>
+- [b-T1A1/2003-075] T1A1/2003-07510 (February 2004), *Mapping between ITU-T (Y.1541/Y.1221) and 3GPP (TS 23-107) QoS Classes and Traffic Descriptors*. <>
+
+---
+
+10 T1 standards are maintained since November 2003 by ATIS.
+
+
+
+
+
+## SERIES OF ITU-T RECOMMENDATIONS
+
+| | |
+|-----------------|--------------------------------------------------------------------------------------------------|
+| Series A | Organization of the work of ITU-T |
+| 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 | 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 |
\ No newline at end of file
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new file mode 100644
index 0000000000000000000000000000000000000000..cb7e432f6cf19f6e6baeb8f681a959ec82b84e48
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+++ b/marked/Y/T-REC-Y.2025-201207-I_PDF-E/raw.md
@@ -0,0 +1,1861 @@
+
+
+I n t e r n a t i o n a l T e l e c o m m u n i c a t i o n U n i o n
+
+# ITU-T
+
+TELECOMMUNICATION
+STANDARDIZATION SECTOR
+OF ITU
+
+## Y.2025
+
+(07/2012)
+
+SERIES Y: GLOBAL INFORMATION
+INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS
+AND NEXT-GENERATION NETWORKS
+
+Next Generation Networks – Frameworks and functional
+architecture models
+
+# --- **Functional architecture of the next generation network service integration and delivery environment**
+
+Recommendation ITU-T Y.2025
+
+
+
+The logo of the International Telecommunication Union (ITU) is located in the bottom right corner. It features a blue globe with two red lightning bolts striking it. To the right of the globe, the text 'ITU' is written in a large, bold, blue font, and below it, the words 'International Telecommunication Union' are written in a smaller, blue font.
+
+ITU logo: A blue globe with red lightning bolts and the text 'ITU International Telecommunication Union'.
+
+# ITU-T Y-SERIES RECOMMENDATIONS **GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS AND NEXT- GENERATION NETWORKS**
+
+| | |
+|--------------------------------------------------------------------|----------------------|
+| GLOBAL INFORMATION INFRASTRUCTURE | |
+| General | Y.100–Y.199 |
+| Services, applications and middleware | Y.200–Y.299 |
+| Network aspects | Y.300–Y.399 |
+| Interfaces and protocols | Y.400–Y.499 |
+| Numbering, addressing and naming | Y.500–Y.599 |
+| Operation, administration and maintenance | Y.600–Y.699 |
+| Security | Y.700–Y.799 |
+| Performances | Y.800–Y.899 |
+| INTERNET PROTOCOL ASPECTS | |
+| General | Y.1000–Y.1099 |
+| Services and applications | Y.1100–Y.1199 |
+| Architecture, access, network capabilities and resource management | Y.1200–Y.1299 |
+| Transport | Y.1300–Y.1399 |
+| Interworking | Y.1400–Y.1499 |
+| Quality of service and network performance | Y.1500–Y.1599 |
+| Signalling | Y.1600–Y.1699 |
+| Operation, administration and maintenance | Y.1700–Y.1799 |
+| Charging | Y.1800–Y.1899 |
+| IPTV over NGN | Y.1900–Y.1999 |
+| NEXT GENERATION NETWORKS | |
+| Frameworks and functional architecture models | Y.2000–Y.2099 |
+| Quality of Service and performance | Y.2100–Y.2199 |
+| Service aspects: Service capabilities and service architecture | Y.2200–Y.2249 |
+| Service aspects: Interoperability of services and networks in NGN | Y.2250–Y.2299 |
+| Numbering, naming and addressing | Y.2300–Y.2399 |
+| Network management | Y.2400–Y.2499 |
+| Network control architectures and protocols | Y.2500–Y.2599 |
+| Packet-based Networks | Y.2600–Y.2699 |
+| Security | Y.2700–Y.2799 |
+| Generalized mobility | Y.2800–Y.2899 |
+| Carrier grade open environment | Y.2900–Y.2999 |
+| FUTURE NETWORKS | Y.3000–Y.3499 |
+| CLOUD COMPUTING | Y.3500–Y.3999 |
+
+*For further details, please refer to the list of ITU-T Recommendations.*
+
+## **Recommendation ITU-T Y.2025**
+
+# **Functional architecture of the next generation network service integration and delivery environment**
+
+## **Summary**
+
+Recommendation ITU-T Y.2025 defines the functional architecture of next generation network service integration and delivery environment (NGN-SIDE), which includes the definition of functional entities, reference points, service procedures and interconnection between different NGN-SIDEs.
+
+This Recommendation builds on the NGN-SIDE framework, general requirements, capabilities, and requirements related to service interfaces described in Recommendation ITU-T Y.2240.
+
+## **History**
+
+| Edition | Recommendation | Approval | Study Group |
+|---------|----------------|------------|-------------|
+| 1.0 | ITU-T Y.2025 | 2012-07-29 | 13 |
+
+## **Keywords**
+
+Functional architecture, functional entities, NGN, NGN-SIDE, reference points, resource adaptation, service creation, service delivery management, service execution, service integration.
+
+## 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 .
+
+© ITU 2013
+
+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..... | 2 |
+| 4 Abbreviations and acronyms ..... | 2 |
+| 5 Conventions ..... | 3 |
+| 6 Overview of NGN-SIDE ..... | 4 |
+| 6.1 NGN-SIDE general characteristics..... | 4 |
+| 6.2 Position of NGN-SIDE in NGN architecture ..... | 4 |
+| 6.3 Introduction to NGN-SIDE functional architecture ..... | 5 |
+| 7 Functional architecture of NGN-SIDE ..... | 7 |
+| 7.1 NGN-SIDE service creation functional group related functional entities..... | 9 |
+| 7.2 NGN-SIDE service execution functional group-related functional entities... | 12 |
+| 7.3 NGN-SIDE service delivery management functional group related
functional entities ..... | 19 |
+| 7.4 NGN-SIDE adaptation functional group related functional entities ..... | 24 |
+| 8 NGN-SIDE reference points..... | 26 |
+| 8.1 NGN-SIDE internal reference points ..... | 26 |
+| 8.2 NGN-SIDE external reference points..... | 29 |
+| 9 NGN-SIDE service procedures..... | 30 |
+| 9.1 Resource registration procedure ..... | 30 |
+| 9.2 Application development procedure..... | 31 |
+| 9.3 Application provisioning procedure ..... | 32 |
+| 9.4 Resource triggering procedure ..... | 34 |
+| 9.5 Context information-based service procedure..... | 36 |
+| 9.6 Charging procedure ..... | 37 |
+| 9.7 Application triggering procedure ..... | 39 |
+| 9.8 Procedure related to accessing resource in another NGN-SIDE ..... | 40 |
+| 10 Security considerations..... | 42 |
+| Annex A – Interconnection between different NGN-SIDEs ..... | 43 |
+| Appendix I – APIs for the NGN-SIDE functional architecture ..... | 45 |
+| Appendix II – Mapping between NGN-SIDE functional entities and NGN functional
entities..... | 46 |
+| Bibliography..... | 48 |
+
+
+
+# Recommendation ITU-T Y.2025
+
+# Functional architecture of the next generation network service integration and delivery environment
+
+# 1 Scope
+
+This Recommendation defines the functional architecture of NGN service integration and delivery environment (NGN-SIDE), which includes the definition of functional entities, reference points, service procedures and interconnection between different NGN-SIDEs.
+
+The Recommendation builds on the NGN-SIDE framework, general requirements, capabilities, and requirements related to service interfaces described in [ITU-T Y.2240].
+
+# 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 Y.2012] Recommendation ITU-T Y.2012 (2010), *Functional requirements and architecture of next generation networks*.
+- [ITU-T Y.2221] Recommendation ITU-T Y.2221 (2010), *Requirements for support of ubiquitous sensor network (USN) applications and services in the NGN environment*.
+- [ITU-T Y.2233] Recommendation ITU-T Y.2233 (2010), *Requirements and framework allowing accounting and charging capabilities in NGN*.
+- [ITU-T Y.2240] Recommendation ITU-T Y.2240 (2011), *Requirements and capabilities for next generation network service integration and delivery environment*.
+
+# 3 Definitions
+
+## 3.1 Terms defined elsewhere
+
+This Recommendation uses the following terms defined elsewhere:
+
+**3.1.1 application** [b-ITU-T Y.2261]: A structured set of capabilities, which provide value-added functionality supported by one or more services, which may be supported by an API interface.
+
+**3.1.2 application network interface** [ITU-T Y.2012]: Interface which provides a channel for interactions and exchanges between applications and NGN elements. The ANI offers capabilities and resources needed for the realization of applications.
+
+**3.1.3 application programming interface** [b-ITU-T I.312]: An API provides a set of interfaces from an application environment to an execution environment. The execution environment provides services to the application environment.
+
+**3.1.4 functional architecture** [ITU-T Y.2012]: A set of functional entities and the reference points between them used to describe the structure of an NGN. These functional entities are separated by reference points, and thus, they define the distribution of functions.
+
+**3.1.5 functional entity** [ITU-T Y.2012]: An entity that comprises an indivisible set of specific functions. Functional entities are logical concepts, while groupings of functional entities are used to describe practical, physical implementations.
+
+**3.1.6 next generation network (NGN)** [b-ITU-T Y.2001]: A packet-based network able to provide telecommunication services and able to make use of multiple broadband, QoS-enabled transport technologies and in which service-related functions are independent from underlying transport-related technologies. It enables unfettered access for users to networks and to competing service providers and/or services of their choice. It supports generalized mobility which will allow consistent and ubiquitous provision of services to users.
+
+**3.1.7 NGN service integration and delivery environment (NGN-SIDE)** [ITU-T Y.2240]: An open environment in NGN integrating resources from different domains and delivering integrated services to applications over NGN.
+
+NOTE – These domains include, but are not limited to, telecommunication domain (e.g., fixed and mobile networks), Internet domain, broadcasting domain and content provider domain.
+
+**3.1.8 NGN service stratum** [b-ITU-T Y.2011]: That part of the NGN which provides the user functions that transfer service-related data and the functions that control and manage service resources and network services to enable user services and applications.
+
+**3.1.9 NGN transport stratum** [b-ITU-T Y.2011]: That part of the NGN which provides the user functions that transfer data and the functions that control and manage transport resources to carry such data between terminating entities.
+
+**3.1.10 reference point** [ITU-T Y.2012]: A conceptual point at the conjunction of two non-overlapping functional entities that can be used to identify the type of information passing between these functional entities.
+
+NOTE – A reference point may correspond to one or more physical interfaces between pieces of equipment.
+
+## **3.2 Terms defined in this Recommendation**
+
+None.
+
+# **4 Abbreviations and acronyms**
+
+This Recommendation uses the following abbreviations and acronyms:
+
+| | |
+|------|-------------------------------------|
+| ANI | Application Network Interface |
+| API | Application Programming Interface |
+| BPEL | Business Process Execution Language |
+| CDR | Call Detail Record |
+| CP | Content Provider |
+| CPU | Central Processing Unit |
+| CSN | Converged Service Network |
+| FE | Functional Entity |
+| FTP | File Transfer Protocol |
+
+| | |
+|----------|--------------------------------------------------|
+| GUI | Graphics User Interface |
+| HTTP | Hyper Text Transfer Protocol |
+| IdM | Identity Management |
+| ISDN | Integrated Services Digital Network |
+| NGN | Next Generation Network |
+| NGN-SIDE | NGN Service Integration and Delivery Environment |
+| NNI | Network-Network Interface |
+| OSE | Open Service Environment |
+| PLMN | Public Land Mobile Network |
+| POJO | Plain Old Java Objects |
+| PSTN | Public Switched Telephone Network |
+| QoS | Quality of Service |
+| REST | Representational State Transfer |
+| SLA | Service Level Agreement |
+| SMS | Short Message Service |
+| SNI | Service Network Interface |
+| SOAP | Simple Object Access Protocol |
+| SP | Service Provider |
+| UNI | User Network Interface |
+| USN | Ubiquitous Sensor Network |
+
+# 5 Conventions
+
+In this Recommendation:
+
+**Functions:** In the context of NGN-SIDE architecture, "functions" are defined as a collection of functionalities. It is represented by the following symbol:
+
+
+
+```
+
+graph TD
+ Functions[Functions]
+
+```
+
+A rounded rectangular box containing the word 'Functions'.
+
+**Functional entity:** In the context of NGN-SIDE architecture, a "functional entity" is defined as set of one or more functions. It is represented by the following symbol:
+
+
+
+```
+
+graph TD
+ FunctionalEntity[Functional entity]
+
+```
+
+A rectangular box containing the text 'Functional entity'.
+
+**Functional group:** In the context of NGN-SIDE architecture, a "functional group" is defined as a group of related functional entities. It is represented by the symbol as "functions" shown above.
+
+**Data source:** In the context of NGN-SIDE architecture, "data source" is defined as particular source of local storage of data (e.g., repository specific to some functional entity). It is represented by the following symbol:
+
+
+
+The diagram shows a horizontal oval with the words "Data" and "source" stacked vertically inside it. This symbol represents a data source in the NGN-SIDE architecture.
+
+Symbol for Data source: an oval containing the text 'Data source'.
+
+# 6 Overview of NGN-SIDE
+
+## 6.1 NGN-SIDE general characteristics
+
+NGN-SIDE [ITU-T Y.2240] provides an environment for service creation, service execution, and service delivery management in order to support the integration of capabilities from different domains over NGN. NGN-SIDE also provides resource brokering and resource adaptors capabilities.
+
+The general characteristics of NGN-SIDE are described as follows:
+
+- 1) NGN-SIDE provides exposure of resources (including service enabler, content, applications and virtualized resources) from different domains (NGN, fixed networks (e.g., PSTN/ISDN), mobile networks (e.g., PLMN), Internet, content providers, broadcast networks (e.g., cable networks, etc.) to applications in a secure and controlled way.
+- 2) NGN-SIDE provides a service creation environment including capabilities for application development, resource repository, and testing environment.
+- 3) NGN-SIDE provides a configurable, scalable, reliable and virtualized service execution environment including capabilities for resource registration, access control, static and dynamic service orchestration capability, resource manager, and service dispatching.
+- 4) NGN-SIDE provides a manageable and configurable service delivery management environment including capabilities for the management of role related information, charging, context management, content management, policy management, application provisioning.
+- 5) NGN-SIDE provides capabilities for resource brokering and resource adaptor including adaptors for NGN and adaptors for non-NGN.
+- 6) NGN-SIDE provides mechanisms to support USN applications [ITU-T Y.2221].
+
+## 6.2 Position of NGN-SIDE in NGN architecture
+
+Figure 6-1 shows position of service integration and delivery environment in NGN functional architecture [ITU-T Y.2012].
+
+
+
+Y.2025(12)\_F6-1
+
+--- Control — Media - - - Management - - - IdM
+
+Figure 6-1: The position of NGN-SIDE in NGN architecture. This diagram illustrates the functional architecture of NGN-SIDE within the NGN. At the top is the 'Applications' layer. Below it is the 'Service Stratum' (green box), which contains 'Application support functions and service support functions' and 'Service control and content delivery functions'. The latter includes 'Service user profiles', 'Service control functions', and 'Content delivery functions'. Below the Service Stratum is the 'Transport Stratum' (yellow box), which contains 'Transport control functions' (including 'Network attachment and control functions', 'Mobility management and control functions', and 'Resource and admission control functions') and 'Transport functions'. On the left, 'Management functions' (pink bar) and 'End-user functions' (white box) are connected to the Service Stratum via 'UNI' (User Network Interface). 'IdM functions' (yellow box) are connected to the Service Stratum via 'ANI' (Application Network Interface). On the right, 'Functions from other service providers' and 'Functions from other networks' are connected to the Service Stratum via 'SNI' (Service Network Interface) and 'NNI' (Network Network Interface). A legend at the bottom indicates: Control (dashed line), Media (solid line), Management (dashed line), and IdM (dashed line).
+
+**Figure 6-1 – The position of NGN-SIDE in NGN architecture**
+
+As shown in Figure 6-1, NGN-SIDE functions reside in the NGN service stratum [ITU-T Y.2012].
+
+## 6.3 Introduction to NGN-SIDE functional architecture
+
+Figure 6-2 shows the general architecture of NGN-SIDE. The detailed functional architecture is specified in clause 7.
+
+
+
+Figure 6-2 – NGN-SIDE functional architecture overview. The diagram shows a central NGN-SIDE architecture box divided into two layers. The top layer is the 'NGN-SIDE integration layer' containing three functional groups: 'Service creation functional group' (red), 'Service execution functional group' (blue), and 'Service delivery management functional group' (yellow). The bottom layer is the 'NGN-SIDE adaptation layer' containing a single functional group: 'Resource adaptation functional group' (purple). External components interact with these layers: 'Application development functions', 'Applications', and 'Content provider functions' connect to the integration layer; 'Billing domain' and 'Administration functions' connect to the right side of the integration layer; and 'Resources in NGN/Non-NGN' connect to the adaptation layer. A reference code 'Y.2025(12)\_F6-2' is located at the bottom right of the diagram.
+
+**Figure 6-2 – NGN-SIDE functional architecture overview**
+
+As shown in Figure 6-2, applications, application development functions, content provider functions, billing domain, administration functions and resources in NGN/non-NGN interact with NGN-SIDE.
+
+### 6.3.1 NGN-SIDE functions
+
+In line with [ITU-T Y.2240], NGN-SIDE architecture is composed of two layers:
+
+- NGN-SIDE integration layer
+- NGN-SIDE adaptation layer.
+
+NGN-SIDE integration layer supports the following functional groups:
+
+- service creation functional group
+- service execution functional group
+- service delivery and management functional group.
+
+The service creation functional group provides entities to realize an application development environment for application developers. Application developer interacts with service creation functional group to create applications.
+
+The service execution functional group provides entities to support the service execution environment. Service execution receives requests from applications and executes service requests.
+
+The service delivery management functional group provides management support for ensuring proper functioning of the service creation and service execution functional groups and providing associated delivery functionalities.
+
+The NGN-SIDE adaptation layer supports resource adaptation functional group which provides entities to realize resource brokering and resource adaptors. The resource brokering function identifies the appropriate resources from the NGN-SIDE resource based on NGN-SIDE users' request and mediates among resources and applications. The resource adaptor function performs
+
+adaptation of resources from the NGN-SIDE resource provider. The adaptation functional group interacts with different resources offered by NGN and non-NGN.
+
+### **6.3.2 Functions external to NGN-SIDE**
+
+An application developer accesses the FEs in the service creation functional group via application development functions in order to create and test applications.
+
+When an (in-house or third party) application intends to consume the resources integrated in NGN-SIDE, the application sends a resource request to the service execution functional group. The service execution functional group interacts with the related FEs in the service execution functional group and service delivery management functional group to retrieve information related to the processing of request accessing resource in NGN and/or non-NGN.
+
+The resource request is sent to the adaptation functional group to invoke the requested resource. The adaptation functional group brokers and adapts the appropriate resource.
+
+After the resource execution is finished, the response is sent back to the application via the service execution functional group.
+
+The content provider functions enable content provider to make available different types of content to NGN-SIDE.
+
+The billing domain receives and processes charging information from the NGN-SIDE charging functions. As a business support function, the billing domain is outside the NGN-SIDE functional architecture.
+
+The administration functions enable administrator to perform several functions including content management and application life cycle management.
+
+# **7 Functional architecture of NGN-SIDE**
+
+This clause specifies the NGN-SIDE functional architecture with the description of the NGN-SIDE functional entities (FEs) being provided in the following sub-clauses. The description of the NGN-SIDE reference points is provided in clause 8.
+
+The functional architecture of NGN-SIDE is shown in Figure 7-1.
+
+
+
+The diagram illustrates the NGN-SIDE detailed functional architecture, showing the interaction between various functional groups and external domains.
+
+**External Domains and Interfaces:**
+
+- Application development functions:** Interfaces include $I_{ADF-TE}$ and $I_{ADF-ADS}$ .
+- Applications:** Interface is $I_{APP-AC}$ .
+- Billing domain:** Interface is $I_{BD-CH}$ .
+- Content provider functions:** Interface is $I_{CPF-CNM}$ .
+- Administration functions:** Interfaces include $I_{ADM-CNM}$ and $I_{ADM-AP}$ .
+- NGN resources:** Interface is $I_{RA-NGN}$ .
+- Non-NGN resources:** Interface is $I_{RA-NNGN}$ .
+
+**Internal Functional Groups and Interfaces:**
+
+- Service creation functional group (Red):** Contains Application development support FE, Testing environment FE, and Resource repository FE. Interfaces include $I_{ADS-RR}$ , $I_{TE-ADS}$ , and $I_{RR-RE}$ .
+- Service execution functional group (Blue):** Contains Access control FE, Service orchestration FE, Service dispatcher FE, Policy decision FE, Resource manager FE, Resource routing FE, and Resource registry FE. Interfaces include $I_{SD-CXM}$ , $I_{SO-CXM}$ , $I_{ADS-CNM}$ , $I_{ADS-CXM}$ , $I_{ADS-AP}$ , $I_{AC-SD}$ , $I_{SO-ADS}$ , $I_{SD-SO}$ , $I_{SD-PD}$ , $I_{RB-SD}$ , $I_{SD-ROU}$ , $I_{SD-RR}$ , $I_{RR-ROU}$ , $I_{RR-RA}$ , $I_{RB-RR}$ , $I_{RB-RA}$ , $I_{RR-RA}$ , $I_{RB-CH}$ , and $I_{RB-CXM}$ .
+- Service delivery management functional group (Yellow):** Contains Charging FE, Management of role related information FE, Policy management FE, Application provisioning FE, and Context management FE. Interface is $I_{RB-AP}$ .
+- Resource adaptation (Purple):** Contains Resource brokering FE and Resource adaptor FE. Interface is $I_{RA-NGN}$ .
+- Content management FE (Yellow):** Interface is $I_{ADM-CNM}$ .
+
+**NGN-SIDE reference architecture**
+
+Y.2025(12)\_F7-1
+
+Figure 7-1 – NGN-SIDE detailed functional architecture diagram showing the interaction between various functional groups and external domains.
+
+Figure 7-1 – NGN-SIDE detailed functional architecture
+
+The service creation functional group enables application developers to create and test applications. The service creation functional group includes the following functional entities:
+
+- application development support FE
+- testing environment FE
+- resource repository FE.
+
+Service execution functional group enables applications to access exposed resources. Service execution functional group includes the following functional entities:
+
+- access control FE
+- policy decision FE
+- resource manager FE
+- service dispatcher FE
+- service orchestration FE
+- resource routing FE
+- resource registry FE.
+
+The service delivery management functional group supports service execution and service creation mechanisms. The service delivery management functional group interacts with different external functions such as content provider functions, administration functions and billing domain for content handling, administrative and billing, respectively. The service delivery management functional group includes the following functional entities:
+
+- content management FE
+- management of role related information FE
+- policy management FE
+- application provisioning FE
+- charging FE
+- context management FE.
+
+The adaptation functional group performs resource mediation and adaptors function to access resource in different domains as well as enables different resources to interact with applications. Adaptation functional group includes the following functional entities:
+
+- resource brokering FE
+- resource adaptor FE
+
+## **7.1 NGN-SIDE service creation functional group related functional entities**
+
+### **7.1.1 Application development support FE**
+
+The application development support FE enables application developers to develop applications using resources exposed by NGN-SIDE.
+
+Figure 7-2 shows a functional view of application development support FE.
+
+
+
+```
+
+graph TD
+ A[Application development support FE]
+ B[Resource repository FE] --- A
+ C[Testing environment FE] --- A
+ D[Content management FE] --- A
+ E[Context management FE] --- A
+ F[Service orchestration FE] --- A
+ subgraph A_Box [Application development support FE]
+ G[Developer access]
+ H[Design tools]
+ I[Developer community]
+ end
+
+```
+
+Figure 7-2 – Application development support FE functional view. The diagram shows a central 'Application development support FE' box containing 'Developer access', 'Design tools', and 'Developer community'. It is connected to 'Resource repository FE' and 'Testing environment FE' on the left, and 'Content management FE' and 'Context management FE' on the right. A 'Service orchestration FE' box is connected below the central box.
+
+**Figure 7-2 – Application development support FE functional view**
+
+Application developers can access this FE to develop applications using online and/or offline design tools. The design tools facilitate application development and provide functions including drag and drop, automatic code generation, etc. When developing an application, the application development support FE interacts with the resource repository FE to achieve the development interface information of the resources used in the application, and also interacts with the content management FE to achieve the information of the content used in the application.
+
+For the applications requiring context awareness information, the context management FE exposes the related context information which is used in the application creation procedure.
+
+Developers also can develop composite resources with the application development support FE. Composite resources are stored in the service orchestration FE to be accessible as a resource for other applications.
+
+The developer community function in this FE is an optional functionality which supports a developer forum to discuss and exchange their ideas, and support collection and exposure of customer feedback and ratings about applications, ratings about resources and tools, and provide self-service functions. Furthermore, the developer community provides an entrance for developers to NGN-SIDE. It supports functions of developer registration. In addition, developers can use it to download development documents.
+
+NOTE – The capability of the developer community function can be offered by an independent web portal service. This Recommendation assumes this function is integrated into NGN-SIDE.
+
+### **7.1.2 Resource repository FE**
+
+The resource repository FE provides functionalities for the storage of resource interface description information related to the resources. Application developers use the resource interface to create applications.
+
+Figure 7-3 shows a functional view of resource repository FE.
+
+
+
+```
+
+graph TD
+ A[Application development support FE] --- B[Resource repository FE]
+ subgraph B [Resource repository FE]
+ C([Information repository])
+ D[Version management]
+ end
+ B --- E[Resource registry FE]
+
+```
+
+Figure 7-3: Resource repository FE functional view. The diagram shows a central 'Resource repository FE' box containing an 'Information repository' oval and a 'Version management' rounded rectangle. Above it is an 'Application development support FE' box connected by a vertical line. To its right is a 'Resource registry FE' box connected by a horizontal line.
+
+**Figure 7-3 – Resource repository FE functional view**
+
+The resource repository FE interacts with the resource registry FE for getting resource interface description information.
+
+When a resource is registered to the resource registry, the resource information related to application development such as resource interface description information is stored in the resource repository. The resource interface is exposed to application developers.
+
+The resource repository FE also provides resource version management mechanism to keep synchronization of resource information registered at resource registry FE.
+
+### 7.1.3 Testing environment FE
+
+Figure 7-4 shows a functional view of testing environment FE.
+
+
+
+```
+
+graph TD
+ A[Testing environment FE] --- B[Application development support FE]
+ subgraph A [Testing environment FE]
+ C[Developer access]
+ D[Application test]
+ E[Test analyze]
+ end
+
+```
+
+Figure 7-4: Testing environment FE functional view. The diagram shows a central 'Testing environment FE' box containing three rounded rectangles: 'Developer access' at the top, 'Application test' at the bottom left, and 'Test analyze' at the bottom right. Below it is an 'Application development support FE' box connected by a vertical line.
+
+**Figure 7-4 – Testing environment FE functional view**
+
+Application developers can access this FE to test the created application to ensure its normal running before the application is published. The testing operations include tracing and debugging.
+
+The developer access function can check the developer's access permission and provide a GUI including an overview of the developer's own application such as latest test status.
+
+After the developer's access, the application test function provides:
+
+- 1) Multiple simulation roles including network, applications, end users, etc.
+- 2) Online/offline testing tools for tracing and debugging
+- 3) Real-world network uncertainties simulation, e.g., variable response time delays
+- 4) Configuration of individual subscriber and large groups of subscribers for simulation
+- 5) Traffic monitoring capability between application and simulator
+
+The test analysis function can provide a testing report for the developers to get detailed information, and may highlight some part with suggestions which generated automatically.
+
+The testing environment FE interacts with the application development support FE to provide simulation of resources exposed by NGN-SIDE for application developers to test their applications.
+
+NOTE – Application testing activities should not impact the regular operations of NGN-SIDE.
+
+## **7.2 NGN-SIDE service execution functional group-related functional entities**
+
+### **7.2.1 Resource registry FE**
+
+The resource registry FE provides resource registration, resource discovery and resource governance functionalities. Additionally, it maintains a catalogue of the registered resources.
+
+Figure 7-5 shows a functional view of resource registration FE.
+
+
+
+```
+graph TD
+ SD[Service dispatcher FE] --- RR[Resource registry FE]
+ RR --- RR_R[Resource registrar]
+ RR --- RR_D[Resource discovery]
+ RR --- RR_G[Resource governance]
+ RR --- RC([Resource catalog])
+ RR --- RR_Routing[Resource routing FE]
+ RR --- RR_Repository[Resource repository FE]
+ RR --- RR_Brokering[Resource Brokering FE]
+ RR --- CM[Context Management FE]
+ RA[Resource adaptor FE] --- RR
+```
+
+The diagram illustrates the functional view of the Resource registry FE. It is a central green box containing four sub-functions: Resource registrar, Resource discovery, Resource governance, and Resource catalog (represented by an oval). The Resource registry FE is connected to several external functional entities (FEs): Service dispatcher FE (top), Resource routing FE (left), Resource repository FE (bottom-left), Resource Brokering FE (right), Context Management FE (bottom-right), and Resource adaptor FE (bottom). The Resource registrar and Resource discovery sub-functions are connected to the Resource routing FE and Resource repository FE respectively. The Resource governance sub-function is connected to the Resource Brokering FE and Context Management FE respectively. The Resource catalog sub-function is connected to the Resource adaptor FE.
+
+Functional view of the Resource registry FE
+
+**Figure 7-5 – Resource registry FE functional view**
+
+The resource registrar function processes the resource registration request from resource providers. The resource information is stored in resource catalogue. When the resource needs unregistration, the resource registrar removes the subscription of the resource from the local catalogue and notifies the resource repository FE, resource brokering FE and resource adaptor FE accordingly.
+
+During the resource registration process, the resource registry interacts with the resource adaptor FE and the resource repository functional entity.
+
+When the resource is registered at the resource registry FE, the resource registry FE:
+
+- sends an adaptation request including resource registration information towards the resource adaptor FE to set up a corresponding adaptation function for this resource;
+- sends resource interface description information to the resource repository FE to store an interface description for application development purposes;
+- sends resource information to the resource brokering FE and the resource brokering FE schedules resources accordingly;
+- provides resource routing-related information to the resource routing FE.
+
+When the service dispatcher FE sends a request to query resource registration information, the resource discovery function consults the resource catalogue to locate the requested resource according to the resource information received and sends the outcome accordingly.
+
+The resource governance function manages resource life cycle and synchronizes information with context management FE.
+
+### 7.2.2 Access control FE
+
+The access control capability provides translation of APIs/protocols across different NGN-SIDE service interfaces as well as access from applications to functionalities and/or resources exposed by NGN-SIDE [ITU-T Y.2240].
+
+The access control FE includes the following sub-functions:
+
+- API/Protocol translation
+- Authentication and authorization
+- Relaying request/response
+- Triggering charging event.
+
+Figure 7-6 shows a functional view of the access control FE.
