
+
+It is necessary to state in Table 1/E.422 or Table 2/E.422 the access point where the observations have been made, as observations obtained at each one of the three access points mentioned above are not comparable.
+
+4.2 Observations for Table 1/E.423 must be carried out from access points on the operators' positions.
+
+## 5 Number of observations
+
+5.1 Service observing programmes should be established in such a manner that statistical results obtained be as reliable as practicable bearing in mind the cost of obtaining large samples.
+
+5.2 According to the studies carried out by the CCITT in 1964-1968, the quantities shown below are considered the *minimum* quantities to provide a general indication of the quality of service.
+
+### 5.2.1 Table 1/E.422
+
+The minimum number of observations per outgoing circuit group for Table 1/E.422 should be 200 per month when more than 20 circuits are included in a group, 200 per quarter when there are between 10 and 20 circuits in a group and 200 per year if there are less than 10 circuits in a group.
+
+### 5.2.2 Table 1/E.423
+
+The minimum number of observations for Table 1/E.423 should be 200 per quarter when there are more than 20 circuits in the group, 200 per semester when there are between 10 and 20 circuits and 200 per year when there are less than 10 circuits in the group.
+
+### 5.2.3 Transit traffic
+
+Where an outgoing circuit group also carries transit traffic it is desirable to obtain data for each destination country reached via this circuit group. In principle, the number of observations for each destination should be obtained as indicated above. To accomplish this, one should use for each destination country its corresponding number of erlangs and derive from these erlangs a theoretical number of circuits.
+
+However, where only a very small amount of traffic is handled, e.g. less than 5 erlangs, each Administration may wish either to make a smaller number of observations or (e.g. in case of no complaints) no observations at all and rely on the information obtained at the transit exchange.
+
+5.3 The number of observations specified above will provide a general indication of results on quality of service in certain broad categories. Administrations may desire more accurate results especially for the individual categories in Table 1/E.422.
+
+Attention is drawn to Table 1/E.421 which gives the number of observations required to obtain a certain degree of accuracy.
+
+---
+
+<sup>1)</sup> For definitions of test access points see Recommendation M.700. See also Recommendation M.110.
+
+TABLE 1/E.421
+
+| Expected percentage rate of failure | Number of observations of a random sample required to predict with 95% confidence the true percentage of failure with an accuracy of: |            |            |            |            |            |
+|-------------------------------------|---------------------------------------------------------------------------------------------------------------------------------------|------------|------------|------------|------------|------------|
+|                                     | $\pm 25\%$                                                                                                                            | $\pm 30\%$ | $\pm 35\%$ | $\pm 40\%$ | $\pm 45\%$ | $\pm 50\%$ |
+| 2                                   | 3136                                                                                                                                  | 2178       | 1600       | 1225       | 1030       | 880        |
+| 4                                   | 1536                                                                                                                                  | 1067       | 784        | 600        | 500        | 440        |
+| 6                                   | 1003                                                                                                                                  | 696        | 512        | 392        | 330        | 290        |
+| 8                                   | 736                                                                                                                                   | 511        | 376        | 288        | 245        | 215        |
+| 10                                  | 576                                                                                                                                   | 400        | 294        | 225        | 195        | 170        |
+| 12                                  | 469                                                                                                                                   | 326        | 239        | 183        | 150        | 132        |
+| 14                                  | 393                                                                                                                                   | 273        | 201        | 154        | 128        | 112        |
+| 16                                  | 336                                                                                                                                   | 233        | 171        | 131        | 112        | 98         |
+| 18                                  | 292                                                                                                                                   | 202        | 149        | 114        | 95         | 80         |
+| 20                                  | 256                                                                                                                                   | 178        | 131        | 100        | 85         | 70         |
+| 30                                  | 149                                                                                                                                   | 104        | 76         | 60         | 50         | 42         |
+| 40                                  | 96                                                                                                                                    | 67         | 50         | 38         | 30         | 24         |
+| 50                                  | 64                                                                                                                                    | 44         | 33         | 25         | 20         | 16         |
+
+Annex to Table 1/E.421
+
+#### *Examples of use of Table 1/E.421*
+
+*Example 1* – It is estimated from previous results that a particular type of failure occurs on about 4% of calls. If it is required to confirm, with 95% confidence, that the existing failure rate is between 3% and 5% (i.e.  $\pm 25\%$  of 4%), then observations must be made on a random sample of 1536 calls.
+
+*Example 2* – For an expected failure rate of 2%, observations must be made on a random sample of about 1200 calls (1225 in the table) to predict, with 95% confidence, that the true percentage is between 1.2% and 2.8% (i.e.  $\pm 40\%$  of 2%). This means that when 200 observations are taken over a period it is necessary to take the "rolling average" of conditions over six periods. The rate of failure for a number of categories important from the maintenance point of view is expected to be about 2%.
+
+*Example 3* – After observations have been taken and the rate of failure in the sample has been calculated, the table may be used in a "backward" direction to give a rough indication of the accuracy of the result.
+
+Suppose that out of a sample of 1000 observations, there were 29 failures due to cause "X" and 15 failures due to cause "Y". The rates of failure in the sample due to X and Y, respectively, are then 2.9% and 1.5%. From the table, it is apparent from this sample of 1000 calls that the true rate of failure due to X has an accuracy of about  $\pm 35\%$  (i.e. is between 1.9% and 3.9%), and that due to Y has an accuracy of about  $\pm 50\%$  (i.e. is between 0.8% and 2.3%).
+
+## 6 Exchange and analysis of the results of observations
+
+### 6.1 *Exchange of the results of observations*
+
+The following periodicities are proposed for the exchange of results between Administrations:
+
+Table 1/E.422 or Table 2/E.422 – a monthly exchange is desirable;
+
+Table 1/E.423 or Table 2/E.423 – a quarterly exchange is desirable.
+
+Nevertheless, in the case of small groups of circuits (less than 20 circuits) the information should be exchanged after 200 observations have been made but never later than one year in any case; attention is drawn to the fact that less than 200 observations are of little value.
+
+Results of observations will be reported without delay:
+
+- to the Administrations and the network analysis point of the country where observations are carried out;
+- to the Administrations and the network analysis point of the other country (including transit Administrations and their network analysis point when involved).
+
+The benefits to be derived from service observations tend to decrease if there is any increase in the time taken to make the results available to those who can take action to bring about an improvement. The results of service observations according to Tables 1/E.422 and 1/E.423 should therefore be made available to the Administration in the countries of destination as soon as possible after completion of the observation period and in any case within six weeks.
+
+### 6.2 *Analysis of observation results*
+
+An analysis of the results should be carried out in the country of origin as well as in the country of destination.
+
+Some Administrations have found it useful to distribute to other Administrations concerned, service observation statistics in the form of graphs.

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+
+
+![ITU logo: A globe with a lightning bolt and the letters ITU.](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg)
+
+ITU logo: A globe with a lightning bolt and the letters ITU.
+
+INTERNATIONAL TELECOMMUNICATION UNION
+
+**CCITT**
+
+**E.430**
+
+THE INTERNATIONAL  
+TELEGRAPH AND TELEPHONE  
+CONSULTATIVE COMMITTEE
+
+**TELEPHONE NETWORK AND ISDN**
+
+**QUALITY OF SERVICE,  
+NETWORK MANAGEMENT AND TRAFFIC  
+ENGINEERING**
+
+---
+
+**QUALITY OF SERVICE FRAMEWORK**
+
+**Recommendation E.430**
+
+---
+
+![CCITT logo: A globe with the letters CCITT.](84a1d09fb489061482111515543b60dc_img.jpg)
+
+CCITT logo: A globe with the letters CCITT.
+
+Geneva, 1992
+
+# FOREWORD
+
+The CCITT (the International Telegraph and Telephone Consultative Committee) is a permanent organ of the International Telecommunication Union (ITU). CCITT is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis.
+
+The Plenary Assembly of CCITT which meets every four years, establishes the topics for study and approves Recommendations prepared by its Study Groups. The approval of Recommendations by the members of CCITT between Plenary Assemblies is covered by the procedure laid down in CCITT Resolution No. 2 (Melbourne, 1988).
+
+Recommendation E.430 was prepared by Study Group II and was approved under the Resolution No. 2 procedure on the 16th of June 1992.
+
+# --- CCITT NOTE
+
+In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication Administration and a recognized private operating agency.
+
+# **QUALITY OF SERVICE FRAMEWORK**
+
+# **1 Introduction**
+
+A typical user is not interested in how a particular service is implemented, but he is interested in comparing one service with another in terms of certain universal performance parameters which apply to any service. Quality of Service (QOS) is expressed by parameter which:
+
+- do not depend on assumptions about the network internal design;
+- are referred to in terms of user-perceivable effects and not by their causes in the network;
+- are described in network independent terms and create a common language understandable by both the user and the provider;
+- take into account all aspects of the service which can be objectively measured at the service access point.
+
+A network provider is concerned with the efficiency and effectiveness of the network. From the network providers point of view, network performance is best expressed by parameters which give information for:
+
+- system development;
+- network planning;
+- operation and maintenance.
+
+The user orientated QOS parameters provide a valuable framework for network design, but they are not necessarily usable in specifying network performance requirements for particular connections.
+
+Similarly, the network performance (NP) parameters primarily determine the Quality of Service, but they do not, necessarily, describe that quality in a way that is meaningful to users.
+
+Both types of parameters are needed, and their values must be related if a network is to be effective in serving its users. The definition of QOS and NP parameters should make mapping of values clear in cases where there is not a simple one-to-one relationship between them.
+
+# **2 Purpose**
+
+It is recognised that NP parameters make a major contribution to the QOS. The purpose of this Recommendation is to identify a relationship between Quality of Service (QOS) and network performance (NP) parameters.
+
+# **3 Scope**
+
+This Recommendation covers the technical performance of a connection. For compatibility and completeness, Quality of Service aspects are considered in the form of a high level  $3 \times 3$  matrix.
+
+# **4 Matrix**
+
+A matrix has been designed to enable cross correlation between QOS parameters and relevant QOS and NP Recommendations covering all aspects of telecommunications.
+
+The matrix forms the prime structure for identifying all QOS sources and relationships, relevant to network performance.
+
+The intention is that, by cross-relating the appropriate general identifiers, it will be possible to source the required detailed parameter.
+
+The performance parameters are classified according to the three basic communication functions; access, user information transfer and disengagement, and are described according to speed, accuracy and dependability criteria.
+
+Speed is the time-related criterion used to describe the function performance.
+
+Accuracy is the criterion that describes the degree of correctness with which the function is performed.
+
+Dependability is the performance criterion that describes the degree of certainty (or surety) with which a function is performed regardless of speed or accuracy, but within a given observation interval (from Recommendation I.350).
+
+| Criterion/Function                    | Speed               | Accuracy                           | Dependability               |
+|---------------------------------------|---------------------|------------------------------------|-----------------------------|
+| Connection set-up<br>(access)         | E.431<br>See List A | E.845 (Rev.1)<br>See List B        | E.845, E.846<br>See List C  |
+| User information transfer             | E.432<br>See List D | E.432, E.855 (Rev.1)<br>See List E | E.850 (Rev.1)<br>See List F |
+| Connection disengagement<br>(release) | E.431<br>See List G | See List H                         | See List I                  |
+
+FIGURE 1/E.430  
+**High-level 3 × 3 matrix**
+
+TABLE 1/E.430  
+**Recommendations related the entries of the  $3 \times 3$  matrix**
+
+| List A | List B        | List C         |
+|--------|---------------|----------------|
+| E.431  | E.845 (Rev.1) | E.845<br>E.846 |
+| X.135  | X.136         | X.136          |
+| I.352  | I.352         | I.352          |
+| E.422  | E.422         |                |
+| E.427  | E.424         |                |
+| E.721  | E.425         |                |
+|        | E.426         |                |
+|        | E.427         |                |
+| List D | List E        | List F         |
+| E.432  | G.821         | E.850 (Rev.1)  |
+| X.135  | G.82x         | X.136          |
+|        | E.422         |                |
+|        | E.424         |                |
+| I.35B  | E.432         | I.35C          |
+| I.35C  | E.855 (Rev.1) | I.35P          |
+| I.35P  | X.136         | I.35B          |
+|        | I.35B         | E.428          |
+|        | I.35P         |                |
+| List G | List H        | List I         |
+| E.431  |               |                |
+| X.135  | X.136         | X.136          |
+| I.352  | I.352         | I.352          |
+| E.721  |               |                |

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+
+
+![ITU logo: A globe with a lightning bolt and the letters ITU.](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg)
+
+ITU logo: A globe with a lightning bolt and the letters ITU.
+
+INTERNATIONAL TELECOMMUNICATION UNION
+
+**ITU-T**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+**E.438**
+
+(03/2000)
+
+SERIES E: OVERALL NETWORK OPERATION,  
+TELEPHONE SERVICE, SERVICE OPERATION AND  
+HUMAN FACTORS
+
+Quality of service, network management and traffic  
+engineering – Network management – Checking the  
+quality of the international telephone service
+
+---
+
+**Performance parameters and measurement  
+methods to assess N-ISDN 64 kbit/s circuit-  
+switched bearer service UDI in operation**
+
+ITU-T Recommendation E.438
+
+(Formerly CCITT Recommendation)
+
+---
+
+# ITU-T E-SERIES RECOMMENDATIONS **OVERALL NETWORK OPERATION, TELEPHONE SERVICE, SERVICE OPERATION AND HUMAN FACTORS**
+
+## **OPERATION, NUMBERING, ROUTING AND MOBILE SERVICES**
+
+## **INTERNATIONAL OPERATION**
+
+|                                                        |             |
+|--------------------------------------------------------|-------------|
+| Definitions                                            | E.100–E.103 |
+| General provisions concerning Administrations          | E.104–E.119 |
+| General provisions concerning users                    | E.120–E.139 |
+| Operation of international telephone services          | E.140–E.159 |
+| Numbering plan of the international telephone service  | E.160–E.169 |
+| International routing plan                             | E.170–E.179 |
+| Tones in national signalling systems                   | E.180–E.189 |
+| Numbering plan of the international telephone service  | E.190–E.199 |
+| Maritime mobile service and public land mobile service | E.200–E.229 |
+
+## **OPERATIONAL PROVISIONS RELATING TO CHARGING AND ACCOUNTING IN THE INTERNATIONAL TELEPHONE SERVICE**
+
+|                                                                |             |
+|----------------------------------------------------------------|-------------|
+| Charging in the international telephone service                | E.230–E.249 |
+| Measuring and recording call durations for accounting purposes | E.260–E.269 |
+
+## **UTILIZATION OF THE INTERNATIONAL TELEPHONE NETWORK FOR NON-TELEPHONY APPLICATIONS**
+
+|                 |             |
+|-----------------|-------------|
+| General         | E.300–E.319 |
+| Phototelegraphy | E.320–E.329 |
+
+## **ISDN PROVISIONS CONCERNING USERS**
+
+|                            |             |
+|----------------------------|-------------|
+| International routing plan | E.350–E.399 |
+|----------------------------|-------------|
+
+## **QUALITY OF SERVICE, NETWORK MANAGEMENT AND TRAFFIC ENGINEERING**
+
+## **NETWORK MANAGEMENT**
+
+|                                  |             |
+|----------------------------------|-------------|
+| International service statistics | E.400–E.409 |
+| International network management | E.410–E.419 |
+
+### | | | |--------------------------------------------------------------------|--------------------| | <b>Checking the quality of the international telephone service</b> | <b>E.420–E.489</b> | |--------------------------------------------------------------------|--------------------|
+
+## **TRAFFIC ENGINEERING**
+
+|                                                                                   |             |
+|-----------------------------------------------------------------------------------|-------------|
+| Measurement and recording of traffic                                              | E.490–E.505 |
+| Forecasting of traffic                                                            | E.506–E.509 |
+| Determination of the number of circuits in manual operation                       | E.510–E.519 |
+| Determination of the number of circuits in automatic and semi-automatic operation | E.520–E.539 |
+| Grade of service                                                                  | E.540–E.599 |
+| Definitions                                                                       | E.600–E.699 |
+| ISDN traffic engineering                                                          | E.700–E.749 |
+| Mobile network traffic engineering                                                | E.750–E.799 |
+
+## **QUALITY OF TELECOMMUNICATION SERVICES: CONCEPTS, MODELS, OBJECTIVES AND DEPENDABILITY PLANNING**
+
+|                                                                                             |             |
+|---------------------------------------------------------------------------------------------|-------------|
+| Terms and definitions related to the quality of telecommunication services                  | E.800–E.809 |
+| Models for telecommunication services                                                       | E.810–E.844 |
+| Objectives for quality of service and related concepts of telecommunication services        | E.845–E.859 |
+| Use of quality of service objectives for planning of telecommunication networks             | E.860–E.879 |
+| Field data collection and evaluation on the performance of equipment, networks and services | E.880–E.899 |
+
+# **PERFORMANCE PARAMETERS AND MEASUREMENT METHODS TO ASSESS N-ISDN 64 kbit/s CIRCUIT-SWITCHED BEARER SERVICE UDI IN OPERATION**
+
+## **Summary**
+
+This Recommendation presents an overview of performance parameters for the measurement and assessment of N-ISDN 64 kbit/s circuit switched UDI bearer services in operation. Guidelines and considerations for measurement methods are also provided. These parameters can be used for N-ISDN monitoring and improvement in operations. Their achieved values can be used both to establish guaranteed performance levels in Service Level Agreement with the customers and Service Quality Agreement with other administrations, and to verify, analyse and improve the performance level currently offered.
+
+###### **Source**
+
+ITU-T Recommendation E.438 was prepared by ITU-T Study Group 2 (1997-2000) and was approved under the WTSC Resolution No. 1 procedure on 13 March 2000.
+
+# FOREWORD
+
+ITU (International Telecommunication Union) is the United Nations Specialized Agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the ITU. The ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis.
+
+The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics.
+
+The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Resolution No. 1.
+
+In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC.
+
+## NOTE
+
+In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+## INTELLECTUAL PROPERTY RIGHTS
+
+The ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. The ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process.
+
+As of the date of approval of this Recommendation, the ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database.
+
+© ITU 2001
+
+All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU.
+
+## CONTENTS
+
+###### Page
+
+|       |                                                                                           |   |
+|-------|-------------------------------------------------------------------------------------------|---|
+| 1     | Introduction.....                                                                         | 1 |
+| 2     | Scope.....                                                                                | 1 |
+| 3     | References.....                                                                           | 2 |
+| 4     | Terms and definitions .....                                                               | 3 |
+| 5     | Abbreviations and acronyms.....                                                           | 4 |
+| 6     | ISDN CSCT NP/QOS parameters .....                                                         | 4 |
+| 7     | Measurement methods for ISDN CSCT NP/QOS parameters.....                                  | 5 |
+| 7.1   | Measurement methods applicable.....                                                       | 6 |
+| 7.2   | Comparison of three measurement methods in terms of measurable performance parameter..... | 6 |
+| 7.3   | Characteristics of each measurement method.....                                           | 7 |
+| 7.3.1 | Test call based measurement .....                                                         | 7 |
+| 7.3.2 | CDR based measurement.....                                                                | 7 |
+| 7.3.3 | INMD based measurement .....                                                              | 7 |
+
+# Introduction
+
+ISDN traffic is growing because it allows faster access to and use of advanced services (such as Internet access, videocommunication, etc.) than traditional PSTN networks. ISDN networks are completely defined by ITU-T in terms of architecture, features, access interfaces, transport and signalling protocols, interworking functionality and basic and supplementary services. Recommendation E.721 gives good guidance for planning and designing ISDN networks with adequate GOS levels. Recommendation M.3650 covers maintenance performance related aspects of ISDN. Operations related ISDN NP/QOS aspects, however, are spread among many specific ITU-T Recommendations, some of which only partially cover performance parameters, events and methods for their measurement. This Recommendation attempts to give a complete and organic overview of ISDN NP/QOS parameters and related measurement methods to be used in operations for monitoring and improvement purposes.
+
+The measures, identified according to the methodological approach described in ITU-T Recommendations I.350 [6] and E.820 [4], are defined in clause 6. Additional definitions are given in clause 4. The ISDN NP/QOS parameters can be collected and measured by Administrations in accordance with the measurement methods described in clause 7.
+
+# **PERFORMANCE PARAMETERS AND MEASUREMENT METHODS TO ASSESS N-ISDN 64 kbit/s CIRCUIT-SWITCHED BEARER SERVICE UDI IN OPERATION**
+
+*(Geneva, 2000)*
+
+## **1 Introduction**
+
+ISDN traffic is growing because it allows faster access to and use of advanced services (such as Internet access, videocommunication, etc.) than traditional PSTN networks. ISDN networks are completely defined by ITU-T in terms of architecture, features, access interfaces, transport and signalling protocols, interworking functionality and basic and supplementary services. Recommendation E.721 gives good guidance for planning and designing ISDN networks with adequate GOS levels. Recommendation M.3650 covers maintenance performance related aspects of ISDN. Operations related ISDN NP/QOS aspects, however, are spread among many specific ITU Recommendations, some of which only partially cover performance parameters, events and methods for their measurement. This Recommendation attempts to give a complete and organic overview of ISDN NP/QOS parameters and related measurements methods to be used in operations for monitoring and improvement purposes.
+
+The measures, identified according to the methodological approach described in ITU-T Recommendations I.350 [6] and E.820 [4], are defined in clause 6 of this Recommendation. Additional definitions are given in clause 4. The ISDN NP/QOS parameters can be collected and measured by administrations in accordance with the measurement methods described in clause 7.
+
+## **2 Scope**
+
+The main aim of this Recommendation is to give complete guidance for the characterization and assessment, in operation, of the performance of bearer CSCT 64 kbit/s UDI ISDN services by a set of operational NP/QOS measures, related to all the main functions/phases of an ISDN call (setup, information transfer, release). The values measured for these parameters are mainly used for Operation, but also for Administration and Maintenance (OAM) purposes, and for managing Service Level Agreements (SLAs) and Service Quality Agreements (SQAs) [21] with customers and other ROAs.
+
+To pursue this aim, this Recommendation:
+
+- identifies the main ISDN NP/QOS parameters for assessing the serveability and integrity of 64 kbit/s based circuit switched ISDN connections and networks. References to E-, G-, I-, M-, O-, P- and Q-series Recommendations for NP/QOS parameters definition are provided. Measures are related both to single B-channel and multi B-channel applications using both BRA and PRA accesses.
+- relates these NP/QOS parameters to test call based, CDR-based and INMD-based measurement methods for assessing the connection setup, information transfer and disengagement phases of an ISDN call. Measurability considerations for these ISDN NP/QOS parameters, depending on the measurement method used, are given.
+
+The most of the ISDN performance parameters identified are similar to those already made and used in operation for PSTN. This allows a set of homogeneous measures particularly useful in the case of mixed ISDN ↔ PSTN connections or for comparisons of services between ISDN and PSTN
+
+connections in terms of performance values achieved. However, some performance parameters have been added or modified<sup>1</sup> to those related to PSTN because:
+
+- ISDN connections, up to the network access point (and sometimes up to the service access point) are fully digital.
+- Many services/applications can share the same connection(s).
+- A single service/application communication<sup>2</sup> can involve more than one B-channel/connection.
+- A communication request can be performed both by *en bloc* and by overlap sending.
+- New communication control functions, in addition to those related to the basic telephone call, such as bearer control, compatibility checking, terminal selection, supplementary services control, notify, etc., may be present.
+- Routing can depend on the kind of the bearer service chosen on a per call basis.
+- Measurement can be made at standard user/network interfaces, using enhanced signalling protocols (e.g. DSS1, SS7 etc.).
+
+The assessment of some NP/QOS parameters can also require measurement on B- (information transfer) channels in addition to those taken on D- (signalling) channel.
+
+This Recommendation does not set performance planning objectives – these are mainly defined in [5] – but rather describes means by which actual NP can be assessed. The mapping of the measurement made with this Recommendation into parameters reflecting customer opinion is beyond the scope of this Recommendation and is left to the individual ROA.
+
+## 3 References
+
+The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; all users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published.
+
+- [1] ITU-T Recommendation I.112 (1993), *Vocabulary of terms for ISDNs*.
+- [2] ITU-T Recommendation E.600 (1993), *Terms and definitions of traffic engineering*.
+- [3] ITU-T Recommendation E.800 (1994), *Terms and definitions related to quality of service and network performance including dependability*.
+- [4] ITU-T Recommendation E.820 (1992), *Call models for serveability and service integrity performance*.
+- [5] ITU-T Recommendation E.721 (1999), *Network grade of service parameters and target values for circuit-switched services in the evolving ISDN*.
+- [6] ITU-T Recommendation I.350 (1993), *General aspects of quality of service and network performance in digital networks, including ISDNs*.
+
+---
+
+<sup>1</sup> Also some related objective values should be modified according to the media (voice, data, video) or the teleservice used in the call, even if they are not included in this Recommendation.
+
+<sup>2</sup> With the term call, according to the ITU-T Recommendation E.600 [2], we intend a teleservice/application request that can involve in case of multi-channel call more than one bearer service/ network connection. For simplicity, we consider here multi-channel teleservices/applications using only 64 kbit/s UDI bearer service.
+
+- [7] ITU-T Recommendation I.352 (1993), *Network performance objectives for connection processing delays in an ISDN.*
+- [8] ITU-T Recommendation I.353 (1996), *Reference events for defining ISDN and B-ISDN performance parameters.*
+- [9] ITU-T Recommendation I.355 (1995), *ISDN 64 kbit/s connection type availability performance.*
+- [10] ITU-T Recommendation G.114 (1988), *Mean one-way propagation time.*
+- [11] ITU-T Recommendation G.821 (1996), *Error performance of an international digital connection operating at a bit rate below the primary rate and forming part of an integrated services digital network.*
+- [12] ITU-T Recommendation O.152 (1992), *Error performance measuring equipment for bit rates of 64 kbit/s and  $N \times 64$  kbit/s.*
+- [13] ITU-T Recommendation E.846 (1993), *Accessibility for 64 kbit/s circuit-switched international end-to-end ISDN connection types.*
+- [14] ITU-T Recommendation E.425 (1998), *Internal automatic observations.*
+- [15] ITU-T Recommendation E.428 (1992), *Connection retention.*
+- [16] ITU-T Recommendation E.850 (1992), *Connection retainability objective for the international telephone service.*
+- [17] ITU-T Recommendation M.3650 (1997), *Network performance measurements of ISDN calls.*
+- [18] ITU-T Recommendation I.430 (1995), *Basic user-network interface – Layer 1 specification.*
+- [19] ITU-T Recommendation Q.921 (1997), *ISDN user-network interface – Data link layer specification.*
+- [20] ITU-T Recommendation Q.931 (1998), *ISDN user-network interface layer 3 specification for basic call control.*
+- [21] ITU-T Recommendation E.801 (1996), *Framework for Service Quality Agreement.*
+- [22] ITU-T Recommendation P.561 (1996), *In-Service, non-intrusive measurement device – Voice service measurements.*
+- [23] ITU-T Recommendation E.459 (1998), *Measurements and metrics for characterizing facsimile transmission performance using non-intrusive techniques.*
+
+## 4 Terms and definitions
+
+This Recommendations defines the following terms:
+
+**4.1 Differential One-Way Propagation Delay (DOWPD):** It expresses the time difference between the one-way propagation delays (see [10]) measured for each couple of different channels involved in a call.
+
+**4.2 Call Success Ratio (CSR):** Expresses the probability that a call has reached the correct number (i.e. is not misrouted) and starts the transfer of user data on the B-channel.
+
+**4.3 Call Disengagement Failure Ratio (CDFR):** It is an estimate that a release attempt (made by the user or by the network) fails (namely does not release successfully) in disengaging all the resources previously engaged to set up an ISDN connection using a single channel.
+
+NOTE – In case of multi-channel calls ( $N \geq 2$ ) for each measure expressed as a ratio (such as the above CSR, and CDFR parameters), a vector of N values should be obtained. It is also possible to measure the same kind of parameters referring to the multi-channel call, instead to the single channel. In this case, the success and acceptability criteria should be verified simultaneously for all the N-channels involved by the multi-channel call, while it is sufficient that a failure criteria affects at least one of the N-channels to consider the call failed.
+
+## 5 Abbreviations and acronyms
+
+This Recommendation uses the following abbreviations:
+
+|      |                                              |
+|------|----------------------------------------------|
+| BRA  | Basic Rate Access                            |
+| CSCT | Circuit Switched Connection Type             |
+| DSS1 | Digital Subscriber Signalling System No. 1   |
+| INMD | In-service, Non-intrusive Measurement Device |
+| ISDN | Integrated Services Digital Network          |
+| NP   | Network Performance                          |
+| OAM  | Operation Administration and Maintenance     |
+| PRA  | Primary Rate Access                          |
+| QOS  | Quality of Service                           |
+| TE   | Terminal Equipment                           |
+| UDI  | Unrestricted Digital Information             |
+
+## 6 ISDN CSCT NP/QOS parameters
+
+The NP/QOS ISDN parameters are listed in Table 1. They are specified, according to the call phases, in terms of related performance criteria (speed, accuracy, dependability – see [6]) and classified as B (Basic) and O (Optional). The basic parameters, highlighted in bold in Table 1, are those easier to measure and of higher importance for NP/QOS monitoring and improvement in operations. They are normally used in SQA (see [21]) and SLA contracts. Their measurement methods are shown in Table 2. The optional parameters, related to performance aspects of minor importance, may be measured by some administrations for specific operational purposes and in specific contexts to assure a better service level to their customers.
+
+**Table 1/E.438 – ISDN NP/QOS performance parameters and related ITU-T Recommendation references including their definitions**
+
+| NP/QOS measures                            | Perf. Criterion | B/O      | Recs. references for definition |
+|--------------------------------------------|-----------------|----------|---------------------------------|
+| <b>Connection setup Phase</b>              |                 |          |                                 |
+| <b>ABR</b> – Answer Bid Ratio              | <b>D</b>        | <b>B</b> | E.425 [14]                      |
+| <b>ASR</b> – Answer Seizure Ratio          | <b>D</b>        | <b>B</b> | E.425 [14]                      |
+| STA – Short Term Accessibility (Note 3)    | D               | O        | E.846 [13]                      |
+| NAR – Network Accessibility Ratio (Note 4) | D               | O        | E.800 [3]                       |
+| <b>NER</b> – Network Effectiveness Ratio   | <b>D</b>        | <b>B</b> | E.425 [14]                      |
+| <b>CSR</b> – Call Success Ratio            | <b>D</b>        | <b>B</b> | (Note 1)                        |
+
+**Table 1/E.438 – ISDN NP/QOS performance parameters and related ITU-T Recommendation references including their definitions (concluded)**
+
+| NP/QOS measures                                                                                                                                                                                                                                                                                         | Perf. Criterion | B/O      | Recs. references for definition |
+|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------------|----------|---------------------------------|
+| <b>MCED</b> – Mean Call Establishment Delay                                                                                                                                                                                                                                                             | <b>S</b>        | <b>B</b> | I.352 [7]                       |
+| <b>PRSD</b> – PRe-Selection Delay                                                                                                                                                                                                                                                                       | <b>S</b>        | <b>O</b> | E.721 [5]                       |
+| <b>PSD</b> – Post-Selection Delay (Note 5)                                                                                                                                                                                                                                                              | <b>S</b>        | <b>O</b> | E.721 [5]                       |
+| <b>MR</b> – Misrouting Ratio (Note 6)                                                                                                                                                                                                                                                                   | <b>D</b>        | <b>O</b> | E.800 [3]                       |
+| <b>Connection information transfer phase</b>                                                                                                                                                                                                                                                            |                 |          |                                 |
+| <b>MOWPD</b> – Mean One-Way Propagation Delay                                                                                                                                                                                                                                                           | <b>S</b>        | <b>B</b> | G.114 [10]                      |
+| <b>MDOWPD</b> – Mean differential OWPD (Note 7)                                                                                                                                                                                                                                                         | <b>S</b>        | <b>B</b> | (Note 1)                        |
+| <b>MES</b> – Mean Errored Seconds                                                                                                                                                                                                                                                                       | <b>A</b>        | <b>B</b> | G.821 [11]                      |
+| <b>MSES</b> – Mean Severely Errored Seconds                                                                                                                                                                                                                                                             | <b>A</b>        | <b>B</b> | G.821 [11]                      |
+| <b>PRR</b> – Premature Release Ratio                                                                                                                                                                                                                                                                    | <b>D</b>        | <b>B</b> | E.428 [15], E.850 [16]          |
+| <b>Connection disengagement phase</b>                                                                                                                                                                                                                                                                   |                 |          |                                 |
+| <b>CDFR</b> – Call Disengagement Failure Ratio (Note 8)                                                                                                                                                                                                                                                 | <b>D</b>        | <b>B</b> | (Note 1)                        |
+| <b>MCDD</b> – Mean Call Disengagement Delay (Note 9)                                                                                                                                                                                                                                                    | <b>S</b>        | <b>B</b> | I.352 [7]                       |
+| <b>A</b> <b>Accuracy</b>                                                                                                                                                                                                                                                                                |                 |          |                                 |
+| <b>B</b> <b>Basic</b>                                                                                                                                                                                                                                                                                   |                 |          |                                 |
+| <b>D</b> <b>Dependability</b>                                                                                                                                                                                                                                                                           |                 |          |                                 |
+| <b>O</b> Optional                                                                                                                                                                                                                                                                                       |                 |          |                                 |
+| <b>S</b> <b>Speed</b>                                                                                                                                                                                                                                                                                   |                 |          |                                 |
+| NOTE 1 – The definition is contained in clause 4 .                                                                                                                                                                                                                                                      |                 |          |                                 |
+| NOTE 2 – All the delay measures are expressed as mean value, while calls performing effectively during the correspondent phases are expressed in terms of percentages.                                                                                                                                  |                 |          |                                 |
+| NOTE 3 – This parameter is time statistical distribution based.                                                                                                                                                                                                                                         |                 |          |                                 |
+| NOTE 4 – This parameter can be defined as the probability that a user attempting to establish a call receives an indication that the B-channel has been assigned to him. It simply estimates ratio between the seizures and the bids measured in a sample both of test calls and of real traffic calls. |                 |          |                                 |
+| NOTE 5 – Significant for overlap sending calls.                                                                                                                                                                                                                                                         |                 |          |                                 |
+| NOTE 6 – This parameter expresses the probability that a call is misrouted.                                                                                                                                                                                                                             |                 |          |                                 |
+| NOTE 7 – New measure relevant only for multichannel calls.                                                                                                                                                                                                                                              |                 |          |                                 |
+| NOTE 8 – This parameter is important because it influences accessibility performance and revenue generated by traffic.                                                                                                                                                                                  |                 |          |                                 |
+| NOTE 9 – A similar measure, named release delay, is defined in [6].                                                                                                                                                                                                                                     |                 |          |                                 |
+
+## 7      Measurement methods for ISDN CSCT NP/QOS parameters
+
+In this clause measurement methods for the ISDN CSCT NP/QOS basic parameters are defined.
+
+### 7.1 Measurement methods applicable
+
+Three different measurement methods are used for assessing ISDN CSCT NP/QOS parameters:
+
+- Test call based measurements (made at the S/T interface).<sup>3</sup>
+- CDR based measurements (made at the switches).
+- INMD based measurements (made at the S/T interface or at the switches).
+
+### 7.2 Comparison of three measurement methods in terms of measurable performance parameter
+
+In Table 2 below the possible measurement methods used to assess each ISDN CSCT NP/QOS measure, both for single and multiple B-channel applications, are shown.
+
+**Table 2/E.438 – Basic ISDN NP/QOS operational parameters and related measurement methods**
+
+| NP/QOS measures                              | Single B  |            |      | Multiple B |     |      |
+|----------------------------------------------|-----------|------------|------|------------|-----|------|
+|                                              | Test Call | CDR (Note) | INMD | Test Call  | CDR | INMD |
+| <b>Connection Setup Phase</b>                |           |            |      |            |     |      |
+| ABR – Answer Bid Ratio                       | –         | O          | *    | –          | *   | *    |
+| ASR – Answer Seizure Ratio                   | –         | O          | *    | –          | *   | *    |
+| NER – Network Effectiveness Ratio            | O         | O          | *    | O          | *   | *    |
+| CSR – Call Success Ratio                     | O         | –          | *    | O          |     | *    |
+| MCED – Mean Call Establishment Delay         | O         | O          | *    | O          | •   | *    |
+| <b>Connection Information Transfer Phase</b> |           |            |      |            |     |      |
+| MOWPD – Mean One-Way Propagation Delay       | O         | •          | *    | O          | •   | *    |
+| MDOWPD – Mean Differential OWPD              | –         | –          | *    | O          | •   | *    |
+| MES – MeanErrored Seconds                    | O         | •          | *    | O          | •   | *    |
+| MSES – Mean SeverelyErrored Seconds          | O         | •          | *    | O          | •   | *    |
+| PRR – Premature Release Rate                 | O         | •          | *    | O          | •   | *    |
+
+<sup>3</sup> In order to accurately represent network wide performance, large geographically disposed test devices may be required.
+
+**Table 2/E.438 – Basic ISDN NP/QOS operational parameters and related measurement methods (concluded)**
+
+| NP/QOS measures                                                                                                                                                                                                                                                      | Single B  |            |      | Multiple B |     |      |
+|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------|------------|------|------------|-----|------|
+|                                                                                                                                                                                                                                                                      | Test Call | CDR (Note) | INMD | Test Call  | CDR | INMD |
+| <b>Connection Disengagement Phase</b>                                                                                                                                                                                                                                |           |            |      |            |     |      |
+| CDFR – Call Disengagement Failure Ratio                                                                                                                                                                                                                              | O         | O          | *    | O          | •   | *    |
+| MCDD – Mean Call Disengagement Delay                                                                                                                                                                                                                                 | O         | O          | *    | O          | •   | *    |
+| O    Measurable<br>•    Not measurable<br>—    Not applicable<br>*    For further study<br>NOTE – Since CDR/INMD measurement is made at the switching node, the results obtained apply only to the portion of the network between the switch and at the end section. |           |            |      |            |     |      |
+
+### 7.3 Characteristics of each measurement method
+
+#### 7.3.1 Test call based measurement
+
+This method can measure almost all performance parameters. In order to obtain statistically valid NER, CSR, PRR, or CDFR, a sufficient number of test calls should be generated at the S/T interface. With test call measurements, one can also identify problems in any segment of the end-to-end connection by conducting appropriate analysis of the detailed DSS1/SS7 protocol messages.
+
+#### 7.3.2 CDR based measurement
+
+CDR based measurement is suitable to measure ABR, ASR, NER and CDFR based on a large volume of live traffic. It also provides the possibility to measure connection setup delay and connection disengagement delay. However, off-line analysis is required to measure time interval by searching corresponding call detail data. This measurement method is not applicable for measuring performance parameters in information transfer phase and performances of multi-channel calls.
+
+#### 7.3.3 INMD based measurement
+
+INMD measurements for ISDN can assess both transmission quality during the information transfer phase and performance parameters related to call establishment and call release phases. INMD based measurement over PSTN has already been recommended in P.561 [22] for speech, and E.459 [23] for G3 facsimile. In the similar way INMD based measurement for ISDN could be recommended for each Teleservice, e.g. G4 facsimile. This is for further study.
+
+
+
+
+
+# SERIES OF ITU-T RECOMMENDATIONS
+
+|                 |                                                                                                                                |
+|-----------------|--------------------------------------------------------------------------------------------------------------------------------|
+| Series A        | Organization of the work of ITU-T                                                                                              |
+| Series B        | Means of expression: definitions, symbols, classification                                                                      |
+| Series C        | General telecommunication statistics                                                                                           |
+| Series D        | General tariff principles                                                                                                      |
+| <b>Series E</b> | <b>Overall network operation, telephone service, service operation and human factors</b>                                       |
+| Series F        | Non-telephone telecommunication services                                                                                       |
+| Series G        | Transmission systems and media, digital systems and networks                                                                   |
+| Series H        | Audiovisual and multimedia systems                                                                                             |
+| Series I        | Integrated services digital network                                                                                            |
+| Series J        | Transmission of television, sound programme and other multimedia signals                                                       |
+| Series K        | Protection against interference                                                                                                |
+| Series L        | Construction, installation and protection of cables and other elements of outside plant                                        |
+| Series M        | TMN and network maintenance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits |
+| Series N        | Maintenance: international sound programme and television transmission circuits                                                |
+| Series O        | Specifications of measuring equipment                                                                                          |
+| Series P        | Telephone transmission quality, telephone installations, local line networks                                                   |
+| Series Q        | Switching and signalling                                                                                                       |
+| Series R        | Telegraph transmission                                                                                                         |
+| Series S        | Telegraph services terminal equipment                                                                                          |
+| Series T        | Terminals for telematic services                                                                                               |
+| Series U        | Telegraph switching                                                                                                            |
+| Series V        | Data communication over the telephone network                                                                                  |
+| Series X        | Data networks and open system communications                                                                                   |
+| Series Y        | Global information infrastructure and Internet protocol aspects                                                                |
+| Series Z        | Languages and general software aspects for telecommunication systems                                                           |

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@@ -0,0 +1,678 @@
+
+
+![ITU logo: A globe with a lightning bolt and the letters ITU.](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg)
+
+ITU logo: A globe with a lightning bolt and the letters ITU.
+
+INTERNATIONAL TELECOMMUNICATION UNION
+
+**ITU-T**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+**E.439**
+
+(03/2000)
+
+SERIES E: OVERALL NETWORK OPERATION,  
+TELEPHONE SERVICE, SERVICE OPERATION AND  
+HUMAN FACTORS
+
+Quality of service, network management and traffic  
+engineering – Network management – Checking the  
+quality of the international telephone service
+
+---
+
+**Test call measurement to assess N-ISDN  
+64 kbit/s circuit-switched bearer service UDI in  
+operation**
+
+ITU-T Recommendation E.439
+
+(Formerly CCITT Recommendation)
+
+---
+
+# ITU-T E-SERIES RECOMMENDATIONS **OVERALL NETWORK OPERATION, TELEPHONE SERVICE, SERVICE OPERATION AND HUMAN FACTORS**
+
+|                                                                                                   |                    |
+|---------------------------------------------------------------------------------------------------|--------------------|
+| <b>OPERATION, NUMBERING, ROUTING AND MOBILE SERVICES</b>                                          |                    |
+| INTERNATIONAL OPERATION                                                                           |                    |
+| Definitions                                                                                       | E.100–E.103        |
+| General provisions concerning Administrations                                                     | E.104–E.119        |
+| General provisions concerning users                                                               | E.120–E.139        |
+| Operation of international telephone services                                                     | E.140–E.159        |
+| Numbering plan of the international telephone service                                             | E.160–E.169        |
+| International routing plan                                                                        | E.170–E.179        |
+| Tones in national signalling systems                                                              | E.180–E.199        |
+| Maritime mobile service and public land mobile service                                            | E.200–E.229        |
+| OPERATIONAL PROVISIONS RELATING TO CHARGING AND ACCOUNTING IN THE INTERNATIONAL TELEPHONE SERVICE |                    |
+| Charging in the international telephone service                                                   | E.230–E.249        |
+| Measuring and recording call durations for accounting purposes                                    | E.260–E.269        |
+| UTILIZATION OF THE INTERNATIONAL TELEPHONE NETWORK FOR NON-TELEPHONY APPLICATIONS                 |                    |
+| General                                                                                           | E.300–E.319        |
+| Phototelegraphy                                                                                   | E.320–E.329        |
+| ISDN PROVISIONS CONCERNING USERS                                                                  | E.330–E.399        |
+| <b>QUALITY OF SERVICE, NETWORK MANAGEMENT AND TRAFFIC ENGINEERING</b>                             |                    |
+| NETWORK MANAGEMENT                                                                                |                    |
+| International service statistics                                                                  | E.400–E.409        |
+| International network management                                                                  | E.410–E.419        |
+| <b>Checking the quality of the international telephone service</b>                                | <b>E.420–E.489</b> |
+| TRAFFIC ENGINEERING                                                                               |                    |
+| Measurement and recording of traffic                                                              | E.490–E.505        |
+| Forecasting of traffic                                                                            | E.506–E.509        |
+| Determination of the number of circuits in manual operation                                       | E.510–E.519        |
+| Determination of the number of circuits in automatic and semi-automatic operation                 | E.520–E.539        |
+| Grade of service                                                                                  | E.540–E.599        |
+| Definitions                                                                                       | E.600–E.699        |
+| ISDN traffic engineering                                                                          | E.700–E.749        |
+| Mobile network traffic engineering                                                                | E.750–E.799        |
+| QUALITY OF TELECOMMUNICATION SERVICES: CONCEPTS, MODELS, OBJECTIVES AND DEPENDABILITY PLANNING    |                    |
+| Terms and definitions related to the quality of telecommunication services                        | E.800–E.809        |
+| Models for telecommunication services                                                             | E.810–E.844        |
+| Objectives for quality of service and related concepts of telecommunication services              | E.845–E.859        |
+| Use of quality of service objectives for planning of telecommunication networks                   | E.860–E.879        |
+| Field data collection and evaluation on the performance of equipment, networks and services       | E.880–E.899        |
+
+For further details, please refer to ITU-T List of Recommendations.
+
+# **TEST CALL MEASUREMENT TO ASSESS N-ISDN 64 kbit/s CIRCUIT-SWITCHED BEARER SERVICE UDI IN OPERATION**
+
+## **Summary**
+
+This Recommendation presents an overview of the operational measurements, defined in Recommendation E.438, that can be performed by test calls and used to assess the performance of N-ISDN 64 kbit/s circuit-switched UDI bearer services. Correspondent measurements (excluding transmission quality measures), performed by exchanges on live traffic, are specified in Recommendation M.3650. These Recommendations should be used by administrations and by ROAs for monitoring and improvement analysis of ISDN services and networks in operations. The measured values can be used both to set guaranteed performance levels in Service Level Agreement with the customers and Service Quality Agreements with other administrations, and to verify, analyse and improve the performance level currently achieved.
+
+###### **Source**
+
+ITU-T Recommendation E.439 was prepared by ITU-T Study Group 2 (1997-2000) and was approved under the WTSC Resolution No. 1 procedure on 13 March 2000.
+
+## FOREWORD
+
+ITU (International Telecommunication Union) is the United Nations Specialized Agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the ITU. The ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis.
+
+The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics.
+
+The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Resolution No. 1.
+
+In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC.
+
+### NOTE
+
+In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+## INTELLECTUAL PROPERTY RIGHTS
+
+The ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. The ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process.
+
+As of the date of approval of this Recommendation, the ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database.
+
+© ITU 2000
+
+All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU.
+
+## CONTENTS
+
+|                                                                                                                            | Page |
+|----------------------------------------------------------------------------------------------------------------------------|------|
+| 1 Introduction.....                                                                                                        | 1    |
+| 2 Scope.....                                                                                                               | 1    |
+| 3 References.....                                                                                                          | 2    |
+| 4 Terms and definitions .....                                                                                              | 3    |
+| 5 Abbreviations and acronyms.....                                                                                          | 3    |
+| 6 General consideration on test call measurement for ISDN.....                                                             | 4    |
+| 7 NP/QOS ISDN parameters considered .....                                                                                  | 4    |
+| 7.1 Test call measurements to assess NP/QOS parameters for ISDN calls using 64 kbit/s UDI single channel.....              | 5    |
+| 7.1.1 Call setup phase .....                                                                                               | 5    |
+| 7.1.2 User information transfer phase.....                                                                                 | 7    |
+| 7.1.3 Call disengagement phase.....                                                                                        | 9    |
+| 7.2 Test call measurements and criteria to assess NP parameters for ISDN calls using 64 kbit/s UDI multiple channels ..... | 10   |
+| 7.2.1 Assessment of NP/QOS parameters for multi-channel calls .....                                                        | 10   |
+| 7.2.2 Specific NP/QOS parameters for multi-channel ISDN communications .....                                               | 10   |
+| 8 Consideration on ISDN calls using Primary Rate Interface.....                                                            | 11   |
+| Annex A – Calculation methods and procedures to derive NP/QOS parameters .....                                             | 11   |
+| Annex B – Data collection principles and statistical procedure .....                                                       | 13   |
+| B.1 Composition of ISDN speed criterion related performance parameters .....                                               | 13   |
+| B.2 Composition of ISDN dependability criterion related performance parameters.....                                        | 14   |
+| Annex C – Statistical treatment of ISDN NP parameters .....                                                                | 14   |
+
+# Introduction
+
+ISDN traffic is growing, particularly for access to Internet and to broadband networks, and for videocommunication services. Standard measurements, as close as possible to those used for PSTN, are needed to monitor the level of performance achieved.
+
+This Recommendation describes practical definitions and methods to be used in operation for measuring the performance of ISDN CSCT 64 kbit/s UDI bearer service on a per-call basis through test call generation. The standard NP/QOS measures and the related definitions and considerations are described in ITU-T Recommendation E.438. Similar measures taken in operation for real traffic are described in ITU-T Recommendation M.3650.
+
+The list of operational measures and the NP/QOS parameters enabling assessment, by the three performance serveability criteria, of the three communication functions of an ISDN call, are described in clause 7. Remarks on performance of multiple channel calls for ISDN are made in 7.2. Specific considerations on ISDN calls using primary rate interface accesses are made in clause 8. Calculation methods and procedures to derive the NP/QOS statistical parameters from the NP measures obtained on a per-call basis are provided in Annex A. In Annex B, data collection principles and statistical calculation procedures for the same parameters are described. Annex C references statistical procedures to estimate the confidence interval for the performance parameters and compliance testing to verify their acceptability level.
+
+# **TEST CALL MEASUREMENT TO ASSESS N-ISDN 64 kbit/s CIRCUIT-SWITCHED BEARER SERVICE UDI IN OPERATION**
+
+# **1 Introduction**
+
+ISDN traffic is growing, particularly for access to Internet and to broadband networks, and for videocommunication services. Standard measurements, as close as possible to those used for PSTN, are needed to monitor the level of performance achieved.
+
+This Recommendation describes practical definitions and methods to be used in operation for measuring the performance of ISDN CSCT 64 kbit/s UDI bearer service on a per-call basis through test call generation. The standard NP/QOS measures and the related definitions and considerations are described in ITU-T Recommendation E.438. Similar measures taken in operation for real traffic are described in ITU-T Recommendation M.3650.
+
+The list of operational measures and the NP/QOS parameters enabling assessment, by the three performance serveability criteria, of the three communication functions of an ISDN call, are described in clause 7. Remarks on performance of multiple channel calls for ISDN are made in 7.2. Specific considerations on ISDN calls using primary rate interface accesses are made in clause 8. Calculation methods and procedures to derive the NP/QOS statistical parameters from the NP measures obtained on a per-call basis are provided in Annex A. In Annex B, data collection principles and statistical calculation procedures for the same parameters are described. Annex C references statistical procedures to estimate the confidence interval for the performance parameters and compliance testing to verify their acceptability level.
+
+# **2 Scope**
+
+This Recommendation describes methods for assessing in operation the serveability performance of setup, information transfer and disengagement phases of 64 kbit/s circuit-switched ISDN connections and networks by means of test calls. Methods are given for determining the values of derived performance parameters from the primary measurements. The parameters themselves are, for the most part, defined in other Recommendations in the E-, G-, I-, M- and O-series.
+
+The methods described in this Recommendation are applicable only to the unrestricted digital bearer service accessed via basic rate and primary rate ISDN<sup>1,2,3,4</sup>. QOS estimation of teleservices using 64 kbit/s UDI requires the definition of appropriate performance parameters that take account of the effects of terminal equipment on QOS: this is for future study. In some cases, a compromise is necessary between the formal definition of a parameter and the means of measuring it. Where such compromises are required, this Recommendation takes the pragmatic view that a performance parameter is of little value if it cannot be operationally measured and its formal definition has been
+
+---
+
+<sup>1</sup> This includes both 64 kbit/s services and  $n \times 64$  kbits/s services.
+
+<sup>2</sup> The inclusion of parameters for assessing the information transfer phase of 3.1 kHz audio and the speech bearer services are for further study. Therefore, the performance of mixed connections ISDN  $\leftrightarrow$  PSTN are not presently considered.
+
+<sup>3</sup> This Recommendation does not consider Dedicated Circuit Connection Type (DCCT) and Packet Switched Connection Type (PSCT).
+
+<sup>4</sup> Packet switched ISDN services, teleservices and supplementary services are not within the scope of this Recommendation at present.
+
+adjusted accordingly. Additionally, not all parameters reflect the way in which a user might view the QOS of service and the parameters and measurements method described herein are for network assessment only. The mapping of the measurement made with this Recommendation into parameters reflecting the customer view is beyond the scope of this Recommendation and is left to individual ROAs.
+
+# 3 References
+
+The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; all users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published.
+
+- [1] ITU-T Recommendation E.438 (2000), *Performance parameters and measurement methods to assess N-ISDN 64 kbit/s circuit switched bearer service UDI in operation.*
+- [2] ITU-T Recommendation M.3650 (1997), *Network performance measurements of ISDN calls.*
+- [3] ITU-T Recommendation E.721 (1999), *Network grade of service parameters and target values for circuit-switched services in the evolving ISDN.*
+- [4] ITU-T Recommendation I.350 (1993), *General aspects of quality of service and network performance in digital networks, including ISDNs.*
+- [5] ITU-T Recommendation I.352 (1993), *Network performance objectives for connection processing delays in an ISDN.*
+- [6] ITU-T Recommendation I.353 (1996), *Reference events for defining ISDN and B-ISDN performance parameters.*
+- [7] ITU-T Recommendation I.355 (1995), *ISDN 64 kbit/s connection type availability performance.*
+- [8] ITU-T Recommendation G.114 (1988), *Mean one-way propagation time.*
+- [9] ITU-T Recommendation G.821 (1996), *Error performance of an international digital connection operating at a bit rate below the primary rate and forming part of an integrated services digital network.*
+- [10] ITU-T Recommendation O.152 (1992), *Error performance measuring equipment for bit rates of 64 kbit/s and  $N \times 64$  kbit/s.*
+- [11] ITU-T Recommendation E.846 (1993), *Accessibility for 64 kbit/s circuit-switched international end-to-end ISDN connection types.*
+- [12] ITU-T Recommendation E.800 (1994), *Terms and definitions related to quality of service and network performance including dependability.*
+- [13] ITU-T Recommendation E.820 (1992), *Call models for serveability and service integrity performance.*
+- [14] ITU-T Recommendation E.425 (1998), *Internal automatic observations.*
+- [15] ITU-T Recommendation I.430 (1995), *Basic user-network interface – Layer 1 specification.*
+- [16] ITU-T Recommendation Q.921 (1997), *ISDN user-network interface – Data link layer specification.*
+
+- [17] ITU-T Recommendation Q.931 (1998), *ISDN user-network interface layer 3 specification for basic call control.*
+- [18] ITU-T Recommendation E.600 (1993), *Terms and definitions of traffic engineering.*
+- [19] ITU-T Recommendation E.850 (1992), *Connection retainability objective for the international telephone service.*
+- [20] ITU-T Recommendation E.428 (1992), *Connection retention.*
+- [21] ITU-T Handbook on Quality of Service and Network Performance, Geneva 1993.
+- [22] ITU-T Recommendation I.112 (1993), *Vocabulary of terms for ISDNs.*
+- [23] ITU-T Recommendation I.431 (1993), *Primary rate user-network interface – Layer 1 specification.*
+- [24] ITU-T Recommendation E.845 (1988), *Connection accessibility objective for the international telephone service.*
+
+# 4 Terms and definitions
+
+For the purposes of this Recommendation, see definitions given in or referenced by E.438.
+
+# 5 Abbreviations and acronyms
+
+This Recommendation uses the following abbreviations:
+
+|        |                                              |
+|--------|----------------------------------------------|
+| ABR    | Answer Bid Ratio                             |
+| ASR    | Answer Seizure Ratio                         |
+| BRA    | Basic Rate Access                            |
+| CDFR   | Call Disengagement Failure Ratio             |
+| CSCT   | Circuit Switched Connection Type             |
+| CSR    | Call Success Ratio                           |
+| DSS1   | Digital Subscriber Signalling System No. 1   |
+| INMD   | In-service, Non-intrusive Measurement Device |
+| ISDN   | Integrated Services Digital Network          |
+| MCDD   | Mean Call Disengagement Delay                |
+| MCED   | Mean Call Establishment Delay                |
+| MDOWPD | Mean Differential One-Way Propagation Delay  |
+| MES    | Mean Errored Seconds                         |
+| MOWPD  | Mean One-Way Propagation Delay               |
+| MR     | Misrouting Ratio                             |
+| MSES   | Mean Severely Errored Seconds                |
+| NER    | Network Effectiveness Ratio                  |
+| NP     | Network Performance                          |
+| OAM    | Operation Administration and Maintenance     |
+| PRA    | Primary Rate Access                          |
+
+|     |                                  |
+|-----|----------------------------------|
+| PRR | Premature Release Rate           |
+| QOS | Quality of Service               |
+| TE  | Terminal Equipment               |
+| UDI | Unrestricted Digital Information |
+
+# 6 General consideration on test call measurement for ISDN
+
+All of the end-to-end ISDN NP/QOS parameters not involving the terminal's performance and the user's behaviour can be easily measured by test calls. Most of the serveability parameters are measured on the D-channel and are derived from observations of specific DSS1 protocol signals at the S/T interface and from call states transitions (user side), as defined in [16] and [17]. Those including the user behaviour (such as ASR, ABR) are not directly measurable by test calls. For these parameters, measurement of real traffic is recommended. For the parameters related to call transmission quality, test call measurements are taken on the B-channel. It is also possible to distinguish and to measure all the channels (and connections) involved in a multi-channel call using test calls. Additionally, misrouted calls can be easily detected. By analyzing these elementary data on connections suffering poor performance, it is possible to detect and locate the causes of failures and malfunctions in the network.
+
+The test call measurements are normally performed only at the transport layers (layer 1-3 according to OSI model) of the bearer protocols, as the test call equipment is usually only able to emulate the bearer services. However, the trend is to include in test equipment the capability to emulate higher layers of standardized protocols for some popular teleservices (such as T4 for fax, H.221/H.242 for videocommunication or H.323 for videoconferencing)<sup>5</sup> making specific measurements closer to the QOS experienced by the users.
+
+# 7 NP/QOS ISDN parameters considered
+
+This clause gives methods and criteria for making end-to-end NP/QOS elementary measures in operation, on a per-call basis by test call devices. The related NP/QOS parameters defined in [1] are listed in Table 1<sup>6</sup>, measures of these can be statistically derived from representative test call populations by using the formulae shown in Annex A. These parameters are all expressed as % values. Specific ISDN↔PSTN NP parameters are not included, being for further study.
+
+<sup>5</sup> Thus also including both the performance of the terminal and of interoperability with the network and with others terminals. Nevertheless, some terminal dependent implementation feature (such as timer, signalling options, processing times, functional procedures, etc.) cannot be precisely taken into account.
+
+<sup>6</sup> For specific operational purposes, also the "Misrouting probability" parameter (see [12]) can be estimated.
+
+**Table 1/E.439 – Basic ISDN NP/QOS operational parameters**
+
+| NP/QOS parameter                             | Symb   | Rec.           | NP elementary measure                                | Symb | Perform. Criterion |
+|----------------------------------------------|--------|----------------|------------------------------------------------------|------|--------------------|
+| <b>Connection Setup Phase</b>                |        |                |                                                      |      |                    |
+| Network Effectiveness Ratio                  | NER    | E.425          | connection setup outcome                             | cs0  | D                  |
+| Call Success Ratio                           | CSR    | E.438          | connection setup outcome & destination test terminal | cs0  | D                  |
+| Mean Call Establishment Delay                | MCED   | I.352          | connection establishment delay                       | ced  | S                  |
+| <b>Connection Information Transfer Phase</b> |        |                |                                                      |      |                    |
+| Mean One-Way Propagation Delay               | MOWPD  | G.114          | one-way propagation delay                            | owpd | S                  |
+| Mean Differential OW Propagation Delay       | MDOWPD |                | one-way propagation delay                            | owpd | S                  |
+| MeanErrored Seconds                          | MES    | G.821          | bit error rate                                       | ber  | A                  |
+| Mean SeverelyErrored Seconds                 | MSES   | G.821          | bit error rate                                       | ber  | A                  |
+| Premature Release Rate                       | PRR    | E.850<br>E.428 | User information transfer outcome                    | uito | D                  |
+| <b>Connection Disengagement Phase</b>        |        |                |                                                      |      |                    |
+| Mean Call Disengagement Delay                | MCDD   | I.352          | call disengagement delay                             | cdd  | S                  |
+| Call Disengagement Failure Ratio             | CDFR   | E.800          | call disengagement outcome                           | cdo  | D                  |
+| A Accuracy<br>D Dependability<br>S Speed     |        |                |                                                      |      |                    |
+
+## 7.1 Test call measurements to assess NP/QOS parameters for ISDN calls using 64 kbit/s UDI single channel<sup>7</sup>
+
+### 7.1.1 Call setup phase
+
+#### Elementary performance measures (performed on a single call)
+
+##### Connection setup outcome (cs0)
+
+*Measurement:* Reception at the S/T interface (calling user side) of a CONNECT<sup>8</sup> DSS1 message from the network (cs0 = Y → call effective), or not (cs0 = N → call ineffective).
+
+<sup>7</sup> The accuracy of the testing performed to check the dependability criteria depends on how and how many optional parts of the protocol in the user side specified in [17] (necessary to point out any malfunctions in the DSS1 call control procedure performed by the network) are implemented in the TE. Moreover, for the handling of message type or sequence errors, the STATUS ENQUIRY shall be sent to the network in order to obtain the call state in the network side.
+
+<sup>8</sup> All the NP/QOS measures referring to the ALERTING message are equivalent to those referring to CONNECT message (except in some cases for a negligible and constant processing time of the test call device when it generates both messages). The reason is that the test call equipment (and loop-back devices) is always regarded as being available (if not, the measure should be managed differently or discarded).
+
+##### Call establishment delay (ced)
+
+*Measurement:* Measure of the time interval (ced – expressed in milliseconds) for each effective call beginning at the instant in which *the first bit* of the first DSS1 layer 2 frame of the call attempt crosses the S/T interface, and ending when *the last bit* of the first layer 2 frame, coming from the network and containing the layer 3 CONNECT message relative to the same call, is received at the same interface<sup>9</sup>.
+
+*Usage notes:* The measured time intervals shall be representative of the setup sequence most commonly experienced by the user of a specific application requesting the circuit-switched bearer service under test.
+
+#### NP/QOS parameters (estimated on a sample of calls)
+
+##### Network Effectiveness Ratio (NER)<sup>10</sup>
+
+*Definition:* E.425 [14]
+
+*Estimation:* The NER is evaluated as the ratio of the number  $N_a$  of *effective calls* (seizures with  $cso = Y$ ) to the number  $N_s$  of *seizures* expressed as a percentage. A seizure is a bid (test call) that obtains a B-channel assignment notification under the assumption that the destination number, selected automatically by the test call device, is correctly provided.
+
+##### Call Success Ratio (CSR)
+
+*Definition:* E.438 [1]
+
+*Estimation:* The CSR is evaluated as the ratio of the number  $N_d$  of *effective calls* (seizures with  $cso = Y$ ) correctly routed to the destination terminal (recognized by the calling terminal's management system<sup>11</sup>) to the number  $N_s$  of *seizures* expressed as a percentage. A seizure is a bid (test call) that obtains a B-channel assignment notification under the assumption that the destination number, selected automatically by the test call device, is correctly provided.
+
+---
+
+<sup>9</sup> In order to obtain a more accurate measure, the delay introduced by the layer 2 link establishment should be included, as in the case of a failure of the first attempt to obtain the establishment of multiple frame operation, a successive request cannot be sent before 1 second (the timers T200 implemented in the user and in the network side last after that time). This is due to the timer T200 activated at the setup of the layer 2 of the DSS1 protocol after a call request, when a SABME (Set Asynchronous Balanced Mode Extended) unnumbered frame is sent, and deactivated by the UA (Unnumbered Acknowledgment) unnumbered frame sent back by the Layer 2 entity which have received the SABME frame. In the case of a failure (the setup of Layer 2 cannot be completed) the same entity answers with a DM (Disconnect Mode) and the timer is stopped. But if neither a UA nor a DM frame is received within 1 second, the timer expires and the same procedure is reactivated for other 2 times, and then definitively terminated by sending to the layer 2 management entity an MDL-ERROR-INDICATION primitive.
+
+<sup>10</sup> The complementary measure NER is also used in operation, according to [24].
+
+<sup>11</sup> The procedure for the remote terminal recognition shall be as reliable and quick as possible in order to avoid errors (acknowledgment of a wrong TE or failed recognition of the right TE) and to limit as much as possible calls released by the a remote terminal before the procedure completion: in these cases it could be difficult to distinguish between misrouted connections and calls prematurely released by the network.
+
+##### Mean Call Establishment Delay (MCED)
+
+*Definition:* I.352 [5]
+
+*Estimation:* The *Mean Call Establishment Delay* (MCED) is evaluated as the arithmetic mean of the *call establishment delay* (ced) values measured in a representative population of test calls having successfully performed the network access function<sup>12</sup>.
+
+### 7.1.2 User information transfer phase
+
+#### Elementary performance measures (performed on a single call)
+
+##### One-way propagation delay (owpd)
+
+*Definition:* G.114 [8]
+
+The *one-way propagation delay* of a connection is normally evaluated as the mean of the propagation delays in the two directions of transmission<sup>13</sup>. A sufficiently accurate one-way propagation delay measurement requires at present too complex and costly solutions (basically two test call devices very well synchronized).
+
+*Measurement:* After a successful connection setup phase of a test call directed to a remote device capable of performing the loop-back function, if:
+
+- $T$  is the time interval in milliseconds beginning with the sending of the first bit of a binary sequence at S/T interface of the calling TE and ending with the reception at the same interface of the last bit of the same sequence reflected by the loop-back device on the same B-channel used by the calling device in transmission.
+- $N$  is the number of bits of the binary sequence.
+- $T_L$  is the delay in milliseconds introduced by the loop-back function performed in the remote terminal, previously measured as the time interval beginning with the reception of one bit at S/T interface and ending with the retransmission of the same bit over the same channel in the opposite direction.
+
+The *mean one-way propagation delay* shall be computed as:
+
+$$0.5 \times (T - N \times 0.015625 - T_L)$$
+
+If the binary sequence is such that the relative contribution<sup>14</sup> ( $N \times 0.015625$ ) added up to the loop-back function delay  $T_L$  is shorter than a millisecond, these terms can be regarded as irrelevant, if not then the above mentioned formula shall be used in order to obtain a propagation delay measurement independent of the particular implementation adopted.
+
+##### Bit error rate (ber)
+
+*Definition:* G.821 [9]
+
+*Measurement:* In conformance with [9], the *bit error rate (ber)* over a single B-channel shall be measured by the direct comparison of a pseudorandom test pattern made up with 2047 bits ( $2^{11} - 1$ ) transmitted and received over the same B-channel.
+
+---
+
+<sup>12</sup> In case of a single channel call, this is an estimation of the average delay experienced by a user for effective calls from the completion of the access requests to the reception of the indications of a connection to a remote user.
+
+<sup>13</sup> This parameter gives a reliable estimation of the delays characterizing the two directions of transmission if these are provided by the same media. This condition is generally accomplished by CSCT ISDN connections.
+
+<sup>14</sup> 0.015625 is the mean transmission time in milliseconds of one bit through a 64 kbit/s channel.
+
+Two are two possible alternatives:
+
+- *One-way BER measurements*: performed transmitting a test pattern to a remote device comparing it to an identical one, the same being done on the opposite direction of the same B-channel. In this case, two values will be available for each test call.
+- *Two-way BER measurements*: performed transmitting the test pattern to a remote loop-back device which retransmits transparently the data received over the same B-channel in the opposite direction.
+
+The first solution shall be preferred to the second one. Whatever solution is chosen, it should be explicitly indicated (*one-way* or *two-way*).
+
+###### **stotal, sunavail, errored seconds (es), severely errored seconds (ses)**
+
+*Definitions*: G.821 [9]
+
+*Measurements*: Every **ber** measurement (one-way or two-way) shall be provided with the relative values of the following derived measures as defined in [9]:
+
+- *stotal*: the total *ber* monitoring time in seconds.
+- *sunavail*: the number of one second intervals where the connection is deemed not to be available<sup>15</sup>.
+- *es*: *errored seconds* is the number of one second intervals within *savail* ( $savail = stotal - sunavail$ ), rounded off to the next higher integer) with at least one errored bit.
+- *ses*: *severely errored seconds* is the number of one second intervals within *savail* ( $savail = stotal - sunavail$ , rounded off to the next higher integer) where *ber* is worse than  $10^{-3}$ .
+
+##### **User information transfer outcome (uito)**
+
+*Measurement*: Correct release process started by the test call device (after the reception of the CONNECT DSS1 message) at the end of the test call duration through the sending of a DISCONNECT DSS1 message (*uito* = Y); on the contrary, if a DISCONNECT, RELEASE or RELEASE COMPLETE DSS1 message is received from the network before the ending of the test call duration, the call is considered as prematurely released (*uito* = N)
+
+#### **NP/QOS parameters (estimated on a sample of calls)**
+
+##### **Mean One-Way Propagation Delay (MOWPD)**
+
+*Estimation*: The *mean one-way propagation delay* is evaluated as the arithmetic mean of the one-way propagation delay values measured in a representative population of test calls.
+
+##### **Mean Errored Seconds (MES)**
+
+*Estimation*: Percentage of *Errored Seconds* measured in the *Savail* periods, averaged over a significant population of test calls with BER measurements.
+
+##### **Mean Severely Errored Seconds (MSES)**
+
+*Estimation*: Percentage of *Severely Errored Seconds* in the *Savail* periods, averaged over a significant population of test calls with BER measurements.
+
+---
+
+<sup>15</sup> An unavailability period begins with ten consecutive seconds with a BER worse than  $10^{-3}$  for each second and ends with the first of ten seconds with a BER better than  $10^{-3}$ .
+
+##### Premature Release Rate (PRR)
+
+*Definitions:* E.850 [19]; E.428 [20].
+
+*Estimation:* The PRR is evaluated as the ratio of the number of prematurely released calls ( $u_{ito} = N$ ) to the number of test calls having successfully performed the access function, normalized to the mean call holding time<sup>16</sup> expressed in minutes.
+
+The formula for the calculation of the statistical parameter normalized to the mean call holding time (see [19]) is also given in Annex A.
+
+### 7.1.3 Call disengagement phase
+
+#### Elementary performance measures (performed on a single call)
+
+##### Call disengagement delay (cdd)
+
+*Definition:* The *disengagement delay*, for a successfully disengaged call, is the time interval beginning with the sending by the TE of a call clearing request and ending when an appropriate answer is received from the network.
+
+*Measurement:* It shall be measured for calls successfully cleared by the TE and by the network:
+
+- Call clearing by the TE: the *disengagement delay* is the time interval (expressed in milliseconds) beginning with the *sending* by the TE of the first message requesting a call clearing (DISCONNECT or RELEASE) and ending with the *receiving* from the network of the first message stating that the call has been cleared (RELEASE or RELEASE COMPLETE respectively)<sup>17</sup>.
+- Call clearing by the network: the *disengagement delay* is the time interval (expressed in milliseconds) beginning with the *sending* by the TE of the first message requesting the release of a call disengaged by the network (RELEASE) and ending with the *receiving* from the network of the first message stating that the call has been released (RELEASE COMPLETE).
+
+##### Call disengagement outcome (cdo)
+
+*Measurement:* Reception (cdo = Y) or not (cdo = N) from the network of a RELEASE or a RELEASE COMPLETE DSS1 message. cdo = y means connection correctly released (making the connection resources available for a new connection).
+
+#### NP/QOS parameters (estimated on a sample of calls)
+
+##### Mean Call Disengagement Delay (MCDD)
+
+*Definition:* I.352<sup>18</sup> [5]
+
+*Estimation:* The *Mean Call Disengagement Delay* is evaluated as the arithmetic mean of the call *disengagement delay* values measured in a representative test call population with a successfully performed disengagement function.
+
+---
+
+<sup>16</sup> The duration of the mean call holding time, reflecting average ISDN call duration profiles could be derived from real traffic monitoring.
+
+<sup>17</sup> The time of occurrence of the sending of a DSS1 layer 3 message (from a TE to the NT) is the time at which the first bit of the frame crosses the S/T interface, while that of receiving (from the NT to TE) is the time at which the last bit of the specified message crosses the same interface.
+
+<sup>18</sup> The correspondent parameter in I.352 is called "release delay".
+
+##### Call Disengagement Failure Ratio (CDFR)
+
+*Definition:* E.800<sup>19</sup> [12] The *call disengagement failure probability* is the probability that a disengagement attempt is not successfully performed<sup>20</sup>.
+
+*Estimation:* Ratio of failed disengagement attempts (those with  $cdo = N$ ) to the total number of test calls performed in a specified time period.
+
+## 7.2 Test call measurements and criteria to assess NP parameters for ISDN calls using 64 kbit/s UDI multiple channels
+
+### 7.2.1 Assessment of NP/QOS parameters for multi-channel calls
+
+The measurements taken by test calls permit the assessment of not only connection related performance parameters, but also call<sup>21</sup> related parameters. In fact, in the case of a multi-channel call, the test call equipment is able to identify the channels used for each call to the destination terminal or loop-back device, and to measure the performances of the single connections involved between the S/T interfaces of each connection. So the overall end-to-end NP/QOS performance parameters, still estimated between the S/T interfaces, can be derived, from those of each channel involved in the call. The parameters are obtained (as mean values) by applying the performance criteria related composition formulae contained in Annex B<sup>22</sup>. For dependability parameters, it is sufficient to consider the multi-channel call not effective if at least one connection to the destination is not established.
+
+Additional performance parameters, specific for multi-channel calls, should be measured. For example for videotelephony or videoconference (where audio and video share different channels), *the differential propagation delay between the channels involved* is a fundamental NP parameter used in operation for the user information transfer phase<sup>23</sup>.
+
+### 7.2.2 Specific NP/QOS parameters for multi-channel ISDN communications
+
+#### Elementary performance measures
+
+##### Differential one-way propagation delay (dowpd)
+
+*Definition:* For the definition of the differential one-way propagation delay, see clause 4 of [1], [8] and 7.1.2.
+
+*Measurement:* For a call using two B-channels ( $N = 2$ ) it can be obtained by sending simultaneously<sup>24</sup> a recognizable bit (or sequence of bits) on both channels at the originating S/T interface (e.g. BRI), and measuring at the terminating S/T interface of the connection the time difference between the two instants of the reception of the same bit (or the last bit of the sequence).
+
+---
+
+<sup>19</sup> In E.800 is called "release failure probability".
+
+<sup>20</sup> For all the test calls, irrespective of their effectiveness and outcome.
+
+<sup>21</sup> A call, related to a teleservice/application request, can be both single and multi-channel.
+
+<sup>22</sup> It is important to distinguish in the evaluations, in the reports and as objectives between NP/QOS parameters related to single or to multi-channel call (for example NER, CSR, CED, ..., etc.)
+
+<sup>23</sup> Depending on the allocation of the media services (voice, data, video) on the set of channels involved in a multi-channel call, there are some fundamental differences between connections performance and media QOS levels measured. If high level protocols, as well as the information exchanged on the B-channel, are also measurable by improved test call software tools (for standardized teleservices/application protocols), the resulting values are very close to the level of QOS experienced by the user.
+
+<sup>24</sup> Simultaneously means that the maximum tolerated error, affecting the measured time, is one bit transmitting time.
+
+For multi-channel calls (involving a number  $N > 2$  B-channels), a vector of  $2 \cdot \binom{N}{2}$  dowpd values (one for each couple of channels and for each way of transmission) can be obtained<sup>25</sup>.
+
+#### NP/QOS parameters (estimated on a sample of calls)
+
+##### Mean Differential One-Way Propagation Delay (MDOWPD)<sup>26</sup>
+
+*Estimation:* The *mean differential one-way propagation delay*, for a multi-channel ISDN communication, is the arithmetic mean, in a representative population of test multi-channel calls, of all the absolute values of the differences between the one-way propagation delays values in msec, measured between and referred to each pair of B-channels used in a multi-channel ISDN communication.
+
+# 8 Consideration on ISDN calls using Primary Rate Interface
+
+If an ISDN service call uses a subset or the whole number of the PRI channels, all the considerations and the NP/QOS parameters described in 7.1 and 7.2 apply. The measures are performed at the T interface, in accordance with [23].
+
+## ANNEX A
+
+### Calculation methods and procedures to derive NP/QOS parameters
+
+This annex lists the main formulae that can be used to estimate (to evaluate, to assess) the NP/QOS parameters defined in clause 7.
+
+For formulae involving dependability aspects (where the performance parameters is expressed as a ratio), the counters of the states and events in the call process (see also Figure A.1) are the following:
+
+- $Nb$  Total number of test calls (*bids*) correctly made.
+- $Ns$  Number of *seizures* (test calls with B-channel assigned).
+- $Na$  Number of *bids* (*seizure*<sup>27</sup>) resulting in an answer signal (cso = Y).
+- $Nd$  Number of effective bids correctly routed to the destination terminal.
+- $Ne$  Number of completed test calls with errors on the information transferred (BER  $\neq 0$ ).
+- $Ni$  Number of effective bids terminating correctly the user information transfer phase (uito = Y).
+- $Nc$  Number of bids completing correctly and successfully all the communication phases.
+- $Nr$  Number of effective calls not performing correctly the release function<sup>28</sup> (cdo = N).
+- $Tc$ <sup>29</sup> Duration of the test call in case of normal release by the calling TE.
+- $Th$  Average call duration (derived from traffic monitoring).
+
+<sup>25</sup> In this case the recognizable bit (or sequence of bits) must be sent simultaneously to all the N channels.
+
+<sup>26</sup> This parameter is related to the speed criterion applied to the user information transfer phase.
+
+<sup>27</sup> A bid must become a seizure to be effective.
+
+<sup>28</sup> Including those prematurely released or not effective .
+
+<sup>29</sup> The  $Tc$ ,  $Th$  and  $Tp$  are call holding times.
+
+$T_p$  Estimated average call duration of prematurely released calls.
+
+The elementary time measurements used for the formulae involving the speed criterion are:
+
+ced Connection establishment delay for the effective calls in ms.
+
+owpd One-way propagation delay in ms.
+
+cdd Connection disengagement delay in ms.
+
+While the measurements for the formulae involving the accuracy criterion are:
+
+es Errored seconds.
+
+ses Severely errored seconds.
+
+![Flow diagram of call processing stages: Nb -> [B-channel assigned to the call] -> Ns -> [Answer signal received] -> Na -> [Call routed to correct destination] -> Nd -> [User inform. transfer completed] -> Ni -> [Release correctly performed] -> Nc. A small code T0207650-99 is at the bottom right.](51db757d054ce1ce83c436a3578b56ca_img.jpg)
+
+```
+
+    Nb --- [B-channel assigned to the call] --- Ns --- [Answer signal received] --- Na --- [Call routed to correct destination] --- Nd --- [User inform. transfer completed] --- Ni --- [Release correctly performed] --- Nc
+    
+```
+
+T0207650-99
+
+Flow diagram of call processing stages: Nb -> [B-channel assigned to the call] -> Ns -> [Answer signal received] -> Na -> [Call routed to correct destination] -> Nd -> [User inform. transfer completed] -> Ni -> [Release correctly performed] -> Nc. A small code T0207650-99 is at the bottom right.
+
+**Figure A.1/E.439 – Counters (on a sample of Nb test calls) of the number of calls having performed correctly the related call processing function**
+
+**Table A.1/E.439 – Formulae to evaluate the basic ISDN NP/QOS operational connection parameters**
+
+| NP/QOS parameter                                      | Estimation formulae                                                       |
+|-------------------------------------------------------|---------------------------------------------------------------------------|
+| <b>Connection Setup Phase (Note)</b>                  |                                                                           |
+| Network Effectiveness Ratio                           | $NER\% = \frac{Na}{Ns} \cdot 100$                                         |
+| Call Success Ratio                                    | $CSR\% = \frac{Nd}{Ns} \cdot 100$                                         |
+| Mean Call Establishment Delay (ms)                    | $MCED = \frac{\sum_{i=1}^{Na} ced_i}{Na}$                                 |
+| <b>Connection Information Transfer Phase</b>          |                                                                           |
+| Mean One-Way Propagation Delay (ms)                   | $MOWPD = \frac{\sum_{i=1}^{Na} owpd_i}{Na}$                               |
+| Mean Differential OWPD between the channels i, j (ms) | $MDOWPD_{i,j} = \frac{\sum_{K=1}^{Na} (owpd_i^{(k)} - owpd_j^{(k)})}{Na}$ |
+| Mean Errored Seconds                                  | $MES\% = \frac{\sum_{i=1}^{Na} \frac{es_i}{savail}}{Na} \cdot 100$        |
+
+**Table A.1/E.439 – Formulae to evaluate the basic ISDN NP/QOS operational connection parameters (concluded)**
+
+| NP/QOS parameter                                                                                                                                                                 | Estimation formulae                                                  |
+|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|----------------------------------------------------------------------|
+| Mean Severely Errored Seconds                                                                                                                                                    | $MSES\% = \frac{\sum_{i=1}^{Na} \frac{ses_i}{savail}}{Na} \cdot 100$ |
+| Premature Release Rate                                                                                                                                                           | $PRR = \frac{1 - \frac{Ni}{Na}}{Th} \cdot 100$                       |
+| <b>Connection Disengagement Phase</b>                                                                                                                                            |                                                                      |
+| Mean Call Disengagement Delay (ms)                                                                                                                                               | $MCDD = \frac{\sum_{i=1}^{Na} cdd_i}{Na}$                            |
+| Call Disengagement Failure Ratio                                                                                                                                                 | $CDFR = \frac{Nr}{Na} \cdot 100$                                     |
+| NOTE – For specific operational purposes the misrouting probability MR (see [12]) can also be estimated, by applying the following formula: $MR = (1 - \frac{Nd}{Na}) \cdot 100$ |                                                                      |
+
+## ANNEX B
+
+### Data collection principles and statistical procedure
+
+In case of ISDN multi-channel communication, it is possible to derive the overall network related performance of the call by using performance data of single channel and the composition formulae.
+
+### B.1 Composition of ISDN speed criterion related performance parameters
+
+For speed related NP parameters, if we assume that the delays  $d_1, d_2, \dots, d_n$  of each of the  $n$  channels varies randomly with mean  $D_1, D_2, \dots, D_n$  and 95% points  $z_1, z_2, \dots, z_n$  respectively, then the total delay  $d = d_1 + d_2 + \dots + d_n$  has a distribution with **mean  $D = D_1 + D_2 + \dots + D_n$**  with no further assumptions.
+
+If, in addition, the delays are assumed to be statistically independent and that  $z_i = D_i + k \cdot \sigma_i$  with the same  $k$  for all the portions (being  $\sigma_i$  the standard deviation of  $D_i$ ), then the similar equality is also assumed for  $d$ , i.e.  $Z = D + k \cdot \sigma_d$ , where  $Z$  is the X% point (for example 95%) of  $d$ . These equalities are true for normal distributions with  $k = 1.645$ . Then the variance of  $d$  is the sum of the variances of the  $D_i$ . It follows that the 95% point of  $d$  is given by:
+
+$$Z = D + [(z_1 - m_1)^2 + (z_2 - m_2)^2 + \dots + (z_n - m_n)^2]^{1/2}$$
+
+The assumption of normality seems reasonable, but other assumptions are possible and could give substantially different answers.
+
+**Example:** In a two-channel call, the channel c1 has a setup delay of 5 seconds, while the second channel c2 has a call setup delay of 7 seconds. The total delay introduced by the network between the S/T interfaces of the connection is globally of 12 seconds.
+
+### B.2 Composition of ISDN dependability criterion related performance parameters
+
+The failure probability ratio (related to accessibility, retainability, integrity and release measures) of a call involving n channels can be roughly estimated as the sum of the failure probability of each channel by assuming that the success probability is high enough and does not change substantially among the channels used.
+
+As an example, in the case of a call involving 2 channels (such as BRI videotelephony call), the formula can be easily derived:
+
+$$\begin{aligned}
+ \Pr(\text{failure 2B-channel call}) &= \\
+ &= 1 - \Pr(\text{successful 2B-channel call}) = \\
+ &= 1 - \Pr(\text{successful 1B-channel call}) \cdot \Pr(\text{successful second B-channel call} / \Pr(\text{successful first B-channel call})) \approx \\
+ &\approx 1 - \Pr(\text{successful 1B-channel call}) \cdot \Pr(\text{successful 1B-channel call}) = \\
+ &= 1 - [\Pr(\text{successful 1B-channel call})]^2 = \\
+ &= 1 - \{1 - [\Pr(\text{failure 1B-channel call})]\}^2 = \\
+ &= 1 - \{1 - 2 \cdot [\Pr(\text{failure 1B-channel call})] + [\Pr(\text{failure 1B-channel call})]^2\} = \\
+ &= 2 \cdot [\Pr(\text{failure 1B-channel call})] - [\Pr(\text{failure 1B-channel call})]^2
+ \end{aligned}$$
+
+If  $\Pr(\text{failure 1B-channel call}) \ll 1$  (acceptable hypothesis) then we can neglect the  $[\Pr(\text{failure 1B-channel call})]^2$  term and we can conclude that :
+
+$$\Pr(\text{failure 2B-channel call}) \approx 2 \cdot [\Pr(\text{failure 1B-channel call})]$$
+
+## ANNEX C
+
+### Statistical treatment of ISDN NP parameters
+
+In this annex some guidelines regarding the data collection and standard methods for their statistical processing (sample size and confidence interval estimation, compliance testing) are given.
+
+All the NP/QOS parameters are categorized into four main sets as outlined in Table C.1. By using the appropriate class identified by this table, it is possible to estimate the confidence interval related to a measure, and to verify if the assessed values for that parameter complies with its objective threshold. The specific statistical treatment, referenced in Annex C of [21], should be applied.
+
+The network performance parameters that are time related are normally evaluated as **mean**. Their objective values can also be obtained by fixing the one side statistical tolerance interval and estimating the fractile by the available sample. Sometimes the operator prefers to estimate the ratio of calls which have an achieved value satisfactory (or unsatisfactory) with respect to a prefixed threshold (or objective or outcome) to the total number of calls. In this case, the column **ratio** should be used. An example is the % age of calls exceeding x msec to establish the connection (or the call). The dependability and the accuracy parameters are normally estimated in terms of a **ratio**. The frequency of a prematurely released call is the only parameter expressed as a **rate**.
+
+The statistical NP and QOS parameters shall be derived from representative test calls populations, each of them performed from a specific origin to a specific destination or between specific users (or class of users).
+
+The test calls should be scheduled to reflect traffic variations over the hours of a day, the days of a week and the months of a year. Alternatively, they may be uniformly distributed and weighted according to the real traffic variations.
+
+**Table C.1/E.439 – Statistical classification of ISDN QOS/NP parameters**
+
+| <b>NP/QOS parameter</b>                                    | <b>Mean</b> | <b>% Fractile</b> | <b>Ratio</b> | <b>Rate/<br/>Intensity</b> |
+|------------------------------------------------------------|-------------|-------------------|--------------|----------------------------|
+| <b>MCED</b> – Mean Call Establishment Delay                | X           | X                 |              |                            |
+| <b>NER</b> – Network Effectiveness Ratio                   |             |                   | X            |                            |
+| <b>MOWPD</b> – Mean One-Way Propagation Delay              | X           | X                 |              |                            |
+| <b>MDOPD</b> – Mean Differential One-Way Propagation Delay | X           | X                 |              |                            |
+| <b>MES</b> – MeanErrored Seconds                           |             |                   | X            |                            |
+| <b>MSES</b> – Mean SeverelyErrored Seconds                 |             |                   | X            |                            |
+| <b>PRR</b> – Premature Release Rate                        |             |                   |              | X                          |
+| <b>MCDD</b> – Mean Call Disengagement Delay                | X           | X                 |              |                            |
+| <b>CDFR</b> – Call Disengagement Failure Ratio             |             |                   | X            |                            |
+
+
+
+
+
+# ITU-T RECOMMENDATIONS SERIES
+
+|                 |                                                                                                                                |
+|-----------------|--------------------------------------------------------------------------------------------------------------------------------|
+| Series A        | Organization of the work of the ITU-T                                                                                          |
+| Series B        | Means of expression: definitions, symbols, classification                                                                      |
+| Series C        | General telecommunication statistics                                                                                           |
+| Series D        | General tariff principles                                                                                                      |
+| <b>Series E</b> | <b>Overall network operation, telephone service, service operation and human factors</b>                                       |
+| Series F        | Non-telephone telecommunication services                                                                                       |
+| Series G        | Transmission systems and media, digital systems and networks                                                                   |
+| Series H        | Audiovisual and multimedia systems                                                                                             |
+| Series I        | Integrated services digital network                                                                                            |
+| Series J        | Transmission of television, sound programme and other multimedia signals                                                       |
+| Series K        | Protection against interference                                                                                                |
+| Series L        | Construction, installation and protection of cables and other elements of outside plant                                        |
+| Series M        | TMN and network maintenance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits |
+| Series N        | Maintenance: international sound programme and television transmission circuits                                                |
+| Series O        | Specifications of measuring equipment                                                                                          |
+| Series P        | Telephone transmission quality, telephone installations, local line networks                                                   |
+| Series Q        | Switching and signalling                                                                                                       |
+| Series R        | Telegraph transmission                                                                                                         |
+| Series S        | Telegraph services terminal equipment                                                                                          |
+| Series T        | Terminals for telematic services                                                                                               |
+| Series U        | Telegraph switching                                                                                                            |
+| Series V        | Data communication over the telephone network                                                                                  |
+| Series X        | Data networks and open system communications                                                                                   |
+| Series Y        | Global information infrastructure and Internet protocol aspects                                                                |
+| Series Z        | Languages and general software aspects for telecommunication systems                                                           |
+
+\*18598\*

marked/E/T-REC-E.454-199610-I_PDF-E/raw.md

@@ -0,0 +1,363 @@
+
+
+![ITU logo: A globe with a lightning bolt and the letters ITU.](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg)
+
+ITU logo: A globe with a lightning bolt and the letters ITU.
+
+INTERNATIONAL TELECOMMUNICATION UNION
+
+**ITU-T**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+**E.454**
+
+(10/96)
+
+SERIES E: TELEPHONE NETWORK AND ISDN
+
+Quality of service, network management and traffic  
+engineering – Network management – Checking the  
+quality of the international telephone service
+
+---
+
+**Transmission performance metrics based on  
+Error Correction Mode (ECM) facsimile**
+
+ITU-T Recommendation E.454
+
+(Previously CCITT Recommendation)
+
+---
+
+# ITU-T E-SERIES RECOMMENDATIONS **TELEPHONE NETWORK AND ISDN**
+
+|                                                                                                   |                    |
+|---------------------------------------------------------------------------------------------------|--------------------|
+| <b>OPERATION, NUMBERING, ROUTING AND MOBILE SERVICES</b>                                          |                    |
+| INTERNATIONAL OPERATION                                                                           | E.100–E.229        |
+| OPERATIONAL PROVISIONS RELATING TO CHARGING AND ACCOUNTING IN THE INTERNATIONAL TELEPHONE SERVICE | E.230–E.299        |
+| UTILIZATION OF THE INTERNATIONAL TELEPHONE NETWORK FOR NON-TELEPHONY APPLICATIONS                 | E.300–E.329        |
+| ISDN PROVISIONS CONCERNING USERS                                                                  | E.330–E.399        |
+| <b>QUALITY OF SERVICE, NETWORK MANAGEMENT AND TRAFFIC ENGINEERING</b>                             |                    |
+| NETWORK MANAGEMENT                                                                                | E.400–E.489        |
+| International service statistics                                                                  | E.400–E.409        |
+| International network management                                                                  | E.410–E.419        |
+| <b>Checking the quality of the international telephone service</b>                                | <b>E.420–E.489</b> |
+| TRAFFIC ENGINEERING                                                                               | E.490–E.799        |
+| Measurement and recording of traffic                                                              | E.490–E.505        |
+| Forecasting of traffic                                                                            | E.506–E.509        |
+| Determination of the number of circuits in manual operation                                       | E.510–E.519        |
+| Determination of the number of circuits in automatic and semi-automatic operation                 | E.520–E.539        |
+| Grade of service                                                                                  | E.540–E.599        |
+| Definitions                                                                                       | E.600–E.699        |
+| ISDN traffic engineering                                                                          | E.700–E.749        |
+| Mobile network traffic engineering                                                                | E.750–E.799        |
+| QUALITY OF TELECOMMUNICATION SERVICES: CONCEPTS, MODELS, OBJECTIVES AND DEPENDABILITY PLANNING    | E.800–E.899        |
+| Terms and definitions related to the quality of telecommunication services                        | E.800–E.809        |
+| Models for telecommunication services                                                             | E.810–E.844        |
+| Objectives for quality of service and related concepts of telecommunication services              | E.845–E.859        |
+| Use of quality of service objectives for planning of telecommunication networks                   | E.860–E.879        |
+| Field data collection and evaluation on the performance of equipment, networks and services       | E.880–E.899        |
+
+*For further details, please refer to ITU-T List of Recommendations.*
+
+## **ITU-T RECOMMENDATION E.454**
+
+# **TRANSMISSION PERFORMANCE METRICS BASED ON ERROR CORRECTION MODE (ECM) FACSIMILE**
+
+## **Summary**
+
+The purpose of this Recommendation is to define transmission performance metrics based on Error Correction Mode (ECM) facsimile. Performance parameters defined in Recommendations E.451, E.452 and E.453 have been modified to accommodate the error correction and partial page characteristics of ECM facsimile. Performance parameters for ECM that will help infer the image quality for non-ECM transmissions have also been defined.
+
+The parameters defined in this Recommendation are intended for use when intrusive text techniques are employed.
+
+### **Source**
+
+ITU-T Recommendation E.454 was prepared by ITU-T Study Group 2 (1993-1996) and was approved under the WTSC Resolution No. 1 procedure on the 8th of October 1996.
+
+## FOREWORD
+
+ITU (International Telecommunication Union) is the United Nations Specialized Agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the ITU. The ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis.
+
+The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics.
+
+The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Resolution No. 1 (Helsinki, March 1-12, 1993).
+
+In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC.
+
+## NOTE
+
+In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+© ITU 1997
+
+All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU.
+
+## CONTENTS
+
+|   |                                                   | Page |
+|---|---------------------------------------------------|------|
+| 1 | Summary .....                                     | 1    |
+| 2 | References .....                                  | 1    |
+| 3 | Definitions .....                                 | 2    |
+| 4 | Abbreviations .....                               | 2    |
+| 5 | Introduction .....                                | 3    |
+| 6 | Frame size for ECM-based test calls .....         | 3    |
+| 7 | Facsimile call cut-off performance .....          | 3    |
+| 8 | Modem speed reductions and transaction time ..... | 4    |
+| 9 | Image quality metrics .....                       | 5    |
+
+
+
+# **TRANSMISSION PERFORMANCE METRICS BASED ON ERROR CORRECTION MODE (ECM) FACSIMILE**
+
+*(Geneva, 1996)*
+
+## **1 Summary**
+
+The purpose of this Recommendation is to define transmission performance metrics based on Error Correction Mode (ECM) facsimile. Performance parameters defined in Recommendations E.451, E.452 and E.453 have been modified to accommodate the error correction and Partial Page characteristics of ECM facsimile. Performance parameters for ECM that will help estimate the image quality for non-ECM transmissions have also been defined.
+
+The parameters defined in this Recommendation are intended for use when intrusive test techniques are employed. These metrics may be extended for use with non-intrusive test methodologies.
+
+ECM metrics for operation using V.34 modulation and the options for G3 terminals to operate at 64 kbit/s defined in Annex F/T.4 and Annex C/T.30 are for further study.
+
+The various parameters relating to Group 3 Facsimile terminal characteristics have been selected in order to provide a common basis for the measurement of the transmission performance of networks.
+
+The metrics defined in this Recommendation are not appropriate for the evaluation of the performance of facsimile terminals.
+
+## **2 References**
+
+The following Recommendations contain material that is either relevant to or provides background for this Recommendation.
+
+ITU-T Recommendation T.4 (1996), *Standardization of group 3 facsimile apparatus for document transmission*.
+
+ITU-T Recommendation T.30 (1996), *Procedures for document facsimile transmission in the general switched telephone network*.
+
+ITU-T Recommendation T.22 (1993), *Standardized test charts for document facsimile transmissions*.
+
+ITU-T Recommendation F.182 (1993), *Operational provisions for the international public facsimile service between subscribers' stations with group 3 facsimile machines (telefax 3)*.
+
+ITU-T Recommendation E.450 (1993), *Facsimile quality of service on PSTN – General aspects*.
+
+ITU-T Recommendation E.451 (1993), *Facsimile call cut-off performance*.
+
+ITU-T Recommendation E.452 (1993), *Facsimile modem speed reduction and transaction time*.
+
+ITU-T Recommendation E.453 (1994), *Facsimile image quality as corrupted by transmission-induced scan line errors*.
+
+ITU-T Recommendation E.456 (1994), *Test transactions for facsimile transmission performance*.
+
+ITU-T Recommendation E.457 (1996), *Facsimile measurement methodologies*.
+
+## 3 Definitions
+
+For the purposes of this Recommendation, the definitions given in Recommendations E.450, E.451, E.452, E.453 and E.456 are applicable.
+
+## 4 Abbreviations
+
+For the purposes of this Recommendation, the following abbreviations are used.
+
+|      |                                   |
+|------|-----------------------------------|
+| ARQ  | Automatic Repeat Request          |
+| CFR  | Confirmation to Receive           |
+| CPE  | Customer Premises Equipment       |
+| CRP  | Command Repeat                    |
+| CTC  | Continue To Correct               |
+| CTR  | Response to Continue to Correct   |
+| DCS  | Digital Command Signal            |
+| ECM  | Error Correction Mode             |
+| EOM  | End of Message                    |
+| EOP  | End of Procedure                  |
+| EOR  | End of Retransmission             |
+| ERR  | Response to End of Retransmission |
+| FCD  | Facsimile Coded Data              |
+| FCS  | Frame Check Sequence              |
+| FTT  | Failure to Train                  |
+| HDLC | High-Level Data Link Control      |
+| MCF  | Message Confirmation              |
+| MPS  | Multipage Signal                  |
+| PP   | Partial Page                      |
+| PPR  | Partial Page Request              |
+| PPS  | Partial Page Signal               |
+| PSTN | Public Switched Telephone Network |
+| RCP  | Return to Control Partial Page    |
+| RNR  | Receiver Not Ready                |
+| RR   | Receiver Ready                    |
+| RTC  | Return To Control                 |
+| RTN  | Retrain Negative                  |
+| RTP  | Retrain Positive                  |
+
+## 5 Introduction
+
+The purpose of this Recommendation is to define transmission performance metrics based on Error Correction Mode (ECM) facsimile.
+
+ECM facsimile has been defined in Annex A/T.4 and Annex A/T.30. The error correction is based on half-duplex page selective repeat ARQ (automatic repeat request) technique. An HDLC frame structure is utilized for all binary coded facsimile message procedures. The basic HDLC structure consists of a number of frames each of which is subdivided into a number of fields. These fields provide for frame labelling and error checking.
+
+A facsimile page is divided into Partial Pages (PPs) consisting of up to 256 Facsimile Coded Data (FCD) frames and three Return to Control Partial Page (RCP) frames. Each FCD frame has a frame number field as well as a Frame Check Sequence (FCS). Two options are recognized for the FCD frames: The Facsimile Data Field may have a length of either 256 or 64 octets. The last PP may have less than 256 FCD frames and the last frame (including RTC) may have less than 256 or 64 octets. The choice of 256- or 64-octet frame size is made by the transmitter and communicated to the receiver via the DCS command (bit 28).
+
+The transmitter sends one of a set of PPS messages at the end of a Partial Page. When an errored frame is declared by the receiver, it transmits a Partial Page Request (PPR) to the transmitter to indicate that the frames specified in the associated facsimile information field need to be retransmitted. When the PPR is received, the transmitting station retransmits the requested frames. If the PPR is received four times in the same block, either the End of Retransmission (EOR) for end of Retransmission or Continue to Correct (CTC) is sent for continuing the transmission.
+
+In the following clauses, the facsimile performance parameters for ECM facsimile are discussed. ECM facsimile performance can be used to derive an estimate of the image quality of non-ECM facsimile and we specify how this could be accomplished.
+
+## 6 Frame size for ECM-based test calls
+
+Test calls for ECM facsimile can use either the 256- or 64-octet frame size.
+
+It is recommended that the 256-octet frame size be chosen if the test calls are intended to evaluate:
+
+- 256-octet ECM transmissions and/or;
+- error-free page image quality metric only for non-ECM facsimile (from ECM facsimile).
+
+The 256-octet choice means that  $256 \times 8 \times 256 = 524\,288$  bits of facsimile coded data can be transmitted in one Partial Page or block. A Partial Page of this size is sufficient to accommodate a T.22 Test Chart No. 4 (or the older T.21 Test Chart No. 2). This is helpful because ECM metrics defined in clause 9 b) and 9 c) closely correspond to the error-free page metrics defined in E.453 for non-ECM facsimile.
+
+The 64-octet frame size may be used if the intent is to evaluate:
+
+- 64-octet ECM transmissions and/or;
+- a more fine-grained assessment of Image quality metrics for non-ECM facsimile (from ECM facsimile) including an approximate evaluation of Severely Errored pages.
+
+## 7 Facsimile call cut-off performance
+
+Recommendation E.451 defines performance parameters for facsimile call cut-offs. Most of the definitions in clause 3/E.451 apply to cut-off performance of ECM facsimile without any modifications and others require some modification:
+
+- a) A pre-message phase B failure is considered to have occurred if prior to the transmission of the first page, either the originating or the terminating facsimile terminal goes on-hook prior to the reception of CFR message by the originating terminal.
+
+A post-message phase B failure is considered to have occurred if a phase B failure occurs after the transmission of any Partial Page.
+
+- b) A phase C/phase D failure at any Partial Page is considered to have occurred:
+
+- if a valid post message response (MCF, PPR, CTR, ERR, RNR) is not received in response to PPS-NULL, PPS-EOM, PPS-MPS, PPS-EOP, PPS-PRI-Q; CTC, EOR-NULL, EOR-EOM, EOR-MPS, EOR-EOP, EOR-PRI-Q; RR, and CRP;
+- if the transmitter aborts the transmission after receiving PPR for the fourth time;
+- if the timer  $T_5$  (which is reset at the beginning of the receipt of the first RNR from the receiver and has a limit of  $60 \pm 5$  s) elapses.
+
+Facsimile call cut-off ratios for test calls have been defined in Recommendation E.451. In clause 2/E.451, the conditions that apply to test calls have been established. These conditions apply to test calls in the ECM mode also. The size of the ECM test transactions shall be the same as for non-ECM transactions as specified in Recommendation E.456.
+
+One key performance parameter for cut-off ratios defined in Recommendation E.451 is shown here:
+
+$$\% C_N = (F_N / T) * 100$$
+
+Where  $F_N$  is the number of N-Partial Page test transactions ( Recommendation E.456) where there was a phase B, C or D failure, and T is the total number of test transactions that satisfy all the requirements stated in clause 2/E.451. (N is chosen to be 5 for the 256-octet frame size and 20 for the 64-octet frame size.)
+
+Facsimile cut-off ratios for m Partial Pages ( $1 \leq m \leq N$ ) is:
+
+$$\% C_m = (F_m / T) * 100$$
+
+Where  $F_m$  is the number of transactions that had a phase B, C or D failure at the  $m^{\text{th}}$  Partial Page.
+
+Other metrics associated with cut-offs for ECM transmission follow the definitions in E.451.
+
+Note the following difference between the call cut-off performance of ECM and non-ECM transmissions. For ECM transmissions, the modems must train more often if there are PPRs and associated frame retransmissions. Therefore, there are more chances for call cut-offs if the network impairments are such that the training sequences are affected.
+
+## 8 Modem speed reductions and transaction time
+
+Performance parameters for modem speed reduction and transaction time for non-ECM transmissions have been defined in Recommendation E.452. There are some differences in the manner in which speed reductions take place for ECM transmissions when compared to non-ECM transmissions:
+
+- For both ECM and non-ECM transmissions, speed reductions can take place during Phase B negotiations. In this case, speed reductions take place until a CFR is transmitted by the receiver to the transmitter confirming that the TCF has been received at an acceptable error level.
+- For ECM transmissions, additional speed reductions can take place if four PPRs have been received in the same block and the transmitter chooses to fall back in speed. This is similar
+
+to but different from the speed fallback in non-ECM transmissions that may occur in response to RTP or RTN responses from the receiver.
+
+- a) A key performance parameter is the percentage of calls without modem speed reduction from the initial agreed upon speed  $S_i$  (see clause 1/E.452):
+
+$$\% C_1 = C_1 / T_C * 100$$
+
+where  $T_C$  is the total number of completed test calls.
+
+- b) Partial Page based metrics can be defined by the number of Partial Pages at speed  $S_n(N_{Sn})$  for  $S_n = S_i, S_{i-1}, S_{i-2}$ , etc. This parameter can be expressed as a percentage of the total number of pages associated with completed transactions ( $N_t$  which is equal to  $5 * T_C$  for test transactions defined in Recommendation E.456).
+
+$$\% N_{Si,Sn} = N_{Sn} / N_t * 100$$
+
+- c) The definition of Transaction Efficiency rating follows the definition in Recommendation E.452 except that pages are replaced by Partial Pages.
+- d) Transaction time
+
+For ECM transmissions, the transaction time is affected by several factors:
+
+- Transaction times are significantly affected by the choice of the frame size. In the 64-octet mode there are more turn-arounds and more overhead per page because the Partial Pages are smaller in size.
+- In ECM, the receiver may transmit RNR for flow control to clear up congestion at the receiver. The transmitter responds by sending RR queries which are acknowledged by RNR or MCF. This exchange can take place up to the limit of the  $T_5$  timer of  $60 \pm 5$ s. Both test call-based and non-intrusive monitoring could capture this additional delay. Note however that this increase in transaction time is caused by CPE effects and not the network.
+
+Following Recommendation E.452, we define transaction time for completed transactions without modem speed reductions below  $S_i$  ( $T_{t1}$ ): this is the average transaction time of all completed transactions without any modem speed reductions. The value of this parameter should be reported separately for the 256- and 64-octet frame size, for transactions with and without RNR-RR sequence, etc.
+
+It may also be useful to measure the percentage of completed transactions that have RNR-RR sequences as a percentage of total transactions, the average duration of RNR-RR sequence times, etc. These metrics will be explored in a future Recommendation on non-intrusive measurements.
+
+## 9 Image quality metrics
+
+ECM transmissions are intended to produce error-free images. It is however possible to derive an estimate of the ability of networks to carry Error-Free images by examining the fraction of transactions that do not have PPR requests from the receiver.
+
+- a) Calls without any PPR requests (Error-Free calls)
+
+$C_{NPPR}$  is the number of completed transactions that had no PPRs.
+
+Then represented as a percentage of  $T_C$ , where  $T_C$  is the number of completed transactions in the test,
+
+$$\% C_{NPPR} = (C_{NPPR} / T_C) * 100$$
+
+- b) Number of Partial Pages without any PPR requests
+
+$P_{\text{NPPR}}$  is the total number of Partial Pages without any PPR in  $T_C$  completed transactions.
+
+Then represented as a percentage of the total number of Partial Pages ( $N$ ) in  $T_C$  completed test transactions,
+
+$$\% P_{\text{NPPR}} = (P_{\text{NPPR}} / N) * 100$$
+
+- c) Number of Pages without any PPR requests
+
+$P_{\text{GPPR}}$  is the total number of Pages without any PPR messages in  $T_C$  completed transactions.
+
+Then represented as a percentage of the total number of pages ( $N_P$ ) in  $T_C$  completed transactions,
+
+$$\% P_{\text{GPPR}} = (P_{\text{GPPR}} / N_P) * 100$$
+
+- d) Per cent Frame Error Rate
+
+Frame Error Rate is defined as:
+
+$$\text{FRER} = \text{EFR} / \text{TFR}$$
+
+where EFR is the number of errored frames that are requested for retransmissions (including repeat retransmissions) and TFR is the total number of frames transmitted including retransmissions. FRER closely represents the facsimile modem Block Error Rate for 2048-bit and 512-bit blocks for the 256-octet and 64-octet frame sizes, respectively.
+
+- e) The use of ECM does not guarantee that images will not be degraded due to transmission errors under severe conditions. The following metric could serve as an indicator of transactions with severely degraded image quality.
+
+Per cent of Completed Transactions with one or more EOR message. A transaction with an EOR message will produce degraded images at the receiving terminal.
+
+Per cent EOR is defined as:
+
+$$\% N_{\text{EOR}} = (N_{\text{EOR}} / T_C) * 100$$
+
+where  $N_{\text{EOR}}$  is the number of completed transactions with one or more EOR message.
+
+- f) Calls with PPRs on consecutive frames
+
+For further study (Note).
+
+NOTE – Calls with PPRs in consecutive frames may provide a measure of calls with Severely-Errored pages in non-ECM transmissions. This is for further study.
+
+# ITU-T RECOMMENDATIONS SERIES
+
+- Series A Organization of the work of the ITU-T
+- Series B Means of expression
+- Series C General telecommunication statistics
+- Series D General tariff principles
+- Series E Telephone network and ISDN**
+- Series F Non-telephone telecommunication services
+- Series G Transmission systems and media
+- Series H Transmission of non-telephone signals
+- Series I Integrated services digital network
+- Series J Transmission of sound-programme and television signals
+- Series K Protection against interference
+- Series L Construction, installation and protection of cables and other elements of outside plant
+- Series M Maintenance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits
+- Series N Maintenance: international sound-programme and television transmission circuits
+- Series O Specifications of measuring equipment
+- Series P Telephone transmission quality
+- Series Q Switching and signalling
+- Series R Telegraph transmission
+- Series S Telegraph services terminal equipment
+- Series T Terminal equipment and protocols for telematic services
+- Series U Telegraph switching
+- Series V Data communication over the telephone network
+- Series X Data networks and open system communication
+- Series Z Programming languages

marked/E/T-REC-E.457-199602-I_PDF-E/raw.md

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+
+
+![ITU logo: A globe with a lightning bolt and the letters ITU.](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg)
+
+ITU logo: A globe with a lightning bolt and the letters ITU.
+
+INTERNATIONAL TELECOMMUNICATION UNION
+
+**ITU-T**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+**E.457**
+
+(02/96)
+
+**TELEPHONE NETWORK AND ISDN  
+QUALITY OF SERVICE, NETWORK MANAGEMENT  
+AND TRAFFIC ENGINEERING**
+
+---
+
+**FACSIMILE MEASUREMENT  
+METHODOLOGIES**
+
+**ITU-T Recommendation E.457**
+
+(Previously "CCITT Recommendation")
+
+---
+
+# FOREWORD
+
+The ITU-T (Telecommunication Standardization Sector) is a permanent organ of the International Telecommunication Union (ITU). The ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis.
+
+The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics.
+
+The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Resolution No. 1 (Helsinki, March 1-12, 1993).
+
+ITU-T Recommendation E.457 was prepared by ITU-T Study Group 2 (1993-1996) and was approved under the WTSC Resolution No. 1 procedure on the 19th of February 1996.
+
+---
+
+# NOTE
+
+In this Recommendation, the expression “Administration” is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+# CONTENTS
+
+|                                                                                 | <i>Page</i> |
+|---------------------------------------------------------------------------------|-------------|
+| 1 References .....                                                              | 1           |
+| 2 Definitions.....                                                              | 1           |
+| 3 Abbreviations .....                                                           | 1           |
+| 4 Introduction.....                                                             | 1           |
+| 5 Measurement methodologies.....                                                | 2           |
+| 5.1 Test calls .....                                                            | 2           |
+| 5.2 Non-intrusive measurements .....                                            | 3           |
+| 5.3 Mixed mode measurements .....                                               | 4           |
+| 5.4 Terminal based measurements.....                                            | 4           |
+| 6 Test planning.....                                                            | 4           |
+| 7 Statistical aspects.....                                                      | 5           |
+| Annex A – Estimation of sample sizes for facsimile performance parameters ..... | 5           |
+
+# **SUMMARY**
+
+This Recommendation discusses various facsimile measurement methodologies focusing on G3 facsimile as defined by Recommendations T.4, T.6, T.30 and used on PSTN as defined by Recommendations F.180 and F.182. The Recommendation evaluates the advantages and disadvantages of intrusive (test-call based), non-intrusive, mixed-mode and terminal based measurements. Test planning aspects including planning approach, measurement topology, test location points, and some statistical aspects are also discussed.
+
+# **FACSIMILE MEASUREMENT METHODOLOGIES**
+
+*(Geneva, 1996)*
+
+# **1 References**
+
+The following Recommendations contain material relevant to this Recommendation.
+
+- ITU-T Recommendation T.4 (1993), *Standardization of Group 3 facsimile apparatus for document transmission*.
+- CCITT Recommendation T.6 (1988), *Facsimile coding schemes and coding control functions for Group 4 facsimile apparatus*.
+- ITU-T Recommendation T.30 (1993), *Procedures for document facsimile transmission in the general switched telephone network*.
+- ITU-T Recommendation F.182 (1993), *Operational provisions for the international public facsimile service between subscribers' stations with Group 3 facsimile machines (telefax 3)*.
+- ITU-T Recommendation E.450 (1993), *Facsimile quality of service on PSTN – General aspects*.
+- ITU-T Recommendation E.451 (1993), *Facsimile call cut-off performance*.
+- ITU-T Recommendation E.452 (1993), *Facsimile modem speed reductions and transaction time*.
+- ITU-T Recommendation E.453 (1994), *Facsimile image quality as corrupted by transmission-induced scan line errors*.
+- ITU-T Recommendation E.456 (1994), *Test transaction for facsimile transmission performance*.
+
+# **2 Definitions**
+
+For the purposes of this Recommendation the definitions given in Recommendations E.450, E.451, E.452 and E.453 will be applicable.
+
+# **3 Abbreviations**
+
+A glossary is presented in Recommendation E.450.
+
+# **4 Introduction**
+
+The intent of this Recommendation is to provide an overview of facsimile measurement methodologies, their advantages and disadvantages, test planning and statistical aspects of measurements.
+
+The measurement of facsimile service quality of networks can be accomplished by a variety of techniques including:
+
+- 4.1** Intrusive test-call-based measurements using test machines meeting certain minimum requirements will be developed in the future.
+- 4.2** Non-intrusive measurements based on live customer traffic monitored at a network interface using measurement equipment meeting certain minimum requirements will be defined in the future.
+- 4.3** Mixed mode measurements involving test calls utilizing non-intrusive (protocol and analogue signal) monitoring for trouble shooting.
+- 4.4** Terminal based measurements obtained from terminal reports meeting certain technical requirements.
+
+In the following, we discuss these measurement methodologies in some detail.
+
+# 5 Measurement methodologies
+
+### 5.1 Test calls
+
+Measurements using test-call-based methodology are typically carried out over an end-to-end path. The general test topology is shown in Figure 1. Usually, the test calls interface the network at a point similar to that of a typical subscriber.
+
+It is recommended that the test calls follow the prescriptions listed below:
+
+- 5.1.1 Test calls use test transactions defined in Recommendation E.456.
+- 5.1.2 Performance parameters be measured as specified in Recommendations E.451, E.452, and E.453.
+- 5.1.3 Test machines satisfy the minimum requirements. (To be developed.)
+- 5.1.4 Statistical requirements are met (see clause 7).
+
+![Diagram of intrusive measurement topology showing a sequence of network components: Fax test apparatus, CO, TS, ISC, ISC, TS, CO, and Fax test apparatus. Connections are labeled 2 W or 4 W. Arrows indicate the National network and International network segments.](573c8f9e728e343b6864e1070c14b8cf_img.jpg)
+
+The diagram illustrates an intrusive measurement topology. It consists of a series of network components connected in a linear sequence. At each end, a 'Fax test apparatus' is connected via a '2 W' (2-wire) interface to a 'CO' (Central office). The 'CO' is connected to a 'TS' (Toll switch) via a '4 W' (4-wire) interface. The 'TS' is connected to an 'ISC' (International switching centre) via a '4 W' interface. The two 'ISC' units are connected to each other via a '4 W' interface. This central segment, consisting of the two 'ISC' units and the '4 W' link between them, is labeled as the 'International network'. The first 'TS' and 'CO' are connected to the first 'ISC' via '4 W' interfaces. The second 'ISC' is connected to the second 'TS' via a '4 W' interface. The second 'TS' is connected to the second 'CO' via a '4 W' interface. The second 'CO' is then connected to the second 'Fax test apparatus' via a '2 W' interface. Arrows point from the labels 'National network' and 'International network' to the appropriate parts of the diagram. A reference code 'T0204930-95/d01' is present in the bottom right corner of the diagram area.
+
+2 W 2 wire  
+4 W 4 wire  
+CO Central office  
+TS Toll switch  
+ISC International switching centre
+
+Diagram of intrusive measurement topology showing a sequence of network components: Fax test apparatus, CO, TS, ISC, ISC, TS, CO, and Fax test apparatus. Connections are labeled 2 W or 4 W. Arrows indicate the National network and International network segments.
+
+FIGURE 1/E.457  
+Example of intrusive measurement topology
+
+#### 5.1.5 Remarks
+
+- a) Test calls provide a means for end-to-end performance characterization of networks in a controlled fashion.
+- b) Test calls can be used for the comparison of performance of specific network services, network technologies, customer premises equipment, etc.
+- c) Test calls are one of the faster methods of trouble-shooting a network problem or a network/terminal interaction problem.
+- d) Test calls are costly in the sense that they use up network resources for testing purposes.
+- e) Test calls provide only a limited view of the geographical diversity since it is usually not possible to provide and maintain a large number of test access points. From practical considerations, the test access points are located in major communication centres which presumably have a higher quality network performance than, say, the outlying areas.
+- f) Test calls tend to produce performance results that are in general better than that observed in non-intrusive measurements because the impact of customer CPE malfunctioning and incompatibilities, poor quality access and egress networks, etc. is usually avoided.
+
+- g) When conducting network tests, the prevailing conditions should be known to the maximum possible extent. For example, if the comparative performance of different media is being assessed, the network should be in its nominal state. If abnormal conditions occur (e.g. network under restoration) during tests, this data should be analysed separately.
+
+### 5.2 Non-intrusive measurements
+
+Usually, non-intrusive measurement systems monitor the performance of facsimile calls at a network concentration point such as a switch (Figure 2). However, it is possible to monitor facsimile performance non-intrusively at any point in the connection with the appropriate interface. In general, non-intrusive monitoring provides an end-to-end view of facsimile performance regardless of the measurement point. Some network equipment with FAX DEMOD and REMOD may be provisioned so that the G3 fax protocol messages are intentionally altered (e.g. limit the maximum speed) and the characteristics of facsimile transactions are changed as a result. In this case, the measurements should be analysed taking into account the effects of such equipment.
+
+5.2.1 It is recommended that non-intrusive measurements be conducted using facsimile performance parameters that will be defined in the future.
+
+![Diagram of non-intrusive measurement topology showing a path from customer fax machines through CO, TS, ISC, ISC, TS, and CO switches, with a measurement system connected to the CO and TS switches. The diagram includes labels for 2W and 4W interfaces, National network, and International network. A legend defines the abbreviations: 2 W (2 wire), 4 W (4 wire), CO (Central office), TS (Toll switch), and ISC (International switching centre).](49ee89a1d5852ab005dbbab6de09a8a6_img.jpg)
+
+The diagram illustrates a non-intrusive measurement topology. It shows a sequence of network components connected in series: a Customer fax machine (2 W) connected to a Central Office (CO), which is connected to a Toll switch (TS) via a 4 W interface. The TS is part of a National network and is connected to an International switching centre (ISC). The first ISC is connected to another ISC, which is then connected to another TS (part of the National network), which is finally connected to another CO (2 W) and then to another Customer fax machine. A 'Non-intrusive fax measurement system' is shown with lines connecting it to the CO and TS switches, indicating the points where measurements are taken. The diagram is labeled with 'National network' and 'International network' to distinguish between different types of network segments. A reference code 'T0204940-95/d02' is present in the bottom right corner of the diagram area.
+
+2 W 2 wire  
+4 W 4 wire  
+CO Central office  
+TS Toll switch  
+ISC International switching centre
+
+Diagram of non-intrusive measurement topology showing a path from customer fax machines through CO, TS, ISC, ISC, TS, and CO switches, with a measurement system connected to the CO and TS switches. The diagram includes labels for 2W and 4W interfaces, National network, and International network. A legend defines the abbreviations: 2 W (2 wire), 4 W (4 wire), CO (Central office), TS (Toll switch), and ISC (International switching centre).
+
+FIGURE 2/E.457  
+Example of non-intrusive measurement topology
+
+#### 5.2.2 Remarks
+
+- Non-intrusive measurements provide a means for characterizing the end-to-end service quality of networks, including a variety of CPE interactions, customer settings and malfunctions.
+- Depending on the capabilities of the equipment, non-intrusive measurements could also provide a comparison of the performance of specific network services, network technologies, CPE, etc.
+- Such measurements are usually able to gather data quickly and in large volumes once the network arrangements for the data collection are completed. The ability to capture data is a function of the fax traffic volume and the number of channels that can be monitored simultaneously.
+- Measurement costs are limited to costs for data collection and analysis, and network resources are not tied up for the purposes of testing.
+- Measurements can provide a general view of tail network conditions depending on where the measurement point is located. If it is possible to associate the per call performance measurements with calling and called numbers, it is possible to obtain a very detailed view of tail network performances.
+
+- f) Measurements produce results that are in general worse than those observed in test-call based measurements because of the CPE malfunctioning and incompatibilities, poor quality access and egress networks, etc.
+- g) While non-intrusive measurements offer certain advantages, they do not permit the level of control that can be achieved using the test call methodology. For example, when sending test calls all transactions can use test transactions defined in Recommendation E.456 providing a very controlled test stimulus. Such control is not possible for non-intrusive measurements.
+- h) When non-intrusive monitoring is conducted at a network concentration point, image quality parameters defined in Recommendation E.453 cannot be evaluated directly. However, ECM based metrics could be characterized which could serve as a surrogate for the image quality parameters defined in Recommendation E.453. Additionally, analysis of RTN and RTP signals can be used to give a general picture of image degradation due to transmission errors.
+
+### 5.3 Mixed mode measurements
+
+Mixed mode measurements may be used for specialized purposes such as trouble-shooting. In this case, test calls are launched from a test apparatus which could include a facsimile machine that is having problems of some kind. Non-intrusive equipment could be as simple as a T.30 protocol analyser or could be a more complex device capable of performing both T.30 and analogue signal characteristic measurements.
+
+There are no specific requirements that pertain to these types of trouble-shooting measurements except that the measurements be technically sound.
+
+### 5.4 Terminal based measurements
+
+Facsimile terminals are capable of producing a variety of terminal reports indicating the success/failure of calls, call duration, some protocol information for failed calls, etc. The number and selection of items varies by manufacturer and model. These reports are more useful than having no information at all. However, there are no ITU standards for how this information is gathered by the machine. Therefore, caution should be exercised in interpreting the data from terminal reports. This is especially true for transaction times reported by terminals where considerable variations exist in the calculation of this parameter.
+
+# 6 Test planning
+
+Planning of a facsimile performance study should include careful consideration of the goals of the study, primary factors that are planned to be studied, secondary factors, interactions, statistical aspects, etc.
+
+- a) The tests must be planned such that the results for the primary factors can be obtained without confounding those factors. In formulating the test plan, interactions that are likely to arise must be identified beforehand and the interpretations of the test results must include the possible effects of these interactions. For example, when comparing the facsimile performance on two types of transport media on the international segment, it is important to keep the tail network conditions as similar.
+- b) Secondary factors such as time of day can often be important in network tests because the load on the networks, routing, etc. can be different during different periods. The sample plan should include these factors if it is likely that the results and their interpretation would be affected substantially.
+- c) It is often useful to conduct a pilot study with a smaller sample size prior to conducting the full study. The pilot study can often provide guidance on what factors are important, what are the likely problems to be encountered or what the statistical considerations are likely to be, etc.
+- d) Test machines used for intrusive testing should be carefully selected so that they have no known incompatibility problems, are representative of the facsimile terminal base, etc. They should meet the requirements which will be specified in the future.
+
+# 7 Statistical aspects
+
+Results of facsimile performance tests must be statistically valid and special care must be exercised to ensure that a sufficient number of samples are collected and the correct statistical analysis is employed. Depending on the questions to be studied, the test hypothesis must be formulated and the sample size estimates developed. There are a variety of texts that are available for this purpose and some of them are listed in the references. As an example, the sample size for estimating facsimile call cut-off ratios at a given level of accuracy is presented in Annex A. Additional details on statistical questions are proposed to be included in the facsimile QOS Handbook.
+
+# Annex A
+
+## Estimation of sample sizes for facsimile performance parameters
+
+(This annex forms an integral part of this Recommendation)
+
+The E-Series Recommendations “E.451: Facsimile call cut-off performance”, “E.452: Facsimile modem speed reductions and transaction time” and “E.453: Facsimile image quality as corrupted by transmission-induced scan line errors” define and formulate a number of dichotomous parameters expressed in terms of percentages. These parameters are frequently estimated by conducting field studies. To ensure the statistical validity of the end result, planners of facsimile field studies need to determine the minimum number of test calls (sample size) before conducting the experiment. Mathematically, this problem is classified under the statistical theory of determining the sample size,  $n$ , necessary to estimate the parameter of interest  $P$  with pre-specified margins of error,  $\Delta$  at a given confidence level  $\beta$ . This annex provides a simple, practical stepwise procedure for determining the sample size  $n$ .
+
+#### Procedure
+
+The procedure will consist of the following six steps:
+
+- Step 1: Specify the proportion (percentage)  $P$  that needs to be estimated.
+- Step 2: Using past experience determine an estimated value for the parameter  $P$  and call it  $P_0$ .
+- Step 3: Specify the error tolerance limits (margins of error),  $\Delta$  and the desired confidence level  $\beta$  (in practice usually one of the two confidence levels of  $\beta = 90\%$  or  $\beta = 95\%$  are used).
+- Step 4: Using the desired confidence level,  $\beta$ , select the appropriate chart from an appropriate statistics reference, e.g. “Volume 12, How to Choose the Proper Sample Size, American Society for Quality Control, Statistics Division”.
+- Step 5: Using the acceptable margin of error,  $\Delta$ , determine the appropriate curve on the selected chart.
+- Step 6: Using the  $P_0$  as the value on the abscissa on the selected chart, determine the minimum sample size,  $n$ .
+
+#### Illustration
+
+A field study is being planned to estimate the facsimile call cut-off ratios for the facsimile service from location A to location B. The investigator requires a margin of error no more than  $\Delta = 5\%$  at a confidence level of  $\beta = 90\%$ . It is estimated from past experience that the facsimile call success ratio for the facsimile service from location A to location B is 90%, i.e.  $P_0 = 10\%$ . Then, the sample size is determined by the ordinate of the curve  $\Delta = 5$  at the abscissa of  $P_0 = 10$ , see Figure A.1. This results in a sample of size  $n = 100$  facsimile calls.
+
+NOTE – The above procedures are designed for dichotomous parameters. For continuous parameters, such as transaction time, different procedures are needed. The reason is that the mathematical formulae derived for the dichotomous parameters do not apply directly to continuous parameters. Details for continuous parameters and other statistical issues will be found in the Handbook of Facsimile QOS.
+
+![A log-log graph showing the relationship between sample size and estimated proportion for a 90% confidence level. The y-axis is 'Sample size' from 10 to 5000. The x-axis is 'Estimated P0 in per cent' from 0.1 to 10. Six curves are shown for Δ = 1, 2, 3, 4, 5, and 6. The curves show that as the estimated proportion increases, the required sample size also increases. For a given proportion, the sample size decreases as Δ increases.](adb1f42239329fa8283d1a40005f989f_img.jpg)
+
+Estimating one proportion  
+90% Confidence Level
+
+T0204950-95/d03
+
+A log-log graph showing the relationship between sample size and estimated proportion for a 90% confidence level. The y-axis is 'Sample size' from 10 to 5000. The x-axis is 'Estimated P0 in per cent' from 0.1 to 10. Six curves are shown for Δ = 1, 2, 3, 4, 5, and 6. The curves show that as the estimated proportion increases, the required sample size also increases. For a given proportion, the sample size decreases as Δ increases.
+
+FIGURE A.1/E.457  
+**Minimum sample size**