+
+
+
+```
+graph TD
+ subgraph AC_FE [Access control FE]
+ APT[API/Protocol translation]
+ TCE[Triggering charging event]
+ AA[Authentication/authorization]
+ RRR[Relaying request/response]
+ end
+ MRF[Management of role related information FE] --- AC_FE
+ SOFE[Service orchestration FE] --- AC_FE
+ AC_FE --- CF[Charging FE]
+ AC_FE --- SDFE[Service dispatcher FE]
+```
+
+The diagram illustrates the functional view of the Access control FE. It is a central green box containing four sub-functions: API/Protocol translation, Triggering charging event, Authentication/authorization, and Relaying request/response. To the left, two boxes labeled 'Management of role related information FE' and 'Service orchestration FE' are connected to the central box. To the right, a box labeled 'Charging FE' is connected. Below the central box, a box labeled 'Service dispatcher FE' is connected.
+
+Functional view of the Access control FE
+
+**Figure 7-6 – Access control FE functional view**
+
+The API/protocol translation function translates the message request from the relevant service API and subsequently the authentication/authorization function authenticates and/or authorizes the message request with the interaction of management of role-related information FE. After authentication/authorization, the triggering charging event sends the charging-related information to the charging FE and finally, the relaying request/response function forwards the request to the service dispatcher FE or towards applications.
+
+#### API/Protocol translation
+
+This function parses the requests as received from different applications to perform different actions including request authentication, authorization and charging-related functions.
+
+#### Authentication and authorization
+
+This function authenticates and authorizes the requests from applications with the interaction of management of the role-related information FE.
+
+This sub-function also interacts with the IdM function in NGN to achieve end user, application and service-related identity information for authentication and authorization.
+
+The request is authenticated to identify the application identity securely and further authorized (e.g., the request needs to consume protected resources controlled by the resource provider which has the right of granting application X access to the resource) according to the approval of the resource provider and service level agreements (SLAs).
+
+##### Triggering charging event
+
+This function interacts with charging FE to perform different charging functions.
+
+In case of online charging, this function will support mechanisms to trigger charging events. In case of offline charging, this function will support mechanisms to generate and deliver CDRs to the charging FE.
+
+#### Relaying request/response
+
+This function is responsible for forwarding:
+
+- the request/response from application towards target resource
+- the request/response from resource towards the target application.
+
+### 7.2.3 Policy decision FE
+
+The policy decision FE performs all policy rule evaluation related functions. The policy decision FE includes two sub-functions: decision making and synchronization. Additionally, the policy decision FE provides storage for the policies.
+
+Figure 7-7 shows the policy decision FE functional view.
+
+
+
+```
+graph LR
+ subgraph PDCF [Policy decision FE]
+ DM[Decision making]
+ S[Synchronization]
+ PS([Policy storage])
+ end
+ SDF[Service dispatcher FE] --- PDCF
+ SOF[service orchestration FE] --- PDCF
+ PMF[Policy management FE] --- PDCF
+ RMF[Resource manager FE] --- PDCF
+ PDCF --- RBF[Resource brokering FE]
+```
+
+The diagram illustrates the functional view of the Policy decision FE. It is a central green box containing three sub-functions: 'Decision making' (a rounded rectangle), 'Synchronization' (a rounded rectangle), and 'Policy storage' (an oval). To the left of the central box are two external boxes: 'Service dispatcher FE' and 'service orchestration FE', both connected to the central box by horizontal lines. To the right are two external boxes: 'Policy management FE' and 'Resource manager FE', also connected by horizontal lines. Below the central box is a single external box 'Resource brokering FE', connected by a vertical line.
+
+Figure 7-7: Policy decision FE functional view diagram
+
+**Figure 7-7 – Policy decision FE functional view**
+
+Policies include SLAs between NGN-SIDE users and NGN-SIDE resources, end user's preferences and in-house application's resource requirements (related to computing, connectivity and storage resources).
+
+The policy decision FE synchronizes the policies from the policy management FE, and stores the policies in policy storage.
+
+The service dispatcher FE, the service orchestration FE and the resource brokering FE interact with the decision making function of the policy decision FE to acquire the policy decision making results. The service dispatcher FE, the service orchestration FE and the resource brokering FE enforce the policies according to policy decision result. The resource manager FE also interacts with the policy decision FE to manage resources for in-house applications.
+
+### 7.2.4 Resource manager FE
+
+The resource manager performs the controlling functions for all resources in order to satisfy the application's requirements. During the deployment of NGN-SIDE in-house applications, the application provisioning capability communicates with the resource manager which assigns the resources (including computing, connectivity, and storage) internal to NGN-SIDE according to the application's requirements (SLAs) and the NGN-SIDE provider's policies [ITU-T Y.2240].
+
+Figure 7-8 shows a resource manager FE functional view.
+
+The resource manager includes the following sub-functions:
+
+- Resource creation
+- Resource allocation
+- Resource release
+- Resource tracking and statistical analysis.
+
+
+
+```
+graph LR; PD[Policy decision FE] --- RM[Resource manager FE]; AP[Application provisioning FE] --- RM; RM --- C[Charging FE]; subgraph RM [Resource manager FE]; RC[Resource creation]; RA[Resource allocation]; RR[Resource release]; RTS[Resource tracking and statistical analysis]; end
+```
+
+The diagram illustrates the functional view of the Resource manager FE. It is a central green box containing four sub-functions: Resource creation, Resource allocation, Resource release, and Resource tracking and statistical analysis. To the left, two boxes labeled 'Policy decision FE' and 'Application provisioning FE' are connected to the central box by lines. To the right, a box labeled 'Charging FE' is connected to the central box by a line.
+
+Figure 7-8 – Resource manager FE functional view diagram
+
+**Figure 7-8 – Resource manager FE functional view**
+
+#### Resource creation
+
+Resource creation enables the creation of a resource pool. This function is responsible for resource profiling, including CPU profile, memory profile, network profile and storage profile, according to a resource template, so that different resources can be allocated to different applications in a consistent and systematic way.
+
+#### Resource allocation
+
+Resource allocation enables the provisioning of resources to applications, including CPU, memory, network and storage resources, among multiple applications on an application server according to defined policies.
+
+#### Resource release
+
+When an application is uninstalled, the related resources are released. As a result, these resources are added to the resource pool.
+
+#### Resource tracking and statistical analysis
+
+Resource tracking keeps runtime information about resources in the resource pool, such as available resources at any point of time. Resource information is updated when a particular resource is allocated or released.
+
+Resource statistical analysis is an optional capability which shows the information of a resource's usage at regular intervals. It supports multidimensional analysis, such as all resources' usage by one application, all resources' usage by one application provider, CPU's usage by all applications, memory's usage by all applications, etc.
+
+NOTE – This Recommendation assumes that the resource statistical analysis, which can be an independent capability outside NGN-SIDE, is integrated into NGN-SIDE.
+
+### 7.2.5 Service dispatcher FE
+
+This capability provides unified message routing and message exchange mechanisms within NGN-SIDE [ITU-T Y.2240]. Message routing and message exchange mechanisms deal with varying qualities of service, depending on application needs, resource performance and resource policies.
+
+Figure 7-9 shows the service dispatcher FE functional view.
+
+Service dispatcher includes the following sub-functions:
+
+- Message routing
+- Message transformation
+- Message exception handling
+- Service logic parsing and processing.
+
+
+
+```
+graph TD
+ AC[Access control FE] --- SD[Service dispatcher FE]
+ CM[Context management FE] --- SD
+ RR[Resource registry FE] --- SD
+ PD[Policy decision FE] --- SD
+ SD --- RRouting[Resource routing FE]
+ SD --- SOP[Service orchestration FE]
+ SD --- RB[Resource brokering FE]
+```
+
+The diagram illustrates the functional view of the Service dispatcher FE. It is a central green box containing four sub-functions: Message routing, Message exception handling, Message transformation, and Service logic parsing and processing. This central box is connected to several external Functional Elements (FEs): Access control FE (top), Context management FE (left), Resource registry FE (left), Policy decision FE (left), Resource routing FE (right), Service orchestration FE (right), and Resource brokering FE (bottom).
+
+Figure 7-9 – Service dispatcher FE functional view diagram
+
+**Figure 7-9 – Service dispatcher FE functional view**
+
+#### Message routing
+
+A request message from an application is passed through the access control FE. The message routing function conducts route calculation for requests and responses between NGN-SIDE users and NGN-SIDE resource providers. For selecting a proper resource, the service dispatcher FE accesses information in policy decision FE, resource registry FE, resource routing FE and context management FE. With the resource information, context information and the policy information, the message routing function supports various strategies such as static/deterministic routing, dynamic
+
+routing, content-based routing, rule-based routing, context-based routing, policy-based routing and so forth.
+
+When the destination FE is determined, a new message (using common message structure) is generated and sent to the target functional element. The target functional element could be resource brokering FE for the downward invocation of resources, and also access control FE for the upward triggering of applications. When the resource is a composite resource, the message routing function will interact with service orchestration FE several times for the sequential request of resources. This function is also responsible for maintaining correlations between requests and responses.
+
+#### **Message transformation**
+
+This function is responsible for converting a service request enclosed in an API to common message structure when service request is sent towards a target resource, and converting a common message structure back to the API used by the application when service request is sent towards a target application.
+
+#### **Message exception handling**
+
+When message handling errors occur, the message exception handling function tries to resolve them by interacting with the resource registry FE, context management FE and the policy decision FE. The message exception handling function sends back an exception message to the application that owns the error, and asks the resource registry FE to update the state of the resources.
+
+#### **Service logic parsing and processing**
+
+The application sends the request to NGN-SIDE. This request could be composed of two parts: the normal resource request and the description of the application's service logic. When the resource request includes the service logic of the application, the service logic parsing and processing function is responsible for:
+
+- parsing the service logic of the application which sends the request for resource invocation;
+- processing the request in terms of fetching the status information of the resources requested in the service logic from the context management FE and handling the corresponding procedures according to the acquired status information.
+
+When the resources used in the application service logic are concrete resources (i.e., resources provided by the resource provider and directly exposed by NGN-SIDE) and applications indicate explicitly the resource to be triggered, the service logic parsing and processing function checks the availability of these resources according to the received resource status information. If any of the concrete resources is not available, this function will end the service logic execution and send a failure notification to the application. If all the concrete resources used in the service logic are available, the service logic execution continues.
+
+When one of the resources used in the service logic is an abstract resource (i.e., integrated and exposed by NGN-SIDE and could be triggered as one of multiple concrete resources with similar function provided by different resource providers) and NGN-SIDE chooses one of these resources to be triggered, the service logic parsing and processing function checks the availability of these resources according to the received resource status information. When none of the concrete resources which belong to the same abstract resource is available, this function will end the service logic execution and send a failure notification to the application. When at least one or more concrete resources which belong to the same abstract resource are available and other concrete resources used in the service logic other than this abstract resource are available, the service logic execution continues.
+
+### 7.2.6 Service orchestration FE
+
+The service orchestration FE enables a collaboration of multiple services (resources) based on their interaction with one another at the message level. This FE consists of two functions and one data source: service composition, composite service execution and service logic repository.
+
+Figure 7-10 shows a functional view of the service orchestration FE.
+
+
+
+```
+graph LR; ADSE[Application development support FE] --- SOFE[Service orchestration FE]; SOFE --- SDFE[Service dispatcher FE]; subgraph SOFE [Service orchestration FE]; SC[Service Composition]; CSE[Composite Service Execution]; SLR([Service logic repository]); end
+```
+
+The diagram illustrates the functional view of the Service orchestration FE. It is a central green box labeled "Service orchestration FE" containing three components: "Service Composition", "Composite Service Execution", and "Service logic repository" (represented as an oval). To the left of this box is a green box labeled "Application development support FE", and to the right is a green box labeled "Service dispatcher FE". Lines connect the central box to both the left and right boxes.
+
+Figure 7-10: Service orchestration FE functional view diagram
+
+**Figure 7-10 – Service orchestration FE functional view**
+
+The service composition generates an orchestrated service logic that combines existing service resources to define high level functionalities. The orchestrated service logic describes interactions between multiple services (resources) by exchanging messages, branching logics, and invocation sequences. These orchestrated services (resources) are created using by related orchestrate capabilities and languages such as BPEL and POJO. The service composition provides the ability to expose an orchestrated service (resources) using a specific protocol or interface (REST, SOAP, etc.).
+
+The composite service execution is conducted by parsing and running the service logic. During the composite service execution, sequential request of resources are forwarded to service dispatcher FE.
+
+Composite resource descriptions are stored as service logic. The application development support FE use composite resources in the developing time.
+
+### 7.2.7 Resource routing FE
+
+For the purpose of interaction with other NGN-SIDEs, the resource routing FE manages and provides resource routing information to locate the resources in other NGN-SIDEs.
+
+Figure 7-11 shows the functional view of the resource routing FE.
+
+
+
+```
+graph LR; RRF[Resource registry FE] --- RFE[Resource routing FE]; RFE --- SDFE[Service dispatcher FE]; subgraph RFE [Resource routing FE]; RIS[Routing information synchronization]; RIA[Routing information access]; RIR([Routing information repository]); end
+```
+
+The diagram illustrates the functional view of the Resource routing FE. It is a central green box labeled "Resource routing FE" containing three components: "Routing information synchronization", "Routing information access", and "Routing information repository" (represented as an oval). To the left of this box is a green box labeled "Resource registry FE", and to the right is a green box labeled "Service dispatcher FE". Lines connect the central box to both the left and right boxes.
+
+Figure 7-11: Resource routing FE functional view diagram
+
+Y.2025(12)\_F7-11
+
+**Figure 7-11 – Resource routing FE functional view**
+
+The resource routing FE includes the following sub-functions:
+
+- Routing information synchronization
+- Routing information access
+- Routing information repository.
+
+The routing information repository function stores the resource routing information of the resources which are registered in other NGN-SIDEs.
+
+When a resource is registered to one of the NGN-SIDE, the routing information synchronization function synchronizes the resource routing related information to the resource routing FE in other NGN-SIDEs. For details, refer to Annex A.
+
+The routing information access function interacts with the service dispatcher FE to accomplish the resource request routing function between NGN-SIDEs.
+
+## **7.3 NGN-SIDE service delivery management functional group related functional entities**
+
+### **7.3.1 Content management FE**
+
+The content management FE manages the content, including content storage, content update and content deletion functions.
+
+Figure 7-12 shows a functional view of the content management FE.
+
+
+
+```
+graph TD; CMFE[Content management FE] --- ADSFE[Application development support FE]; CMFE --- CD[Content deployment]; CMFE --- CC[Content classification]; CMFE --- CDEL[Content delivery];
+```
+
+The diagram illustrates the functional view of the Content management FE. It consists of a large light green rectangle labeled 'Content management FE' at the top. Inside this rectangle, there are three smaller rounded rectangles: 'Content deployment' at the top, 'Content classification' at the bottom left, and 'Content delivery' at the bottom right. Below the 'Content management FE' rectangle, there is a separate rectangle labeled 'Application development support FE'. A vertical line connects the bottom center of the 'Content management FE' rectangle to the top center of the 'Application development support FE' rectangle.
+
+Functional view of the Content management FE
+
+**Figure 7-12 – Content management FE functional view**
+
+The content classification function extracts the information of the content resource and classifies content resources into different groups. Content resource information includes the content size, type, publisher, location, etc.
+
+The content delivery function performs content delivery to different NGN-SIDE users' environments, such as content for specific applications, content for specific end user equipment, content for specific end user locations, etc.
+
+The content deployment function dispatches content to content storage resources in order to expose content to applications.
+
+### **7.3.2 Policy management FE**
+
+Figure 7-13 shows a functional view of the policy management FE.
+
+
+
+```
+
+graph LR
+ PDE[Policy decision FE] --- PMFE[Policy management FE]
+ subgraph PMFE [Policy management FE]
+ MMS[Management and synchronization]
+ PS([Policy storage])
+ end
+
+```
+
+Figure 7-13 – Policy management FE functional view. The diagram shows a 'Policy decision FE' box connected to a larger 'Policy management FE' box. Inside the 'Policy management FE' box, there is a rounded rectangle labeled 'Management and synchronization' and an oval labeled 'Policy storage'.
+
+**Figure 7-13 – Policy management FE functional view**
+
+The policy management FE provides management of policies used for access, provisioning, logging and management of resources.
+
+The policy management FE is responsible for providing a central place for the network provider to manage the rules and policies associated with APIs and services that are exposing through NGN-SIDE. This component will govern and control the lifecycle of the rules/policies. The administrator and provider portal will interface with this FE to provide the following functionalities.
+
+- Create/modify/delete/query rules/policies
+- Activate and deactivate rules/policies
+- View the status of the rules/policies, which includes:
+ - a) Current deployed version
+ - b) APIs or services being used
+ - c) Display metrics about the API/service performance
+- Provision the rules/policies in conjunction with partners and their application as well as APIs, which includes:
+ - a) Define what rules are to be applied for a given API.
+ - b) Define a default context that is to be associated with a rule/policy for an given API.
+ - c) Define a partner's application policy/rule context for a given rule which is to be used when the application invokes that API.
+ - d) Define how a rule/policy action is to behave for a given API.
+- The policy storage in this FE stores these resource related policies, which include SLAs between NGN-SIDE users and NGN-SIDE resources and end user preferences. These policies could be used by policy decision FE to select an appropriate resource for the resource request from applications.
+
+### 7.3.3 Charging FE
+
+The charging FE provides charging information collection and synchronization function as well as local storage of the call detail records (CDRs).
+
+Figure 7-14 shows a functional view of the charging FE.
+
+
+
+```
+
+graph TD
+ subgraph Charging_FE [Charging FE]
+ CS[Collection and synchronization]
+ SA[Statistical Analysis]
+ CS_CDR((CDR storage))
+ end
+ AC[Access control FE] --- Charging_FE
+ RB[Resource brokering FE] --- Charging_FE
+ RMF[Resource manager FE] --- Charging_FE
+ SOF[Service orchestration FE] --- Charging_FE
+
+```
+
+Figure 7-14 – Charging FE functional view. The diagram shows a central 'Charging FE' block containing 'Collection and synchronization', 'Statistical Analysis', and 'CDR storage'. It is connected to 'Access control FE', 'Resource brokering FE', 'Resource manager FE', and 'Service orchestration FE'.
+
+**Figure 7-14 – Charging FE functional view**
+
+The collection and synchronization function receives the charging information from other FEs in NGN-SIDE, such as the access control FE, service orchestration FE and the resource brokering FE.
+
+When it is required to generate CDRs, charging FE generates CDRs according to the received charging information and stores the CDRs in the CDR storage which are synchronized with the billing domain and backend systems.
+
+The statistical analysis function analyses the resource usage according to the CDRs. Statistical analysis supports multiple dimensions (e.g., resource type, application, developer, time dimension). The charging FE supports event-based online/offline charging mechanisms as specified in [ITU-T Y.2233] and it could be mapped to charging collection function, online charging function and charging gateway function in the functional architecture of charging and accounting in NGN. The charging FE enables SP to implement differentiated charging according to the quality of service (QoS) of the resources as defined in SLA.
+
+When it is required to charge NGN-SIDE users (i.e., application provider), the access control FE triggers a charging event to send charging-related information to the charging FE.
+
+When it is required to support charging for NGN-SIDE resource providers (i.e., short message service (SMS) provider), the resource brokering FE triggers a charging event to send charging-related information (e.g., resource usage information) to the charging FE.
+
+When composite resource whose service logic is stored in service orchestration FE is executed, the service orchestration FE triggers a charging-event to transfer charging related information to the charging FE.
+
+In case of charging for composite resources, the charging FE generates a transaction identifier against this composite resource. Service orchestration FE includes this transaction identifier in the charging information. The service orchestration FE notifies the end of a service transaction to the charging FE.
+
+When it is required to charge for the consumption of resources including computing, connectivity and storage, the resource manager FE sends charging information related to the resource consumption.
+
+### 7.3.4 Management of role related information FE
+
+Figure 7-15 shows a functional view of the management of role-related information FE.
+
+
+
+```
+
+graph LR
+ A[Access control FE] --- B[Management of role related information FE]
+ subgraph B [Management of role related information FE]
+ C[Information management]
+ D[Information Access]
+ E([Information storage])
+ end
+
+```
+
+Figure 7-15: Management of role related information FE functional view. The diagram shows an 'Access control FE' box connected to a larger 'Management of role related information FE' box. Inside the larger box are 'Information management', 'Information Access', and 'Information storage' components.
+
+**Figure 7-15 – Management of role related information FE functional view**
+
+The management of the role-related information FE provides management, storage and access control for all role related information in the NGN-SIDE ecosystems.
+
+The role-related information includes basic information for all roles (e.g., NGN-SIDE user-resource provider relationship), role-specific information (e.g., preference profiles) and subscription-related information (e.g., end user-application provider subscription relationship information for in-house applications). The information storage is provided in the management of role-related information FE to store all this information.
+
+The management operations for the NGN-SIDE provider includes add, modify and delete operations of this role-related information, which are implemented by the information management function. When an end user subscribes a new application, the subscription relationship will be added by the information management function into the information storage, and the end user's related preference profiles are stored in the information storage.
+
+The information access function provides role-related information and subscription to the access control FE for authentication and authorization purposes.
+
+The information management function manages the subscription and preferences of different end users with a particular application. The access control FE checks the subscription of an end user with a specific application by interacting with the information access function.
+
+### 7.3.5 Application provisioning FE
+
+The application provisioning FE provides mechanisms to deploy applications.
+
+Figure 7-16 shows a functional view of the application provisioning FE.
+
+
+
+```
+
+graph LR
+ A[Resource Manager FE] --- B[Application provisioning FE]
+ subgraph B [Application provisioning FE]
+ C[General Management]
+ D[Lifecycle Management]
+ E[Process Control]
+ F[Resource Control]
+ G[Tools]
+ end
+
+```
+
+Figure 7-16: Application provisioning FE functional view. The diagram shows a 'Resource Manager FE' box connected to a larger 'Application provisioning FE' box. Inside the larger box are 'General Management', 'Lifecycle Management', 'Process Control', 'Resource Control', and 'Tools' components.
+
+**Figure 7-16 – Application provisioning FE functional view**
+
+Application provisioning includes the following functions:
+
+- the general management function: provides the general management function of application deployment, such as data management, statistical analysis and so on;
+- the lifecycle management function: manages the status of applications in the application deployment process, delivering the start and stop instructions of application deployment and collecting the results;
+- the process control function: controls the application deployment process, such as requests number, delay time and so on;
+- the resource control function: controls and records dispatch of the resources;
+- tools function: includes format conversion tool, which converts the deployment instruction into a suitable format, so as to fit for different running environment; application deployment templates, which could fulfil the automatic deployment and application uninstalling tool. During application uninstall process, uninstalling tool queries the database and other information, then packages operational data of the application into readable structured data.
+
+### 7.3.6 Context management FE
+
+Figure 7-17 shows a functional view of the context management FE.
+
+
+
+```
+graph TD
+ subgraph CMFE [Context management FE]
+ CD[Collection and delivery]
+ CIS([Context information storage])
+ end
+ SDFE[Service dispatcher FE] --- CMFE
+ SOFE[Service orchestration FE] --- CMFE
+ CMFE --- ADSFE[Application development support FE]
+ CMFE --- RREFE[Resource registry FE]
+ CMFE --- RBEFE[Resource brokering FE]
+```
+
+Figure 7-17: Context management FE functional view. The diagram shows a central 'Context management FE' block. Inside this block are two sub-components: 'Collection and delivery' and 'Context information storage'. The 'Context management FE' block is connected to five external functional elements: 'Service dispatcher FE' and 'Service orchestration FE' on the left; 'Application development support FE' and 'Resource registry FE' on the right; and 'Resource brokering FE' at the bottom.
+
+**Figure 7-17 – Context management FE functional view**
+
+The context management FE collects and aggregates context information related to different context sources, and exposes the context information to other NGN-SIDE FEs according to the policies.
+
+These context information includes the service context, such as service availability, service QoS, service performance; the end user context, such as the end user's identity, end user's presence, end user's location, end user's preferences and end user's social status; the device context, such as device status (device's presence, device's capabilities), device's runtime parameters (CPU, memory, load, performance, etc.); the network context, such as network conditions (e.g., bandwidth, traffic, topology, etc.) and network performance.
+
+This FE provides a collection and delivery function for collecting and managing the different kinds of context information, also the function for exposing that information to other FEs on the NGN-SIDE; and provides a storage function for storing that information.
+
+The resource registry FE synchronizes resource information with the context management FE. When the resource is registered, the context management FE starts to collect the resource context information.
+
+The service dispatcher FE and the service orchestration FE interact with the context management FE to achieve the context information, such as the end user context, the device context, the service context, etc. The context management FE returns the context information of services to the service parsing and processing function of service dispatcher FE according to the received the request.
+
+The resource brokering FE interacts with the context management FE to achieve the context information, such as the resource related context, the network context, etc., to select an appropriate resource for the application.
+
+The application development support FE could use the context information in the context management FE to develop context-based applications.
+
+Both at the beginning and in the middle of an application execution, the context information could be achieved from this FE to customize, personalize, and adapt the application execution according to the actual situation.
+
+## 7.4 NGN-SIDE adaptation functional group related functional entities
+
+### 7.4.1 Resource brokering FE
+
+The resource brokering FE provides the interaction between applications and resources for the downward invocation of resources and the upward triggering of applications. It also interacts with the NGN-SIDE integration layer FEs (e.g., policy decision FE) to enforce the resource-related policies such as scheduling of resources [ITU-T Y.2240].
+
+Figure 7-18 shows the functional view of the resource brokering FE.
+
+Resource brokering FE includes the following sub-functions:
+
+- Resource invocation
+- Application invocation
+- Resource scheduler
+- Application scheduler.
+
+
+
+```
+graph TD; SD[Service dispatcher FE] --- RB[Resource brokering FE]; CM[Context management FE] --- RB; PD[Policy decision FE] --- RB; AP[Application provisioning FE] --- RB; RR[Resource registry FE] --- RB; RA[Resource adaptor FE] --- RB; subgraph RB [Resource brokering FE]; RI[Resource invocatin]; AI[Application invocatin]; RS[Resource scheduler]; AS[Application scheduler]; end
+```
+
+The diagram illustrates the functional view of the Resource brokering FE. It is a central green box containing four sub-functions: Resource invocatin, Application invocatin, Resource scheduler, and Application scheduler. This central box is connected to six external green boxes: Service dispatcher FE (top), Context management FE (left), Policy decision FE (left), Application provisioning FE (right), Resource registry FE (right), and Resource adaptor FE (bottom). The connections are as follows: Service dispatcher FE connects to the top of the central box. Context management FE connects to the left side of the central box. Policy decision FE connects to the left side of the central box. Application provisioning FE connects to the right side of the central box. Resource registry FE connects to the right side of the central box. Resource adaptor FE connects to the bottom of the central box.
+
+Functional view of the Resource brokering FE
+
+**Figure 7-18 – Resource brokering FE functional view**
+
+When the resource brokering FE receives a request with a designated resource address (or resource identifier), resource invocation handler parses the request to identify the target resource. The resource invocation handler interacts with the policy decision FE to analyse the related service level agreements (SLAs) and other related policies between NGN-SIDE provider and resource provider. Finally, a request is sent to the corresponding resource adaptor as scheduled by the resource scheduler.
+
+When the resource brokering FE receives a request with a designated application address (or application identifier), the application invocation handler parses and authorizes the service request to identify the target application. The application invocation handler interacts with the policy decision FE to analyse the related service level agreements (SLAs) and other related policies between NGN-SIDE provider and application provider. Finally, a request is sent to the corresponding application as scheduled by the application scheduler.
+
+During runtime, if resource information changes, the resource registry FE notifies the resource brokering FE. The resource brokering FE reflects the corresponding changes in resource invocation and resource scheduler functions.
+
+The resource scheduler is provisioned resource information during resource registration and maintains a list of registered resources with the resource metrics and make available the list of resources based on certain criteria for a particular service. The resource scheduler periodically checks the connectivity and QoS of resource.
+
+The application scheduler is provisioned with application information during application provisioning and maintains application information so that resource requests can be sent to the application when a request is originated from a resource.
+
+### **7.4.2 Resource adaptor FE**
+
+The resource adaptor FE provides mechanisms that allow applications to uniformly access resources by hiding the details of the resources. The resources offered by NGN/non-NGN may vary according to the underlying resource technologies. This makes it difficult for application developers to develop new applications based on direct usage of such diverse and complex underlying resources [ITU-T Y.2240]. To address this, the resource adaptor FE prepares an abstract interface for various resources offered by NGN/non-NGN (e.g., USN, telecom network, broadcasting network, and contents network). The resource adaptor FE performs two types of adaptation: control plan level and data plan level.
+
+The resource adaptor FE receives requests towards resources, and then translates the request message into protocols/APIs according to the target resource protocol/API.
+
+The resource adaptor FE receives requests towards applications, translates the request message into NGN-SIDE internal common messaging format.
+
+When the resource adaptor FE receives a request from the resource registry FE, the resource adaptor FE sets up a corresponding data/control adaptation function for the resource being registered according to the request.
+
+Figure 7-19 shows the functional view of the resource adaptor FE, which includes:
+
+- Control adaptation function
+- Data adaptation function
+- Resource access function
+- Instance management function
+- Resource description repository.
+
+
+
+```
+
+graph TD
+ RB[Resource Brokering FE] --- RA[Resource adaptor FE]
+ RR[Resource registry FE] --- RA
+ subgraph RA [Resource adaptor FE]
+ DA[Data adaptation]
+ IM[Instance management]
+ CA[Control adaptation]
+ RD([Resource description])
+ RA_A[Resource access]
+ end
+ RA --- NGN[NGN Resources]
+ RA --- NonNGN[Non-NGN Resources]
+
+```
+
+Figure 7-19 – resource adaptor FE functional view. The diagram shows a central 'Resource adaptor FE' block containing 'Data adaptation', 'Instance management', 'Control adaptation', 'Resource description', and 'Resource access'. It is connected to 'Resource Brokering FE' and 'Resource registry FE' at the top, and 'NGN Resources' and 'Non-NGN Resources' at the bottom.
+
+**Figure 7-19 – resource adaptor FE functional view**
+
+The control adaptation function performs control protocol/API conversions and matches protocol/API request messages between applications and resources.
+
+The data adaptation function performs data adaptation functions to enable applications and resources to deliver data in a heterogeneous environment (e.g., USN data format, and Internet data format).
+
+The resource access function provides an abstract interface to resources in NGN/non-NGN with data adaptation and control adaptation. When a resource is requested through the abstract interface, the resource adaptor FE identifies data type and protocols of the target resource and performs appropriate adaptations for uniform access to various resources.
+
+The instance management function manages all instances of the resource adaptor for a particular resource. It can initiate and remove instances of the resource adaptor.
+
+The resource description repository stores resource description of each resource being adapted. The resource description information includes resource identifier, resource adaptor instance and resource access methods.
+
+# 8 NGN-SIDE reference points
+
+NGN-SIDE reference points, shown in Figure 7-1 are distinguished into:
+
+- NGN-SIDE internal reference points, related to interactions between NGN-SIDE FEs;
+- NGN-SIDE external reference points, related to interactions between NGN-SIDE FEs and functions external to NGN-SIDE.