marked/E/T-REC-E.500-199811-I_PDF-E/raw.md

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+
+
+![ITU logo: A globe with the letters ITU and a lightning bolt.](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg)
+
+ITU logo: A globe with the letters ITU and a lightning bolt.
+
+INTERNATIONAL TELECOMMUNICATION UNION
+
+**ITU-T**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+**E.500**
+
+(11/98)
+
+SERIES E: OVERALL NETWORK OPERATION,  
+TELEPHONE SERVICE, SERVICE OPERATION AND  
+HUMAN FACTORS
+
+Quality of service, network management and traffic  
+engineering – Traffic engineering – Measurement and  
+recording of traffic
+
+# --- **Traffic intensity measurement principles**
+
+ITU-T Recommendation E.500
+
+(Previously CCITT Recommendation)
+
+---
+
+## OVERALL NETWORK OPERATION, TELEPHONE SERVICE, SERVICE OPERATION AND HUMAN FACTORS
+
+## **OPERATION, NUMBERING, ROUTING AND MOBILE SERVICES**
+
+## INTERNATIONAL OPERATION
+
+|                                                        |             |
+|--------------------------------------------------------|-------------|
+| Definitions                                            | E.100–E.103 |
+| General provisions concerning Administrations          | E.104–E.119 |
+| General provisions concerning users                    | E.120–E.139 |
+| Operation of international telephone services          | E.140–E.159 |
+| Numbering plan of the international telephone service  | E.160–E.169 |
+| International routing plan                             | E.170–E.179 |
+| Tones in national signalling systems                   | E.180–E.199 |
+| Maritime mobile service and public land mobile service | E.200–E.229 |
+
+## OPERATIONAL PROVISIONS RELATING TO CHARGING AND ACCOUNTING IN THE INTERNATIONAL TELEPHONE SERVICE
+
+|                                                                |             |
+|----------------------------------------------------------------|-------------|
+| Charging in the international telephone service                | E.230–E.249 |
+| Measuring and recording call durations for accounting purposes | E.260–E.269 |
+
+## UTILIZATION OF THE INTERNATIONAL TELEPHONE NETWORK FOR NON-TELEPHONY APPLICATIONS
+
+|                 |             |
+|-----------------|-------------|
+| General         | E.300–E.319 |
+| Phototelegraphy | E.320–E.329 |
+
+## ISDN PROVISIONS CONCERNING USERS
+
+|             |
+|-------------|
+| E.330–E.399 |
+|-------------|
+
+## **QUALITY OF SERVICE, NETWORK MANAGEMENT AND TRAFFIC ENGINEERING**
+
+## NETWORK MANAGEMENT
+
+|                                                             |             |
+|-------------------------------------------------------------|-------------|
+| International service statistics                            | E.400–E.409 |
+| International network management                            | E.410–E.419 |
+| Checking the quality of the international telephone service | E.420–E.489 |
+
+## TRAFFIC ENGINEERING
+
+|                                                                                   |                    |
+|-----------------------------------------------------------------------------------|--------------------|
+| <b>Measurement and recording of traffic</b>                                       | <b>E.490–E.505</b> |
+| Forecasting of traffic                                                            | E.506–E.509        |
+| Determination of the number of circuits in manual operation                       | E.510–E.519        |
+| Determination of the number of circuits in automatic and semi-automatic operation | E.520–E.539        |
+| Grade of service                                                                  | E.540–E.599        |
+| Definitions                                                                       | E.600–E.699        |
+| ISDN traffic engineering                                                          | E.700–E.749        |
+| Mobile network traffic engineering                                                | E.750–E.799        |
+
+## QUALITY OF TELECOMMUNICATION SERVICES: CONCEPTS, MODELS, OBJECTIVES AND DEPENDABILITY PLANNING
+
+|                                                                                             |             |
+|---------------------------------------------------------------------------------------------|-------------|
+| Terms and definitions related to the quality of telecommunication services                  | E.800–E.809 |
+| Models for telecommunication services                                                       | E.810–E.844 |
+| Objectives for quality of service and related concepts of telecommunication services        | E.845–E.859 |
+| Use of quality of service objectives for planning of telecommunication networks             | E.860–E.879 |
+| Field data collection and evaluation on the performance of equipment, networks and services | E.880–E.899 |
+
+# **TRAFFIC INTENSITY MEASUREMENT PRINCIPLES**
+
+## **Summary**
+
+This Recommendation describes traffic intensity concepts and traffic intensity measurement methodologies. The concepts of normal and high load are described and the methodology for using these measured traffic intensities in determining the load for traffic system dimensioning is discussed.
+
+###### **Source**
+
+ITU-T Recommendation E.500 was revised by ITU-T Study Group 2 (1997-2000) and was approved under the WTSC Resolution No. 1 procedure on the 9th of November 1998.
+
+## FOREWORD
+
+ITU (International Telecommunication Union) is the United Nations Specialized Agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the ITU. The ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis.
+
+The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics.
+
+The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Resolution No. 1.
+
+In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC.
+
+## NOTE
+
+In this Recommendation the term *recognized operating agency (ROA)* includes any individual, company, corporation or governmental organization that operates a public correspondence service. The terms *Administration*, *ROA* and *public correspondence* are defined in the *Constitution of the ITU (Geneva, 1992)*.
+
+## INTELLECTUAL PROPERTY RIGHTS
+
+The ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. The ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process.
+
+As of the date of approval of this Recommendation, the ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database.
+
+© ITU 1999
+
+All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU.
+
+## CONTENTS
+
+|                                                                                                            | Page |
+|------------------------------------------------------------------------------------------------------------|------|
+| 1 Scope .....                                                                                              | 1    |
+| 2 References .....                                                                                         | 1    |
+| 3 Definitions .....                                                                                        | 1    |
+| 4 Abbreviations .....                                                                                      | 2    |
+| 5 Traffic intensity concepts .....                                                                         | 2    |
+| 5.1 Background .....                                                                                       | 2    |
+| 5.2 Traffic intensity concept and stationarity .....                                                       | 3    |
+| 5.3 Assumptions for this Recommendation .....                                                              | 3    |
+| 5.4 Measured traffic intensity .....                                                                       | 4    |
+| 5.5 Convergence of the measured traffic intensity and choice of read-out period .....                      | 4    |
+| 6 Measurement methods and normal and high load traffic intensities .....                                   | 5    |
+| 6.1 Daily measurement methods .....                                                                        | 5    |
+| 6.2 Grouping of daily measurements .....                                                                   | 6    |
+| 6.3 Normal and high load traffic intensities .....                                                         | 6    |
+| 6.4 Considerations on service measurements .....                                                           | 7    |
+| 7 Determination of the traffic intensity values for resource dimensioning .....                            | 8    |
+| 8 History .....                                                                                            | 8    |
+| Annex A – Example of stationary traffic intensity with holding times larger than the read-out period ..... | 9    |
+
+
+
+# TRAFFIC INTENSITY MEASUREMENT PRINCIPLES
+
+(revised in 1998)
+
+## 1 Scope
+
+This Recommendation considers traffic intensity measurements for traffic systems consisting of a pool of resources and random arrival events that require the use of some amount of resources from the pool for some period of time. Traffic systems with and without waiting room (i.e. queueing) are considered. Only traffic systems with a pool of resources of a single type are considered. The defined traffic intensity measurements relate to the use of stationary arrival process models to characterize traffic over the measurement intervals.
+
+## 2 References
+
+The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; all users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published.
+
+- ITU-T Recommendation E.492 (1996), *Traffic reference period*.
+- ITU-T Recommendation E.501 (1997), *Estimation of traffic offered in the network*.
+- CCITT Recommendation E.503 (1992), *Traffic measurement data analysis*.
+- CCITT Recommendation E.504 (1988), *Traffic measurement administration*.
+- CCITT Recommendation E.506 (1992), *Forecasting international traffic*.
+- CCITT Recommendation E.507 (1988), *Models for forecasting international traffic*.
+- CCITT Recommendation E.508 (1992), *Forecasting new telecommunication services*.
+- ITU-T Recommendation E.600 (1993), *Terms and definitions of traffic engineering*.
+
+## 3 Definitions
+
+This Recommendation defines the following terms:
+
+The **Daily Peak Period (DPP) traffic intensity measurement method** is the method in which traffic intensity is measured for consecutive read-out periods of each day, and the peak traffic intensity for the day is recorded. This method requires continuous measurements.
+
+The **Fixed Daily Measurement Interval (FDMI) traffic intensity measurement method** is the method in which a predetermined time interval (i.e. a set of consecutive read-out periods during a day) in which peak period loads usually occur is identified, and during that time interval each day traffic intensity measurements are taken. The peak traffic intensity over the measured read-out periods is recorded for the day.
+
+**Normal load condition** identifies frequent busy operating conditions of the network for which user expectations should be met.
+
+**High load condition** identifies not very frequently encountered operating conditions for which user service expectations would not necessarily be met, but for which the level of performance achieved should be high enough to avoid significant user dissatisfaction, spread of congestion, etc.
+
+**Normal (high) load traffic intensity** is the representative value over a monthly time interval of the traffic intensity under normal (high) load condition.
+
+**Yearly Representative Value (YRV) of the normal (high) load traffic intensity** is the representative value over a yearly time interval of the traffic intensity under normal (high) load condition.
+
+Other definitions follow Recommendation E.600.
+
+## 4 Abbreviations
+
+This Recommendation uses the following abbreviations:
+
+|      |                                  |
+|------|----------------------------------|
+| CPU  | Central Processing Unit          |
+| DPP  | Daily Peak Period                |
+| FDMI | Fixed Daily Measurement Interval |
+| GOS  | Grade of Service                 |
+| YRV  | Yearly Representative Value      |
+
+## 5 Traffic intensity concepts
+
+### 5.1 Background
+
+In a broad sense, traffic intensity relates to the rate that work arrives to a traffic system and the resources needed to handle the work. The class of *traffic systems* under consideration in this Recommendation consists of a pool of resources of a single type, jobs that arrive and seize a needed amount of resources or wait until they are available (or leave if there are insufficient available resources and insufficient waiting room), and a holding time per job, which is the time a job requires from a specified quantity of dedicated resources to complete its work. Some important examples are:
+
+- Circuit Groups – The job is the call, the resources are the specified number of circuits required by the call, and the holding time for a job is the call holding time.
+- Call Processing – The resource is a call processing CPU, the job is a call, and the holding time for the job is the CPU processing time for the call.
+- Packet Data Transport – The resource is a fixed bandwidth data transmission channel, the job is to transport a data packet over the transmission channel, and the holding time for a job is the time it takes to transmit the packet (i.e. [packet length]/[data channel speed]).
+- B-ISDN network – Consider an ATM link in which the Connection Admission Control (CAC) assigns a certain fixed bandwidth to each arriving connection. It behaves as a traffic system in which the job is a connection, the resource is the bandwidth assigned by the CAC to the connection and the holding time for a job is the connection holding time.
+
+Average traffic intensity is measured over time intervals which are called *read-out periods* (see Recommendation E.492). The length of the read-out period must be chosen so that acceptable estimates of traffic intensity are obtained. Specific considerations that must be made in choosing the read-out period are given in 5.5.
+
+### 5.2 Traffic intensity concept and stationarity
+
+Instantaneous carried traffic intensity is defined in Recommendation E.600 as the amount of occupied resources in a traffic system at a given instant. Instantaneous offered traffic intensity is the amount of occupied resources in a traffic system with infinite resources. Average traffic intensity is defined as the time average of the instantaneous traffic intensity over a period of time. The variation of the instantaneous traffic intensity over time is called the traffic intensity process.
+
+This Recommendation deals with situations in which the traffic intensity process can be considered stationary, that is, there are stationary traffic intensity models that are a good approximation to the actual traffic intensity process<sup>1</sup>. For the traffic intensity process to be considered stationary in a read-out period, it is necessary that:
+
+- a) the job arrival process can be considered stationary;
+- b) the job departure process can be considered stationary;
+- c) both the arrival and departure processes have the same mean rate during the read-out period.
+
+When the average job holding time is much smaller than the read-out period, conditions b) and c) are satisfied in most practical situations if condition a) is satisfied. In this case, the average traffic intensity is given by:
+
+$$A = \lambda \cdot n \cdot h \quad (1)$$
+
+where  $\lambda$  is the average job arrival rate,  $n$  is the average number of dedicated resources per job, and  $h$  the average resource holding time per job (weighted with the number of resources needed by the job).
+
+If the mean holding time is of the order or greater than the read-out period, equation (1) may not hold even though the traffic intensity process can be approximated by a statistical model. An example of this situation is illustrated in Annex A.
+
+### 5.3 Assumptions for this Recommendation
+
+In order for the methods used in this Recommendation to be valid, the following assumptions must be satisfied:
+
+- 1) A read-out period length can be chosen such that there is, for each observed read-out period, a stationary model that is a good approximation to the actual traffic intensity process observed.
+- 2) If the model of the traffic intensity process has parameters in addition to traffic intensity (e.g. peakedness or variance measures), those parameters are obtained by methods that are not covered in this Recommendation.
+- 3) When there are additional parameters, as identified in Assumption 2, the worst case situation for dimensioning resources always occurs when the traffic intensity is highest.
+
+---
+
+<sup>1</sup> A good approximation means that when the traffic intensity model parameters are set to produce the measured traffic intensity over an observed read-out period, and this traffic model is used to predict system performance over the read-out period, the predicted performance is (for dimensioning purposes) within acceptable limits of accuracy from the observed performance.
+
+- 4) Exceptional read-out periods that violate Assumption 1 (e.g. the observed arrival process is highly non-stationary) should be detected and excluded from being considered.<sup>2</sup>
+
+### 5.4 Measured traffic intensity
+
+Consider a traffic system and let  $W(t_1, t_2)$  be the total work done<sup>3</sup> over the time interval  $(t_1, t_2)$ . The *measured traffic intensity* over the time interval  $(t_1, t_2)$  is defined as:
+
+$$A(t_1, t_2) = W(t_1, t_2) / (t_2 - t_1) \quad (2)$$
+
+The unit for measured traffic intensity is the erlang, and (2) represents the average number of busy resources over the time interval  $(t_1, t_2)$ .
+
+If the traffic system blocks some of the arrivals, the measured traffic intensity is a measure of *carried load* and not of the offered load. With negligible blocking, the measured traffic intensity is also a measure of the offered load. For dimensioning purposes, the need is to dimension for offered load, so it is desirable for the measured traffic intensities used in dimensioning to capture the offered load. If there is significant blocking present when traffic intensities are measured, some method should be used to estimate the blocked traffic intensities so that as good an estimate as possible of the offered load is determined. Recommendation E.501 provides procedures for estimating the traffic offered to a circuit switched network.
+
+To use (2) to measure traffic intensity, it is necessary to measure the actual resource usage  $W(t_1, t_2)$ . An alternative frequently used in practice is to average samples of the total resources in use, taken at uniformly spaced points in time over the read-out period. Another alternative, only valid if the job holding time is much smaller than the read-out period, is to measure job arrivals, number of needed resources per job and holding time per job. Under these conditions let  $N(t_1, t_2)$  denote the number of job arrivals over the time interval  $(t_1, t_2)$ . Then (2) can be rewritten as:
+
+$$\begin{aligned} A(t_1, t_2) &= [N(t_1, t_2) / (t_2 - t_1)] \cdot [W(t_1, t_2) / N(t_1, t_2)] \\ &= \lambda(t_1, t_2) \cdot n(t_1, t_2) \cdot h(t_1, t_2) \end{aligned} \quad (3)$$
+
+In this form  $A(t_1, t_2)$  has the form of (1) where it is expressed as the product of an average measured job arrival rate,  $\lambda(t_1, t_2)$ , an average number of resources used per job,  $n(t_1, t_2)$ , and an average measured holding time per job,  $h(t_1, t_2)$ .
+
+### 5.5 Convergence of the measured traffic intensity and choice of read-out period
+
+The measured traffic intensity,  $A(t_1, t_2)$ , given in (2) and, when applicable, in (3), is an estimate of the average traffic intensity  $A$ , and as  $(t_2 - t_1)$  increases,  $A(t_1, t_2)$  converges to  $A$ . From a traffic measurement perspective, it is desired to choose a read-out period length  $(t_2 - t_1)$  large enough that  $A(t_1, t_2)$  lies within a narrow confidence interval about  $A$ . However, the read-out period cannot be chosen too large, for then the traffic intensity process will no longer be approximately stationary, and
+
+---
+
+<sup>2</sup> This Recommendation defines normal and high load traffic intensities (see 6.3) for read-out periods satisfying Assumption 1, and it provides methods for determining traffic intensities for dimensioning (see clause 7) to meet specified GOS parameters during those periods. Dimensioning might also be done to meet other GOS parameters during read-out periods violating Assumption 1. Traffic intensity measurements and methods for those periods are outside the scope of this Recommendation.
+
+<sup>3</sup> When holding times are much smaller than the read-out period, an alternative definition is to use the total work that arrives over the interval  $(t_1, t_2)$ . In some cases it is easier to measure the total work a job brings when it arrives rather than measuring the actual resource usage (e.g. for packet networks one can accumulate the total octets that arrive as opposed to measuring the total octets sent).
+
+the measured traffic intensity looses its ability to characterize load levels for dimensioning resources and monitoring GOS.
+
+If a read-out period length cannot be determined that gives an acceptable confidence interval and satisfies Assumption 1 of 5.3, then more detailed models should be considered. If a satisfactory model cannot be found, then the methods in this Recommendation should not be used.
+
+The required length of the read-out period to achieve a desired size confidence interval depends on the traffic model that approximates the actual traffic. For example, consider a circuit group to which calls arrive as a Poisson process with a known average holding time,  $h$ , and an unknown average arrival rate,  $\lambda$ . To estimate the average traffic intensity (i.e.  $\lambda h$ ), it is necessary to take measurements over a read-out period that is long enough to obtain a desired level of confidence. Suppose it is desired to estimate the traffic intensity with a 95% confidence interval width smaller than  $\alpha \times (\text{estimated traffic intensity})$ . Then it can be shown, based on well known results for the Poisson processes, that the measurement interval must be long enough to observe more than  $[2 \times 1.96 / \alpha]^2$  call arrivals (e.g. if  $\alpha = 0.2$ , the read-out period must be long enough to observe more than 384 call arrivals). Methods to choose a read-out period length for other types of traffic models should be based, when possible, on appropriate statistical models to approximate the confidence interval, and read-out periods should be chosen long enough to achieve a desired level of confidence based on the statistical model. If appropriate statistical models are not available, statistical techniques based on the analysis of the measured traffic intensity may be possible. For example, the average measured traffic intensity as defined in (2) can be examined as  $(t_2 - t_1)$  increases, and criteria based on the convergence of this average measured traffic intensity can be used.
+
+For certain types of actual traffic patterns (e.g. very bursty traffic), some traffic models can lead to very short read-out periods. In these cases alternative models should be used, if possible, that lead to longer read-out periods (e.g. greater than 5 minutes) so that resources are not dimensioned for infrequent small interval peak traffic levels.
+
+## 6 Measurement methods and normal and high load traffic intensities
+
+The read-out period is chosen so that the arrival process is close to a stationary model; but looking over many read-out periods, the traffic intensity will change significantly. The telecommunications resources must be dimensioned to accommodate the higher load levels that will occur over time. The notions of normal and high load conditions are used to identify the traffic intensity values to use for resource dimensioning.
+
+The *normal* load condition is intended to represent frequent busy operating conditions of the network for which user service expectations should be met. A *high* load condition is intended to represent less frequently encountered operating conditions for which user service expectations would not necessarily be met, but for which the level of performance achieved should be high enough to avoid significant user dissatisfaction, spread of congestion (e.g. due to excessive user repeat attempts), etc.
+
+### 6.1 Daily measurement methods
+
+The recommended daily traffic intensity measurement method is the one developed in Recommendation E.492, and it will be termed the Daily Peak Period (DPP) method. In this method, the traffic intensity is measured for consecutive read-out periods of each day and the peak traffic intensity for the day is recorded. This method requires continuous measurement.
+
+If the traffic patterns are known to be somewhat predictable, non-continuous measurement methods are possible. If it is known that peak period loads will usually occur during certain intervals of the day, a Fixed Daily Measurement Interval (FDMI) method can be used in which a predetermined time
+
+interval (i.e. a set of consecutive read-out periods) is identified. During this time interval each day traffic intensity measurements are taken. The peak traffic intensity over the measured read-out periods is recorded for the day.
+
+If it is known that peak period loads will likely occur during a particular read-out period during the day, the FDMI method can be reduced to measuring traffic intensity only during the identified busy read-out period and recorded for the day.
+
+For the non-continuous measurement method (i.e. FDMI), it is necessary to periodically take additional measurements to make sure traffic patterns have not changed and the busy periods are still being captured during the measurement intervals being used.
+
+In some cases tariff structures may change during the day to stimulate (or curtail) traffic, and the desired GOS from the network may be different for the different tariff structures. In the cases when the GOS parameters change, the chosen traffic measurement method should be used for each time interval a particular set of GOS parameters apply. This is because the network must be dimensioned to handle the load for each of these time periods. Thus, a daily peak traffic intensity should be recorded for each GOS period during the day.
+
+### **6.2 Grouping of daily measurements**
+
+In order to do meaningful statistical analysis of traffic intensity measurements, the daily measurements have been traditionally organized into statistically homogeneous groups (i.e. collected into daily groups having, approximately, the same statistical behaviour). The three daily groups to be considered are: working days, week-end days (including most holidays), and yearly exceptional days (e.g. Christmas, Mother's Day, extraordinary events, etc.). If GOS objectives change during the day due to tariff strategies or other reasons, as discussed above, the groupings would be expanded to be by day and by GOS period.
+
+Week-end traffic intensities are usually smaller than the working days intensities. Thus week-end days have been traditionally excluded to determine normal and high traffic loads. However, the method proposed below for determining normal and high loads does not need to previously exclude the week-end days because, if they really have lower traffic intensity, they will be automatically excluded by the method itself.
+
+This is not the case of the yearly exceptional days. Different GOS objectives are typically used by the operators for those days than for either normal load or high load GOS. These days of exceptional high traffic are not automatically excluded by the method for determining normal and high loads.
+
+Thus, if different GOS objectives are used for those days, they should be excluded before determining normal and high loads. Note that the ITU-T Recommendations do not address GOS target values for yearly exceptional days, so operators need to agree on a bilateral basis to what GOS objectives should be met for those days.
+
+Although working and week-end days do not have to be distinguished for determining normal and high loads, it may be necessary to distinguish them if additional statistical analysis is desired.
+
+### **6.3 Normal and high load traffic intensities**
+
+Using either of the daily measurement methods described above (DPP or FDMI), a daily peak traffic intensity for a traffic system is determined. This daily peak traffic intensity measurement is the basis for determining normal and high load traffic intensities. If there are multiple GOS periods during the day, as discussed above, a daily peak traffic intensity would be determined for each GOS period and normal and high load traffic intensities would be found for each daily GOS period. The following
+
+definitions of normal and high load traffic intensities for a traffic system are based on the methods developed in Recommendation E.492.
+
+Normal and high load traffic intensities are defined over a monthly time interval.<sup>4</sup> A set of days is chosen out of the month. This set of days may be either all the days except the yearly exceptional ones, or only the group of working days. This second option may be used only when it is known that the traffic intensities in the week-end days are smaller than in the working days.
+
+The *normal load traffic intensity* for a traffic system is determined by the following steps:
+
+- 1) Order the chosen days from lowest to highest daily peak traffic intensity measurement.
+- 2) Select the day having the fourth highest daily peak traffic intensity measurement. This traffic intensity is defined as the *normal load traffic intensity* of the traffic system for the month being considered.<sup>5</sup>
+
+The *high load traffic intensity* for the traffic system is determined by following the procedure indicated in step 1) above and then selecting the day having the second highest daily peak traffic intensity measurement. This traffic intensity is defined as the *high load traffic intensity* of the traffic system for the month being considered.
+
+It is important to note that within a telecommunications network there are different traffic systems and their normal and high loads must be determined individually. In fact, the daily peak traffic intensity for different traffic systems can occur during different read-out periods. For example, consider a single exchange for which there are three major traffic systems: circuit groups, call processing and signalling network. Suppose in one hour the average call arrival rate is 100 calls/s with an average call holding time of 180 s, and in another hour the average call arrival rate is 200 calls/s with a 60 s average call holding time. For the circuit group traffic system, the first hour has the highest traffic intensity (18 000 erlangs). For the call processing and signalling traffic systems, the second hour has the higher traffic intensity (assuming the holding time per call in those systems is the same for both hours).
+
+### 6.4 Considerations on service measurements
+
+In case the traffic is composed of jobs that correspond to different services (multiservice traffic) with different traffic characteristics or different potential demand growth, it can be useful to make individual measurements for the traffic of each service. In case some services have a potential demand growth greater than other services, the period determining the normal or high load of those services could correspond in the future to the period determining the normal or high load of the aggregated traffic. Thus, attention should not only be paid to the measurements in the periods of normal or high load of the aggregated traffic, but also to the measurements in the periods of high traffic of services which, due to its present volume and to their potential growth, could determine the future normal and high loads of the aggregated traffic. Measurements to provide the daily traffic profile for each service could be useful to identify those periods to which attention must also be paid. This subject requires further study.
+
+---
+
+<sup>4</sup> A month is chosen because it is short enough that seasonal variations and growth will not significantly affect load behaviour during the time interval considered, and it is long enough to get adequate statistical significance.
+
+<sup>5</sup> If there is more information available on the distribution of the peak daily traffic load, a day other than the fourth highest might be determined to be more appropriate.
+
+## 7 Determination of the traffic intensity values for resource dimensioning
+
+Resources in a traffic system are dimensioned to meet specified GOS objectives for defined load periods. In this clause the normal and high load traffic intensities defined above are considered, and methods for determining traffic intensities for dimensioning resources to meet GOS objectives are described.
+
+Given the way normal and high load traffic intensities are defined, they must be viewed as observations of random variables. That is, the measured values of normal and high load traffic intensities for each month are samples from their respective probability distribution.
+
+Ideally, the objective of resource dimensioning in a traffic system is to dimension the resources so that the normal and high load GOS parameters are met when the normal and high load traffic intensities occur, respectively, in each month. The problem in meeting this ideal objective is that the normal and high load traffic intensities for each month are random variables, and to dimension so these objectives are met with certainty for each month could be very costly. An alternative might be to dimension so as to keep the probability of not meeting the normal and high load GOS objectives in any month less than some chosen value. However, this approach requires knowledge of, or good approximations for, the probability distribution functions of the normal and high load traffic intensities random variables. In general, such distribution information is difficult to obtain due to the lack of homogeneity in traffic patterns from month-to-month. This lack of homogeneity results in small samples on which to base statistical analysis, and therefore large confidence intervals would result. It has been found from analysis and simulation that the probability distributions for normal and high load traffic intensities are very sensitive to the underlying traffic intensity distribution functions, and therefore it is not possible to give a general methodology along these lines.
+
+As an alternative to basing dimensioning on knowledge of the probability distribution functions of the normal and high load traffic intensity random variables, the following method based on an observed Yearly Representative Value (YRV) is suggested. In this method, the normal and high load traffic intensities are recorded for each month of a year. The YRV of the normal (high) load for that year is chosen to be either the second highest or the highest observed normal (high) load traffic intensity for that year. If the traffic intensity tends to be fairly homogeneous from month-to-month, it is recommended that the second highest value be chosen, since this would help avoid outliers. However, if there is not much homogeneity (e.g. one or two months tend to generate the peak loads), then using the peak value is recommended.
+
+If the normal or high load YRV comes from a situation in which there was significant blocking in the network, it is necessary to estimate the offered traffic intensity and use it for the YRV rather than the measured carried traffic intensity. Recommendation E.501 provides some methods for estimating offered traffic intensity from measured traffic intensity in a circuit switched network.
+
+Once the normal and high load YRVs for the current year have been determined, the normal and high load traffic intensities to use to dimension the traffic system for future years are obtained by applying the expected growth to the YRVs for the current year. The expected growth should be determined using traffic forecasting methods (see Recommendations E.506, E.507 and E.508). The growth model applied to the YRV could also include some safety margin to account for uncertainty. The amount of safety margin to use must be determined by experience with the specific traffic system and the circumstances in which it is being dimensioned.
+
+## 8 History
+
+Recommendation E.500 – First issue 1969; revised in 1992; present revision in 1998.
+
+## ANNEX A
+
+### Example of stationary traffic intensity with holding times larger than the read-out period
+
+This annex illustrates how traffic systems with call holding times greater than the read-out period can lead to a traffic intensity process over the read-out period that can be approximated by a stationary process, but equation (1) is not valid for computing average traffic intensity over the read-out period.
+
+Consider a traffic system consisting of a circuit group with two call arrival processes. The first call arrival process, Process 1, has calls with exponentially distributed holding times, an average holding time of 1 minute, and a stationary Poisson call arrival process with an average call arrival rate of 100 calls/minute for all time. The second call arrival process, Process 2, has a deterministic call holding time of 100 minutes, and a deterministic call arrival process that has a call arrival rate of 20 calls/min for time,  $t$ , in the interval  $0 < t < 10$  min, and 0 calls/min for all other times<sup>6</sup>.
+
+Figure A.1 illustrates the resulting traffic intensities. Process 1 is a stationary process, and equation (1) can be used to determine its average traffic intensity for all time  $t$  as 100 circuits. Process 2 is a non-stationary process, so its average traffic intensity depends on the length and placement of the time interval over which the average is taken. However, its instantaneous traffic intensity is easily characterized; it is seen to increase linearly over the time interval  $(0, 10)$  min, stay constant at 200 circuits over the interval  $(10, 100)$  min, and drop linearly back to zero over the interval  $(100, 110)$  min.
+
+The total traffic intensity on the system can be characterized by the sum of the average traffic intensity of Process 1 and the instantaneous traffic intensity of Process 2, as shown in Figure A.1. For time intervals  $(-\infty, 0)$ ,  $(10, 100)$ , and  $(110, \infty)$  the traffic intensity process can be approximated by a stationary process. For time intervals  $(-\infty, 0)$  and  $(110, \infty)$  the approximating process is just Process 1, and for time interval  $(10, 100)$  the approximating process is Process 1 applied on top of 200 occupied circuits. It is clear that equation (1) is not valid during time interval  $(10, 100)$ .
+
+---
+
+<sup>6</sup> The choice of deterministic arrivals and holding times for Process 2 is only for ease of explanation. It is straightforward to expand this example to include more realistic models that include randomness in Process 2. Process 2 is intended to represent such services as video on demand, with long holding times (about 90 minutes) and most call arrivals concentrated in certain time intervals (typically between 8 PM and 9 PM).
+
+![Line graph showing Traffic Intensity (circuits) vs Time (min) for three processes: Total (Process 1 + Process 2), Process 2 (Instantaneous intensity), and Process 1 (Average intensity).](ad29805cd4f64ad2828e14feb66de664_img.jpg)
+
+The graph illustrates traffic intensity over a 100-minute period. The y-axis represents 'Traffic Intensity (circuits)' from 0 to 400, and the x-axis represents 'Time (min)' from 0 to 100. A dashed horizontal line at 100 circuits represents 'Process 1: Average intensity'. A dotted line represents 'Process 2: Instantaneous intensity', which rises from 0 to 200 circuits at 10 minutes, stays constant until 100 minutes, and then drops to 0. A solid line represents 'Total: Process 1 + Process 2', which rises from 100 to 300 circuits at 10 minutes, stays constant until 100 minutes, and then drops to 100 circuits. The label 'T0207220-98' is in the bottom right corner.
+
+| Time (min) | Process 1: Average intensity (circuits) | Process 2: Instantaneous intensity (circuits) | Total: Process 1 + Process 2 (circuits) |
+|------------|-----------------------------------------|-----------------------------------------------|-----------------------------------------|
+| 0          | 100                                     | 0                                             | 100                                     |
+| 10         | 100                                     | 200                                           | 300                                     |
+| 100        | 100                                     | 200                                           | 300                                     |
+| 100+       | 100                                     | 0                                             | 100                                     |
+
+Line graph showing Traffic Intensity (circuits) vs Time (min) for three processes: Total (Process 1 + Process 2), Process 2 (Instantaneous intensity), and Process 1 (Average intensity).
+
+**Figure A.1/E.500**
+
+# ITU-T RECOMMENDATIONS SERIES
+
+- Series A Organization of the work of the ITU-T
+- Series B Means of expression: definitions, symbols, classification
+- Series C General telecommunication statistics
+- Series D General tariff principles
+- Series E Overall network operation, telephone service, service operation and human factors**
+- Series F Non-telephone telecommunication services
+- Series G Transmission systems and media, digital systems and networks
+- Series H Audiovisual and multimedia systems
+- Series I Integrated services digital network
+- Series J Transmission of television, sound programme and other multimedia signals
+- Series K Protection against interference
+- Series L Construction, installation and protection of cables and other elements of outside plant
+- Series M TMN and network maintenance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits
+- Series N Maintenance: international sound programme and television transmission circuits
+- Series O Specifications of measuring equipment
+- Series P Telephone transmission quality, telephone installations, local line networks
+- Series Q Switching and signalling
+- Series R Telegraph transmission
+- Series S Telegraph services terminal equipment
+- Series T Terminals for telematic services
+- Series U Telegraph switching
+- Series V Data communication over the telephone network
+- Series X Data networks and open system communications
+- Series Y Global information infrastructure
+- Series Z Programming languages

marked/E/T-REC-E.522-198811-I_PDF-E/raw.md

@@ -0,0 +1,422 @@
+
+
+![ITU logo](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg)
+
+The logo of the International Telecommunication Union (ITU) features the letters 'ITU' in a bold, sans-serif font, superimposed on a stylized globe with intersecting lines.
+
+ITU logo
+
+INTERNATIONAL TELECOMMUNICATION UNION
+
+**ITU-T**
+
+**E.522**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+**TELEPHONE NETWORK AND ISDN**
+
+**QUALITY OF SERVICE, NETWORK MANAGEMENT  
+AND TRAFFIC ENGINEERING**
+
+---
+
+**NUMBER OF CIRCUITS IN A HIGH-USAGE  
+GROUP**
+
+**ITU-T Recommendation E.522**
+
+(Extract from the *Blue Book*)
+
+---
+
+# NOTES
+
+1 ITU-T Recommendation E.522 was published in Fascicle II.3 of the *Blue Book*. This file is an extract from the *Blue Book*. While the presentation and layout of the text might be slightly different from the *Blue Book* version, the contents of the file are identical to the *Blue Book* version and copyright conditions remain unchanged (see below).
+
+2 In this Recommendation, the expression “Administration” is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+# NUMBER OF CIRCUITS IN A HIGH-USAGE GROUP
+
+## 1 Introduction
+
+For the economic planning of an alternate routing network the number of circuits in a high-usage group should be determined so that the annual charges for the whole network arrangement are at a minimum. This is done under the constraint that given requirements for the grade of service are fulfilled. In the optimum arrangement, the cost per erlang of carrying a marginal amount of traffic over the high-usage route or over the alternative route is the same.
+
+![A triangle diagram representing a network routing. The top vertex is labeled 'T'. The bottom-left vertex is labeled '(1)'. The bottom-right vertex is labeled '(2)'. To the right of the triangle, the text 'CCITT - 48090' is present.](163688ca8da9787f5d48edd68d8cc75b_img.jpg)
+
+A triangle diagram representing a network routing. The top vertex is labeled 'T'. The bottom-left vertex is labeled '(1)'. The bottom-right vertex is labeled '(2)'. To the right of the triangle, the text 'CCITT - 48090' is present.
+
+FIGURE 1/E.522
+
+The optimum number of high-usage circuits,  $n$ , from one exchange (1) to another exchange (2) is therefore obtained from the following expression when the overflow traffic is routed over a transit exchange T (route 1-T-2, see Figure 1/E.522).
+
+$$F_n(A) = A \{E_{1,n}(A) - E_{1,(n+1)}(A)\} = M \times \frac{\text{annual charge (1-2)}}{\text{annual charge (1-T-2)}}$$
+
+$A$  is the traffic flow offered, for the relation “1-2”, in the Erlang loss formula for a full availability group. The expression  $F_n(A)$  gives the marginal occupancy<sup>1)</sup> (improvement function) for the high-usage group, if one more circuit were added.
+
+$M$  is the *marginal utilization factor*<sup>2)</sup> for the final route “1-T-2” (which has nothing to do with cost ratio), if one additional circuit were provided. The annual charges are marginal charges for adding one additional circuit to route “1-2” and likewise to route “1-T-2”.
+
+Planning of an alternate routing network is described in the technical literature (see [1] to [10]).
+
+Annual charge as used in this Recommendation refers to investment costs.
+
+## 2 Recommended practical method
+
+### 2.1 Field of application
+
+It must be recognized that the conditions applying to alternative routing will vary widely between the continental network and the intercontinental network. Significant differences between the two cases apply to the length and cost of circuits, the traffic flow and the different times at which the busy hours occur. The method described attempts to take account of these factors in so far as it is practicable to do so in any simplified procedure.
+
+1) Marginal occupancy is often called LTC (last trunk capacity).
+
+2) Marginal utilization is often called ATC (additional trunk capacity).
+
+### 2.2 Traffic statistics
+
+The importance of reliable traffic estimates should be emphasized. Traffic estimates are required for each of the relations in question, for both the busy hour of the relation and for the busy hour of each link of the routes to which the traffic overflows. Since this may be affected by the high-usage arrangements finally adopted, it will be necessary to have traffic estimates for each relation covering most of the significant hours of the day. This applies particularly to the intercontinental network where the final routes carry traffic components with widely differing busy hours.
+
+### 2.3 Basis of the recommended method
+
+The method is based on a simplification of the economic dimensioning equations described under 1. Introduction. The simplifying assumptions are:
+
+- i) the ratios of the alternative high-usage annual charges are grouped in classes and a single ratio selected as representative for each class. This is acceptable because total network costs are known to be relatively insensitive to changes in the annual charges ratio;
+- ii) the marginal utilization factor  $M$  applicable to the overflow routes is regarded as constant within a range of circuit group sizes;
+
+| Size of group<br>(number of circuits) | Value of $M$ |
+|---------------------------------------|--------------|
+| For less than 10 . . . . .            | 0.6          |
+| For 10 or more . . . . .              | 0.8          |
+
+- iii) each high-usage group will be dimensioned against the cheapest alternative route to which traffic overflows. (That is, the effect of parallel alternative routes is ignored.)
+
+Where greater precision is required in either network or individual route dimensioning, more sophisticated methods may be employed (see [5] and [7]).
+
+### 2.4 Determination of cost ratio
+
+In continental and intercontinental working, the number of circuits to be provided in high-usage circuit groups depends upon the ratio of the annual charges estimated by the Administrations involved. The annual charge ratio (see Table 1/E.522) is defined as:
+
+$$R = \frac{\text{annual charge of one additional circuit on the alternative route}}{\text{annual charge of one additional circuit on the high - usage route}}$$
+
+The “annual charge of one additional circuit on the alternative route” is calculated by summing:
+
+- the annual charge per circuit of each link comprising the alternative route, and
+- the annual charge of switching one circuit at each intermediate switching centre.
+
+When a third Administration is involved, it may be necessary to calculate the annual charge for switching at the intermediate centre from the transit switching charge per holding minute<sup>3)</sup>. This may be done as follows:
+
+$$\text{Annual charges for switching} = M \times 60 \times F \times 26 \times 12 \times \text{transit switching charge per holding minute.}$$
+
+In the calculation of the conversion factor  $F$  from busy hour to day, its dependence on the traffic offered to the high usage route, the overflow probability and the time difference should be taken into account. As a guideline, Table 1/E.522, which is calculated using the standard traffic profiles of Table 1/E.523, may be used.
+
+---
+
+<sup>3)</sup> It may be necessary to calculate transit switching charge per holding minute from charge per conversation minute (efficiency factor is described in Recommendation E.506).
+
+TABLE 1/E.522
+
+| Offered traffic (erlangs) | Overflow probability (%) | Time difference |     |     |     |     |     |     |     |     |     |     |     |     |
+|---------------------------|--------------------------|-----------------|-----|-----|-----|-----|-----|-----|-----|-----|-----|-----|-----|-----|
+|                           |                          | 0               | 1   | 2   | 3   | 4   | 5   | 6   | 7   | 8   | 9   | 10  | 11  | 12  |
+| 5                         | 1                        | 2.6             | 3.2 | 3.7 | 3.8 | 2.7 | 2.3 | 2.3 | 1.7 | 3.2 | 2.4 | 2.2 | 2.0 | 2.7 |
+|                           | 10                       | 3.7             | 4.5 | 4.8 | 4.7 | 3.5 | 3.1 | 3.0 | 2.5 | 4.1 | 3.2 | 2.9 | 2.8 | 3.6 |
+|                           | 20                       | 4.5             | 5.2 | 5.4 | 5.3 | 4.0 | 3.7 | 3.5 | 3.1 | 4.7 | 3.8 | 3.4 | 3.4 | 4.2 |
+|                           | 30                       | 5.1             | 5.8 | 6.0 | 5.8 | 4.6 | 4.2 | 4.0 | 3.7 | 5.1 | 4.3 | 3.9 | 4.0 | 4.8 |
+|                           | 40                       | 5.7             | 6.4 | 6.5 | 6.3 | 5.1 | 4.7 | 4.5 | 4.2 | 5.6 | 4.8 | 4.4 | 4.6 | 5.3 |
+|                           | 50                       | 6.3             | 6.9 | 7.0 | 6.8 | 5.6 | 5.2 | 5.0 | 4.7 | 6.0 | 5.3 | 5.0 | 5.1 | 5.8 |
+| 10                        | 1                        | 2.1             | 2.6 | 3.3 | 3.5 | 2.5 | 2.1 | 2.1 | 1.4 | 2.8 | 2.0 | 2.0 | 1.8 | 2.4 |
+|                           | 10                       | 3.2             | 4.0 | 4.4 | 4.3 | 3.1 | 2.7 | 2.6 | 2.1 | 3.8 | 2.8 | 2.6 | 2.4 | 3.2 |
+|                           | 20                       | 4.0             | 4.8 | 5.1 | 4.9 | 3.6 | 3.3 | 3.1 | 2.7 | 4.3 | 3.4 | 3.0 | 3.0 | 3.8 |
+|                           | 30                       | 4.7             | 5.4 | 5.6 | 5.4 | 4.2 | 3.8 | 3.6 | 3.3 | 4.8 | 3.9 | 3.4 | 3.6 | 4.4 |
+|                           | 40                       | 5.3             | 6.0 | 6.1 | 5.9 | 4.7 | 4.4 | 4.2 | 3.8 | 5.3 | 4.4 | 4.0 | 4.2 | 4.9 |
+|                           | 50                       | 5.9             | 6.6 | 6.7 | 6.4 | 5.3 | 4.9 | 4.7 | 4.4 | 5.7 | 5.0 | 4.6 | 4.8 | 5.5 |
+| 25                        | 1                        | 1.6             | 2.0 | 2.8 | 3.1 | 2.2 | 1.8 | 2.0 | 1.2 | 2.4 | 1.7 | 1.8 | 1.6 | 2.1 |
+|                           | 10                       | 2.7             | 3.3 | 3.9 | 3.9 | 2.7 | 2.4 | 2.3 | 1.7 | 3.3 | 2.4 | 2.3 | 2.0 | 2.7 |
+|                           | 20                       | 3.5             | 4.2 | 4.6 | 4.4 | 3.2 | 2.8 | 2.7 | 2.2 | 3.9 | 3.0 | 2.6 | 2.5 | 3.3 |
+|                           | 30                       | 4.2             | 5.0 | 5.2 | 5.0 | 3.7 | 3.4 | 3.2 | 2.8 | 4.4 | 3.5 | 3.0 | 3.1 | 3.9 |
+|                           | 40                       | 4.8             | 5.6 | 5.8 | 5.5 | 4.3 | 3.9 | 3.8 | 3.4 | 4.9 | 4.0 | 3.5 | 3.7 | 4.5 |
+|                           | 50                       | 5.5             | 6.2 | 6.3 | 6.1 | 4.9 | 4.5 | 4.3 | 4.0 | 5.4 | 4.6 | 4.1 | 4.4 | 5.1 |
+| 50                        | 1                        | 1.3             | 1.7 | 2.4 | 2.9 | 2.1 | 1.6 | 2.0 | 1.1 | 2.1 | 1.5 | 1.6 | 1.4 | 2.0 |
+|                           | 10                       | 2.3             | 2.8 | 3.5 | 3.6 | 2.5 | 2.2 | 2.1 | 1.4 | 3.1 | 2.2 | 2.2 | 1.8 | 2.4 |
+|                           | 20                       | 3.1             | 3.9 | 4.3 | 4.2 | 3.0 | 2.6 | 2.4 | 1.9 | 3.7 | 2.7 | 2.5 | 2.2 | 3.0 |
+|                           | 30                       | 3.9             | 4.7 | 5.0 | 4.8 | 3.4 | 3.1 | 2.9 | 2.5 | 4.2 | 3.3 | 2.8 | 2.8 | 3.6 |
+|                           | 40                       | 4.6             | 5.4 | 5.6 | 5.3 | 4.0 | 3.7 | 3.5 | 3.2 | 4.7 | 3.8 | 3.2 | 3.5 | 4.3 |
+|                           | 50                       | 5.3             | 6.0 | 6.1 | 5.9 | 4.7 | 4.3 | 4.2 | 3.8 | 5.2 | 4.3 | 3.8 | 4.2 | 4.9 |
+
+*Note* – Linear interpolation may be used to obtain intermediate results.
+
+The value determined for  $R$  should then be employed to select in Table 2/E.522 the precise (or next higher) value of annual charges ratio for use in traffic tables. The value of annual charges ratios may be grouped in the following general sets:
+
+- Within a single continent or other smaller closely connected land mass involving distances up to 1000 miles, high traffic and frequently one-way operation:
+
+Annual charges ratio:  $R = 1.5; \underline{2.0}; 3.0; 4.0; 5.0; 6.0$  and  $7.0^{4)}$
+
+b) Intercontinental working involving long distances, small traffic and usually two-way operation:
+
+Annual charges ratio:  $R = 1.1; \underline{1.3}; 1.5; 2.0; 3.0; 4.0$  and  $5.0^{4)}$ .
+
+### 2.5 Use of method
+
+High-usage circuit groups carrying random traffic can be dimensioned from Table 2/E.522.
+
+*Step 1* – Estimate the annual charges ratio  $R$  as described under 2.4 above. (There is little difference between adjacent ratios.) If this ratio is difficult to estimate, the values underlined in a) and b) of § 2.4 above, should be used.
+
+*Step 2* – Consult Table 2/E.522 to determine the number of high-usage circuits  $N$ .
+
+*Note* – When two values of  $N$  are given the right-hand figure applies to alternative routes of more than 10 circuits, the left-hand figure applies to smaller groups. The left-hand figure is omitted when it is no longer possible for the alternative route to be small.
+
+## 3 24-hour traffic profiles
+
+The traffic value used in the method in § 2 should be the value of traffic offered to the high-usage route during the busy hour of the final route. In the case that some of the busy hours of the circuit groups or links forming an alternative route do not coincide with the busy hour of the relation, the ensuing method should be followed to take 24-hour traffic profiles into account (see [6], [8] and [9]).
+
+The method consists of the following three basic steps:
+
+- i) prepare hourly traffic demands for which dimensioning is to be done;
+- ii) size all circuit groups, high usage and final, for one hourly traffic demand;
+- iii) iterate the process in step ii) for each additional hourly matrix.
+
+### 3.1 Preparation of hourly traffic demands
+
+Each Administration gathers historical traffic data on an hourly basis in accordance with Recommendations E.500 and E.523. Using historical data and information contained in Recommendation E.506, hourly traffic demand forecasts are made, resulting in a series of hourly demands for each exchange to every other exchange.
+
+### 3.2 Sizing circuit groups for one-hourly traffic demand
+
+Using the methods in § 2 and Recommendation E.521, trunk group sizes are prepared for the first hourly traffic demand disregarding other hourly traffic demands.
+
+---
+
+4) These values are tentative. Ranges and representative values of annual charges ratio require further study.
+
+TABLE 2/E.522
+
+### Number of high-usage circuits for different values of offered traffic, annual charges ratios and sizes of overflow groups
+
+| Traffic offered during network busy hour (erlangs) | Annual charges ratios                                                                                                                                                                           |            |          |         |          |          |                                                              |          |             | Number of circuits if there is no overflow route, for $p = 0.01$ |  |
+|----------------------------------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|------------|----------|---------|----------|----------|--------------------------------------------------------------|----------|-------------|------------------------------------------------------------------|--|
+|                                                    | 1.1                                                                                                                                                                                             | 1.3        | 1.5      | 2.0     | 3.0      | 4.0      | 5.0                                                          | 6.0      | 7.0         |                                                                  |  |
+|                                                    | Minimum circuit occupancies for high-usage traffic                                                                                                                                              |            |          |         |          |          |                                                              |          |             |                                                                  |  |
+|                                                    | 0.545/0.727                                                                                                                                                                                     | 0.46/0.615 | 0.4/0.53 | 0.3/0.4 | 0.2/0.26 | 0.15/0.2 | 0.12/0.16                                                    | 0.0/0.13 | 0.085/0.114 |                                                                  |  |
+|                                                    | $N$ , number of high usage circuits $A/B$ , where<br>$A$ is for less than 10 circuits in the overflow group ( $M = 0.6$ )<br>$B$ is for 10 or more circuits in the overflow group ( $M = 0.8$ ) |            |          |         |          |          |                                                              |          |             |                                                                  |  |
+| 1.5                                                | 1/0                                                                                                                                                                                             | 1/0        | 2/1      | 2/2     | 3/2      | 3/3      | 4/3                                                          | 4/3      | 4/4         | 6                                                                |  |
+| 1.75                                               | 1/0                                                                                                                                                                                             | 2/1        | 2/1      | 3/2     | 3/3      | 4/3      | 4/4                                                          | 4/4      | 4/4         | 6                                                                |  |
+| 2.0                                                | 1/0                                                                                                                                                                                             | 2/1        | 2/2      | 3/2     | 4/3      | 4/4      | 4/4                                                          | 5/4      | 5/5         | 7                                                                |  |
+| 2.25                                               | 2/0                                                                                                                                                                                             | 2/1        | 3/2      | 3/3     | 4/4      | 5/4      | 5/4                                                          | 5/5      | 5/5         | 7                                                                |  |
+| 2.5                                                | 2/0                                                                                                                                                                                             | 3/1        | 3/2      | 4/3     | 5/4      | 5/5      | 5/5                                                          | 6/5      | 6/5         | 7                                                                |  |
+| 2.75                                               | 2/1                                                                                                                                                                                             | 3/2        | 3/2      | 4/3     | 5/4      | 5/5      | 6/5                                                          | 6/6      | 6/6         | 8                                                                |  |
+| 3.0                                                | 3/1                                                                                                                                                                                             | 3/2        | 4/3      | 4/4     | 5/5      | 6/5      | 6/6                                                          | 6/6      | 7/6         | 8                                                                |  |
+| 3.5                                                | 3/1                                                                                                                                                                                             | 4/2        | 4/3      | 5/4     | 6/5      | 7/6      | 7/6                                                          | 7/7      | 7/7         | 9                                                                |  |
+| 4.0                                                | 4/2                                                                                                                                                                                             | 4/3        | 5/4      | 6/5     | 7/6      | 7/7      | 8/7                                                          | 8/7      | 8/8         | 10                                                               |  |
+| 4.5                                                | 4/2                                                                                                                                                                                             | 5/3        | 6/4      | 6/6     | 7/7      | 8/7      | 8/8                                                          | 9/8      | 9/8         | 10                                                               |  |
+| 5.0                                                | 5/3                                                                                                                                                                                             | 6/4        | 6/5      | 7/6     | 8/7      | 9/8      | 9/9                                                          | 9/9      | 10/9        | 11                                                               |  |
+| 5.5                                                | 5/3                                                                                                                                                                                             | 6/5        | 7/5      | 8/7     | 9/8      | 9/9      | 10/9                                                         | 10/10    | 10/10       | 12                                                               |  |
+| 6.0                                                | 6/3                                                                                                                                                                                             | 7/5        | 7/6      | 8/7     | 9/9      | 10/9     | 11/10                                                        | 11/10    | 11/11       | 13                                                               |  |
+| 7.0                                                | 7/4                                                                                                                                                                                             | 8/6        | 8/7      | 10/8    | 11/10    | 11/11    | 12/11                                                        | 12/12    | 13/12       | 14                                                               |  |
+| 8.0                                                | 8/5                                                                                                                                                                                             | 9/7        | 10/8     | 11/10   | 12/11    | 13/12    | 13/13                                                        | 14/13    | 14/13       | 15                                                               |  |
+| 9.0                                                | /6                                                                                                                                                                                              | /8         | /9       | /11     | /12      | /13      | /14                                                          | /14      | /15         | 17                                                               |  |
+| 10.0                                               | /7                                                                                                                                                                                              | /9         | /10      | /12     | /14      | /15      | /15                                                          | /16      | /16         | 18                                                               |  |
+| 12.0                                               | /9                                                                                                                                                                                              | /11        | /12      | /14     | /16      | /17      | /18                                                          | /18      | /19         | 20                                                               |  |
+| 15.0                                               | /12                                                                                                                                                                                             | /14        | /16      | /18     | /20      | /21      | /21                                                          | /22      | /22         | 24                                                               |  |
+| 20.0                                               | /16                                                                                                                                                                                             | /19        | /21      | /23     | /25      | /27      | /28                                                          | /28      | /29         | 30                                                               |  |
+| 25.0                                               | /21                                                                                                                                                                                             | /24        | /26      | /29     | /31      | /33      | /33                                                          | /34      | /35         | 36                                                               |  |
+| 30.0                                               | /26                                                                                                                                                                                             | /29        | /31      | /34     | /37      | /38      | /39                                                          | /40      | /41         | 42                                                               |  |
+| 40.0                                               | /36                                                                                                                                                                                             | /39        | /42      | /45     | /48      | /50      | /51                                                          | /52      | /52         | 53                                                               |  |
+| 50.0                                               | /45                                                                                                                                                                                             | /49        | /52      | /55     | /59      | /61      | /62                                                          | /63      |             | 64                                                               |  |
+| 60.0                                               | /55                                                                                                                                                                                             | /60        | /62      | /66     | /70      | /72      | /73                                                          |          |             | 75                                                               |  |
+| 80.0                                               | /74                                                                                                                                                                                             | /80        | /83      | /87     | /92      | /94      | /95                                                          |          |             | 96                                                               |  |
+| 100.0                                              | /94                                                                                                                                                                                             | /100       | /103     | /108    | /113     | /116     |                                                              |          |             | 117                                                              |  |
+| 120.0                                              | /113                                                                                                                                                                                            | /120       | /124     | /129    | /134     | /137     | Direct final circuit groups are economical within this area. |          |             | 138                                                              |  |
+| 150.0                                              | /143                                                                                                                                                                                            | /150       | /154     | /160    | /166     | /169     |                                                              |          |             | 170                                                              |  |
+| 200.0                                              | /192                                                                                                                                                                                            | /200       | /205     | /212    | /219     |          |                                                              |          |             | 221                                                              |  |
+| 250.0                                              | /241                                                                                                                                                                                            | /250       | /256     | /263    | /271     |          |                                                              |          |             | 273                                                              |  |
+| 300.0                                              | /290                                                                                                                                                                                            | /300       | /306     | /315    | /323     |          |                                                              |          |             | 324                                                              |  |
+
+### 3.3 *Iterating for each additional hourly traffic matrix*
+
+In sizing the circuit groups for the second hourly traffic demand, the method is provided with the circuit quantities resulting from the previous step, and is constrained solely to increasing circuit group sizes; i.e., if the circuit group sizes for the first hourly traffic demand were greater than for the second hourly demand, then the circuit group sizes for the first hourly traffic demand would be retained.
+
+All additional hourly traffic demands are processed in the same iterative manner. The resulting circuit group sizes then satisfy the traffic demands for all hours being considered (see Annex A for a computational example).
+
+### 3.4 *Processing sequence*
+
+Processing may start with the first hour of traffic demand, however, experiments have indicated that efficiencies of the network can be improved if processing starts with the hour with the smallest total traffic demand. It should be noted that this method gives us suboptimal networks, which may be improved by manual refinements.
+
+## 4 **Minimum outlay alternate routing networks**
+
+The method below allows Administrations to adjust alternate routing networks to take into account existing revenue accounting divisions.
+
+The method consists of the following steps:
+
+- i) Obtain 24-hour traffic profiles in accordance with Recommendations E.500 and E.523;
+- ii) Compute circuit quantities and costs for a no-overflow network in accordance with Recommendation E.520;
+- iii) Compute monthly overflow minutes (holding time) at varying percentages of busy-hour overflow. This is done by applying three conversion factors to the busy hour overflow erlangs:
+  - Ratio of holding minutes to erlangs: a fixed value of 60.
+  - Daily overflow to busy-hour overflow ratio: a value that depends on the 24-hour traffic profile and the degree of overflow.
+  - Monthly overflow to daily overflow ratio (Recommendation E.506): a value that depends on the day-to-day pattern within a month and the degree of overflow.
+- iv) Starting with the network calculated in step ii):
+  - reduce the high usage circuits by one circuit,
+  - calculate overflow to final circuit groups,
+  - dimension final circuit groups in accordance with Recommendation E.521,
+  - calculate circuit costs and transit charges;
+- v) Iterate step iv) until the minimum outlay (circuit costs plus transit charges) for terminal administrations is reached (see Annex B for computational example).
+
+## 5 **Service considerations**
+
+On intercontinental circuits, where both-way operation is employed, a minimum of two circuits may be economical. Service considerations may also favour an increase in the number of direct circuits provided, particularly where the annual charges ratio approaches unity.
+
+Although the dimensioning of high-usage groups is normally determined by traffic flows and annual charges ratios, it is recognized that such groups form part of a network having service requirements relative to the subscriber. The ability to handle the offered traffic with acceptable traffic efficiency should be tempered by the overall network considerations on quality of service.
+
+The quality of service feature, which is of primary importance in a system of high-usage and final circuit groups, is the advantage derived from direct circuits versus multi-link connections. A liberal use of direct high-usage circuit groups, taking into account the economic factors, favours a high quality of service to the subscriber. It is recommended that new high-usage groups should be provided whenever the traffic flow and cost ratios are not conclusive. This practice may result in direct high-usage groups of two circuits or more.
+
+The introduction of high-usage groups improves the overall grade of service and provides better opportunities of handling traffic during surges and breakdown conditions. When high-usage links bypass the main final routes the introduction of high-usage routes can assist in avoiding expenses which might otherwise be incurred in keeping below the maximum number of long-distance links in series. In the future, more measurements of traffic flows may be necessary for international accounting purposes and high-usage circuits should make this easier.
+
+## ANNEX A
+
+(to Recommendation E.522)
+
+### Example of network dimensioning taking into account 24-hour traffic profiles
+
+#### A.1 Assumptions (see also Figure A-1/E.522)
+
+Calculations are performed under the following conditions:
+
+- 1) Time difference:  
+ A is 9 hours west of B  
+ C is 5 hours west of A  
+ B is 10 hours west of C
+- 2) Traffic profiles:  
+ 24-hour traffic profiles as per Table I/E.523 are used.
+- 3) Busy hour traffic:  
+ A-B 50 erlangs  
+ A-C 100 erlangs  
+ C-B 70 erlangs
+- 4) Cost ratio:  
+ $R = 1.3$
+
+![Diagram of a triangular network for numerical examples (Example 1). The network consists of three nodes: A, B, and C. Node A is at the bottom left, node B is at the bottom right, and node C is at the top. The base of the triangle is a horizontal line labeled 'High usage circuit group'. The left side is a diagonal line labeled 'Final circuit group'. The right side is a diagonal line labeled 'Final circuit group'. Arrows indicate traffic flow: from A to C along the left side, from C to B along the right side, and from A to B along the base. The word 'Overflow' is written above the base line, between the two diagonal lines. The text 'CCITT-69331' is located to the right of node B.](0b87abe67b21a93777287649c33e755d_img.jpg)
+
+Diagram of a triangular network for numerical examples (Example 1). The network consists of three nodes: A, B, and C. Node A is at the bottom left, node B is at the bottom right, and node C is at the top. The base of the triangle is a horizontal line labeled 'High usage circuit group'. The left side is a diagonal line labeled 'Final circuit group'. The right side is a diagonal line labeled 'Final circuit group'. Arrows indicate traffic flow: from A to C along the left side, from C to B along the right side, and from A to B along the base. The word 'Overflow' is written above the base line, between the two diagonal lines. The text 'CCITT-69331' is located to the right of node B.
+
+FIGURE A-1/E.522
+
+Triangular network for numerical examples (Example 1)
+
+#### A.2 Numerical results
+
+24 hourly traffic demands are processed. The order of processing are from the hour with the smallest total traffic demand to the hour with the largest total traffic demand. Computational results are given in Table A-1/E.522.
+
+TABLE A-1/E.522
+
+#### Numerical results
+
+| Hour | Hourly traffic demand |        |       | Number of circuits obtained by single hour dimensioning (disregarding lower bounds imposed by the previous iterative stage) |     |     | Number of circuits obtained considering lower bounds imposed by the previous iterative stage |     |     | Number of circuits required to meet multiple hourly traffic demands |     |     |
+|------|-----------------------|--------|-------|-----------------------------------------------------------------------------------------------------------------------------|-----|-----|----------------------------------------------------------------------------------------------|-----|-----|---------------------------------------------------------------------|-----|-----|
+|      | A-B                   | A-C    | C-B   | A-B                                                                                                                         | A-C | C-B | A-B                                                                                          | A-C | C-B | A-B                                                                 | A-C | C-B |
+| 6    | 17.50                 | 5.00   | 3.50  | 17                                                                                                                          | 19  | 17  | 17                                                                                           | 19  | 17  | 17                                                                  | 19  | 17  |
+| 7    | 20.00                 | 5.00   | 3.50  | 19                                                                                                                          | 20  | 18  | 19                                                                                           | 20  | 18  | 19                                                                  | 20  | 18  |
+| 5    | 2.50                  | 5.00   | 28.00 | 1                                                                                                                           | 14  | 41  | 19                                                                                           | 11  | 39  | 19                                                                  | 20  | 39  |
+| 4    | 2.50                  | 5.00   | 35.00 | 1                                                                                                                           | 14  | 49  | 19                                                                                           | 11  | 47  | 19                                                                  | 20  | 47  |
+| 8    | 37.50                 | 5.00   | 3.50  | 37                                                                                                                          | 23  | 22  | 19                                                                                           | 38  | 37  | 19                                                                  | 38  | 47  |
+| 9    | 40.00                 | 5.00   | 3.50  | 39                                                                                                                          | 24  | 23  | 19                                                                                           | 41  | 40  | 19                                                                  | 41  | 47  |
+| 3    | 2.50                  | 5.00   | 45.50 | 1                                                                                                                           | 14  | 61  | 19                                                                                           | 11  | 59  | 19                                                                  | 41  | 59  |
+| 18   | 2.50                  | 50.00  | 3.50  | 1                                                                                                                           | 66  | 12  | 19                                                                                           | 64  | 9   | 19                                                                  | 64  | 59  |
+| 10   | 50.00                 | 5.00   | 3.50  | 49                                                                                                                          | 26  | 25  | 9                                                                                            | 61  | 59  | 19                                                                  | 64  | 59  |
+| 19   | 2.50                  | 60.00  | 3.50  | 1                                                                                                                           | 77  | 12  | 19                                                                                           | 75  | 9   | 19                                                                  | 75  | 59  |
+| 20   | 2.50                  | 60.00  | 3.50  | 1                                                                                                                           | 77  | 12  | 19                                                                                           | 75  | 9   | 19                                                                  | 75  | 59  |
+| 22   | 12.50                 | 30.00  | 24.50 | 12                                                                                                                          | 45  | 39  | 12                                                                                           | 45  | 39  | 19                                                                  | 75  | 59  |
+| 2    | 2.50                  | 5.00   | 63.00 | 1                                                                                                                           | 14  | 80  | 19                                                                                           | 11  | 78  | 19                                                                  | 75  | 78  |
+| 17   | 2.50                  | 70.00  | 3.50  | 1                                                                                                                           | 87  | 12  | 19                                                                                           | 85  | 9   | 19                                                                  | 85  | 78  |
+| 1    | 2.50                  | 5.00   | 70.00 | 1                                                                                                                           | 14  | 87  | 19                                                                                           | 11  | 85  | 19                                                                  | 85  | 85  |
+| 23   | 20.00                 | 20.00  | 42.00 | 19                                                                                                                          | 36  | 60  | 19                                                                                           | 36  | 60  | 19                                                                  | 85  | 85  |
+| 11   | 47.50                 | 25.00  | 17.50 | 47                                                                                                                          | 46  | 38  | 3                                                                                            | 85  | 77  | 19                                                                  | 85  | 85  |
+| 21   | 12.50                 | 55.00  | 24.50 | 12                                                                                                                          | 73  | 39  | 12                                                                                           | 73  | 39  | 19                                                                  | 85  | 85  |
+| 12   | 42.50                 | 30.00  | 21.00 | 42                                                                                                                          | 50  | 41  | 3                                                                                            | 85  | 76  | 19                                                                  | 85  | 85  |
+| 16   | 2.50                  | 90.00  | 3.50  | 1                                                                                                                           | 109 | 12  | 19                                                                                           | 107 | 9   | 19                                                                  | 107 | 85  |
+| 0    | 20.00                 | 20.00  | 66.50 | 19                                                                                                                          | 36  | 87  | 19                                                                                           | 36  | 87  | 19                                                                  | 107 | 87  |
+| 13   | 30.00                 | 65.00  | 35.00 | 29                                                                                                                          | 86  | 54  | 5                                                                                            | 107 | 76  | 19                                                                  | 107 | 87  |
+| 15   | 17.50                 | 100.00 | 28.00 | 17                                                                                                                          | 121 | 44  | 19                                                                                           | 120 | 43  | 19                                                                  | 120 | 87  |
+| 14   | 27.50                 | 95.00  | 38.50 | 27                                                                                                                          | 117 | 57  | 19                                                                                           | 124 | 64  | 19                                                                  | 124 | 87  |
+
+This example relates to an intercontinental network where busy hours of the three traffic relations are widely different among each other. The busy hour of the relation A-C, i.e. hour 15, is a low traffic period for the relations A-B and C-B. The busy hour of the relation C-B, i.e. hour 1, is a low traffic period for the relations A-B and A-C. Similarly, the busy hour of the relation A-B, i.e. hour 10, is a low traffic period for the relations A-C and C-B.
+
+In this case, the single hour dimensioning method, where traffic data during the busy hour of the final circuit group are used for dimensioning, cannot be applied. If the single hour dimensioning method is applied, this results in considerable under-dimensioning.
+
+If all the circuit groups are dimensioned as final, the required number of circuits are 64, 117 and 85 for the circuit groups A-B, A-C and C-B, respectively. About 14% of the total number of circuits is saved by the use of alternate routing.
+
+(to Recommendation E.522)
+
+### **Example of minimum outlay network dimensioning**
+
+![Diagram of a triangular network for numerical example (Example 2). The network consists of three nodes: A, B, and C. Node A is at the bottom left, node B is at the bottom right, and node C is at the top. A solid line connects A and C, labeled 'Final circuit group'. A solid line connects C and B, labeled 'Final circuit group'. A dashed line connects A and B, labeled 'High usage circuit group'. An arrow points from the dashed line to the solid line between C and B, labeled 'Overflow'. The diagram is labeled 'CCITT-69321'.](5a4e62bead259c258d069fd3663ea670_img.jpg)
+
+Diagram of a triangular network for numerical example (Example 2). The network consists of three nodes: A, B, and C. Node A is at the bottom left, node B is at the bottom right, and node C is at the top. A solid line connects A and C, labeled 'Final circuit group'. A solid line connects C and B, labeled 'Final circuit group'. A dashed line connects A and B, labeled 'High usage circuit group'. An arrow points from the dashed line to the solid line between C and B, labeled 'Overflow'. The diagram is labeled 'CCITT-69321'.
+
+FIGURE B-1/E.522
+
+Triangular network for numerical example (Example 2)
+
+#### B.1 *Assumptions* (see also Figure B-1/E.522)
+
+Calculations are performed under the following conditions:
+
+- 1) Time difference:  
+ A is 3 hours west of B  
+ A is 3 hours west of C  
+ No time difference between B and C
+- 2) Traffic profiles:  
+ 24-hour traffic profiles as per Table 1/E.523 are used.
+- 3) Busy hour traffic:  
+ A-B 16 erlangs  
+ A-C 33 erlangs  
+ C-B 33 erlangs
+- 4) Each Administration monthly cost per circuit:  
+ A-B 1000 units  
+ A-C 1000 units  
+ C-B 800 units
+- 5) Transit charge per holding minute to each terminal Administration:  
+ 1/2 unit
+- 6) Conversion factors:
+  - i) Holding minutes/erlangs: 60
+  - ii) Daily overflow/busy hour overflow  
+ This conversion factor ( $F$ ) is calculated according to the guideline given in § 2.4.
+  - iii) Monthly overflow/daily overflow: 26  
+ where medium social contact per Recommendation E.502 is assumed.
+- 7) Grade-of-service (GOS) on final circuit groups: 0.01
+
+#### B.2 *Numerical results*
+
+Numerical results are shown in Table B-1/E.522. The number of circuits C-B does not increase because of the 24-hour traffic profiles matching. The number of high usage circuits A-B in the minimum outlay network is larger than that in the minimum cost network. The impact of considering transit charges in dimensionings is always in the direction of less overflow.
+
+TABLE B-1/E.522
+
+##### Numerical results
+
+| Network results                |                    |     |     | Economic results ( × 1000 units/month) |    |    |                 |     |        |                            |      |      |
+|--------------------------------|--------------------|-----|-----|----------------------------------------|----|----|-----------------|-----|--------|----------------------------|------|------|
+| Busy-hour overflow probability | Number of circuits |     |     | Circuits costs                         |    |    | Transit charges |     |        | Total outlay               |      |      |
+|                                | A-B                | A-C | C-B | A                                      | B  | C  | A               | B   | C      | A                          | B    | C    |
+| 0.0000                         | 25                 | 45  | 45  | 70                                     | 61 | 81 | –               | –   | –      | 70.0                       | 61.0 | 81.0 |
+| 0.0090                         | 25                 | 45  | 45  | 70                                     | 61 | 81 | 0.3             | 0.3 | (0.7)  | 70.3                       | 61.3 | 80.3 |
+| 0.0151                         | 24                 | 45  | 45  | 69                                     | 60 | 81 | 0.6             | 0.6 | (1.3)  | 69.6                       | 60.6 | 79.7 |
+| 0.0221                         | 23                 | 45  | 45  | 68                                     | 59 | 81 | 0.9             | 0.9 | (1.9)  | 68.9                       | 59.9 | 79.1 |
+| 0.0331                         | 22                 | 46  | 45  | 68                                     | 58 | 82 | 1.4             | 1.4 | (2.9)  | 69.4                       | 59.4 | 79.1 |
+| 0.0471                         | 21                 | 46  | 45  | 67                                     | 57 | 82 | 2.1             | 2.1 | (4.2)  | 69.1                       | 59.1 | 77.8 |
+| 0.0641                         | 20                 | 46  | 45  | 66                                     | 56 | 82 | 3.0             | 3.0 | (6.0)  | 69.0                       | 59.0 | 76.0 |
+|                                |                    |     |     |                                        |    |    |                 |     |        | Minimum outlay for A and B |      |      |
+| 0.0861                         | 19                 | 47  | 45  | 66                                     | 55 | 83 | 4.2             | 4.2 | (8.4)  | 70.2                       | 59.2 | 74.5 |
+| 0.1121                         | 18                 | 47  | 45  | 65                                     | 54 | 83 | 5.7             | 5.7 | (11.5) | 70.7                       | 59.7 | 71.5 |
+|                                |                    |     |     |                                        |    |    |                 |     |        | Minimum cost network       |      |      |
+| 0.142                          | 17                 | 48  | 45  | 65                                     | 53 | 84 | 7.6             | 7.6 | (15.1) | 72.6                       | 60.6 | 68.9 |
+| 0.175                          | 16                 | 49  | 45  | 65                                     | 52 | 85 | 9.7             | 9.7 | (19.4) | 74.7                       | 61.7 | 65.6 |
+
+## References
+
+- [1] WILKINSON (R. I.): Theories for toll traffic engineering in the USA, *Bell Syst. Tech. J.*, 1956, No. 35, pp. 421-514.
+- [2] WILKINSON (R.I.): Simplified engineering of single stage alternate routing systems, *Fourth International Teletraffic Congress*, London., 1964.
+- [3] RAPP (Y.): Planning of junction network in a multi-exchange area. 1. General Principles, *Ericsson Tech*; 1964, No. 20, 1, pp. 77-130.
+- [4] LEVINE (S. W.) and WERNANDER (M. A.): Modular engineering of trunk groups for traffic requirements, *Fifth International Teletraffic Congress*, New York, 1967.
+- [5] PRATT (C. W.): The concept of marginal overflow in alternate routing, *Fifth International Teletraffic Congress*, New York, 1967.
+- [6] EISENBERG (M.): Engineering traffic networks for more than one busy hour, *Bell System Tech. J.*, 1977, Vol. 56, pp. 1-20.
+- [7] AKIMARU (H.) *et al.*: Derivatives of Wilkinson formula and their application to optimum design of alternative routing systems, *Ninth International Teletraffic Congress*, Torremolinos, 1979.
+- [8] HORN (R. W.): A simple approach to dimensioning a telecommunication network for many hours of traffic demand, *International Conference on Communications*, Denver, 1981.
+- [9] BESHA (M. E.): Traffic data reduction for multiple-hour network dimensioning, *Second International Network Planning Symposium*, Brighton, 1983.
+- [10] LINDBERGER (K.): Simple approximations of overflow system quantities for additional demands in the optimization, *Tenth International Teletraffic Congress*, Montreal, 1983.

marked/E/T-REC-E.523-198811-I_PDF-E/raw.md

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+
+
+![ITU logo](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg)
+
+The logo of the International Telecommunication Union (ITU) features the letters 'ITU' in a bold, sans-serif font, superimposed on a stylized globe with intersecting lines.
+
+ITU logo
+
+INTERNATIONAL TELECOMMUNICATION UNION
+
+**ITU-T**
+
+**E.523**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+**TELEPHONE NETWORK AND ISDN**
+
+**QUALITY OF SERVICE, NETWORK MANAGEMENT  
+AND TRAFFIC ENGINEERING**
+
+---
+
+**STANDARD TRAFFIC PROFILES FOR  
+INTERNATIONAL TRAFFIC STREAMS**
+
+**ITU-T Recommendation E.523**
+
+(Extract from the *Blue Book*)
+
+---
+
+# NOTES
+
+1 ITU-T Recommendation E.523 was published in Fascicle II.3 of the *Blue Book*. This file is an extract from the *Blue Book*. While the presentation and layout of the text might be slightly different from the *Blue Book* version, the contents of the file are identical to the *Blue Book* version and copyright conditions remain unchanged (see below).
+
+2 In this Recommendation, the expression “Administration” is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+# **STANDARD TRAFFIC PROFILES FOR INTERNATIONAL TRAFFIC STREAMS**
+
+The worldwide nature of the international telephone network, spanning as it does all possible time zones, has stimulated studies of the traffic streams between countries in different relative time locations. These studies have led to the development of standardized 24-hour traffic profiles which, theoretically based and verified by measurements, would be useful for engineering purposes. In fact, these concepts can be applied to a variety of network situations:
+
+- i) variable access satellite working where a large number of traffic streams with possibly differing traffic profiles share the pool of satellite circuits;
+- ii) combining of traffic streams on groups of terrestrial circuits which may be either high-usage or final choice routes;
+- iii) detour routing of traffic between origin and destination countries to take advantage of prevailing low load conditions on the detour path.
+
+In developing any such applications, account must be taken of the International Routing Plan (Recommendation E.171 [1]) and of accepted accounting principles (Recommendation D.150 [2]).
+
+It must be recognized that the preferred basis for dimensioning consists of traffic profiles based on real traffic. Nevertheless, many countries have found the standard profiles presented in this Recommendation very useful where streams are too small to obtain reliable measurements or where no measurements are available.
+
+For both-way profiles, two equivalent methods of presentation are given in chart and tabular form. In Figure 1/E.523 hour-by-hour traffic volumes are shown in diagrammatically as percentages of the total daily traffic volume; such percentages are particularly convenient for tariff studies. In Table 1/E.523, hourly traffics are expressed as percentages of the busy hour traffic, and this is convenient for engineering purposes. Time zone differences are given in whole hours only. Directional profiles are given in Tables 2/E.523 and 3/E.523.
+
+Although tables are given for both-way and directional traffic streams, it must be emphasized that at this stage only the both-way profiles can be regarded as soundly supported by measurement. The directional profiles are theoretically based and supported by some measurements, but should be used with caution until adequate verification has been achieved.
+
+The theoretical basis for the profiles presented here is contained in Annex A. It depends on a convenience function  $f(t)$  which represents the profile of *local* daily traffic, where of course no time zone difference exists. The function  $f(t)$  used for computation of the standard profile was derived by mathematical manipulation of measurements of the Tokyo-Oakland and Tokyo-Vancouver streams. Although these results have been supported by other measurements, it leaves open the possibility that the convenience function may vary from one country to another and that, strictly, these should be derived independently and then used to obtain a calculated profile for the international relation. It also seems that the convenience function for the country of destination should be given greater weight than that for the country of origin. These remarks suggest possible refinements, but are not quantified in this Recommendation.
+
+![A grid of 13 histograms showing standard hourly both-way traffic distribution patterns for time differences from 0 to 12 hours. Each graph plots percentage of daily traffic volume against local time.](5d92d5c9cc01a262b0389d138caa9aea_img.jpg)
+
+The figure consists of 13 histograms. The first graph is labeled 'No time difference'. The others are labeled '1 hour' through '12 hours'. Each graph shows the hourly traffic volume as a percentage of the daily total. The base pattern ('No time difference') shows low traffic (approx. 1%) from 00:00 to 07:00, rising to a morning peak of ~10% at 10:00-11:00, a slight dip at midday, an afternoon peak of ~11% at 15:00-16:00, and then declining back to low levels by midnight. Subsequent graphs show this same profile shifted horizontally to the right by the number of hours indicated in their labels.
+
+| Local Time    | Traffic Volume (%) |
+|---------------|--------------------|
+| 03:00 - 08:00 | ~1%                |
+| 09:00         | ~6%                |
+| 10:00         | ~10%               |
+| 11:00         | ~10%               |
+| 12:00         | ~8%                |
+| 13:00         | ~9%                |
+| 14:00         | ~10%               |
+| 15:00         | ~11%               |
+| 16:00         | ~10%               |
+| 17:00         | ~8%                |
+| 18:00         | ~6%                |
+| 19:00 - 02:00 | ~4% to 1%          |
+
+A grid of 13 histograms showing standard hourly both-way traffic distribution patterns for time differences from 0 to 12 hours. Each graph plots percentage of daily traffic volume against local time.
+
+CCITT - 48101
+
+*Note* – The vertical scale gives the hourly traffic volume as a percentage of the daily traffic volume. The horizontal scales show the local times.
+
+FIGURE 1/E.523  
+**Standard hourly both-way traffic distribution patterns**
+
+TABLE 1/E.523
+
+## **Standard hourly bothway traffic patterns**
+
+|                                                  |    | Local time in the more westerly country |   |   |   |   |   |    |    |    |     |     |     |    |    |    |    |    |    |    |    |    |     |    |    | BH<br>% |
+|--------------------------------------------------|----|-----------------------------------------|---|---|---|---|---|----|----|----|-----|-----|-----|----|----|----|----|----|----|----|----|----|-----|----|----|---------|
+|                                                  |    | 0                                       | 1 | 2 | 3 | 4 | 5 | 6  | 7  | 8  | 9   | 10  | 11  | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21  | 22 | 23 |         |
+| Time difference (in hours) between two countries | 0  | 5                                       | 5 | 5 | 5 | 5 | 5 | 10 | 10 | 50 | 90  | 100 | 95  | 85 | 70 | 85 | 85 | 70 | 45 | 25 | 40 | 40 | 35  | 20 | 15 | 10.0    |
+|                                                  | 1  | 5                                       | 5 | 5 | 5 | 5 | 5 | 10 | 25 | 70 | 95  | 100 | 90  | 80 | 80 | 85 | 80 | 60 | 35 | 30 | 40 | 35 | 25  | 15 | 10 | 10.0    |
+|                                                  | 2  | 5                                       | 5 | 5 | 5 | 5 | 5 | 20 | 30 | 75 | 100 | 100 | 90  | 90 | 85 | 85 | 65 | 45 | 45 | 35 | 40 | 30 | 25  | 15 | 5  | 10.0    |
+|                                                  | 3  | 5                                       | 5 | 5 | 5 | 5 | 5 | 25 | 35 | 75 | 100 | 95  | 100 | 95 | 80 | 70 | 50 | 60 | 45 | 35 | 30 | 25 | 15  | 5  | 5  | 10.4    |
+|                                                  | 4  | 5                                       | 5 | 5 | 5 | 5 | 5 | 25 | 35 | 65 | 85  | 100 | 100 | 85 | 60 | 50 | 60 | 55 | 40 | 25 | 25 | 20 | 5   | 5  | 5  | 11.5    |
+|                                                  | 5  | 5                                       | 5 | 5 | 5 | 5 | 5 | 25 | 30 | 65 | 95  | 100 | 90  | 70 | 50 | 60 | 60 | 55 | 30 | 20 | 20 | 5  | 5   | 5  | 5  | 12.4    |
+|                                                  | 6  | 10                                      | 5 | 5 | 5 | 5 | 5 | 25 | 30 | 75 | 100 | 100 | 75  | 55 | 60 | 65 | 60 | 40 | 25 | 15 | 5  | 5  | 5   | 5  | 5  | 13.1    |
+|                                                  | 7  | 10                                      | 5 | 5 | 5 | 5 | 5 | 25 | 35 | 80 | 100 | 85  | 55  | 70 | 65 | 65 | 50 | 40 | 20 | 5  | 5  | 5  | 5   | 5  | 10 | 13.5    |
+|                                                  | 8  | 25                                      | 5 | 5 | 5 | 5 | 5 | 35 | 45 | 95 | 100 | 80  | 95  | 90 | 75 | 60 | 50 | 35 | 5  | 5  | 5  | 5  | 5   | 20 | 20 | 11.7    |
+|                                                  | 9  | 40                                      | 5 | 5 | 5 | 5 | 5 | 35 | 40 | 75 | 80  | 100 | 95  | 85 | 60 | 55 | 35 | 5  | 5  | 5  | 5  | 5  | 25  | 25 | 40 | 12.1    |
+|                                                  | 10 | 40                                      | 5 | 5 | 5 | 5 | 5 | 35 | 35 | 60 | 95  | 100 | 90  | 65 | 50 | 40 | 5  | 5  | 5  | 5  | 5  | 25 | 30  | 50 | 55 | 12.5    |
+|                                                  | 11 | 40                                      | 5 | 5 | 5 | 5 | 5 | 30 | 25 | 75 | 100 | 95  | 70  | 55 | 35 | 5  | 5  | 5  | 5  | 5  | 25 | 30 | 65  | 70 | 60 | 12.3    |
+|                                                  | 12 | 40                                      | 5 | 5 | 5 | 5 | 5 | 20 | 35 | 80 | 100 | 80  | 65  | 40 | 5  | 5  | 5  | 5  | 5  | 20 | 35 | 60 | 100 | 80 | 65 | 11.3    |
+
+*Note 1* - The 24-hour profile of both-way traffic between any two countries is read from left to right from the appropriate row of the table; all time differences can be expressed in the range 0-12 hours. Each entry is expressed as a percentage of the busy hour traffic.
+
+*Note 2* - The *more westerly* country of a traffic relation is the one from which we can proceed eastwards to the other through time zones not exceeding 12 hours.
+
+*Note 3* - For network planning studies, UTC (Universal Coordinated Time) would normally be used so that all traffic streams are processed time consistently. Clearly if the more westerly country is  $W$  hours ahead of UTC (ignoring the international dateline), then the traffic at 0000-0100 UTC is obtained from the row corresponding to the time difference between the two countries at the column headed  $W$ . Alternatively, the first entry in the appropriate row gives the relative traffic intensity for the hour  $(24 - W)$  to  $(25 - W)$ .
+
+Example: For the traffic stream between the U.K. (UTC + 1 hour) and the central zone of USA (UTC + 18 hours), the time difference is 7 hours and the USA is regarded as the more westerly country, hence  $W = 18$ . Thus from the table, the traffic during 0000-0100 UTC is 5 % of the busy hour traffic, and the busy hour is 1500-1600 UTC.
+
+*Note 4* - The column headed "BH %" gives the busy hour traffic volume as a percentage of the daily traffic volume.
+
+TABLE 2/E.523
+
+## **Diurnal distributions of eastbound international telephone traffic**
+
+|                                                  |    | Local time in the more westerly country |   |   |   |   |   |    |    |     |     |     |     |    |    |    |    |    |    |    |    |    |     |     |     |
+|--------------------------------------------------|----|-----------------------------------------|---|---|---|---|---|----|----|-----|-----|-----|-----|----|----|----|----|----|----|----|----|----|-----|-----|-----|
+|                                                  |    | 0                                       | 1 | 2 | 3 | 4 | 5 | 6  | 7  | 8   | 9   | 10  | 11  | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21  | 22  | 23  |
+| Time difference (in hours) between two countries | 0  | 10                                      | 5 | 5 | 5 | 5 | 5 | 10 | 10 | 50  | 90  | 100 | 95  | 85 | 70 | 85 | 85 | 70 | 45 | 25 | 40 | 40 | 35  | 20  | 15  |
+|                                                  | 1  | 5                                       | 5 | 5 | 5 | 5 | 5 | 10 | 30 | 80  | 95  | 100 | 90  | 80 | 80 | 85 | 80 | 60 | 35 | 30 | 40 | 35 | 25  | 15  | 10  |
+|                                                  | 2  | 5                                       | 5 | 5 | 5 | 5 | 5 | 25 | 40 | 85  | 100 | 100 | 90  | 90 | 85 | 85 | 60 | 40 | 45 | 35 | 40 | 25 | 20  | 15  | 5   |
+|                                                  | 3  | 5                                       | 5 | 5 | 5 | 5 | 5 | 40 | 50 | 90  | 100 | 95  | 100 | 95 | 80 | 65 | 40 | 55 | 45 | 35 | 25 | 20 | 10  | 5   | 5   |
+|                                                  | 4  | 5                                       | 5 | 5 | 5 | 5 | 5 | 35 | 50 | 70  | 85  | 100 | 100 | 85 | 60 | 40 | 50 | 50 | 40 | 25 | 20 | 15 | 5   | 5   | 5   |
+|                                                  | 5  | 5                                       | 5 | 5 | 5 | 5 | 5 | 30 | 40 | 70  | 95  | 100 | 90  | 65 | 45 | 50 | 50 | 50 | 25 | 20 | 15 | 5  | 5   | 5   | 5   |
+|                                                  | 6  | 10                                      | 5 | 5 | 5 | 5 | 5 | 40 | 45 | 85  | 100 | 100 | 65  | 45 | 55 | 55 | 50 | 30 | 20 | 15 | 5  | 5  | 5   | 5   | 5   |
+|                                                  | 7  | 10                                      | 5 | 5 | 5 | 5 | 5 | 40 | 50 | 90  | 100 | 75  | 40  | 60 | 55 | 55 | 40 | 30 | 10 | 5  | 5  | 5  | 5   | 5   | 10  |
+|                                                  | 8  | 25                                      | 5 | 5 | 5 | 5 | 5 | 55 | 65 | 100 | 100 | 70  | 90  | 85 | 70 | 45 | 35 | 25 | 5  | 5  | 5  | 5  | 5   | 20  | 20  |
+|                                                  | 9  | 50                                      | 5 | 5 | 5 | 5 | 5 | 40 | 45 | 70  | 75  | 100 | 100 | 85 | 55 | 50 | 35 | 5  | 5  | 5  | 5  | 5  | 25  | 35  | 60  |
+|                                                  | 10 | 65                                      | 5 | 5 | 5 | 5 | 5 | 45 | 45 | 60  | 95  | 100 | 90  | 60 | 45 | 35 | 5  | 5  | 5  | 5  | 5  | 25 | 30  | 75  | 100 |
+|                                                  | 11 | 65                                      | 5 | 5 | 5 | 5 | 5 | 40 | 40 | 75  | 90  | 80  | 55  | 40 | 25 | 5  | 5  | 5  | 5  | 5  | 20 | 25 | 80  | 100 | 95  |
+|                                                  | 12 | 55                                      | 5 | 5 | 5 | 5 | 5 | 20 | 40 | 65  | 70  | 50  | 40  | 20 | 5  | 5  | 5  | 5  | 5  | 20 | 25 | 70 | 100 | 90  | 80  |
+
+*Note* – This table is based on  $p = 1.4$ ,  $q = 0.6$ , i.e. greater weight is given to the convenience function of the called party (see Annex A).
+
+TABLE 3/E.523
+
+## **Diurnal distributions of westbound international telephone traffic**
+
+|                                                  |    | Local time in the more westerly country |   |   |   |   |   |    |    |    |     |     |     |    |    |    |    |    |    |    |    |    |    |    |    |
+|--------------------------------------------------|----|-----------------------------------------|---|---|---|---|---|----|----|----|-----|-----|-----|----|----|----|----|----|----|----|----|----|----|----|----|
+|                                                  |    | 0                                       | 1 | 2 | 3 | 4 | 5 | 6  | 7  | 8  | 9   | 10  | 11  | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 |
+| Time difference (in hours) between two countries | 0  | 10                                      | 5 | 5 | 5 | 5 | 5 | 10 | 10 | 50 | 90  | 100 | 95  | 85 | 70 | 85 | 85 | 70 | 45 | 25 | 40 | 40 | 35 | 20 | 15 |
+|                                                  | 1  | 5                                       | 5 | 5 | 5 | 5 | 5 | 10 | 20 | 60 | 95  | 100 | 90  | 80 | 80 | 85 | 80 | 60 | 35 | 30 | 40 | 35 | 25 | 15 | 10 |
+|                                                  | 2  | 5                                       | 5 | 5 | 5 | 5 | 5 | 15 | 20 | 65 | 100 | 100 | 90  | 90 | 85 | 85 | 70 | 50 | 45 | 35 | 40 | 35 | 30 | 15 | 5  |
+|                                                  | 3  | 5                                       | 5 | 5 | 5 | 5 | 5 | 10 | 20 | 60 | 100 | 95  | 100 | 95 | 80 | 75 | 60 | 65 | 45 | 35 | 35 | 30 | 15 | 5  | 5  |
+|                                                  | 4  | 5                                       | 5 | 5 | 5 | 5 | 5 | 15 | 20 | 60 | 85  | 100 | 100 | 85 | 60 | 60 | 70 | 60 | 40 | 25 | 30 | 25 | 5  | 5  | 5  |
+|                                                  | 5  | 5                                       | 5 | 5 | 5 | 5 | 5 | 20 | 20 | 60 | 95  | 100 | 90  | 75 | 55 | 70 | 70 | 60 | 35 | 20 | 25 | 5  | 5  | 5  | 5  |
+|                                                  | 6  | 10                                      | 5 | 5 | 5 | 5 | 5 | 10 | 15 | 65 | 100 | 100 | 85  | 65 | 65 | 75 | 70 | 50 | 30 | 15 | 5  | 5  | 5  | 5  | 5  |
+|                                                  | 7  | 10                                      | 5 | 5 | 5 | 5 | 5 | 10 | 20 | 70 | 100 | 95  | 70  | 80 | 75 | 75 | 60 | 50 | 30 | 5  | 5  | 5  | 5  | 5  | 10 |
+|                                                  | 8  | 20                                      | 5 | 5 | 5 | 5 | 5 | 15 | 25 | 90 | 100 | 90  | 95  | 95 | 80 | 75 | 65 | 45 | 5  | 5  | 5  | 5  | 5  | 20 | 20 |
+|                                                  | 9  | 25                                      | 5 | 5 | 5 | 5 | 5 | 30 | 35 | 80 | 85  | 100 | 95  | 85 | 65 | 60 | 35 | 5  | 5  | 5  | 5  | 5  | 20 | 20 | 25 |
+|                                                  | 10 | 10                                      | 5 | 5 | 5 | 5 | 5 | 25 | 25 | 60 | 95  | 100 | 90  | 70 | 55 | 45 | 5  | 5  | 5  | 5  | 5  | 25 | 30 | 25 | 10 |
+|                                                  | 11 | 15                                      | 5 | 5 | 5 | 5 | 5 | 10 | 10 | 65 | 95  | 100 | 80  | 65 | 45 | 5  | 5  | 5  | 5  | 5  | 25 | 35 | 40 | 35 | 25 |
+|                                                  | 12 | 20                                      | 5 | 5 | 5 | 5 | 5 | 20 | 25 | 70 | 100 | 90  | 80  | 55 | 5  | 5  | 5  | 5  | 5  | 20 | 40 | 65 | 70 | 50 | 40 |
+
+*Note* – This table is based on  $p = 1.4$ ,  $q = 0.6$ , i.e. greater weight is given to the convenience function of the called party (see Annex A).
+
+(to Recommendation E.523)
+
+## **Mathematical expression for the influence of time differences on the traffic flow**
+
+A telephone call is initiated when a person wishes to call someone else, but both parties have to be on the line before the call is established. It is considered that a telephone call is made at a time which tends to be convenient for both the calling and called parties. The *degree of convenience* for making a telephone call is considered to be a periodical function of time  $t$ , whose period is 24 hours. When the time difference between both parties is zero, the degree of convenience is denoted by  $f(t)$ , where  $t$  is local standard time. The graphic shape of the basic function  $f(t)$  will be determined by the daily pattern of human activities, and will resemble, or fairly closely coincide with, the hour by hour traffic distribution in the national (or local) telephone network.
+
+It is assumed that the hourly traffic distribution  $F_\tau(t)$ , when a time difference of  $\tau$  hours exists between the originating and called locations, is expressed as the geometric mean of convenience functions of two locations  $\tau$  hours apart:
+
+$$F_\tau(t) = k \{ f(t) \cdot f(t + \tau) \}^{1/2}$$
+
+where
+
+$$k = 1 / \int_{24 \text{ hours}} \{ f(t) \cdot f(t + \tau) \}^{1/2} dt \quad (\text{A-1})$$
+
+The sign of  $\tau$  is positive when the time at the destination is ahead of the reference time, and negative when the time of destination is behind the reference time.
+
+The distribution of equation (A-1) represents the sum of the outgoing and incoming traffics. Expressions for the one-way hourly traffic distributions can also be obtained by extending the concept of convenience function as follows.
+
+Define convenience functions both for the caller  $f_0(t)$  and for the called party  $f_i(t)$ . Then the one-way traffic distributions of east-bound and west-bound telephone calls, for the case of  $\tau$  hour time-difference, are similarly expressed as follows:
+
+$$F_{\tau, \text{east}}(t) = k \{ f_0(t) \cdot f_i(t + \tau) \}^{1/2}$$
+
+$$k = 1 / \int_{24 \text{ hours}} \{ f_0(t) \cdot f_i(t + \tau) \}^{1/2} dt \quad (\text{A-2})$$
+
+$$F_{\tau, \text{west}}(t) = k \{ f_i(t) \cdot f_0(t + \tau) \}^{1/2}$$
+
+$$k = 1 / \int_{24 \text{ hours}} \{ f_i(t) \cdot f_0(t + \tau) \}^{1/2} dt \quad (\text{A-3})$$
+
+where
+
+$t$  is the local standard time of the west station and
+
+$\tau$  is positive.
+
+It is natural that a caller makes a call considering the convenience of the called person, and therefore the convenience function of the called person  $f_i$  contributes more than the convenience of the caller  $f_0$  to the directional distribution  $F$ . They can be written as follows:
+
+$$f_i(t) = k_1 \{f(t)\}^p, \quad f_0(t) = k_2 \{f(t)\}^q, \quad (A-4)$$
+
+where
+
+$$p > q \quad \text{and} \quad p + q = 2,$$
+
+and where  $k_1$  and  $k_2$  are normalizing coefficients to ensure that:
+
+$$\int_{24\text{hours}} f_i(t) dt = 1, \quad \int_{24\text{hours}} f_0(t) dt = 1.$$
+
+As to the values of  $p$  and  $q$  in equation (A-4), it has been found empirically that the convenience of the called side  $p$  is considerably larger than that of originating side  $q$ , and appropriate values are roughly  $p = 1.4$  and consequently  $q = 0.6$ .
+
+# References
+
+- [1] CCITT Recommendation *International telephone routing plan*, Rec. E. 171.
+- [2] CCITT Recommendation *New system for accounting in international telephony*, Rec. D.150.
+
+# Bibliography
+
+CASEY(J. Jr.) and SHIMASAKI (N.): Optimal dimensioning of a satellite network using alternate routing concepts, *Sixth International Teletraffic Convention*, Munich, 1970.
+
+RAPP (Y.): Planning of a junction network with non-coincident busy hours, *Ericsson Technics*, No. 1, 1971.
+
+CABALLERO (P. A.) and DIAZ (F.): Optimization of networks of hierarchical structure with non-coincident busy hours, *Seventh International Teletraffic Convention*, Stockholm, 1973.
+
+OTHA (T.): Network efficiency and network planning considering telecommunication traffic influenced by time difference, *Seventh International Teletraffic Convention*, Stockholm, 1973.

marked/E/T-REC-E.524-199905-I_PDF-E/raw.md

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+
+
+![ITU logo: A globe with the letters ITU and a lightning bolt.](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg)
+
+ITU logo: A globe with the letters ITU and a lightning bolt.
+
+INTERNATIONAL TELECOMMUNICATION UNION
+
+**ITU-T**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+**E.524**
+
+(05/99)
+
+SERIES E: OVERALL NETWORK OPERATION,  
+TELEPHONE SERVICE, SERVICE OPERATION AND  
+HUMAN FACTORS
+
+Quality of service, network management and traffic  
+engineering – Traffic engineering – Determination of the  
+number of circuits in automatic and semi-automatic  
+operation
+
+---
+
+**Overflow approximations for non-random inputs**
+
+ITU-T Recommendation E.524
+
+(Previously CCITT Recommendation)
+
+---
+
+# OVERALL NETWORK OPERATION, TELEPHONE SERVICE, SERVICE OPERATION AND HUMAN FACTORS
+
+## **OPERATION, NUMBERING, ROUTING AND MOBILE SERVICES**
+
+## INTERNATIONAL OPERATION
+
+|                                                        |             |
+|--------------------------------------------------------|-------------|
+| Definitions                                            | E.100–E.103 |
+| General provisions concerning Administrations          | E.104–E.119 |
+| General provisions concerning users                    | E.120–E.139 |
+| Operation of international telephone services          | E.140–E.159 |
+| Numbering plan of the international telephone service  | E.160–E.169 |
+| International routing plan                             | E.170–E.179 |
+| Tones in national signalling systems                   | E.180–E.199 |
+| Maritime mobile service and public land mobile service | E.200–E.229 |
+
+## OPERATIONAL PROVISIONS RELATING TO CHARGING AND ACCOUNTING IN THE INTERNATIONAL TELEPHONE SERVICE
+
+|                                                                |             |
+|----------------------------------------------------------------|-------------|
+| Charging in the international telephone service                | E.230–E.249 |
+| Measuring and recording call durations for accounting purposes | E.260–E.269 |
+
+## UTILIZATION OF THE INTERNATIONAL TELEPHONE NETWORK FOR NON-TELEPHONY APPLICATIONS
+
+|                 |             |
+|-----------------|-------------|
+| General         | E.300–E.319 |
+| Phototelegraphy | E.320–E.329 |
+
+## ISDN PROVISIONS CONCERNING USERS
+
+E.330–E.399
+
+# **QUALITY OF SERVICE, NETWORK MANAGEMENT AND TRAFFIC ENGINEERING**
+
+### NETWORK MANAGEMENT
+
+|                                                             |             |
+|-------------------------------------------------------------|-------------|
+| International service statistics                            | E.400–E.409 |
+| International network management                            | E.410–E.419 |
+| Checking the quality of the international telephone service | E.420–E.489 |
+
+### TRAFFIC ENGINEERING
+
+|                                                             |             |
+|-------------------------------------------------------------|-------------|
+| Measurement and recording of traffic                        | E.490–E.505 |
+| Forecasting of traffic                                      | E.506–E.509 |
+| Determination of the number of circuits in manual operation | E.510–E.519 |
+
+|                                                                                          |                    |
+|------------------------------------------------------------------------------------------|--------------------|
+| <b>Determination of the number of circuits in automatic and semi-automatic operation</b> | <b>E.520–E.539</b> |
+|------------------------------------------------------------------------------------------|--------------------|
+
+|                                    |             |
+|------------------------------------|-------------|
+| Grade of service                   | E.540–E.599 |
+| Definitions                        | E.600–E.699 |
+| ISDN traffic engineering           | E.700–E.749 |
+| Mobile network traffic engineering | E.750–E.799 |
+
+# QUALITY OF TELECOMMUNICATION SERVICES: CONCEPTS, MODELS, OBJECTIVES AND DEPENDABILITY PLANNING
+
+|                                                                                             |             |
+|---------------------------------------------------------------------------------------------|-------------|
+| Terms and definitions related to the quality of telecommunication services                  | E.800–E.809 |
+| Models for telecommunication services                                                       | E.810–E.844 |
+| Objectives for quality of service and related concepts of telecommunication services        | E.845–E.859 |
+| Use of quality of service objectives for planning of telecommunication networks             | E.860–E.879 |
+| Field data collection and evaluation on the performance of equipment, networks and services | E.880–E.899 |
+
+# **OVERFLOW APPROXIMATIONS FOR NON-RANDOM INPUTS**
+
+## **Summary**
+
+To ensure accurate network design and planning in the presence of multiple streams (arising, e.g. from different services on the same network), it is imperative to determine the individual means and variances of the overflows of the different traffic streams offered to a common trunk group arrangement. The exact calculation of these parameters for the individual overflow streams is a very hard problem. Thus, this Recommendation introduces different approximate methods for the calculation of the individual overflows. These methods are evaluated in terms of accuracy, processing time, memory requirements and programming effort. This Recommendation also provides sample numerical results based on exact calculations to which the results based on these methods may be compared.
+
+## **Source**
+
+ITU-T Recommendation E.524 was revised by ITU-T Study Group 2 (1997-2000) and was approved under the WTSC Resolution No. 1 procedure on the 10th of May 1999.
+
+# FOREWORD
+
+ITU (International Telecommunication Union) is the United Nations Specialized Agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the ITU. The ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis.
+
+The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics.
+
+The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Resolution No. 1.
+
+In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC.
+
+## NOTE
+
+In this Recommendation the term *recognized operating agency (ROA)* includes any individual, company, corporation or governmental organization that operates a public correspondence service. The terms *Administration*, *ROA* and *public correspondence* are defined in the *Constitution of the ITU (Geneva, 1992)*.
+
+## INTELLECTUAL PROPERTY RIGHTS
+
+The ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. The ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process.
+
+As of the date of approval of this Recommendation, the ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database.
+
+© ITU 1999
+
+All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU.
+
+## CONTENTS
+
+|       |                                                 | <b>Page</b> |
+|-------|-------------------------------------------------|-------------|
+| 1     | Scope .....                                     | 1           |
+| 2     | References .....                                | 1           |
+| 3     | Terms and definitions.....                      | 1           |
+| 4     | Abbreviations .....                             | 1           |
+| 5     | Introduction .....                              | 1           |
+| 6     | Proposed methods .....                          | 2           |
+| 6.1   | IPP method .....                                | 2           |
+| 6.2   | EC method.....                                  | 3           |
+| 6.3   | AWW method .....                                | 3           |
+| 6.3.1 | Blocking of overflow traffic.....               | 4           |
+| 6.3.2 | Wallström formula for individual blocking ..... | 4           |
+| 6.3.3 | Handling of overflow variances .....            | 4           |
+| 6.4   | EPS method .....                                | 5           |
+| 7     | Examples and criteria for comparison.....       | 6           |
+| 8     | Summary of results.....                         | 12          |
+| 9     | History .....                                   | 12          |
+
+
+
+###### Recommendation E.524
+
+# OVERFLOW APPROXIMATIONS FOR NON-RANDOM INPUTS
+
+(revised in 1999)
+
+# 1 Scope
+
+This Recommendation introduces approximate methods for the calculation of means and variances of overflows for individual (non-random) traffic streams offered to a circuit group arrangement.
+
+# 2 References
+
+The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; all users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published.
+
+- CCITT Recommendation E.521 (1988), *Calculation of the number of circuits in a group carrying overflow traffic*.
+- ITU-T Recommendation E.600 (1993), *Terms and definitions of traffic engineering*.
+
+# 3 Terms and definitions
+
+General terms and definitions are given in Recommendation E.600; notations used in the description of the proposed methods appear with the methods themselves in clause 6.
+
+# 4 Abbreviations
+
+This Recommendation uses the following abbreviations:
+
+|     |                                 |
+|-----|---------------------------------|
+| AWW | approximate Wilkinson Wallström |
+| EC  | equivalent capacity             |
+| EPS | equivalent Poisson stream       |
+| ERT | equivalent random traffic       |
+| IPP | interrupted Poisson process     |
+
+# 5 Introduction
+
+This Recommendation provides approximate methods for the calculation of means and variances of overflows for individual (non-random) traffic streams in a circuit group arrangement.
+
+The considered methods are necessary complements to those included in the existing Recommendation E.521 where it is required to take into account concepts such as cluster engineering with service equalization, service protection and end-to-end grade of service. Recommendation E.521 is then insufficient as it is concerned with the grade of service for only one non-random traffic stream in a circuit group.
+
+Design methods concerning the above-mentioned areas are subject to further study and this Recommendation will serve as a reference when, in the future, Recommendation E.521 is complemented or replaced.
+
+In this Recommendation the proposed methods are evaluated in terms of accuracy, processing time, memory requirements and programming effort. Other criteria may be relevant and added in the future.
+
+The proposed methods are described briefly in clause 6. Clause 7 defines a set of examples of circuit group arrangements with exactly calculated (exact resolution of equations of state) individual means and variances, to which the result of the methods can be compared. This leads to Table 2, where for each method the important criteria are listed. The publications cited in the bibliography section at the end contain detailed information about the mathematical background of each of the methods.
+
+# **6 Proposed methods**
+
+The following methods are considered:
+
+- a) IPP method;
+- b) EC method;
+- c) AWW method;
+- d) EPS method.
+
+## **6.1 IPP method**
+
+IPP method is a Poisson process interrupted by a random switch. The on-/off-duration of the random switch has a negative exponential distribution. Overflow traffic from a circuit group can be accurately approximated by an IPP, since IPP can represent bulk characteristics of overflow traffic. IPP has three parameters, namely, on-period intensity and mean on-/off-period durations. To approximate overflow traffic by an IPP, those three parameters are determined so that some moments of overflow traffic will coincide with those of IPP.
+
+The following two kinds of moment match methods are considered in this Recommendation:
+
+- three-moment match method [1] where IPP parameters are determined so that the first three moments of IPP will coincide with those of overflow traffic;
+- four-moment ratio match method [2] where IPP parameters are determined so that the first moment and the ratios of the 2nd/3rd and 7th/8th binomial moments of IPP will coincide with those of overflow traffic.
+
+To analyse a circuit group where multiple Poisson and overflow traffic streams are simultaneously offered, each overflow stream is approximated by an IPP. The IPP method is well suited to computer calculation. State transition equations of the circuit group with IPP inputs can be solved directly and no introduction of equivalent models is necessary. Characteristics of overflow traffic can be obtained from the solution of state transition equations. The main feature of the IPP method is that the individual means and variances of the overflow traffic can be solved.
+
+## 6.2 EC method
+
+The EC method [3] does not use the traffic-moments but the transitional behaviour of the primary traffic, by introducing a certain function  $\rho(n)$  versus the equivalent capacity ( $n$ ) of the partial overflow traffic, as defined by the recurrent process:
+
+$$\begin{cases} \rho(0) = Em(\alpha) \quad [\text{Erlang loss formula}] \\ \frac{n}{\rho(n)} = (m+n-a) + \alpha \cdot \rho(n-1) \end{cases} \quad (6-1)$$
+
+if  $n$  is a positive integer, and approximated by linear interpolation if not.
+
+A practical approximation, considering the predominant overflow congestion states only, leads to the equations:
+
+$$\frac{n_i}{n} = \frac{a_i \rho_i(n_i) / D_i(n_i + 1)}{\sum_{k=1}^x a_k \rho_k(n_k) / D_k(n_k + 1)} \quad (6-2)$$
+
+with:
+
+$$D_i(n) = 1 + a_i [\rho_i(n) - \rho_i(n-1)] \quad (6-3)$$
+
+defining the equivalent capacity ( $n_i$ ) of the partial overflow traffic labelled  $i$ , and influenced by the mutual dependency between the partial overflow traffic streams.
+
+The mean value of the partial second overflow is:
+
+$$O_i = a_i \pi \rho_i(n_i) \quad (6-4)$$
+
+where  $\pi$  is the time congestion of the overflow group.
+
+The partial GOS (grade of service) equalization is fulfilled if:
+
+$$\rho_i(n_i) = C \quad (6-5)$$
+
+$C$  being a constant to be chosen.
+
+## 6.3 AWW method
+
+The AWW method uses an approximate ERT model based on an improvement of Rapp's approximation. The total overflow traffic is split up in the individual parts by a simple expression, see equations (6-7) and (6-9). To calculate the total overflow traffic, any method can be used. An approximate Erlang formula calculation for which the speed is independent of the size of the calculated circuit group is given in [4].
+
+The following notations are used:
+
+|                      |                                                           |
+|----------------------|-----------------------------------------------------------|
+| $M$                  | mean of total offered traffic                             |
+| $V$                  | variance of total offered traffic                         |
+| $Z$                  | $V/M$                                                     |
+| $B$                  | mean blocking of the studied group                        |
+| $m_i, v_i, z_i, b_i$ | corresponding quantities for an individual traffic stream |
+| $\sim$               | is used for overflow quantities.                          |
+
+### 6.3.1 Blocking of overflow traffic
+
+For overflow calculations, an approximate ERT model is used. By numerical investigations, a considerable improvement has been found to Rapp's classical approximation for the fictitious traffic. The error added by the approximation is small compared to the error of the ERT model. It is known that ERT underestimates low blockings when mixing traffic of diverse peakedness [2]. The formula, which was given in [4] (although with one printing error), is for  $Z > 1$ :
+
+$$A^* \approx V + Z(Z - 1) (2 + \gamma^\beta)$$
+
+where:
+
+$$\gamma = (2.36 Z - 2.17) \log \left\{ 1 + \frac{Z - 1}{M(Z + 1.5)} \right\}$$
+
+and:
+
+$$\beta = Z/(1.5 M + 2 Z - 1.3) \quad (6-6)$$
+
+### 6.3.2 Wallström formula for individual blocking
+
+There has been much interest in finding a simple and accurate formula for the individual blocked traffic  $\tilde{m}_i$ . Already in 1967, Katz [5] proposed a formula of the type:
+
+$$\tilde{m}_i = m_i B(1 - w + w z_i / Z) \quad (6-7)$$
+
+with  $w$  being a suitable expression. Wallström proposed a very simple one but with reasonable results [6] and [2]:
+
+$$w = 1 - B \quad (6-8)$$
+
+One practical problem is, however, that a small peaked substream could have a blocking  $b_i > 1$  with this formula. To avoid such unreasonable results, a modification is used in this case. Let  $z_{\max}$  be the largest individual  $z_i$ . Then the value used is:
+
+$$w = \begin{cases} 1 - B & \text{if } z_{\max} < Z(1 + B) \text{ otherwise} \\ \frac{Z(1 - B)}{B(z_{\max} - Z)} \end{cases} \quad (6-9)$$
+
+### 6.3.3 Handling of overflow variances
+
+Covariances are not separately calculated within the AWW method. Rather, their effect is included in the individual overflow parameters  $\tilde{v}_i$  so that they sum up to the total variance. The quantities  $\tilde{v}_i$  are obtained from the total overflow variance  $\tilde{V}$  by a simple splitting formula:
+
+$$\tilde{v}_i = \tilde{V} v_i / V \quad (6-10)$$
+
+One can prove that Wallström's splitting formula (6-8) and formula (6-10) together with the ERT model satisfies a certain consistency requirement. One will obtain the same values for the individual blocked traffic when calculating a circuit group of  $N_1 + N_2$  circuits as when calculating first the  $N_1$  circuits and then offering the overflow to the  $N_2$  circuits.
+
+Since the individual variances are treated in this manner, they are not comparable with the results reported in Table 1.
+
+## 6.4 EPS method
+
+The EPS method [7] consists in transforming the individual peaked streams into equivalent Poisson streams (using the standard ERT model) and determining the conditions under which the equivalence is valid (peakedness = variance/mean).
+
+The following notations are used:
+
+- $a_i$  Mean of traffic of input stream  $i$
+- $z_i$  Peakedness of traffic of input stream  $i$
+- $a$  Mean of total offered traffic
+- $v$  Variance of total offered traffic
+- $z$  Peakedness of total offered traffic
+- $O$  Mean of total overflow traffic
+- $Z$  Peakedness of total overflow traffic
+- $V$  Variance of total overflow traffic
+- $O_i$  Mean of overflow of traffic stream  $i$
+- $V_i$  Variance of overflow of traffic stream  $i$
+- $Z_i$  Peakedness of overflow of traffic stream  $i$
+- $C_{(i,j)}$  Covariance between the overflow traffic streams  $i$  and  $j$
+
+The conditions for the validity of the EPS method are:
+
+$$z_i \ll a_i \quad (6-11a)$$
+
+$$(z_i - 1) \ll a_i / 3 \quad (6-11b)$$
+
+These conditions are met in today's large traffic networks, where the traffic is of the order of hundreds of erlangs and peakedness is of order unity.
+
+The method yields the following results:
+
+$$O_i = f_i O \quad (6-12a)$$
+
+$$V_i = (f_i)^2 V + f_i (1 - f_i) O \quad (6-12b)$$
+
+where the stream fractions  $f_i$  are:
+
+$$f_i = a_e(i) / \sum a_e(i) \quad (6-12c)$$
+
+$a_e(i)$ , mean of equivalent Poisson traffic of stream  $i$ , is given by:
+
+$$a_e(i) = a_i z_i + 3z_i (z_i - 1) \quad (6-13)$$
+
+The mean total overflow  $O = \sum O_i$  and the corresponding variance  $V$  are:
+
+$$O = a_e B(s + s_e, a_e) \quad (6-14a)$$
+
+$$V = O (1 - O + a_e / (s + s_e + 1 - a_e + O)) \quad (6-14b)$$
+
+where  $a_e$  and  $s_e$  are given by:
+
+$$a_e = v + 3z (z - 1) \quad (6-15a)$$
+
+$$s_e = a_e (a + z) / (a + z - 1) - a - 1 \quad (6-15b)$$
+
+$B$  denotes the Erlang B formula. Peakedness  $Z$  of the total overflow, equal to  $V/O$ , is:
+
+$$Z = I - O + a_e/(s + s_e + I - a_e + O) \quad (6-16)$$
+
+The covariance between overflow streams  $i$  and  $j$  is:
+
+$$C(i, j) = f_i f_j (V - O) \quad (6-17)$$
+
+Similarly,
+
+$$Z_i - 1 = f_i (Z - 1) \quad (6-18)$$
+
+Clearly, as the input peaked streams approach Poisson in character,  $a_e(i) \rightarrow a_i$ , since  $z_i \rightarrow 1$ . As a result,  $f_i = a_i/\sum a_i$ , and the above equations appropriately reduce to those for Poisson input streams [7]. Note also that under the conditions defined by equations (6-11a) and (6-11b), equation (6-12c) reduces to  $f_i \approx a_i z_i / \sum a_i z_i$ .
+
+# 7 Examples and criteria for comparison
+
+The defined methods are tested by calculating the examples given in Table 1.
+
+The calculation model is given in Figure 1.
+
+![Figure 1/E.524 – Calculation model diagram. The diagram shows a hierarchical trunk group structure. At the top, a 'Common trunk group' with capacity N is shown. Above it, four overflow streams are depicted, labeled O0 V0, O1 V1, O2 V2, and O3 V3. These streams are grouped under a total overflow O and V. Below the common trunk group, there are three 'First choice trunk groups' labeled N1, N2, and N3. Arrows indicate traffic flow from input streams A1, A2, and A3 into their respective first choice trunk groups. Overflow from these groups then flows into the common trunk group. A separate input stream A0 is also shown entering the common trunk group directly. The diagram includes various labels for traffic volumes (A, O, V), trunk group capacities (N), and peakedness (Z).](af6be343f0c0a8f155f965dcf337b8af_img.jpg)
+
+Figure 1/E.524 – Calculation model diagram. The diagram shows a hierarchical trunk group structure. At the top, a 'Common trunk group' with capacity N is shown. Above it, four overflow streams are depicted, labeled O0 V0, O1 V1, O2 V2, and O3 V3. These streams are grouped under a total overflow O and V. Below the common trunk group, there are three 'First choice trunk groups' labeled N1, N2, and N3. Arrows indicate traffic flow from input streams A1, A2, and A3 into their respective first choice trunk groups. Overflow from these groups then flows into the common trunk group. A separate input stream A0 is also shown entering the common trunk group directly. The diagram includes various labels for traffic volumes (A, O, V), trunk group capacities (N), and peakedness (Z).
+
+$A_i$  Offered Poisson traffic volume  
+ $N_i$  Number of first choice trunk group  
+ $N$  Number of common trunk group  
+ $O_i$  Mean of individual overflow traffic from common trunk group  
+ $V_i$  Variance of individual overflow traffic from common trunk group  
+ $O$  Mean of total overflow traffic from common trunk group  
+ $V$  Variance of total overflow traffic from common trunk group
+
+**Figure 1/E.524 – Calculation model**
+
+For comparison, the following criteria are established:
+
+i) *Overflow traffic error*
+
+- *accuracy of the individual overflow traffic mean and variance*
+  - *Mean error*
+
+$$\varepsilon_O^I = \frac{\sum_{\text{all examples } i=1} \sum_{i=1}^M \delta_O^i}{\{\text{number of streams}\} \{\text{number of examples}\}}$$
+
+$$\varepsilon_V^I = \frac{\sum_{\text{all examples } i=1} \sum_{i=1}^M \delta_V^i}{\{\text{number of streams}\} \{\text{number of examples}\}}$$
+
+- *Standard deviation of error*
+
+$$sd_O^I = \frac{\left\{ \sum_{\text{all examples } i=1} \sum_{i=1}^M (\delta_O^i - \varepsilon_O^I)^2 \right\}^{1/2}}{\{\text{number of streams}\} \{\text{number of examples}\}}$$
+
+$$sd_V^I = \frac{\left\{ \sum_{\text{all examples } i=1} \sum_{i=1}^M (\delta_V^i - \varepsilon_V^I)^2 \right\}^{1/2}}{\{\text{number of streams}\} \{\text{number of examples}\}}$$
+
+where:
+
+$$\delta_O^i = (O_i - \bar{O}_i) / \bar{O}_i$$
+
+$$\delta_V^i = (V_i - \bar{V}_i) / \bar{V}_i$$
+
+$O_i, V_i$  Calculated individual mean and variance of approximate method.
+
+$\bar{O}_i, \bar{V}_i$  Exactly calculated individual mean and variance.
+
+$M$  Number of input streams to common trunk group.
+
+- *accuracy of the total overflow traffic mean and variance*
+  - *Mean error*
+
+$$\varepsilon_O^T = \frac{\sum_{\text{all examples}} \delta_O}{\{\text{number of examples}\}}$$
+
+$$\varepsilon_V^T = \frac{\sum_{\text{all examples}} \delta_V}{\{\text{number of examples}\}}$$
+
+- *Standard deviation of error*
+
+$$sd_O^T = \frac{\left\{ \sum_{\substack{\text{all} \\ \text{examples}}} (\delta_O - \varepsilon_O^T)^2 \right\}^{1/2}}{\{\text{number of examples}\}}$$
+
+$$sd_V^T = \frac{\left\{ \sum_{\substack{\text{all} \\ \text{examples}}} (\delta_V - \varepsilon_V^T)^2 \right\}^{1/2}}{\{\text{number of examples}\}}$$
+
+where:
+
+$$\delta_O = (O - \bar{O}) / \bar{O}$$
+
+$$\delta_V = (V - \bar{V}) / \bar{V}$$
+
+$O, V$  Calculated total mean and variance of approximate method.
+
+$\bar{O}, \bar{V}$  Exactly calculated total mean and variance.
+
+### ii) *Computational effort*
+
+- *Relative processor time*
+
+$$C = \frac{\{\text{Total central processing unit (CPU) time for calculating all examples by using the approximate method}\}}{\{\text{Total CPU time for calculating all examples by Erlang formula}\}}$$
+
+- *Memory requirements*
+
+$$M = \frac{\text{The size of memory required for the execution of approximate method}}{\text{The size of memory required for execution of Erlang formula}}$$
+
+- *Program size*
+
+$$S = \frac{\text{Source program size for approximate method}}{\text{Source program size for Erlang formula}}$$
+
+NOTE 1 –  $C$ ,  $M$  and  $S$ , for a specific approximate method, should be based on the same processor, language and supporting algorithms.
+
+NOTE 2 – Depending on the type of approximate method (direct calculating or recursive) different trade-offs between  $C$ ,  $M$  and  $S$  may be reached, e.g. more memory versus less time, small program versus more time, etc.
+
+**Table 1a/E.524 – Exactly calculated mean and variance of individual overflow traffic – Three first choice groups**
+
+| Case | $A_1$  | $A_2$  | $A_3$  | $A_0$ | $O_0$    | $O_1$   | $O_2$   | $O_3$   | $O$    |
+|------|--------|--------|--------|-------|----------|---------|---------|---------|--------|
+|      | $N_1$  | $N_2$  | $N_3$  | $N$   | $V_0$    | $V_1$   | $V_2$   | $V_3$   | $V$    |
+| 1    | 7.036  | 26.688 | 64.169 | –     | –        | 0.4337  | 0.7490  | 1.091   | 2.274  |
+|      | 5      | 28     | 70     | 11    | –        | 0.7656  | 2.111   | 4.441   | 10.51  |
+| 2    | 7.036  | 26.688 | 64.169 | –     | –        | 0.1449  | 0.2758  | 0.4944  | 0.9150 |
+|      | 5      | 28     | 70     | 16    | –        | 0.2436  | 0.7328  | 1.911   | 4.293  |
+| 3    | 7.036  | 26.688 | 64.169 | –     | –        | 0.01369 | 0.02846 | 0.06628 | 0.1084 |
+|      | 5      | 28     | 70     | 25    | –        | 0.02041 | 0.06461 | 0.2205  | 0.4464 |
+| 4    | 7.036  | 10.176 | 13.250 | –     | –        | 0.7459  | 1.262   | 1.785   | 3.792  |
+|      | 5      | 6      | 7      | 14    | –        | 1.193   | 2.292   | 3.625   | 11.28  |
+| 5    | 7.036  | 10.176 | 13.250 | –     | –        | 0.2888  | 0.4857  | 0.6832  | 1.458  |
+|      | 5      | 6      | 7      | 19    | –        | 0.4636  | 0.9089  | 1.460   | 4.754  |
+| 6    | 7.036  | 10.176 | 13.250 | –     | –        | 0.03570 | 0.05915 | 0.08237 | 0.1772 |
+|      | 5      | 6      | 7      | 26    | –        | 0.05358 | 0.1026  | 0.1621  | 0.5249 |
+| 7    | 7.036  | 32.395 | 77.617 | –     | –        | 0.4516  | 1.176   | 2.344   | 3.972  |
+|      | 5      | 31     | 77     | 16    | –        | 0.7434  | 3.466   | 10.39   | 21.41  |
+| 8    | 7.036  | 32.395 | 77.617 | –     | –        | 0.1538  | 0.4294  | 0.9739  | 1.557  |
+|      | 5      | 31     | 77     | 23    | –        | 0.2427  | 1.200   | 4.219   | 8.558  |
+| 9    | 7.036  | 32.395 | 77.617 | –     | –        | 0.01303 | 0.03984 | 0.1006  | 0.1535 |
+|      | 5      | 31     | 77     | 35    | –        | 0.01841 | 0.09378 | 0.3690  | 0.7124 |
+| 10   | 64.169 | 32.395 | 13.250 | –     | –        | 1.157   | 1.455   | 1.320   | 3.933  |
+|      | 70     | 31     | 7      | 15    | –        | 4.442   | 4.256   | 2.849   | 18.28  |
+| 11   | 64.169 | 32.395 | 13.250 | –     | –        | 0.5564  | 0.5849  | 0.4749  | 1.616  |
+|      | 70     | 31     | 7      | 21    | –        | 2.026   | 1.675   | 1.023   | 8.008  |
+| 12   | 64.169 | 32.395 | 13.250 | –     | –        | 0.06907 | 0.05265 | 0.03848 | 0.1602 |
+|      | 70     | 31     | 7      | 32    | –        | 0.2167  | 0.1295  | 0.07165 | 0.7075 |
+| 13   | 7.036  | 26.688 | 64.169 | 3.000 | 0.4064   | 0.5038  | 0.8274  | 1.160   | 2.897  |
+|      | 5      | 28     | 70     | 13    | 0.5578   | 0.8566  | 2.243   | 4.574   | 13.16  |
+| 14   | 7.036  | 26.688 | 64.169 | 3.000 | 0.1460   | 0.1840  | 0.3384  | 0.5729  | 1.241  |
+|      | 5      | 28     | 70     | 18    | 0.1992   | 0.3043  | 0.8779  | 2.163   | 5.893  |
+| 15   | 7.036  | 26.688 | 64.169 | 3.000 | 0.01170  | 0.01506 | 0.03086 | 0.07035 | 0.1280 |
+|      | 5      | 28     | 70     | 28    | 0.01472  | 0.02218 | 0.06861 | 0.2287  | 0.5374 |
+| 16   | 7.036  | 32.395 | 77.617 | 1.000 | 0.1253   | 0.4451  | 1.156   | 2.304   | 4.031  |
+|      | 5      | 31     | 77     | 17    | 0.1392   | 0.7266  | 3.366   | 10.10   | 21.77  |
+| 17   | 7.036  | 32.395 | 77.617 | 1.000 | 0.04250  | 0.1536  | 0.4275  | 0.9674  | 1.591  |
+|      | 5      | 31     | 77     | 24    | 0.04696  | 0.2409  | 1.183   | 4.148   | 8.775  |
+| 18   | 7.036  | 32.395 | 77.617 | 1.000 | 0.004542 | 0.01687 | 0.05106 | 0.1282  | 0.2006 |
+|      | 5      | 31     | 77     | 35    | 0.004891 | 0.02398 | 0.1214  | 0.4751  | 0.9548 |
+| 19   | 64.169 | 32.395 | 13.250 | 9.000 | 1.761    | 1.251   | 1.654   | 1.630   | 6.295  |
+|      | 70     | 31     | 7      | 21    | 3.052    | 4.517   | 4.406   | 3.103   | 27.73  |
+| 20   | 64.169 | 32.395 | 13.250 | 9.000 | 0.6761   | 0.6501  | 0.7389  | 0.6427  | 2.708  |
+|      | 70     | 31     | 7      | 28    | 1.253    | 2.225   | 1.956   | 1.279   | 13.61  |
+| 21   | 64.169 | 32.395 | 13.250 | 9.000 | 0.06219  | 0.09577 | 0.07978 | 0.06069 | 0.2984 |
+|      | 70     | 31     | 7      | 40    | 0.1054   | 0.2884  | 0.1887  | 0.1099  | 1.409  |
+
+**Table 1b/E.524 – Exactly calculated mean and variance of individual overflow traffic – Two first choice groups**
+
+| Case | $A_1$  | $A_2$  | $A_3$ | $A_0$ | $O_0$ | $O_1$   | $O_2$   | $O_3$ | $O$     |
+|------|--------|--------|-------|-------|-------|---------|---------|-------|---------|
+|      | $N_1$  | $N_2$  | $N_3$ | $N$   | $V_0$ | $V_1$   | $V_2$   | $V_3$ | $V$     |
+| 22   | 8.200  | 30.000 | –     | –     | –     | 0.6153  | 1.139   | –     | 1.755   |
+|      | 5      | 30     | –     | 10    | –     | 1.179   | 3.473   | –     | 6.159   |
+| 23   | 8.200  | 30.000 | –     | –     | –     | 1.807   | 2.465   | –     | 4.272   |
+|      | 5      | 30     | –     | 5     | –     | 3.263   | 7.431   | –     | 13.00   |
+| 24   | 8.200  | 30.000 | –     | –     | –     | 0.01866 | 0.04814 | –     | 0.06680 |
+|      | 5      | 30     | –     | 21    | –     | 0.03026 | 0.1233  | –     | 0.1993  |
+| 25   | 8.200  | 30.000 | –     | –     | –     | 0.2111  | 0.4629  | –     | 0.6740  |
+|      | 5      | 30     | –     | 14    | –     | 0.3902  | 1.372   | –     | 2.355   |
+| 26   | 8.200  | 14.300 | –     | –     | –     | 0.04699 | 0.09279 | –     | 0.1398  |
+|      | 5      | 7      | –     | 22    | –     | 0.07700 | 0.1980  | –     | 0.3724  |
+| 27   | 8.200  | 14.300 | –     | –     | –     | 0.3744  | 0.7547  | –     | 1.129   |
+|      | 5      | 7      | –     | 16    | –     | 0.6603  | 1.763   | –     | 3.322   |
+| 28   | 8.200  | 14.300 | –     | –     | –     | 0.9282  | 1.892   | –     | 2.820   |
+|      | 5      | 7      | –     | 12    | –     | 1.614   | 4.212   | –     | 7.774   |
+| 29   | 8.200  | 14.300 | –     | –     | –     | 2.002   | 4.095   | –     | 6.098   |
+|      | 5      | 7      | –     | 7     | –     | 3.272   | 7.806   | –     | 13.64   |
+| 30   | 8.200  | 42.000 | –     | –     | –     | 0.02324 | 0.09886 | –     | 0.1221  |
+|      | 5      | 37     | –     | 27    | –     | 0.03602 | 0.3019  | –     | 0.4197  |
+| 31   | 8.200  | 42.000 | –     | –     | –     | 0.2136  | 0.8353  | –     | 1.049   |
+|      | 5      | 37     | –     | 19    | –     | 0.3682  | 2.945   | –     | 4.204   |
+| 32   | 8.200  | 42.000 | –     | –     | –     | 1.499   | 4.437   | –     | 5.935   |
+|      | 5      | 37     | –     | 8     | –     | 2.616   | 14.60   | –     | 21.00   |
+| 33   | 8.200  | 42.000 | –     | –     | –     | 0.6940  | 2.416   | –     | 3.110   |
+|      | 5      | 37     | –     | 13    | –     | 1.237   | 8.493   | –     | 12.30   |
+| 34   | 30.000 | 14.300 | –     | –     | –     | 0.06570 | 0.05450 | –     | 0.1202  |
+|      | 30     | 7      | –     | 25    | –     | 0.1628  | 0.1116  | –     | 0.3922  |
+| 35   | 30.000 | 14.300 | –     | –     | –     | 0.4669  | 0.4662  | –     | 0.9331  |
+|      | 30     | 7      | –     | 18    | –     | 1.300   | 1.088   | –     | 3.461   |
+| 36   | 30.000 | 14.300 | –     | –     | –     | 1.374   | 1.739   | –     | 3.113   |
+|      | 30     | 7      | –     | 12    | –     | 3.932   | 4.001   | –     | 10.91   |
+| 37   | 30.000 | 14.300 | –     | –     | –     | 2.425   | 3.806   | –     | 6.231   |
+|      | 30     | 7      | –     | 7     | –     | 6.994   | 7.628   | –     | 18.16   |
+| 38   | 8.200  | 67.900 | –     | –     | –     | 0.01656 | 0.1007  | –     | 0.1173  |
+|      | 5      | 65     | –     | 30    | –     | 0.02497 | 0.3667  | –     | 0.4658  |
+| 39   | 8.200  | 67.900 | –     | –     | –     | 0.1835  | 0.9716  | –     | 1.155   |
+|      | 5      | 65     | –     | 20    | –     | 0.3132  | 4.189   | –     | 5.488   |
+| 40   | 8.200  | 67.900 | –     | –     | –     | 0.5393  | 2.449   | –     | 2.986   |
+|      | 5      | 65     | –     | 14    | –     | 0.9685  | 10.73   | –     | 14.35   |
+| 41   | 8.200  | 67.900 | –     | –     | –     | 1.361   | 4.707   | –     | 6.068   |
+|      | 5      | 65     | –     | 8     | –     | 2.441   | 19.71   | –     | 26.55   |
+| 42   | 51.500 | 14.300 | –     | –     | –     | 0.07517 | 0.04089 | –     | 0.1161  |
+|      | 54     | 7      | –     | 27    | –     | 0.2290  | 0.08146 | –     | 0.4339  |
+| 43   | 51.500 | 14.300 | –     | –     | –     | 0.6402  | 0.4689  | –     | 1.109   |
+|      | 54     | 7      | –     | 18    | –     | 2.248   | 1.101   | –     | 4.799   |
+
+**Table 1c/E.524 – Exactly calculated mean and variance of individual overflow traffic – One first choice group**
+
+| Case | $A_1$  | $A_2$  | $A_3$ | $A_0$ | $O_0$   | $O_1$   | $O_2$ | $O_3$ | $O$     |
+|------|--------|--------|-------|-------|---------|---------|-------|-------|---------|
+|      | $N_1$  | $N_2$  | $N_3$ | $N$   | $V_0$   | $V_1$   | $V_2$ | $V_3$ | $V$     |
+| 44   | 51.500 | 14.300 | –     | –     | –       | 1.403   | 1.362 | –     | 2.765   |
+|      | 54     | 7      | –     | 13    | –       | 5.079   | 3.224 | –     | 11.50   |
+| 45   | 51.500 | 14.300 | –     | –     | –       | 2.586   | 3.675 | –     | 6.261   |
+|      | 54     | 7      | –     | 7     | –       | 9.612   | 7.513 | –     | 21.11   |
+| 46   | 8.200  | –      | –     | 4.000 | 0.03309 | 0.04990 | –     | –     | 0.08299 |
+|      | 5      | –      | –     | 16    | 0.04785 | 0.08712 | –     | –     | 0.1789  |
+| 47   | 8.200  | –      | –     | 4.000 | 0.3494  | 0.4859  | –     | –     | 0.8354  |
+|      | 5      | –      | –     | 11    | 0.5382  | 0.9155  | –     | –     | 1.975   |
+| 48   | 8.200  | –      | –     | 4.000 | 0.9011  | 1.169   | –     | –     | 2.070   |
+|      | 5      | –      | –     | 8     | 1.327   | 2.120   | –     | –     | 4.554   |
+| 49   | 8.200  | –      | –     | 4.000 | 1.802   | 2.142   | –     | –     | 3.944   |
+|      | 5      | –      | –     | 5     | 2.369   | 3.588   | –     | –     | 7.333   |
+| 50   | 30.000 | –      | –     | 4.000 | 0.01660 | 0.05973 | –     | –     | 0.07633 |
+|      | 30     | –      | –     | 20    | 0.02296 | 0.1558  | –     | –     | 0.2228  |
+| 51   | 30.000 | –      | –     | 4.000 | 0.1991  | 0.5806  | –     | –     | 0.7796  |
+|      | 30     | –      | –     | 13    | 0.3062  | 1.743   | –     | –     | 2.656   |
+| 52   | 30.000 | –      | –     | 4.000 | 0.5988  | 1.400   | –     | –     | 1.999   |
+|      | 30     | –      | –     | 9     | 0.9338  | 4.255   | –     | –     | 6.730   |
+| 53   | 30.000 | –      | –     | 4.000 | 1.560   | 2.558   | –     | –     | 4.118   |
+|      | 30     | –      | –     | 5     | 2.199   | 7.620   | –     | –     | 12.01   |
+| 54   | 51.500 | –      | –     | 4.000 | 0.01445 | 0.07537 | –     | –     | 0.08982 |
+|      | 54     | –      | –     | 22    | 0.01966 | 0.2413  | –     | –     | 0.3131  |
+| 55   | 51.500 | –      | –     | 4.000 | 0.1208  | 0.5143  | –     | –     | 0.6351  |
+|      | 54     | –      | –     | 15    | 0.1819  | 1.893   | –     | –     | 2.575   |
+| 56   | 51.500 | –      | –     | 4.000 | 0.4286  | 1.383   | –     | –     | 1.812   |
+|      | 54     | –      | –     | 10    | 0.6788  | 5.300   | –     | –     | 7.549   |
+| 57   | 51.500 | –      | –     | 4.000 | 1.145   | 2.429   | –     | –     | 3.574   |
+|      | 54     | –      | –     | 6     | 1.726   | 9.299   | –     | –     | 13.55   |
+
+# 8 Summary of results
+
+The available methods and the performance measures with respect to the criteria are listed in Table 2.
+
+**Table 2/E.524 –Comparison of different approximation methods**
+
+| Functions      | Comparison           |                     |                    |
+|----------------|----------------------|---------------------|--------------------|
+|                | Computational effort |                     |                    |
+| Method         | Processor time       | Memory requirements | Programming effort |
+| IPP method     |                      |                     |                    |
+| 3-moment match | 400                  | 5                   | 50                 |
+| 4-moment ratio | 1000                 | 5                   | 50                 |
+| EC method      | 40                   | 2                   | 3                  |
+| AWW method     | 3                    | 1.6                 | 3                  |
+| EPS method     | 3                    | 2                   | 3                  |
+
+# 9 History
+
+Recommendation E.524 – first issued in 1988; revised in 1992; second revision in 1999.
+
+# Bibliography
+
+- [1] MATSUMOTO (J.), WATANABE (Y.): Analysis of individual traffic characteristics for queueing systems with multiple Poisson and overflow inputs, *Proc. 10th ITC*, paper 5.3.1, Montreal 1983.
+- [2] RENEBY (L.): On individual and overall losses in overflow systems, *Proc. 10th ITC*, paper 5.3.5, Montreal 1983.
+- [3] LE GALL (P.): Overflow traffic combination and cluster engineering, *Proc. 11th ITC*, paper 2.2B-1, Kyoto 1985.
+- [4] LINDBERG (P.), NIVERT (K.), SAGERHOLM (B.): Economy and service aspects of different designs of alternate routing networks, *Proc. 11th ITC*, Kyoto 1985.
+- [5] KATZ (S.): Statistical performance analysis of a switched communications network, *Proc. 5th ITC*, New York 1967.
+- [6] LINDBERGER (K.): Simple approximations of overflow system quantities for additional demands in the optimization, *Proc. 10th ITC*, Montreal 1983.
+- [7] BHANDARI (R.): A model for stream overflows in circuit-switched communication networks, *IEICE Transactions on Communications: Special Issue on Telecommunications Network Planning and Design*, Vol. E80-B, No. 2, pp. 324-331 (1997).
+
+# ITU-T RECOMMENDATIONS SERIES
+
+|                 |                                                                                                                                |
+|-----------------|--------------------------------------------------------------------------------------------------------------------------------|
+| Series A        | Organization of the work of the ITU-T                                                                                          |
+| Series B        | Means of expression: definitions, symbols, classification                                                                      |
+| Series C        | General telecommunication statistics                                                                                           |
+| Series D        | General tariff principles                                                                                                      |
+| <b>Series E</b> | <b>Overall network operation, telephone service, service operation and human factors</b>                                       |
+| Series F        | Non-telephone telecommunication services                                                                                       |
+| Series G        | Transmission systems and media, digital systems and networks                                                                   |
+| Series H        | Audiovisual and multimedia systems                                                                                             |
+| Series I        | Integrated services digital network                                                                                            |
+| Series J        | Transmission of television, sound programme and other multimedia signals                                                       |
+| Series K        | Protection against interference                                                                                                |
+| Series L        | Construction, installation and protection of cables and other elements of outside plant                                        |
+| Series M        | TMN and network maintenance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits |
+| Series N        | Maintenance: international sound programme and television transmission circuits                                                |
+| Series O        | Specifications of measuring equipment                                                                                          |
+| Series P        | Telephone transmission quality, telephone installations, local line networks                                                   |
+| Series Q        | Switching and signalling                                                                                                       |
+| Series R        | Telegraph transmission                                                                                                         |
+| Series S        | Telegraph services terminal equipment                                                                                          |
+| Series T        | Terminals for telematic services                                                                                               |
+| Series U        | Telegraph switching                                                                                                            |
+| Series V        | Data communication over the telephone network                                                                                  |
+| Series X        | Data networks and open system communications                                                                                   |
+| Series Y        | Global information infrastructure and Internet protocol aspects                                                                |
+| Series Z        | Languages and general software aspects for telecommunication systems                                                           |