+
+## 8.1 NGN-SIDE internal reference points
+
+The following provides the description of the NGN-SIDE internal reference points:
+
+**ITE-ADS** Reference point between the testing environment FE and the application development support FE.
+
+The application development support FE can achieve online/offline test tool, test environment and test result through this reference point and make them available to the application developers.
+
+| | |
+|----------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| I SO-ADS | Reference point between the service orchestration FE and the application development support FE.
The application developer can store their application as resource in service orchestration FE through this reference point, also can achieve the resource kept in service orchestration FE for their own use.
|
+| I ADS-CXM | Reference point between the application development support FE and the context management FE.
The application development support FE can achieve context information through this reference point.
|
+| I ADS-CNM | Reference point between the application development support FE and the content management FE.
The application development support FE can achieve content information through this reference point.
|
+| I ADS-RR | Reference point between the resource repository FE and the application development support FE.
The application development support FE can achieve development interface information of the resources through this reference point.
|
+| I RR-RE | Reference point between the resource repository FE and the resource registry FE.
The resource repository FE can achieve resource description information from the resource registry FE through this reference point.
|
+| I AC-SD | Reference point between the access control FE and the service dispatcher FE.
With this reference point, access control FE sends request to service dispatcher FE for further processing. Additionally, service dispatcher FE uses this reference point to transfer request originated from underlying resource (e.g., SMS) towards application.
|
+| I SD-SO | Reference point between the service orchestration FE and the service dispatcher FE.
With this reference point, service dispatcher FE invokes composite resource in service orchestration FE.
|
+| I SD-RR | Reference point between the resource registry FE and the service dispatcher FE.
With this reference point, service dispatcher FE interrogates the availability of the requested resource in resource registry FE.
|
+| I SD-PD | Reference point between the policy decision FE and the service dispatcher FE.
With this reference point, service dispatcher FE interacts with policy decision FE which determines the policies and sends the outcome to the service dispatcher FE.
|
+| I PD-RM | Reference point between the resource manager FE and the policy decision FE.
With this reference point, resource manager FE consults policy decision FE to allocate resources required for in-house application deployment.
|
+| I AC-CH | Reference point between the access control FE and the charging FE.
The access control FE can provide charging information through this reference point.
|
+| I AC-MOR | Reference point between the access control FE and the management of role related information FE.
The access control FE can achieve role related information through this reference point.
|
+| I SO-CH | Reference point between the service orchestration FE and the charging FE.
The service orchestration FE can provide charging information through this reference point.
|
+
+| | |
+|---------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| I PD-PM | Reference point between the policy decision FE and the policy management FE.
The policy decision FE can achieve the policy configured through this reference point. |
+| I RM-AP | Reference point between the resource manager FE and the application provisioning FE.
The resource manager FE can achieve the application information configured through this reference point. |
+| I RB-CH | Reference point between the resource brokering FE and the charging FE.
The resource brokering FE can provide charging information through this reference point. |
+| I RB-CXM | Reference point between the resource brokering FE and the content management FE.
The resource brokering FE can provide context information through this reference point. |
+| I RB-AP | Reference point between the resource brokering FE and the application provisioning FE.
The resource brokering FE can achieve application information configured through this reference point. |
+| I SO-CXM | Reference point between the service orchestration FE and the context management FE.
The service orchestration FE can achieve context information through this reference point. |
+| I SD-CXM | Reference point between the service dispatcher FE and the context management FE.
The service dispatcher FE can achieve context information through this reference point. |
+| I RB-PD | Reference point between the resource brokering FE and the policy decision FE.
The policy decision FE can provide related policy configured through this reference point. |
+| I RB-RR | Reference point between the resource brokering FE and the resource registry FE.
The resource brokering FE can provide registration information through this reference point. |
+| I RB-SD | Reference point between the resource brokering FE and the service dispatch FE.
The service dispatch FE makes use of this reference point to send resource request to resource brokering for the proper selection of the resource. |
+| I RB-RA | Reference point between the resource brokering FE and the resource adaptor FE.
The resource adaptor FE can provide adapted resource through this reference point. |
+| I RM-CH | Reference point between the resource manager FE and the charging FE.
With this reference point, the resource manager FE provides charging information related to consumption of resources (including computing, connectivity, and storage). |
+| I RR-ROU | Reference point between the resource registry FE and the resource routing FE.
With this reference point, the resource registry FE provides resource routing related information to the resource routing FE to synchronize the resource routing information to other NGN-SIDES. |
+| I SD-ROU | Reference point between the service dispatcher FE and the resource routing FE.
The service dispatcher FE achieves resource routing information through this reference point. |
+
+## 8.2 NGN-SIDE external reference points
+
+### 8.2.1 Reference points related to NGN-SIDE service interfaces
+
+This clause provides the reference points which can be mapped to NGN-SIDE service interfaces identified in [ITU-T Y.2240].
+
+Appendix I provides information about APIs relevant to the NGN-SIDE service interfaces.
+
+- | | |
+|---------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| $I_{ADF-ADS}$ | Reference point between the application development functions and the application development support FE.
With this reference point, developers can access the development environment provided by NGN-SIDE. This reference point can be mapped to the NGN-SIDE ANI or UNI service interfaces. |
+| $I_{ADF-TE}$ | Reference point between the application development functions and the testing environment FE.
With this reference point, the developers can access the testing environment provided by NGN-SIDE. This reference point can be mapped to the NGN-SIDE ANI or UNI service interfaces. |
+| $I_{APP-AC}$ | Reference point between the applications and the access control FE.
With this reference point, the applications can send resource request with authentication and authorization information to NGN-SIDE. This reference point can be mapped to the NGN-SIDE ANI or UNI service interfaces. |
+| $I_{CPF-CNM}$ | Reference point between the content provider functions and the content management FE.
With this reference point, the content provider can make available different types of content as a resource to NGN-SIDE. This reference point can be mapped to the NGN-SIDE SNI service interface identified in [ITU-T Y.2240]. |
+
+NOTE – Annex A describes interactions between different NGN-SIDEs which can be achieved through the NGN-SIDE NNI service interface identified in [ITU-T Y.2240].
+
+### 8.2.2 Reference points related to NGN-SIDE resource interfaces
+
+This clause provides the reference points related to NGN-SIDE resource interfaces identified in [ITU-T Y.2240].
+
+- | | |
+|---------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| $I_{RA-NGN}$ | Reference point between the resource adaptor FE and the resources in NGN (see also the relevant information in clauses 9 and 10 of [ITU-T Y.2240]). The resources are provided according to the corresponding request through this reference point. |
+| $I_{RA-NNGN}$ | Reference point between the resource adaptor FE and the resources in non-NGN (see also the relevant information in clauses 9 and 10 of [ITU-T Y.2240]). |
+
+### 8.2.3 Reference points to other functions
+
+- | | |
+|---------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| $I_{BD-CH}$ | Reference point between the billing domain and the charging FE.
With this reference point, the billing domain can achieve charging information such as CDR from NGN-SIDE. |
+| $I_{ADM-CNM}$ | Reference point between the administrator functions and the content management FE.
With this reference point, the administrator can manage the content. |
+| $I_{ADM-AP}$ | Reference point between the administration function and the application provisioning FE.
With this reference point, the administrator can manage the application's lifecycle, deployment status, etc. |
+
+# 9 NGN-SIDE service procedures
+
+## 9.1 Resource registration procedure
+
+Resources are located and accessed by the application as well as used by the application developer after resources have been registered successfully at the resource registry FE.
+
+Figure 9-1 describes how a resource is registered to NGN-SIDE.
+
+
+
+```
+sequenceDiagram
+ participant RPF as Resource provider FE
+ participant RRFE as Resource registry FE
+ participant RAFE as Resource adaptor FE
+ participant RREFE as Resource repository FE
+
+ RPF->>RRFE: 1. Registration request
+ RRFE->>RAFE: 2. Adaptation set-up request
+ RAFE->>RAFE: 3. Set up the adaptation function for the resource
+ RAFE-->>RRFE: 4. Response
+ RRFE->>RREFE: 5. Resource interface description information request
+ RREFE->>RREFE: 6. Store resource interface description information
+ RREFE-->>RRFE: 7. Response
+ RRFE-->>RPF: 8. Response
+```
+
+The diagram shows the following steps: 1. Registration request from Resource provider FE to Resource registry FE. 2. Adaptation set-up request from Resource registry FE to Resource adaptor FE. 3. Set up the adaptation function for the resource (self-call on Resource adaptor FE). 4. Response from Resource adaptor FE to Resource registry FE. 5. Resource interface description information request from Resource registry FE to Resource repository FE. 6. Store resource interface description information (self-call on Resource repository FE). 7. Response from Resource repository FE to Resource registry FE. 8. Response from Resource registry FE to Resource provider FE.
+
+Sequence diagram illustrating the Resource registration procedure involving four entities: Resource provider FE, Resource registry FE, Resource adaptor FE, and Resource repository FE.
+
+**Figure 9-1 – Resource registration procedure**
+
+Procedure description:
+
+- Resource provider sends resource registration request to resource registry FE.
+- After receiving the request, resource registry FE sends resource adaptation set-up request to adaptor.
+- Adaptor sets up the adaptation function corresponding to the resource information.
+- Adaptor sends back the response to resource registry FE.
+- Resource registry FE sends request which includes resource interface description information to resource repository FE.
+- Resource repository FE stores the resource interface description information locally.
+- Resource repository FE sends back the response to resource registry FE.
+
+NOTE – Order of step 2 and 5 is implementation dependent and can be executed in any order.
+
+Resource registry FE notifies resource provider the resource registration result.
+
+## 9.2 Application development procedure
+
+This procedure describes how developers access the application development related functions provided by NGN-SIDE to develop and test applications which using the resources exposed in NGN-SIDE.
+
+
+
+```
+sequenceDiagram
+ participant AD as Application developer
+ participant ADSFE as Application development support FE
+ participant RRF as Resource repository FE
+ participant TEFE as Testing environment FE
+
+ AD->>ADSFE: 1. Access
+ ADSFE->>RRF: 2. Resource development information request
+ RRF-->>ADSFE: 3. Resource development information response
+ ADSFE->>ADSFE: 4. Develop application
+ ADSFE->>TEFE: 5. Application testing request and developed application delivery
+ TEFE->>TEFE: 6. Test application
+ TEFE-->>ADSFE: 7. Application testing result
+```
+
+The diagram is a sequence diagram showing the interaction between four entities: Application developer (dashed box), Application development support FE, Resource repository FE, and Testing environment FE. The process follows these steps: 1. The Application developer sends an 'Access' message to the Application development support FE. 2. The Application development support FE sends a 'Resource development information request' to the Resource repository FE. 3. The Resource repository FE returns a 'Resource development information response' to the Application development support FE. 4. The Application development support FE performs a self-action labeled 'Develop application'. 5. The Application development support FE sends an 'Application testing request and developed application delivery' message to the Testing environment FE. 6. The Testing environment FE performs a self-action labeled 'Test application'. 7. The Testing environment FE returns an 'Application testing result' message to the Application development support FE.
+
+Sequence diagram illustrating the Application development procedure involving four participants: Application developer, Application development support FE, Resource repository FE, and Testing environment FE.
+
+**Figure 9-2 – Application development procedure**
+
+Application developer accesses the application development support FE to create application.
+
+- The application development support FE supports interaction with the resource repository FE to obtain the development interface information of the resources required in the application development.
+- The resource repository FE returns the development interface information of the resources.
+- Application developer creates applications using online and/or offline design tools according to the resource development interface information.
+- When application is created, application developer requests testing of application and deliver the developed application to the testing environment.
+- The testing environment FE performs the testing procedures for the application.
+- The testing environment FE returns the application testing result.
+
+## 9.3 Application provisioning procedure
+
+The application provisioning FE provides lifecycle management for applications in NGN-SIDE such as deployment, activation, deactivation and withdrawal. In those procedures, the application provisioning FE interacts with the administrator and provider portal (i.e., user interface), resource manager FE and resource brokering FE.
+
+### 9.3.1 Application deployment
+
+The application deployment procedure stores provisioning information of the target application such as a name addresses and requirements in NGN-SIDE. Figure 9-3 depicts how an application is deployed into NGN-SIDE.
+
+
+
+```
+sequenceDiagram
+ participant Admin as Administrator & Provider Portal
+ participant AppFE as Application provisioning FE
+ participant ResMgrFE as Resource manager FE
+ participant ResBrokFE as Resource brokering FE
+
+ Admin->>AppFE: 1. Application deployment request
+ AppFE->>ResMgrFE: 2. Resource allocating request
+ ResMgrFE->>ResMgrFE: 3. Resource allocation
+ ResMgrFE-->>AppFE: 4. Response
+ AppFE->>ResBrokFE: 5. Notifying information of the application
+ ResBrokFE-->>AppFE: 6. Response
+ AppFE-->>Admin: 7. Response
+```
+
+The diagram is a sequence diagram showing the interaction between four components: Administrator & Provider Portal, Application provisioning FE, Resource manager FE, and Resource brokering FE. The process begins with the Administrator & Provider Portal sending a '1. Application deployment request' to the Application provisioning FE. The Application provisioning FE then sends a '2. Resource allocating request' to the Resource manager FE. The Resource manager FE performs a self-action labeled '3. Resource allocation'. Following this, the Resource manager FE sends a '4. Response' back to the Application provisioning FE. The Application provisioning FE then sends '5. Notifying information of the application' to the Resource brokering FE. The Resource brokering FE responds with a '6. Response' to the Application provisioning FE. Finally, the Application provisioning FE sends a '7. Response' back to the Administrator & Provider Portal.
+
+Sequence diagram illustrating the application deployment processes between four entities: Administrator & Provider Portal, Application provisioning FE, Resource manager FE, and Resource brokering FE.
+
+**Figure 9-3 – Application deployment processes**
+
+- An administrator requests deployment of an application through the provider portal interface. The application related information is inserted into application provisioning FE.
+- Application provisioning FE interprets the application related information that contains an application name, an application accessible address, and resource requirements and so on.
+- Application provisioning FE sends resource requirements to resource manager FE.
+- Resource manager FE allocates resources for the deploying application.
+- Resource manager FE sends back the result to application provisioning FE.
+- After required resources are allocated for the application, application provisioning FE notifies the information of the application deployment to resource brokering FE.
+
+- Resource brokering FE maintains state of the application (i.e., deployed) and sends back the response to application provisioning FE.
+- Application provisioning FE sends back the result of the application deployment to the provider portal.
+
+### 9.3.2 Application activation/deactivation
+
+The application activation/deactivation procedure switches state information of an application whether it is available or not. Figure 9-4 depicts how an application is activated or deactivated.
+
+
+
+```
+
+sequenceDiagram
+ participant Admin as Administrator & Provider Portal
+ participant AppProv as Application provisioning FE
+ participant ResMgr as Resource manager FE
+ participant ResBrok as Resource brokering FE
+
+ Admin->>AppProv: 1. Application activation/deactivation request
+ AppProv->>ResBrok: 2. Notifying state of the application
+ ResBrok-->>AppProv: 3. Response
+ AppProv-->>Admin: 4. Response
+
+```
+
+The diagram shows four vertical lifelines representing: Administrator & Provider Portal, Application provisioning FE, Resource manager FE, and Resource brokering FE. The process consists of four steps: 1. A request from the Administrator & Provider Portal to the Application provisioning FE. 2. A notification from the Application provisioning FE to the Resource brokering FE. 3. A response back from the Resource brokering FE to the Application provisioning FE. 4. A final response from the Application provisioning FE back to the Administrator & Provider Portal. The Resource manager FE is shown as a component but does not participate in these specific message exchanges.
+
+Sequence diagram of Application activation/deactivation processes showing interactions between Administrator & Provider Portal, Application provisioning FE, Resource manager FE, and Resource brokering FE.
+
+**Figure 9-4 – Application activation/deactivation processes**
+
+An administrator requests activation or deactivation of an application through the provider portal interface. The target application identifier is inserted into application provisioning FE.
+
+- Application provisioning FE notifies the state of them to resource brokering FE.
+- Resource brokering FE updates state of the application (i.e., activated or deactivated) and sends back the response to application provisioning FE.
+- Application provisioning FE sends back the result of the application activation or deactivation to provider portal.
+
+### 9.3.3 Application withdrawal
+
+The application withdrawal procedure eliminates the application provisioning information and related resources from NGN-SIDE. Figure 9-5 depicts how an application is removed.
+
+
+
+```
+
+sequenceDiagram
+ participant A as Administrator & Provider Portal
+ participant B as Application provisioning FE
+ participant C as Resource manager FE
+ participant D as Resource brokering FE
+
+ A->>B: 1. Application withdrawal request
+ B->>C: 2. Resource release request
+ C->>C: 3. Resource release
+ C->>B: 4. Response
+ B->>D: 5. Notifying elimination of the application
+ D->>C: 6. Response
+ C->>B: 6. Response
+ B->>A: 7. Response
+
+```
+
+Sequence diagram showing the application withdrawal process between four components: Administrator & Provider Portal, Application provisioning FE, Resource manager FE, and Resource brokering FE. The process consists of seven steps: 1. Application withdrawal request, 2. Resource release request, 3. Resource release (self-call), 4. Response, 5. Notifying elimination of the application, 6. Response, and 7. Response.
+
+**Figure 9-5 – Application withdrawal processes**
+
+An administrator requests withdrawal of an application through the provider portal interface. The target application identifier is sent to the application provisioning FE.
+
+- The application provisioning FE sends a withdrawal command with the target application identifier to resource manager FE.
+- Resource manager FE removes the all resources allocated to the application.
+- Resource manager FE sends back the result to application provisioning FE.
+- Application provisioning FE notifies the withdrawal of the application to resource brokering FE.
+- Resource brokering FE eliminates the application related information in it and sends back the response to application provisioning FE.
+- Application provisioning FE eliminates the application related information and sends back the result of application withdrawal to the provider portal.
+
+## 9.4 Resource triggering procedure
+
+This procedure describes the service flow to invoke a particular resource. This service flow includes interaction of access control FE, service dispatcher FE, resource registry FE, resource brokering FE and resource adaptor FE.
+
+In the following service flows, application has subscription to a location service enabler to find the user's location.
+
+
+
+```
+
+sequenceDiagram
+ participant Application
+ participant Access control FE
+ participant Service dispatcher FE
+ participant Resource registry FE
+ participant Resource brokering FE
+ participant Resource adaptor FE
+ participant Resource
+
+ Application->>Access control FE: 1. Resource request
+ Access control FE->>Service dispatcher FE: 2. Resource request
+ Service dispatcher FE->>Resource registry FE: 3. Query resource information
+ Resource registry FE-->>Service dispatcher FE: 4. Response
+ Service dispatcher FE->>Resource brokering FE: 5. Send resource request for brokering
+ Resource brokering FE->>Resource adaptor FE: 6. Resource adaptation
+ Resource adaptor FE->>Resource: 7. Invoke the requested resource
+ Resource->>Resource: 8. Request processing
+ Resource-->>Application: 9. Request response
+
+```
+
+Sequence diagram illustrating the Resource triggering procedure. The participants are Application, Access control FE, Service dispatcher FE, Resource registry FE, Resource brokering FE, Resource adaptor FE, and Resource. The steps are: 1. Resource request (Application to Access control FE), 2. Resource request (Access control FE to Service dispatcher FE), 3. Query resource information (Service dispatcher FE to Resource registry FE), 4. Response (Resource registry FE to Service dispatcher FE), 5. Send resource request for brokering (Service dispatcher FE to Resource brokering FE), 6. Resource adaptation (Resource brokering FE to Resource adaptor FE), 7. Invoke the requested resource (Resource adaptor FE to Resource), 8. Request processing (Resource self-loop), 9. Request response (Resource to Application).
+
+**Figure 9-6 – Resource triggering procedure**
+
+- Application sends a resource (location) request to get location information of a user.
+- Access control FE authenticates and authorizes requesting application.
+- Service dispatcher translates the API/protocol carrying the request into a common message structure and enquires the resource registry FE to get the resource information.
+- Resource registry returns the resource information to the service dispatcher FE.
+- Service dispatcher sends the resource request to resource brokering FE.
+- Resource brokering FE selects the resource among one or more candidate resource list and sends the resource request to the corresponding resource adaptor.
+- Resource adaptor generates a message according to the API/protocol native to the target resource and encloses content received in common message structure and invokes the target resource.
+- The target resource processes the request (get user location).
+- Target resource (location service enabler) sends response (carrying user location) towards application via different FEs.
+
+## 9.5 Context information-based service procedure
+
+In NGN-SIDE, the context information is utilized to select the most appropriate resources for the purpose of services or applications. The context management FE maintains in its own storage many types of context information such as the service context, the end user context, the device context and the network context.
+
+The main function of context information-based service procedure consists of delivery and collection of context information. First, delivery of context information is performed when the context management FE receives context requests from external entities that serve context information-based service. Second, context information is collected by context management FE continuously.
+
+Figure 9-7 depicts how context information-based services are conducted. Context using functional entities include the service dispatcher FE, service orchestration FE and application development support FE. Hereafter, those kinds of functional entities are indicated as context utilizing functional entities.
+
+
+
+```
+sequenceDiagram
+ participant CUF as Context Utilizing Functional Entities
+ participant CM as Context management FE
+ participant RB as Resource brokering FE
+
+ CUF->>CM: 1. Context request
+ CM->>CM: 2. Context inquiry
+ CM-->>CUF: 3. Context response
+ CUF->>RB: 4. Resource request based on contexts
+ RB-->>CM: 5. Resource response
+ RB->>CM: 6. Notify resource's context
+ CM->>CM: 7. Update context
+```
+
+The diagram is a sequence diagram showing the interaction between three main components: Context Utilizing Functional Entities (CUFE), Context management FE, and Resource brokering FE. The CUFE is represented by a box containing three sub-entities: Service dispatcher FE, Service orchestration FE, and Application development support FE. The process begins with the CUFE sending a '1. Context request' to the Context management FE. The Context management FE then performs a self-action '2. Context inquiry'. It then sends a '3. Context response' back to the CUFE. Next, the CUFE sends a '4. Resource request based on contexts' to the Resource brokering FE. The Resource brokering FE responds with a '5. Resource response' to the Context management FE. Finally, the Resource brokering FE sends a '6. Notify resource's context' to the Context management FE, which then performs a self-action '7. Update context'.
+
+Sequence diagram illustrating the context information-based service processes.
+
+**Figure 9-7 – Context information-based service processes**
+
+- Context utilizing functional entities request context information to context management FE.
+- Context management FE looks up requested context information at context management storage.
+
+- Context management sends back the context information to requested FE.
+- Context utilizing functional entities request resources based on context information.
+- Resource brokering FE returns resources to requested FE.
+- Resource brokering FE notifies context information to context managements FE if they have any change.
+- Context management FE updates context information.
+
+## 9.6 Charging procedure
+
+### 9.6.1 Charging procedures for NGN-SIDE user
+
+When the access control FE receives a request from an NGN-SIDE user (i.e., application), after authentication and authorization, the access control triggers charging event to send charging related information to the charging FE.
+
+The charging FE collects information on the service provider (SP) consumption of resources and generates call detail records (CDRs). The charging FE enables SP to implement differentiated charging according to the quality of service (QoS) of the resources as defined in SLA.
+
+
+
+```
+
+sequenceDiagram
+ participant Application
+ participant AccessControlFE as Access Control FE
+ participant ChargingFE as Charging FE
+ participant Billing
+
+ Application->>AccessControlFE: 1. request resource
+ AccessControlFE->>ChargingFE: 2. trigger charging event
+ ChargingFE->>ChargingFE: 3. generate CDR
+ ChargingFE->>Billing: 4. transfer CDRs
+
+```
+
+The diagram shows a sequence of four steps: 1. The Application sends a 'request resource' message to the Access Control FE. 2. The Access Control FE sends a 'trigger charging event' message to the Charging FE. 3. The Charging FE performs a self-action 'generate CDR' (represented by a circle with a downward arrow). 4. The Charging FE sends a 'transfer CDRs' message to the Billing system.
+
+Sequence diagram illustrating the charging procedure for NGN-SIDE user (application provider).
+
+**Figure 9-8 – Charging procedure for NGN-SIDE user (application provider)**
+
+- The application sends request to invoke resource.
+- The access control FE triggers charging event to send charging information related to the resource request.
+- The charging FE generates CDR according to received charging information.
+- The charging FE sends CDRs to the backend billing system.
+
+### 9.6.2 Charging procedures for composite resources
+
+When composite resource whose service logic is stored in service orchestration FE is executed, the service orchestration FE triggers a charging event to transfer charging-related information to the charging FE.
+
+The charging FE generates TransactionID against this composite resource. The service orchestration FE is required to always include this TransactionID in the charging information. The service orchestration FE notifies the end of a service transaction to the charging FE.
+
+
+
+```
+sequenceDiagram
+ participant ROFE as Resource orchestration FE
+ participant CFE as Charging FE
+ participant Billing
+
+ ROFE->>ROFE: 1. composite resource execution
+ ROFE->>CFE: 2. trigger charging event
+ activate CFE
+ CFE->>CFE: 3. generate Transaction ID
+ CFE->>ROFE: 4. send Transaction ID
+ deactivate CFE
+ ROFE->>ROFE: 5. generate CDR
+ ROFE->>Billing: 6. transfer CDRs
+```
+
+The diagram shows a sequence of operations between three entities: Resource orchestration FE, Charging FE, and Billing. 1. Resource orchestration FE performs a self-action '1. composite resource execution'. 2. Resource orchestration FE sends '2. trigger charging event' to Charging FE. 3. Charging FE performs a self-action '3. generate Transaction ID'. 4. Charging FE sends '4. send Transaction ID' back to Resource orchestration FE. 5. Resource orchestration FE performs a self-action '5. generate CDR'. 6. Resource orchestration FE sends '6. transfer CDRs' to Billing.
+
+Sequence diagram illustrating the charging procedure for composite resources involving Resource orchestration FE, Charging FE, and Billing.
+
+**Figure 9-9 – Charging procedure for composite resources**
+
+- The resource orchestration FE is executing the composite resource logic.
+- The service orchestration FE triggers charging event to send charging related information with the indication about composite resource.
+- The charging FE generates service TransactionID.
+- The charging FE sends TransactionID to service orchestration FE.
+- When composite resource transaction ends, service orchestration notifies the charging FE to close the charging transaction for the composite resource. As a result, the charging FE generates a CDR according to the charging information.
+- The charging FE sends CDRs to backend billing system.
+
+### 9.6.3 Charging procedures for NGN-SIDE resource provider
+
+In NGN-SIDE ecosystem, NGN-SIDE resource providers and NGN-SIDE resource users can have independent charging triggering mechanisms according to the deployment requirements.
+
+This scenario describes the charging procedures for the NGN-SIDE resource provider.
+
+
+
+```
+
+sequenceDiagram
+ participant Application
+ participant Resource brokering FE
+ participant Charging FE
+ participant Billing
+
+ Application->>Resource brokering FE: 1. Resource request
+ Resource brokering FE->>Charging FE: 2. trigger charging event
+ Charging FE->>Charging FE: 3. generate CDR
+ Charging FE->>Billing: 4. transfer CDRs
+
+```
+
+Sequence diagram showing the charging procedure for NGN-SIDE resource provider. The diagram involves four lifelines: Application, Resource brokering FE, Charging FE, and Billing. The process starts with a '1. Resource request' from Application to Resource brokering FE. Then, '2. trigger charging event' is sent from Resource brokering FE to Charging FE. On the Charging FE lifeline, a self-call '3. generate CDR' is shown. Finally, '4. transfer CDRs' is sent from Charging FE to Billing.
+
+**Figure 9-10 – Charging procedure for NGN-SIDE resource provider**
+
+- Request from application is sent towards resource brokering FE.
+- The resource brokering FE triggers charging event to send charging information related to the invoked resource.
+- The charging FE generates CDR according to received charging information.
+- The charging FE sends CDRs to backend billing system.
+
+## 9.7 Application triggering procedure
+
+This procedure provides the service flows related to triggering an application (e.g., vote casting application for counting votes) by a resource (e.g., SMS). This service flow includes interaction of resource adaptor FE, resource brokering FE, service dispatcher FE and access control FE.
+
+In this service flow, the resource submits (messaging service) a message to an application which is deployed to count votes.
+
+
+
+```
+
+sequenceDiagram
+ participant RX as Resource X
+ participant RA as Resource Adaptor FE
+ participant RB as Resource brokering FE
+ participant SD as Service dispatcher FE
+ participant AC as Access control FE
+ participant App as Application
+
+ RX->>RA: 1. send message
+ RA->>RB: 2. Send req to locate application
+ RB->>SD: 3. Send req towards application
+ SD->>AC: 4. Send req for auth
+ AC->>App: 5. Send req to application
+ App->>App: 6. process request
+ App-->>RX: 7. Response
+
+```
+
+Sequence diagram illustrating the Application triggering procedure. The participants are Resource X, Resource Adaptor FE, Resource brokering FE, Service dispatcher FE, Access control FE, and Application. The steps are: 1. Resource X sends a message to Resource Adaptor FE. 2. Resource Adaptor FE sends a request to locate the application to Resource brokering FE. 3. Resource brokering FE sends a request towards the application to Service dispatcher FE. 4. Service dispatcher FE sends a request for authentication to Access control FE. 5. Access control FE sends a request to the application. 6. The application processes the request (self-loop). 7. The application sends a response back to Resource X.
+
+**Figure 9-11 – Application triggering procedure**
+
+- Resource X sends a message carrying vote information towards an application used for vote counts via resource adaptor FE.
+- Resource adaptor corresponding to resource X translates the API/protocol carrying the message and encloses the message content into a common message structure and send the message to resource brokering FE.
+- Resource brokering FE locates the corresponding application and sends the request to service dispatcher FE.
+- Service dispatcher FE interacts with other relevant functional elements (e.g., policy decision) for policy enforcement. Afterward service dispatcher FE generates message according to the API/protocol native to the application and encloses content received in common message structure. This message is sent to access control FE.
+- Access control FE performs the authentication and authorization and delivers the message to the application.
+- Application processes the message content to get the vote information and update the vote count accordingly.
+- Application sends a message confirmation response to the resource via different FEs.
+
+## 9.8 Procedure related to accessing resource in another NGN-SIDE
+
+Figure 9-12 describes the scenario in which an application deployed in a CSN node accesses the resource registered in a remote CSN node.
+
+
+
+```
+
+sequenceDiagram
+ participant App as Application
+ participant CSN1 as CSN Node1
+ participant CSN2 as CSN Node2
+ participant Res as Resource
+
+ Note over CSN1: Access control FE, Service dispatcher FE, Resource registry FE, Resource routing FE
+
+ App->>CSN1: 1. Resource request
+ CSN1->>CSN1: 2. Resource request
+ CSN1->>CSN1: 3. Query resource information
+ CSN1-->>CSN1: 4. Response (unregistered resource)
+ CSN1->>CSN1: 5. Query resource routing information
+ CSN1-->>CSN1: 6. Resource routing information response
+ CSN1->>CSN1: 7. Response (resource routing information)
+ CSN1-->>App: 8. Response (resource routing information)
+ App->>CSN2: 9. Updated resource request
+ CSN2->>Res: 10. Updated resource request
+ Res->>CSN2: 11. Resource invoking
+ CSN2-->>CSN2: 12. Response (resource invoking)
+ CSN2-->>App: 13. Response (resource invoking)
+
+```
+
+Sequence diagram showing the procedure for accessing a resource in a remote CSN-Node. The diagram involves an Application, CSN Node1 (with Access control FE, Service dispatcher FE, Resource registry FE, and Resource routing FE), CSN Node2, and a Resource. The process starts with a resource request from the Application to CSN Node1, followed by internal queries and responses within CSN Node1. The request is then forwarded to CSN Node2, which invokes the Resource, and finally returns the response to the Application.
+
+**Figure 9-12 – Procedure related to accessing resource in remote CSN-Node**
+
+Procedure description:
+
+- Application sends resource request to CSN-Node1.
+- Access control FE in CSN-Node1 authenticates the resource request, and transfers it to service dispatcher FE upon successful authentication.
+- Service dispatcher FE queries resource information through resource registry FE.
+- Resource registry FE returns the query response, which indicates the resource does not register in this CSN-Node.
+- Service dispatcher FE queries resource routing information through resource routing FE.
+- Resource routing FE returns the routing information of the requested resource.
+- Service dispatcher FE transfers the routing information to access control FE.
+- Access control FE transfers the routing information to application.
+- Application sends updated resource request to CSN-Node2.
+
+- CSN-Node2 sends request to resource.
+- Resource is invoked.
+- Resource sends invoking response to CSN-Node2.
+- CSN-Node2 sends resource invoking response to application.
+
+# **10 Security considerations**
+
+The security requirements for the functional architecture of the NGN-SIDE are addressed by the security requirements identified in clause 8.4 of [ITU-T Y.2240].
+
+# Annex A
+
+## Interconnection between different NGN-SIDEs
+
+(This annex forms an integral part of this Recommendation.)
+
+NGN-SIDE in a particular NGN domain exposes its resources to the NGN-SIDE users. The NGN-SIDE users of a certain NGN-SIDE can only use the resources registered in that NGN-SIDE. In some circumstances (e.g., population density, geography), an NGN-SIDE provider can deploy distinct NGN-SIDEs in different NGN domains. These NGN-SIDEs can collaborate with each other to enable the users of an NGN-SIDE to access diverse resources available in other NGN-SIDEs.
+
+The interconnection of these NGN-SIDE forms the so called converged service network (CSN). Each NGN-SIDE in the CSN is known as CSN-Node. Figure A.1 shows the overall concept of CSN.
+
+
+
+The diagram illustrates the CSN conceptual view. At the top, a row of boxes represents 'Application 1', 'Application 2', an ellipsis, and 'Application m'. Below these is a large light-blue rounded rectangle labeled 'CSN'. Inside this rectangle, several smaller rounded rectangles represent 'CSN-node's, which are interconnected with each other. Arrows point from the application boxes down to the CSN-node boxes. Below the CSN rectangle is another row of boxes representing 'Resource 1', 'Resource 2', 'Resource 3', an ellipsis, and 'Resource n'. Arrows point from the CSN-node boxes down to the resource boxes. Dashed horizontal lines separate the applications from the CSN and the CSN from the resources. The text 'Y.2025(12)\_FA.1' is located at the bottom right of the diagram.
+
+Figure A.1 – CSN conceptual view
+
+**Figure A.1 – CSN conceptual view**
+
+As shown in Figure A.1, the CSN-Nodes are interconnected with each other in the CSN. Each CSN-Node manages one or multiple categories of resources.
+
+When resource requests from applications are received by CSN-Nodes, the CSN-Nodes schedule the resources for these applications, that is, select and invoke the requested resources.
+
+Figure A.2 shows the internal structure of a CSN-Node.
+
+
+
+The diagram shows the internal structure of a CSN-Node. It is a large light-gray rounded rectangle labeled 'CSN-Node' at the bottom. Inside, there are three main components: 'Resource routing FE' and 'Service dispatcher FE' are connected by a horizontal line. Below the 'Service dispatcher FE' is a stack of three boxes labeled 'Other NGN-SIDE FEs'. An external line enters the CSN-Node from the left and connects to the 'Resource routing FE'.
+
+Figure A.2 – CSN-Node internal structure
+
+**Figure A.2 – CSN-Node internal structure**
+
+The service dispatcher FE analyses the received resource request and queries the resource registry FE whether the requested resource is registered in this CSN-Node. When the requested resource is not registered in this CSN-Node, the service dispatcher FE sends the query request to the resource routing FE to acquire the routing information of the requested resource.
+
+When receiving the request, the resource routing FE queries the routing information of the requested resource in its storage and returns the routing information to the service dispatcher FE.
+
+The service dispatcher FE returns the routing information of the requested resource to the application, and the application will request the resource in another CSN-Node according to the routing information. Alternatively, the service dispatcher FE could directly route the resource request to the CSN-Node in which the resource registers.
+
+The CSN-Nodes can also be organized and interconnected in hierarchical mode. Figure A.3 provides the CSN conceptual view in n-tiers hierarchy.
+
+The CSN-Node on the top most tier (e.g., tier n-1) is responsible for the overall routing of resources in a hierarchical manner.
+
+NOTE – Applications accessing a specific CSN-Node can locate resources registered to any CSN node in any tier.
+
+When a CSN-Node on a particular tier (e.g., tier n) identifies that the requested resource is not locally registered but available in underlying CSN-Nodes, it routes the request to the CSN-Node on the lower tier (e.g., tier n+1). The CSN-Node (s) on the lower tier(s) then query(ies) the requested resource tier by tier until the resource is found.
+
+When a CSN-Node on a particular tier (e.g., tier n) identifies that the requested resource is not registered locally, it routes the request to the CSN-Node on the upper tier (e.g., tier n-1) or directly to the CSN-Node in the top most tier to locate the resource.
+
+
+
+Tier n-1
+
+Tier n
+
+Tier n+1
+
+Y.2025(12)\_FA.3
+
+Figure A.3 – CSN conceptual view in hierarchical mode. The diagram illustrates a three-tier hierarchy. Tier n-1 at the top contains an 'Application' (dashed blue box) connected to a 'CSN node' (solid yellow box), which is also connected to a 'Resource' (dashed green box). A dashed horizontal line separates Tier n-1 from Tier n. Tier n contains two 'CSN node' (solid yellow boxes). The left 'CSN node' is connected to an 'Application' (dashed blue box) and a 'Resource' (dashed green box). The right 'CSN node' is connected to a 'Resource' (dashed green box). A dashed horizontal line separates Tier n from Tier n+1. Tier n+1 at the bottom contains four 'CSN node' (solid yellow boxes). The leftmost 'CSN node' is connected to a 'Resource' (dashed green box). The second 'CSN node' is connected to a 'Resource' (dashed green box). The third 'CSN node' is connected to a 'Resource' (dashed green box). The rightmost 'CSN node' is connected to a 'Resource' (dashed green box).
+
+**Figure A.3 – CSN conceptual view in hierarchical mode**
+
+# **Appendix I**
+
+## **APIs for the NGN-SIDE functional architecture**
+
+(This appendix does not form an integral part of this Recommendation.)
+
+This Recommendation does not intend to define application programming interfaces (APIs) architectural aspects. The exposure of APIs for functional architecture of the NGN-SIDE is achieved according to requirements identified in clause 10.2.2 of [ITU-T Y.2240].
+
+For detailed information on APIs across different service interfaces, refer to the following clauses of [ITU-T Y.2240]:
+
+- 10.2.2 "NGN-SIDE service interfaces"
+- 10.2.2.1 "General requirements of NGN-SIDE service interfaces"
+- 10.2.2.2 "Service interface requirements across ANI"
+- 10.2.2.3 "Service interface requirements across UNI"
+- 10.2.2.4 "Service interface requirements across NNI"
+- 10.2.2.5 "Service interface requirements across SNI"
+
+# Appendix II
+
+## Mapping between NGN-SIDE functional entities and NGN functional entities
+
+(This appendix does not form an integral part of this Recommendation.)
+
+The NGN-SIDE architecture is defined in accordance with [ITU-T Y.2012]. Therefore, its functionalities have a corresponding relationship with the NGN architecture. Figure 6-1 shows the location of NGN-SIDE in the NGN functional architecture.
+
+Table II.1 provides the relationships between the functional entities identified in this Recommendation and the functional entities in the NGN architecture [ITU-T Y.2012].
+
+**Table II.1 – Mapping between NGN-SIDE functional entities and NGN functional entities**
+
+| No. | NGN-SIDE functional entity | NGN functional entity | Remarks |
+|-----|--------------------------------------------------------------|---------------------------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| 1 | Content management FE | Content distribution and location control FE | Both control the distribution of content and gather the related information. |
+| 2 | Service orchestration FE | Application service coordination manager FE | Both handle the interaction of several resources or services. |
+| 3 | Context management FE | Application support user profile FE | Application support user profile FE in NGN support end user settings which include information related to the capabilities of the end user's terminal devices. |
+| 4 | Application provisioning FE | Application provisioning FE | Both support lifecycle management of the applications. |
+| 5 | Resource registry FE, role related information management FE | Identity management functions | Resource registry FE and role related information management FE provide support for IdM mechanisms. |
+| 6 | Role related information management FE, policy decision FE | Service authentication and authorization FE | Service authentication and authorization FE in NGN ensures that the end user has valid utilization rights for the requested service, and performs policy control at the service level. |
+| 7 | Resource adaptor FE | User signalling interworking FE, Network signalling interworking FE | The two FEs in NGN have the responsibility for the interworking for different types of application signalling, and these also the functions of the resource adaptor FE in NGN-SIDE. |
+
+**Table II.1 – Mapping between NGN-SIDE functional entities and NGN functional entities**
+
+| No. | NGN-SIDE
functional entity | NGN
functional entity | Remarks |
+|------------|---------------------------------------|----------------------------------|------------------------------------------------------------------------------------------------------------------------------------|
+| 8 | Access control FE | Application gateway FE | Both provide a secure open interfaces for the applications to use the resources. |
+| 9 | Policy decision FE | Policy decision FE | Both make decision regarding network resources and admission control bases on network policy rules, SLAs, and service information. |
+
+# Bibliography
+
+- [b-ITU-T I.312] ITU-T Recommendation I.312/Q.1201 (1992), *Principles of intelligent network architecture*.
+- [b-ITU-T Y.2001] ITU-T Recommendation Y.2001 (2004), *General overview of NGN*.
+- [b-ITU-T Y.2011] ITU-T Recommendation Y.2011 (2004), *General principles and general reference model for Next Generation Networks*.
+- [b-ITU-T Y.2201] ITU-T Recommendation Y.2201 (2009), *Requirements and capabilities for ITU-T NGN*.
+- [b-ITU-T Y.2261] ITU-T Recommendation Y.2261 (2006), *PSTN/ISDN evolution to NGN*.
+
+
+
+# SERIES OF ITU-T RECOMMENDATIONS
+
+| | |
+|-----------------|--------------------------------------------------------------------------------------------------|
+| Series A | Organization of the work of ITU-T |
+| 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 | 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 |
\ No newline at end of file
diff --git a/marked/Y/T-REC-Y.2056-201108-I_PDF-E/raw.md b/marked/Y/T-REC-Y.2056-201108-I_PDF-E/raw.md
new file mode 100644
index 0000000000000000000000000000000000000000..a757a198ea179182d439ce526b30d2759ed94168
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@@ -0,0 +1,512 @@
+
+
+I n t e r n a t i o n a l T e l e c o m m u n i c a t i o n U n i o n
+
+# ITU-T
+
+TELECOMMUNICATION
+STANDARDIZATION SECTOR
+OF ITU
+
+## Y.2056
+
+(08/2011)
+
+SERIES Y: GLOBAL INFORMATION
+INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS
+AND NEXT-GENERATION NETWORKS
+
+Next Generation Networks – Frameworks and functional
+architecture models
+
+# --- **Framework of vertical multihoming in IPv6-based next generation networks**
+
+Recommendation ITU-T Y.2056
+
+
+
+The logo of the International Telecommunication Union (ITU) is located in the bottom right corner. It features a blue globe with two red lightning bolts striking it. To the right of the globe, the text "ITU" is written in a large, bold, blue font, and below it, the words "International Telecommunication Union" are written in a smaller, blue font.
+
+ITU logo: A blue globe with red lightning bolts and the text 'ITU International Telecommunication Union'.
+
+## ITU-T Y-SERIES RECOMMENDATIONS **GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS AND NEXT- GENERATION NETWORKS**
+
+## GLOBAL INFORMATION INFRASTRUCTURE
+
+| | |
+|-------------------------------------------|-------------|
+| General | Y.100–Y.199 |
+| Services, applications and middleware | Y.200–Y.299 |
+| Network aspects | Y.300–Y.399 |
+| Interfaces and protocols | Y.400–Y.499 |
+| Numbering, addressing and naming | Y.500–Y.599 |
+| Operation, administration and maintenance | Y.600–Y.699 |
+| Security | Y.700–Y.799 |
+| Performances | Y.800–Y.899 |
+
+## INTERNET PROTOCOL ASPECTS
+
+| | |
+|--------------------------------------------------------------------|---------------|
+| General | Y.1000–Y.1099 |
+| Services and applications | Y.1100–Y.1199 |
+| Architecture, access, network capabilities and resource management | Y.1200–Y.1299 |
+| Transport | Y.1300–Y.1399 |
+| Interworking | Y.1400–Y.1499 |
+| Quality of service and network performance | Y.1500–Y.1599 |
+| Signalling | Y.1600–Y.1699 |
+| Operation, administration and maintenance | Y.1700–Y.1799 |
+| Charging | Y.1800–Y.1899 |
+| IPTV over NGN | Y.1900–Y.1999 |
+
+## NEXT GENERATION NETWORKS
+
+| | |
+|-------------------------------------------------------------------|----------------------|
+| Frameworks and functional architecture models | Y.2000–Y.2099 |
+| Quality of Service and performance | Y.2100–Y.2199 |
+| Service aspects: Service capabilities and service architecture | Y.2200–Y.2249 |
+| Service aspects: Interoperability of services and networks in NGN | Y.2250–Y.2299 |
+| Numbering, naming and addressing | Y.2300–Y.2399 |
+| Network management | Y.2400–Y.2499 |
+| Network control architectures and protocols | Y.2500–Y.2599 |
+| Smart ubiquitous networks | Y.2600–Y.2699 |
+| Security | Y.2700–Y.2799 |
+| Generalized mobility | Y.2800–Y.2899 |
+| Carrier grade open environment | Y.2900–Y.2999 |
+| Future networks | Y.3000–Y.3099 |
+
+*For further details, please refer to the list of ITU-T Recommendations.*
+
+## **Recommendation ITU-T Y.2056**
+
+# **Framework of vertical multihoming in IPv6-based next generation networks**
+
+## **Summary**
+
+Recommendation ITU-T Y.2056 describes a framework for vertical multihoming in IPv6-based next generation networks (NGN). This Recommendation provides the definition, requirements, methods, functional architecture and applications of vertical multihoming in IPv6-based NGN.
+
+## **History**
+
+| Edition | Recommendation | Approval | Study Group |
+|---------|----------------|------------|-------------|
+| 1.0 | ITU-T Y.2056 | 2011-08-06 | 13 |
+
+## **Keywords**
+
+IPv6, multihoming, NGN, vertical multihoming.
+
+## 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 .
+
+© ITU 2012
+
+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 ..... | 3 |
+| 6 Description of vertical multihoming in IPv6-based NGN..... | 3 |
+| 7 Requirements of vertical multihoming in IPv6-based NGN ..... | 4 |
+| 7.1 Multihoming features and requirements of each layer ..... | 4 |
+| 7.2 Interaction across several layers ..... | 5 |
+| 7.3 Resource management of vertical multihoming..... | 5 |
+| 7.4 Other requirements for vertical multihoming..... | 6 |
+| 8 Methods of vertical multihoming ..... | 6 |
+| 8.1 Methods of vertical multihoming in terms of correspondence between
IPv6 address and interface..... | 6 |
+| 8.2 Methods of vertical multihoming in terms of supporting layers ..... | 7 |
+| 9 Functional architecture of vertical multihoming ..... | 9 |
+| 9.1 Functional architecture of vertical multihoming on the host side ..... | 9 |
+| 9.2 Overall architecture of vertical multihoming on the network side..... | 10 |
+| 10 Applications of vertical multihoming..... | 11 |
+| 10.1 Use cases related to lower layer ..... | 11 |
+| 10.2 Use cases related to upper layer ..... | 13 |
+| 11 Security considerations ..... | 14 |
+| Bibliography..... | 15 |
+
+
+
+## Recommendation ITU-T Y.2056
+
+# Framework of vertical multihoming in IPv6-based next generation networks
+
+## 1 Scope
+
+As heterogeneous access technologies have been developed, network nodes have been given the ability to simultaneously connect multiple access networks to support reliability, load sharing and mobility. These simultaneous multiple connections are established through multiple accesses to next generation networks (NGNs) using multiple access technologies, multiple network interfaces, multiple Internet Protocol version 6 (IPv6) addresses and multiple transport sessions.
+
+To provide efficient simultaneous multiple connections, it is required to consider the impact from/on multiple access technologies, multiple network interfaces and multiple transport sessions. This Recommendation defines vertical multihoming as multihoming based on the characteristics of simultaneous multiple connections of several layers, which are managed vertically across several layers. This Recommendation describes a framework of vertical multihoming in IPv6-based NGN.
+
+This Recommendation describes or defines:
+
+- vertical multihoming;
+- requirements of vertical multihoming;
+- methods of vertical multihoming;
+- functional architecture of vertical multihoming;
+- applications of vertical multihoming.
+
+## 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 published regularly. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation.
+
+- | | |
+|----------------|--------------------------------------------------------------------------------------------------------------------------|
+| [ITU-T Y.2001] | Recommendation ITU-T Y.2001 (2004), General overview of NGN . |
+| [ITU-T Y.2011] | Recommendation ITU-T Y.2011 (2004), General principles and general reference model for Next Generation Networks . |
+| [ITU-T Y.2051] | Recommendation ITU-T Y.2051 (2008), General Overview of IPv6-based NGN . |
+| [ITU-T Y.2052] | Recommendation ITU-T Y.2052 (2008), Framework of multi-homing in IPv6-based NGN . |
+| [ITU-T Y.2701] | Recommendation ITU-T Y.2701 (2007), Security requirements for NGN release 1 . |
+
+## 3 Definitions
+
+### 3.1 Terms defined elsewhere
+
+This Recommendation uses the following terms defined elsewhere:
+
+**3.1.1 IPv6-based NGN** [ITU-T Y.2051]: This refers to NGN that supports addressing, routing protocols and services associated with IPv6. An IPv6-based NGN shall recognize and process the IPv6 headers and options, operating over various underlying transport technologies in the transport stratum.
+
+**3.1.2 IPv6 multihoming** [ITU-T Y.2052]: A feature of an IPv6 host and/or IPv6 network that enables the host or network to be multihomed to networks through multiple network interfaces and multiple IPv6 addresses.
+
+**3.1.3 fault tolerance** [b-ITU-T E.800]: The attribute of an item that makes it able to perform a required function in the presence of certain given sub-item faults.
+
+**3.1.4 load balancing** [ITU-T Y.2052]: A scheme by which the traffic load could be separated and balanced to effectively utilize the network resources (e.g., link bandwidth).
+
+**3.1.5 network interface** [ITU-T Y.2052]: A device to be used by a node to connect to a network.
+
+### 3.2 Terms defined in this Recommendation
+
+This Recommendation defines the following terms:
+
+**3.2.1 multihoming**: Multiple links between an end-point and one or more transport networks. Multihoming may be used, for example, for load balancing or protection via diverse routes.
+
+**3.2.2 vertical multihoming**: A feature of multihoming based on the characteristics of simultaneous multiple connections of several layers which are managed vertically across several layers.
+
+## 4 Abbreviations and acronyms
+
+This Recommendation uses the following abbreviations and acronyms:
+
+| | |
+|------|------------------------------------------|
+| DCCP | Datagram Congestion Control Protocol |
+| IP | Internet Protocol |
+| IPv4 | Internet Protocol version 4 |
+| IPv6 | Internet Protocol version 6 |
+| MAC | Media Access Control |
+| NACF | Network Attachment Control Functions |
+| NGN | Next Generation Networks |
+| OS | Operating System |
+| PHY | PHYsical Layer |
+| QoS | Quality of Service |
+| RACF | Resource and Admission Control Functions |
+| SCTP | Stream Control Transmission Protocol |
+| TCP | Transmission Control Protocol |
+| UDP | User Datagram Protocol |
+
+## **5 Conventions**
+
+None.
+
+## **6 Description of vertical multihoming in IPv6-based NGN**
+
+IPv6-based NGN [ITU-T Y.2051], as one example of NGN, consists of a core network and heterogeneous access networks which allows flexible use of various interfaces. In addition, by using IPv6 multihoming capability [ITU-T Y.2052], a network and/or a network node are able to have multiple network connections via multiple network interfaces with multiple IPv6 addresses.
+
+Although a network and/or a network node have multiple network connections with IPv6 multihoming, generally, it uses only one network connection at one time. Other network connections remain to prepare for a secondary (backup) connection and are used for special cases such as fault tolerance, providing higher bandwidth, load balancing, and mobility. There is a difference between providing multiple network connections and providing simultaneous multiple network connections with respect to how many network connections are being utilized at a given moment.
+
+As heterogeneous access technologies are widely deployed in NGN, an NGN node can have the ability to connect various access networks simultaneously [ITU-T Y.2001] and [ITU-T Y.2011]. In multiple network connections due to heterogeneous access networks, many layers are used to establish multiple network connections.
+
+From the point of view of the physical (PHY)/media access control (MAC) layer, there may be multiple network interfaces/MAC protocols which are directly related to each access technology, and these multiple network interfaces/MAC protocols may be simultaneously used. So, in PHY/MAC layer, there are multiple link layer connections to communicate with other nodes.
+
+From the network layer's aspect, there may be multiple IPv6 addresses/IPv6 prefixes which are simultaneously used to establish multiple communication paths. So, in the network layer, there are multiple network layer connections to communicate with other nodes.
+
+From the transport layer's aspect, there may be multiple transport layer sessions which are simultaneously used.
+
+When considering how multiple network connections are established, each layer has a specific role for multiple network connections. Multiple network connections are made with the help of each layer and there is no interaction or relationship between the layers. However, to make efficient multiple network connections and manage these connections, it is required to consider the interaction and the relationship between layers. To do this, the concept of 'vertical multihoming' is used. In vertical multihoming, each layer has its specific multihoming features, which should be harmonized between layers. Figure 1 shows the multihoming of each layer and vertical multihoming. This Recommendation defines vertical multihoming as multihoming based on the characteristics of simultaneous multiple connections of several layers, which are managed vertically across several layers.
+
+
+
+Figure 1 – Concept of vertical multihoming. The diagram illustrates a network architecture between Host 1 and Host 2. Host 1 (left) and Host 2 (right) both have a five-layer protocol stack: Application layer, Transport layer, Network layer, MAC layer, and Physical layer. On Host 1, each layer is associated with a 'vertical multihoming' feature, represented by an oval. The network between the hosts consists of an IPv6-based core network (cloud) connected to three IPv6-based access networks (clouds labeled 1, 2, and 3) on the left and two IPv6-based access networks (clouds) on the right. Dashed lines connect the corresponding layers of Host 1 and Host 2, indicating communication paths through the various access and core networks.
+
+**Figure 1 – Concept of vertical multihoming**
+
+In vertical multihoming, each layer has multihoming features and many network resources are used to establish multiple network connections. In PHY/MAC layer, multiple access technologies, multiple network interfaces, and multiple radios are network resources. In the network layer, multiple IPv6 addresses and multiple IPv6 prefixes are network resources. In the transport layer, multiple transport sessions are network resources. To establish multiple network connections and manage network resources efficiently, an integrated and harmonized network management is needed.
+
+## 7 Requirements of vertical multihoming in IPv6-based NGN
+
+With regard to the requirements of multihoming for IPv6-based NGN, the general, site specific, and host specific requirements are described in [ITU-T Y.2052]. As vertical multihoming is based on characteristics of multiple connections, which are simultaneously used, supported by several layers, and managed vertically across the layers, the requirements specific to the vertical multihoming involve not only the network layer but also other layers. This clause first describes aspects of each layer for vertical multihoming. Then, it describes the requirement of interaction across several layers. Because vertical multihoming is related to several layers, which have their own resources, management of the resources is one of the important topics to be considered for vertical multihoming.
+
+### 7.1 Multihoming features and requirements of each layer
+
+Generally, IPv6 multihoming means that a feature of IPv6 hosts and/or an IPv6 network enables the host and/or network to be multihomed to networks through multiple network interfaces and multiple IPv6 addresses. To provide multiple network connections, it is not only IPv6-multihoming, but also multihoming features of other layers that play an important role.
+
+In PHY/MAC layer, there may be many PHY entities (e.g., physical interfaces, radios or channels) and many MAC entities (e.g., MAC protocols). If it is assumed that the connection on the PHY/MAC layer is a link layer connection, then there are many link layer connections due to heterogeneous access networks. As heterogeneous access technologies and access networks have been deployed in IPv6-based NGN, a host can use multihoming features of the link layer such as multiple radios, multiple channels, multiple interfaces and multiple MAC protocols. Using these multihoming features makes it possible to establish multiple link layer connections. For vertical multihoming, multiple link layer connections are required to be provided and these multiple link layer connections are required to be simultaneously enabled and utilized. And these multiple link layer connections are required to be harmonized with above network layer connections.
+
+In the network layer, for multihoming features, multiple IPv6 addresses and multiple IPv6 prefixes are used. By using this IPv6 multihoming, multiple network connections are established at the network layer. For vertical multihoming, multiple network layer connections are required to be provided and these multiple network layer connections are required to be simultaneously enabled and utilized. Also, these multiple network layer connections are required to be harmonized with link layer connections and transport layer connections.
+
+In the transport layer, for multihoming features, multiple transport streams and ports are used. By using these multihoming features, multiple transport connections are established at the transport layer. For vertical multihoming, these multiple transport layer connections are required to be provided and these multiple transport layer connections are required to be simultaneously enabled and utilized. These transport layer connections are also required to be harmonized with link layer connections and network layer connections.
+
+### **7.2 Interaction across several layers**
+
+Generally, the layer concept (e.g., Transmission Control Protocol (TCP)/IP Protocol suites) simplifies design, implementation, and testing by partitioning the overall communications process. Protocols in each layer can be designed separately from those in other layers. The layer concept provides flexibility for modifying and evolving protocols and services without having to change layers above or below. Typically, the architecture and services of the Internet have been developed based on this layer concept and operated properly.
+
+In NGN environments, where a host has the capability to connect to heterogeneous access networks and simultaneously use multiple connections, there is a strong need to modify the current layer concept. For example, a cross-layer mechanism could redesign the layer concept by interconnecting the layers. It could include the creation of new interfaces, the merging of adjacent layers, and designing coupling without new interfaces. Similarly, for vertical multihoming, interaction across several layers is needed.
+
+Figure 1 depicts multihoming for each layer: physical layer multihoming, MAC layer multihoming, network layer multihoming, transport layer multihoming and application layer multihoming. If the multihoming of each layer is not managed in an integrated fashion, it would seem that the synergy effects of multihoming of each layer is not good. For example, if there are multiple link layer connections at the PHY/MAC layer and multiple network layer connections at the network layer and there is no interaction between two adjacent layers, the network layer would not know how many link layer connections are provided for them. Without knowing the below link layer connection characteristics, it would be difficult to efficiently utilize network layer connections. Similarly, multiple transport connections are required to interact with below network layer connections and link layer connections to ensure efficient utilization. So, for vertical multihoming, the interaction across several layers is required.
+
+### **7.3 Resource management of vertical multihoming**
+
+Vertical multihoming is related to several layers; the PHY/MAC layer, network layer, transport layer, and application layer. In each layer, there are specific network resources. In the PHY/MAC layer, wired/wireless interfaces, radios and channels are included. In the network layer, IPv6 address and IPv6 prefix are network resources. In the transport layer, transport streams and port numbers are network resources. If the legacy layer concept is considered, network resources at each layer do not directly affect other network resources at an adjacent layer. But, in vertical multihoming, due to the interaction across several layers, network resources at one layer affect other adjacent layers. So, it is required to manage network resources in different ways.
+
+As described in clause 7.2, in vertical multihoming, interaction between adjacent layers is required and network resources in adjacent layers affect other layers. In vertical multihoming, network resources are required to be managed in an integrated fashion, which differs from the legacy layer concept. Also it is required to consider the effect of using network resources in one layer on an adjacent layer.
+
+### **7.4 Other requirements for vertical multihoming**
+
+For vertical multihoming, the following requirements are required to be satisfied in order to handle multiple network interfaces and multiple network connections efficiently.
+
+- Routing optimization through multiple network connections over multiple interfaces: Routing optimization focuses on choosing the data path on multiple network connections for forwarding data efficiently in terms of diverse application requirements.
+- Quality of Service (QoS) based connection selection over multiple network connections: In heterogeneous environments, each network interface technology has different transmission capabilities. Hence, the multihomed host can forward data through different routing paths with different transmission capabilities over multiple network connections established with multiple network interfaces. Also, dividing data streaming among different network interfaces can increase transmission capabilities through simultaneous usage of multiple network interfaces.
+- Bandwidth utilization over multiple network connections: Bandwidth utilization is to provide better transmission stability, reliability and performance. Hence, the issues affecting bandwidth utilization are how to separate data streams and how to recombine data streams over multiple network connections.
+- Recovery scheme for network interface failure: When the original network interface used for data transmission fails because of the link disconnection problem in the link layer or the routing problem in the network layer, the multihomed host is required to perform a fast connection recovery by using any available network interface in the multihomed host.
+- Network interface selection: Network interface selection defines which network interfaces to use and when to change them, depending on the network interface selection algorithm and policy. The selection takes into account chosen parameters such as signal strength, transmission rate, service stability and reliability.
+
+## **8 Methods of vertical multihoming**
+
+This clause introduces several methods of vertical multihoming in terms of how network addresses correspond to interfaces and to what extent the relevant capabilities of layers are involved.
+
+### **8.1 Methods of vertical multihoming in terms of correspondence between IPv6 address and interface**
+
+In a vertical multihoming environment, there are two different methods for establishing multiple network connections according to the number of IPv6 addresses as follows:
+
+- Multiple network connections through a unique IPv6 address per interface.
+- Multiple network connections through a shared IPv6 address per interface.