marked/E/T-REC-E.527-200003-I_PDF-E/raw.md

@@ -0,0 +1,559 @@
+
+
+![ITU logo: A globe with a lightning bolt and the letters ITU.](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg)
+
+ITU logo: A globe with a lightning bolt and the letters ITU.
+
+INTERNATIONAL TELECOMMUNICATION UNION
+
+**ITU-T**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+**E.527**
+
+(03/2000)
+
+SERIES E: OVERALL NETWORK OPERATION,  
+TELEPHONE SERVICE, SERVICE OPERATION AND  
+HUMAN FACTORS
+
+Quality of service, network management and traffic  
+engineering – Traffic engineering – Determination of the  
+number of circuits in automatic and semi-automatic  
+operation
+
+---
+
+**Dimensioning at a circuit group with multi-slot  
+bearer services and overflow traffic**
+
+ITU-T Recommendation E.527
+
+(Formerly CCITT Recommendation)
+
+---
+
+# ITU-T E-SERIES RECOMMENDATIONS **OVERALL NETWORK OPERATION, TELEPHONE SERVICE, SERVICE OPERATION AND HUMAN FACTORS**
+
+|                                                                                                   |                    |
+|---------------------------------------------------------------------------------------------------|--------------------|
+| <b>OPERATION, NUMBERING, ROUTING AND MOBILE SERVICES</b>                                          |                    |
+| INTERNATIONAL OPERATION                                                                           |                    |
+| Definitions                                                                                       | E.100–E.103        |
+| General provisions concerning Administrations                                                     | E.104–E.119        |
+| General provisions concerning users                                                               | E.120–E.139        |
+| Operation of international telephone services                                                     | E.140–E.159        |
+| Numbering plan of the international telephone service                                             | E.160–E.169        |
+| International routing plan                                                                        | E.170–E.179        |
+| Tones in national signalling systems                                                              | E.180–E.189        |
+| Numbering plan of the international telephone service                                             | E.190–E.199        |
+| Maritime mobile service and public land mobile service                                            | E.200–E.229        |
+| OPERATIONAL PROVISIONS RELATING TO CHARGING AND ACCOUNTING IN THE INTERNATIONAL TELEPHONE SERVICE |                    |
+| Charging in the international telephone service                                                   | E.230–E.249        |
+| Measuring and recording call durations for accounting purposes                                    | E.260–E.269        |
+| UTILIZATION OF THE INTERNATIONAL TELEPHONE NETWORK FOR NON-TELEPHONY APPLICATIONS                 |                    |
+| General                                                                                           | E.300–E.319        |
+| Phototelegraphy                                                                                   | E.320–E.329        |
+| ISDN PROVISIONS CONCERNING USERS                                                                  |                    |
+| International routing plan                                                                        | E.350–E.399        |
+| <b>QUALITY OF SERVICE, NETWORK MANAGEMENT AND TRAFFIC ENGINEERING</b>                             |                    |
+| NETWORK MANAGEMENT                                                                                |                    |
+| International service statistics                                                                  | E.400–E.409        |
+| International network management                                                                  | E.410–E.419        |
+| Checking the quality of the international telephone service                                       | E.420–E.489        |
+| TRAFFIC ENGINEERING                                                                               |                    |
+| Measurement and recording of traffic                                                              | E.490–E.505        |
+| Forecasting of traffic                                                                            | E.506–E.509        |
+| Determination of the number of circuits in manual operation                                       | E.510–E.519        |
+| <b>Determination of the number of circuits in automatic and semi-automatic operation</b>          | <b>E.520–E.539</b> |
+| Grade of service                                                                                  | E.540–E.599        |
+| Definitions                                                                                       | E.600–E.699        |
+| ISDN traffic engineering                                                                          | E.700–E.749        |
+| Mobile network traffic engineering                                                                | E.750–E.799        |
+| QUALITY OF TELECOMMUNICATION SERVICES: CONCEPTS, MODELS, OBJECTIVES AND DEPENDABILITY PLANNING    |                    |
+| Terms and definitions related to the quality of telecommunication services                        | E.800–E.809        |
+| Models for telecommunication services                                                             | E.810–E.844        |
+| Objectives for quality of service and related concepts of telecommunication services              | E.845–E.859        |
+| Use of quality of service objectives for planning of telecommunication networks                   | E.860–E.879        |
+| Field data collection and evaluation on the performance of equipment, networks and services       | E.880–E.899        |
+
+For further details, please refer to ITU-T List of Recommendations.
+
+# **DIMENSIONING AT A CIRCUIT GROUP WITH MULTI-SLOT BEARER SERVICES AND OVERFLOW TRAFFIC**
+
+## **Summary**
+
+This Recommendation deals with dimensioning methods for a set of circuit groups handling multi-slot bearer services which consist of first-choice groups and an overflow group to which overflow traffic from the first-choice groups are offered. For this purpose, this Recommendation provides example methods for calculating peakedness of the overflow traffic and example methods for calculating individual call blocking probabilities of the overflow group.
+
+### **Source**
+
+ITU-T Recommendation E.527 was revised by ITU-T Study Group 2 (1997-2000) and was approved under the WTSC Resolution No. 1 procedure on 13 March 2000.
+
+## FOREWORD
+
+ITU (International Telecommunication Union) is the United Nations Specialized Agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the ITU. The ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis.
+
+The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics.
+
+The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Resolution No. 1.
+
+In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC.
+
+### NOTE
+
+In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+## INTELLECTUAL PROPERTY RIGHTS
+
+The ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. The ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process.
+
+As of the date of approval of this Recommendation, the ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database.
+
+© ITU 2000
+
+All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU.
+
+## CONTENTS
+
+|       |                                                                                                           | Page |
+|-------|-----------------------------------------------------------------------------------------------------------|------|
+| 1     | Scope of this Recommendation .....                                                                        | 1    |
+| 2     | References.....                                                                                           | 1    |
+| 3     | Terms and definitions .....                                                                               | 1    |
+| 4     | Introduction.....                                                                                         | 1    |
+| 5     | Modelling for dimensioning of circuit groups .....                                                        | 2    |
+| 5.1   | Modelling of offered traffic .....                                                                        | 2    |
+| 5.2   | Categories of circuit groups .....                                                                        | 2    |
+| 5.3   | GOS objectives .....                                                                                      | 2    |
+| 6     | Characterization of overflow traffic from a first-choice group.....                                       | 3    |
+| 6.1   | Calculating traffic intensity of individual overflow.....                                                 | 3    |
+| 6.2   | Calculating peakedness of individual overflows .....                                                      | 3    |
+| 7     | Dimensioning methods for an overflow group .....                                                          | 3    |
+| 7.1   | Principles .....                                                                                          | 3    |
+| 7.2   | Calculating individual call blocking probabilities .....                                                  | 3    |
+| 8     | History.....                                                                                              | 4    |
+| 9     | Bibliography.....                                                                                         | 4    |
+|       | Annex A – Example methods for calculating overflow variances from a first-choice group..                  | 4    |
+| A.1   | Assumptions and notations .....                                                                           | 4    |
+| A.2   | Variance calculation methods .....                                                                        | 5    |
+| A.2.1 | Exact solution method .....                                                                               | 5    |
+| A.2.2 | Approximation method.....                                                                                 | 6    |
+|       | Annex B – Example method for calculating individual call blocking probabilities of an overflow group..... | 7    |
+| B.1   | Reduced network method .....                                                                              | 7    |
+| B.2   | Notations .....                                                                                           | 7    |
+| B.3   | Determination of equivalent capacity $n_i$ .....                                                          | 8    |
+| B.4   | Time congestion $\Pi$ .....                                                                               | 8    |
+| B.5   | Blocking probability $B_i$ .....                                                                          | 9    |
+| B.6   | The second overflow.....                                                                                  | 9    |
+| B.7   | Field of application .....                                                                                | 9    |
+| B.8   | Processing time and programming effort.....                                                               | 9    |
+
+
+
+# **DIMENSIONING AT A CIRCUIT GROUP WITH MULTI-SLOT BEARER SERVICES AND OVERFLOW TRAFFIC**
+
+*(revised in 2000)*
+
+## **1 Scope of this Recommendation**
+
+This Recommendation deals with dimensioning methods for a set of circuit groups handling multi-slot bearer services which consist of first-choice groups and an overflow group to which overflow traffic from the first-choice groups are offered. For this purpose, this Recommendation provides example methods for calculating peakedness of the overflow traffic and example methods for calculating individual call blocking probabilities of the overflow group.
+
+## **2 References**
+
+The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; all users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published.
+
+- ITU-T Recommendation E.524 (1999), *Overflow approximations for non-random inputs*.
+- ITU-T Recommendation E.526 (1993), *Dimensioning a circuit group with multi-slot bearer services and no overflow inputs*.
+- CCITT Recommendation E.731 (1992), *Methods for dimensioning resources operating in circuit switched mode*.
+- ITU-T Recommendation E.737 (1997), *Dimensioning methods for B-ISDN*.
+
+## **3 Terms and definitions**
+
+Recommendation E.600 provides general terminology in traffic engineering used in this Recommendation.
+
+## **4 Introduction**
+
+This Recommendation presents methods for dimensioning a circuit group with multi-slot bearer services and overflow traffic. Methods for dimensioning a circuit group with multi-slot bearer services and no overflow traffic are presented in Recommendation E.526. Thus this Recommendation complements Recommendation E.526.
+
+This Recommendation treats an overflow group to which multiple overflow traffic streams from the first-choice groups. It is assumed that both overflow groups and first-choice groups are operated with full availability (see Recommendation E.731).
+
+Individual traffic streams will be expressed, on the one hand, in calls as in Recommendation E.524, and on the other in busy circuits as in Recommendation E.526.
+
+This Recommendation is also related to Recommendations E.731 and E.737 in that the dimensioning methods presented in these Recommendations are based on the technique of multi-slot traffic modelling of a circuit-switched network which handles a mixed traffic with different bandwidth requirements.
+
+## 5 Modelling for dimensioning of circuit groups
+
+### 5.1 Modelling of offered traffic
+
+For traffic engineering purpose, multi-slot bearer traffic is often characterized by the following parameters:
+
+- traffic stream identification, denoted by  $i$ ;
+- call arrival rate for traffic stream  $i$ , denoted by  $\lambda_i$ ;
+- mean holding time for traffic stream  $i$ , denoted by  $1/\mu_i$ ;
+- number of circuits occupied by a call for traffic stream  $i$ , denoted by  $d_i$ ;
+- traffic intensity measured in number of calls for traffic stream  $i$ , denoted by  $A_i$  ( $A_i = \lambda_i/\mu_i$ );
+- peakedness factor for traffic stream  $i$ , denoted by  $Z_i$ .
+
+### 5.2 Categories of circuit groups
+
+In this Recommendation, the following two categories of circuit groups with multi-slot bearer services are considered.
+
+#### a) *First-choice group*
+
+A first-choice group is a circuit group to which fresh traffic is offered. The fresh traffic is modelled by a Poisson arrival process and thus its peakedness factor is one. The first-choice group with multi-slot bearer services may handle various traffic streams of calls which hold different numbers of time slots when accepted.
+
+Following the definitions and notations in Recommendation E.526, the size of the first-choice group is represented by the number of circuits in the group.
+
+#### b) *Overflow group*
+
+An overflow group is a circuit group to which overflow traffic from the first-choice groups is offered. It may handle fresh traffic which is offered to it as well.
+
+The size of the overflow group is also represented by the number of circuits in the group.
+
+### 5.3 GOS objectives
+
+For the purpose of dimensioning circuit groups with multi-slot bearer services, call blocking probabilities are considered as an important GOS parameter. Thus, the objectives of link call blocking probabilities and/or end-to-end call blocking probabilities are often used in a dimensioning process of a network which consists of circuit groups. Since end-to-end call blocking probabilities are often calculated from the link call blocking probabilities and routing patterns as described in Recommendation E.737, it is important to evaluate individual call blocking probabilities at a circuit group. This Recommendation, therefore, focuses on methods for calculating individual call blocking probabilities at the circuit group level.
+
+# 6 Characterization of overflow traffic from a first-choice group
+
+### 6.1 Calculating traffic intensity of individual overflow
+
+Once individual call blocking probabilities are obtained at a first-choice group, the traffic intensities  $O_i$  of individual overflows can be evaluated as follows:
+
+$$O_i = A_i B_i \quad (6-1)$$
+
+where  $B_i$  denotes the call blocking probability of the  $i$ -th traffic stream at the first-choice group. Example methods for calculating the call blocking probability  $B_i$  are given in Recommendations E.526, E.731 and E.737.
+
+### 6.2 Calculating peakedness of individual overflows
+
+To characterize the overflow traffic for the purpose of dimensioning the overflow group, the peakednesses of the individual overflow traffic offered to the overflow group are often used. The peakedness  $Z_i$  is defined as:
+
+$$Z_i = V_i / O_i \quad (6-2)$$
+
+where  $V_i$  denotes the variance of the overflow traffic.
+
+Example methods for calculating the variances and thus peakednesses of individual overflow are given in Annex A.
+
+## 7 Dimensioning methods for an overflow group
+
+### 7.1 Principles
+
+The basic problem of dimensioning an overflow group is to determine the size of the group and the parameter values of service protection schemes such as a trunk reservation (see Recommendations E.731 and E.737), if applied, under the constraint of call blocking objectives in an economical way for a given offered traffic condition. Note that the overflow traffic streams offered to the group may be characterized by its traffic intensity and peakedness. If the overflow traffic is directly offered from a first-choice group, its intensity and peakedness may be calculated by using the methods given in clause 6.
+
+To dimension the overflow group, in principle, the following iterative procedure is used:
+
+Step 1: Start with an initial set of values of the group size and, if applied, of parameters of service protection schemes.
+
+Step 2: Evaluate individual blocking probabilities of the calls at the group for the current set of group size and parameter values to check if the blocking objectives are satisfied.
+
+Step 3: If the objectives are all met and a certain optimization criterion is met as well, end the procedure. Otherwise, modify the group size and/or the parameter values of service protection schemes and return to Step 2.
+
+As seen in Step 2 above, it is needed to calculate all the call blocking probabilities for the group.
+
+### 7.2 Calculating individual call blocking probabilities
+
+Several methods are available for calculating approximate individual call blocking probabilities at the overflow group. Table A.1/E.737 gives a (not exhaustive) list of available methods.
+
+Annex B gives another example method which is not included in Table A.1/E.737.
+
+## 8 History
+
+The first issue in 1995, revised in 2000.
+
+## 9 Bibliography
+
+- [1] ODA (T.): Moment Analysis for Traffic Associated with Markovian queueing Systems, *IEEE Transactions on Communications*, Vol. 39, No. 5, pp. 737-746, May 1991.
+- [2] LE GALL (P.): Overflow traffic combination and cluster engineering, *Proceedings of ITC-11*, paper 2.2 B-1, Kyoto 1985.
+- [3] de PAZ (C.): A non-linear dynamic analysis of overflow traffic, *Comunicaciones de Telefónica I + D*, No. 19, December 2000.
+
+## ANNEX A
+
+### Example methods for calculating overflow variances from a first-choice group
+
+### A.1 Assumptions and notations
+
+Consider a first-choice group with multi-slot bearer services to which Poisson traffic streams are input. It is assumed that the circuit group is operated in full availability. The following notations are used.
+
+#### Model parameters
+
+- $N$  capacity of the group (number of slots in the group).
+- $I$  number of traffic streams.
+- $i$  identifier of traffic stream,  $i = 1, 2, \dots, I$ .
+- $\lambda_i$  arrival rate of traffic stream  $i$ .
+- $\mu_i$  reciprocal of mean holding time of calls in stream  $i$ .
+- $A_i$  traffic intensity measured in number of calls,  $A_i = \lambda_i/\mu_i$ .
+- $d_i$  number of circuits used by a call in stream  $i$ .
+- $B_i$  call blocking probability of traffic stream  $i$  at the first-choice group.
+- $O_i$  mean of overflow  $i$ .
+- $V_i$  variance of overflow  $i$ .
+- $Z_i$  peakedness of overflow  $i$ .
+
+#### Notations for calculation
+
+- $n_i$  number of calls in stream  $i$  in progress.
+- $\mathbf{n}$  state of the group,  $\mathbf{n} = (n_1, n_2, \dots, n_I)$ .
+- $E$  state space of the group  $E = (\mathbf{n})$ .
+- $|E|$  total number of states in the state space  $E$ .
+- $\mathbf{Q}$   $|E| \times |E|$  coefficient matrix of steady state equations.
+- $\boldsymbol{\pi}$  steady state probabilities vector of the group.
+
+$\mathbf{R}_i$   $|E| \times |E|$  overflow rate matrix of traffic stream  $i$ .
+
+$\mathbf{f}_i$  the first moment vector of overflow  $i$ .
+
+$F_i$  the first moment of overflow  $i$ .
+
+$S_i$  the second moment of overflow  $i$ .
+
+$\mathbf{e}$   $|E| \times 1$  vector with all the element equal to unity.
+
+$\mathbf{I}$   $|E| \times |E|$  diagonal matrix with all the diagonal elements equal to unity.
+
+Note that the steady state probabilities  $\boldsymbol{\pi}$  are given as a solution of  $\boldsymbol{\pi}\mathbf{Q} = 0$  and  $\boldsymbol{\pi}\mathbf{e} = 1$  and that it has the product-form solution in special cases, as stated in Recommendations E.526, E.731 and E.737.
+
+The overflow rate matrix  $\mathbf{R}_i = [r_i(\mathbf{n}_1, \mathbf{n}_2)]$  is a diagonal matrix whose  $\mathbf{n}$ -th diagonal element  $r_i(\mathbf{n}, \mathbf{n})$  is given as follows:
+
+$$r_i(\mathbf{n}, \mathbf{n}) = \begin{cases} \lambda_i & : \text{ if an arriving call in stream } i \text{ is rejected at state } \mathbf{n}, \\ 0 & : \text{ otherwise.} \end{cases} \quad (\text{A.1-1})$$
+
+### A.2 Variance calculation methods
+
+#### A.2.1 Exact solution method
+
+The mean and variance of stream  $i$  overflow can be calculated by the following procedure.
+
+##### Exact calculation procedure
+
+Step 1) Calculate  $\boldsymbol{\pi}$  and  $\mathbf{B}_i$ .
+
+Step 2) Calculate the mean  $O_i$  from  $O_i = A_i B_i$ .
+
+Step 3) Solve the following system of linear equation for the vector  $\mathbf{f}_i$ :
+
+$$\mathbf{f}_i(\mu_i \mathbf{I} - \mathbf{Q}) = \boldsymbol{\pi} \mathbf{R}_i \quad (\text{A.2-1})$$
+
+Step 4) Calculate  $F_i$  and  $S_i$  by:
+
+$$F_i = O_i \quad (\text{A.2-2})$$
+
+$$S_i = \left( \frac{1}{\mu_i} \right) \mathbf{f}_i \mathbf{R}_i \mathbf{e} + F_i \quad (\text{A.2-3})$$
+
+Step 5) Calculate the variance  $V_i$  and peakedness  $Z_i$  by:
+
+$$V_i = S_i - (F_i)^2 \quad (\text{A.2-4})$$
+
+$$Z_i = V_i / O_i \quad (\text{A.2-5})$$
+
+Derivation of the equations (A.2-1) to (A.2-3) and numerical examples can be found in [1]. The above calculation procedure for the variances can also be applied to the multi-slot groups where a service protection scheme such as trunk reservation described in Recommendations E.526, E.731 and E.737 is used.
+
+It should be remarked that, when the size of group and/or the number of traffic streams are large, computational complexity of solving the above equation (A.2-1) in Step 3) becomes considerably large due to high dimensionality.
+
+#### A.2.2 Approximation method
+
+In order to lessen the computational complexity to calculate the second moment  $S_i$ , the following approximation method may be used when the circuit group is operated in full availability.
+
+The principle of the approximation method is to establish a hypothetical stochastic process whose state space size is tractably smaller than that of the original state space  $E$ . Consider a state space  $E' = (j : 0 \leq j \leq N)$ . Assuming that the group is operated by complete sharing policy and the probabilities  $\pi$  are known and also letting  $E_j$  denote a subspace of  $E$  of the group such that  $J = (n : \sum_{i=1,2,\dots,I} d_i n_i = j)$ , the state transition rates  $q(j_1, j_2)$  in the state space  $E'$  are set as follows:
+
+$$q(j_1, j_2) = \begin{cases} \lambda_i & : 0 \leq j_1 \leq N - d_i, j_2 = j_1 + d_i, \text{ for all } i, \\ \xi_i(j_i) & : d_i \leq j_1 \leq N, j_2 = j_1 - d_i, \text{ for all } i, \\ 0 & : \text{otherwise} \end{cases} \quad (\text{A.2-6})$$
+
+where  $\xi_k(j)$  is given by:
+
+$$\xi_i(j) = \mu_i E \left[ n_i \mid \sum_{i=1,2,\dots,I} d_i n_i = j \right] = \mu_i \left\{ \sum_{n \in E_j} n_i \pi(n) \right\} / \left\{ \sum_{n \in E_j} \pi(n) \right\} \quad (\text{A.2-7})$$
+
+The following notations are used as regards to the state transition model:
+
+$Q'$   $N \times N$  coefficient matrix of the steady state equations,  $Q' = [q(j_1, j_2)]$ .
+
+$\pi'$   $N \times 1$  vector with  $N$  element that satisfies the system of equations  $\pi' Q' = 0$  and  $\pi' e = 1$ .
+
+$R_i'$   $N \times N$  overflow rate matrix of traffic stream  $i$ .
+
+$f_i'$  the first moment vector of overflow  $i$ .
+
+$S_i'$  approximate second moment of overflow  $i$ .
+
+Note that it holds that  $\pi'(j) = \sum_{n \in E_j} \pi(n)$ . The matrix  $R_i' = [r_i'(j_1, j_2)]$  is a diagonal matrix whose  $j$ -th diagonal element  $r_i'(j, j)$  is given as follows:
+
+$$r_i'(j, j) = \begin{cases} \lambda_i & : \text{if an arriving call in stream } i \text{ is rejected at state } j, \\ 0 & : \text{otherwise.} \end{cases} \quad (\text{A.2-8})$$
+
+The calculation procedure for an approximation to the variance of each overflow can be constructed as follows:
+
+##### Approximation procedure
+
+Step 1) Calculate  $\pi$  and  $B_i$ .
+
+Step 2) Calculate the mean  $O_i$  from  $O_i = A_i B_i$ .
+
+Step 3) Solve the following system of linear equation for the vector  $f_i'$ :
+
+$$f_i' (\mu_i I - Q') = \pi' R_i' \quad (\text{A.2-9})$$
+
+Step 4) Calculate  $F_i$  and  $S_i'$  by:
+
+$$F_i = O_i \quad (\text{A.2-10})$$
+
+$$S_i' = (1/\mu_i) f_i' R_i' e + F_i \quad (\text{A.2-11})$$
+
+Step 5) Calculate the approximate variance  $V_i'$  and peakedness  $Z_i'$  by:
+
+$$V_i' = S_i' - (F_i)^2 \quad (\text{A.2-12})$$
+
+$$Z_i' = V_i'/O_i \quad (\text{A.2-13})$$
+
+Numerical examples can be found in [1]. Especially, when all the service rates  $\mu_i$  are the same and no trunk reservation is applied, the approximation is good.
+
+## ANNEX B
+
+### Example method for calculating individual call blocking probabilities of an overflow group
+
+### B.1 Reduced network method
+
+This method is derived from [2].
+
+### B.2 Notations
+
+#### For partial overflow traffic of $n^{0,i}$ ( $i = 1, \dots, x$ )
+
+- number of simultaneous time slots:  $d_i$ .
+- traffic intensity (in calls):  $b_i$ .
+- traffic intensity (in circuits):  $(b_i \cdot d_i)$ .
+- overflow function:  $\rho_i(n)$ .
+- peakedness factor:  $z_i = \frac{\text{variance}}{\text{mean}}$  (of traffic).
+- equivalent capacity (in calls):  $n_i$ .
+
+#### For the first-choice circuit group of $n^{0,i}$
+
+- number of circuits:  $m_i$ .
+- offered traffic intensity (in calls):  $a_i$ .
+- probability of overflow:  $p_i = E_{m_i/d_i}(a_i)$  where  $E_n(a)$  is the Erlang loss formula extended to the case where  $n$  need not be an integer. We have the relationship:  $b_i = a_i p_i$ .
+
+#### For the overflow group
+
+- number of circuits:  $N$ .
+- total traffic intensity (in calls):  $b = \sum_{i=1}^x b_i$
+- total traffic intensity (in circuits):  $M = \sum_{i=1}^x b_i d_i$
+- reduction factor:  $Z_0$ .
+- time congestion:  $\Pi$ 
+  - Second overflow traffic intensity (in calls):  $O_i$ .
+  - Probability of partial blocking:  $B_i = O_i/b_i$ .
+
+### B.3 Determination of equivalent capacity $n_i$
+
+The overflow function  $\rho_i(n)$  is defined by the following recurrent process, derived from recurrent process (6-1) in E.524:
+
+$$\rho_i(0) = p_i = E_{m_i/d_i}, \rho_i(n) = p_i = E_{m_i/d_i}(a_i), \frac{n}{\rho_i(n)} = \left( \frac{m_i}{d_i} + n - a_i \right) + a_i \rho_i(n-1) \quad (B-1)$$
+
+This recurrent process may produce numerical instabilities leading to values with significant numerical error when the following condition occurs:
+
+$$\frac{\alpha_i(n) - \sqrt{a_i \cdot (n+1)}}{a_i} < \rho_i(n) < \frac{\alpha_i(n) + \sqrt{a_i \cdot (n+1)}}{a_i} \quad (B-2)$$
+
+with:
+
+$$\alpha_i(n) = a_i - \frac{m_i}{d_i} - n - 1 \quad (B-3)$$
+
+To avoid this computational difficulty, the following tight upper bound to  $\rho_i(n)$  can be used (see [3]):
+
+$$\rho_i(n) < \frac{\sqrt{\alpha_i^2(n) + 4a_i \cdot (n+1)} - \alpha_i(n)}{2a_i} \quad (B-4)$$
+
+with  $\alpha_i(n)$  given by formula (B-3). This upper bound has the following two properties:
+
+- a) The upper bound becomes tighter as  $n$  increases.
+- b) It is calculated directly from formula (B-4) without the recursive process.
+
+The *equivalent capacity*  $n_i$  (in calls) is the solution of the following set of equations, derived from the set (6-2) of Recommendation E.524:
+
+$$\frac{n_i}{N} = \frac{a_i \rho_i(n_i) / D_i(n_i + 1)}{\sum_{k=1}^x a_k d_k \rho_k(n_k) / D_k(n_k + 1)}, \quad i = 1, \dots, x \quad (B-5)$$
+
+with:
+
+$$D_i(n) = 1 + a_i [\rho_i(n) - \rho_i(n-1)] \quad (B-6)$$
+
+The only modification is the insertion of the parameter  $d_k$  in the denominator of (6-2) in E.524. The *peakedness factor*  $z_i$  is given by the expression:
+
+$$z_i = D_i(1) \quad (B-7)$$
+
+NOTE – For direct traffic we have:  $m_i = 0, b_i = a_i, \rho_i(n) = D_i(n) = 1$ .
+
+### B.4 Time congestion II
+
+The expression (A-3) in Annex A/E.526 becomes:
+
+$$\Pi = B_1 \approx \left( \frac{1}{Z_0} \right) \cdot E_{N/Z_0} \left( \frac{M}{Z_0} \right) \quad (B-8)$$
+
+the reduction factor becoming:
+
+$$Z_0 = \frac{\sum_{i=1}^x a_i d_i^2 \rho_i(n_i)}{\sum_{i=1}^x b_i d_i} \quad (B-9)$$
+
+$E_n(a)$  is the Erlang loss formula with  $n$  fractional. It will be remembered that  $\Pi$  is equal to the blocking probability  $B_1$  of a direct traffic ( $m_i = 0$ ) with simple time slots ( $d_i = 1$ ) and arrivals conforming to Poisson's law.
+
+### B.5 Blocking probability $B_i$
+
+The factor  $H_i(d_i)$  is the same as the factor  $H_i$  in Annex A/E.526. We thus obtain, for the blocking probability of partial traffic stream  $n^{0,i}$ :
+
+$$B_i = B_1 \cdot \frac{\rho_i(n_i)}{E_{m_i} / (a_i / d_i)} \cdot H_i(d_i) \quad \text{with} \quad H_i(d_i) = \frac{K^{d_i} - 1}{K - 1} \quad (B-10)$$
+
+where the term  $K$  is defined as:
+
+$$K = \left[ \frac{N}{M} \right]^{1/Z} \quad \text{with : } V = \sum_{i=1}^x b_i d_i^2 \text{ and } Z = \frac{V}{M} \quad (B-11)$$
+
+### B.6 The second overflow
+
+Formula (6-4) in E.524 now gives, for the intensity of *the second partial overflow*  $O_i$  (in calls):
+
+$$O_i = a_i \rho_i(n_i) H_i(d_i) \times \Pi \quad (B-12)$$
+
+Similarly, formula (6-5) in E.524 modified gives, for the partial grade of service equalization:
+
+$$\rho_i(n_i) \cdot H_i(d_i) = C \quad (B-13)$$
+
+where  $C$  is an economically suitable constant.
+
+NOTE – This equalization is only possible for a fairly low  $d_i$ . For video communications (large  $d_i$ ), it is necessary to have recourse to service protection methods.
+
+### B.7 Field of application
+
+This approximate method may be used for:
+
+$$d \leq 10, z \leq 3 \quad (B-14)$$
+
+### B.8 Processing time and programming effort
+
+The values given in Table 2/E.524 hold approximately.
+
+
+
+
+
+# ITU-T RECOMMENDATIONS SERIES
+
+|                 |                                                                                                                                |
+|-----------------|--------------------------------------------------------------------------------------------------------------------------------|
+| Series A        | Organization of the work of the ITU-T                                                                                          |
+| Series B        | Means of expression: definitions, symbols, classification                                                                      |
+| Series C        | General telecommunication statistics                                                                                           |
+| Series D        | General tariff principles                                                                                                      |
+| <b>Series E</b> | <b>Overall network operation, telephone service, service operation and human factors</b>                                       |
+| Series F        | Non-telephone telecommunication services                                                                                       |
+| Series G        | Transmission systems and media, digital systems and networks                                                                   |
+| Series H        | Audiovisual and multimedia systems                                                                                             |
+| Series I        | Integrated services digital network                                                                                            |
+| Series J        | Transmission of television, sound programme and other multimedia signals                                                       |
+| Series K        | Protection against interference                                                                                                |
+| Series L        | Construction, installation and protection of cables and other elements of outside plant                                        |
+| Series M        | TMN and network maintenance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits |
+| Series N        | Maintenance: international sound programme and television transmission circuits                                                |
+| Series O        | Specifications of measuring equipment                                                                                          |
+| Series P        | Telephone transmission quality, telephone installations, local line networks                                                   |
+| Series Q        | Switching and signalling                                                                                                       |
+| Series R        | Telegraph transmission                                                                                                         |
+| Series S        | Telegraph services terminal equipment                                                                                          |
+| Series T        | Terminals for telematic services                                                                                               |
+| Series U        | Telegraph switching                                                                                                            |
+| Series V        | Data communication over the telephone network                                                                                  |
+| Series X        | Data networks and open system communications                                                                                   |
+| Series Y        | Global information infrastructure and Internet protocol aspects                                                                |
+| Series Z        | Languages and general software aspects for telecommunication systems                                                           |
+
+\*18543\*

marked/E/T-REC-E.541-198811-I_PDF-E/raw.md

@@ -0,0 +1,133 @@
+
+
+![ITU logo](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg)
+
+The logo of the International Telecommunication Union (ITU) features the letters 'ITU' in a bold, sans-serif font, superimposed on a stylized globe with intersecting lines.
+
+ITU logo
+
+INTERNATIONAL TELECOMMUNICATION UNION
+
+**ITU-T**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+**E.541**
+
+**TELEPHONE NETWORK AND ISDN**
+
+**QUALITY OF SERVICE, NETWORK MANAGEMENT  
+AND TRAFFIC ENGINEERING**
+
+---
+
+**OVERALL GRADE OF SERVICE FOR  
+INTERNATIONAL CONNECTIONS  
+(SUBSCRIBER-TO-SUBSCRIBER)**
+
+**ITU-T Recommendation E.541**
+
+(Extract from the *Blue Book*)
+
+---
+
+## NOTES
+
+1 ITU-T Recommendation E.541 was published in Fascicle II.3 of the *Blue Book*. This file is an extract from the *Blue Book*. While the presentation and layout of the text might be slightly different from the *Blue Book* version, the contents of the file are identical to the *Blue Book* version and copyright conditions remain unchanged (see below).
+
+2 In this Recommendation, the expression “Administration” is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+# **OVERALL GRADE OF SERVICE FOR INTERNATIONAL CONNECTIONS (SUBSCRIBER-TO-SUBSCRIBER)**
+
+## **1 Introduction**
+
+1.1 The overall grade of service (subscriber-to-subscriber) on international connections – relating only to the phenomena of congestion in the entire network as a result of the traffic flow – depends on a number of different factors, such as the routing arrangements in the national and international parts of the connection, congestion allowed per switching stage, the methods used to measure traffic and compute the traffic base, and the time differences between the busy hours of the various links involved in the connection.
+
+1.2 The most satisfactory way in which this grade of service could be described would be to give its distribution. The design average grade of service during the busy hour of the complete connection would be the most useful single parameter. However, until such time as continuous traffic measurements are carried out during the busy season in all parts of the network on a routine basis, it is not possible to compute this average grade of service. Therefore, at this stage it cannot be used as a criterion for the dimensioning of the network.
+
+1.3 The only practical way of ensuring an acceptable overall grade of service on international calls is to specify an upper limit on the design loss probability per connecting link in the national network as is done for the links in the international network (see Recommendation E.540).
+
+## **2 General considerations**
+
+2.1 Since the success of the international automatic service is highly dependent on the grade of service of all links involved in the connection from subscriber-to-subscriber, it is desirable that the originating and terminating national network involved in the connection has grade of service standards comparable with those of the international network.
+
+2.2 It is especially important that the links in the country of destination should have a good grade of service for handling the traffic, since high congestion in the terminating national network could have serious effects on the international network. High congestion in the network of the country of destination causes added retrials with consequent increased loading on common switching devices as well as increased occupation of the routes with ineffective calls.
+
+## **3 Design objectives**
+
+3.1 It is recommended that the links in the national network should be designed for a loss probability<sup>1)</sup> not exceeding 1 per cent per link in the final choice route during its applicable busy hour. It is recognized, however, that in some countries additional congestion is permitted for the internal switching stages of the transit exchanges. It is also recognized that, where this recommended grade of service is not provided for the national service, it may not be economically feasible to provide it for international relations.
+
+3.2 The maximum number of links in tandem used by an international connection is defined by Recommendation E.171 [1].
+
+3.3 Although the worst overall grade of service would be approximated by the sum of loss probabilities for individual links connected in tandem, on most calls the overall grade of service will be significantly better.
+
+---
+
+<sup>1)</sup> The loss probability mentioned refers to busy hour traffic values as defined in Recommendation E.500.
+
+## 4 Maximum traffic loading
+
+4.1 An acceptable automatic service on a final circuit group is difficult to maintain if the traffic loading on the group exceeds a level corresponding to a calculated Erlang grade of service of 10 per cent. Beyond this traffic loading, service on the route may rapidly deteriorate. This condition will be accentuated under the cumulative effect of repeat attempt calls if these should occur.
+
+4.2 The curves of Figure 1/E.541 indicate the proportionate reduction in circuits that may be tolerated for a short period, 15 minutes for example, under normal busy-hour conditions, on a full-availability circuit group dimensioned for 1 per cent Erlang loss, in accordance with the above traffic overload criterion. Table 1/E.541 gives the figures used to plot the curves.
+
+![Line graph showing the proportionate reduction in the number of circuits in a final group in the event of a breakdown. The Y-axis is 'Per cent reduction in circuits allowed so that 1 % congestion will become no more than 10% congestion' (0-50%). The X-axis is 'Number of circuits in the final group' (0-150). Two curves are shown: Curve 1 (peakedness factor = 2.5) and Curve 2 (random traffic, peakedness factor = 1.0). Both curves show a decreasing trend as the number of circuits increases.](f961cbef0f8217e216b553bed270315b_img.jpg)
+
+| Number of circuits in the final group | Per cent reduction (Curve 1: peakedness factor = 2.5) | Per cent reduction (Curve 2: random traffic, peakedness factor = 1.0) |
+|---------------------------------------|-------------------------------------------------------|-----------------------------------------------------------------------|
+| 10                                    | 40                                                    | 32                                                                    |
+| 20                                    | 33                                                    | 27                                                                    |
+| 30                                    | 30                                                    | 24                                                                    |
+| 50                                    | 26                                                    | 21                                                                    |
+| 100                                   | 22                                                    | 18                                                                    |
+| 150                                   | 19                                                    | 16                                                                    |
+
+Line graph showing the proportionate reduction in the number of circuits in a final group in the event of a breakdown. The Y-axis is 'Per cent reduction in circuits allowed so that 1 % congestion will become no more than 10% congestion' (0-50%). The X-axis is 'Number of circuits in the final group' (0-150). Two curves are shown: Curve 1 (peakedness factor = 2.5) and Curve 2 (random traffic, peakedness factor = 1.0). Both curves show a decreasing trend as the number of circuits increases.
+
+- 1: peakedness factor = 2.5
+- 2: random traffic (peakedness factor = 1.0)
+
+FIGURE 1/E.541  
+Proportionate reduction in the number of circuits in a final group in the event of a breakdown  
+if the calculated Erlang grade of service is not to exceed 10 per cent
+
+TABLE 1/E.541
+
+### **Percentage reduction in the number of circuits if the calculated Erlang grade of service is not to exceed 10%**
+
+| Number of circuits | If originally operating at 1 % congestion, % reduction in circuits allowed to yield 10 % congestion |                         |
+|--------------------|-----------------------------------------------------------------------------------------------------|-------------------------|
+|                    | Random traffic<br>(peakedness factor = 1.0)                                                         | Peakedness factor = 2.5 |
+| 5                  | 37.7                                                                                                | –                       |
+| 10                 | 32.3                                                                                                | 40.2                    |
+| 20                 | 27.2                                                                                                | 33.3                    |
+| 30                 | 24.8                                                                                                | 30.1                    |
+| 50                 | 21.7                                                                                                | 26.5                    |
+| 100                | 18.3                                                                                                | 22.4                    |
+| 150                | 16.7                                                                                                | 19.7                    |
+
+4.3 The curves of Figure 1/E.541 are intended merely as a guide. If the breakdown occurs during an exceptionally busy hour, the permissible proportionate reduction will be less. Conversely, if the breakdown occurs during an hour of light traffic, a higher proportionate reduction in circuits could be tolerated. A higher reduction might also be acceptable after an appropriate oral announcement has been introduced. In the general case, a knowledge of the circuit occupancy will enable an estimate to be made of the prevailing Erlang loss figure with the reduced number of circuits.
+
+The permissible reduction in the case of large groups should not be exceeded; otherwise very serious congestion can result from repeated attempts.
+
+## 5 General notes
+
+*Note 1* – Teletraffic implications for international switching and operational procedures under failure of a transmission facility are discussed in Supplement No. 5 of this fascicle.
+
+*Note 2* – Alternative routing in the national and in the international networks provides on average a grade of service that is better than that provided in the theoretical final route.
+
+*Note 3* – Non-coincidence of traffic peaks in the national and international networks will provide reduction in the overall grade of service compared with the sum of the design grade of service values per link.
+
+*Note 4* – Time differences will also improve the resulting grade of service.
+
+*Note 5* – The methods of measuring and calculating the traffic base for provisioning purposes in the national networks may be different in various countries and differ from the methods for the international network given in Recommendation E.500. This means that the national traffic values are not always comparable among themselves or with the values of the international network. Each Administration must estimate how its design traffic level compares with that recommended for the international network.
+
+*Note 6* – The design grade of service value of each link will only apply if the traffic at each switching stage is equal to the forecast. In practice, such a situation will seldom occur. Furthermore, the planning procedure normally is such that the specified grade of service should not be exceeded until the end of the planning period. In a growing network, this means that the circuit groups during almost the whole planning period give a better service than the specified critical standard.
+
+In conclusion, the overall grade of service depends on the accuracy of forecasts made and the planning procedure used, i.e. it depends on the interval between plant additions and on the specific traffic value in future to which the grade of service is related.
+
+## Reference
+
+- [1] CCITT Recommendation *International routing plan*, Rec. E.171.