+
+In the first method, where the multihomed host is assigned the unique IPv6 address per interface, the multihomed host can send and receive packets simultaneously over the multiple network connections established with a network host through the unique IPv6 address assigned to an interface. As shown in Figure 2-a, this method shows that the multihomed host is able to create multiple connectivity via multiple network interfaces and uses multiple network interfaces simultaneously for sending and receiving packets without a particular IPv6 stack support. Since a
+
+particular application which wants to establish multiple network connections contacts a network host by creating a client-local TCP/User Datagram Protocol (UDP) socket of the transport layer with a unique IPv6 address assigned to multiple network interfaces, that is, from the application's perspective, there may exist multiple network connections between the multihomed hosts.
+
+
+
+Figure 2: Multiple network connections through (a) a unique IPv6 address per interface and (b) a shared IPv6 address per interface. Diagram (a) shows a stack of five layers: Application layer, Transport layer, Network layer (multiple IPv6), MAC layer, and Physical layer. Arrows from the Application and Transport layers converge at the Network layer, which then branches out to multiple Physical layers. Diagram (b) shows a similar stack, but the Network layer is labeled '(single IPv6)'. Arrows from the Application and Transport layers converge at the Network layer, which then branches out to multiple Physical layers. Below diagram (b) is the text 'Y.2056(11)\_F02'.
+
+**Figure 2 – Multiple network connections through (a) a unique IPv6 address per interface and (b) a shared IPv6 address per interface**
+
+In the second method, the multihomed host is assigned the shared IPv6 address across multiple network interfaces. Although this method makes only one IPv6 address visible to the application, the multihomed host is able to access heterogeneous networks through multiple network interfaces. Therefore, it uses multiple network resources which can be accessed by multiple network interfaces. However, in this method, although a particular application in the multihomed host wants to establish multiple network connections with a network host, the application is not able to establish multiple network connections. Since the application does not know how to support multiple network interfaces, a particular function for the establishment of multiple network connections is needed in the IPv6 stack. Here, the function may perform the flow assignment for an application flow to be serviced on a particular network interface.
+
+### 8.2 Methods of vertical multihoming in terms of supporting layers
+
+To support vertical multihoming in an IPv6-based NGN, not only the IPv6 network layer but also other layers/stratums are to be considered. To provide optimal vertical multihoming, it is better to ensure all layers/stratum have multihoming capabilities. However, in reality, this is difficult to achieve. Vertical multihoming is related to several layers and each layer may have different capabilities to support vertical multihoming. This clause classifies the methods of vertical multihoming in terms of supporting layers.
+
+If the methods of vertical multihoming are classified as the multihoming capabilities of each layer, there are the following methods for providing vertical multihoming:
+
+- multiple network connections through the multihoming capabilities of the PHY/MAC layer;
+- multiple network connections through the multihoming capabilities of the PHY/MAC and network layers;
+- multiple network connections through the multihoming capabilities of the PHY/MAC, network and transport layers;
+- multiple network connections through the multihoming capabilities of the PHY/MAC, network, transport and application layers.
+
+
+
+| | | | |
+|---------------------------------------|---------------------------------------|---------------------------------------|---------------------------------------|
+| Original application | Original application | Original application | Multihoming features in application |
+| Original TCP/UDP/SCTP/DCCP | Original TCP/UDP/SCTP/DCCP | Multihoming features in SCTP/DCCP | Multihoming features in SCTP/DCCP |
+| Original IPv6 | Multihoming features in IPv6 | Multihoming features in IPv6 | Multihoming features in IPv6 |
+| Multihoming features in PHY/MAC layer | Multihoming features in PHY/MAC layer | Multihoming features in PHY/MAC layer | Multihoming features in PHY/MAC layer |
+
+(a) (b) (c) (d)
+
+Y.2056(11)\_F03
+
+**Figure 3 – Multiple network connections through the multihoming capabilities of each layer**
+
+In the first method, the host adopts multihoming features in the PHY/MAC layer such as multiple interfaces, multiple channels, multiple radios, and multiple MAC protocols, but other layers do not support multihoming. Due to the overheads and cost of modification of the original network layer, the transport layer and application layer, it is difficult to modify other layers all at once, to support multihoming at each layer. For specific applications and/or a specific operating system (OS), it may be difficult to modify them to support vertical multihoming. In this method, the host must have a capability to handle multihoming features in the PHY/MAC layer even though the original network layer and transport layer do not support multihoming features in the PHY/MAC layer.
+
+In the second method, the host adopts multihoming features in the PHY/MAC layer and network layer but other layers such as the transport layer and application layer are not aware of the existence of multihoming features in the PHY/MAC layer and network layer. In this method, the host must have a capability to effectively combine multihoming features in the PHY/MAC layer and multihoming features in the network layer. Also, a host must have a capability to handle multihoming features in the PHY/MAC layer and network layer even though the original transport layer and application layer do not support multihoming features in the PHY/MAC layer and network layer.
+
+In the third method, the host adopts multihoming features in the PHY/MAC layer, network layer, and transport layer but the application layer is not aware of the existence of these multihoming features in the other layers. It seems that existing TCP/UDP could not have the capability to support multihoming features and it seems that Stream Control Transmission Protocol (SCTP) [b-IETF RFC 2960]/Datagram Congestion Control Protocol (DCCP) [b-IETF RFC 4340] could have the capability to support multihoming features. In this method, the host must have a capability to effectively combine multihoming features among the PHY/MAC layer, network layer, and transport layer. Also, a host must have a capability to handle multihoming features in the PHY/MAC layer, network layer, and transport layer even though the original application layer does not support multihoming features in other layers.
+
+In the fourth method, the host adopts multihoming features in every layer and it is the ultimate vertical multihoming. So, there are multiple connection characteristics of each layer and these characteristics may be simultaneously utilized and managed vertically across several layers. In this method, a host must have a capability to interact multihoming features across several layers and a resource management scheme for vertical multihoming.
+
+## 9 Functional architecture of vertical multihoming
+
+As described in clause 7, the requirements of vertical multihoming in an IPv6-based NGN include the requirements of multihoming in an IPv6-based NGN as described in [ITU-T Y.2052]. As vertical multihoming is based on IPv6 multihoming, the requirements of vertical multihoming are also based on the requirements of IPv6 multihoming in IPv6-based NGNs.
+
+Also, the functional architecture of vertical multihoming is related to the functional architecture of multihoming in IPv6-based NGNs. Many functions and functional entities described in [ITU-T Y.2052] can be referred to, to provide vertical multihoming.
+
+In the functional architecture described in [ITU-T Y.2052], the main function and functional entities for multihoming in an IPv6-based NGN are located on the network side such as the network attachment control function (NACF), access network function, edge function, and core transport function.
+
+The functions for vertical multihoming on the network side are also related to functions for vertical multihoming on the host side. As the primary purpose of vertical multihoming is to provide efficient multiple connections by considering the multihoming characteristics of each layer, the functions for vertical multihoming on the host side is basically responsible for providing vertical multihoming and the functions for vertical multihoming on the network side assist the functions on the host side.
+
+### 9.1 Functional architecture of vertical multihoming on the host side
+
+To consider the requirements of vertical multihoming, most requirements are related to the host side.
+
+The required functions for vertical multihoming are as follows:
+
+- identifying resources on each layer;
+- resource management;
+- recognizing network status and adjust resources;
+- interaction across several layers.
+
+To provide these functions for vertical multihoming in IPv6-based NGN, these functions may be located on both the host side and the network side. This clause describes the required functions for vertical multihoming on the host side. As shown in Figure 1, multihoming features exist in each layer and vertical multihoming functions are related to multihoming features in each layer.
+
+
+
+The diagram illustrates the relationship between vertical multihoming functions and multihoming features in each layer. On the left, there is a vertical stack of four rectangular boxes representing different layers: 'Multihoming features in application', 'Multihoming features in SCTP/DCCP', 'Multihoming features in IPv6', and 'Multihoming features in PHY/MAC layer'. To the right of this stack is a single rectangular box labeled 'Vertical multihoming function'. Four horizontal lines connect each of the four layer boxes to a central vertical line. This central vertical line has four dots, each aligned with one of the horizontal lines, and a single line connects this central vertical line to the 'Vertical multihoming function' box. The label 'Y.2056(11)\_F04' is located at the bottom right of the diagram.
+
+Diagram showing the relationship between vertical multihoming functions and multihoming features in each layer.
+
+**Figure 4 – The relationship between vertical multihoming functions and multihoming features in each layer**
+
+For vertical multihoming, the resource identifying function, resource management function, network status recognize and adjust function, and interaction across layer functions are tightly coupled and interact closely. The basic capability of each function is as follows:
+
+
+
+Y.2056(11)\_F05
+
+Figure 5: Functions for vertical multihoming. A diagram showing four functions arranged in a 2x2 grid within a larger box. The functions are: Resource Identifying function (top-left), Resource management function (top-right), Network status Recognize and adjust function (bottom-left), and Interaction across layers function (bottom-right).
+
+**Figure 5 – Functions for vertical multihoming**
+
+- Resource identifying function: For vertical multihoming, there are many resources in each layer. It is important to identify what kind of resources are related to vertical multihoming and what kind of attribute of each resource has an influence on vertical multihoming. The resource identifying function identifies resources on each layer for vertical multihoming and gathers necessary information for resource management.
+- Resource management function: In vertical multihoming, a resource in one layer is closely related to resources in another layer. The role of the resource management function for vertical multihoming is to control and manage resources in each layer in an integrated fashion.
+- Network status recognize and adjust function: Because vertical multihoming deals with interactions between all layers and relates to the resources in each layer, it is important to precisely recognize the status of each layer. To satisfy the requirement of a specific service (such as guaranteeing end-to-end performance, guaranteeing minimum bandwidth for some applications), vertical multihoming is required to have the capability to adjust resources on each layer.
+- Interaction across layer function: For vertical multihoming, one specific layer must collaborate with other layers. The interaction across layer function manages the interaction between different layers for vertical multihoming.
+
+### 9.2 Overall architecture of vertical multihoming on the network side
+
+In clause 9.2 of [ITU-T Y.2052], the functional architecture to support multihoming is described. To provide functions for vertical multihoming on the network side, existing functional entities can be used to provide functions for vertical multihoming. In contrast to the functional architecture which is defined in [ITU-T Y.2052], the resource and admission control function (RACF) [b-ITU-T Y.2111] is required to participate in providing vertical multihoming. The following figure shows the overall architecture related to vertical multihoming on the network side.
+
+
+
+Y.2056(811)\_F06
+
+----- Control Media — Management
+
+Figure 6: Overall architecture of vertical multihoming on the network side. The diagram shows a layered architecture. At the top is 'Applications'. Below it is the 'Service stratum' (green box) containing 'Application support functions and service support functions' and 'Service control functions'. Below the service stratum is the 'Transport stratum' (yellow box). Inside the transport stratum is the 'IPv6-based transport control functions' (white box) containing 'IPv6 enabled network attachment control functions' and 'Resource and admission control functions'. Below the control functions is the 'IPv6-based transport functions' (white box) containing 'IPv6 enabled access network functions', 'IPv6 enabled edge functions', 'IPv6 enabled core transport functions', 'Gateway functions', and 'Media handling functions'. To the left is a vertical bar for 'Management functions'. To the right is a box for 'Other networks'. The architecture is bounded by 'UNI' (User Network Interface) on the left and 'NNI' (Network Network Interface) on the right. A legend at the bottom indicates: dashed line for Control, hatched box for Media, and solid line for Management.
+
+**Figure 6 – Overall architecture of vertical multihoming on the network side**
+
+## 10 Applications of vertical multihoming
+
+In IPv6-based NGN, NGN users will benefit from always-on connectivity, load sharing, traffic engineering, fault tolerance with redundancy, and session continuity with the help of IPv6 multihoming [ITU-T Y.2052]. With vertical multihoming, these use cases are also applied to IPv6-based NGN. Besides these use cases, vertical multihoming has additional use cases as follows.
+
+- use cases related to lower layer (e.g., PHY layer, MAC layer);
+- use cases related to upper layer (e.g., transport layer, application layer).
+
+### 10.1 Use cases related to lower layer
+
+Generally, a legacy user terminal utilizes one network interface for communication at a time. Even though it has multiple network interfaces, it does not utilize multiple network interfaces simultaneously. The reason why it uses a single interface at a time may be in compliance with the traditional TCP/IP layer concept and there is no need to use multiple interfaces simultaneously.
+
+In the traditional TCP/IP layer concept, typically, one network interface is directly related to one IP address. Even though IPv6 is widely deployed, this situation does not change. The big difference between IPv6 and Internet Protocol version 4 (IPv4) is that there is a greater number of IPv6 addresses available to the network entities for use. It is possible to use multiple IPv6 addresses per single network interface and multiple network interfaces in a host. So, it is possible to utilize multiple network connections using an abundant number of IPv6 addresses and multiple network interfaces. The benefit of IPv6 multihoming, usage of multiple network connections with multiple IPv6 addresses and multiple network interfaces is not increased as expected due to the inefficient relation between one IPv6 address and a single network interface.
+
+If a host has multiple interfaces and multiple IPv6 addresses, the relationship between them may exist in various ways and it may be dynamically changeable. Among multiple interfaces, some of them may be utilized (connected to an access network) and some of them may not be utilized (is not connected to an access network). Among multiple IPv6 addresses, some of them may be utilized (there is a routing path to communicate) and some of them may not be utilized (there is no routing path to communicate). If a host can recognize the existence of multiple interfaces and multiple IPv6 addresses and the utilized conditions of each interface and each IPv6 address, the host may find the optimal association between the network interface and IPv6 address.
+
+
+
+Y.2056(11)\_F07
+
+Diagram illustrating the relationship between multiple IPv6 addresses and multiple network interfaces. The top row shows IPv6 addresses: IPv6-1, IPv6-2, IPv6-3, ..., IPv6-n. The bottom row shows network interfaces: I/F-1, I/F-2, I/F-3, ..., I/F-n. Dashed lines connect each IPv6 address to every network interface, representing a multi-to-multi mapping.
+
+**Figure 7 – An example of the relationship in the multiplicity of network interfaces and IPv6 addresses**
+
+For example, in the traditional TCP/IP layer concept, one specific interface and one specific IPv6 address is combined at a starting time of communication. The selection of one IPv6 address among multiple IPv6 addresses and the selection of one network interface among multiple interfaces are completely independent. Even though there are lots of advantages of this independent layer concept, this complete independent layer concept cannot utilize the benefit of the existence of multiple interfaces and multiple IPv6 addresses. As there is no specific rule for combining a network interface and an IPv6 address and one IPv6 address and one network interface is selected for communication, there is no guarantee to select the optimal association between a network interface and an IPv6 address.
+
+After communication between the nodes start, the combination between specific network interfaces and specific IPv6 addresses cannot be modified. In communication mechanisms based on the traditional TCP/IP layer concept, the combination between a network interface and an IPv6 address should be used for the entire time of communication. During communication, if the relation combination between a network interface and an IPv6 address is modified, the communication is disrupted.
+
+Because there are multiple network interfaces and multiple IPv6 addresses for communication, a host can utilize multiple network interfaces and multiple IPv6 addresses simultaneously. But in the traditional TCP/IP layer mechanism, a host cannot utilize these multiplicities of network interfaces and IPv6 addresses.
+
+If vertical multihoming is used, it is possible to utilize these multiplicities of network interfaces and IPv6 addresses. Vertical multihoming can recognize the existence of multiple network interfaces and IPv6 addresses and coordinate them. One-to-one mapping between a network interface and an IPv6 address in traditional TCP/IP layer concept is enhanced to multi-to-multi mapping between them. The host can find optimal mapping between network interfaces and IPv6 addresses and dynamically update the combination between them to adapt to a changeable exterior environment.
+
+### 10.2 Use cases related to upper layer
+
+Generally the upper layer of IPv6 is the transport layer and application layer. In the traditional TCP/IP layer the concept, there is no relationship between IPv6 multihoming and upper layer operations. Even though so many IPv6 addresses and network interfaces exist, they do not directly affect the operations of the upper layer. Also, upper layer protocols such as TCP/UDP do not utilize the advantage of IPv6 multihoming and the multiplicity of multiple interfaces. If SCTP and multi-path TCP are utilized in the transport layer, the relationship between IPv6 multihoming and the upper layer should be enforced.
+
+
+
+The diagram shows a set of sessions at the top, labeled Session-1, Session-2, Session-3, followed by an ellipsis, and then Session-n. Below these are IPv6 addresses, labeled IPv6-1, IPv6-2, IPv6-3, followed by an ellipsis, and then IPv6-n. Dashed lines connect each session to every IPv6 address, forming a complete bipartite graph. This illustrates that a single session can be associated with multiple IPv6 addresses, and vice versa. The identifier 'Y.2056(11)\_F08' is located at the bottom right of the diagram.
+
+Diagram illustrating the relationship between multiple IPv6 addresses and multiple sessions in the transport layer.
+
+**Figure 8 – An example of the relationship in the multiplicity of IPv6 addresses and sessions in transport layer**
+
+In the traditional TCP/IP layer concept, typically, one TCP/UDP session is directly related to one IP address and it does not change even though IPv6 is widely deployed. If one TCP/UDP session could use multiple IPv6 addresses (and also multiple network interfaces), there are many benefits. If a host has multiple IPv6 addresses and multiple transport sessions, the relationship between them may exist in various ways and it may be dynamically changeable. From the point of the transport layer, among multiple IPv6 addresses, some of them may be utilized (to make an end-to-end connection) and some of them may not be utilized (there is no routing path to communicate). If a host can recognize the existence of multiple IPv6 addresses and multiple transport sessions and the conditions of each IPv6 address and transport sessions, the host may find the optimal association between the IPv6 address and transport session.
+
+For example, in the traditional TCP/IP layer concept, one specific IPv6 address and one specific session/port number are combined when the communication starts. The selection of an IPv6 address among multiple IPv6 addresses and the selection of a session/port number among multiple session/port numbers are completely independent. Even though there are lots of advantages of this independent layer concept, this complete independent layer concept cannot utilize the benefit of the existence of multiple IPv6 addresses and multiple session/port numbers. As there is no specific rule for combining an IPv6 address and session/port number and one IPv6 address and one session/port number is selected for communication, there is no guarantee to select the optimal association between an IPv6 address and a session/port number.
+
+After communication between the nodes starts, the combination between a specific IPv6 address and a specific session/port number cannot be modified. In communication mechanisms based on the traditional TCP/IP layer concept, the combination between an IPv6 address and a session/port number should be used for the entire time of communication. During communication, if the relationship of the combination between an IPv6 address and a session/port number is modified, the communication is disrupted. To solve the modification of an IPv6 address, it is possible to use another mobility management protocol such as Mobile IPv6 [b-IETF RFC 3775] and Proxy Mobile IPv6 [b-IETF RFC 5213].
+
+As there are multiple IPv6 addresses and multiple session/port numbers for communication, a host can use multiple IPv6 addresses and multiple session/port numbers simultaneously. But in the traditional TCP/IP layer mechanism, a host cannot utilize these multiplicities of IPv6 addresses and session/port numbers.
+
+As shown in Figure 8, in vertical multihoming it is possible to utilize these multiplicities of IPv6 addresses and session/port numbers. Vertical multihoming can recognize the existence of multiple IPv6 addresses and session/port numbers and coordinate them. One-to-one mapping between an IPv6 address and a session/port number in the traditional TCP/IP layer concept is enhanced to multi-to-multi mapping. The host can find optimal mapping between an IPv6 address and a session/port number and dynamically update the combination between them to adapt to a changeable exterior environment.
+
+For the application layer, vertical multihoming can coordinate between IPv6 addresses and session/port numbers and dynamically control the necessary QoS features.
+
+## **11 Security considerations**
+
+This Recommendation does not require any specific security considerations and aligns with the security requirements in [ITU-T Y.2701].
+
+## Bibliography
+
+- [b-ITU-T E.800] Recommendation ITU-T E.800 (1994), *Terms and definitions related to quality of service and network performance including dependability.*
+- [b-ITU-T Y.2111] Recommendation ITU-T Y.2111 (2008), *Resource and admission control functions in next generation networks.*
+- [b-IETF RFC 2960] IETF RFC 2960 (2000), *Stream Control Transmission Protocol.*
+- [b-IETF RFC 3775] IETF RFC 3775 (2004), *Mobility Support in IPv6.*
+- [b-IETF RFC 4340] IETF RFC 4340 (2006), *Datagram Congestion Control Protocol (DCCP).*
+- [b-IETF RFC 5213] IETF RFC 5213 (2008), *Proxy Mobile IPv6.*
+
+
+
+
+
+## SERIES OF ITU-T RECOMMENDATIONS
+
+| | |
+|-----------------|--------------------------------------------------------------------------------------------------|
+| Series A | Organization of the work of ITU-T |
+| 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 | 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 |
\ No newline at end of file
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@@ -0,0 +1,1239 @@
+
+
+I n t e r n a t i o n a l T e l e c o m m u n i c a t i o n U n i o n
+
+# ITU-T
+
+TELECOMMUNICATION
+STANDARDIZATION SECTOR
+OF ITU
+
+## Y.2082
+
+(08/2013)
+
+SERIES Y: GLOBAL INFORMATION
+INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS
+AND NEXT-GENERATION NETWORKS
+
+Next Generation Networks – Frameworks and functional
+architecture models
+
+---
+
+### **Distributed service networking relay functions**
+
+Recommendation ITU-T Y.2082
+
+
+
+The logo of the International Telecommunication Union (ITU) is located in the bottom right corner. It features a blue globe with a red lightning bolt striking it, and the text "ITU" in blue, with "International Telecommunication Union" in smaller blue text below it.
+
+ITU logo
+
+ITU-T Y-SERIES RECOMMENDATIONS
+
+**GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS AND NEXT-
+GENERATION NETWORKS**
+
+| | |
+|--------------------------------------------------------------------|----------------------|
+| GLOBAL INFORMATION INFRASTRUCTURE | |
+| General | Y.100–Y.199 |
+| Services, applications and middleware | Y.200–Y.299 |
+| Network aspects | Y.300–Y.399 |
+| Interfaces and protocols | Y.400–Y.499 |
+| Numbering, addressing and naming | Y.500–Y.599 |
+| Operation, administration and maintenance | Y.600–Y.699 |
+| Security | Y.700–Y.799 |
+| Performances | Y.800–Y.899 |
+| INTERNET PROTOCOL ASPECTS | |
+| General | Y.1000–Y.1099 |
+| Services and applications | Y.1100–Y.1199 |
+| Architecture, access, network capabilities and resource management | Y.1200–Y.1299 |
+| Transport | Y.1300–Y.1399 |
+| Interworking | Y.1400–Y.1499 |
+| Quality of service and network performance | Y.1500–Y.1599 |
+| Signalling | Y.1600–Y.1699 |
+| Operation, administration and maintenance | Y.1700–Y.1799 |
+| Charging | Y.1800–Y.1899 |
+| IPTV over NGN | Y.1900–Y.1999 |
+| NEXT GENERATION NETWORKS | |
+| Frameworks and functional architecture models | Y.2000–Y.2099 |
+| Quality of Service and performance | Y.2100–Y.2199 |
+| Service aspects: Service capabilities and service architecture | Y.2200–Y.2249 |
+| Service aspects: Interoperability of services and networks in NGN | Y.2250–Y.2299 |
+| Enhancements to NGN | Y.2300–Y.2399 |
+| Network management | Y.2400–Y.2499 |
+| Network control architectures and protocols | Y.2500–Y.2599 |
+| Packet-based Networks | Y.2600–Y.2699 |
+| Security | Y.2700–Y.2799 |
+| Generalized mobility | Y.2800–Y.2899 |
+| Carrier grade open environment | Y.2900–Y.2999 |
+| FUTURE NETWORKS | Y.3000–Y.3499 |
+| CLOUD COMPUTING | Y.3500–Y.3999 |
+
+*For further details, please refer to the list of ITU-T Recommendations.*
+
+# Recommendation ITU-T Y.2082
+
+## Distributed service networking relay functions
+
+### Summary
+
+Recommendation ITU-T Y.2082 specifies the architecture for relay function (RF), in support of application layer routing optimization for performance improvement and network address translation (NAT)/firewall traversal in the environment of distributed service networking (DSN) as described in Recommendation ITU-T Y.2080.
+
+Application layer routing optimization means the usage of application layer relays to change the route of data packets. Considering the case that the default transport layer route is congested, better performance can be achieved through application layer routing optimization.
+
+The main objectives of this Recommendation are to specify:
+
+- Functional entities of RF
+- Information flows related to RF
+- Reference points related to RF.
+
+### History
+
+| Edition | Recommendation | Approval | Study Group | Unique ID* |
+|---------|----------------|------------|-------------|---------------------------------------------------------------------------------|
+| 1.0 | ITU-T Y.2082 | 2013-08-13 | 13 | 11.1002/1000/11974-en |
+
+### Keywords
+
+Distributed service networking, DSN, functional architecture, relay, relay function, RF.
+
+---
+
+\* To access the Recommendation, type the URL in the address field of your web browser, followed by the Recommendation's unique ID. For example, .
+
+## 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 .
+
+© ITU 2014
+
+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..... | 2 |
+| 4 Abbreviations and acronyms ..... | 2 |
+| 5 Conventions ..... | 2 |
+| 6 Overview of relay functions ..... | 3 |
+| 7 RF functional architecture ..... | 4 |
+| 7.1 Architecture framework..... | 4 |
+| 7.2 Functional entities ..... | 4 |
+| 8 Procedures ..... | 5 |
+| 8.1 Relay procedures ..... | 5 |
+| 8.2 Relay node management procedures ..... | 15 |
+| 8.3 QoS measurement procedures ..... | 17 |
+| 9 Reference points ..... | 18 |
+| 9.1 Reference point C4 ..... | 18 |
+| Appendix I – Relay algorithms introduction..... | 24 |
+| I.1 Description of GNG algorithms ..... | 24 |
+| Bibliography..... | 27 |
+
+
+
+# Recommendation ITU-T Y.2082
+
+## Distributed service networking relay functions
+
+### 1 Scope
+
+This Recommendation specifies relay function (RF) support for network address translation (NAT)/firewall traversal and application layer routing optimization for service performance improvement in distributed service networking (DSN). Furthermore, it defines functional entities of RF, information flows related to RF, and detailed reference point descriptions related to RF.
+
+### 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 Y.2080] Recommendation ITU-T Y.2080 (2012), *Functional architecture of distributed service networking*.
+
+### 3 Definitions
+
+#### 3.1 Terms defined elsewhere
+
+This Recommendation uses the following terms defined elsewhere:
+
+**3.1.1 control node** [b-ITU-T Y.2000-series Sup.10]: A DSN node which provides service control functionalities.
+
+**3.1.2 distributed service networking (DSN)** [b-ITU-T Y.2206]: An overlay networking which provides distributed and manageable capabilities to support various multimedia services and applications.
+
+**3.1.3 DSN node** [b-ITU-T Y.2206]: A node used in DSN providing distributed functionalities, including distributed routing and distributed storage.
+
+**3.1.4 network address translation (NAT)** [b-ITU-T Y.2111]: The operation by which IP addresses are translated (mapped) from one address domain to another address domain.
+
+**3.1.5 point of presence (POP)** [b-ITU-T Y.2081]: A point representing one or several DSN nodes, which supports DSN users in accessing services directly without having intermediate DSN nodes.
+
+**3.1.6 reference point** [b-ITU-T Y.2012]: A conceptual point at the conjunction of two non-overlapping functional entities that can be used to identify the type of information passing between these functional entities.
+
+**3.1.7 relay node (RN)** [ITU-T Y.2080]: A DSN node which relays data packets in order to improve node reachability and quality of service (QoS) by changing the original route of the packets. The data can be voice data, video data, etc.
+
+**3.1.9 user profile** [ITU-T Y.2080]: In the context of the DSN functional architecture, a collection of information that specifies the subscribed services and access privileges related to a DSN service user. The data in the user profile is called user profile data.
+
+NOTE – A user profile may include the following attributes: user ID and other data related to authentication and authorization, user preferences, service status, service class, usage and/or contribution information, or subscriber accounting characteristics, etc.
+
+## 3.2 Terms defined in this Recommendation
+
+This Recommendation defines the following terms:
+
+**3.2.1 functional entity:** An entity that comprises an indivisible set of specific capabilities. Functional entities are logical concepts, while groupings of functional entities are used to describe practical, physical implementations.
+
+**3.2.2 relay:** A procedure to forward data packets from one entity to another entity according to a given policy.
+
+NOTE – In the context of this Recommendation, relay is used to achieve NAT/firewall traversal and QoS improvement.
+
+## 4 Abbreviations and acronyms
+
+This Recommendation uses the following abbreviations and acronyms:
+
+| | |
+|--------|-------------------------------------------------|
+| DSN | Distributed Service Networking |
+| EF | End-user Functions |
+| ID | Identifier |
+| MMTel | Multimedia Telephony |
+| NAT | Network Address Translation |
+| POP | Point Of Presence |
+| RF | Relay Functions |
+| RLF | Resource Location Functions |
+| RN | Relay Node |
+| RT-FE | Relay Transport Functional Entity |
+| RTT | Round Trip Time |
+| SCF | Service Control Functions |
+| TOCF | Traffic Optimization Control Functions |
+| TQM-FE | Transport Quality Measurement Functional Entity |
+| UE | User Equipment |
+
+## 5 Conventions
+
+The following conventions apply:
+
+- 1) The meaning of Functions is as follows:
+
+**Functions:** In the context of DSN architecture, "Functions" are defined as functional groups composed of functional entities. It is represented by the following symbol:
+
+## 6 Overview of relay functions
+
+RFs support relaying of particular application traffic for DSN nodes to achieve NAT/firewall traversal and quality of service (QoS) improvement. One or more relay node (RN) entities can be inserted into the data path to improve network performance. RF supports the following functions:
+
+- NAT or firewall traversal
+When one or more DSN nodes involved in DSN service are behind the NAT/firewall, RF can be used to support NAT/firewall traversal enabling those DSN nodes to communicate with other DSN nodes.
+- Routing optimization
+When the default route cannot meet the desired QoS requirements for DSN services, communicating parties can set up an alternative data path through RNs to improve network performances, e.g., packet loss rate, delay, jitter. It is also possible to set up multiple data paths through RNs to provide backups in case the main path is interrupted or congested.
+
+Figure 6-1 shows the position of RF in DSN functional architecture as defined in [ITU-T Y.2080].
+
+
+
+----- Control ..... Management
+
+Y.2082(13)\_F6-1
+
+Figure 6-1: The position of RF in DSN functional architecture. The diagram shows a blue-shaded area representing the DSN functional architecture. Inside, there are several functional blocks: 'Other AFs' (a blue box), 'CSAF' (a white box), 'EF' (a white box), 'SCF' (a white box), 'RLF' (a white box), 'RF' (a yellow box), 'TOCF' (a white box), 'NEF' (a white box), and 'CDF' (a white box). The blocks are interconnected by dashed lines representing control and management planes. Control plane connections are labeled A1, A2, A3, A4, A5, C1, C2, C3, C4, C5, C6, C7, C8, C9, and C10. Management plane connections are labeled A1, A2, A3, A4, A5, C1, C2, C3, C4, C5, C6, C7, C8, C9, and C10. The 'RF' block is highlighted in yellow. A red-shaded area on the right contains a block labeled 'MF'. A legend at the bottom left indicates that dashed lines represent 'Control' and dotted lines represent 'Management'. The reference 'Y.2082(13)\_F6-1' is located at the bottom right.
+
+**Figure 6-1 – The position of RF in DSN functional architecture**
+
+## 7 RF functional architecture
+
+### 7.1 Architecture framework
+
+Figure 7-1 describes the RF functional architecture with functional entities and relevant reference points. RF consists of the following FEs:
+
+- RT-FE (relay transport functional entity).
+- TQM-FE (transport quality measurement functional entity).
+
+The detailed functions of RT-FE and TQM-FE are described in clause 7.2.
+
+
+
+```
+graph LR
+ RLF[RLF]
+ subgraph Relay_functions [Relay functions]
+ TQM_FE[TQM-FE
+(Transport Quality Measurement FE)]
+ RT_FE[RT-FE
+(Relay Transport FE)]
+ end
+ Relay_functions -.->|C4-1| RLF
+ RLF -.->|C4-2| TQM_FE
+ RT_FE -.-> RLF
+```
+
+Figure 7-1: Relay functions functional architecture diagram. The diagram shows a Resource Location Function (RLF) box on the left and a large box on the right labeled 'Relay functions'. Inside the 'Relay functions' box are two smaller boxes: 'TQM-FE (Transport Quality Measurement FE)' on the left and 'RT-FE (Relay Transport FE)' on the right. A dashed arrow labeled 'C4-1' points from the 'Relay functions' box to the RLF box. A dashed arrow labeled 'C4-2' points from the RLF box to the TQM-FE box. A dashed arrow points from the RT-FE box to the RLF box. The reference 'Y.2082(13)\_F7-1' is at the bottom right.
+
+**Figure 7-1 – Relay functions functional architecture**
+
+### 7.2 Functional entities
+
+#### 7.2.1 Relay transport functional entity
+
+RT-FE is a functional entity that relays the data packet between DSN nodes. RT-FE also reports flow statistics and RN status to a resource location function (RLF). The functions performed by RT-FE include the following:
+
+- RT-FE registers RN to RLF.
+- RT-FE reserves resource for data packet relay.
+- RT-FE relays data packets for DSN nodes, including DSN nodes behind NAT/firewall.
+- RT-FE validates the legality of a DSN node when the DSN node sends data packet to RT-FE.
+- RT-FE buffers relayed data packets.
+- RT-FE reports relay task results (e.g., the duration and flow statistic) to RLF.
+- RT-FE forwards data packets from one input to several outputs.
+- RT-FE monitors RN status and reports status information to RLF. Status information includes CPU usage, memory usage, disk usage, and network interface usage, etc.
+- RT-FE monitors events and reports event related information to RLF when it occurs.
+
+NOTE – For example, an event includes the case when an RN load reaches a given threshold.
+
+#### 7.2.2 Transport quality measurement functional entity
+
+TQM-FE is a functional entity that performs QoS measurement for the data path starting from or ending by it. The functions of TQM-FE include the following:
+
+- TQM-FE receives measurement instructions from RLF and reports these measurement results as required by RLF.
+- TQM-FE measures the QoS parameters (e.g., delay, delay jitter, packet loss rate) on application flows.
+
+- TQM-FE can initiate a new measurement flow with a certain packet pattern to another TQM-FE to measure the application's QoS parameters, when requested by RLF.
+- NOTE – TQM-FE uses different connection methods for different types of measurements, e.g., TCP connections for measuring TCP QoS parameters, and UDP connections for measuring UDP QoS parameters.
+
+## 8 Procedures
+
+This clause describes how RFs interact with other DSN functions to provide relay services. The procedures in this clause apply for conversational services such as multimedia telephony (MMTel) or video conferencing.
+
+### 8.1 Relay procedures
+
+#### 8.1.1 General relay procedure
+
+Figure 8-1 shows the general relay procedure. The detailed relay procedures are illustrated in the following clauses in 8.1.
+
+The service control function (SCF) handles the service request and sets up the relay path between EFs. EFs may or may not be aware of the RN inserted into the data path.
+
+
+
+```
+
+sequenceDiagram
+ participant EFA as EF A
+ participant SCF as SCF
+ participant RLF as RLF
+ participant RF as RF
+RT-FE
+ participant EFB as EF B
+
+ EFA->>SCF: 1. Service request
+ SCF->>RLF: 2. Relay node request
+ Note over RLF: 3. Relay node selection
+ RLF->>RF: 4. Resource reservation request
+ RF-->>RLF: 5. Resource reservation response
+ RLF->>SCF: 6. Relay node information
+ Note over EFA, SCF, RLF, RF, EFB: 7. Data plane connection setting up
+ EFA<-->>RF: 8. Data traffic
+ RF<-->>EFB: 8. Data traffic
+ Note over SCF, RLF, RF: 9. Relay session information update
+
+```
+
+Sequence diagram illustrating the General relay procedure (Figure 8-1). The diagram shows the interaction between EF A, SCF, RLF, RF (RT-FE), and EF B. The steps are: 1. Service request from EF A to SCF; 2. Relay node request from SCF to RLF; 3. Relay node selection (local to RLF); 4. Resource reservation request from RLF to RF; 5. Resource reservation response from RF to RLF; 6. Relay node information from RLF to SCF; 7. Data plane connection setting up (a wide bar spanning all entities); 8. Data traffic (two large arrows between EF A and RF, and between RF and EF B); 9. Relay session information update (a bar spanning SCF, RLF, and RF).
+
+Y.2082(13)\_F8-1
+
+**Figure 8-1 – General relay procedure**
+
+1. EF A sends service request (e.g., the Invite message in a SIP session) to SCF to request DSN services.
+2. SCF sends RN request to RLF (which is in charge of managing RNs).
+NOTE 1 – Based on the user profile (e.g., whether the user has subscribed to the relay service), the requested service type, and the current access status of EF A or EF B (e.g., whether there are NAT/firewall devices), the SCF may determine that an RN is needed.
+3. Based on the EF addresses and the requested service, RLF locates and selects one or more suitable RNs for this request.
+
+4. Optionally, RLF may send a resource reservation request to RT-FE in the selected RNs to reserve relay resources.
+5. RT-FE reserves necessary resources and returns the information (e.g., the allocated port) about reserved resources.
+6. RLF returns the information of selected RNs to SCF.
+7. SCF sets up the data plane connection by informing EF A and EF B of the data plane addresses that they should connect to. One or more RNs could be inserted into the data path.
+8. EF A and EF B send data packets to each other through relay path.
+9. During the relay service, or after the relay service has been finished, RT-FE sends relay session information to RLF. RLF may forward the relay session information to SCF.
+
+NOTE 2 – A relay session is the process by which RN(s) relay packets for a given set of DSN nodes. The process includes relay resource reservation, connection set up, and data packet forwarding. A relay session is identified through the relay session ID.
+
+NOTE 3 – Relay session information includes the source/destination addresses, the RN ID, the amount of traffic relayed, and the duration of the relay session.
+
+### 8.1.2 Relay node selection procedures
+
+In the processes of RN selection, there are several factors to be considered, such as RN capabilities, round-trip time (RTT) values, etc. These factors can be classified into following three categories.
+
+- 1) Network capabilities, including RTT, available bandwidth, IP address type, etc.
+- 2) System capabilities, including cumulative online time, join/leave frequency, etc.
+- 2) Physical capabilities, including available processing power, available memory space, available disk space, etc.
+
+As different services require different kinds of capabilities, the selection procedure takes into account the service type and QoS requirements. For example, a latency-sensitive service such as MMTel or video conferencing, will first take into consideration the network capabilities related to delay in the selection of RNs.
+
+#### 8.1.2.1 Relay node selection procedure based on TOCF optimization
+
+Figure 8-2 shows the RN selection procedure based on TOCF optimization.
+
+
+
+```
+
+sequenceDiagram
+ participant SCF
+ participant RLF
+ participant TOCF
+ participant RF as RF (RT-FE)
+
+ SCF->>RLF: 1. Relay node request
+ RLF->>TOCF: 2. Relay optimization request
+ Note over TOCF: 3. POPs selection
+ TOCF->>RLF: 4. IDs of candidate POPs
+ Note over RLF: 5. Relay node selection
+ RLF->>RF: 6. Resource reservation request
+ RF-->>RLF: 7. Resource reservation response
+ RLF-->>SCF: 8. Selected relay node(s)
+
+```
+
+Sequence diagram showing the RN selection procedure based on TOCF optimization. The diagram involves four main entities: SCF, RLF, TOCF, and RF (containing RT-FE). The process starts with SCF sending a '1. Relay node request' to RLF. RLF then sends a '2. Relay optimization request' to TOCF. TOCF performs '3. POPs selection' and returns '4. IDs of candidate POPs' to RLF. RLF then performs '5. Relay node selection'. RLF sends a '6. Resource reservation request' to RF (RT-FE). RF returns a '7. Resource reservation response' to RLF. Finally, RLF sends '8. Selected relay node(s)' back to SCF.
+
+Y.2082(13)\_F8-2
+
+**Figure 8-2 – RN selection procedure based on TOCF optimization**
+
+1. SCF sends RN request to RLF, which indicates the IP addresses of source node and destination node, service type, and QoS requirement.
+ 2. RLF sends relay optimization request to TOCF for the IDs of the candidate POPs that represent the potential RNs that can meet the QoS requirement. The message includes IP addresses of the source node and the destination node.
+ 3. TOCF selects the candidate POPs based on topology information, traffic information and optimization policies. For example, TOCF can select POPs that have the lowest costs for paths connecting the source and destination node.
+ 4. TOCF returns the IDs of the candidate POPs to RLF.
+ 5. Based on the service type and QoS requirement, RLF further refines the RN selection policy and selects one or more RNs from the full list of candidate POPs.
+- NOTE 1 – Based on the QoS requirement, RLF sets the threshold for each capability. The RN capabilities are collected by RLF before the relay selection procedure. RNs that meet the capability thresholds will be selected as candidates. For conversational services that are delay-sensitive, the network capabilities of the RNs may be considered first.
+6. RLF sends resource reservation request to the selected RN(s).
+ 7. RN(s) return resource reservation response to RLF.
+- NOTE 2 – Step 6 and step 7 are optional if the RN request in step 1 does not specify a QoS requirement.
+8. RLF returns the information of the selected RN(s) to SCF.
+
+#### 8.1.2.2 RN selection procedure based on RLF optimization
+
+Figure 8-3 shows the RN selection procedure based on RLF optimization.
+
+
+
+```
+
+sequenceDiagram
+ participant SCF
+ participant RLF
+ participant TOCF
+ participant RF as RF (RT-FE)
+
+ SCF->>RLF: 3. Relay node request
+ RLF->>TOCF: 1. Map request
+ TOCF-->>RLF: 2. Map response (network map, cost map)
+ RLF->>TOCF: 4. Relay node selection
+ RLF->>RF: 5. Resource reservation request
+ RF-->>RLF: 6. Resource reservation response
+ RLF->>SCF: 7. Selected relay node
+
+```
+
+Y.2082(13)\_F8-3
+
+Sequence diagram showing the RN selection procedure based on RLF optimization. The diagram involves four entities: SCF, RLF, TOCF, and RF (containing RT-FE). The process starts with SCF sending a '3. Relay node request' to RLF. RLF then sends a '1. Map request' to TOCF, which responds with a '2. Map response (network map, cost map)'. RLF then performs '4. Relay node selection'. Next, RLF sends a '5. Resource reservation request' to RF, which responds with a '6. Resource reservation response'. Finally, RLF sends a '7. Selected relay node' back to SCF.
+
+**Figure 8-3 – RN selection procedure based on RLF optimization**
+
+1. RLF requests network map and cost map from TOCF periodically.
+- NOTE 1 – Network map is the mapping between the IP address and the ID of POP. Cost map is the mapping between a pair of POPs and its cost value.
+2. TOCF responds with network map and cost map to RLF.
+- NOTE 2 – Step 1 and step 2 are executed periodically.
+3. SCF sends RN request to RLF, which indicates the IP addresses of source node and destination node, service type, and QoS requirement.
+
+4. Based on network map and cost map, RLF selects the candidate POPs, and then, based on the service type and QoS requirement, RLF further refines the RN selection policy and selects one or more RNs from the full list of candidate POPs.
+
+NOTE 3 – Based on the QoS requirement, RLF sets the threshold for each capability. The RN capabilities are collected by RLF before the relay selection procedure. RNs that meet the capability thresholds will be selected as candidates. For conversational services that are delay-sensitive, the network capabilities of the RNs may be considered first.
+
+5. RLF sends resource reservation request to RT-FE of the selected RN(s).
+6. RT-FE returns resource reservation response to RLF.
+
+NOTE 4 – Step 5 and step 6 are optional if the RN request in step 3 does not specify a QoS requirement.
+
+7. RLF returns the information of selected RN(s) to SCF.
+
+### 8.1.2.3 Relay node selection procedure for data traffic from one source to multi-destinations
+
+Figure 8-4 shows the procedure where data packets are relayed from the source user equipment (UE) to its destination UEs, which can be used in the service like video conferencing. One or more RNs can be selected for different destinations.
+
+
+
+```
+
+sequenceDiagram
+ participant EF
+ participant SCF
+ participant RLF
+ participant RF1 as RF1 RT-FE
+ participant RF2 as RF2 RT-FE
+
+ EF->>SCF: 1. Service request
+ SCF->>RLF: 2. Relay node request
+ RLF->>RLF: 3. Relay node selection
+ RLF->>RF1: 4. Resource reservation request
+ RLF->>RF2: 4. Resource reservation request
+ RF1->>RLF: 5. Record the relationship
+ RF2->>RLF: 5. Record the relationship
+ RF1->>RLF: 6. Resource reservation response
+ RF2->>RLF: 6. Resource reservation response
+ RLF->>SCF: 7. Selected relay node(s)
+ SCF->>EF: 8. Selected relay node(s)
+ EF->>RF1: 9. Data traffic
+ EF->>RF2: 9. Data traffic
+ RF1->>Dest1: 10. Data traffic
+ RF1->>Dest2: 10. Data traffic
+ RF1->>Dest3: 10. Data traffic
+ RF2->>Dest4: 10. Data traffic
+ RF2->>Dest5: 10. Data traffic
+ RF2->>Dest6: 10. Data traffic
+
+```
+
+The diagram illustrates the relay node selection procedure for data traffic from one source to multiple destinations. The participants involved are the Source User Equipment (EF), the Service Control Function (SCF), the Relay Location Function (RLF), and two Relay Functions (RF1 and RF2). The procedure follows these steps:
+
+- EF sends a "Service request" to SCF.
+- SCF sends a "Relay node request" to RLF.
+- RLF performs "Relay node selection" internally.
+- RLF sends a "Resource reservation request" to both RF1 and RF2.
+- RF1 and RF2 send "Record the relationship" responses to RLF.
+- RF1 and RF2 send "Resource reservation response" messages to RLF.
+- RLF sends the "Selected relay node(s)" information to SCF.
+- SCF sends the "Selected relay node(s)" information back to EF.
+- EF sends "Data traffic" to both RF1 and RF2.
+- RF1 and RF2 forward the "Data traffic" to their respective destinations (multiple destinations for each RF).
+
+Sequence diagram illustrating the Relay Node (RN) selection procedure for data traffic from one source to multiple destinations. The diagram shows the interactions between the Source User Equipment (EF), the Service Control Function (SCF), the Relay Location Function (RLF), and two Relay Functions (RF1 and RF2).
+
+Y.2082(13)\_F8-4
+
+**Figure 8-4 – RN selection procedure for data traffic from one source to multi-destinations**
+
+1. EF sends the service request to SCF to request DSN services.
+2. SCF sends the RN request to RLF, which indicates the IP addresses of source node and destination node(s), service type, and QoS requirement.
+NOTE 1 – Based on user profile (e.g., whether the user has subscribed to the relay service), the requested service type, and the current access status of EF A or EF B, the SCF may determine that RN is needed.
+3. RLF selects the appropriate RN(s) that may provide relay services for several destination nodes. For example, RF1 is responsible for relaying packets from source node to some of the destination nodes, and RF2 is responsible for relaying packet from source node to the remainder of the destination nodes.
+NOTE 2 – RN selection may be based on TOCF optimization or RLF optimization, as described in clauses 8.1.2.1 and 8.1.2.2 separately.
+4. RLF sends resource reservation request to RT-FE of the selected RN(s).
+5. RT-FE(s) reserve resources (e.g., port, bandwidth) for this session, and records the mapping between the source node and its destination nodes.
+6. RT-FEs returns resource reservation response to RLF.
+7. RLF returns the information of selected RN(s) to SCF.
+8. SCF sends response to EF with RN(s) information.
+9. EF sends data packets to each RN.
+10. RN(s) send copies of received data packets to multiple destination nodes.
+
+### **8.1.3 Data plane connection procedures**
+
+Because an RN can be accessed by many consumers' UEs, it is necessary to design a mechanism to establish a secure relay path for each session. A relay session ID mechanism is used for this secure relay path establishment. Clauses 8.1.3.1, 8.1.3.2 and 8.1.3.3 provide an introduction of how this mechanism works. Clauses 8.1.3.4 and 8.1.3.5 particularly emphasize the multi-relay path set-up and update procedures.
+
+#### **8.1.3.1 Session set-up**
+
+Figure 8-5 illustrates the session set-up procedure for secure relay path establishment. The relay session ID is delivered to participants during session negotiation.
+
+
+
+```
+
+sequenceDiagram
+ participant EFA as EF A
+ participant SCF
+ participant RLF
+ participant RF as RF
+RT-FE
+ participant EFB as EF B
+
+ EFA->>SCF: 1. Service request
+ SCF->>RLF: 2. Relay node request
+ Note over RLF: 3. Relay node location and selection, creating relay session ID
+ RLF-->>RF: 4. Resource reservation request, with relay session ID
+ RF-->>RLF: 5. Resource reservation response
+ RLF->>SCF: 6. Selected relay node, with relay session ID
+ SCF->>EFB: 7. Service request, with relay session identifier and relay node information
+ EFB->>SCF: 8. Service response
+ SCF->>EFA: 9. Service response, with relay session ID and relay node information
+ EFA<--><-->EFB: 10. Data path setup
+
+```
+
+Y.2082(13)\_F8-5
+
+Sequence diagram showing the session set-up procedure for secure relay path establishment between EF A, SCF, RLF, RF (RT-FE), and EF B.
+
+**Figure 8-5 – Session set-up procedure for secure relay path establishment**
+
+1. EF A sends service request to SCF to request DSN services.
+2. SCF sends relay request to RLF to request relay services.
+NOTE – Based on user profile (e.g., whether the user has subscribed to the relay service), the requested service type, and current access status of EF A or EF B, the SCF may determine that RN is needed.
+3. Based on the EF addresses and the requested service, RLF locates and selects one or more suitable RNs for this request. At the same time, RLF generates a relay session ID for this session.
+4. RLF sends resource reservation request to RT-FE of RN to reserve relay resource. The relay session ID is included in the resource reservation request.
+5. RT-FE reserves necessary resources and returns the information about reserved resources in response message to RLF. RT-FE stores the received relay session ID for data path set-up.
+6. RLF returns the information of the selected RN(s) to SCF. The relay session ID is included in the response message.
+7. SCF forwards the service request to EF B, with the relay session ID received from RLF. SCF replaces EF A's data plane address with reserved resources in RN.
+8. EF B responds to the service request from SCF, by sending a service response message that includes its data plane information, i.e., IP address, port, codec, back to SCF.
+9. SCF transfers the service response message to EF A, with the relay session ID received from RLF. SCF replaces EF B's data plane address with reserved resources in RN.
+10. EF A and EF B begin to set up data path.
+
+### 8.1.3.2 Data path set-up for data traffic from one source to single destination
+
+Figure 8-6 illustrates the flows of data path set-up for data traffic from one source to single destination.
+
+
+
+```
+sequenceDiagram
+ participant EFA as EF A
+ participant RF as RF
+ participant RTFE as RT-FE
+ participant EFB as EF B
+
+ EFA->>RTFE: 1. First data packet, with relay session ID
+ RTFE->>RTFE: 2. Valid ID, binding with reserved resource
+ RTFE->>RTFE: 3. Cache data packet
+ EFB->>RTFE: 4. First data packet, with relay session ID
+ RTFE->>RTFE: 5. Valid ID, binding with reserved resource
+ EFA<->>SCF: 1. Service request
+ SCF->>RLF: 2. Relay node request
+ Note over RLF: 3. Relay node selection
+ RLF->>RF1: 4. Resource reservation
+ RLF->>RF2: 4. Resource reservation
+ RLF->>RF3: 4. Resource reservation
+ RLF->>SCF: 5. Selected relay nodes
+ SCF->>EFA: 6. Main data traffic
+ SCF->>RF1: 6. Main data traffic
+ SCF->>RF2: 6. Main data traffic
+ SCF->>RF3: 6. Main data traffic
+ SCF->>EFB: 6. Main data traffic
+ SCF->>EFA: 6. Backup data traffic
+ SCF->>RF1: 6. Backup data traffic
+ SCF->>RF2: 6. Backup data traffic
+ SCF->>RF3: 6. Backup data traffic
+ SCF->>EFA: 6. Backup data traffic
+ SCF->>EFB: 6. Backup data traffic
+ EFA->>SCF: 7. QoS measurement
+ EFA->>SCF: 8. Relay path update request
+ SCF->>RLF: 9. Relay path update request
+ RLF->>RF1: 9. Relay path update request
+ RLF->>RF2: 9. Relay path update request
+ RLF->>RF3: 9. Relay path update request
+ RLF->>SCF: 10. Response with new data plane information
+ SCF->>EFA: 11. Response with new relay node information
+ Note over EFA: 12. Use backup relay path
+ SCF->>EFA: 13. Main data traffic
+ SCF->>RF1: 13. Main data traffic
+ SCF->>RF2: 13. Main data traffic
+ SCF->>RF3: 13. Main data traffic
+ SCF->>EFB: 13. Main data traffic
+ SCF->>EFA: 13. Backup data traffic
+ SCF->>RF1: 13. Backup data traffic
+ SCF->>RF2: 13. Backup data traffic
+ SCF->>RF3: 13. Backup data traffic
+ SCF->>EFB: 13. Backup data traffic
+
+```
+
+Y.2082(13)\_F8-8
+
+Sequence diagram illustrating the multi relay path set-up and update procedure between EF A, SCF, RLF, and three relay nodes (RF1, RF2, RF3).
+
+**Figure 8-8 – Multi relay path set-up and update procedure**
+
+1. EF A sends service request to SCF to request DSN services.
+2. Based on the service profile or the location of EF A, SCF determines that multiple relay paths should be prepared for the requested service. Multiple relay paths may be used to achieve better QoS, or for regions with poor connections for example. SCF sends relay request to RLF to request for RNs.
+3. Depending on the EF addresses and the requested service, RLF locates and selects multiple suitable RNs for this request.
+4. Optionally, RLF reserves resources in the selected RNs.
+5. RLF returns the information of the selected RNs to SCF. SCF selects one RN to build the main relay path, and others to build backup path.
+6. Multiple relay paths are set up under the control of SCF. One is designated as the main path and the others are designated as backup paths to be used when a backup path is able to provide better QoS than the original main path.
+7. EF measures the QoS and will request for relay path change when the QoS drops below a given threshold for a given time.
+
+NOTE 1 – EF can be EF A or EF B. In this procedure, it is assumed that EF A initiates the request for relay path change.
+
+8. When QoS drops below threshold (i.e., becomes bad), EF A sends relay path update request to SCF. EF A inserts its new data plane information and the current QoS measurement results in the request message.
+9. SCF sends the relay path update request to EF B, with the new RN information.
+NOTE 2 – SCF determines whether the QoS can be improved by switching to a new relay path. SCF may require QoS information from RLF to determine whether any existing backup relay path can provide better QoS than the main path. For this step, it is assumed that the QoS can be improved by changing to a backup relay path.
+10. EF B responds to SCF with new data plane information.
+11. SCF sends a response to EF A with the new RN information.
+12. EF A begins using the backup relay path to transfer traffic, and stops sending data packet through the main path.
+13. The original backup traffic path now functions as the main relay path, and one of the other relay paths is selected as the new backup path.
+
+### 8.1.3.5 Multi relay path update failure
+
+Figure 8-9 shows the multi relay path update failure procedure.
+
+
+
+```
+
+sequenceDiagram
+ participant EFA as EF A
+ participant SCF as SCF
+ participant RLF as RLF
+ participant RF1 as RF1
+RT-FE
+ participant RF2 as RF2
+RT-FE
+ participant EFB as EF B
+
+ EFA-->>EFB: 1. Main data traffic
+ EFA-->>EFB: 1. Backup data traffic
+ EFA->>EFA: 2. QoS measurement
+ EFA->>SCF: 3. Relay path update request
+ SCF->>SCF: 4. Determine
+ SCF-->>EFA: 5. Relay path update denied
+
+```
+
+Sequence diagram illustrating the Multi relay path update failure procedure. The diagram shows the interaction between EF A, SCF, RLF, RF1 (RT-FE), RF2 (RT-FE), and EF B. 1. Main data traffic flows from EF A through SCF, RLF, and RF1 to EF B. 1. Backup data traffic flows from EF A through SCF, RLF, and RF2 to EF B. 2. QoS measurement is performed by EF A. 3. Relay path update request is sent from EF A to SCF. 4. Determine is performed by SCF. 5. Relay path update denied is sent from SCF to EF A.
+
+Y.2082(13)\_F8-9
+
+**Figure 8-9 – Multi relay path update failure procedure**
+
+1. Multiple relay paths are set up under the control of SCF. One is designated as the main path and the other is designated as backup path to be used if it is able to provide better QoS than the original main path.
+2. EF measures the QoS and will initiate a request for relay path change when the QoS drops below a given threshold for a given time.
+NOTE 1 – EF can be EF A or EF B. In this procedure, it is supposed that EF A initiates the request for relay path change.
+
+3. When QoS drops below threshold (i.e., becomes bad), EF A sends relay path update request to SCF. EF A inserts its new data plane information and the current QoS measurement results in the request message
+4. SCF determines that the QoS cannot be improved by switching to a new relay path.
+NOTE 2 – Although resource in the backup RN has been reserved, this does not ensure good QoS between UEs, as other parts of the path (e.g., wireless access) may cause QoS deterioration. SCF may require QoS information from RLF to determine that, because the QoS deterioration is caused by other parts of the path (e.g., wireless access), switching to a new relay is not helpful.
+5. SCF denies the relay path switch request.
+NOTE 3 – The data path is maintained until session termination. Other mechanisms for QoS enhancement are out of the scope of this Recommendation.
+
+## 8.1.4 Information update procedures
+
+### 8.1.4.1 Relay session information update
+
+Control nodes collect relay session information that may be used for billing or accounting. This relay session information includes the source/destination addresses, the RN ID, the amount of traffic relayed, and the duration of the relay session.
+
+Figure 8-10 shows the relay session information update procedure.
+
+
+
+```
+
+sequenceDiagram
+ participant EFA as EF A
+ participant RLF as RLF
+ participant RF as RF
+RT-FE
+ participant EFB as EF B
+
+ EFA <->> RF: 1. Data traffic
+ RF <->> EFB: 1. Data traffic
+ Note over RF: 2. Traffic measurement
+ RF -->> RLF: 3. Relay session information update
+ Note over RF: 4. Session finished
+ RF -->> RLF: 5. Relay session information update
+
+```
+
+Y.2082(13)\_F8-10
+
+Sequence diagram for Relay session information update. Entities: EF A, RLF, RF (containing RT-FE), and EF B. 1. Data traffic flows between EF A and EF B through RF. 2. Traffic measurement occurs at RT-FE. 3. Relay session information update is sent from RT-FE to RLF. 4. Session finished is detected at RT-FE. 5. Final Relay session information update is sent from RT-FE to RLF.
+
+**Figure 8-10 – Relay session information update**
+
+1. EF A and EF B are connected through the RN and send data packets to each other.
+2. RT-FE measures relayed traffic passing through the RN.
+3. During the session, RT-FE may send relay session information update message to RLF.
+4. RT-FE detects that the session has been terminated.
+NOTE – RT-FE determines session termination by notification from SCF, or by noting the time of data traffic interruption.
+5. RT-FE sends the relay session information update message summarizing the relay task for this session to RLF.
+
+## 8.2 Relay node management procedures
+
+### 8.2.1 Relay node registration
+
+RN registers itself to RLF with its own status information, including its capabilities, which is used by the RLF to help in RN selection. Figure 8-11 shows the RN registration procedure.
+
+
+
+```
+
+sequenceDiagram
+ participant RF as RF
+RT-FE
+ participant RLF1 as RLF
+ participant RLF2 as RLF
+
+ RF->>RLF1: 1. Registration request
+ Note over RLF1: 2. Relay node list update
+ RLF1-->>RF: 3. Registration response
+ RLF1->>RLF2: 4. Relay node information notification
+ RLF2-->>RLF1: 5. Relay node information notification response
+
+```
+
+Sequence diagram showing the RN registration procedure between an RF (containing RT-FE) and two RLFs. Step 1: RT-FE sends '1. Registration request' to the first RLF. Step 2: A box labeled '2. Relay node list update' is shown on the first RLF's lifeline. Step 3: The first RLF sends '3. Registration response' back to the RT-FE. Step 4: The first RLF sends '4. Relay node information notification' to the second RLF. Step 5: The second RLF sends '5. Relay node information notification response' back to the first RLF.
+
+Y.2082(13)\_F8-11
+
+**Figure 8-11 – RN registration procedure**
+
+1. RT-FE sends registration request to RLF, including the address of the RN and the capabilities of the RN.
+2. RLF updates the RN list information based on the registration request it received.
+3. RLF returns the registration response to RT-FE.
+4. RLF informs other RLFs of the newly joined RN by the RN information notification message.
+5. Other RLFs return a response to the RN information notification to RLF.
+
+NOTE – Step 4 and step 5 are optional according to different deployment scenarios. When there are multiple RLFs, the RLF that receives registration information can propagate the information to other RLFs.
+
+### 8.2.2 Relay node status information report
+
+Figure 8-12 shows the flows of reporting RN status to RLF. There are three types of reports. The first type is a periodic report, where the RT-FE is responsible for reporting RN status periodically to the RLF to which it registers. The second type is an on-demand report. RLF can request a registered RT-FE to report its node status on-demand. Upon receiving the request, RT-FE should report the requested information. The third type is an event-driven report. When predefined events have occurred, these events should be reported by RT-FE to RLF.
+
+
+
+```
+
+sequenceDiagram
+ participant RLF
+ participant RF
+ participant RTFE as RT-FE
+ Note over RF: RF
+ Note over RTFE: RT-FE
+
+ RLF->>RTFE: 1. Status report
+ RTFE-->>RLF: 2. Status report
+ Note over RLF,RTFE: Periodic report
+
+ RLF->>RTFE: 1. Status request
+ RTFE-->>RLF: 2. Status report
+ Note over RLF,RTFE: On-demand report
+
+ Note over RTFE: 1. Event occurs (e.g., load threshold reaches)
+ RTFE-->>RLF: 2. Status report
+ Note over RLF,RTFE: Event-driven report
+
+```
+
+Y.2082(13)\_F8-12
+
+Sequence diagram showing Relay node status information report procedure between RLF and RT-FE (part of RF).