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+
+
+![ITU logo: A globe with a lightning bolt and the letters ITU.](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg)
+
+ITU logo: A globe with a lightning bolt and the letters ITU.
+
+INTERNATIONAL TELECOMMUNICATION UNION
+
+**ITU-T**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+**E.671**
+
+(03/2000)
+
+SERIES E: OVERALL NETWORK OPERATION,  
+TELEPHONE SERVICE, SERVICE OPERATION AND  
+HUMAN FACTORS
+
+Quality of service, network management and traffic  
+engineering – Traffic engineering – Definitions
+
+---
+
+**Post-selection delay in PSTN/ISDN networks  
+using Internet telephony for a portion of the  
+connection**
+
+ITU-T Recommendation E.671
+
+(Formerly CCITT Recommendation)
+
+---
+
+# ITU-T E-SERIES RECOMMENDATIONS **OVERALL NETWORK OPERATION, TELEPHONE SERVICE, SERVICE OPERATION AND HUMAN FACTORS**
+
+## **OPERATION, NUMBERING, ROUTING AND MOBILE SERVICES**
+
+## **INTERNATIONAL OPERATION**
+
+|                                                        |             |
+|--------------------------------------------------------|-------------|
+| Definitions                                            | E.100–E.103 |
+| General provisions concerning Administrations          | E.104–E.119 |
+| General provisions concerning users                    | E.120–E.139 |
+| Operation of international telephone services          | E.140–E.159 |
+| Numbering plan of the international telephone service  | E.160–E.169 |
+| International routing plan                             | E.170–E.179 |
+| Tones in national signalling systems                   | E.180–E.189 |
+| Numbering plan of the international telephone service  | E.190–E.199 |
+| Maritime mobile service and public land mobile service | E.200–E.229 |
+
+## **OPERATIONAL PROVISIONS RELATING TO CHARGING AND ACCOUNTING IN THE INTERNATIONAL TELEPHONE SERVICE**
+
+|                                                                |             |
+|----------------------------------------------------------------|-------------|
+| Charging in the international telephone service                | E.230–E.249 |
+| Measuring and recording call durations for accounting purposes | E.260–E.269 |
+
+## **UTILIZATION OF THE INTERNATIONAL TELEPHONE NETWORK FOR NON-TELEPHONY APPLICATIONS**
+
+|                 |             |
+|-----------------|-------------|
+| General         | E.300–E.319 |
+| Phototelegraphy | E.320–E.329 |
+
+## **ISDN PROVISIONS CONCERNING USERS**
+
+|                            |             |
+|----------------------------|-------------|
+| International routing plan | E.350–E.399 |
+|----------------------------|-------------|
+
+## **QUALITY OF SERVICE, NETWORK MANAGEMENT AND TRAFFIC ENGINEERING**
+
+### **NETWORK MANAGEMENT**
+
+|                                                             |             |
+|-------------------------------------------------------------|-------------|
+| International service statistics                            | E.400–E.409 |
+| International network management                            | E.410–E.419 |
+| Checking the quality of the international telephone service | E.420–E.489 |
+
+## **TRAFFIC ENGINEERING**
+
+|                                                                                   |             |
+|-----------------------------------------------------------------------------------|-------------|
+| Measurement and recording of traffic                                              | E.490–E.505 |
+| Forecasting of traffic                                                            | E.506–E.509 |
+| Determination of the number of circuits in manual operation                       | E.510–E.519 |
+| Determination of the number of circuits in automatic and semi-automatic operation | E.520–E.539 |
+| Grade of service                                                                  | E.540–E.599 |
+
+|                                    |                    |
+|------------------------------------|--------------------|
+| <b>Definitions</b>                 | <b>E.600–E.699</b> |
+| ISDN traffic engineering           | E.700–E.749        |
+| Mobile network traffic engineering | E.750–E.799        |
+
+## **QUALITY OF TELECOMMUNICATION SERVICES: CONCEPTS, MODELS, OBJECTIVES AND DEPENDABILITY PLANNING**
+
+|                                                                                             |             |
+|---------------------------------------------------------------------------------------------|-------------|
+| Terms and definitions related to the quality of telecommunication services                  | E.800–E.809 |
+| Models for telecommunication services                                                       | E.810–E.844 |
+| Objectives for quality of service and related concepts of telecommunication services        | E.845–E.859 |
+| Use of quality of service objectives for planning of telecommunication networks             | E.860–E.879 |
+| Field data collection and evaluation on the performance of equipment, networks and services | E.880–E.899 |
+
+## **POST-SELECTION DELAY IN PSTN/ISDN NETWORKS USING INTERNET TELEPHONY FOR A PORTION OF THE CONNECTION**
+
+## **Summary**
+
+This Recommendation proposes a post-selection delay Grade of Service (GOS) parameter and target values when part of a PSTN/ISDN connection is replaced by Internet Protocol (IP) based network(s). This parameter is defined and their target values specified assuming that the network and the network components are fully operational. Also, only point-to-point connections supporting basic call flows are considered in this release of the Recommendation.
+
+###### **Source**
+
+ITU-T Recommendation E.671 was prepared by ITU-T Study Group 2 (1997-2000) and was approved under the WTSC Resolution No. 1 procedure on 13 March 2000.
+
+## FOREWORD
+
+ITU (International Telecommunication Union) is the United Nations Specialized Agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the ITU. The ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis.
+
+The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics.
+
+The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Resolution No. 1.
+
+In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC.
+
+### NOTE
+
+In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+### INTELLECTUAL PROPERTY RIGHTS
+
+The ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. The ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process.
+
+As of the date of approval of this Recommendation, the ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database.
+
+© ITU 2000
+
+All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU.
+
+## CONTENTS
+
+###### Page
+
+|     |                                |   |
+|-----|--------------------------------|---|
+| 1   | Scope.....                     | 1 |
+| 2   | References.....                | 1 |
+| 3   | Abbreviations.....             | 2 |
+| 4   | Post-selection delay GOS ..... | 2 |
+| 4.1 | GOS concepts .....             | 2 |
+| 4.2 | Definitions .....              | 2 |
+| 4.3 | Target values .....            | 2 |
+| 5   | Reference connections .....    | 3 |
+| 6   | GOS objectives .....           | 5 |
+| 7   | History.....                   | 5 |
+
+
+
+## **POST-SELECTION DELAY IN PSTN/ISDN NETWORKS USING INTERNET TELEPHONY FOR A PORTION OF THE CONNECTION**
+
+*(Geneva, 2000)*
+
+## **1 Scope**
+
+This Recommendation proposes a post-selection delay Grade of Service (GOS) parameter and target values when part of a PSTN/ISDN connection is replaced by Internet Protocol (IP) based network(s). This parameter is defined and their target values specified assuming that the network and the network components are fully operational. Also, only point-to-point connections supporting basic call flows are considered in this release of the Recommendation.
+
+NOTE 1 – Other GOS parameters such as answer-signal delay, call-release delay, and probability of end-to-end blocking, require further study.
+
+NOTE 2 – This release of the Recommendation is concerned only with the case of *transparent service*, i.e. users will not be aware of the fact that a portion of the circuit-switched connection is being replaced by IP telephony. When this is not the case, IP telephony may be used to facilitate the offering of a set of service classes with different qualities of service. This subject requires further study.
+
+## **2 References**
+
+The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; all users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published.
+
+- ITU-T Recommendation E.500 (1998), *Traffic intensity measurement principles*.
+- CCITT Recommendation E.540 (1988), *Overall grade of service of the international part of an international connection*.
+- CCITT Recommendation E.541 (1988), *Overall grade of service for international connections (subscriber-to-subscriber)*.
+- ITU-T Recommendation E.651 (2000), *Reference connections for traffic engineering of IP access networks*.
+- ITU-T Recommendation E.721 (1999), *Network grade of service parameters and target values for circuit-switched services in the evolving ISDN*.
+- ITU-T Recommendation E.771 (1996), *Network grade of service parameters and target values for circuit-switched land mobile services*.
+- ITU-T Draft Recommendation Y.1231, *IP access network architecture*.
+- ITU-T Draft Recommendation Y.1530, *Call processing performance for voice service in hybrid IP networks*.
+
+## 3 Abbreviations
+
+This Recommendation uses the following abbreviations:
+
+|      |                                     |
+|------|-------------------------------------|
+| GOS  | Grade of Service                    |
+| IP   | Internet Protocol                   |
+| ISDN | Integrated Services Digital Network |
+| PSTN | Public Switched Telephone Network   |
+| TE   | Terminal Equipment                  |
+| VOIP | Voice Over Internet Protocol        |
+
+## 4 Post-selection delay GOS
+
+### 4.1 GOS concepts
+
+GOS parameters were developed for traditional circuit-switched PSTN and standards set in Recommendations E.540 and E.541. GOS concepts were refined and new standards set in the context of circuit-switched services on ISDN. The new standards are given in Recommendations E.720 and E.721. This Recommendation is based on the concepts, parameter definitions, and service types given in Recommendation E.721.
+
+### 4.2 Definitions
+
+The following two definitions of "post-selection delay", as specified in Recommendation E.721, are reproduced herein for ease of reference.
+
+**4.2.1 post-selection delay (overlap sending)** is defined as the time interval from the instant the first bit of the INFORMATION message containing the last selection digit is passed by the calling terminal to the access signalling system until the last bit of the first message indicating call disposition is received by the calling terminal (ALERTING message in case of successful call).
+
+**4.2.2 post-selection delay (*en bloc sending*)** is defined as the time interval from the instant the first bit of the initial SETUP message containing all the selection digits is passed by the calling terminal to the access signalling system until the last bit of the first message indicating call disposition is received by the calling terminal (ALERTING message in case of successful call).
+
+NOTE – In case of automatic answering terminals, the ALERTING message is replaced by the CONNECT message.
+
+### 4.3 Target values
+
+When IP-based networks are used to substitute for a portion of the circuit-switched PSTN/ISDN connection, users will expect and network providers should meet comparable end-to-end post-selection delay as is encountered on connections provided entirely on PSTN/ISDNs. Refinement of the target values which are provisionally specified herein is for further study.
+
+NOTE – If and when IP telephony is used to provide a set of service classes with different qualities of service, the services so provided will not be transparent to the user in the sense of Note 2, in clause 1. In this case, the target values for the respective service classes will necessarily be different from the ones specified in this Recommendation.
+
+## 5 Reference connections
+
+This Recommendation is concerned with the class of *PSTN/ISDN-to-PSTN/ISDN via IP* reference connections as specified in 6.2.3/E.651. It is reproduced in Figure 1.
+
+![Diagram of PSTN/ISDN-to-PSTN/ISDN connection via IP](562f471e8153729557e6a4ee6343c32c_img.jpg)
+
+The diagram illustrates a reference connection path. It starts with a rectangular box labeled 'TE' on the left, connected to an oval labeled 'PSTN/ISDN'. This is followed by a rectangular box labeled 'VOIP gateway', which connects to an oval labeled 'IP core network'. This is followed by another rectangular box labeled 'VOIP gateway', which connects to an oval labeled 'PSTN/ISDN'. Finally, this oval connects to a rectangular box labeled 'TE' on the right. The text 'T0207910-99' is located in the bottom right corner of the diagram area.
+
+Diagram of PSTN/ISDN-to-PSTN/ISDN connection via IP
+
+**Figure 1/E.671 – PSTN/ISDN-to-PSTN/ISDN connection via IP**
+
+The *IP core network* "cloud" in the diagram is also commonly referred to as the "IP backbone". It provides wide-area coverage and interconnection between domains. As specified in Draft Recommendation Y.1231, the IP core network may include one or more IP service provider networks.
+
+The *Voice Over IP (VOIP) gateway* is responsible for the translation and handling of voice calls between PSTN/ISDN and IP core network.
+
+For this class of reference connections, there are three cases of interest for which separate standards for the IP portion of an overall connection can be set. These are:
+
+- *Connection type 1*: IP as a national network where the IP-based network replaces a national PSTN/ISDN in a long-distance connection.
+- *Connection type 2*: IP as an international network where the IP-based network replaces the international portion of an international connection. There are three subcases:
+  - a) The PSTN/ISDNs at both the originating and terminating ends are not replaced by an IP-based network;
+  - b) The PSTN/ISDN at the originating end is replaced by an IP-based network;
+  - c) The PSTN/ISDN at the terminating end is replaced by an IP-based network.
+- *Connection type 3*: IP as an end-to-end network where the IP-based network replaces both the national and international portions of an international connection.
+
+These three types of reference connections are given in Figure 2. [For connection type 2, only subcase a) is shown in the figure.]
+
+![Diagram of Connection type 1: National IP network](f4fdd410cdb84df81274da55721e56fb_img.jpg)
+
+A diagram showing a 'Local switch' connected to a 'National IP Network' cloud via 'VOIP' interfaces at both ends. Each 'Local switch' is further connected to a telephone handset icon.
+
+Diagram of Connection type 1: National IP network
+
+Connection type 1: National IP network
+
+![Diagram of Connection type 2: International IP network](e6df2733626a85205c1db682e6259c46_img.jpg)
+
+A diagram showing a 'Local switch' connected to a 'National PSTN' cloud, which is connected to an 'International IP Network' cloud via 'VOIP' interfaces. The 'International IP Network' cloud is connected to another 'National PSTN' cloud, which is then connected to another 'Local switch' and a telephone handset icon.
+
+Diagram of Connection type 2: International IP network
+
+Connection type 2: International IP network
+
+![Diagram of Connection type 3: National/international IP network](b8661c6c54f72ecc7ff6cb05e47b2891_img.jpg)
+
+A diagram showing a 'Local switch' connected to a 'National/International IP Network' cloud via 'VOIP' interfaces at both ends. Each 'Local switch' is further connected to a telephone handset icon.
+
+Diagram of Connection type 3: National/international IP network
+
+Connection type 3: National/international IP network
+
+T0207920-99
+
+**Figure 2/E.671 – Reference connections**
+
+## 6 GOS objectives
+
+The target values for the post-selection delay parameter for the above three types of reference connections are given in Table 1.
+
+**Table 1/E.671 – Postselection delays for PSTN/ISDN connections with IP telephony**
+
+| Reference connection                                                     | Normal load |        | High load |        |
+|--------------------------------------------------------------------------|-------------|--------|-----------|--------|
+|                                                                          | Mean        | 95%    | Mean      | 95%    |
+| National IP network<br>(equivalent to E.721 toll)                        | 5.0 s       | 8.0 s  | 7.5 s     | 12.0 s |
+| International IP network                                                 | FFS         | FFS    | FFS       | FFS    |
+| National/international IP network<br>(equivalent to E.721 international) | 8.0 s       | 11.0 s | 12.0 s    | 16.5 s |
+
+FFS For further study
+
+NOTE 1 – The "national IP network" connection is considered equivalent to the E.721 toll connection. The "national/international IP network" connection is considered equivalent to the E.721 international connection. Consistent with E.721, except for mean delay at normal load, all other target values are provisional and require further review.
+
+NOTE 2 – The target values are specified at the normal and high loads, with the loading conditions being specified in the same sense as Recommendation E.500. However, the definitions there may need to be adapted for use in IP-based networks. Also for further study is the application of these loading conditions in a geographically distributed network with non-coincident busy hours.
+
+NOTE 3 – International connections are assumed to include one satellite link.
+
+NOTE 4 – Delays for any required database lookup will need to be added to the above target values.
+
+## 7 History
+
+This is the first issue of Recommendation E.671.
+
+
+
+
+
+# ITU-T RECOMMENDATIONS SERIES
+
+|                 |                                                                                                                                |
+|-----------------|--------------------------------------------------------------------------------------------------------------------------------|
+| Series A        | Organization of the work of the ITU-T                                                                                          |
+| Series B        | Means of expression: definitions, symbols, classification                                                                      |
+| Series C        | General telecommunication statistics                                                                                           |
+| Series D        | General tariff principles                                                                                                      |
+| <b>Series E</b> | <b>Overall network operation, telephone service, service operation and human factors</b>                                       |
+| Series F        | Non-telephone telecommunication services                                                                                       |
+| Series G        | Transmission systems and media, digital systems and networks                                                                   |
+| Series H        | Audiovisual and multimedia systems                                                                                             |
+| Series I        | Integrated services digital network                                                                                            |
+| Series J        | Transmission of television, sound programme and other multimedia signals                                                       |
+| Series K        | Protection against interference                                                                                                |
+| Series L        | Construction, installation and protection of cables and other elements of outside plant                                        |
+| Series M        | TMN and network maintenance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits |
+| Series N        | Maintenance: international sound programme and television transmission circuits                                                |
+| Series O        | Specifications of measuring equipment                                                                                          |
+| Series P        | Telephone transmission quality, telephone installations, local line networks                                                   |
+| Series Q        | Switching and signalling                                                                                                       |
+| Series R        | Telegraph transmission                                                                                                         |
+| Series S        | Telegraph services terminal equipment                                                                                          |
+| Series T        | Terminals for telematic services                                                                                               |
+| Series U        | Telegraph switching                                                                                                            |
+| Series V        | Data communication over the telephone network                                                                                  |
+| Series X        | Data networks and open system communications                                                                                   |
+| Series Y        | Global information infrastructure                                                                                              |
+| Series Z        | Languages and general software aspects for telecommunication systems                                                           |
+
+\*18128\*

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+
+
+![ITU logo](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg)
+
+The logo of the International Telecommunication Union (ITU) features a globe with a lightning bolt striking across it, and the letters 'ITU' superimposed on the globe.
+
+ITU logo
+
+INTERNATIONAL TELECOMMUNICATION UNION
+
+**ITU-T**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+**E.681**
+
+(10/2001)
+
+SERIES E: OVERALL NETWORK OPERATION,  
+TELEPHONE SERVICE, SERVICE OPERATION AND  
+HUMAN FACTORS
+
+Traffic engineering – Traffic engineering for IP-networks
+
+---
+
+**Traffic engineering methods for IP access  
+networks based on hybrid fiber/coax system**
+
+ITU-T Recommendation E.681
+
+---
+
+# ITU-T E-SERIES RECOMMENDATIONS
+
+# OVERALL NETWORK OPERATION, TELEPHONE SERVICE, SERVICE OPERATION AND HUMAN FACTORS
+
+|                                                                                                   |                    |
+|---------------------------------------------------------------------------------------------------|--------------------|
+| INTERNATIONAL OPERATION                                                                           |                    |
+| Definitions                                                                                       | E.100–E.103        |
+| General provisions concerning Administrations                                                     | E.104–E.119        |
+| General provisions concerning users                                                               | E.120–E.139        |
+| Operation of international telephone services                                                     | E.140–E.159        |
+| Numbering plan of the international telephone service                                             | E.160–E.169        |
+| International routing plan                                                                        | E.170–E.179        |
+| Tones in national signalling systems                                                              | E.180–E.189        |
+| Numbering plan of the international telephone service                                             | E.190–E.199        |
+| Maritime mobile service and public land mobile service                                            | E.200–E.229        |
+| OPERATIONAL PROVISIONS RELATING TO CHARGING AND ACCOUNTING IN THE INTERNATIONAL TELEPHONE SERVICE |                    |
+| Charging in the international telephone service                                                   | E.230–E.249        |
+| Measuring and recording call durations for accounting purposes                                    | E.260–E.269        |
+| UTILIZATION OF THE INTERNATIONAL TELEPHONE NETWORK FOR NON-TELEPHONY APPLICATIONS                 |                    |
+| General                                                                                           | E.300–E.319        |
+| Phototelegraphy                                                                                   | E.320–E.329        |
+| ISDN PROVISIONS CONCERNING USERS                                                                  | E.330–E.349        |
+| INTERNATIONAL ROUTING PLAN                                                                        | E.350–E.399        |
+| NETWORK MANAGEMENT                                                                                |                    |
+| International service statistics                                                                  | E.400–E.409        |
+| International network management                                                                  | E.410–E.419        |
+| Checking the quality of the international telephone service                                       | E.420–E.489        |
+| TRAFFIC ENGINEERING                                                                               |                    |
+| Measurement and recording of traffic                                                              | E.490–E.505        |
+| Forecasting of traffic                                                                            | E.506–E.509        |
+| Determination of the number of circuits in manual operation                                       | E.510–E.519        |
+| Determination of the number of circuits in automatic and semi-automatic operation                 | E.520–E.539        |
+| Grade of service                                                                                  | E.540–E.599        |
+| Definitions                                                                                       | E.600–E.649        |
+| <b>Traffic engineering for IP-networks</b>                                                        | <b>E.650–E.699</b> |
+| ISDN traffic engineering                                                                          | E.700–E.749        |
+| Mobile network traffic engineering                                                                | E.750–E.799        |
+| QUALITY OF TELECOMMUNICATION SERVICES: CONCEPTS, MODELS, OBJECTIVES AND DEPENDABILITY PLANNING    |                    |
+| Terms and definitions related to the quality of telecommunication services                        | E.800–E.809        |
+| Models for telecommunication services                                                             | E.810–E.844        |
+| Objectives for quality of service and related concepts of telecommunication services              | E.845–E.859        |
+| Use of quality of service objectives for planning of telecommunication networks                   | E.860–E.879        |
+| Field data collection and evaluation on the performance of equipment, networks and services       | E.880–E.899        |
+
+For further details, please refer to the list of ITU-T Recommendations.
+
+## **ITU-T Recommendation E.681**
+
+# **Traffic engineering methods for IP access networks based on hybrid fiber/coax system**
+
+## **Summary**
+
+This Recommendation describes generic preferred methods for the traffic control and dimensioning of IP-access networks based on hybrid fiber/coax (HFC) system, taking into account the capabilities and limitations of the cable-modem based access technology. The main focus is on the provision over HFC system of IP telephony service in an integrated voice/data environment. Factors affecting system capacity for the support of voice connections are described. Topics discussed include the dimensioning of a single upstream channel, upstream channel pooling, and interoperability between DOCSIS 1.0 and DOCSIS 1.1.
+
+###### **Source**
+
+ITU-T Recommendation E.681 was prepared by ITU-T Study Group 2 (2001-2004) and approved under the WTSA Resolution 1 procedure on 29 October 2001.
+
+# FOREWORD
+
+The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis.
+
+The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics.
+
+The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1.
+
+In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC.
+
+## NOTE
+
+In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+## INTELLECTUAL PROPERTY RIGHTS
+
+ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process.
+
+As of the date of approval of this Recommendation, ITU had received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database.
+
+© ITU 2002
+
+All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU.
+
+## CONTENTS
+
+###### Page
+
+|       |                                                                    |    |
+|-------|--------------------------------------------------------------------|----|
+| 1     | Scope .....                                                        | 1  |
+| 2     | References.....                                                    | 1  |
+| 2.1   | Normative references.....                                          | 1  |
+| 2.2   | Non-normative references .....                                     | 2  |
+| 3     | Definitions .....                                                  | 2  |
+| 4     | Abbreviations.....                                                 | 2  |
+| 5     | Introduction .....                                                 | 2  |
+| 6     | Grade of Service parameters.....                                   | 4  |
+| 7     | Traffic engineering considerations .....                           | 4  |
+| 7.1   | Factors affecting upstream capacity .....                          | 4  |
+| 7.1.1 | Channel characteristics.....                                       | 5  |
+| 7.1.2 | Protocol features.....                                             | 5  |
+| 7.1.3 | Propagation delay .....                                            | 5  |
+| 7.2   | Protocol for upstream transmission .....                           | 5  |
+| 8     | Dimensioning of a single upstream .....                            | 6  |
+| 8.1   | Voice capacity .....                                               | 6  |
+| 8.2   | Available capacity for data.....                                   | 6  |
+| 9     | DOCSIS 1.0 and DOCSIS 1.1 interoperability .....                   | 7  |
+| 10    | Upstream channel pooling .....                                     | 8  |
+| 10.1  | Immediate upstream channel change.....                             | 8  |
+| 10.2  | Voice slot jitter .....                                            | 8  |
+| 10.3  | Assignment algorithms.....                                         | 8  |
+| 11    | History .....                                                      | 10 |
+|       | Appendix I – Example calculation of upstream channel capacity..... | 10 |
+|       | Appendix II – Example of jitter window .....                       | 11 |
+
+
+
+# **Traffic engineering methods for IP access networks based on hybrid fiber/coax system**
+
+# **1 Scope**
+
+This Recommendation describes generic preferred methods for the traffic control and dimensioning of IP-access networks based on hybrid fiber/coax (HFC) system, taking into account the capabilities and limitations of the cable-modem based access technology. It contains relevant traffic principles for the planning, operation, and management of HFC-based IP-access networks so that quality of service (QOS) objectives to customers can be met.
+
+For traffic engineering, this Recommendation assumes that the network is available: that is, it does not consider network equipment in a failure state.
+
+The first release of this Recommendation is only concerned with the provision over HFC system of IP telephony service in an integrated voice/data environment. While the impact of voice service on the capacity available for data is considered, traffic-engineering methods for TCP/IP-supported data services such as web-browsing, email, file transfer, and high-speed data access are for further study. Other services such as video telephony, video-on-demand, are also for further study.
+
+# **2 References**
+
+## **2.1 Normative references**
+
+The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published.
+
+- ITU-T Recommendation E.526 (1993), *Dimensioning a circuit group with multi-slot bearer services and no overflow inputs*.
+- ITU-T Recommendation E.651 (2000), *Reference connections for traffic engineering of IP access networks*.
+- ITU-T Recommendation E.721 (1999), *Network grade of service parameters and target values for circuit-switched services in the evolving ISDN*.
+- ITU-T Recommendation E.726 (2000), *Network grade of service parameters and target values for B-ISDN*.
+- ITU-T Recommendation G.114 (2000), *One-way transmission time*.
+- ITU-T Recommendation G.711 (1988), *Pulse code modulation (PCM) of voice frequencies*.
+- ITU-T Recommendation G.728 (1992), *Coding of speech at 16 kbit/s using low-delay code excited linear prediction*.
+- ITU-T Recommendation J.112 (1998), *Transmission systems for interactive cable television services*.
+
+## 2.2 Non-normative references
+
+The following references are listed here for information:
+
+- DOCSIS 1 Data-Over-Cable Service Interface Specifications, Radio Frequency Interface Specification 1.0, SP-RFI-I05-991105, Cable Television Laboratories, Inc., November 1999.
+- DOCSIS 2 Data-Over-Cable Service Interface Specifications, Radio Frequency Interface Specification 1.1, SP-RFIv1.1-I07-010829, Cable Television Laboratories, Inc., August 2001.
+- DOCSIS 3 Data-Over-Cable Service Interface Specifications, Cable Modem to Customer Premises Equipment Interface Specification, SP-CMCI-I05-001215, Cable Television Laboratories, Inc., December 2000.
+
+# 3 Definitions
+
+This Recommendation defines the following terms:
+
+- 3.1** A **cable modem (CM)** is a modulator-demodulator at subscriber locations intended for use in conveying data communications on a cable television system.
+- 3.2** A **cable modem termination system (CMTS)**, located at the cable television system headend or distribution hub, provides complementary functionality to the cable modems to enable data connectivity to a wide-area network.
+- 3.3** A **fiber node** is a point of interface between a fiber trunk and the coaxial distribution.
+- 3.4** A **hybrid fiber/coax (HFC)** system is a broadband bi-directional shared-media transmission system using fiber trunks between the headend and the fiber nodes, and coaxial distribution from the fiber nodes to the customer locations.
+
+# 4 Abbreviations
+
+This Recommendation uses the following abbreviations:
+
+- CM Cable Modem
+- CMTS Cable Modem Termination System
+- CPE Customer Premises Equipment
+- GoS Grade of Service
+- HFC Hybrid Fiber/Coax system
+- IP Internet Protocol
+- MTA Multi-media Terminal Adapter
+- QoS Quality of Service
+- TCP Transmission Control Protocol
+
+# 5 Introduction
+
+This Recommendation uses the reference architecture of IP access networks based on hybrid fiber/coax systems as specified in 7.1/E.651. For convenience, Figure 7-1/E.651 is reproduced below as Figure 5-1.
+
+![Reference architecture of an HFC-based IP access network diagram](ebff22fb5dd6f50a90e44dca0f82f285_img.jpg)
+
+The diagram illustrates the reference architecture of an HFC-based IP access network. At the top, an 'Edge router' is connected to a 'local IP' network (represented by an oval). The 'local IP' network is further connected to an 'IP core network' (oval) and a 'PSTN/ISDN gateway'. The 'PSTN/ISDN gateway' is connected to a 'PSTN/ISDN' network (oval). Below the 'Edge router' is a 'Cable modem termination system' (CMTS). A 'fiber' link connects the CMTS to a 'Fiber node'. From the 'Fiber node', a 'cable' distribution network branches out to multiple 'Cable modem' units. Each 'Cable modem' is connected to customer premises equipment (CPE), such as a 'phone' via an 'MTA' (Multi-media Terminal Adapter). The entire network structure is enclosed in a dashed box labeled 'HFC-based IP access network' at the bottom right. A small text label 'T0209350-02' is located at the bottom right of the diagram.
+
+Reference architecture of an HFC-based IP access network diagram
+
+T0209350-02
+
+**Figure 5-1/E.681 – Reference architecture of an HFC-based IP access network**
+
+This figure shows an HFC-based IP-access network with cable modems (CMs) located at customer premises connected to a cable modem termination system (CMTS) at the head-end. The HFC distribution plant includes fiber links between a CMTS and a fiber node, with the latter performing optical/electrical conversion. Coaxial cable is used to connect multiple customer premises in close proximity to the fiber node. Customer-premises equipment, such as a personal computer, can interface directly with a CM. An ordinary telephone is usually interfaced through a multi-media terminal adapter (MTA) to a CM. The MTA may be integrated with the CM. Through a managed local IP network and an edge router, an HFC-access network is connected to an IP core network for either Internet access or all-IP end-to-end telephone calls. Connection is also provided via a gateway for interworking with PSTN/ISDN for telephone calls. The edge router may be integrated with the CMTS and routes the traffic over the local IP network. It may also perform traffic policing and, optionally, admission control functions. The local IP network contains all the network elements/servers required for connection management and call processing.
+
+A CMTS and a CM transfer IP traffic by using the *Data-Over-Cable Service Interface Specifications*, Radio Frequency Interface Specification, Version 1.1 [DOCSIS 2]. This specification is commonly referred to as DOCSIS 1.1. An earlier version, DOCSIS 1.0 [DOCSIS 1], was originally developed to support best-effort high-speed data service. Traffic engineering issues related to the interoperability between these two versions is addressed in clause 9.
+
+# 6 Grade of Service parameters
+
+In this clause, GoS parameters that are relevant for traffic engineering purposes are listed. Their definitions and target values are the subject of a future Recommendation.
+
+For IP telephony, the following traffic GoS parameters at the call level are recommended:
+
+- 1) probability of call blocking;
+- 2) post-selection delay;
+- 3) answer-signal delay;
+- 4) call-release delay.
+
+NOTE 1 – These parameters are functionally similar to the corresponding ones specified in ITU-T Recs E.721 and E.726.
+
+NOTE 2 – In the context here, answer-signal delay is functionally equivalent to post pick-up delay. That is, the interval from the time when the terminating phone is picked up (after ringing) to the time when the end-to-end voice path to the originating phone is established. This interval is specified to avoid the "clipped hello".
+
+After call establishment, for information transfer, the term *packet* refers to a packet containing one or more voice samples. In this phase, the following traffic GoS parameters are recommended:
+
+- 1) speech transmission delay (including packetization delay and one-way packet transfer delay);
+- 2) packet delay variation, also referred to as jitter;
+- 3) packet loss (average and burst loss).
+
+NOTE 3 – These parameters are functionally similar to the corresponding cell-level GoS parameters specified in ITU-T Rec. E.726.
+
+# 7 Traffic engineering considerations
+
+In an HFC system, two-way interactivity is accomplished by augmenting a cable-TV broadcast network with a return path in the upstream direction (i.e. a path from the customer to the network). However, due to the relatively small part of the spectrum allocated for upstream use (for compatibility with TV broadcasts) and the noise characteristics therein, the bandwidths available in the two directions are asymmetrical with the upstream bandwidth being much more limited than the downstream. Because of this asymmetry, a CMTS usually associates one downstream channel with multiple (typically up to eight) upstream channels. However, a CM can only access one of these upstream channels at a time for all its communication needs, i.e. to support several (usually up to four) simultaneous voice calls and/or one "always-on" high-speed data connection.
+
+For high-speed data communications, throughput-intensive downloads and file transfers typically occur in the downstream direction, and the upstream is mainly used for the transmission of small packets containing acknowledgements and commands from the users. Unlike data applications, the bidirectional bandwidth requirements of interactive voice communication are inherently symmetrical. Hence, in supporting integrated voice/data services, the bandwidth-limited upstream channels may be the bottleneck.
+
+## 7.1 Factors affecting upstream capacity
+
+The capacity of an upstream channel depends on the physical characteristics and the protocol used for communication. The maximum round-trip propagation delay between a CM and a CMTS also affects the maximum capacity for supporting telephony service. Appendix I contains an example that shows how the following factors affect the upstream capacity for voice connections.
+
+### 7.1.1 Channel characteristics
+
+DOCSIS 1.1 permits operators the flexibility in selecting upstream physical-layer characteristics by providing two modulation formats (QPSK or 16-QAM), a set of five symbol rates, together with a corresponding set of channel widths. The raw bit rate of an upstream channel depends primarily on the channel bandwidth, modulation format, and symbol rate selected for the channel.
+
+### 7.1.2 Protocol features
+
+The number of voice connections that can be supported on a channel depends on the type of codec encoding algorithms, voice packetization interval, the use of payload header suppression, the size of the forward error correction codeword, and the size of a mini-slot.
+
+DOCSIS specifies a mini-slot as a time unit for the purpose of upstream bandwidth allocation. The upstream channel is therefore modelled as a stream of contiguous mini-slots, with each mini-slot representing the time needed for transmission of a fixed number of bytes. Commonly used mini-slot sizes are either 8 or 16 bytes each.
+
+### 7.1.3 Propagation delay
+
+DOCSIS specifies that, once every 10 s, upstream bandwidth be dedicated to allow new CMs to join the network and to perform initial ranging. Ranging is the process for a CM to acquire the correct timing offset such that its transmissions are aligned to the correct mini-slot boundary. Referred to as *initial maintenance*, the bandwidth for this ranging activity requires "a long interval, equivalent to the maximum round-trip propagation delay plus the transmission time of the Ranging Request (RNG-REQ) message". During this interval, voice packets cannot be transmitted. To avoid the impact of this on the packet delay variation, upstream channel bandwidth should not be fully utilized for voice. Hence, the longer this interval, the smaller the upstream capacity for voice.
+
+DOCSIS specifies a maximum spacing of 100 miles (160 km) between a CMTS and the most distant CM, although 15-25 km may be typical. Depending on the ratio of media (fiber to copper) length, media propagation delay varies. Suppose that the media speed equals  $2/3$  of the speed of light in vacuum (see ITU-T Rec. G.114), then the maximum round-trip propagation delay is 1.61 ms.
+
+In practice, cable plants usually operate with shorter distances than the DOCSIS-specified maximum. To get a higher capacity for voice connections, it may be desirable for such cable plants to use a value smaller than the above maximum propagation delay to set the initial maintenance interval.
+
+## 7.2 Protocol for upstream transmission
+
+Access to the mini-slots for upstream transmission by a CM is controlled by the CMTS. A CM can send a packet only after it has requested and obtained from the CMTS a *grant*, i.e. permission to use some number of contiguous mini-slots. Responding to these requests, the CMTS schedules the upstream payload transmissions through successive grants to different CMs. In data communications, each time a CM is ready to send a packet, it requests a grant from the CMTS.
+
+For constant bit rate (CBR) voice communications under DOCSIS 1.1, to minimize overhead, a CMTS automatically provides *unsolicited grants* to a CM for periodic upstream transmission of voice packets for each CBR connection that has been established for the CM. For simplicity, the term *voice slot* refers to a steady stream of periodic unsolicited grants to use succeeding contiguous sequence of mini-slots to transmit the fixed-sized voice packets generated from a CBR connection. Thus, a voice slot is allocated to a CM for each CBR connection it has established.
+
+# 8 Dimensioning of a single upstream
+
+The bandwidth of an upstream channel is shared among the payload traffic for both IP telephony and high-speed data, the overhead traffic from telephony signalling and DOCSIS maintenance activities, as well as traffic arising from contention for upstream transmission requests.
+
+In this clause, it is assumed that each CM is configured *statically* to use a particular upstream channel at provisioning time (e.g. at installation or power up). Hence, each upstream channel is engineered separately.
+
+## 8.1 Voice capacity
+
+For a conservative estimate of the capacity of an individual upstream to support voice connections, the Erlang-B formula can be used:
+
+$$\Pi = (a^n / n!) / \sum_{k=0}^n (a^k / k!)$$
+
+where  $\Pi$  is call congestion (or probability of call blocking),  $a$  is the offered load, and  $n$  is the maximum number of voice connections that can be supported by an upstream channel. This number  $n$  can be determined by using a method similar to that in Appendix I.
+
+To account for finite-source effect, the Engset formula for call congestion can be used:
+
+$$\Pi = \left[ \binom{m-1}{n} \hat{a}^n \right] / \left[ \sum_{k=0}^n \binom{m-1}{k} \hat{a}^k \right]$$
+
+where  $m$  is the number of traffic sources, and  $\hat{a}$  is the average offered load per idle source. Let  $\alpha = a/m$  be the average offered load per source. The relationship  $\hat{a} = \alpha / [1 - \alpha(1 - \Pi)] \approx \alpha / (1 - \alpha)$  can be used to estimate the quantity  $\hat{a}$ , when  $\Pi \ll 1$ .
+
+When the system supports a mixture of encoding schemes (e.g. both ITU-T Recs G.711 and G.728), different voice calls may require different data rates. In this case, the methods of ITU-T Rec. E.526 can be used for dimensioning.
+
+## 8.2 Available capacity for data
+
+The upstream capacity for data traffic depends largely on the degree of bandwidth sharing between voice and data services. In the hard partition scheme where voice and data use separate bandwidth regions with no sharing, data traffic gets only what is allocated in its bandwidth region. Any sharing schemes will allow higher effective average data bandwidth compared to the hard partition scheme [CS01, L01].
+
+To facilitate voice/data sharing, it is assumed for traffic engineering purposes that the sequence of mini-slots in an upstream channel is partitioned into *frames*, the length of each being the packetization time for voice sampling. For most packet telephony applications over cable-access systems, this time is typically 10 ms to minimize speech transmission delays. Within each frame, the set of mini-slots is further partitioned into two *fixed* regions. One is designated for data service only, and accommodates variable-sized data packets. This is referred to as a *data-only region*. The other one, referred to as a *voice region*, is for both voice and data services, with voice having priority over data. Voice packets are fixed in size.
+
+To estimate the *maximum* amount of idle capacity in the voice region that is available for use by data service, note that the probability for  $j$  busy voice slots,  $P_j$  is:
+
+$$P_j = \left[ \binom{m}{j} \hat{a}^j \right] / \left[ \sum_{k=0}^n \binom{m}{k} \hat{a}^k \right] \quad (j = 0, 1, \dots, n)$$
+
+The probability for at least  $i$  idle voice slots in the voice region is  $\sum_{j=0}^{n-i} P_j$ . This idle capacity is available for use by data, in addition to the bandwidth in the data-only region.
+
+![Figure 8-1/E.681: A diagram showing a voice region with two sections of contiguous idle slots. The voice region is divided into four segments: busy slots, idle slots, busy slots, and idle slots. The data-only region is shown to the right. A double-headed arrow below the voice region segments indicates its extent. The label 'T0209360-02' is in the top right corner.](4e4be0bd8b235167902f2c03e41da651_img.jpg)
+
+Figure 8-1/E.681: A diagram showing a voice region with two sections of contiguous idle slots. The voice region is divided into four segments: busy slots, idle slots, busy slots, and idle slots. The data-only region is shown to the right. A double-headed arrow below the voice region segments indicates its extent. The label 'T0209360-02' is in the top right corner.
+
+**Figure 8-1/E.681 – A voice region with two sections of contiguous idle slots (i.e. two "holes")**
+
+Over time, as voice connections are established and cleared, "holes," or sections of contiguous idle voice slots, are created in the channel bandwidth as shown in Figure 8-1. To make full use of this idle capacity in the voice region, DOCSIS 1.1 specifies a data packet fragmentation procedure whereby data packets are fragmented to fill in these holes. A penalty for using this procedure is the extra 16-byte per-fragment overhead that is required to convey fragmentation and reassembly information. In comparison, note that the size of a voice slot under G.711 encoding is about 135 bytes (see Appendix I).
+
+![Figure 8-2/E.681: A diagram showing a voice region with a single section of contiguous idle slots. The voice region is divided into two segments: busy slots and idle slots. The data-only region is shown to the right. A double-headed arrow below the voice region segments indicates its extent. The label 'T0209370-02' is in the top right corner.](cab0834804fb031b43865554cc8d06ab_img.jpg)
+
+Figure 8-2/E.681: A diagram showing a voice region with a single section of contiguous idle slots. The voice region is divided into two segments: busy slots and idle slots. The data-only region is shown to the right. A double-headed arrow below the voice region segments indicates its extent. The label 'T0209370-02' is in the top right corner.
+
+**Figure 8-2/E.681 – A voice region with a single section of contiguous idle slots**
+
+It is possible to reduce the need for data packet fragmentation by jittering some of the busy voice slots away from the data region as shown in Figure 8-2. By creating the largest possible sequence of contiguous idle voice slots for data transmission, efficiency is improved. However, such jittering of any voice slots assigned to voice connections will introduce additional packet delay variation. To minimize speech transmission delay, a budget of about 2 to 3 ms for packet delay variation is typically allocated to the CMTS. Hence, it is desirable to avoid the jittering of any assigned voice slots as much as possible.
+
+In practice, jittering of busy voice slots to close holes is not always necessary. This is because the holes can be used for the transmission of small control packets such as for maintenance and contention for transmission requests. To estimate the capacity available for data with assigned voice slots left in-place without closing holes, the model presented in [L01] can be used.
+
+# 9 DOCSIS 1.0 and DOCSIS 1.1 interoperability
+
+DOCSIS 1.0 was originally developed to support best-effort high-speed data service over a cable-based access system. DOCSIS 1.1, a second-generation protocol, enhances upon DOCSIS 1.0 by providing additional functionality so that the performance requirements of delay/jitter sensitive traffic, such as IP telephony, can be met. In particular, this includes protocol features such as unsolicited grant service (see 7.2), data packet fragmentation (see 8.2), and payload header suppression.
+
+To maintain interoperability, a DOCSIS 1.1 CMTS must be backward compatible with a DOCSIS 1.0 CM. Since DOCSIS 1.0 CMs generally do not support packet fragmentation, a DOCSIS 1.1 CMTS must therefore not attempt to fragment the packet transmissions from a DOCSIS 1.0 CM. As a result, there may potentially be some impact on the quality of service for
+
+real-time communication needs of DOCSIS 1.1 CMs, when both DOCSIS 1.0 and DOCSIS 1.1 CMs are provisioned to share the same upstream channel. To mitigate this impact, the *packed upward* voice slot assignment algorithm described in [L01] may be used. Also, given a number of DOCSIS 1.0 CMs to be supported on an upstream channel, there is an upper limit to the number of voice sources that can be supported on the same channel, or vice versa, as shown in [L01].
+
+# 10 Upstream channel pooling
+
+Since the bandwidth of an upstream channel is limited, the number of CMs that can be supported statically by a given channel is small. To increase the overall total number of CMs that can be supported by a CMTS, i.e. to increase the utilization of the upstream channels, it is necessary to pool these channels together for use by any CM. Thus, in addition to provisioning a CM initially to use a particular channel, a CMTS needs to be capable of assigning CMs dynamically to different channels, based on up-to-date traffic conditions.
+
+## 10.1 Immediate upstream channel change
+
+According to DOCSIS 1.1, when the CMTS determines to move a CM from the currently assigned upstream channel to another, it sends to the CM an Upstream Channel Change Request (UCC-REQ) message. In response, the CM transmits an Upstream Channel Change Response (UCC-RSP) message on the currently assigned channel to signal its readiness to use the new channel. After switching to the new channel, the CM typically performs maintenance functions to make any necessary adjustments to the timing, power, or frequency used. This process is referred to as *re-ranging*.
+
+However, to minimize disruption (e.g. to prevent packet loss) to calls in progress on the currently assigned channel, the CM should be able to use the new channel directly without performing the time-consuming re-ranging. Such a short-cut procedure is referred to as an *Immediate Upstream Channel Change (IUCC)*. To achieve this, the CM must know about the operating characteristics of the new channel. At periodic intervals (maximum 2 s), the CMTS transmits to all CMs information about each active upstream channel via an Upstream Channel Descriptor (UCD) message. A CM should cache the UCD information regularly to avoid re-ranging in switching channels. If a CM does not cache the UCD information (e.g. due to a lack of memory), it is recommended that the CMTS should send a unicast message to the CM right after the UCC-REQ message. This is so that the CM can obtain immediately the operating characteristics of the new channel.
+
+## 10.2 Voice slot jitter
+
+Jitter, also referred to as packet delay variation, is the deviation, measured in units of time, from the ideal or anticipated time of receipt of each packet. Voice slot jitter becomes a problem and needs to be controlled when an IUCC is performed. This is because when an IUCC is to be made for a CM, the relative voice slot positions assigned to the CM for existing connections must still be maintained within a maximum tolerated jitter interval between the current and new upstream channels. To meet the jitter constraint, the concept of a *jitter window* is used to define a set of contiguous voice slots in the voice region with acceptable jitter. To keep jitter small, jitter window size must be small. Appendix II provides an example and further discussion on the use of jitter windows.
+
+## 10.3 Assignment algorithms
+
+A CMTS assigns upstream channels and idle voice slots to CMs, on a call-by-call basis, in response to their requests for call establishments. A CMTS performs channel assignments for a CM on two occasions. Either:
+
+- 1) the first call request from the CM; or
+
+- 2) subsequent call requests whenever all the voice slots in the voice region of the channel currently assigned to the CM are occupied, thereby necessitating the IUCC procedure to be performed.
+
+In either case, a channel is *assignable* only if it can accommodate the request, i.e. there are enough idle voice slots for any established calls plus the new call, all within the jitter constraint. When an IUCC needs to be performed, this means that the following two conditions must be satisfied. First, the number of idle voice slots in each jitter window in the new channel must be no less than the number of voice slots allocated to the CM in the corresponding jitter window in the currently assigned channel. Second, at least one of the jitter windows in the new channel has room to accommodate the new call in addition to existing calls.
+
+In selecting a channel for assignment, a CMTS first searches all the channels under its control to find the ones that meet the above assignment criterion. Suppose that a CMTS has  $c$  upstream channels. Typically,  $c$  is no more than eight. Assuming that the channels are numbered consecutively and identified as 1 through  $c$ . The CMTS can conduct the search in one of two ways:
+
+- 1) *Search in opposite directions*, i.e. upward from channel 1 for the first call from a CM, downward from channel  $c$  for a subsequent IUCC; or vice versa.
+- 2) *Search in the same direction*, i.e. upward from channel 1 (or downward from channel  $c$ ) for both the first call from a CM and a subsequent IUCC.
+
+By using one of these search procedures, the CMTS marks a subset of the  $c$  channels that meets the assignment criterion. If this subset is empty, the new call is blocked.
+
+Assuming a successful search, the CMTS selects one channel out of the marked subset for assignment to the CM with a new call. One of the following procedures may be used:
+
+- 1) *Packed with first fit*: Assign the first channel in the specified search direction. For example, if the search upward procedure is used, then the lowest channel that meets the assignment criterion is selected.
+- 2) *Minimally packed*: Assign a channel with the minimum number of idle voice slots, tie breaking by the specified search direction. Thus, suppose there are multiple channels that meet the assignment criterion and have the same minimum number idle voice slots. If the search upward procedure is used, then the lowest such channel is selected.
+- 3) *Maximally spread*: Assign a channel with the maximum number of idle voice slots, tie breaking by the specified search direction.
+- 4) *Random*: Assign a channel probabilistically.
+
+These four procedures can be combined in different ways. For example, the "packed with first fit" procedure may be used for selecting a channel for the new first call from a CM, while the "maximally spread" procedure for IUCCs in new subsequent calls from the same CM.
+
+After the selection of a channel for assignment, the CMTS does the following. If an IUCC is involved, then all existing voice connections established on the currently assigned channel for the CM are first moved to the new channel. In this move, the relationship of jitter windows in the current and new channels is preserved. Thus, existing voice connections assigned to one jitter window in the currently assigned channel are maintained in the same jitter window in the newly selected channel. After moving all existing connections in this manner, an idle voice slot in the new channel is selected and assigned to the new call. Of course, in the case of a new first call from the CM, IUCC is not needed and the CMTS simply selects an idle voice slot in the channel and assigns it to the CM for the new call. Assuming that the voice slots in the voice region of a channel are numbered consecutively and identified as such, one of the following procedures can be used for the selection of an idle voice slot:
+
+- 1) *Packed*: Select the lowest (or highest) idle voice slot.
+- 2) *Random*: first select randomly a jitter window with at least one idle voice slot and then select the lowest (or highest) idle voice slot in the selected jitter window.
+
+For a given maximum jitter tolerance, the different algorithms achieve different blocking probabilities [L00]. The maximally spread and random algorithms tend to give more favorable performance results.
+
+# 11 History
+
+This is the first issue of ITU-T Rec. E.681.
+
+# Bibliography
+
+- [CS01] CHOUDHURY (G.L.), SEGAL (M.): Cable Infrastructure to Carry Voice and Data – Performance Analysis, Traffic Engineering and Cable Head-end Node Design Design, *Proc. 14th ITC Specialists Seminar on Access Networks and Systems*, Girona, Spain, 25-27 April 2001.
+- [L00] LAI (W.S.): Upstream Bandwidth Allocation for Packet Telephony in Hybrid Fiber-Coax Systems, *Proc. 2000 Symposium on Performance Evaluation of Computer and Telecommunication Systems (SPECTS'2000)*, Vancouver, Canada, 16-20 July 2000, pp. 96-100. (Sponsored by the Society for Computer Simulation International.)
+- [L01] LAI (W.S.): DOCSIS-Based Cable Networks: Impact of Large Data Packets on Upstream Capacity, *Proc. 14th ITC Specialists Seminar on Access Networks and Systems*, Girona, Spain, 25-27 April 2001, pp. 57-67.
+
+# Appendix I
+
+### Example calculation of upstream channel capacity
+
+As an example, the following is assumed:
+
+- 1) *Channel characteristics*: A 3.2 MHz upstream channel operating with QPSK at a symbol rate of 2560 ksymb/s, resulting in a 5.12 Mbit/s channel. This is the raw bandwidth for upstream transmission.
+- 2) *Protocol features*: G.711 encoding at 10 ms packetization interval with payload header suppression.
+
+In this case, a voice packet has a voice payload of 80 bytes. Including the overheads in various protocol layers and using the payload header suppression feature of DOCSIS 1.1, a voice packet may come up to 135 bytes in length. For 8-byte mini-slots, a voice slot will require 17 mini-slots, at a rate of 108.8 kbit/s. A 5.12 Mbit/s channel then yields a maximum of 47 connections, when the full channel bandwidth is used to support voice only. Similar calculations show that there are 44 connections for 16-byte mini-slot at 115.2 kbit/s. (The use of lower bit rate encoding schemes such as G.728 and others will give a higher number of connections.)
+
+- 3) *Propagation delay*: Transmission time for the DOCSIS Ranging Request (RNG-REQ) message at 5.12 Mbit/s is 0.1 ms. Together with the maximum round-trip propagation delay of 1.61 ms, there is a maximum total of 1.71 ms.
+
+For a 10-ms packetization interval, this means that 17.1% of the upstream bandwidth is needed for this purpose. As a result, in a pure-voice environment, the per-channel maximum allowable voice capacity is  $(100\% - 17.1\%) 5.12 \text{ Mbit/s} = 4.24 \text{ Mbit/s}$ . For G.711 encoding with payload header suppression, this translates to a maximum of 38 connections for 8-byte mini-slot at 108.8 kbit/s, or 36 connections for 16-byte mini-slot at 115.2 kbit/s.
+
+- 4) In an integrated voice/data environment, the maximum allowable voice capacity is further reduced by the amount of bandwidth that needs to be dedicated for the support of data services. For example, when voice can use only up to 60% of the channel bandwidth, then for the above two scenarios, the corresponding maxima are 28 and 26 voice connections, respectively.
+
+Since initial maintenance is a low-level activity, its bandwidth is derived from the data bandwidth in this case.
+
+## Appendix II
+
+### Example of jitter window
+
+As an example, Figure II.1 shows a 10-ms frame with a 6.6-ms voice region followed by a 3.4-ms data-only region. It illustrates a typical scenario whereby the bandwidth in a frame is split in a ratio of approximately 2:1, for sharing between voice and data services. The voice region has fifteen voice slots, which is an odd number. The sizes of the two non-overlapping jitter windows are approximately equal, with seven voice slots in the lower window and eight in the upper window. The duration of the lower window is  $6.6 \times (7/15) = 3.08 \text{ ms}$ , while that of the upper window is  $6.6 \times (8/15) = 3.52 \text{ ms}$ .
+
+By splitting the voice region into two approximately equal non-overlapping windows, and maintaining calls within the same jitter window in an IUCC procedure, jitter is limited to the duration of the jitter window. This duration is smaller than that of either the voice region or the frame. Furthermore, by arranging the jitter windows to be both non-overlapping and collectively covering the whole voice region, jitter is maximally reduced while access by a CM to channel bandwidth is maximized (and so call blocking is minimized). Also, all CMs will use the same set of jitter windows, hence simplifying system management.
+
+![Figure II.1/E.681 – Example frame structure with two jitter windows. The diagram shows a 10 ms frame divided into a 6.6 ms voice region and a 3.4 ms data-only region. The voice region is further divided into two jitter windows: a lower jitter window (7 time slots, 3.08 ms) and an upper jitter window (8 time slots, 3.52 ms). The data-only region contains mini-slots with bandwidth equivalent to approximately 8 time slots.](36117e9cb27c58484cd8d3e5f9dc7ac3_img.jpg)
+
+The diagram illustrates a 10 ms frame structure. At the top, a horizontal line with arrows at both ends is labeled "frame (10 ms)". Below this, another horizontal line with arrows at both ends is labeled "voice region (6.6 ms)" and "data-only region (3.4 ms)". A vertical dashed line separates the voice region from the data-only region. Below the voice region, a horizontal line is divided into 15 equal segments representing time slots. The first 7 segments are labeled "lower jitter window (7 time slots) 3.08 ms". The next 8 segments are labeled "upper jitter window (8 time slots) 3.52 ms". Below the data-only region, a horizontal line is divided into 8 equal segments, labeled "mini-slots with bandwidth equivalent to approximately 8 time slots". The label "T0209380-02" is located in the bottom right corner of the diagram area.
+
+Figure II.1/E.681 – Example frame structure with two jitter windows. The diagram shows a 10 ms frame divided into a 6.6 ms voice region and a 3.4 ms data-only region. The voice region is further divided into two jitter windows: a lower jitter window (7 time slots, 3.08 ms) and an upper jitter window (8 time slots, 3.52 ms). The data-only region contains mini-slots with bandwidth equivalent to approximately 8 time slots.
+
+Figure II.1/E.681 – Example frame structure with two jitter windows
+
+
+
+
+
+# SERIES OF ITU-T RECOMMENDATIONS
+
+|                 |                                                                                                                                |
+|-----------------|--------------------------------------------------------------------------------------------------------------------------------|
+| Series A        | Organization of the work of ITU-T                                                                                              |
+| Series B        | Means of expression: definitions, symbols, classification                                                                      |
+| Series C        | General telecommunication statistics                                                                                           |
+| Series D        | General tariff principles                                                                                                      |
+| <b>Series E</b> | <b>Overall network operation, telephone service, service operation and human factors</b>                                       |
+| Series F        | Non-telephone telecommunication services                                                                                       |
+| Series G        | Transmission systems and media, digital systems and networks                                                                   |
+| Series H        | Audiovisual and multimedia systems                                                                                             |
+| Series I        | Integrated services digital network                                                                                            |
+| Series J        | Cable networks and transmission of television, sound programme and other multimedia signals                                    |
+| Series K        | Protection against interference                                                                                                |
+| Series L        | Construction, installation and protection of cables and other elements of outside plant                                        |
+| Series M        | TMN and network maintenance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits |
+| Series N        | Maintenance: international sound programme and television transmission circuits                                                |
+| Series O        | Specifications of measuring equipment                                                                                          |
+| Series P        | Telephone transmission quality, telephone installations, local line networks                                                   |
+| Series Q        | Switching and signalling                                                                                                       |
+| Series R        | Telegraph transmission                                                                                                         |
+| Series S        | Telegraph services terminal equipment                                                                                          |
+| Series T        | Terminals for telematic services                                                                                               |
+| Series U        | Telegraph switching                                                                                                            |
+| Series V        | Data communication over the telephone network                                                                                  |
+| Series X        | Data networks and open system communications                                                                                   |
+| Series Y        | Global information infrastructure and Internet protocol aspects                                                                |
+| Series Z        | Languages and general software aspects for telecommunication systems                                                           |