+
+**Figure 8-12 – Relay node status information report procedure**
+
+Periodic report:
+
+1. RT-FE sends the status report to RLF.
+2. After a predefined interval, RT-FE sends the status information again to RLF.
+
+On-demand report:
+
+1. RLF requests status information of RN.
+2. Upon receiving the report request from RLF, RT-FE responds with the requested information.
+
+Event-driven report:
+
+1. A predefined event to be reported to RLF has occurred.
+2. Upon recognizing the event, RT-FE should report the event to RLF.
+
+### 8.3 QoS measurement procedures
+
+Before or during the RN selection procedure, RLF may need to gather the QoS measurement of the relay path. The QoS measurement of a relay path includes: the RTT of the path, the one-way delay of the path, the available bandwidth of the path, the delay jitter of the path, and the packet loss rate of the path. TQM-FE may set up a new connection for measurement when necessary.
+
+Figure 8-13 shows the procedure of QoS measurement of the relay path.
+
+
+
+```
+
+sequenceDiagram
+ participant TQM-FE A
+ participant RLF
+ participant TQM-FE B
+
+ RLF->>TQM-FE A: 1. Measurement request
+ RLF->>TQM-FE B: 2. Measurement request
+ TQM-FE A <--> TQM-FE B: 3. Data plane connection
+ TQM-FE A->>RLF: 4. Measurement result
+ TQM-FE B->>RLF: 5. Measurement result
+ RLF->>[6. Measurement result recording]
+
+```
+
+Y.2082(13)\_F8-13
+
+Sequence diagram showing QoS measurement of the relay path between TQM-FE A, RLF, and TQM-FE B.
+
+**Figure 8-13 – QoS measurement of the relay path**
+
+1. RLF sends measurement request to TQM-FE A to request measurements. The request includes: the address of TQM-FE B, connection parameters (e.g., connection types, passwords), the type of requested QoS information, the desired measurement methods, and the requested measurement times, duration and frequency, etc.
+NOTE 1 – TQM-FE may be in RN or in UE. The UE that is capable of using relay services may include TQM-FE (in itself) to support QoS measurements.
+2. Optionally, RLF may also send a measurement request to TQM-FE B.
+NOTE 2 – When the requested measurement is simple and consumes few resources (e.g., ping-like measurements), end-terminal B may always be ready for other nodes to connect for such simple operations. In this case, RLF does not need to notify TQM-FE B.
+3. Based on the information in measurement request, TQM-FE A sets up a data plane connection to TQM-FE B when there is no existing connection. These two TQM-FEs exchange data packets based on the instructions in measurement request in order to gather the requested QoS measurements.
+4. TQM-FE A returns measurement results to RLF. The measurement results include the gathered QoS information, timestamp, whether the measurement is successful, etc.
+5. Optionally, TQM-FE B can also return measurement results to RLF.
+6. RLF records the QoS information.
+
+## 9 Reference points
+
+RT-FE interacts with RLF via the reference point C4 to register itself, perform node status reports, and accept resource reservation requests.
+
+TQM-FE interacts with RLF via the reference point C4 to accept measurement tasks and report measurement results.
+
+### 9.1 Reference point C4
+
+Reference point C4 is the control interface between RLF and RT-FE/TQM-FE.
+
+#### 9.1.1 Registration
+
+Table 9-1 lists the parameters included in the registration request sent from RT-FE to RLF to register itself to RLF.
+
+**Table 9-1 – Parameters used for registration request**
+
+| Parameters | Parameter description |
+|---------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Node ID | The identifier of the RN. |
+| Certification | The certification used to authenticate the RN. Detailed format of this certification depends on implementation. |
+| Capability | The capability of the RN.
Attributes:
- – System: CPU (central processor unit), MEM (memory) size, bandwidth, IP address.
- – NAT/firewall traversal: whether the RN supports NAT/firewall traversal, protocols.
- – One to More: whether the RN supports relaying the data traffic from one source to multi-destinations.
- – Measurement capability: the capability of QoS measurement.
|
+| Address List | Address List is used to list the addresses of the RN.
Attributes:
- – Count: The number of addresses in the list.
The Address List includes one or more items of Address, which is the address of the RN.
Address:
- – Type: address type, can be public, local, etc.
- – IP Address.
|
+
+Table 9-2 lists the parameters included in the registration response sent from RLF to RT-FE to respond to the registration request.
+
+**Table 9-2 – Parameters used for registration response**
+
+| Parameters | Parameter description |
+|----------------------|---------------------------------------------------------------------------------------------|
+| Registration Status | The status acknowledge of the registration:
Value: OK/Not Acceptable. |
+| Status Report Period | Status report period. The value is set to 0 to indicate no need for periodic status report. |
+
+### 9.1.2 Status report
+
+Table 9-3 lists the parameters included in the status report request sent from RLF to RT-FE to inform the RN to report its status.
+
+**Table 9-3 – Parameters used for status report request**
+
+| Parameters | Parameter description |
+|----------------------|---------------------------------------------------------------------------------------------|
+| Node ID | The identifier of the RN. |
+| Status Report Period | Status report period. The value is set to 0 to indicate no need for periodic status report. |
+
+Table 9-4 lists the parameters included in the status report sent from RT-FE to RLF to report the node status.
+
+**Table 9-4 – Parameters used for status report**
+
+| Parameters | Parameter description |
+|-------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Node ID | The identifier of the RN. |
+| Uptime | The time since the RN has booted. |
+| Task Count | The number of relay tasks completed by the RN. |
+| Task List | Task List is used to list the tasks that the RN is currently working on.
Attributes:
- – Count: The number of tasks in the list
The Task List includes one or more items of Task, which is the task that the RN is currently working on, including relay tasks and measurement tasks.
Task:
- – Task ID: The task identifier assigned by RLF or by the RN itself.
|
+| Address List | Address List is used to list the addresses of the RN.
Attributes:
- – Count: The number of addresses in the list.
The Address List includes one or more items of Address, which is the address of the RN.
Address:
- – Type: address type, can be public, local, etc.
- – IP Address.
|
+| Resource State | The status of the resource usage of the RN.
Attributes:
- – Bandwidth: the free bandwidth of the RN.
- – CPU: the CPU load of the RN.
- – Memory: the free memory that can be used by the relay task.
- – Free Ports: the number of free ports that can be used for Relay.
|
+
+### 9.1.3 Resource reservation
+
+Table 9-5 lists the parameters included in the resource reservation request sent from RLF to RT-FE to reserve resources for relay tasks to RT-FE.
+
+**Table 9-5 – Parameters used for resource reservation request**
+
+| Parameters | Parameter description |
+|---------------------|------------------------------------------------------------------------------------------------------|
+| Task ID | The task identifier assigned by RLF. |
+| Node ID | The identifier of the RN to which the task is assigned. |
+| Task type | The type of the task, e.g., one source to single destination, one source to multi-destinations, etc. |
+| Security credential | Security information related to the relay task, e.g., the hash of the password or the public key. |
+
+**Table 9-5 – Parameters used for resource reservation request**
+
+| Parameters | Parameter description |
+|------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Source List | Source List is used to list the sources for this relay task.
Attributes:
- – Count: The number of sources in the list.
The Source List includes one or more items of Source, which are the source nodes of the relay task.
Source:
- – Source ID: Source identity.
- – IP Address: Source IP address and port.
- – QoS: the QoS for the relay task, e.g., bandwidth.
- – Connection Type: the connection type for the relay task, e.g., TCP/UDP, active/passive.
- – Security Credential: Security information related to the source node, e.g., the hash of the password or the public key.
|
+| Destination List | Destination List is used to list the destinations for this relay task.
Attributes:
- – Count: The number of destinations in the list
The Destination List includes one or more items of Destination, which is the relay destination of the relay task.
Destination:
- – Destination ID: Destination identity.
- – IP Address: Destination IP address and port.
- – QoS: the QoS for the relay task, e.g., bandwidth.
- – Connection Type: the connection type for the relay task, e.g., TCP/UDP, active/passive.
- – Security Credential: Security information related to the destination node, e.g., the hash of the password or the public key.
|
+
+Table 9-6 lists the parameters included in the resource reservation response sent from RT-FE to RLF.
+
+**Table 9-6 – Parameters used for resource reservation response**
+
+| Parameters | Parameter description |
+|---------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Task Status | The status acknowledge of the task:
Value: OK/Not Acceptable.
|
+| Resource List | Resource List is used to list the resource reserved for this relay task.
Attributes:
- – Count: The number of resources in the list.
The Resource List includes one or more items of Relay Resource, which is the resource reserved by the RN.
Relay Resource:
- – IP address: Reserved IP address and port for the source or destination.
- – Node ID: the ID of source or destination node related to the Resource.
|
+
+#### 9.1.4 Measurement
+
+Table 9-7 lists the parameters included in the measurement request sent from RLF to TQM-FE to assign measurement tasks to TQM-FE.
+
+**Table 9-7 – Parameters used for measurement request**
+
+| Parameters | Parameter description |
+|------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Task ID | The task identifier assigned by RLF. This identifier is returned in the measurement result feedback. |
+| Node ID | The identifier of the RN to which the task is assigned. |
+| Repeat | Flag indicating whether the task is periodical or not.
Value: TRUE/FALSE. |
+| Period | The period of the task in units of milliseconds (ms). TQM-FE should execute the task once for each period. For non-periodic tasks, the default value is set to 0. |
+| Task List | Task List is the list of measurement tasks assigned to TQM-FE at the same time.
Attributes:
– Count: The number of subtasks in the list.
The Task List includes one or more items of Destination, which is the measurement destination of a single task.
Destination:
– Destination ID: Destination identity.
– IP Address: Destination IP address and port.
– Connection Type: the connection type for the relay task, e.g., TCP/UDP, active/passive.
– Security Credential: Security information related to the destination node, e.g., the hash of the password or the public key.
– Parameters: the parameters to be measured, e.g., RTT, throughput, loss, jitter. |
+
+Table 9-8 lists the parameters included in the measurement response sent from TQM-FE to RLF.
+
+**Table 9-8 – Parameters used for measurement response**
+
+| Parameters | Parameter description |
+|-------------|-------------------------------------------------------------------|
+| Task Status | The status acknowledge of the task:
Value: OK/ Not Acceptable. |
+
+Table 9-9 lists the parameters included in the measurement result report sent from TQM-FE to RLF to report measurement results to RLF.
+
+**Table 9-9 – Parameters used for measurement result report**
+
+| Parameters | Parameter description |
+|------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Node ID | The identifier of the RN. |
+| Task ID | The task identifier assigned by RLF. |
+| Address | The address of the RN used for the measurement.
Attributes:
– Type: address type, can be public, local, etc.
– IP Address: the address and port. |
+
+**Table 9-9 – Parameters used for measurement result report**
+
+| Parameters | Parameter description |
+|-------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Result List | Result List is used to report multiple results to the RLF at the same time.
Attributes: - – Count: The number of measurement results in the list.
The Result List includes one or more items of measurement result.
Result: - – Destination identity.
- – IP Address: Destination IP address and port.
- – State: the state of the measurement, connection success or cannot connect to the destination.
- – RTT: the RTT of the link.
- – Throughput: the throughput of the link.
- – Loss: packet loss rate of the link.
- – Jitter: The averages of the deviation from packet mean latency.
- – Timestamp: the time that the measurement is taken.
|
+
+The report does not need response.
+
+#### **9.1.5 Relay session information report**
+
+Table 9-10 lists the parameters included in the relay session information report sent from RT-FE to RLF to report relay session information to RLF.
+
+**Table 9-10 – Parameters used for relay session information report**
+
+| Parameters | Parameter description |
+|-------------|------------------------------------------------------------------------------------------------------|
+| Node ID | The identifier of the RN. |
+| Task ID | The task identifier assigned by RLF. |
+| Task Result | The status of task.
Value: Success/Timeout. |
+| Task Type | The type of the task, e.g., one source to single destination, one source to multi-destinations, etc. |
+| Duration | The duration of the task. |
+| Throughput | Total amount of traffic that the RN has relayed. |
+| Timestamp | The time of the relay session information. |
+
+This report does not need response.
+
+Security mechanisms (e.g., source authentication, integrity protection), should be included when sending this report.
+
+## Appendix I
+
+### Relay algorithms introduction
+
+(This appendix does not form an integral part of this Recommendation.)
+
+Relay algorithms have been studied for several years, and attracted more attention in academic and industry fields. According to different deployment scenarios, different algorithms should be taken into consideration. As an example, one relay algorithm is introduced below in brief.
+
+#### I.1 Description of GNG algorithms
+
+As shown in Figure I.1, a grade-based neighbour group (GNG) relay node selection algorithm is proposed to aim at quality improvement and network address translation (NAT) traversal with low overhead. According to the node location, all neighbouring nodes form a group based on the GNG. Therefore, many groups can be established, and each group will select one or more surrogate nodes to deal with QoS measurement. The surrogate for each group will maintain some of its neighbouring groups' information, and measure the round-trip time (RTT).
+
+
+
+Y.2082(13)\_Fl.1
+
+| | | | |
+|-------------------|---------------|------------------------|----------------------------|
+| ● Client node | ○ Ring member | ⊘ Candidate relay node | → Message of query |
+| ● Group surrogate | ● RN-S node | ⊗ Selected relay node | → Message of relay request |
+
+Diagram illustrating the GNG relay node selection algorithm. It shows two overlapping groups, Group A and Group B, each containing client nodes and ring members. Group A has a surrogate node (purple dot) and Group B has a surrogate node (purple dot). A Relay Node Server (RN-S, blue circle) is shown at the top. Arrows indicate messages of query and relay request between the RN-S and the surrogate nodes. A legend below the diagram defines the symbols: Client node (black dot), Ring member (white circle), Candidate relay node (hatched circle), Selected relay node (diagonal lines circle), Group surrogate (purple dot), RN-S node (blue circle), Message of query (solid arrow), and Message of relay request (dashed arrow).
+
+Figure I.1 – GNG relay node selection algorithm
+
+##### I.1.1 GNG system structures and node operations
+
+The following three types of nodes are defined in GNG protocol.
+
+###### 1) Relay node server (RN-S)
+
+RN-S, which can be implemented as RC-FE in the RF framework, is normally a powerful, dedicated, and always-on server used for processing relay nodes' joining requests, maintaining all surrogate information, making relay node selections, etc.
+
+RN-S plays critical roles and stores important information in GNG algorithm. RN-S provides the following functions and services to make the entire system strong and intelligent:
+
+- Collect the autonomous system (AS) information and build an up-to-date AS graph.
+- Accept all relay nodes' registration; registration information includes state information, bandwidth, continuous online time, node processing power and other related information.
+- Collect the surrogates' measurement results, such as round-trip time between different groups.
+
+- Execute relay node selection algorithm, request the related relay resource, such as the port number of data transport.
+- Select new surrogates for group upon surrogate failures.
+- Assign the measurement tasks to the surrogates.
+
+## 2) Group surrogates
+
+Group surrogate nodes are powerful and stable with high bandwidth network connections within a group. There can be one or more surrogates within one group.
+
+Group surrogates volunteer themselves to provide the following services:
+
+- Periodically measure the QoS between closed groups, including RTT, bandwidth, etc.
+- Report the measurement results to the RN-S.
+
+## 3) Relay node
+
+Relay nodes can be end hosts or servers deployed by operators, and are responsible for relaying traffic packets.
+
+In GNG, relay nodes have the following duties:
+
+- Become surrogates in their groups, if they are the only nodes in their groups.
+- Periodically publish their nodes' information to RN-S.
+- Registration to the RN-S to become a relay node.
+- Relay media packets.
+
+### I.1.2 Relay nodes selection procedure
+
+The general procedure of relay node selection in GNG is introduced here. As shown in Figure I.2, when the QoS cannot satisfy the needs of UEs, or UEs are behind NAT, they will request for relay node support to improve the QoS or provide NAT traversal. Relay request will be sent to RN-S. The specific GNG relay process is shown in Figure I.2 below, and includes the following steps.
+
+Step 1: RN-S receives relay request between UE1 and UE2.
+
+Step 2: RN-S queries the groups of UE1 and UE2, $UE1 \in GroupID\ 1, UE2 \in GroupID\ 2$ , looks up each group's surrogate, and initiates the relay assemblage $R = \{\Phi\}$ .
+
+Step 3: If Group1 ID does not equal Group2 ID, then RN-S chooses relay nodes in the group neighbouring relay list.
+
+Step 4: Based on collected information of relay overlay, such as: traffic load conditions and reliabilities of the nearby relay nodes, as well as RTTs and packet loss rates of the relay paths corresponding to these nearby relay nodes, RN-S picks the most suitable relay nodes for UEs.
+
+
+
+```
+
+graph TD
+ Start[Receive relay request between UE1
+and UE2;] --> Query[Query the groups of UE1 and UE2,
+lookup each group's surrogate, initiate
+the relay assemblage $R=\{\Phi\}$ ]
+ Query --> Decision{GroupID 1 = GroupID 2
+Yes or No?}
+ Decision -- No --> GetCS[Get the common relay set of group
+neighbouring relay list, abbreviated to CS]
+ GetCS --> Loop[Each $G \in CS$ , each $r \in G$ .
+If $RTT(S1-r-S2) < lat T$ , add r to R]
+ Decision -- Yes --> Deny[Deny relay request]
+ Loop --> Return([Return R])
+ Deny --> Return
+
+```
+
+Y.2082(13)\_FI.2
+
+Flowchart of the GNG relay procedure. The process begins with receiving a relay request between UE1 and UE2. It then queries their groups, looks up surrogates, and initializes the relay assemblage R as an empty set. A decision diamond asks if GroupID 1 equals GroupID 2. If 'Yes', the request is denied and the process proceeds to return R. If 'No', it retrieves a common relay set (CS) from neighboring relay lists. For each group G in CS and each relay r in G, if the round-trip time RTT(S1-r-S2) is less than a latency threshold T, the relay r is added to R. Finally, the set R is returned.
+
+**Figure I.2 – GNG relay procedure**
+
+## Bibliography
+
+- [b-ITU-T Y.2012] Recommendation ITU-T Y.2012 (2010), *Functional requirements and architecture of next generation networks*.
+- [b-ITU-T Y.2081] Recommendation ITU-T Y.2081 (2012), *Distributed service networking traffic optimization control functions*.
+- [b-ITU-T Y.2206] Recommendation ITU-T Y.2206 (2010), *Requirements for distributed service networking capabilities*.
+- [b-ITU-T Y.2111] Recommendation ITU-T.2111 (2011), *Resource and admission control functions in next generation networks*.
+- [b-ITU-T Y.2000-series Sup.10] Recommendation ITU-T Y.2000-series – Supplement 10 (2010), *Supplement on distributed service network (DSN) use cases*.
+
+
+
+
+
+## SERIES OF ITU-T RECOMMENDATIONS
+
+| | |
+|-----------------|--------------------------------------------------------------------------------------------------|
+| Series A | Organization of the work of ITU-T |
+| 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 | 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 |
\ No newline at end of file
diff --git a/marked/Y/T-REC-Y.2212-200802-I_PDF-E/raw.md b/marked/Y/T-REC-Y.2212-200802-I_PDF-E/raw.md
new file mode 100644
index 0000000000000000000000000000000000000000..2e3750061a636d1770a7e662ae2a1f335da44cba
--- /dev/null
+++ b/marked/Y/T-REC-Y.2212-200802-I_PDF-E/raw.md
@@ -0,0 +1,1000 @@
+
+
+I n t e r n a t i o n a l T e l e c o m m u n i c a t i o n U n i o n
+
+**ITU-T**
+
+TELECOMMUNICATION
+STANDARDIZATION SECTOR
+OF ITU
+
+**Y.2212**
+
+(02/2008)
+
+SERIES Y: GLOBAL INFORMATION
+INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS
+AND NEXT-GENERATION NETWORKS
+
+Next Generation Networks – Service aspects: Service
+capabilities and service architecture
+
+# --- **Requirements of managed delivery services**
+
+Recommendation ITU-T Y.2212
+
+## ITU-T Y-SERIES RECOMMENDATIONS **GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS AND NEXT- GENERATION NETWORKS**
+
+## GLOBAL INFORMATION INFRASTRUCTURE
+
+| | |
+|-------------------------------------------|-------------|
+| General | Y.100–Y.199 |
+| Services, applications and middleware | Y.200–Y.299 |
+| Network aspects | Y.300–Y.399 |
+| Interfaces and protocols | Y.400–Y.499 |
+| Numbering, addressing and naming | Y.500–Y.599 |
+| Operation, administration and maintenance | Y.600–Y.699 |
+| Security | Y.700–Y.799 |
+| Performances | Y.800–Y.899 |
+
+## INTERNET PROTOCOL ASPECTS
+
+| | |
+|--------------------------------------------------------------------|---------------|
+| General | Y.1000–Y.1099 |
+| Services and applications | Y.1100–Y.1199 |
+| Architecture, access, network capabilities and resource management | Y.1200–Y.1299 |
+| Transport | Y.1300–Y.1399 |
+| Interworking | Y.1400–Y.1499 |
+| Quality of service and network performance | Y.1500–Y.1599 |
+| Signalling | Y.1600–Y.1699 |
+| Operation, administration and maintenance | Y.1700–Y.1799 |
+| Charging | Y.1800–Y.1899 |
+
+## NEXT GENERATION NETWORKS
+
+| | |
+|-----------------------------------------------------------------------|----------------------|
+| Frameworks and functional architecture models | Y.2000–Y.2099 |
+| Quality of Service and performance | Y.2100–Y.2199 |
+| Service aspects: Service capabilities and service architecture | Y.2200–Y.2249 |
+| Service aspects: Interoperability of services and networks in NGN | Y.2250–Y.2299 |
+| Numbering, naming and addressing | Y.2300–Y.2399 |
+| Network management | Y.2400–Y.2499 |
+| Network control architectures and protocols | Y.2500–Y.2599 |
+| Security | Y.2700–Y.2799 |
+| Generalized mobility | Y.2800–Y.2899 |
+
+*For further details, please refer to the list of ITU-T Recommendations.*
+
+# **Recommendation ITU-T Y.2212**
+
+# **Requirements of managed delivery services**
+
+## **Summary**
+
+Recommendation ITU-T Y.2212 provides the service and functional requirements of managed delivery services (MDS).
+
+## **Source**
+
+Recommendation ITU-T Y.2212 was approved on 29 February 2008 by ITU-T Study Group 13 (2005-2008) under Recommendation ITU-T A.8 procedure.
+
+## **Keywords**
+
+Always on service (AoS), managed delivery services (MDS), MDS control, MDS functional architecture model, MDS service classification, MDS service partnership, MDS service profile, MDS service scenario, non-subscription based MDS, on-demand service (ODS), subscription-based MDS.
+
+## 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 .
+
+© ITU 2009
+
+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 |
+| | 3.1 Terms defined elsewhere..... | 1 |
+| | 3.2 Terms defined in this Recommendation..... | 2 |
+| 4 | Abbreviations and acronyms ..... | 2 |
+| 5 | Conventions ..... | 3 |
+| 6 | MDS overview..... | 3 |
+| | 6.1 MDS business model..... | 3 |
+| | 6.2 MDS service provisioning..... | 4 |
+| 7 | Service requirements of MDS ..... | 5 |
+| | 7.1 Requirements for MDS service classification ..... | 6 |
+| | 7.2 Requirements for MDS service partnership ..... | 6 |
+| | 7.3 Requirements for the use of profiles for MDS ..... | 6 |
+| | 7.4 MDS control requirements ..... | 7 |
+| | 7.5 Authentication and authorization requirements..... | 7 |
+| 8 | Profiles for MDS management ..... | 7 |
+| | 8.1 General requirements of MDS related profiles ..... | 7 |
+| | 8.2 MDS service profile ..... | 8 |
+| | 8.3 Third-party provider profile ..... | 9 |
+| | 8.4 User profile..... | 9 |
+| | 8.5 MDS control profile ..... | 10 |
+| 9 | Functional architecture ..... | 12 |
+| | 9.1 Functional architecture model ..... | 12 |
+| | 9.2 MDS functional elements ..... | 16 |
+| 10 | MDS service scenarios ..... | 17 |
+| | 10.1 Subscription-based MDS service scenario ..... | 17 |
+| | 10.2 Non-subscription based MDS service scenario..... | 24 |
+| 11 | Security considerations..... | 26 |
+
+## **Introduction**
+
+One of the advantages of the ITU-T NGN is the openness formed by the whole of the ITU-T NGN architecture (Recommendation ITU-T Y.2001). The NGN's concept, principles and functional architectural model provides a great opportunity to initiate a more detailed development of various interfaces such as UNI, NNI, ANI, etc.
+
+NGN should have efficient and flexible capabilities to enable third-party providers and users to use NGN capabilities through the interfaces.
+
+This Recommendation describes "managed delivery services" as the services that use ANI to enable the provision of managed delivery services between third-party providers and users.
+
+# Recommendation ITU-T Y.2212
+
+# Requirements of managed delivery services
+
+# 1 Scope
+
+The objective of this Recommendation is to describe the service and functional requirements of the managed delivery services (MDS) provided by an NGN provider to third-party providers via ANI (application network interface), with features supported by the next generation network (NGN) [ITU-T Y.2001], [ITU-T Y.2011], [ITU-T Y.2012], and [ITU-T Y.2201].
+
+The service and functional requirements described in this Recommendation are built on the NGN general reference model [ITU-T Y.2011] and generalized functional architecture [ITU-T Y.2012]. This Recommendation describes the service concept of MDS, the business model among players relevant to MDS, the service requirements of MDS, profiles for MDS management, the functional architecture model, MDS service scenarios, and security considerations for MDS.
+
+This Recommendation describes several service scenarios to show how MDSs are operated. These service scenarios are described from a service procedural point of view, as well as in terms of the functional entities involved.
+
+# 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 Y.2001] | Recommendation ITU-T Y.2001 (2004), General overview of NGN . |
+| [ITU-T Y.2011] | Recommendation ITU-T Y.2011 (2004), General principles and general reference model for next generation networks . |
+| [ITU-T Y.2012] | Recommendation ITU-T Y.2012 (2006), Functional requirements and architecture of the NGN release 1 . |
+| [ITU-T Y.2111] | Recommendation ITU-T Y.2111 (2006), Resource and admission control functions in next generation networks . |
+| [ITU-T Y.2201] | Recommendation ITU-T Y.2201 (2007), NGN release 1 requirements . |
+| [ITU-T Y.2701] | Recommendation ITU-T Y.2701 (2007), Security requirements for NGN release 1 . |
+
+# 3 Definitions
+
+## 3.1 Terms defined elsewhere
+
+This Recommendation uses the following terms defined elsewhere:
+
+**3.1.1 application network interface (ANI)** [ITU-T Y.2012]: Interface which provides a channel for interactions and exchanges between applications and NGN elements. The ANI offers capabilities and resources needed for the realization of applications.
+
+## 3.2 Terms defined in this Recommendation
+
+This Recommendation defines the following terms:
+
+**3.2.1 managed delivery services (MDS):** The services provided by an NGN provider to third-party providers with features supported by the NGN, in which comprehensive control capabilities for service delivery are available between third-party providers and their users.
+
+**3.2.2 MDS control profile:** The set of information regarding service control, session control, resource control and transport control to support MDS.
+
+**3.2.3 MDS service profile:** The sets of MDS service information to provide comprehensive control capabilities for service delivery between third-party providers and their users.
+
+**3.2.4 user:** The user of the services of a third-party provider whose services are provided with managed delivery features facilitated through MDS.
+
+# 4 Abbreviations and acronyms
+
+This Recommendation uses the following abbreviations and acronyms:
+
+| | |
+|----------|-------------------------------------------------------------|
+| AC | Admission Control |
+| AMG-FE | Access Media Gateway Functional Entity |
+| ANI | Application Network Interface |
+| AoS | Always on Service |
+| ASF&SSF | Application Support Functions and Service Support Functions |
+| BE | Best Effort |
+| BiC | Bandwidth Instantiation Control |
+| BoD | Bandwidth-on-Demand |
+| BW | Bandwidth |
+| CoS | Class of Services |
+| CPE | Customer Premises Equipment |
+| CPE-BE | Customer Premises Equipment Border Element |
+| FE | Functional Entity |
+| IBC-FE | Interconnection Border Gateway Control Functional Entity |
+| IBG-FE | Interconnection Border Gateway Functional Entity |
+| I-CSC-FE | Interrogating Call Session Control Functional Entity |
+| MDS | Managed Delivery Services |
+| MGC-FE | Media Gateway Control Functional Entity |
+| MRB-FE | Media Resource Broker Functional Entity |
+| MRC-FE | Media Resource Control Functional Entity |
+| NACF | Network Attachment Control Function |
+| NAPT | Network Address and Port Translation |
+| NGN | Next Generation Network |
+| ODS | On-Demand Service |
+
+| | |
+|----------|------------------------------------------------|
+| P-CSC-FE | Proxy Call Session Control Functional Entity |
+| PSS | Pre-Scheduled Service |
+| RACF | Resource and Admission Control Function |
+| SCF | Service Control Function |
+| S-CSC-FE | Serving Call Session Control Functional Entity |
+| SeC | Security Control |
+| TCF | Transport Control Function |
+| UNI | User Network Interface |
+| VoD | Video-on-Demand |
+
+# 5 Conventions
+
+This Recommendation uses the following conventions, the same as those used in [ITU-T Y.2012], to denote functional entities.
+
+**A-n:** This term is used to indicate the functional entity in application support functions.
+
+**S-n:** This term is used to indicate the functional entity in service support functions.
+
+**T-n:** This term is used to indicate the functional entity in transport and transport control functions.
+
+# 6 MDS overview
+
+This clause describes the business model and service provisioning types of MDS.
+
+## 6.1 MDS business model
+
+It is recognized that MDS focus on the online business area, particularly on markets and businesses where the broadband real-time interaction is involved, and where an added value is required via customization.
+
+It is required that MDS make use of NGN capabilities to differentiate the service levels experienced by users, such as quality of service, security level, etc.
+
+Figure 6-1 explains the key aspects of the MDS business model. Users invoke services to satisfy their own special requirements by requesting certain managed capabilities, such as bandwidth allocation and routing, depending on their service needs. A third-party provider will be able to provide more service capabilities by partnering with NGN providers, without any further infrastructural investments between a user and a third-party provider, or between users of the third-party providers. Due to these additional capabilities, a third-party provider will provide a better and broader range of services through the selection of appropriate parameters. Users of a third-party provider will use their services in various ways, depending on their needs. NGN providers will be able to extend their business coverage jointly with third-party providers, in order to extend their users directly or indirectly, and to develop a value-added infrastructure.