marked/E/T-REC-E.760-200003-I_PDF-E/raw.md

@@ -0,0 +1,540 @@
+
+
+![ITU logo](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg)
+
+The logo of the International Telecommunication Union (ITU) features the letters 'ITU' in a bold, sans-serif font, superimposed on a stylized globe with latitude and longitude lines. A lightning bolt symbol is positioned to the right of the globe.
+
+ITU logo
+
+INTERNATIONAL TELECOMMUNICATION UNION
+
+**ITU-T**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+**E.760**
+
+(03/2000)
+
+SERIES E: OVERALL NETWORK OPERATION,  
+TELEPHONE SERVICE, SERVICE OPERATION AND  
+HUMAN FACTORS
+
+Quality of service, network management and traffic  
+engineering – Traffic engineering – Mobile network traffic  
+engineering
+
+# --- **Terminal mobility traffic modelling**
+
+ITU-T Recommendation E.760
+
+(Formerly CCITT Recommendation)
+
+---
+
+## ITU-T E-SERIES RECOMMENDATIONS **OVERALL NETWORK OPERATION, TELEPHONE SERVICE, SERVICE OPERATION AND HUMAN FACTORS**
+
+## **OPERATION, NUMBERING, ROUTING AND MOBILE SERVICES**
+
+## **INTERNATIONAL OPERATION**
+
+|                                                        |             |
+|--------------------------------------------------------|-------------|
+| Definitions                                            | E.100–E.103 |
+| General provisions concerning Administrations          | E.104–E.119 |
+| General provisions concerning users                    | E.120–E.139 |
+| Operation of international telephone services          | E.140–E.159 |
+| Numbering plan of the international telephone service  | E.160–E.169 |
+| International routing plan                             | E.170–E.179 |
+| Tones in national signalling systems                   | E.180–E.189 |
+| Numbering plan of the international telephone service  | E.190–E.199 |
+| Maritime mobile service and public land mobile service | E.200–E.229 |
+
+## **OPERATIONAL PROVISIONS RELATING TO CHARGING AND ACCOUNTING IN THE INTERNATIONAL TELEPHONE SERVICE**
+
+|                                                                |             |
+|----------------------------------------------------------------|-------------|
+| Charging in the international telephone service                | E.230–E.249 |
+| Measuring and recording call durations for accounting purposes | E.260–E.269 |
+
+## **UTILIZATION OF THE INTERNATIONAL TELEPHONE NETWORK FOR NON-TELEPHONY APPLICATIONS**
+
+|                 |             |
+|-----------------|-------------|
+| General         | E.300–E.319 |
+| Phototelegraphy | E.320–E.329 |
+
+## **ISDN PROVISIONS CONCERNING USERS**
+
+|                            |             |
+|----------------------------|-------------|
+| International routing plan | E.350–E.399 |
+|----------------------------|-------------|
+
+## **QUALITY OF SERVICE, NETWORK MANAGEMENT AND TRAFFIC ENGINEERING**
+
+## **NETWORK MANAGEMENT**
+
+|                                                             |             |
+|-------------------------------------------------------------|-------------|
+| International service statistics                            | E.400–E.409 |
+| International network management                            | E.410–E.419 |
+| Checking the quality of the international telephone service | E.420–E.489 |
+
+## **TRAFFIC ENGINEERING**
+
+|                                                                                   |             |
+|-----------------------------------------------------------------------------------|-------------|
+| Measurement and recording of traffic                                              | E.490–E.505 |
+| Forecasting of traffic                                                            | E.506–E.509 |
+| Determination of the number of circuits in manual operation                       | E.510–E.519 |
+| Determination of the number of circuits in automatic and semi-automatic operation | E.520–E.539 |
+| Grade of service                                                                  | E.540–E.599 |
+| Definitions                                                                       | E.600–E.699 |
+| ISDN traffic engineering                                                          | E.700–E.749 |
+
+|                                           |                    |
+|-------------------------------------------|--------------------|
+| <b>Mobile network traffic engineering</b> | <b>E.750–E.799</b> |
+|-------------------------------------------|--------------------|
+
+## **QUALITY OF TELECOMMUNICATION SERVICES: CONCEPTS, MODELS, OBJECTIVES AND DEPENDABILITY PLANNING**
+
+|                                                                                             |             |
+|---------------------------------------------------------------------------------------------|-------------|
+| Terms and definitions related to the quality of telecommunication services                  | E.800–E.809 |
+| Models for telecommunication services                                                       | E.810–E.844 |
+| Objectives for quality of service and related concepts of telecommunication services        | E.845–E.859 |
+| Use of quality of service objectives for planning of telecommunication networks             | E.860–E.879 |
+| Field data collection and evaluation on the performance of equipment, networks and services | E.880–E.899 |
+
+# **TERMINAL MOBILITY TRAFFIC MODELLING**
+
+## **Summary**
+
+Terminal mobility traffic modelling for land terrestrial or satellite-based mobile systems (including cellular, cordless, paging and IMT-2000) presented in this Recommendation is intended to characterize the mobile user traffic demand associated with mobile services. This demand has significance for both the user and the signalling plane.
+
+### **Source**
+
+ITU-T Recommendation E.760 was prepared by ITU-T Study Group 2 (1997-2000) and was approved under the WTSC Resolution No. 1 procedure on 13 March 2000.
+
+## FOREWORD
+
+ITU (International Telecommunication Union) is the United Nations Specialized Agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the ITU. The ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis.
+
+The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics.
+
+The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Resolution No. 1.
+
+In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC.
+
+### NOTE
+
+In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+## INTELLECTUAL PROPERTY RIGHTS
+
+The ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. The ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process.
+
+As of the date of approval of this Recommendation, the ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database.
+
+© ITU 2000
+
+All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU.
+
+## CONTENTS
+
+|                                                                                                                                                              | Page |
+|--------------------------------------------------------------------------------------------------------------------------------------------------------------|------|
+| 1 Objective and scope .....                                                                                                                                  | 1    |
+| 2 Related Recommendations .....                                                                                                                              | 2    |
+| 3 Definitions .....                                                                                                                                          | 2    |
+| 4 Abbreviations.....                                                                                                                                         | 3    |
+| 5 Introduction.....                                                                                                                                          | 3    |
+| 6 Estimation of traffic demand for cellular networks .....                                                                                                   | 4    |
+| 6.1 Rationale .....                                                                                                                                          | 4    |
+| 6.2 Methodology .....                                                                                                                                        | 5    |
+| 6.3 Upgrading of the procedure for estimating the traffic demand.....                                                                                        | 6    |
+| 7 Mobility modelling and impact on signalling traffic .....                                                                                                  | 6    |
+| 8 History.....                                                                                                                                               | 6    |
+| Appendix I – Estimating the traffic demand .....                                                                                                             | 7    |
+| Appendix II – An example methodology for modelling the handover rate between cells in cellular, terrestrial-based mobile systems .....                       | 9    |
+| Appendix III – An example methodology for modelling the location registration and location updating rate in cellular, terrestrial-based mobile systems ..... | 12   |
+
+
+
+# TERMINAL MOBILITY TRAFFIC MODELLING
+
+(Geneva, 2000)
+
+## 1 Objective and scope
+
+1.1 Terminal mobility traffic modelling for land terrestrial or satellite-based mobile systems (including cellular, cordless, paging and IMT-2000) presented in this Recommendation is intended to characterize the mobile user traffic demand associated with mobile services. This demand has significance for both the user and the signalling plane.
+
+1.2 The geographical scope of traffic demand and terminal mobility modelling ranges from metropolitan to international areas. As an example, Figure 1 shows the scope of Recommendation E.760 for the case of terrestrial-based cellular networks under the assumption of separated fixed and mobile networks (see Recommendation E.751). The figure indicates two teletraffic interfaces at which traffic demand has to be characterized for traffic engineering purposes. One traffic demand relates to the radio interface; the other is associated with the characterization of mobile related traffic which insists on the fixed network. This latter characterization is intended for the purposes of dimensioning fixed network resources used for supporting mobile services.
+
+![Diagram illustrating the scope of traffic demand characterization for cellular networks, showing the interconnection of fixed and mobile networks across metropolitan, wide/national, and international areas.](0236eff05bcb8f3a343ea7933aaa306b_img.jpg)
+
+The diagram illustrates the network architecture for traffic modeling. At the top, an 'International area' is shown with two 'ISC' (Inter-Switching Centre) nodes connected to an 'International fixed network'. Below this, a 'National fixed network' contains several 'LE/TE' (Local Exchange/Terminal Exchange) nodes. In the middle section, a 'Wide/national area' and a 'Metropolitan area' are depicted. The 'Metropolitan area' contains 'other LE/TEs' and 'other MSCs' (Mobile Switching Centres). The 'Wide/national area' consists of a series of 'MSC' nodes, some of which are connected to 'MMF' (Mobility Management Function) blocks. Each 'MSC' is further connected to multiple 'BS' (Base Station) nodes. At the bottom, a 'Land mobile network' is shown with two 'MT' (Mobile Terminal) units. A dashed line connects the two 'MT' units, representing a mobile-to-mobile communication path. Two 'Teletraffic interface' points are indicated: one at the radio interface between the 'BS' and 'MT', and another at the interface between the 'LE/TE' and the 'MSC'.
+
+Diagram illustrating the scope of traffic demand characterization for cellular networks, showing the interconnection of fixed and mobile networks across metropolitan, wide/national, and international areas.
+
+NOTE – The figure shows the interconnection of (separated) fixed and mobile networks, Recommendation E.220, and the allocation of mobility management functions (MMF) within the mobile network, as is typically the case with second generation mobile systems (e.g. GSM). Depending on the actual implementations and traffic requirements, the MSC (Mobile Switching Centre) can be connected with the fixed network at the LE (Local Exchange) or TE (Terminal Exchange) level. This is succinctly indicated through the combination LE/TE. In fact, the allocation of MMF has a range of possible options including the arrangements resulting from integrated mobile and fixed network, Recommendation E.751.
+
+**Figure 1/E.760 – Scope of traffic demand characterization for cellular networks (separated mobile and fixed network, mobile-to-mobile communication)**
+
+**1.3** This Recommendation addresses traffic demand modelling related to land mobile systems and traffic demand associated with the radio interface. Modelling of traffic demand insising on the fixed network is for further study. Finally, traffic modelling for other systems, e.g. cordless and paging systems, is also for further study.
+
+## **2 Related Recommendations**
+
+The following Recommendations contain material that is either relevant to or provides background for this Recommendation.
+
+- CCITT Recommendation E.201 (1991), *Reference Recommendation for mobile services.*
+- CCITT Recommendation E.202 (1992), *Network operational principles for future public mobile systems and services.*
+- ITU-T Recommendation E.220 (1996), *Interconnection of public land mobile networks (PLMN).*
+- ITU-T Recommendation E.600 (1993), *Terms and definitions of traffic engineering.*
+- CCITT Recommendation E.711 (1992), *User demand modelling.*
+- CCITT Recommendation E.712 (1992), *User plane traffic modelling.*
+- CCITT Recommendation E.713 (1992), *Control plane traffic modelling.*
+- ITU-T Recommendation E.751 (1996), *Reference connections for traffic engineering of land mobile networks.*
+- ITU-T Recommendation E.771 (1996), *Network grade of service parameters and target values for circuit switched land mobile services.*
+- ITU-T Recommendation E.773 (1996), *Maritime and aeronautical mobile grade of service concept.*
+- ITU-T Recommendation F.115 (1995), *Service objectives and principles for future public land mobile telecommunication systems.*
+- ITU-R Recommendation M.1034-1 (1997), *Requirements for the radio interface(s) for International Mobile Telecommunications-2000 (IMT-2000).*
+
+## **3 Definitions**
+
+**3.1** For the purposes of this Recommendation, definitions provided in Recommendations E.600, E.751 and E.771 will be applicable.
+
+Additional definitions used in this Recommendation are as follows:
+
+**3.1.1 Network attachment point:** The physical location in the network used for terminating the routing of calls to/from the end-user system (terminal identifier). In the case where the segment spanned between the physical termination of the end-user system and the network access point has additional functions to the sheer electrical connection, access network functionality is required for user information and signalling transfer.
+
+## 4 Abbreviations
+
+This Recommendation uses the following abbreviations:
+
+|          |                                              |
+|----------|----------------------------------------------|
+| BS       | Base Station                                 |
+| GSM      | Global System for Mobile communications      |
+| IMT-2000 | International Mobile Telecommunications-2000 |
+| ISC      | International Switching Centre               |
+| LE       | Local Exchange                               |
+| MMF      | Mobility Management Function                 |
+| MSC      | Mobile Switching Centre                      |
+| MT       | Mobile Terminal                              |
+| TE       | Terminal Exchange                            |
+
+## 5 Introduction
+
+**5.1** One unique feature characterizing the traffic demand of mobile users is spatial volatility. This relates to the changing geographical origin (or destination) of traffic associated with the same mobile user once a connection has been established (in-call mobility) and is due to user terminal mobility. Another aspect of terminal mobility relates to users changing their geographical location in-between calls (inter-call mobility): this results in a dynamic association between the identifier of the actual terminal device used by a user and the network attachment point for calls originated by (or destined to) the same user.
+
+**5.2** As a consequence of traffic volatility combined with traffic source activity and spectrum reuse typical of cellular systems, the radio channel quality is space- and time-dependent and appropriate actions, e.g. handover or combining, may be performed by the system to help maintain a minimum level for the quality of service. Although these actions may result in a consumption of the same resources utilized for accommodating call demands, the characterization of the related processes depends, among others, on how radio resources are engineered and managed. For this reason the characterization of these processes is covered in Recommendations of the E.750-series especially concerned with traffic dimensioning methods for land mobile systems.
+
+**5.3** One way of capturing traffic volatility for engineering purposes is via a distribution in space and time of the user population over a considered area. This distribution shall then be mapped onto user demand, while retaining the space and time dependence.
+
+Factors affecting this distribution include:
+
+- environment type (indoor/outdoor, business, residential, etc.);
+- geography of and mobility patterns on the considered area (open space, urban layout, city precinct, etc.);
+- mobility characteristics (pedestrian/car mobility behaviour, speed, etc.);
+- service penetration.
+
+**5.4** Although efficient use of the available spectrum might be attained by using various forms of dynamic bandwidth allocation to cope with the volatility of mobile traffic, most existing systems are dimensioned according to a worst-case approach with relationship to a static population of users. This implies that the highest traffic demand insisting on a given area (usually corresponding to a cell) is estimated and the number of radio channels related to that area is determined accordingly. The estimate is based on such data as density of residing population, service penetration, geographic characteristics, traffic per subscriber, etc.
+
+This Recommendation is concerned with the worst-case approach as defined above; estimation of the traffic demand based on explicit consideration of the time and space traffic volatility is for further study.
+
+**5.5** Finally, to decouple the traffic demand characterization from the dimensioning and control procedures and harmonize with the methodology used for traffic engineering for fixed networks and services, the traffic demand processes for systems supporting mobile services have to be kept distinct from processes induced by network operation, such as channel quality maintenance and handover handling.
+
+## **6 Estimation of traffic demand for cellular networks**
+
+### **6.1 Rationale**
+
+**6.1.1** For traffic engineering of cellular systems, information on geographical population distribution is of vital importance to an operator. For new entrants to a market, this information can normally only be estimated using published census information. This may vary in resolution, with the better ones being rather detailed, and may resolve down to municipal or district level. From the census database and the size of the geographical area, it is possible to estimate the population density for the location. Together with the year-on-year user penetration forecast and the average traffic intensity per subscriber, the traffic demand can be obtained.
+
+**6.1.2** In parallel with the traffic engineering process, radio coverage planning is also performed to enable network infrastructure roll-out. Based on the terrain database and the morphology database together with the desired signal level necessary to provide suitable in-building and outdoor services, base site locations are identified. Frequently, contiguous coverage is required and, hence, the coverage area of base sites are packed closely together in order to eliminate coverage gaps as far as possible. In reality, the terrain is rather undulated. In order to eliminate the majority of the coverage gaps, it is required to significantly overlap the coverage between base stations. Thus the dividing lines defined by the equal signal level from two or more base sites will form the boundary of the "best server" region for individual base sites. In other words, when a mobile is within the best server region of a specific base site, it will receive the strongest signal from that base site even though the signal from other base sites may still be adequate for communications. By associating mobile stations with the base site of a best server region, the highest downlink carrier-to-interference ratio can be obtained<sup>1</sup>.
+
+**6.1.3** As the best server regions are rarely regular in shape due to terrain undulation and other geographical features, the traffic capture ability of each base site could be quite different. By mapping the best server region into the population density map, a first order estimation of the traffic demand per sector can be realized. However, this may lead to substantial inaccuracies since users are generally congregated along roads and buildings and rarely located in open spaces. A method to obtain a more accurate estimation of the traffic demand is to polarize the population into areas where it is most likely to be located.
+
+This can be achieved by assigning weightings to different geographical features. Based on these weightings, the traffic for each cell can be more accurately estimated. Evidently, for a cell which contains several open spaces, the amount of traffic is expected to be very low. By contrast, for a cell which contains buildings and shopping areas, the traffic density is expected to be high.
+
+---
+
+<sup>1</sup> In addition, when power control is used in the uplink, a minimum transmit power is required which could in turn prolong battery life of the handsets.
+
+### 6.2 Methodology
+
+6.2.1 The input data to the procedure enabling the estimation of the traffic demand is as follows:
+
+#### Input
+
+- size of the service area<sup>2</sup> (height, width);
+- number and location of the base station sites insiting on the service area;
+- contour of the best server region around each base station site;
+- size of the (identical) elemental areas (height, width) comprising an ideal grid superposed to the service area;
+- population on the service area;
+- service penetration rate;
+- traffic per user;
+- weighting factors accounting for the geographical features of the service area (see Table 1).
+
+**Table 1/E.760 – Weighting factors for the traffic demand in relationship to the geographical features**
+
+| Feature                 | Weight |
+|-------------------------|--------|
+| Road                    | ffs    |
+| Open space              | ffs    |
+| Water                   | ffs    |
+| Road and building       | ffs    |
+| Open space and road     | ffs    |
+| Open space and building | ffs    |
+| Open space and water    | ffs    |
+
+6.2.2 The output of the procedure is:
+
+#### Output
+
+- traffic demand associated with each base station site comprised in the service area.
+
+6.2.3 The estimation of the traffic demand associated with the radio interface of cellular mobile systems is organized according to the following steps:
+
+#### Procedure
+
+Step a) The best server regions associated with the base station sites are noted.
+
+Step b) The ideal grid comprised of the elemental areas is superimposed to the service area.
+
+Step c) The contour of each best service region is approximated by the sequence of the closest sides of the elemental areas. This way a discretization of the best server region is realized, with granularity depending on the size of the elemental areas.
+
+Step d) Each elemental area is assigned a weighting factor depending on the geographical features of the underlying portion of service area. The type of weighting factors are as given in Table 1.
+
+---
+
+<sup>2</sup> The service area is assumed rectangular in shape to simplify the description of the methodology. While no generality is lost in the description, in practice the portions of the best server regions beyond the borders of a rectangular service area have to be accounted for by extending to them the use of the procedure.
+
+Step e) Traffic demand is allocated to each elemental area. The details of the computations are as follows:
+
+- i) normalization factors associated with each elemental area in the ideal grid are computed based on the related weightings given as in Step d). The normalization factors are used to apportion the traffic offered in the service area to the best service regions and, ultimately, to the base station sites;
+- ii) an initial average traffic demand per elemental area is computed by multiplying the traffic offered per user by the user density in an elemental area (the user density in an elemental area is obtained by dividing the total population by the surface of the service area, and multiplying by the service penetration);
+- iii) the initial average traffic per elemental area under ii) above is multiplied by the related normalization factor. This yields the traffic demand associated with each elemental area.
+
+Step f) The products in iii) under Step e) related to the elemental areas comprising the same best server region are summed up: this gives the traffic demand associated with each base site.
+
+An example of how traffic demand can be derived based on the procedure is given in Appendix I.
+
+### **6.3 Upgrading of the procedure for estimating the traffic demand**
+
+Upgrading of the procedure described for estimating the traffic demand is possible. For example, socio-economic information could explicitly impact the weightings used for characterizing the traffic demand associated with individual base station sites. The use of additional information to impact the weighting scale is for further study.
+
+## **7 Mobility modelling and impact on signalling traffic**
+
+**7.1** Mobile networks require dedicated signalling functionality to perform tasks essential to supporting mobile services (e.g. registration, authentication, location and location updating, channel quality monitoring and restoration, etc.) Although explicit consideration of the traffic and mobility processes on the signalling plane is for further study, a model intended to account for the user mobility behaviour is addressed in Appendices II and III. The aim of this model is to represent a basis on which future Recommendations dedicated to dimensioning aspects of mobile networks could expand. This model considers the transition rate of users across the boundary between adjacent regions with significance for mobile networks, such as radio cells (Appendix II) and location areas (Appendix III). The user transition rate is an element which has a direct impact on signalling processes, and hence traffic engineering associated with the signalling plane.
+
+## **8 History**
+
+**8.1** Recommendation first published in 2000.
+
+## **Bibliography**
+
+- GRILLO (D.), SKOOG (R.A.), CHIA (S.), LEUNG (K.K.): Traffic Engineering for Personal Communications in ITU-T Work: The Need to Match Practice and Theory, *IEEE Personal Communications*, Vol. 5, No. 6, pp. 38-58, December 1998.
+
+## APPENDIX I
+
+### Estimating the traffic demand
+
+**I.1** This appendix illustrates how to derive the traffic demand based on the procedure described in 6.2.3. Steps a) to e) of the procedure are illustrated in Figure I.1 with relationship to the following values:
+
+### Input
+
+- size of the service area (height: 1.6 km, width: 1.1 km);
+- number of the base station sites insiting on the service area: 8, location of the base station sites: as in Figure I.1 a);
+- contour of the best server region around each base station site: as in Figure I.1 a);
+- size of the (identical) elemental areas (height: 100 m, width: 100 m) comprising an ideal grid superposed to the service area;
+- population on the service area: 17 600;
+- service penetration rate: 5%;
+- traffic per user: 20 mErlang;
+- weighting factors accounting for the geographical features of the service area: as in Table I.1.
+
+Specifically, Figure I.1 a) shows the geographical features and the best server regions of the area under consideration. Figure I.1 b) shows the  $100 \times 100 \text{ m}^2$  grid overlay on the area. This represents the resolution of the digital terrain database which will eventually determine the resolution of the best server map as well as the traffic distribution map. Assuming that census information indicates that the  $1.1 \times 1.6 \text{ km}^2$  area has a population of 17 600 people, this corresponds to a population density of one person per  $100 \text{ m}^2$ . With a service penetration rate of 5%, there will be 880 subscribers in the area. Given that each user will generate 20 mErlangs of traffic, the total traffic in the area amounts to 17.6 Erlangs. This corresponds to an average traffic density of 1 mErlangs per  $100 \text{ m}^2$ . As the resolution of the digital terrain database is accurate to  $100 \times 100 \text{ m}^2$ , computer prediction of the signal level for the best server region will be quantized into elemental areas of the same size. This is shown in Figure I.1 c). Finally, also assume weighting factors for the traffic load in relationship to the geographical features as represented in Table I.1.
+
+**I.2** By mapping the best server region to the traffic elemental areas, the traffic demand for each cell can be calculated. Applying the weighting to the geographic area as shown in Figure I.1 b), a weighting map as shown in Figure I.1 d) can be obtained. Summing the total weights in the service area and knowing the total traffic, the traffic for each individual bin can be apportioned as shown in Figure I.1 e). Finally, mapping the best server region to the traffic map, the traffic prediction for each cell can be obtained, Figure I.1 f).
+
+To show the importance of using the weighting factors, consider the demanded traffic of Cell 1. Without the weighting factor, a traffic load of 3.3 Erlangs would be predicted. However, with the weighting, a traffic load of 4.2 Erlangs (30% higher) can be anticipated.
+
+It should be noted that the weighting factors shown in this example are indicative and for real applications more calibrations are necessary to ensure satisfactory accuracy.
+
+**Table I.1/E.760 – Weighting factors for the traffic demand in relationship to the geographical features (indicative values)**
+
+| Feature                 | Weight |
+|-------------------------|--------|
+| Road                    | 2      |
+| Open space              | 1      |
+| Water                   | 0      |
+| Road and building       | 3      |
+| Open space and road     | 2      |
+| Open space and building | 3      |
+| Open space and water    | 1      |
+
+![Figure I.1/E.760 – Estimating traffic demand from population distribution, service area layout and radio coverage arrangement. The figure consists of six sub-diagrams (a-f) showing the process from geographical mapping to traffic estimation in Erlangs.](c2b98986bdf45e15707f6b2bd7ade2bd_img.jpg)
+
+**a)** Geographical map showing a road, building, pond, and cells (Cell 1 to Cell 6). A base station is located near Cell 2. The map includes labels: Road, Building, 100 m, Base station, Determining the resolution for figuring out the traffic demand, Best server boundary, Pond, Cell 1, Cell 2, Cell 3, Cell 4, Cell 5, Cell 6, and Figuring out the traffic weighting.
+
+**b)** Grid-based map showing the same geographical features. Labels include: 100 m, Building, Base station, Cell 1, Cell 2, Cell 3, Cell 4, Cell 5, Cell 6, and Best server boundary.
+
+**c)** Map showing computer-predicted best server regions based on terrain map. Labels include: Computer predicted best server regions based on terrain map and Traffic estimation for each cell.
+
+**d)** Generate traffic map, represented by a 20x20 grid of numbers (1, 2, 3).
+
+**e)** Mapping traffic to best server region, represented by a 20x20 grid of decimal values (0.06, 0.17, 0.11, 0.00).
+
+**f)** Final traffic estimation for each cell, showing Cell 1, Cell 2, and Cell 3 with their respective traffic values in Erlangs. Cell 1 has a total of 4.15 Erlangs.
+
+Figure I.1/E.760 – Estimating traffic demand from population distribution, service area layout and radio coverage arrangement. The figure consists of six sub-diagrams (a-f) showing the process from geographical mapping to traffic estimation in Erlangs.
+
+**Figure I.1/E.760 – Estimating traffic demand from population distribution, service area layout and radio coverage arrangement**
+
+### An example methodology for modelling the handover rate between cells in cellular, terrestrial-based mobile systems
+
+**II.1** Prediction of the handover rate in a cellular system has some common features with the prediction of the traffic demand, but it has also some very distinct features. For a given cell, the traffic demand depends on the user density in the whole cell, while the handover rate depends on the user density only in the border of the cell<sup>3</sup>. The in-call user mobility has only a second order impact on the traffic demand, while it has a fundamental impact on the handover rate. The mobility degree or speed of the users has to be considered, as it is necessary to distinguish between indoor and outdoor users, and for outdoor users, between pedestrians and cars.
+
+The handover rate in cell is the rate of in-call users crossing the cell border. Given the overlapping between cells as a first approximation, the border of the cell can be taken as the border of "best server" region of its base station. To assume that the handover rate is equal to the in-call crossing rate of the border of the "best server" region leads to a safe-side estimation of the handover rate, since the system introduces a certain hysteresis before performing a handover<sup>4</sup>.
+
+**II.2** Referring to a cell, distinction has to be made between outgoing handover rate (rate of in-call users moving out the cell) and incoming handover rate (moving into the cell). Both of them are estimated in a similar way. Obviously, an incoming handover in a cell is an outgoing handover of an adjacent cell. Thus we will refer here to the outgoing handover rate bearing in mind that the same could be said on the incoming handover rate.
+
+Let a cell be characterized by:
+
+- A density of in-call users at every point, given by the function  $\sigma = \sigma(x, y)$ .
+- An average value of the component in the normal outside direction of the speed of each in-call user being in a point  $(x, y)$  of the contour, given by the function:  $v_n = v_n(x, y)$ .
+- This average value is obtained considering the above-mentioned component equal to zero when it is negative (i.e. when the user goes in the inside direction).
+- A border/contour  $L$ .
+
+Thus, the number of in-call users crossing out the cell border per time unit,  $h$ , is:
+
+$$h = \int_L \sigma v_n \, dl \quad (\text{II-1})$$
+
+Two different approaches, apart from a mixed one, may be followed to integrate this expression. If the cell is in a rural area crossed by few roads and without any town in the border (see Figure II.1), the density  $\sigma$  can be considered zero in all the points of the border, except in the roads. The simplest way of evaluating the outgoing crossing rate is as the sum of the outgoing crossing rate by each one of the roads crossing the border:
+
+<sup>3</sup> Only handovers due to the user's mobility, i.e. user crossing the border between adjacent cells, are considered here. Other types of handovers (e.g. those due to excessive co-channel interference or to traffic balancing between cells) are not considered in the proposed model.
+
+<sup>4</sup> The case of hierarchical cellular layout with macrocells overlaid to microcells, resulting in more sophisticated rules for performing handovers, is for further study.
+
+![Figure II.1/E.760 – Typical rural area. The diagram shows a large irregular polygon labeled 'Cell' with a smaller irregular polygon labeled 'Town' inside it. Three roads, labeled h1, h2, and h3, cross the cell boundary. Arrows indicate the direction of traffic flow: h1 points out of the cell to the top right, h2 points out of the cell to the top left, and h3 points out of the cell to the bottom right. A small text label 'T0208000-99' is located near the bottom right of the cell boundary.](b8d3d85b1575ec6abdcf1bd9ce438701_img.jpg)
+
+Figure II.1/E.760 – Typical rural area. The diagram shows a large irregular polygon labeled 'Cell' with a smaller irregular polygon labeled 'Town' inside it. Three roads, labeled h1, h2, and h3, cross the cell boundary. Arrows indicate the direction of traffic flow: h1 points out of the cell to the top right, h2 points out of the cell to the top left, and h3 points out of the cell to the bottom right. A small text label 'T0208000-99' is located near the bottom right of the cell boundary.
+
+**Figure II.1/E.760 – Typical rural area**
+
+$$h = \sum_j h_j \quad (\text{II-2})$$
+
+where  $h_j$  is the number of in-call users passing by road  $i$  in the outside direction per time unit. Note that the existence of a town inside the cell, as in Figure II.1, is not explicitly considered in Formula II-2.  $h_j$  may be estimated from published road traffic information. The number of cars passing by each road per time unit must be multiplied by the service penetration factor and by the average traffic per user. If the cell border is close to a town, the number of pedestrians (with mobile set and in conversation) crossing the border by each of the roads must also be considered.
+
+This approach, which is quite simple in a rural area with few roads, becomes tedious when the number of roads crossing the cell is large and even more in an urban area with a high number of streets. [1] shows that when the number of roads or streets crossing the cell is in the order of 10 or higher, a good approximation is to assume that the mobiles follow a random uniformly distributed direction with a same average modular speed in all the directions. If  $v$  is the average modular speed of the in-call users, then:
+
+$$v_n = \frac{v}{\pi} \quad (\text{II-3})$$
+
+and Formula (II-1) becomes:
+
+$$h = \int_L \frac{\sigma v}{\pi} d l \quad (\text{II-4})$$
+
+If both  $\sigma$  and  $v$  can be considered constant along the contour, the outgoing crossing rate is:
+
+$$h = \frac{\sigma v}{\pi} p \quad (\text{II-5})$$
+
+where  $p$  is the perimeter of the cell.
+
+If  $\sigma$  can be considered constant in all the internal points of the cell:
+
+$$h = a \frac{v p}{\pi S} \quad (\text{II-6})$$
+
+where  $a$  is the (originating plus terminating) traffic demand in the cell and  $S$  is the surface of the cell. Formula (II-5) and even more Formula (II-6) can be used in most cases only as a first approximation since the assumptions on which they are based are not usually satisfied. Thus, a more appropriate way of evaluating (II-4) is by overlaying a grid on the area as explained in Appendix I. Figure II.2 shows a  $100 \times 100 \text{ m}^2$  grid overlay on a cell. The border of the cell passes through 14 bins of the grid.
+
+![Figure II.2/E.760: Use of a grid to estimate handover rate. The figure shows a 6x6 grid with a polygonal cell boundary drawn across it. The boundary is labeled with numbers 1 through 14 at its vertices. The cell is roughly pentagonal, with vertices at (1,4), (2,4), (3,3), (4,2), (5,2), (5,3), (4,4), (3,4), (2,4), and (1,4) in grid coordinates. The label 'T0208010-99' is at the bottom right.](1d529a819ad929684331c55eed6673bb_img.jpg)
+
+Figure II.2/E.760: Use of a grid to estimate handover rate. The figure shows a 6x6 grid with a polygonal cell boundary drawn across it. The boundary is labeled with numbers 1 through 14 at its vertices. The cell is roughly pentagonal, with vertices at (1,4), (2,4), (3,3), (4,2), (5,2), (5,3), (4,4), (3,4), (2,4), and (1,4) in grid coordinates. The label 'T0208010-99' is at the bottom right.
+
+**Figure II.2/E.760 – Use of a grid to estimate handover rate**
+
+For each bin  $i$  of the grid, the traffic demand  $a_i$ , the average speed  $v_i$  and the length  $p_i$  of the cell border within the bin can be estimated, and then Formula (II-4) becomes:
+
+$$h = \frac{1}{\pi \cdot s} \sum_i a_i v_i p_i \quad (\text{II-7})$$
+
+where  $s$  is the surface of a bin ( $10\,000\text{ m}^2$  in the case considered).
+
+For estimating the product  $a_i v_i$  in each bin, it may be useful to distinguish three types of users with very different mobility characteristics:
+
+- Indoor users, characterized by a traffic demand  $a_{di}$  and an average speed  $v_{di}$ .
+- Outdoor pedestrian users, characterized by a traffic demand  $a_{pi}$  and average speed  $v_{pi}$ <sup>5</sup>.
+- Users in cars, characterized by a traffic demand  $a_{ci}$  and an average speed  $v_{ci}$ .
+
+Thus Formula (II-7) could be written as:
+
+$$h = \frac{1}{\pi \cdot s} \sum_i (a_{di} v_{di} + a_{pi} v_{pi} + a_{ci} v_{ci}) p_i \quad (\text{II-8})$$
+
+$a_{di}$ ,  $a_{pi}$  and  $a_{ci}$  can be estimated by a procedure similar to that explained in Appendix I: to estimate the traffic demand of the group of users in the whole area and to apportion it among the bins by assigning a weighting factor to each bin. For estimating the average speed  $a_{di}$ ,  $a_{pi}$  or  $a_{ci}$ , the fraction of users in movement during a call can be estimated, and multiplied by an estimation of their average speed.
+
+For evaluating  $p_i$  it has to be considered that cell borders inside buildings are in general more irregular than in open spaces, with incurred higher values for  $p_i$ . Moreover, in the case of high buildings upper floors are sensitive to line-of-sight effects between base station antennas and openings in the walls (windows, external doors, etc.) which may alter the relationship between receiving/transmitting devices and best station valid for lower floors. These effects usually result in sequences of smaller, interleaved cells and, ultimately, in higher  $p_i$  values. The quantification of the dependency of  $p_i$  on the above aspects is for further study.
+
+<sup>5</sup> Users in large indoor surfaces (as e.g. large shopping centres) could have a mobility behaviour more similar to outdoor pedestrian users than to users in small indoor sites. In this case, they should be characterized by  $v_{pi}$  instead of  $v_{di}$  and their traffic demand included in  $a_{pi}$  instead of in  $a_{di}$ .
+
+In some areas, a mixed approach among those represented by Formulae (II-2) and (II-8) could be more appropriate, for example, in a city crossed by a few highways, as in Figure II.3 a), or a cell whose border is partially inside a city and partially outside it, as in Figure II.3 b).
+
+![Figure II.3/E.760 – Examples in which a mixed approach is appropriate to estimate the handover rate. The figure contains two diagrams, Case a) and Case b). Case a) shows a 'City' area with a 'Cell' inside it, crossed by two 'Highways'. Case b) shows a 'City' area with a 'Cell' partially inside and partially outside it, crossed by 'Roads'. A reference code 'T0208020-99' is present in Case b).](ff7ce44f3fdd51bae7b231f34df07c6a_img.jpg)
+
+Figure II.3/E.760 – Examples in which a mixed approach is appropriate to estimate the handover rate. The figure contains two diagrams, Case a) and Case b). Case a) shows a 'City' area with a 'Cell' inside it, crossed by two 'Highways'. Case b) shows a 'City' area with a 'Cell' partially inside and partially outside it, crossed by 'Roads'. A reference code 'T0208020-99' is present in Case b).
+
+**Figure II.3/E.760 – Examples in which a mixed approach is appropriate to estimate the handover rate**
+
+In these cases, a high fraction of the handovers may be produced by cars going by few roads or highways, but the number of handovers produced by other users (pedestrians or cars in streets or indoor users) may also be significant. It may be appropriate to estimate the rate of handovers produced by cars in the roads by means of Formula (II-2) and the rate of handovers produced by the other users by means of Formula (II-8). In this formula  $a_{ci}$  must not include the traffic produced by the cars in the roads.
+
+## APPENDIX III
+
+### **An example methodology for modelling the location registration and location updating rate in cellular, terrestrial-based mobile systems**
+
+A location registration is produced when the user switches on the mobile set, and a location updating is produced when a switched-on mobile crosses the border of a location area.
+
+The total location registration rate in a geographical area does not depend on the layout of location areas, while the location updating rate depends on it. For estimating the location registration rate, the operator must firstly estimate the number of users in the area and multiply it by the location registration rate per user, which can be estimated from the experience gained in geographical areas with similar characteristics. If the operator is interested in apportioning the total location registration rate into location registration rates for each cell, the same procedure explained in Appendix I for apportioning the traffic demand for each cell can be followed.
+
+For estimating the location updating rate in a location area, the same methodology explained in Appendix II for estimating the handover rate may be followed. Formulas of Appendix II apply to this case by only changing:
+
+- Cell by location area.
+- Traffic demand by number of switched-on users.
+
+This methodology may be appropriate for the first deployment of the network. Once the network has been deployed, statistics can be taken on the rate of handovers between each pair of adjacent cells. By assuming proportionality between the location updating rate and the handover rate between each pair of adjacent cells, the location updating rate for any other configuration of location areas can be estimated. It allows to choose the location area layout which minimizes the total location updating rate.
+
+## **Bibliography**
+
+- [1] MORALES-ANDRÉS (G.), VILLÉN-ALTAMIRANO (M.): An Approach to Modelling Subscriber Mobility in Cellular Radio Networks, *Forum TELECOM-87*, Geneva 1987.
+
+
+
+# ITU-T RECOMMENDATIONS SERIES
+
+|                 |                                                                                                                                |
+|-----------------|--------------------------------------------------------------------------------------------------------------------------------|
+| Series A        | Organization of the work of the ITU-T                                                                                          |
+| Series B        | Means of expression: definitions, symbols, classification                                                                      |
+| Series C        | General telecommunication statistics                                                                                           |
+| Series D        | General tariff principles                                                                                                      |
+| <b>Series E</b> | <b>Overall network operation, telephone service, service operation and human factors</b>                                       |
+| Series F        | Non-telephone telecommunication services                                                                                       |
+| Series G        | Transmission systems and media, digital systems and networks                                                                   |
+| Series H        | Audiovisual and multimedia systems                                                                                             |
+| Series I        | Integrated services digital network                                                                                            |
+| Series J        | Transmission of television, sound programme and other multimedia signals                                                       |
+| Series K        | Protection against interference                                                                                                |
+| Series L        | Construction, installation and protection of cables and other elements of outside plant                                        |
+| Series M        | TMN and network maintenance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits |
+| Series N        | Maintenance: international sound programme and television transmission circuits                                                |
+| Series O        | Specifications of measuring equipment                                                                                          |
+| Series P        | Telephone transmission quality, telephone installations, local line networks                                                   |
+| Series Q        | Switching and signalling                                                                                                       |
+| Series R        | Telegraph transmission                                                                                                         |
+| Series S        | Telegraph services terminal equipment                                                                                          |
+| Series T        | Terminals for telematic services                                                                                               |
+| Series U        | Telegraph switching                                                                                                            |
+| Series V        | Data communication over the telephone network                                                                                  |
+| Series X        | Data networks and open system communications                                                                                   |
+| Series Y        | Global information infrastructure and Internet protocol aspects                                                                |
+| Series Z        | Languages and general software aspects for telecommunication systems                                                           |

marked/E/T-REC-E.773-199610-I_PDF-E/raw.md

@@ -0,0 +1,218 @@
+
+
+![ITU logo: A globe with a lightning bolt and the letters ITU.](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg)
+
+ITU logo: A globe with a lightning bolt and the letters ITU.
+
+INTERNATIONAL TELECOMMUNICATION UNION
+
+**ITU-T**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+**E.773**
+
+(10/96)
+
+SERIES E: TELEPHONE NETWORK AND ISDN
+
+Quality of service, network management and traffic  
+engineering – Traffic engineering – Mobile network traffic  
+engineering
+
+---
+
+**Maritime and aeronautical mobile grade of  
+service concept**
+
+ITU-T Recommendation E.773
+
+(Previously CCITT Recommendation)
+
+---
+
+# ITU-T E-SERIES RECOMMENDATIONS **TELEPHONE NETWORK AND ISDN**
+
+## **OPERATION, NUMBERING, ROUTING AND MOBILE SERVICES**
+
+|                                                                                                   |             |
+|---------------------------------------------------------------------------------------------------|-------------|
+| INTERNATIONAL OPERATION                                                                           | E.100–E.229 |
+| OPERATIONAL PROVISIONS RELATING TO CHARGING AND ACCOUNTING IN THE INTERNATIONAL TELEPHONE SERVICE | E.230–E.299 |
+| UTILIZATION OF THE INTERNATIONAL TELEPHONE NETWORK FOR NON-TELEPHONY APPLICATIONS                 | E.300–E.329 |
+| ISDN PROVISIONS CONCERNING USERS                                                                  | E.330–E.399 |
+
+## **QUALITY OF SERVICE, NETWORK MANAGEMENT AND TRAFFIC ENGINEERING**
+
+|                                                                                                |                    |
+|------------------------------------------------------------------------------------------------|--------------------|
+| NETWORK MANAGEMENT                                                                             | E.400–E.489        |
+| International service statistics                                                               | E.400–E.409        |
+| International network management                                                               | E.410–E.419        |
+| Checking the quality of the international telephone service                                    | E.420–E.489        |
+| TRAFFIC ENGINEERING                                                                            | E.490–E.799        |
+| Measurement and recording of traffic                                                           | E.490–E.505        |
+| Forecasting of traffic                                                                         | E.506–E.509        |
+| Determination of the number of circuits in manual operation                                    | E.510–E.519        |
+| Determination of the number of circuits in automatic and semi-automatic operation              | E.520–E.539        |
+| Grade of service                                                                               | E.540–E.599        |
+| Definitions                                                                                    | E.600–E.699        |
+| ISDN traffic engineering                                                                       | E.700–E.749        |
+| <b>Mobile network traffic engineering</b>                                                      | <b>E.750–E.799</b> |
+| QUALITY OF TELECOMMUNICATION SERVICES: CONCEPTS, MODELS, OBJECTIVES AND DEPENDABILITY PLANNING | E.800–E.899        |
+| Terms and definitions related to the quality of telecommunication services                     | E.800–E.809        |
+| Models for telecommunication services                                                          | E.810–E.844        |
+| Objectives for quality of service and related concepts of telecommunication services           | E.845–E.859        |
+| Use of quality of service objectives for planning of telecommunication networks                | E.860–E.879        |
+| Field data collection and evaluation on the performance of equipment, networks and services    | E.880–E.899        |
+
+*For further details, please refer to ITU-T List of Recommendations.*
+
+## **ITU-T RECOMMENDATION E.773**
+
+## **MARITIME AND AERONAUTICAL MOBILE GRADE OF SERVICE CONCEPT**
+
+### **Summary**
+
+This Recommendation introduces the Grade of Service (GOS) concept for both satellite- and terrestrial-based maritime and aeronautical mobile systems. This Recommendation confines initially the GOS concept to circuit-switched user plane traffic. Signalling traffic issues associated with the user plane traffic are covered under separate Recommendations.
+
+###### **Source**
+
+ITU-T Recommendation E.773 was prepared by ITU-T Study Group 2 (1993-1996) and was approved under the WTSC Resolution No. 1 procedure on the 8th of October 1996.
+
+## FOREWORD
+
+ITU (International Telecommunication Union) is the United Nations Specialized Agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the ITU. The ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis.
+
+The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics.
+
+The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Resolution No. 1 (Helsinki, March 1-12, 1993).
+
+In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC.
+
+### NOTE
+
+In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+© ITU 1997
+
+All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU.
+
+## CONTENTS
+
+|   |                                                                                                               | Page |
+|---|---------------------------------------------------------------------------------------------------------------|------|
+| 1 | Scope.....                                                                                                    | 1    |
+| 2 | References.....                                                                                               | 1    |
+| 3 | Definitions .....                                                                                             | 1    |
+| 4 | Abbreviations.....                                                                                            | 1    |
+| 5 | GOS concept .....                                                                                             | 2    |
+| 6 | Principles to allocate GOS targets .....                                                                      | 2    |
+| 7 | Principles to select GOS maritime and aeronautical mobiles and fixed network interconnection parameters ..... | 3    |
+| 8 | History.....                                                                                                  | 3    |
+
+
+
+## **MARITIME AND AERONAUTICAL MOBILE GRADE OF SERVICE CONCEPT**
+
+*(Geneva, 1996)*
+
+### **1 Scope**
+
+This Recommendation introduces the Grade of Service (GOS) concept for both satellite- and terrestrial-based maritime and aeronautical mobile systems. Circuit-switched and packet-switched services are provided by these systems.
+
+This Recommendation confines initially the GOS concept to circuit-switched user plane traffic. Signalling traffic issues associated with the user plane traffic are covered under separate Recommendations.
+
+### **2 References**
+
+The following Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; all users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published.
+
+The following Recommendations contain material that is either relevant to or provides background for this Recommendation:
+
+- ITU-T Recommendation E.220 (1996), *Interconnection of public land mobile networks (PLMN)*.
+- ITU-T Recommendation E.600 (1993), *Terms and definitions for traffic engineering*.
+- CCITT Recommendation E.720 (1988), *ISDN Grade of Service concept*.
+- ITU-T Recommendation E.752 (1996), *Reference connections for traffic engineering of maritime and aeronautical systems*.
+- ITU-T Recommendation E.770 (1993), *Land mobile and fixed network interconnection traffic Grade of Service concept*.
+- ITU-T Recommendation E.771 (1996), *Network Grade of Service parameters and target values for circuit-switched public land mobile services*.
+- ITU-T Recommendation E.774 (1996), *Network Grade of Service parameters and target values for maritime and aeronautical mobile services*.
+- ITU-T Recommendation F.110 (1996), *Operational provision for the maritime mobile service*.
+
+### **3 Definitions**
+
+Definitions relevant to this Recommendation are contained in Recommendation E.752.
+
+### **4 Abbreviations**
+
+For the purposes of this Recommendation, the following abbreviation is used.
+
+### 5 GOS concept
+
+For maritime and aeronautical mobile systems, transmission quality of the radio link, user behaviour and spectrum re-use are factors that may impact traffic Grade of Service parameters in a unique way. In turn, the Quality of Service (QOS) experienced by the users is dependent on the defined GOS targets.
+
+The key aspects which characterize maritime and aeronautical services in a unique way are the mobility on a global scale for maritime service and the high-speed of users movement for the aeronautical service. This contributes to the complexity of the supporting communication infrastructure and the related control actions. Although future systems may envisage sophisticated radio coverage architecture, such as "spot beam" and "global beam" operation, GOS parameters for current systems apply for "global beam" only.
+
+Similarly as with land mobile systems, users can appreciate GOS directly through failure to establish a connection due to poor channel quality, deterioration of the transmission quality on and possible cut-off of an established connection.
+
+The identified GOS parameters may be utilized to define the GOS targets for different segments of the connection path between a maritime/aeronautical user and the interfacing network element in the fixed domain. The target values of the GOS parameters shall be set under normal and overload conditions.
+
+### 6 Principles to allocate GOS targets
+
+The principles to allocate GOS targets for connections including a maritime or aeronautical network segment are generally the same as those described in Recommendation E.720. Accordingly, GOS target values are initially set end-to-end (user GOS) and subsequently allocated to network segments.
+
+In a connection, maritime and aeronautical network segments may replace, from a logical point of view, fixed network counterparts. However, it may not be possible, in general, for maritime and aeronautical network segments of existing systems to cost-effectively maintain some (or all) of the performance targets set for GOS parameters associated with corresponding fixed network segments. This is consistent with the current perception of maritime and aeronautical users that a service provided via a maritime and aeronautical network, or network segment, can hardly compare on an equal basis with the same service fully provided through the fixed network.
+
+A differentiation of the GOS performance targets for specific network segments and in specific situations with respect to their fixed network logical counterparts is introduced in principle. The differentiation must, however, guarantee that specific bounds to the end-to-end GOS parameters values are met.
+
+In connections comprising both maritime (or aeronautical) and fixed network segments, the allocation of GOS targets for the fixed network segments shall be the same as for end-to-end fixed network connections. In other words, interconnection of maritime and aeronautical and fixed networks should not impose any requirement for additional performance nor any restriction in the normal operation of the fixed network, in accordance with Recommendation E.220. This enables independent design and implementation of functional network elements, both fixed and maritime and aeronautical.
+
+Different GOS budgets for the maritime and aeronautical network may result from different fixed network segment replacements.
+
+The elements comprising a connection including maritime or aeronautical network segments are depicted in Figure 1. GOS parameters and target values are defined for the Satellite/Terrestrial Subsystem and the Ground Subsystem, as introduced in Recommendation E.752.
+
+![Diagram showing the elements of a connection: Maritime/Aeronautical User, Mobile User Subsystem, Terrestrial/Satellite Subsystem, Ground Subsystem, and Fixed Network.](acfc53eca625d62b38aa2563efa95c3e_img.jpg)
+
+The diagram illustrates a sequence of five interconnected components arranged horizontally. It begins with a small icon on the left representing a 'Maritime/Aeronautical User', consisting of a circle and a triangle. This is connected by a line to an oval labeled 'Mobile User Subsystem'. This oval is connected to another oval labeled 'Terrestrial/Satellite Subsystem'. This second oval is connected to a third oval labeled 'Ground Subsystem'. Finally, the 'Ground Subsystem' oval is connected to a fourth oval labeled 'Fixed Network'. Below the first oval is the text 'Maritime/Aeronautical User'. Below the last oval is the text 'T0205590-96'.
+
+Diagram showing the elements of a connection: Maritime/Aeronautical User, Mobile User Subsystem, Terrestrial/Satellite Subsystem, Ground Subsystem, and Fixed Network.
+
+FIGURE 1/E.773
+
+#### **Elements in a connection including maritime or aeronautical network segments**
+
+### **7 Principles to select GOS maritime and aeronautical mobiles and fixed network interconnection parameters**
+
+For further study.
+
+### **8 History**
+
+This is the first issue of Recommendation E.773.
+
+# ITU-T RECOMMENDATIONS SERIES
+
+- Series A Organization of the work of the ITU-T
+- Series B Means of expression
+- Series C General telecommunication statistics
+- Series D General tariff principles
+- Series E Telephone network and ISDN**
+- Series F Non-telephone telecommunication services
+- Series G Transmission systems and media
+- Series H Transmission of non-telephone signals
+- Series I Integrated services digital network
+- Series J Transmission of sound-programme and television signals
+- Series K Protection against interference
+- Series L Construction, installation and protection of cables and other elements of outside plant
+- Series M Maintenance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits
+- Series N Maintenance: international sound-programme and television transmission circuits
+- Series O Specifications of measuring equipment
+- Series P Telephone transmission quality
+- Series Q Switching and signalling
+- Series R Telegraph transmission
+- Series S Telegraph services terminal equipment
+- Series T Terminal equipment and protocols for telematic services
+- Series U Telegraph switching
+- Series V Data communication over the telephone network
+- Series X Data networks and open system communication
+- Series Z Programming languages

marked/E/T-REC-E.774-199610-I_PDF-E/raw.md

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+
+
+![ITU logo: A globe with a lightning bolt and the letters ITU.](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg)
+
+ITU logo: A globe with a lightning bolt and the letters ITU.
+
+INTERNATIONAL TELECOMMUNICATION UNION
+
+**ITU-T**
+
+**E.774**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+(10/96)
+
+SERIES E: TELEPHONE NETWORK AND ISDN
+
+Quality of service, network management and traffic  
+engineering – Traffic engineering – Mobile network traffic  
+engineering
+
+---
+
+**Network grade of service parameters and target  
+values for maritime and aeronautical mobile  
+services**
+
+ITU-T Recommendation E.774
+
+(Previously CCITT Recommendation)
+
+---
+
+# ITU-T E-SERIES RECOMMENDATIONS **TELEPHONE NETWORK AND ISDN**
+
+|                                                                                                   |                    |
+|---------------------------------------------------------------------------------------------------|--------------------|
+| <b>OPERATION, NUMBERING, ROUTING AND MOBILE SERVICES</b>                                          |                    |
+| INTERNATIONAL OPERATION                                                                           | E.100–E.229        |
+| OPERATIONAL PROVISIONS RELATING TO CHARGING AND ACCOUNTING IN THE INTERNATIONAL TELEPHONE SERVICE | E.230–E.299        |
+| UTILIZATION OF THE INTERNATIONAL TELEPHONE NETWORK FOR NON-TELEPHONY APPLICATIONS                 | E.300–E.329        |
+| ISDN PROVISIONS CONCERNING USERS                                                                  | E.330–E.399        |
+| <b>QUALITY OF SERVICE, NETWORK MANAGEMENT AND TRAFFIC ENGINEERING</b>                             |                    |
+| NETWORK MANAGEMENT                                                                                | E.400–E.489        |
+| International service statistics                                                                  | E.400–E.409        |
+| International network management                                                                  | E.410–E.419        |
+| Checking the quality of the international telephone service                                       | E.420–E.489        |
+| TRAFFIC ENGINEERING                                                                               | E.490–E.799        |
+| Measurement and recording of traffic                                                              | E.490–E.505        |
+| Forecasting of traffic                                                                            | E.506–E.509        |
+| Determination of the number of circuits in manual operation                                       | E.510–E.519        |
+| Determination of the number of circuits in automatic and semi-automatic operation                 | E.520–E.539        |
+| Grade of service                                                                                  | E.540–E.599        |
+| Definitions                                                                                       | E.600–E.699        |
+| ISDN traffic engineering                                                                          | E.700–E.749        |
+| <b>Mobile network traffic engineering</b>                                                         | <b>E.750–E.799</b> |
+| QUALITY OF TELECOMMUNICATION SERVICES: CONCEPTS, MODELS, OBJECTIVES AND DEPENDABILITY PLANNING    | E.800–E.899        |
+| Terms and definitions related to the quality of telecommunication services                        | E.800–E.809        |
+| Models for telecommunication services                                                             | E.810–E.844        |
+| Objectives for quality of service and related concepts of telecommunication services              | E.845–E.859        |
+| Use of quality of service objectives for planning of telecommunication networks                   | E.860–E.879        |
+| Field data collection and evaluation on the performance of equipment, networks and services       | E.880–E.899        |
+
+For further details, please refer to ITU-T List of Recommendations.
+
+## **ITU-T RECOMMENDATION E.774**
+
+# **NETWORK GRADE OF SERVICE PARAMETERS AND TARGET VALUES FOR MARITIME AND AERONAUTICAL MOBILE SERVICES**
+
+## **Summary**
+
+This Recommendation identifies the Grade of Service (GOS) parameters and associated target values for circuit-switched services in both satellite- and terrestrial-based maritime and aeronautical systems. The GOS parameters and target values are confined to the mobile network segment of end-to-end connections.
+
+### **Source**
+
+ITU-T Recommendation E.774 was prepared by ITU-T Study Group 2 (1993-1996) and was approved under the WTSC Resolution No. 1 procedure on the 8th of October 1996.
+
+## FOREWORD
+
+ITU (International Telecommunication Union) is the United Nations Specialized Agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the ITU. The ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis.
+
+The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics.
+
+The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Resolution No. 1 (Helsinki, March 1-12, 1993).
+
+In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC.
+
+### NOTE
+
+In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+© ITU 1997
+
+All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU.
+
+## CONTENTS
+
+|                                                                                  | Page |
+|----------------------------------------------------------------------------------|------|
+| 1 Scope.....                                                                     | 1    |
+| 2 Related Recommendations .....                                                  | 1    |
+| 3 Definitions .....                                                              | 1    |
+| 4 Abbreviations.....                                                             | 2    |
+| 5 Introduction.....                                                              | 2    |
+| 6 GOS parameters and target values.....                                          | 2    |
+| 6.1 GOS parameters.....                                                          | 2    |
+| 6.1.1 Probability of link blocking for the terrestrial/satellite subsystem ..... | 3    |
+| 6.1.2 Probability of blocking at LES/GES.....                                    | 3    |
+| 6.1.3 Probability of unsuccessful handover for terrestrial based systems .....   | 3    |
+| 6.1.4 Authentication delay.....                                                  | 3    |
+| 6.2 Target values for GOS parameters.....                                        | 4    |
+| 7 History.....                                                                   | 5    |
+
+
+
+## **NETWORK GRADE OF SERVICE PARAMETERS AND TARGET VALUES FOR MARITIME AND AERONAUTICAL MOBILE SERVICES**
+
+*(Geneva, 1996)*
+
+# **1 Scope**
+
+This Recommendation outlines the general consideration for identifying Grade of Service (GOS) parameters for the maritime and aeronautical circuit-switched services and defines the target values under normal and heavy traffic load conditions.
+
+These parameters are defined – and their target values specified – assuming that the network and the network components are operating in their normal mode (i.e. are fully operational). Further, the parameters and their target values assume normal (as opposed to distress or emergency) traffic.
+
+Mobile services in terrestrial- and satellite-based maritime and aeronautical systems can be circuit- or packet-switched. This Recommendation is initially concerned with circuit-switched user plane traffic and normal (as opposed to distress and safety) traffic. Packet-switched traffic is for further study. This Recommendation is applicable to the terrestrial/satellite subsystem.
+
+# **2 Related Recommendations**
+
+The following Recommendations contain material that is either relevant to or provides background for this Recommendation:
+
+- CCITT Recommendation E.500 (1992), *Traffic intensity measurement principles*.
+- ITU-T Recommendation E.600 (1993), *Terms and definitions of traffic engineering*.
+- ITU-T Recommendation E.751 (1996), *Reference connections for traffic engineering of land mobile networks*.
+- ITU-T Recommendation E.752 (1996), *Reference connections for traffic engineering of maritime and aeronautical systems*.
+- ITU-T Recommendation E.770 (1993), *Land mobile and fixed network interconnection traffic grade of service concept*.
+- ITU-T Recommendation E.771 (1996), *Network grade of service parameters and target values for circuit-switched public land mobile services*.
+- ITU-T Recommendation E.773 (1996), *Maritime and aeronautical mobile grade of service concept*.
+- ITU-T Recommendation F.110 (1996), *Operational provision for the maritime mobile service*.
+
+# **3 Definitions**
+
+Definitions relevant to this Recommendation are contained in Recommendation E.752. The following definitions complement those in Recommendation E.752.
+
+**3.1 normal traffic load<sup>1</sup>:** Average of all week days busy hour traffic for the three busiest months of the year excluding December – (Average Busy Season Busy Hour, ABSBH).
+
+**3.2 high traffic load<sup>1</sup>:** Mean of the three highest busy hour traffic in the same period as the normal load subject to the condition that the three values fall on different days – (Highest Busy Season Busy Hour, HBSBH).
+
+# **4 Abbreviations**
+
+For the purposes of this Recommendation, the following abbreviations are used.
+
+|       |                                 |
+|-------|---------------------------------|
+| ABSBH | Average Busy Season Busy Hour   |
+| AES   | Aircraft Earth Station          |
+| GES   | Ground Earth Station            |
+| GOS   | Grade of Service                |
+| GS    | Ground Station                  |
+| HBSBH | Highest Busy Season Busy Hour   |
+| LES   | Land Earth Station              |
+| SES   | Ship Earth Station              |
+| TSS   | Terrestrial/Satellite Subsystem |
+
+# **5 Introduction**
+
+This Recommendation proposes network Grade of Service (GOS) parameters and target values for both satellite- and terrestrial-based maritime/aeronautical mobile networks. Although these systems provide circuit- and packet-switched services, this Recommendation defines the parameters and the target values only for the circuit-switched traffic. The parameters and target values for the signalling traffic are covered under separate Recommendations.
+
+Note that in aeronautical mobile-satellite systems the high traffic load (HBSBH) is typically 30% greater than the normal traffic load (ABSBH). Hence the GOS criteria for the ABSBH typically would not meet that of HBSBH and therefore the aeronautical mobile-satellite systems must be dimensioned for the HBSBH.
+
+This Recommendation covers GOS parameters and target values for both terrestrial- and satellite-based mobile networks.
+
+# **6 GOS parameters and target values**
+
+## **6.1 GOS parameters**
+
+The GOS parameters for circuit-switched traffic specified on an end-to-end basis depend on a number of factors. These include user behaviour, routing arrangements such as priority offered in the
+
+---
+
+<sup>1</sup> This definition is derived from Recommendation E.500, modified to reflect the peculiar diurnal and seasonal profile of mobile satellite telecommunications using SCPC (Single Channel Per Carrier) demand assigned channel allocation.
+
+different stages of connection, and the time difference between busy hours associated with different segments of the connection.
+
+A successful call attempt is one for which the system has successfully assigned a channel and routed a call attempt to the designated terminal address. A non-pre-empted call attempt to a busy end-user should be treated as successful from the viewpoint of the GOS performance.
+
+In this Recommendation, the following traffic GOS parameters are specified for mobile circuit-switched services.
+
+- probability of link blocking for the terrestrial/satellite subsystem;
+- probability of blocking at LES/GES;
+- probability of unsuccessful handover for terrestrial-based systems;
+- authentication delay.
+
+### **6.1.1 Probability of link blocking for the terrestrial/satellite subsystem**
+
+Probability that an offered call will be blocked (loss probability) during the busy hour due to shortage of satellite/terrestrial circuits in the terrestrial/satellite subsystem segment. Different GOS target values for link blocking probability are applicable to carry Average Busy Season Busy Hour (ABSBH) traffic and Highest Busy Season Busy Hour (HBSBH) traffic.
+
+### **6.1.2 Probability of blocking at LES/GES**
+
+Probability that an offered call will fail due to shortage of channel units and terrestrial link to fixed network at LES/GES in the ground subsystem. As in the case of the probability of link blocking for the terrestrial/satellite subsystem, the target values are defined for ABSBH and HBSBH traffic load conditions.
+
+### **6.1.3 Probability of unsuccessful handover for terrestrial based systems**
+
+This parameter is the probability that a handover attempt fails because of lack of radio resources in the target cell, or because of a lack of free resources for establishing the new network connection. The failure condition is based either on a specified time interval since the handover request was first issued or on a threshold on signal strength. (Satellite-based systems can be designed without the possibility of handover between spot beams, e.g. the original Inmarsat system)
+
+### **6.1.4 Authentication delay**
+
+Authentication of an automatic credit/charge/calling card call, originating from a mobile station involves a preliminary (format) verification at the SES/AES before the information is passed to the LES/GES for further processing.
+
+Authentication delay is defined as the time elapsed since the initial verification is performed at the LES/GES to the time the caller receives the authentication message. The final responsibility for meeting the target value for the authentication delay rests with the mobile service provider, although the total authentication procedure may be accomplished by using a combination of mobile and fixed network facilities. These latter are credit card agency database systems chosen by the mobile service provider and typically contribute a substantial portion to the overall authentication delay.
+
+The GOS parameters recommended for maritime and aeronautical circuit switched-services are summarized in Table 1.
+
+TABLE 1/E.774
+
+### **GOS parameters for maritime and aeronautical mobile services**
+
+| GOS parameters                                                                                                                              | Terrestrial mobile network |     |     | Satellite mobile network |     |     |
+|---------------------------------------------------------------------------------------------------------------------------------------------|----------------------------|-----|-----|--------------------------|-----|-----|
+|                                                                                                                                             | M-F                        | F-M | M-M | M-F                      | F-M | M-M |
+| Probability of link blocking for terrestrial/satellite subsystem                                                                            | A                          | A   | A   | A                        | A   | A   |
+| Probability of blocking at LES/GES                                                                                                          | A                          | A   | A   | A                        | A   | A   |
+| Probability of unsuccessful handover                                                                                                        | FS                         | FS  | FS  | NA                       | NA  | NA  |
+| Authentication delay for mobile originated credit card calls                                                                                | FS                         | FS  | FS  | A                        | NA  | A   |
+| M-F Mobile-to-Fixed network<br>F-M Fixed network-to-Mobile<br>M-M Mobile-to-Mobile<br>A Applicable<br>NA Not Applicable<br>FS Further Study |                            |     |     |                          |     |     |
+
+## **6.2 Target values for GOS parameters**
+
+GOS target values for circuit-switched services are given in Table 2.
+
+TABLE 2/E.774
+
+### **Target values for GOS parameters - circuit-switched services**
+
+|                                                                                                                       | Terrestrial mobile network |              | Satellite mobile network                                          |                                                                |
+|-----------------------------------------------------------------------------------------------------------------------|----------------------------|--------------|-------------------------------------------------------------------|----------------------------------------------------------------|
+|                                                                                                                       | Maritime                   | Aeronautical | Maritime                                                          | Aeronautical                                                   |
+| GOS parameters                                                                                                        | Maritime                   | Aeronautical | Maritime                                                          | Aeronautical                                                   |
+| Probability of Link blocking for terrestrial/satellite Subsystem                                                      | FS                         | FS           |                                                                   |                                                                |
+| Normal Load                                                                                                           |                            |              | 2%                                                                | 2%                                                             |
+| High Load                                                                                                             |                            |              | 10%                                                               | 10%                                                            |
+| Probability of blocking at LES/GES                                                                                    | FS                         | FS           |                                                                   |                                                                |
+| Normal Load                                                                                                           |                            |              | 1%                                                                | 1%                                                             |
+| High Load                                                                                                             |                            |              | 2%                                                                | 2%                                                             |
+| Probability of unsuccessful handover                                                                                  | FS                         | FS           | NA                                                                | NA                                                             |
+| Authentication delay<br>(only for mobile originated calls,<br>normal and high load)                                   | FS                         | FS           | 95% of calls to<br>be authenticated<br>within $\leq 15.0$<br>secs | 95% of calls to<br>be authenticated<br>within $\leq 12.0$ secs |
+| NA Not Applicable<br>FS Further Study<br>NOTE – Authentication delay refers to the overall delay as defined in 6.1.4. |                            |              |                                                                   |                                                                |
+
+# **7 History**
+
+This is the first issue of Recommendation E.774.
+
+# ITU-T RECOMMENDATIONS SERIES
+
+- Series A Organization of the work of the ITU-T
+- Series B Means of expression
+- Series C General telecommunication statistics
+- Series D General tariff principles
+- Series E Telephone network and ISDN**
+- Series F Non-telephone telecommunication services
+- Series G Transmission systems and media
+- Series H Transmission of non-telephone signals
+- Series I Integrated services digital network
+- Series J Transmission of sound-programme and television signals
+- Series K Protection against interference
+- Series L Construction, installation and protection of cables and other elements of outside plant
+- Series M Maintenance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits
+- Series N Maintenance: international sound-programme and television transmission circuits
+- Series O Specifications of measuring equipment
+- Series P Telephone transmission quality
+- Series Q Switching and signalling
+- Series R Telegraph transmission
+- Series S Telegraph services terminal equipment
+- Series T Terminal equipment and protocols for telematic services
+- Series U Telegraph switching
+- Series V Data communication over the telephone network
+- Series X Data networks and open system communication
+- Series Z Programming languages

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+
+
+# Recommendation**ITU-T E.813 (05/2024)**
+
+SERIES E: Overall network operation, telephone service, service operation and human factors
+
+Quality of telecommunication services: concepts, models, objectives and dependability planning – Models for telecommunication services
+
+# --- **Mapping and visualization strategies for the assessment of connectivity**
+
+![ITU logo](0538daaa5583c23e17db3a12f2281a55_img.jpg)
+
+The logo of the International Telecommunication Union (ITU) is located in the bottom right corner. It features a blue circular emblem with a stylized globe and the letters 'ITU' in white.
+
+ITU logo
+
+## ITU-T E-SERIES RECOMMENDATIONS
+
+### Overall network operation, telephone service, service operation and human factors
+
+|                                                                                                      |                    |
+|------------------------------------------------------------------------------------------------------|--------------------|
+| INTERNATIONAL OPERATION                                                                              | E.100-E.229        |
+| OPERATIONAL PROVISIONS RELATING TO CHARGING AND ACCOUNTING IN THE<br>INTERNATIONAL TELEPHONE SERVICE | E.230-E.299        |
+| UTILIZATION OF THE INTERNATIONAL TELEPHONE NETWORK FOR NON-<br>TELEPHONY APPLICATIONS                | E.300-E.329        |
+| ISDN PROVISIONS CONCERNING USERS                                                                     | E.330-E.349        |
+| INTERNATIONAL ROUTING PLAN                                                                           | E.350-E.399        |
+| NETWORK MANAGEMENT                                                                                   | E.400-E.489        |
+| TRAFFIC ENGINEERING                                                                                  | E.490-E.799        |
+| QUALITY OF TELECOMMUNICATION SERVICES: CONCEPTS, MODELS,<br>OBJECTIVES AND DEPENDABILITY PLANNING    | E.800-E.899        |
+| Terms and definitions related to the quality of telecommunication services                           | E.800-E.809        |
+| <b>Models for telecommunication services</b>                                                         | <b>E.810-E.844</b> |
+| Objectives for quality of service and related concepts of telecommunication services                 | E.845-E.859        |
+| Use of quality of service objectives for planning of telecommunication networks                      | E.860-E.879        |
+| Field data collection and evaluation on the performance of equipment, networks and services          | E.880-E.899        |
+| OTHER                                                                                                | E.900-E.999        |
+| INTERNATIONAL OPERATION                                                                              | E.1000-E.1999      |
+| NETWORK MANAGEMENT                                                                                   | E.4000-E.4999      |
+
+For further details, please refer to the list of ITU-T Recommendations.
+
+# Recommendation ITU-T E.813
+
+# Mapping and visualization strategies for the assessment of connectivity
+
+## Summary
+
+Mapping and visualizing connectivity of telecommunication services is crucial to the work of regulators, government entities and operators as it facilitates the decision-making process to reduce the digital divide. Recommendation ITU-T E.813 provides guidance, especially when it is needed to identify unserved and underserved areas. Moreover, connectivity should be understood not only as the telecommunications service's presence or absence, but also as a concept that should be built upon different perspectives.
+
+Recommendation ITU-T E.813 defines a high-level framework for mapping and visualization strategies that include guidelines to define first how to identify and measure the level of connectivity and secondly tools and functionalities that are useful in representing the status of this connectivity.
+
+## History \*
+
+| Edition | Recommendation | Approval   | Study Group | Unique ID          |
+|---------|----------------|------------|-------------|--------------------|
+| 1.0     | ITU-T E.813    | 2024-05-29 | 12          | 11.1002/1000/15897 |
+
+## Keywords
+
+Connectivity index, GIS, mapping, QoS, visualization.
+
+---
+
+\* To access the Recommendation, type the URL <https://handle.itu.int/> in the address field of your web browser, followed by the Recommendation's unique ID.
+
+## FOREWORD
+
+The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis.
+
+The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics.
+
+The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1.
+
+In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC.
+
+## NOTE
+
+In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some other obligatory language such as "must" and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party.
+
+## INTELLECTUAL PROPERTY RIGHTS
+
+ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process.
+
+As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents/software copyrights, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the appropriate ITU-T databases available via the ITU-T website at <http://www.itu.int/ITU-T/ipr/>.
+
+© ITU 2024
+
+All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU.
+
+## Table of Contents
+
+|                                                                                   | Page |
+|-----------------------------------------------------------------------------------|------|
+| 1 Scope .....                                                                     | 1    |
+| 2 References.....                                                                 | 1    |
+| 3 Definitions .....                                                               | 2    |
+| 3.1 Terms defined elsewhere .....                                                 | 2    |
+| 3.2 Terms defined in this Recommendation.....                                     | 2    |
+| 4 Abbreviations and acronyms .....                                                | 2    |
+| 5 Conventions .....                                                               | 2    |
+| 6 Connectivity of telecommunication services.....                                 | 3    |
+| 6.1 Assessment of connectivity .....                                              | 3    |
+| 6.2 Data tools.....                                                               | 5    |
+| 6.3 In-building assessment of connectivity .....                                  | 7    |
+| 6.4 Requirements and characteristics of mapping and visualization tools .....     | 8    |
+| 6.5 Connectivity assessment interfaces and types of views .....                   | 12   |
+| Appendix I – Use cases.....                                                       | 14   |
+| I.1 Use case 1: Accelerating infrastructure deployment.....                       | 14   |
+| I.2 Use case 2: Resolving quality of service issues .....                         | 14   |
+| I.3 Use case 3: Providing informed choices to end users in terms of services .... | 14   |
+| I.4 Use case 4: Improving transparency and governance .....                       | 14   |
+| Appendix II – Characteristics of information sources .....                        | 16   |
+| Appendix III – Construction of single-number indicators and some examples.....    | 19   |
+| Bibliography.....                                                                 | 21   |
+
+
+
+# Recommendation ITU-T E.813
+
+## Mapping and visualization strategies for the assessment of connectivity
+
+# 1 Scope
+
+In this Recommendation, the term "connectivity" is used with a broader meaning than the usual ones used in the telecommunication industry, including existing definitions in ITU-T Recommendations. Besides the basic meaning related to the state of being connected, without respect to a specific reason why, this Recommendation also takes into account the fact that, to be connected to a service, an end-user needs to see several, potentially many, criteria fulfilled, related to different dimensions that can be grouped into two big clusters:
+
+- Technical elements related to the ability of a given network and a given device to share through a physical link the information and contents needed to provide access to a service. This includes network coverage and performance, as well as device performance.
+- All other non-technical elements.
+
+Taking these two clusters, this Recommendation outlines a series of toolboxes, related to the dimensions underlying connectivity, including relevant parameters. This Recommendation also proposes strategies and guidelines:
+
+- To construct a composite connectivity index based on these toolboxes.
+- To geographically map and visualize this index or any underlying relevant parameter.
+
+These geographical mapping and visualization strategies are useful in:
+
+- Evaluating the connectivity of users to telecommunication services, by taking all or a part of the dimensions mentioned above.
+- Representing underserved as well as unserved areas, with the identification of the concerned dimensions, to determine the appropriate intervention and necessary measures needed by the end users.
+
+Appendices to this Recommendation provide guidance on spatial analysis including stratification methodologies to classify geographical areas, data granularity, data collection and post-processing mechanisms.
+
+# 2 References
+
+The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation.
+
+- [ITU-T E.802] Recommendation ITU-T E.802 (2007), *Framework and methodologies for the determination and application of QoS parameters*.
+- [ITU-T E.804] Recommendation ITU-T E.804 (2014), *Quality of service aspects for popular services in mobile networks*.
+- [ITU-T E.805] Recommendation ITU-T E.805 (2019), *Strategies to establish quality regulatory frameworks*.
+
+- [ITU-T E.805.1] Recommendation ITU-T E.805.1 (2021), *Quality of service operational strategy for improved regulatory supervision of providers of mobile telecommunication services*.
+- [ITU-T E.806] Recommendation ITU-T E.806 (2019), *Measurement campaigns, monitoring systems and sampling methodologies to monitor the quality of service in mobile networks*.
+- [ITU-T E.812] Recommendation ITU-T E.812 (2020), *Crowdsourcing approach for the assessment of end-to-end quality of service in fixed and mobile broadband networks*.
+- [ITU-T E.840] Recommendation ITU-T E.840 (2018), *Statistical framework for end-to-end network-performance benchmark scoring and ranking*.
+
+# 3 Definitions
+
+## 3.1 Terms defined elsewhere
+
+None.
+
+## 3.2 Terms defined in this Recommendation
+
+This Recommendation defines the following terms:
+
+- 3.2.1 connectivity:** Two-way access to telecommunication services related to performance and usability.
+- 3.2.2 connectivity index:** A scalar level that represents the overall degree of connectivity, evaluated at a particular time and applicable for a specific duration and geographical area.
+- 3.2.3 mapping:** The process of illustrating values or parameters in a geographic information system (GIS).
+
+# 4 Abbreviations and acronyms
+
+This Recommendation uses the following abbreviations and acronyms:
+
+|      |                                      |
+|------|--------------------------------------|
+| GIS  | Geographic Information System        |
+| H3   | Hexagonal Hierarchical Spatial Index |
+| KPI  | Key Performance Indicator            |
+| MOS  | Mean Opinion Score                   |
+| OSS  | Operations Support System            |
+| QoS  | Quality of Service                   |
+| RSCP | Received Signal Code Power           |
+| RSRP | Reference Signal Received Power      |
+
+# 5 Conventions
+
+None.
+
+# 6 Connectivity of telecommunication services
+
+## 6.1 Assessment of connectivity
+
+Assessing the level of connectivity is primarily essential in order to understand the optimal telecom services needs, opportunities, and challenges of the target community in a particular location or specific geographical area. To this end, a more holistic approach to assess connectivity can be carried out to gather information on current and future needs, perform gap and risk analysis, boost investment and ensure productivity and growth in a targeted community or in a geographic area. This holistic approach consists of obtaining an index that brings an even broader view of the connectivity status, so that it can be denominated as a connectivity index.
+
+Identifying different performance and usability levels in different geographical areas through a connectivity index can provide a better understanding for the end users service status and can lead to greater competition and investment, to the benefit of all the different stakeholders in the digital ecosystem. These connectivity index levels can provide investors with granular country-level market intelligence that highlights key intersections of telecommunication development needs. A connectivity index is a quantity that cannot be derived from a single primary measurement value. It could be represented by a group of values from different categories of data, but such a multi-dimensional array of values would be difficult to handle. Instead, a connectivity index is defined which is calculated from those values as a single number that expresses the level of connectivity available in a geographical area. Input data for this connectivity index come from multiple sources of information related to the digital ecosystem such as telecommunications infrastructure, topography, or terrain characteristics, performance indicators, regulatory aspects, demand for telecommunications services and even socio-economic statistics. It is important to emphasize that the sources of information to consider will depend on the objective of the analysis.
+
+### 6.1.1 Connectivity index
+
+A composite index can be obtained through a combination of multiple indicators identified and relevant for the target analysis using statistical methodologies. It is beneficial when a single dimensionless value is required to assess the connectivity status in simple way, so that decision makers can have a complete picture in mind. Then, concrete, targeted action plans can be derived to improve the connectivity based on an analysis of the obtained value of this composite index for the studied geographical area.
+
+For this purpose, even if there is no universal method for constructing composite indices, their construction is mainly determined by the application or question that is going to be investigated.
+
+In simple terms, a composite index is a single (scalar) number that is constructed from a set of input values. Typically, those input values come with their own ranges (e.g., a mean opinion score (MOS) scale from 1 to 5). In order to process them into a composite indicator, these values need to be normalized, i.e., brought to the same scale. Each input value has a given weight with which it contributes to the output quantity.
+
+For instance, if the output quantity is calculated as a weighted sum of normalized input values, the set of weights is chosen such that the output value has also the desired value range, e.g., 0...100.
+
+Also, typically, input values are not used linearly, but are transformed using some nonlinear function, expressing essentially an assessment. If this transformation is done by a function applied to the original input quantity, normalization can be integrated into this transformation already. For example, rather than using average income the input might be the percentage of households with an income below a certain threshold. Figure 1 shows an example of the construction of a composite index.
+
+![Diagram illustrating the construction of a composite index. Three input values (V1, V2, V3) are each processed through a 'Normalization and transformation' step (T1, T2, T3). The outputs are then weighted (Weight W1, W2, W3) and combined in a 'Weighted addition' circle to produce an 'Output value (Indicator) X'. The label E.813(24) is present in the bottom right.](a5ee5c23b6dc52ec1d724b76d5a5f58f_img.jpg)
+
+```
+
+graph LR
+    V1[Input value V1] --> T1[Normalization and transformation T1]
+    V2[Input value V2] --> T2[Normalization and transformation T2]
+    V3[Input value V3] --> T3[Normalization and transformation T3]
+    T1 -- "Weight W1" --> WA((Weighted addition))
+    T2 -- "Weight W2" --> WA
+    T3 -- "Weight W3" --> WA
+    WA --> X[Output value (Indicator) X]
+    E81324[E.813(24)]
+  
+```
+
+Diagram illustrating the construction of a composite index. Three input values (V1, V2, V3) are each processed through a 'Normalization and transformation' step (T1, T2, T3). The outputs are then weighted (Weight W1, W2, W3) and combined in a 'Weighted addition' circle to produce an 'Output value (Indicator) X'. The label E.813(24) is present in the bottom right.
+
+**Figure 1 – Example of the construction of a composite index**
+
+The following guidelines are recommended for the construction of a connectivity index that uses a set of variables (connectivity indicators) that can be obtained from the toolboxes previously described:
+
+1. Key performance indicators (KPIs) from multiple toolboxes should be selected according to the considerations defined by the objective of the analysis. The selection step is the result of a trade-off between possible redundancies caused by overlapping information and the risk of losing information.
+2. Normalization can be required as the KPI in a data set often have different measurement units. Therefore, it is necessary to bring the KPI to the same standard, by transforming them into pure and dimensionless numbers.
+3. The composite index is constructed through the combination of all the different KPI from the chosen toolboxes. For this combination, different aggregation methods are possible. The choice of the 'best' aggregation method also depends on the aim and the users of the analysis (regulators, operators, or end users).
+4. The methodology to obtain the index should be transparent and documented to allow for validation/verification of the results, and to enable analysis of the impact of each input into the composite index, i.e., helping the user of the index to identify areas of improvement which will have the greatest impact.
+5. The use of multivariate methods is suggested for the connectivity index construction. Multivariate methods allow for a deeper exploration into possible patterns that exist in the data, enable complex inter-relationships between many variables to be represented graphically, and provide ways of reducing the dimensionality of the data for summary and further analysis.
+6. Among the multivariate methods available, cluster analysis can be used to identify natural groupings amongst the sampling units so that units within each group (cluster) are similar to one another while dissimilar units are in different groups. Furthermore, when dealing with large datasets (for example, crowdsourcing information), principal component analysis (PCA) can be useful to reduce the dimensionality of the data while considering as much as possible of the variation of the original data. In this way, a smaller number of variables can summarize the data by a linear combination of the original variables.
+7. The question of the choice of a system of weights in order to weigh the individual indicators, according to their different levels of importance in expressing the considered phenomenon, necessarily involves the introduction of an arbitrary component. For example, subjective weights can be set by a group of specialists (e.g., regulators, operators, policy makers) or maybe social surveys about how important individual indicators are to the people. A suitable statistical methodology that assigns a weight depending on the variation of the data can also be used (for example, PCA).
+
+## 6.2 Data tools
+
+Assessment and evaluation of the connectivity status depend on different informational resources or data tools and targets. For example, required targets can range from new market entry, filling coverage gaps and densification related matters. Such informational resources can dimension and scale telecommunication solutions if it is according to a set target.
+
+For purposes of this Recommendation, data from different sources of information can be viewed as toolboxes.
+
+KPI obtained from data sources of information could be associated with each toolbox. The following toolboxes are suggested to begin the analysis, however the use of any or various of the toolboxes may differ according to the use case that is being investigated.
+
+### 6.2.1 Performance toolbox
+
+The performance toolbox includes KPI that measure the level of quality of service (QoS) achieved or delivered to the customer. These KPI are measurable (with instruments or observations) and allow assessment of the ability of a whole or a portion of the network to provide the functions related to communications between users, see [ITU-T E.806].
+
+KPI that could be considered, but not limited to, this toolbox, are the following:
+
+- Download/upload throughput, Packet loss, Jitter and Latency
+- Unsuccessful call ratio, Dropped call ratio, Call set up time
+- Voice MOS, Video MOS
+
+### 6.2.2 Telecom market trends toolbox
+
+Market trend analysis is an effective tool for an evolving market such as the telecommunications industry to stay and grow. Since market trends are dynamic, such analysis enables companies to identify, forecast and strategise for current and upcoming markets including market maturity and future market potential.
+
+Some KPIs relevant to this toolbox are:
+
+- Mobile users penetration (MUP) (telephony, Internet access) per neighbourhood polygon
+- Fixed users penetration (FUP) (telephony, Internet access) per neighbourhood polygon
+- The presence of any kind of service providers such as mobile operators, fixed operators, mobile virtual operators, wireless Internet service providers (ISPs)
+- Fixed broadband basket
+- Mobile cellular low-usage basket
+- Mobile broadband Internet prices per month
+- Satellite broadband Internet prices per month (if any)
+- Churn (potential revenue loss)
+
+### 6.2.3 Coverage toolbox
+
+This toolbox gathers all those metrics that help to identify those geographic areas where users can connect to a network, stay connected and reliably communicate with optimal network conditions. It is usually represented as single or multiple layers such as roads, lakes, inhabited areas, and land use, etc., see [b-ITU-T Y.4562].
+
+Some KPIs that can be considered to determine whether an area is covered:
+
+- Signal strengths: received signal level (RxLev) for GSM, received signal code power (RSCP) for UMTS and reference signal received power (RSRP) for LTE, SS-RSRP for NR
+- Availability of line-of-sight (LoS)
+
+- Availability of wired connections (optical fibre, DSL, coaxial) for Internet
+- Availability of satellite access for the Internet
+
+### **6.2.4 Telecommunications infrastructure toolbox**
+
+Infrastructure toolbox contains data related to deployed telecom infrastructure (masts and towers, optical fibre cables and other media, bandwidth and backhaul, etc.), nevertheless other kinds of infrastructure can also be considered in this toolbox.
+
+Some data that could be considered in this toolbox:
+
+- Mobile broadband technologies availability (LTE, 5G) (with the corresponding type of power supply deployed)
+- Fixed access technologies availability (optical fibre, DSL, coaxial)
+- Availability of fixed and wireless backhauling
+- Aerial accessibility via existing light poles and transmission tower infrastructure
+- Points of interconnection such as border gateway HUBs, data centres, Internet exchange point (IXP)
+- Availability of electricity (backup batteries / solar)
+- Ease of right of way for laying cable or installing pole/tower
+- Ease of right of use of existing street furniture
+
+### **6.2.5 Consumer behavioural factors toolbox**
+
+This toolbox reflects consumer behaviours that are helpful in the study of consumers and the processes they use to choose, use (consume), and dispose of telecommunications products and services. Studying consumer behaviour is important because it helps to understand what influences consumers' buying decisions, how consumers decide on a product to fill the digital divide in the market and to identify the products that are needed and the products that are obsolete.
+
+The factors relevant to this toolbox are:
+
+- Smartphones penetration
+- Computers penetration by household
+- Online shopping penetration
+- Digital financial services usage
+- Traffic and hours spent surfing Internet per consumer / by type of device
+- Internet access penetration (fixed and mobile)
+- Sensitivity to tariff
+- Sensitivity to the quality of services (based on complaints)
+
+### **6.2.6 Socio-economic factors toolbox**
+
+Socio-economic toolbox refers to classifying people by their social, economic and educational status. Examining demographics not only provides an understanding of the composition of the market area, but also, they help to understand the potential range of impacts of a proposed change and the likely responses of those impacted if the change occurs.
+
+Some KPIs that could be considered in this toolbox:
+
+- Demographic parameters: For example, age, education level, income level, number of members by household, genre, occupation, urban or rural population.
+- Business parameters: Demographic data about enterprises, number of enterprises, size of enterprise measured by the number of employees, earnings, sector, among others.
+
+- Socio-economic levels: Data that allows grouping and classifying of households based on availability of basic infrastructure (power supply grid, lighting, water, paving streets), health infrastructure, connectivity, and entertainment, among others. The level of detail available depends on each country.
+
+### 6.2.7 GIS toolbox
+
+A geographic information system (GIS) facilitates understanding patterns, relationships, and geographic context by visualizing in map forms, and remains a powerful decision-making tool that enables effective environmental, demographic, and topographic analysis. Therefore, geodata-based telecom network analysis facilitates efficient decision-making such as where network components should be placed and how they should be connected, what size components to use and how to create a strategy on meeting capacity requirements and maintaining network reliability, working conditions of a particular network, optimization of network performance, maximizing the optimal use of existing infrastructure and minimizing the cost of deployment. Thus, geodata helps to enhance telecom processes through better customer-relationship management and location services. Accordingly, the GIS toolbox will include topographic related information.
+
+Some layers of information relevant to this toolbox are:
+
+- Terrain layers
+- Topographic layers
+- Building layers (2D and 3D)
+- Regulatory aspects (Restrictions on tower heights near airports, signal level at international borders, near schools/hospital/prisons/defense establishment, rights of way, etc.)
+- Protected area layers (National parks, conservation reserves, community reserves, sanctuaries, biosphere, monuments).
+
+## 6.3 In-building assessment of connectivity
+
+Since most users spend most of their time indoors, it is important to understand the QoS in these environments. Within the buildings, QoS measurements should consider the effect of built structures and often the best way of achieving this is via direct measurement of KPIs from devices involving users in defining and achieving the optimum outcomes for themselves. With more detailed and accurate information about the building and the clutter environment, and that too in a digital format that is interoperable, such measurements would be of great help for tools predicting quality of services inside the building.
+
+Connectivity quality assessment may start from a particular spot for a variety of services to be measured at that spot. Assessment of quality in an apartment may be composed of several spots. Further assessment at building level may or may not comprise aggregation at floor level depending upon closeness of the variations across apartments on the same floor or across a floor on the same side of the tower.
+
+Indoor sample validation is an essential primary process to assess in-building connectivity, and evaluation of parametric conditions such as power signal strength indicators for different mobile radio technologies (RSCP, RSRP, SS RSRP), using validation methodologies, provides a high probability differentiation between indoor and outdoor samples. Moreover, other combination of indoor sample indicators such as sample mobility along with geospatial building polygons enhances the confidence level of indoor identification and provides beneficial use cases.
+
+Furthermore, collected samples with X, Y, Z coordinates indicate human activity at an elevation in reference to ground level. Sample validation methodologies previously mentioned can overcome the challenge and raise the confidence level to determine ground altitude as a reference for valid Z values, which can be impacted by rough terrain, location accuracy and sample size. This data can be used to
+
+develop a path to dimension and model building polygons, provide indoor coverage penetration visuality, and inform related quality assessment and optimization needs.
+
+## **6.4 Requirements and characteristics of mapping and visualization tools**
+
+Assessing the level of connectivity of any geography can take many forms, ranging from literal mapping using geographic information system tools to data collection and analysis or polling that helps a region better understand its needs and opportunities. In general, mapping tools are needed to communicate the status of connectivity in a high-quality way for different purposes and from different perspectives. Such tools enable users to visualize and understand geographic patterns, relationships, and trends.
+
+In order to support this, data needs to be linked with respective geographical information. For instance, demographic information may be related to postcode areas; in such a case geo-visualization could display this information with respect to polygons on a map; in this case data is related to a given area. It is also possible that primary data is linked to a specific point (given by e.g., GPS coordinates; locations where actual measurements showed a call drop). In such a case, visualization can either be direct (drawing respective points on a map) or data can be aggregated. In this case, the unit of aggregation would be a polygon (a tile, a postcode area, etc.) and the quantity to be visualized would be for instance a colour-coded representation of an indicator, in the example case of a call-drop rate.
+
+### **6.4.1 Map creation**
+
+The main aim is to represent on a map the multiple values of the composite index associated with different geographical areas in order to know the status of connectivity. Therefore, a connectivity assessment map must inform, in an instant, what the levels of connectivity are in a given geographical area.
+
+However, to deepen the analysis and to have a better understanding of the relationships between locations, distances, and other geographic information, the analyst could consider including other mapping layers, and filters, corresponding to data from different sources of information involved in the index calculation. Of course, this data must be linked to a specific point or geographical area.
+
+For example, some relevant layers that could support a better understanding of connectivity will be socio-economic data associated with demographic areas, network coverage or even infrastructure deployment. Data to be included will always depend on the analysis being carried out.
+
+As is well known, maps communicate information that is related to space and location in a remarkably efficient way, reducing volumes of information to a single, clear visual presentation. This is why it is advisable also to consider only those additional data that will be useful for the specific purpose and so maintain visual clarity.
+
+### **6.4.2 Visualization**
+
+Visualization is a summary term for presenting data in visual forms, such as bar graphs, pie charts, time-axis diagrams, maps, etc. For example, the visualization of geospatial data ("geo-visualization"), seeks to represent data in a form that can be more easily understood and interpreted by non-technical audiences.
+
+Based on the advantages and limitations of different map styles, some styles of maps are better at representing certain types of information than others. On the other hand, how the geospatial data is represented can affect what conclusions are drawn from it. For this reason, it is important to choose a mapping style that allows making sense of the information in order to best suit the needs.
+
+Clauses 6.4.2.1 to 6.4.2.4 present some of the methods for visualizing geospatial data that may be convenient in the right map to represent the values of the connectivity index:
+
+#### 6.4.2.1 Choropleth maps
+
+Choropleth maps offer a clear way of visualizing a metric by regional blocks. A choropleth map is made by dividing the area being mapped into geographic or political boundaries for instance, and then filling each resulting section with a different colour, representing a different range of connectivity index values. Choropleth maps are useful for visualizing clusters of data across a geographic area while maintaining the context of regional boundaries. Therefore, they can provide a useful means of highlighting which administrative groupings may require investment. Figure 2 shows an example of a choropleth map.
+
+![A choropleth map of the Atlanta metropolitan area showing population change by county. The map is color-coded from light yellow to dark red based on the percentage change in population. A legend titled 'Change in population' shows five categories: Less than -20% (light yellow), -20% to -10% (yellow), -10% to 10% (orange), 10% to 20% (dark orange), and More than 20% (red). The map includes labels for various cities and counties such as Dalton, Atlanta, and Greenville. A search bar at the top reads 'Sp... , where do people usually go on Monday during morning'.](177e8bc1c595b7fe3461d9919f87e044_img.jpg)
+
+A choropleth map of the Atlanta metropolitan area showing population change by county. The map is color-coded from light yellow to dark red based on the percentage change in population. A legend titled 'Change in population' shows five categories: Less than -20% (light yellow), -20% to -10% (yellow), -10% to 10% (orange), 10% to 20% (dark orange), and More than 20% (red). The map includes labels for various cities and counties such as Dalton, Atlanta, and Greenville. A search bar at the top reads 'Sp... , where do people usually go on Monday during morning'.
+
+**Figure 2 – Example of a choropleth map**
+
+#### 6.4.2.2 Hexagon-based maps
+
+Hexagon-based maps are a popular, useful way to view data in maps. Hexagons makes it easy for users to summarize their data on a map and they are especially helpful when looking for patterns or clusters in large amounts of point data. Hexagonal Hierarchical Spatial Index (H3) is hierarchical, so it can be subdivided into smaller grids at various resolutions. Grid systems are a better way to aggregate datapoints than postal code areas, as these areas may have unusual shapes and sizes and may change over time. Grids do not align with streets and neighbourhoods, but a group of grid cells can collectively represent such geometries.
+
+Hexagonal cells are colour-coded based on the number of datapoints they hold or the range of connectivity index values, which enable the users to easily understand patterns in their data. Figure 3 shows some examples of hexagon-based maps.
+
+![Figure 3: Three examples of hexagon-based maps. The left map shows a region with blue and grey hexagons, labeled with cities like Francistown, Serowe, Mafikeng, and Port Elizabeth. The middle map shows a dense cluster of green hexagons, labeled with cities like Maputo, Maseru, and Mbabane. The right map shows a region with orange and red hexagons, labeled with cities like Kaabong, Moroto, and Musoma.](ad29805cd4f64ad2828e14feb66de664_img.jpg)
+
+Figure 3: Three examples of hexagon-based maps. The left map shows a region with blue and grey hexagons, labeled with cities like Francistown, Serowe, Mafikeng, and Port Elizabeth. The middle map shows a dense cluster of green hexagons, labeled with cities like Maputo, Maseru, and Mbabane. The right map shows a region with orange and red hexagons, labeled with cities like Kaabong, Moroto, and Musoma.
+
+**Figure 3 – Examples of hexagon-based maps**
+
+#### 6.4.2.3 Heatmaps
+
+Heatmaps are somewhat like choropleth maps in that they use colours or shades to represent different values or value ranges. However, heatmaps present these values and ranges as a continuous spectrum, rather than as discrete cells constrained by geographical or political boundaries.
+
+In this way, a heat map is useful for more precisely visualizing patterns of high ("hot spots") and low concentrations of a variable. This can come at the cost of accuracy however as it often requires converting discrete data points into a continuous spectrum via algorithms.
+
+Therefore, heatmaps or smoothly varying maps may work well for variables that can change rapidly on small dimensional scales (such as measures of signal strength). Figure 4 shows an example of a heatmap.
+
+![A heatmap overlay on a map of the Buffalo, NY area. The heatmap shows varying intensities from low (blue) to high (red/yellow). High intensity areas are concentrated in the city of Buffalo and North Tonawanda. The map includes labels for Grand Island, North Tonawanda, Kenmore, Amherst, Lancaster, and West Seneca. A legend on the left indicates 'High' at the top (yellow/red) and 'Low' at the bottom (blue). Map controls like zoom and pan are visible on the left side.](1d529a819ad929684331c55eed6673bb_img.jpg)
+
+A heatmap overlay on a map of the Buffalo, NY area. The heatmap shows varying intensities from low (blue) to high (red/yellow). High intensity areas are concentrated in the city of Buffalo and North Tonawanda. The map includes labels for Grand Island, North Tonawanda, Kenmore, Amherst, Lancaster, and West Seneca. A legend on the left indicates 'High' at the top (yellow/red) and 'Low' at the bottom (blue). Map controls like zoom and pan are visible on the left side.
+
+A heatmap overlay on a map of the Buffalo, NY area. The heatmap shows varying intensities from low (blue) to high (red/yellow). High intensity areas are concentrated in the city of Buffalo and North Tonawanda. The map includes labels for Grand Island, North Tonawanda, Kenmore, Amherst, Lancaster, and West Seneca. A legend on the left indicates 'High' at the top (yellow/red) and 'Low' at the bottom (blue). Map controls like zoom and pan are visible on the left side.
+
+**Figure 4 – Example of a heatmap**
+
+#### **6.4.2.4 Temporal animated maps**
+
+Temporal animated maps represent information over time whereas static maps represent all of their information simultaneously. In a temporal animated map, a temporal component is added to display changes in the map. This kind of map is useful for monitoring the evolution of a connectivity index over time and to have a clear vision of the evolution of the connectivity allowing identification where and when the poorest connectivity or the highest connectivity is experienced. Figure 5 shows an example of a temporal animated map.
+
+![Figure 5: Example of temporal animated map. The top part shows a map of Portugal and Spain with numerous pink circular markers indicating data points. The bottom part shows a timeline from January 2008 to July 2014, with a bar chart representing data density over time. The current selection is 'Apr 2014 Serie 2008-2017'.](b53846f262c6904a1b45abef2e95fbd8_img.jpg)
+
+The figure displays a temporal animated map interface. The upper section is a map of the Iberian Peninsula, specifically Portugal and Spain, with a dense cluster of pink circular markers concentrated in the northern and central regions. The map includes standard interactive elements like zoom buttons, a search bar, and attribution to OpenStreetMap contributors and CARTO. The lower section is a horizontal timeline spanning from January 2008 to July 2014. Above the timeline is a bar chart where the height of each bar represents the density or frequency of data points for that specific month. A vertical black line on the timeline indicates the current position at April 2014. Above the timeline, the text 'Apr 2014 Serie 2008-2017' is displayed, along with a play/pause button icon.
+
+Figure 5: Example of temporal animated map. The top part shows a map of Portugal and Spain with numerous pink circular markers indicating data points. The bottom part shows a timeline from January 2008 to July 2014, with a bar chart representing data density over time. The current selection is 'Apr 2014 Serie 2008-2017'.
+
+**Figure 5 – Example of temporal animated map**
+
+## 6.5 Connectivity assessment interfaces and types of views
+
+Organizations and ordinary end users have different requirements and levels of understanding of connectivity assessment interfaces. Clauses 6.5.1 and 6.5.2 present considerations for connectivity assessment interface types for organizations and for ordinary end users.
+
+### 6.5.1 For organizations
+
+A connectivity assessment interface for regulators should be able to accommodate detailed performance and coverage indicators derived from different database sources, such as crowdsourcing, drive or walk testing, operator network elements such as operations support system (OSS) data, as well as databases and operator's official declarations.
+
+Such informational data can provide the ability to build composite indicators such as optimization priority, service availability, ranking and partial geo-marketing guidance. Moreover, such details shall provide regulators with deeper knowledge and amplify their regulatory capacity.
+
+Including filtering functionality in the interface will support organizations in discovering new insights into what is possible in order to define and act on policy goals and initiatives. For example, the ability to filter data from a toolbox, such as household income, may help identify priorities for investment when viewing data such as fibre network availability.
+
+### 6.5.2 For end users
+
+It is critical to develop and enhance a basic view for end user applications as the connectivity assessment interface generates raw data constantly and reflects service quality directly from users. End user applications shall be informative, simple, relevant and clear. Methodologies such as ranking, scoring, and different high-end maps per service can enhance sample generation and provide a higher quality of sample representation. It is considered as the mainstream for data generation. Hence, features such as the following are recommended to have for end users:
+
+- Locations where a subscriber can access the network, e.g., mapping network coverage
+- Ability to access a specific technology, e.g., 5G or fibre network availability
+- A measure of how consistent the network performance is, e.g., what proportion of the time does the network support a level of service that enables basic use cases (network reliability), and a general service comparison between operators
+- General performance KPIs such as throughput and latency
+- Performance metrics related to video streaming and gaming
+
+# Appendix I
+
+## Use cases
+
+(This appendix does not form an integral part of this Recommendation.)
+
+Collection and data analysis can provide substantial data for many stakeholders to ensure visuality and robustness for their decisions (business decisions, market decisions, investments decisions).
+
+The following are examples of use cases for assessing connectivity index.
+
+### **I.1 Use case 1: Accelerating infrastructure deployment**
+
+Digital divide remains a challenge in rural and remote communities. Like common goods, connectivity too is a matter of right for individuals, households, businesses, industries, and the public sector. Therefore, there is a particular attention and consideration for those who live in remote areas and who belong to vulnerable groups.
+
+Across the globe, governments, regulatory authorities and network operators are increasingly aiming to provide technology and infrastructure to bring quick and innovative solutions for complex problems related to critical sectors such as energy, health, education, transport, and agriculture. Hence, the assessment of connectivity index plays a vital role for telecommunication services deployment, digital gap reduction and economic development.
+
+## **I.2 Use case 2: Resolving quality of service issues**
+
+The quality of service plays a critical role for connectivity; consequently, an assessment of connectivity helps to focus on those geographical areas where there is a lack of quality or a quality deficiency. Ensuring the quality of services in this ever-changing environment is increasingly critical. Hence a harmonized and common approach like connectivity index assessment would enable greater quality prospects irrespective of network technologies. In this sense, the connectivity assessment could be performed considering target QoS values, for example, giving the highest connectivity score to the zones where QoS levels meet the desired thresholds.
+
+## **I.3 Use case 3: Providing informed choices to end users in terms of services**
+
+End-user choices should not solely hinge on the price factor. By utilizing reliable information on their access to networks and services, such as the connectivity index assessment, their choices can be supported by various important factors integral to the assessment of the connectivity index. Consequently, a connectivity index can empower customers to make well-informed decisions.
+
+## **I.4 Use case 4: Improving transparency and governance**
+
+Connectivity index assessment will have many useful applications in governance through improved visibility of the network, which is so far a black box.
+
+The following are some examples identified:
+
+- Market competition: Knowledge of market competition dynamics and deployment status may help in drafting better public policies and streamlining obligations. Accordingly, it is usually incorporated into operators' future licenses. Publishing measured QoS and coverage stimulates competition and steers the market in the right direction by providing users with the information that will enable them to choose the operator that best matches their needs in an objective manner.
+- Digital scorecard: Connectivity index may help to produce a digital scorecard for the country for guiding and/or anticipating deployments. It may be used by the regulator/governments to
+
+monitor operators' compliance with obligations and in stimulating competition too. It can also be used to help bolster regional digital development.
+
+- Investor guidance: Currently, an operators' network is a black box for an investor. Obtaining a better and objective understanding of operators' actual coverage in the field, and the ability to establish a diagnosis will help investors and international financial institutions to better channel their choices. Also, once investment is done, it will provide a forward-looking view of rollouts and network performance, to be able to assess the efficiency and effectiveness of the investments made.
+- Coverage gap: Connectivity index assessment will help drafting schemes for deploying networks in white areas, defining priority coverage and in increasing broadband accessibility targets. The ability to identify areas where fixed and mobile coverage is poor or non-existent which also helps public authorities establish a diagnosis of the national status quo, and in tailoring their policies to satisfy coverage needs and so reduce the digital divide and connect the unconnected.
+
+With a composite connectivity index as a score, policymakers could have access to the variables that are used to construct the index. Since these variables can represent different aspects or dimensions of the connectivity index as a whole, attention can be focused on a specific aspect and it can be seen how improving this aspect would improve the overall state rank. For example, improving education and digital skills may have a direct impact on connectivity index without having to increase or modify the signal reception or coverage. With such a framework, an analysis could be carried out to investigate the impact of each of the dimensions that are considered for the construction of the composite connectivity index.
+
+# Appendix II
+
+## Characteristics of information sources
+
+(This appendix does not form an integral part of this Recommendation.)
+
+Gathering the right data is the first step and the basis to assessing connectivity. Data analysis becomes possible through good data collection, useful granularity levels and organization. For this reason, it is essential to identify all possible relevant sources of information and to ensure the quality and accuracy of the data. The more reliable and better organized data, the more likely that it will produce valuable information that are transformable into actionable insights.
+
+Listed below are some of the main characteristics recommended when considering sources of information:
+
+- Data should be related directly or indirectly to the telecommunication services
+
+A comprehensive and multi-dimensional approach may require gathering data that targets multiple and relevant sources of information which may be directly or indirectly concerned with the telecommunication services. It may be useful to mention that [b-ITU GCR] identifies five enablers of connectivity or the meaningful dimensions of connectivity as infrastructure, device, affordability, skills, and safety and security. Some of the enablers may seem to appear as not directly linked to telecommunication variables, however, they may impact the level of connectivity.
+
+- Data should be representative of the investigated geographical area
+
+In order to have information on the connectivity status that will be comparable across the studied geographical areas, it is important that all sources of information have the same representation in the whole area. Representativeness is not about the amount of data from each source of information but the presence of each source of information in the same geographical area.
+
+An example, if the connectivity assessment is going to be performed at a municipality level, then all sources of information are preferred to have that level of granularity. The geographical level to be studied could depend on the objective of the analysis and who is carrying it out (regulators, government entities, operators, others); hence geographical areas could vary such as a small town, a suburban area, a region, or a country.
+
+It should also be considered that there are statistical techniques to account for under or over-representation of the samples available, for example, data imputation techniques can be used to increase the number of samples in some areas or sampling techniques can also be applied to avoid over-representing certain areas. Annex A of [ITU-T E.806] provides a reference to calculate the number of samples to achieve representative results.
+
+- Data should be obtained from official/collaborative initiatives.
+
+The connectivity index will be as accurate as the sources of information from which it was obtained. Official or collaborative initiatives are said to have high accuracy and wider acceptability. Access to official information such as information of central government departments or public bodies or information from network/service providers or any third party, provided that it is compliant with previously agreed rules, can improve confidence in the result obtained due to data source authenticity. In the same way, sources of information from collaborative initiatives, such as crowdsourcing data or data from any type of surveys, will have a big impact in the result obtained thanks to the amount of information gathered but also due to the quality of information collected.
+
+- Data should be obtained periodically
+
+Data analysis to assess connectivity is not a simple task and needs to be performed periodically rather than just once. Therefore, data should be tracked weekly, monthly or whatever the best frequency is for the intended target. Furthermore, data obtained periodically can be used to build a historical raw
+
+database that will allow monitoring of the evolution of the levels of connectivity through this composite index.
+
+- Data redundancy considerations
+
+As data is the basis to understand the status of connectivity, it must be carefully chosen to avoid situations where the same piece of data exists in multiple places. Data redundancy can cause inconsistency, which can provide unreliable and/or meaningless information. Besides, data redundancy may increase the size and complexity of a database making it more of a challenge to maintain. However, when data from two different sources are complementary to each other, redundancy can be useful. In this latter case, for example, when there are two datasets of KPI that contain different samples, then using both datasets will increase the number of samples available for consideration.
+
+- Granularity
+
+Considering that it is common that users have different preferences or interests according to the geographical area they live in, the granularity level is relevant when defining a criterion to segment geographical areas to identify different groups of users.
+
+A careful examination of the data structure to identify different sectors or sub-strata should be undertaken. For example, it could be decided not to combine urban and rural data due to inherent heterogeneity. In urban areas, a division of  $10 \times 10$  metres grid could be suggested to divide each square. Then, a value of connectivity could be associated to each square. While, this level of detail may be sufficient for urban areas, for rural areas, a  $1 \times 1$  kilometre division may be more appropriate due to lower KPI density, KPI availability and typically less infrastructure buildup covering larger areas.
+
+Granularity could also be determined based on the availability of datasets. For example, the census data could be available at a very granular level (for example, zip code), but socio-economic data may be available at municipality level.
+
+Therefore, it is important to perform an exploratory analysis of the data and identify the granularity level available for each of the information sources before deciding on the granularity level for the connectivity analysis.
+
+- Periodicity
+
+The dimension of periodicity should be explored when publishing results of the connectivity analysis and it would depend on the objective of the study. For example, if the connectivity analysis is intended to explore the coverage levels for different radio access technologies (4G, 5G), the periodicity considered could be based on an annual basis. However, if the analysis is intended to explore the QoS of certain regions and has the potential to influence the end users' decision when choosing their telecommunications provider, then the analysis is recommended to be published on a smaller timeframe, such as quarterly or monthly (depending on the availability of the data sources).
+
+Another example is KPIs that are collected in highways. Obtaining samples in this context is different if samples are obtained in cities where there are user concentrations. So, in the case of rural highways, longer periods of observations will be required to gather samples whereas in a city or a crowded place a shorter period could be used.
+
+In summary, for intensive and continuous data involved in connectivity assessment, a small period and therefore a small sample may be suitable. On the other hand, for data which are not likely to be repeated and are quite extensive in nature, a larger period and so a larger sample size may be required.
+
+In general, a sample should be selected so that it truly represents the behaviour of the universe, that is why, depending on the characteristics of data to be collected, the number of samples must be sufficient to be representative of the whole, otherwise the results obtained may be misleading. For example, the accuracy of the QoS KPIs representing end user's complaints must reflect all the
+
+different users' profiles in an operator's network and should represent all geographical areas that are covered or served by operators. If this is not the case, then the 'universe' (the operator's user base) would not be represented in the sample.
+
+In this sense, it is recommended to define the sample size for the different datasets that will be representative of the studied region. [ITU-T E.804] and [ITU-T E.806] provide specific guidance on choosing the relevant samples sizes.
+
+- Collection mechanisms
+
+When assessing for a connectivity index, the time dimension should be considered. This is related to the representativity of the data, which does not remain static but evolves over time. In other words, the samples that were used to obtain connectivity indicators for a reference period (for example, Q1 of year X) may not be fully representative of another period (for example, Q4 of year X). For this reason, it is important that samples are continuously monitored and updated as needed. Additionally, it is advisable that connectivity assessment is completed and published within a short time, otherwise, by the time the results are published, the characteristics, or connectivity levels, among others, may have changed.
+
+Furthermore, even if socio-economic conditions may not vary significantly over time, QoS KPIs could change continuously over time and for different geographical regions. Given this, it is advisable to collect data over a timeframe that is representative of the different conditions, for example, in the case of the signal strengths indicator, its value strongly depends on weather conditions. Therefore, to have a representative sample, it is necessary to gather measurements obtained under different weather conditions.
+
+It is also recommended to consider that data collected from crowdsourcing measurements could be used to infer the coverage conditions. However, the absence of samples in one area does not necessarily indicate a lack of service, since having no samples could indicate a remote or unpopulated area or even an area where users cannot afford the telecommunications service.
+
+# Appendix III
+
+## Construction of single-number indicators and some examples
+
+(This appendix does not form an integral part of this Recommendation.)
+
+This appendix deals with different ways the actual computation of single-number indicators is done, with focus on qualitative differences between approaches and their characteristics.
+
+There are two certainties with respect to single-number indicators: they are constructed from a number of input quantities – i.e., input is multi-dimensional – and their output is a single (not necessarily numerical) quantity, i.e., output is one-dimensional. The multi-dimensional input can be associated with a vector, and the output can be associated with a scalar. The process of creating a single-value indicator is therefore a transformation which can be anything from straightforward and simple to very complex.
+
+### Basics
+
+In the simplest case, a single-number indicator is created as a weighted sum of its component values, then mapped into the desired range. Again, the simplest way to do so is to use a scaling factor, which would typically produce a real number. If the output is to be a quantized, a set of threshold values – its number depending on the number of discrete values - will be required instead.
+
+Mathematically, this simplest case can be expressed as follows:
+
+$$Y = k \sum w_i X_i$$
+
+$Y$  is the compound indicator
+
+$k$  is the output scaling factor
+
+$X_i$  is the  $i$ th component value
+
+$w_i$  is its weight.
+
+Quantization can be expressed by a set of conditions with threshold values  $t_1, t_2$  and assigned values  $V_1, V_2, \dots$ :
+
+If  $Y < t_1$  then  $Q(Y) = V_1$
+
+Else if  $Y < t_2$  the  $Q(Y) = V_2$
+
+...
+
+Else  $Q(Y) = V_{n+1}$
+
+The behaviour of the transformation which produces the single-number indicator is fully controlled by its parameters, i.e., the weights used to compute the raw or intermediate output value, and the scaling factor or thresholds used to compute the final value. There are different ways of selecting these parameters, e.g., by 'human intervention' using some kind of reasoning, or by a data-driven approach such as machine learning.
+
+### Vulnerabilities and ways to mitigate them
+
+A general risk when using single-number indicators is that they can obscure specific, partial weaknesses of the system under consideration. An indicator value in the 'medium' range can belong to a system which has a decent if not outstanding performance in each aspect. However, as long as the indicator is based on a weighted sum of individual KPI only, the same numerical value could also be achieved if the system fails completely in one of its aspects while there is another aspect where it excels. For instance, if a mobile network has excellent properties in telephony but fails miserably in web browsing it may still achieve a decent overall rating.
+
+Example:
+
+Figure III.1 shows the resulting matrix for a simple 'weighted average' where:
+
+$$R = 0.5X + 0.5Y$$
+
+|           |          |          |          |          |          |          |          |          |          |          |           |
+|-----------|----------|----------|----------|----------|----------|----------|----------|----------|----------|----------|-----------|
+| <b>10</b> | 5        | 5.5      | 6        | 6.5      | 7        | 7.5      | 8        | 8.5      | 9        | 9.5      | 10        |
+| <b>9</b>  | 4.5      | 5        | 5.5      | 6        | 6.5      | 7        | 7.5      | 8        | 8.5      | 9        | 9.5       |
+| <b>8</b>  | 4        | 4.5      | 5        | 5.5      | 6        | 6.5      | 7        | 7.5      | 8        | 8.5      | 9         |
+| <b>7</b>  | 3.5      | 4        | 4.5      | 5        | 5.5      | 6        | 6.5      | 7        | 7.5      | 8        | 8.5       |
+| <b>6</b>  | 3        | 3.5      | 4        | 4.5      | 5        | 5.5      | 6        | 6.5      | 7        | 7.5      | 8         |
+| <b>5</b>  | 2.5      | 3        | 3.5      | 4        | 4.5      | 5        | 5.5      | 6        | 6.5      | 7        | 7.5       |
+| <b>4</b>  | 2        | 2.5      | 3        | 3.5      | 4        | 4.5      | 5        | 5.5      | 6        | 6.5      | 7         |
+| <b>3</b>  | 1.5      | 2        | 2.5      | 3        | 3.5      | 4        | 4.5      | 5        | 5.5      | 6        | 6.5       |
+| <b>2</b>  | 1        | 1.5      | 2        | 2.5      | 3        | 3.5      | 4        | 4.5      | 5        | 5.5      | 6         |
+| <b>1</b>  | 0.5      | 1        | 1.5      | 2        | 2.5      | 3        | 3.5      | 4        | 4.5      | 5        | 5.5       |
+| <b>0</b>  | 0        | 0.5      | 1        | 1.5      | 2        | 2.5      | 3        | 3.5      | 4        | 4.5      | 5         |
+|           | <b>0</b> | <b>1</b> | <b>2</b> | <b>3</b> | <b>4</b> | <b>5</b> | <b>6</b> | <b>7</b> | <b>8</b> | <b>9</b> | <b>10</b> |
+
+E.813(24)
+
+**Figure III.1 – Example of the resulting matrix for a simple 'weighted average' function**
+
+Clearly visible is the fact that very low values in one dimension still can achieve 'medium' values in the overall indicator.
+
+Therefore, the easiest way to avoid such perception gaps is of course to not only publish the resulting single-number indicator, but also its component KPI or sub-indicators, and/or also have some kind of text which provides extra information rather than just presenting the indicator value itself.
+
+If, for one or the other reason, this way is not feasible, additional rules can be defined. So far, the construction of the indicator has been strictly vertical, in the sense that dimensions do not 'interact' other than in the stage where the sum of weighted scores is computed.
+
+Whatever way is chosen: the more complex the set of parameters and rules is, the more of a need for proper 'explainability' exists.
+
+## Bibliography
+
+- [b-ITU-T Y.4562] Recommendation ITU-T Y.4562 (2021), *Functions and metadata of spatiotemporal information service for smart cities.*
+- [b-ITU GCR] International Telecommunication Union (2022), *Global Connectivity Report.*
+
+
+
+
+
+## SERIES OF ITU-T RECOMMENDATIONS
+
+|                 |                                                                                                                                                           |
+|-----------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Series A        | Organization of the work of ITU-T                                                                                                                         |
+| Series D        | Tariff and accounting principles and international telecommunication/ICT economic and policy issues                                                       |
+| <b>Series E</b> | <b>Overall network operation, telephone service, service operation and human factors</b>                                                                  |
+| Series F        | Non-telephone telecommunication services                                                                                                                  |
+| Series G        | Transmission systems and media, digital systems and networks                                                                                              |
+| Series H        | Audiovisual and multimedia systems                                                                                                                        |
+| Series I        | Integrated services digital network                                                                                                                       |
+| Series J        | Cable networks and transmission of television, sound programme and other multimedia signals                                                               |
+| Series K        | Protection against interference                                                                                                                           |
+| Series L        | Environment and ICTs, climate change, e-waste, energy efficiency; construction, installation and protection of cables and other elements of outside plant |
+| Series M        | Telecommunication management, including TMN and network maintenance                                                                                       |
+| Series N        | Maintenance: international sound programme and television transmission circuits                                                                           |
+| Series O        | Specifications of measuring equipment                                                                                                                     |
+| Series P        | Telephone transmission quality, telephone installations, local line networks                                                                              |
+| Series Q        | Switching and signalling, and associated measurements and tests                                                                                           |
+| Series R        | Telegraph transmission                                                                                                                                    |
+| Series S        | Telegraph services terminal equipment                                                                                                                     |
+| Series T        | Terminals for telematic services                                                                                                                          |
+| Series U        | Telegraph switching                                                                                                                                       |
+| Series V        | Data communication over the telephone network                                                                                                             |
+| Series X        | Data networks, open system communications and security                                                                                                    |
+| Series Y        | Global information infrastructure, Internet protocol aspects, next-generation networks, Internet of Things and smart cities                               |
+| Series Z        | Languages and general software aspects for telecommunication systems                                                                                      |

marked/E/T-REC-E.850-199210-I_PDF-E/raw.md

@@ -0,0 +1,242 @@
+
+
+![ITU logo: A globe with a lightning bolt and the letters ITU.](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg)
+
+ITU logo: A globe with a lightning bolt and the letters ITU.
+
+INTERNATIONAL TELECOMMUNICATION UNION
+
+**CCITT**
+
+THE INTERNATIONAL  
+TELEGRAPH AND TELEPHONE  
+CONSULTATIVE COMMITTEE
+
+**E.850**
+
+(10/92)
+
+**TELEPHONE NETWORK AND ISDN  
+QUALITY OF SERVICE,  
+NETWORK MANAGEMENT AND TRAFFIC  
+ENGINEERING**
+
+---
+
+**CONNECTION RETAINABILITY OBJECTIVE  
+FOR THE INTERNATIONAL  
+TELEPHONE SERVICE**
+
+![CCITT logo: A globe with the letters CCITT.](6ed175c791b5e156d9c98a8dbcc3318c_img.jpg)
+
+CCITT logo: A globe with the letters CCITT.
+
+**Recommendation E.850**
+
+---
+
+# FOREWORD
+
+The CCITT (the International Telegraph and Telephone Consultative Committee) is a permanent organ of the International Telecommunication Union (ITU). CCITT is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis.
+
+The Plenary Assembly of CCITT which meets every four years, establishes the topics for study and approves Recommendations prepared by its Study Groups. The approval of Recommendations by the members of CCITT between Plenary Assemblies is covered by the procedure laid down in CCITT Resolution No. 2 (Melbourne, 1988).
+
+Recommendation E.850 was revised by Study Group II and was approved under the Resolution No. 2 procedure on the 30th of October 1992.
+
+## --- CCITT NOTE
+
+In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized private operating agency.
+
+© ITU 1993
+
+All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU.
+
+# **CONNECTION RETAINABILITY OBJECTIVE FOR THE INTERNATIONAL TELEPHONE SERVICE<sup>2)</sup>**
+
+*(revised 1992)*
+
+## **Introduction**
+
+This Recommendation is one of a set of Recommendations, comprising Recommendations E.810, E.830, E.845, E.850 and E.855 concerned with the accessibility, retainability and integrity of telephone services.
+
+The CCITT,
+
+*considering*
+
+- (a) that “premature release” is defined in Recommendation E.800 as the event that an established connection will be released for a reason other than intentionally by any of the parties involved in the call;
+- (b) that premature release is a measure of connection retainability;
+- (c) that a prematurely released connection is considered high in annoyance as perceived by telephone users;
+- (d) that the probability of a premature release is a function of network component failure intensity and call holding time;
+- (e) that the objective should take account of the expectations and tolerances of users to the premature release impairment as well as the capabilities of current technology;
+- (f) that the objective might not be met at the present time but should be viewed as a long-term goal;
+- (g) that the objective should take into account the concerns of network planners and system designers, provide useful guidance to each, and it can be used by Administrations in a consistent way to measure connection retainability performance;
+- (h) that connection retainability is defined in Recommendation E.800,
+
+*recommends*
+
+## **1 Definitions**
+
+A **prematurely released telephone connection** is known as a cutoff call when the connection is completely broken, or
+
+- 1) when a single interruption occurs lasting for longer than ten seconds which causes the transmission quality of the connection to be unsuitable for voice communications;
+- 2) when a succession of interruptions occur lasting less than ten seconds where the product of the average duration of each interruption and the frequency of occurrence (i.e. average number of interruptions/seconds) exceeds 0.005.
+
+---
+
+1) Formerly G.181, in *Red Book*, Fascicle III.1.
+
+2) Some of the terms in this Recommendation, for example, the noun “measure”, are used in the sense of their definition given in Recommendation E.800.
+
+## 2 A measure to quantify telephone connection retainability performance
+
+The measure to be used shall be the complement of connection retainability, namely the probability of a prematurely released telephone connection when normalized to a call holding time of one minute ( $P_r$ ). The estimator of the **premature release probability** is the **premature release call ratio** ( $P_{re}$ ) which is defined as:
+
+$$P_{re} = \frac{1 - \frac{R_N}{N}}{T}$$
+
+where  $N$  is the number of telephone calls successfully established in some period of time,  $T$  is the mean call holding time in minutes and  $R_N$  is the number of telephone calls successfully completed out of such  $N$  calls (see Annex A and Annex B).
+
+## 3 Overall objective for premature release probability
+
+The provisional objective for the normalized premature release probability ( $P_r$ ) shall be such that the performance is better than the values given below:
+
+for typical international connections:
+
+$$2 \times 10^{-4} \leq P_r \leq 4 \times 10^{-4}$$
+
+for 90th percentile international connections:
+
+$$4 \times 10^{-4} \leq P_r' \leq 8 \times 10^{-4}$$
+
+for worst case international connections:
+
+$$8 \times 10^{-4} \leq P_r'' \leq 1.6 \times 10^{-3}$$
+
+*Note 1* – It is intended to establish a single value for  $P_r$ ,  $P_r'$  or  $P_r''$  in the future.
+
+*Note 2* – The typical 90th percentile and worst case connections mentioned above shall be assumed to be those hypothetical reference connections (HRXs) given in Recommendation E.830.
+
+*Note 3* – See Annex B.
+
+## 4 Allocation of the overall objective
+
+It is desirable, for planning purposes, to allocate the overall objective for a typical connection to the national systems and the international chain of the HRX. The overall objective is given by:
+
+$$P_r = P_{rn1} + P_{rn2} + P_{ri}$$
+
+where  $P_{rn1}$  and  $P_{rn2}$  are the premature release probabilities for originating and terminating national systems respectively and  $P_{ri}$  is the premature release probability of the international chain. The allocation of the overall objective to national systems and international chain shall be as follows:
+
+$$P_{rn1} = P_{rn2} = \alpha P_{ri}$$
+
+*Note 1* –  $\alpha$  is provisionally recommended as being equal to 2. Thus, for example, if:
+
+$$P_r = 3 \times 10^{-4}$$
+
+then
+
+$$P_{rn1} = P_{rn2} = 1.2 \times 10^{-4}$$
+
+and
+
+$$P_{ri} = 0.6 \times 10^{-4}$$
+
+*Note 2* – Further allocation of the overall objective to the circuits and exchanges used in a connection might also be desirable.
+
+*Note 3* – Objectives for the permissible probability of premature release of an established telephone connection in Integrated Digital Networks (IDNs) and mixed (analogue/digital) networks, due to transit digital or local and combined local/transit exchange malfunctions, are specified in the Recommendations Q.504 or Q.514.
+
+## ANNEX A
+
+(to Recommendation E.850)
+
+### Relationship between the premature release probability and its estimator
+
+The following relationship exists between the premature release probability normalized to a 1-minute holding time ( $P_r$ ) and its estimator  $P_{re}$ :
+
+$$\lim_{N \rightarrow \infty} P_{re} = \lim_{N \rightarrow \infty} \left( \frac{1 - \frac{R_N}{N}}{T} \right) = P_r, \text{ if such limit exists}$$
+
+On the other hand, for the purpose of network design, the probability of a premature release with a mean call holding time of  $T$  minutes,  $P(Z, T)$ , can be expressed using the formula
+
+$$P(Z, T) = \frac{Z}{Z + T^{-1}}$$
+
+where
+
+$$Z = \sum_{i=1}^L Z_i$$
+
+and  $Z_i$  is the average number of failures per minute of an  $i$  component in the hypothetical connection between two users as shown in Figure A-1/E.850. The connection holding time and the time between failures for the individual components are assumed to be exponentially distributed.
+
+![Diagram of a hypothetical connection with segments labeled 1, 2, 3, ..., i, ..., L. The diagram shows a horizontal line representing a connection path. At the left end, there is a telephone handset icon. The line has tick marks labeled 1, 2, 3, ..., i, ..., L. At the right end, there is another telephone handset icon. Below the right handset icon, the text 'T0203750-93' is written.](547f726730e589392f239257a833ede3_img.jpg)
+
+Diagram of a hypothetical connection with segments labeled 1, 2, 3, ..., i, ..., L. The diagram shows a horizontal line representing a connection path. At the left end, there is a telephone handset icon. The line has tick marks labeled 1, 2, 3, ..., i, ..., L. At the right end, there is another telephone handset icon. Below the right handset icon, the text 'T0203750-93' is written.
+
+FIGURE A-1/E.850
+
+### **Hypothetical connection to estimate the retainability of an established telephone connection**
+
+In practice,  $Z \ll T^{-1}$  and therefore  $P_r$  can be approximated as follows:
+
+$$P_r = P(Z, T)_{T=1} = \frac{Z}{Z + 1} \approx \frac{P(Z, T)}{T}$$
+
+Also, the following relationship exists:
+
+$$\lim_{N \rightarrow \infty} \left( 1 - \frac{R_N}{N} \right) = P(Z, T)$$
+
+## ANNEX B
+
+(to Recommendation E.850)
+
+### **A method to estimate the premature release probability for an international telephone connection**
+
+In this annex, a method is described which can be used to estimate the premature release probability for an international telephone connection.
+
+The method is based on placing end-to-end test calls, whose mean holding time is  $T$  in minutes, and observing those which are prematurely released due either to transmission or switching failures, or transmission interruptions lasting longer than ten seconds.
+
+From the results of Annex A, it follows that the simple estimator of  $P_r$  is:
+
+$$P_{re} = \frac{1 - \frac{R_N}{N}}{T}$$
+
+If it can be reasonably assumed that the occurrence or non-occurrence of a premature release for each of the test calls constitutes independent events, then the binomial sampling theory can be used to derive confidence intervals for  $P_r$ , and to determine minimum sample sizes ( $N$ ).
+
+In particular, it would be required that  $N$  be chosen such that:
+
+$$P_r \{ |(R_N/N) - P_r T| \leq e P_r T / 100 \} \geq a / 100$$
+
+where  $e$  is the estimation error in percent, and  $a$  is the confidence level in percent. Writing  $P = P_r \times T$ , it follows from the central limit theorem that, for large  $N$ ,
+
+$$\frac{(eNP)}{100} / [NP(1 - P)]^{1/2} \geq Z_a \tag{B-1}$$
+
+where  $Z_a$  is the root of the equation:
+
+$$(2/\pi)^{1/2} \int_0^{Z_a} \exp(-1/2 y^2) dy = a/100$$
+
+Neglecting terms of order  $P^2$ , the inequality (B-1) becomes:
+
+$$N \geq (100 Z_a/e)^2 / P \quad (\text{B-2})$$
+
+In this last formula,  $P$  is generally not known. As an example, however, if we have to verify that  $P$  is in conformity with the overall objectives of typical connections (see § 3), such that  $P$  is in the order of  $3 \times 10^{-4}$ , then a choice of  $a = 90\%$  and  $e = 40\%$  would lead to  $N \geq 56\,720$ .
+
+Similar calculations based on varying assumptions are reproduced in Figure B-1/E.850.
+
+Based on these results, it is proposed that for an average holding time of  $T = 1$  min,  $N = 60\,000$ . For other values of  $T$  (in minutes),  $N = 60\,000/T$ .
+
+![Figure B-1/E.850: A graph showing the relationship between the number of premature released calls (C) and the relative precision (Em) for different confidence levels (a). The x-axis is labeled 'Number of premature released calls, C (= N - R_N)' and ranges from 0 to 100. The y-axis is labeled 'Em (%)' and ranges from 10 to 400. Four curves are shown for a = 99%, 95%, 90%, and 80%. A label points to the curves: C = (Z_a/e)^2 * 100^2. The graph is labeled T0203740-93.](4279c8be6ec4ed56f4b3349be98bb426_img.jpg)
+
+The figure is a line graph with the following characteristics:
+
+- Y-axis:** Labeled 'Em (%)' with a logarithmic scale from 10 to 400. Major grid lines are at 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, and 400.
+- X-axis:** Labeled 'Number of premature released calls, C (= N - R\_N)' with a linear scale from 0 to 100. Major grid lines are at 0, 20, 40, 60, 80, and 100.
+- Curves:** Four curves are plotted, corresponding to different confidence levels  $a$ :
+  - $a = 99\%$  (top curve)
+  - $a = 95\%$
+  - $a = 90\%$
+  - $a = 80\%$  (bottom curve)
+- Annotation:** A label  $C = \left(\frac{Z_a}{e}\right)^2 \times 100^2$  has an arrow pointing to the curves.
+- Text:** 'T0203740-93' is located at the bottom right of the graph area.
+
+Figure B-1/E.850: A graph showing the relationship between the number of premature released calls (C) and the relative precision (Em) for different confidence levels (a). The x-axis is labeled 'Number of premature released calls, C (= N - R\_N)' and ranges from 0 to 100. The y-axis is labeled 'Em (%)' and ranges from 10 to 400. Four curves are shown for a = 99%, 95%, 90%, and 80%. A label points to the curves: C = (Z\_a/e)^2 \* 100^2. The graph is labeled T0203740-93.
+
+FIGURE B-1/E.850  
+Relative precision in estimating  $P_r$   
+from large samples when  $C/N = 0.1$
+
+## Bibliography
+
+TORTORELLA (M.): Cutoff calls and telephone equipment reliability, *The Bell System Technical Journal*, Vol 60, No. 8, pp. 1861-1890, 1981.