+
+
+
+Figure 6-1: Example of MDS business model. The diagram shows two models: the 'Current business model' and the 'MDS business model'. In the current model, a User (blue circle) provides 'Service charge' to a 3rd party provider (yellow circle) and receives 'Service' in return. The User also provides 'Network capability' to an NGN provider (blue circle) and receives 'Connection fee' in return. A large blue arrow points to the MDS business model. In the MDS model, the User provides 'Service charge+' to the 3rd party provider and receives 'Service+' in return. The User also provides 'Network capability+' to the NGN provider and receives 'Connection fee' in return. Additionally, the 3rd party provider provides 'QoS, routing, others' to the NGN provider, and the NGN provider provides 'Cost' to the 3rd party provider. The text '' is below the first diagram, and '' is below the second. The reference 'Y.2212(08)F6-1' is at the bottom right.
+
+**Figure 6-1 – Example of MDS business model**
+
+## 6.2 MDS service provisioning
+
+There are three different general categories of MDS service provisioning: subscription related viewpoint, service request related viewpoint, and participation into MDS control process related viewpoint.
+
+### 1) Service provisioning from a subscription related viewpoint
+
+Two types of MDS service provisioning can be distinguished, depending on whether or not a prior subscription exists between a third-party provider and a user.
+
+- Subscription-based MDS: This requires a subscription between a third-party provider and a user prior to using MDS. This type is generally useful for services having a regular or specific usage pattern. In general, MDS control policy applies to the network when the user connects to the network. Virtual private leased line services and network-controlled e-learning services would be examples of subscription-based MDS.
+- Non-subscription-based MDS: This requires no subscription between a third-party provider and a user prior to using MDS. This type is generally useful for services having an irregular or single usage pattern. MDS control policy applies to the network when the user requests an MDS on demand. VoD services, video phone services and networked storage services with BoD would be examples of non-subscription-based MDS.
+
+### 2) Service provisioning from a service request related viewpoint
+
+Three types of MDS service provisioning can be distinguished, depending on whether MDS is provided when a user is always connected to the network, or a user requests a service in pre-scheduled or on-demand manner.
+
+- Always on service (AoS): In this service type, MDS is provided when a user connects to the network, without any concern about whether MDS related traffic is generated or not. MDS is cancelled when a user disconnects from the network.
+- Pre-scheduled service (PSS): In this service type, MDS is provided when a user connects to the network, in a pre-scheduled manner that is agreed between a third-party provider and a user.
+- On-demand service (ODS): In this service type, MDS is provided when a user requests a service using MDS on demand. When a user requests the corresponding service to end, MDS is cancelled.
+
+### 3) Service provisioning from a control process participation related viewpoint
+
+Two types of MDS service provisioning can be distinguished, depending on whether a third-party provider takes part in the MDS control process or not.
+
+- MDS control process participation: In this type, a third-party provider participates in the MDS control process by agreement with an NGN provider. In the case of ODS service type, MDS control process participation is required, and the third-party provider requests MDS control to the NGN provider. In the case of AoS/PSS service types, the third-party provider is informed by the NGN provider regarding the user's network access, and then can optionally request MDS control to the NGN provider.
+- No MDS control process participation: In the case of AoS/PSS service types, when a user connects to the network, an NGN provider provides MDS control on its own, without the participation of the 3rd party provider.
+
+Subscription-based MDS with a regular usage pattern is provisioned as either AoS, PSS or ODS type, according to the user profile given to the 3rd party provider during the subscription process. Non-subscription based MDS with an irregular usage pattern is provisioned as ODS type.
+
+Figure 6-2 shows the relationship between MDS service provisioning types.
+
+
+
+Figure 6-2 illustrates the relationship between MDS service provisioning types across three viewpoints:
+
+- Service provisioning from subscription related viewpoint:**
+ - I. Subscription-based MDS:**
+ - Need prior MDS subscription process of a user
+ - MDS control policy applies to network when a user connects to network
+ - II. Non-subscription based MDS:**
+ - No need prior MDS subscription process of a user
+ - MDS control policy applies to network when a user requests an MDS service on demand
+- Service provisioning from service request related viewpoint:**
+ - I. Always on Service (AoS):**
+ - MDS provided when a user connects to network
+ - MDS provided without concern about whether the MDS related traffic is generated or not
+ - MDS cancelled when a user disconnects from network
+ - II. Pre-Scheduled Service (PSS):**
+ - MDS provided in a pre-scheduled manner when a user connects to network
+ - MDS cancelled when a user disconnects from network
+ - III. On-Demand Service (ODS):**
+ - MDS provided when a user requests the MDS on demand
+ - MDS cancelled when a user requests the MDS to end
+- Service provisioning from control process participation related viewpoint:**
+ - I. No MDS control process participation**
+ - II. MDS control process participation**
+
+Connections: Subscription-based MDS maps to AoS and PSS. Non-subscription based MDS maps to ODS. AoS and PSS map to 'No MDS control process participation'. ODS maps to 'MDS control process participation'.
+
+Y.2212(08)F6-2
+
+Figure 6-2: Relationship between MDS service provisioning types. The diagram shows three columns of boxes. The first column, 'Service provisioning from subscription related viewpoint', contains 'I. Subscription-based MDS' (with sub-points: Need prior MDS subscription process, MDS control policy applies when user connects) and 'II. Non-subscription based MDS' (with sub-points: No need prior MDS subscription process, MDS control policy applies when user requests on demand). The second column, 'Service provisioning from service request related viewpoint', contains 'I. Always on Service (AoS)' (MDS provided on connect, no concern about traffic, cancelled on disconnect), 'II. Pre-Scheduled Service (PSS)' (MDS provided pre-scheduled, cancelled on disconnect), and 'III. On-Demand Service (ODS)' (MDS provided on request, cancelled on request to end). The third column, 'Service provisioning from control process participation related viewpoint', contains 'I. No MDS control process participation' and 'II. MDS control process participation'. Lines connect the first column to the second, and the second to the third, showing the mapping between these viewpoints.
+
+Figure 6-2 – Relationship between MDS service provisioning types
+
+# 7 Service requirements of MDS
+
+This clause describes the service requirements for the provision of MDS.
+
+## **7.1 Requirements for MDS service classification**
+
+MDS allows the third-party provider to request different levels of relevant resources and network capabilities, which are identified in NGN release 1. The usage of new or extended capabilities identified in NGN R2 is not precluded. The key components comprising MDS are to be identified as follows:
+
+- Traffic handling: It is required to be able to classify traffic in order to enable QoS differentiation of the traffic according to the third-party provider's application requirements.
+- Bandwidth instantiation control: It is required to be able to control bandwidth. It is recommended that this control be classified in two way: one for amount of bandwidth and the other for control of bandwidth, such as on-demand, semi-permanent, or permanent
+- Admission control (AC): This is required to be classified based on the third-party provider's service policies and business model, such as "always admitted", "premium class admitted", "admission only when available", etc.
+- Class of security: It is required to be able to differentiate levels of security, such as level of firewalls, AAA, level of traversal in NAPT, privacy, etc.
+- Other capabilities: The usage of new or extended capabilities identified in NGN R2 is not precluded (e.g., multicast).
+
+## **7.2 Requirements for MDS service partnership**
+
+The third-party provider is recommended to have an MDS partnership with the NGN provider, based on the MDS service profile given by the NGN provider, before providing MDS to users.
+
+MDS service provisioning is recommended to be carried out according to the result of the MDS partnership between the NGN provider and the third-party provider.
+
+The NGN provider is recommended to update the status of service partnership with the third-party provider after its service partnership is confirmed.
+
+The management of MDS partnerships is recommended to be performed online through ANI or offline.
+
+## **7.3 Requirements for the use of profiles for MDS**
+
+It is recommended that the MDS service profile be prepared by the NGN provider to enable the third-party provider to select NGN capabilities. It is also recommended that the MDS service profile be classified using several combinations, according to NGN network capabilities.
+
+It is recommended that the MDS service profile allow for choices of different levels of resources relevant to services, network capabilities, and resulting cost.
+
+The MDS service profile is recommended to be selected by the third-party provider, according to its specific service requirements.
+
+It is recommended that the third-party provider maintain the user profile.
+
+It is recommended that the third-party provider transfer its third-party provider profile and the user profile regarding its users to the NGN provider, after forming a partnership with the NGN provider.
+
+It is recommended that user discover the types of MDS that are available from third-party providers, via online or offline methods.
+
+It is recommended that the NGN provider maintain MDS control profile.
+
+In addition, it is recommended that the NGN provider collect and maintain MDS accounting and charging related information.
+
+## **7.4 MDS control requirements**
+
+It is recommended that MDS control, such as session/resource control, be carried out by the NGN provider. In order to achieve this, MDS control profile is used internally in the NGN provider.
+
+## **7.5 Authentication and authorization requirements**
+
+The user is required to be authenticated and authorized by the third-party provider to use MDS provided by the third-party provider.
+
+The user is required to be authenticated and authorized by the NGN provider to access the network in which the MDS is provided.
+
+The third-party provider is required to be authenticated and authorized by the NGN provider to use the MDS.
+
+# **8 Profiles for MDS management**
+
+This clause identifies high-level requirements and profiles for the maintenance and exchange of MDS-related information that is required to be properly shared and maintained between the NGN provider, the third-party provider, and the user.
+
+## **8.1 General requirements of MDS related profiles**
+
+It is recommended that the NGN provider and the third-party provider maintain, exchange, and update appropriately relevant information for the provision of MDS.
+
+The profiles relevant to each player, including the user and the provider, for support of MDS are recommended to be as follows:
+
+- a) The NGN provider is required to maintain at least the following profiles:
+ - i) MDS service profile;
+ - ii) Third-party provider profile (this information is transferred from the third-party provider);
+ - iii) User profile (this information is transferred from the third-party provider);
+ - iv) MDS control profile (this information is maintained internally in the NGN provider);
+ - v) Others: for further study;
+- b) The third-party provider is required to maintain at least the following profiles:
+ - i) Third-party provider profile: Third-party provider identification information, service server's address and status information, and other information as needed (this information is required to be transferred to the NGN provider);
+ - ii) User profile (this information is transferred to the NGN provider);
+ - iii) Others: for further study;
+- c) The user is required to have access to at least the following profiles:
+ - i) Third-party provider profile (this information is transferred from the third-party provider);
+ - ii) Others: for further study.
+
+Figure 8-1 shows the relationship of MDS-related profiles between players.
+
+
+
+The diagram illustrates the relationships between MDS-related profiles and the players involved: User, Third party provider, and NGN provider.
+
+- Third party provider (Yellow oval):**
+ - Owns and maintains a **3rd party pro. profile** (Solid box).
+ - Transfers an **MDS service profile** (Dashed box) from the NGN provider.
+ - Transfers a **3rd party pro. profile** (Dashed box) to the User.
+ - Transfers a **User profile** (Solid box) to the NGN provider.
+- NGN provider (Blue oval):**
+ - Owns and maintains an **MDS service profile** (Solid box).
+ - Owns and maintains an **MDS control profile** (Solid box) internally.
+ - Transfers an **MDS service profile** (Dashed box) to the Third party provider.
+ - Transfers a **User profile** (Dashed box) from the Third party provider.
+- User (Purple oval):**
+ - Receives a **3rd party pro. profile** (Dashed box) from the Third party provider.
+
+Legend for profile ownership/maintenance:
+
+- Solid boxes:** Owned and maintained by the provider.
+- Dashed boxes:** Transferred from another provider.
+
+Y.2212(08)\_F8-1
+
+Figure 8-1 – Relationship of MDS-related profiles between players. The diagram shows the flow of MDS-related profiles between a User, a Third party provider, and an NGN provider. Profiles are categorized as MDS service profiles, 3rd party profiles, or User profiles, and are either owned/maintained by a provider or transferred from one.
+
+**Figure 8-1 – Relationship of MDS-related profiles between players**
+
+## 8.2 MDS service profile
+
+An MDS service profile is recommended to be classified as one of several combinations, with various NGN network capabilities. The set of MDS service information is recommended to be selected by the third-party provider according to their service requirements.
+
+The basic information comprising the MDS service profile is as follows:
+
+- CoS (class of services) information: This information relates to the differentiation of traffic handling (e.g., switching and routing) services, according to the service requirements corresponding to different classes of services, such as best effort, premium, etc.
+- AC (admission control) information: This information relates to the admission control of MDS. Examples of priority classification schemes for admission of MDS include 'always admitted', 'premium class admitted', and 'admitted only when available', etc.
+- BiC (bandwidth instantiation control) information: This information relates to the bandwidth control according to the service requirements, such as on-demand, permanent, fixed, variable bandwidth, etc.
+- SeC (security control) information: This information relates to the control of the security level, such as the level of firewalls, AAA, level of traversal in NAPT, privacy, etc.
+- Multicast control information: This information relates to the multicast control of the MDS.
+- Others: for further study
+
+Usage examples of MDS service profile are shown in Table 1.
+
+**Table 1 – Usage of MDS service profiles**
+
+| CoS | AC | BiC | SeC | Service examples | |
+|---------------|---------------------------------------------|-----------------------------------------------|--------------|--------------------------------------------|--|
+| BE class | Always admitted via predetermined AC policy | Always on or Pre-scheduled or On-demand based | Not provided | BW pre-assigned network access | |
+| | | | Provided | BW pre-assigned network access w/ security | |
+| | Admitted only when available | | Not provided | BoD | |
+| | | | Provided | BoD w/ security | |
+| Premium class | Always admitted via predetermined AC policy | Always on or Pre-scheduled or On-demand based | Not provided | IP-Media, Video phone service | |
+| | | | Provided | IP-media/video phone Service w/ security | |
+| | Admitted only when available | | Not provided | Video phone service, BoD | |
+| | | | Provided | VoD/BoD w/ security | |
+
+## 8.3 Third-party provider profile
+
+This profile contains the relevant information of the third-party provider who has an MDS partnership with the NGN provider. The NGN provider maintains and may modify this profile as required over the course of the partnership, to accommodate establishment, modification or cancellation of MDS.
+
+This profile is required to include the following information:
+
+- Addresses of the servers of the third-party provider
+- Server status information of the third-party provider
+- Others: for further study
+
+This profile can optionally include the following information:
+
+- Identifier of the third-party provider
+
+## 8.4 User profile
+
+This profile contains relevant information regarding the users of the third-party provider. The NGN provider maintains this profile for each third-party provider.
+
+This profile is required to include the following information:
+
+- User's IP address
+- User name
+- MDS service type (e.g., subscription-based MDS, non-subscription based MDS)
+- Subscriber log in ID for network access in case of subscription-based MDS
+- Detailed information about MDS service profile selected by the third-party provider (e.g., premium class for CoS, always admitted for AC, fixed bandwidth control for BiC, etc.)
+- Others: for further study
+
+This profile can optionally include the following information:
+
+- Subscriber log in ID for network access in case of the non-subscription based MDS
+
+## **8.5 MDS control profile**
+
+This profile contains information regarding service control, session control, resource control and transport control to support MDS.
+
+This profile is required to include the following information:
+
+- Subscriber log session information for network access: Subscriber log related session information that is created or cancelled when the subscriber is logging into or out of the network
+- Subscriber default service policy information for network access: Default service policy information given to a network subscriber when the subscriber is logging into the network
+- User session information: User session information that is created or cancelled when a subscription-based MDS user is logging into or out of the network, or when a non-subscription based MDS user requests MDS or demands that the MDS be terminated
+- Network topology information: Information for MDS routing that provides network topology information about network nodes and links
+- Network resources information: Network link-related resources information
+- Network node information: Network node related information for dynamic policy control of network nodes
+- Others: for further study
+
+#### **8.5.1 Subscriber log session information of network access**
+
+This information contains subscriber log related session information, which is created or cancelled when a subscriber is logging into or out of the network.
+
+The following elements are required to be included in this set of information:
+
+- Subscriber IP address of network access
+- Subscriber MAC address of network access
+- Subscriber log in ID of network access
+- IP address of transport resource control node (T17/Figure 9-1) associated with access network
+- IP address of access relay node (T-4/Figure 9-1)
+- IP address and port number of edge node (T-3/Figure 9-1)
+- IP address and port number of access node (T-2/Figure 9-1)
+- IP address and port number of access media gateway node (T-1/Figure 9-1)
+- Subscriber basic connection service policy of network access
+- Subscriber connection bandwidth of network access
+- Subscriber service lists of network access
+- Subscriber log in time of network access
+- Others: for further study
+
+#### **8.5.2 Subscriber default service policy information of network access**
+
+This information contains default network access service policy information given to a subscriber when he or she is logging into the network.
+
+The following elements are required to be included in this set of information:
+
+- Subscriber IP address of network access
+- Subscriber basic connection service policy of network access
+
+- Others: for further study
+
+#### **8.5.3 User session information**
+
+This information contains the user's service session information, which is created and cancelled when the subscription-based MDS user is logging into or out of the network access, and when the non-subscription based MDS user requests MDS or demands that the MDS be terminated.
+
+The following elements are required to be included in this set of information:
+
+- User IP address
+- IP address and port number of MDS source
+- IP address and port number of MDS destination
+- Protocol types (e.g. TCP, UDP, etc.) for MDS
+- Detailed information about the MDS service profile selected by the third-party provider (e.g., premium class for CoS, always admitted for AC, fixed bandwidth control for BiC, etc.)
+- Network topology information of the MDS routing path
+- IP addresses and status information of service control nodes, session control nodes and transport control nodes involved in the MDS routing path
+- IP addresses, port numbers and status information of transport nodes involved in the MDS routing path
+- Link-related resources information in the MDS routing path
+- MDS usage time
+- Others: for further study
+
+#### **8.5.4 Network topology information**
+
+This contains information for MDS routing, and is comprised of network node and link information.
+
+The following elements are required to be included in this set of information:
+
+- IP addresses, port numbers and status information of transport nodes
+- Link configuration and status information between transport nodes
+- Others: for further study
+
+#### **8.5.5 Network resources information**
+
+This contains network link related resources information.
+
+The following elements are required to be included in this set of information:
+
+- Information of links between transport nodes (e.g., link bandwidth, etc.)
+- Others: for further study
+
+#### **8.5.6 Network node information**
+
+This contains network node related information for dynamic policy control of network nodes.
+
+The following elements are required to be included in this set of information:
+
+- IP addresses and status information of service control nodes, session control nodes, transport control nodes and transport nodes
+- Port numbers of transport nodes
+- Others: for further study
+
+# **9 Functional architecture**
+
+## **9.1 Functional architecture model**
+
+#### **9.1.1 Reference architecture model**
+
+It is recommended that the MDS functional architecture model be based on the functional architecture model, as in [ITU-T Y.2012], which identifies the NGN functional architecture model. Figure 9-1 and the accompanying Notes (see Notes 1 through 11) are excerpted from the functional architecture model from [ITU-T Y.2012], which is recommended to be a reference model for an MDS functional architecture model.
+
+
+
+The diagram illustrates the NGN generalized functional architecture, organized into several layers and functional blocks:
+
+- Applications Layer:** Includes 'Applications' and 'Application support functions & service support functions (may include own authentication, authorization and accounting)'.
+- Service Control Layer:** Contains various Service Functions (S-1 to S-15) such as S-1: Serving call session control FE, S-2: Proxy call session control FE, S-3: Interrogating call session control FE, S-4: Subscription locator FE, S-5: S. user profile FE, S-6: S. authentication and authorization FE, S-7: Interconnection border gateway control FE, S-8: Access GW control FE, S-9: Media GW control FE, S-10: Breakout gateway control FE, S-11: User signaling interworking FE, S-12: Network signalling interworking FE, S-13: Media resource control FE, S-14: Media resource broker FE, and S-15: General services control FE.
+- Transport Layers:**
+ - Access Transport:** Includes T-1: Access media gateway FE, T-2: Access node FE, T-3: Edge node FE, T-4: Access relay FE, T-11: T. authentication & authorization FE, T-12: T. user profile FE, T-13: T. location management FE, T-14: Access management FE, and T-15: Home gateway Configuration FE.
+ - Core Transport:** Includes T-5: Access border gateway FE, T-6: Interconnection border gateway FE, T-7: Trunking media gateway FE, T-8: Media resource processing FE, T-9: Signalling gateway FE, T-16: Policy decision FE, and T-17: Transport Resource control FE.
+- Management Functions:** A vertical block on the left side, connected to various parts of the architecture.
+- End-user Functions:** Located on the left, including 'Legacy terminal', 'RGW', 'Customer network', 'NGN terminal', and another 'Legacy terminal'.
+- External Networks:** On the right, including 'Other NGN', 'IP multimedia networks', and 'PSTN/ISDN'.
+- Scope of NGN:** Indicated by a large yellow double-headed arrow at the bottom, spanning from the end-user functions to the external networks.
+
+Figure 9-1 – NGN generalized functional architecture diagram showing the flow from Applications and Management functions through various service and transport layers to end-user functions and external networks.
+
+Y.2212(08)\_F9-1
+
+**Figure 9-1 – NGN generalized functional architecture (refer to Notes below)**
+
+NOTE 1 – The T-10 network access configuration FE can optionally reside in a visited network or a home network. It depends on the administrative domain and the business scenario.
+
+NOTE 2 – Lines terminating on the dotted box around S-4 and S-5 indicate connection to both internal FEs. Inclusion of these two FEs in the dotted box does not imply that they are collocated.
+
+NOTE 3 – Allocation of some functions to the IBG-FE needs further study: IBG-FE can/cannot optionally perform media conversion under the control of IBC-FE. A direct link between IBG-FE and IBC-FE is for further study. (Refer to clause 9.3.1.6 of [ITU-T Y.2012] on T-6 IBG-FE.)
+
+NOTE 4 – The NGN-UNI line shows the functional aspect only, and is recommended to not make any pre-decision about an ownership domain.
+
+NOTE 5 – More precise location and distinction of possible NGN-UNIs are for further study.
+
+NOTE 6 – As an option, P-CSC-FE, I-BGC-FE, BGC-FE, and MGC-FE interact with MRC-FE in support of invoking transcoding.
+
+NOTE 7 – Although it is located in the service control functions, the MRB-FE is recommended to be viewed as a part of application support functions and service support functions.
+
+NOTE 8 – Although the scope of this Recommendation is targeted primarily at an NGN architecture, it is clear that the accommodation of legacy PSTN/ISDN terminals and/or interworking with the PSTN/ISDN is an important consideration with respect to NGN deployment. Thus, to provide a more comprehensive view, AMG-FE required to accommodate PSTN/ISDN terminals is shown even though they are not strictly part of the NGN architecture itself.
+
+NOTE 9 – \* indicates multiple links from management functions towards applications, service control, NACF, RACF, access transport, and core transport.
+
+NOTE 10 – This figure does not show any linkage between two same FEs, though it is not precluded.
+
+NOTE 11 – The relationship between S-7 and S-12 needs further study with regard to the interaction with other networks. The relationship of S-7 and S-12 with other NGN needs further study.
+
+#### **9.1.2 MDS functional architecture model**
+
+Figure 9-2, as well as the accompanying Notes (see Notes 1 through 3) show the overall MDS functional architecture model based on [ITU-T Y.2012] (NGN functional architecture model).
+
+
+
+Y.2212(08)\_F9-2
+
+Figure 9-2 – MDS functional architecture model. This diagram illustrates the functional architecture of the MDS (Management and Service Delivery) system. At the top, a row of service boxes includes 'Network storage service with BoD', 'VoD service', 'Virtual private leased line service', 'Network controlled e-learning services', 'Video phone service', 'Video conferencing/collaboration service', 'IP-TV service', and '3rd party provider service platform'. These services interface with the 'NGN control platform' via an 'ANI' (Application Network Interface). The NGN control platform is divided into 'Management functions' and 'End-user functions'. Management functions include 'Application support functions and service support functions + Service control functions' and 'Service provider management (Note 1)'. End-user functions include 'Transport control functions' and 'Transport functions'. The 'Transport control functions' are further divided into 'Session control' and 'Terminal access control (Note 3)'. Session control includes 'S-1: Serving call session control FE', 'S-2: Proxy call session control FE', 'S-3: Interrogating call session control FE', 'S-4: Subscription locator FE', 'S-5: S. user profile FE', 'S-6: S. authentication and authorization FE', 'S-13: Media resource control FE', and 'S-14: Media resource broker FE'. Terminal access control includes 'T-10: Network access configuration FE', 'T-11: T. authentication and authorization FE', 'T-12: T. user profile FE', 'T-13: T. location management FE', 'T-16: Policy decision FE in access node', 'T-16: Policy decision FE in core node', and 'T-17: Transport resource control FE in access node'. The 'Transport functions' include 'Access node', 'Edge node', and 'Core node'. A 'MDS partnership and subscription management platform' is also shown, connected to the NGN control platform and the 'MDS partnership and subscription management functions'.
+
+**Figure 9-2 – MDS functional architecture model**
+
+NOTE 1 – Service provider management function: Its functions, e.g., authentication of service providers and their authorization to use MDS, handling of service requests across an interface, are mainly for the interworking between third-party providers and NGN providers. These are similar to the functions provided by A-2 (application gateway FE). The only difference between this function and A-2 is that this function supports the interworking between the third-party applications and service coordination function, whereas A-2 supports the interworking between applications and S-CSC-FE.
+
+NOTE 2 – Service coordination function: Similar to A-3 (application service coordination manager FE), this function plays a mutually coordinating role between services. The only difference is that A-3 only coordinates between applications, whereas this function coordinates not only between applications but also between application and transport control functions related nodes, such as 'Policy decision FE' and 'T-17: Transport resource control FE in access node'.
+
+NOTE 3 – Terminal access control function: This Function controls terminal access, by identifying terminal profile information and transferring its results to the access part of resource control management FEs, such as T-16 and T-17. This FE is not defined in [ITU-T Y.2012], so further clarification is requested to support this function in line with [ITU-T Y.2012].
+
+Table 2 shows the relationship between MDS functions in terms of NGN functional elements as in [ITU-T Y.2012]. The key differences between MDS functions and [ITU-T Y.2012] FEs are summarized as follows:
+
+**Table 2 – Differences between MDS functions and FEs in [ITU-T Y.2012]**
+
+| MDS Functions | | Y.2012 FEs | |
+|-----------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------------------------------------------------------|---------------|
+| Service Provider Management | - – Open I/F for 3rd party provider to use the MDS
- – SP authentication & authorization
- – Processing of service request from SP
| Application Support Functions & Service Support Functions | A-2 (Note 1) |
+| Service Coordination | - – Processing of service request from SP
| | A-3 (Note 2) |
+| Session Control | - – Functions related to session control
| Service Control Functions | S-1 |
+| | | | S-2 |
+| | | | S-3 |
+| | | | S-13 |
+| | | | S-14 |
+| Terminal Access Control | - – Terminal access control of the network
| Transport Control Functions | T-11 (Note 3) |
+
+### 9.2 MDS functional elements
+
+#### 9.2.1 MDS functional elements in ASF&SSF (application support functions & service support functions)
+
+- Service provider management function (A-2): This function handles the identification and authentication of third-party providers and processing of MDS service requests. As such, open interface (ANI) should be supported for third-party providers.
+
+#### 9.2.2 MDS functional elements in SCF (service control functions)
+
+- General service control FE (S-15): This FE handles non-session control related service requests and third-party service requests. For the handling of services binding with MDS, this FE could be coordinated with the service coordination function performing mutual interactive control between services. For the handling of services without binding MDS, this FE directly requests policy decision FE for resources arrangements or transport resource control FE (T-17) for routing arrangements.
+- Session control function (S-1, S-2, S-3, S-13 and S-14): This function handles functionality related to session control. This function is recommended to be implemented in the same manner as P-CSC-FE, S-CSC-FE, and I-CSC-FE depending on the implementation scenarios. For the handling of services binding with MDS, this function is recommended to be coordinated with service coordination function performing mutual interactive control between services. For the handling of services without binding MDS, this function directly requests policy decision FE for resources arrangements.
+- Service coordination function (A-3): This function handles mutual coordination roles between services. In case of a service requiring resource control function, this function is recommended to coordinate with policy decision FE; whereas in case of a service not requiring resource control function, this function is recommended to coordinate directly with transport resource control FE (T-17) for path control management (e.g., tunnelling etc.).
+- Service authentication and authorization FE (S-6): This FE handles the authentication and authorization of the requested services in coordination with general service control FE (S-15) and session control function.
+
+#### 9.2.3 MDS functional elements in TCF (transport control functions)
+
+- Policy decision FE (core node: T-16): This FE handles resource control functions in the core network and manages information for the core network topology and relevant resources.
+- Policy decision FE (access node: T-16): This FE handles resource control functions in the access network and manages information for access network topology and relevant resources.
+- Transport resource control FE (core node: T-17): This FE is responsible for transport technology-dependent resource control. This FE collects and maintains network information and resource status information (see clause 7.2.3.3 of [ITU-T Y.2111]).
+- Transport resource control FE (access node: T-17): This FE controls edge and access nodes in the access network and performs the functions of authentication for user's network attachment, policy control of access/edge node, and provision of tunnelling functions to servers.
+- Terminal access control function (N/A): This function controls terminal access. As such, this function identifies terminal profile information and transfers it to the terminal and edge node control FE.
+- Network access configuration FE (T-10): This FE handles the IP assignment to the terminal, e.g., DHCP server. This FE provides terminal upgrade information and carries out its upgrades.
+- Transport authentication and authorization FE (T-11): This FE performs authentication and authorization functions in the transport stratum. This FE performs user authentication as well as authorization checking based on the user profiles for network access.
+- Transport user profile FE (T-12): This FE is responsible for storing user profiles (e.g., QoS profile, session control function address, and HGWC-FE address) related to the transport stratum.
+- Transport location management functional entity (T-13): This FE registers the association between the IP address allocated to the user equipment and related network location information provided by NAC-FE (e.g., access line identifier). This FE also registers the association between the network location information received from NAC-FE and geographical location information.
+
+# 10 MDS service scenarios
+
+### 10.1 Subscription-based MDS service scenario
+
+Subscription-based MDS is provisioned on an AoS, PSS or ODS basis.
+
+When provisioned on an AoS/PSS basis, two different types of subscription-based MDS service scenarios are distinguished, depending on whether the third-party provider participates in the MDS control process (Type II) or not (Type I).
+
+In the case of Type I, when a user connects to the network, the NGN provider provides MDS on its own, according to the agreements on partnership and subscription.
+
+In the case of Type II, the third-party provider requests for network control related to MDS after being informed of the user's network access by the NGN provider.
+
+#### 10.1.1 Subscription-based MDS service scenario – Type I
+
+The transport control functions of NGN carry out the relevant network controls according to the result of MDS service subscription in the subscription-based MDS Type I scenario. The subscription-based MDS Type I provisioning mechanism is as follows (see Figure 10-1):
+
+- 1) It is recommended that the third-party provider have an MDS partnership with the NGN provider. This partnership may be formed online and/or offline.
+- 2) A user may request an MDS subscription from the third-party provider online and/or offline.
+- 3) The third-party provider queries the subscription availability of the user to the NGN provider. This will depend on the status of the partnership between the third-party provider and the NGN provider.
+- 4) The NGN provider informs the third-party provider of the result of the user's MDS subscription.
+- 5) The third-party provider informs the user requesting for MDS of the result of the service subscription.
+- 6) The user of the third-party provider connects to the network.
+- 7) The NGN provider recognizes this network connection through the network connection information of the user.
+- 8) The NGN provider carries out MDS related network controls according to the agreements formed during the MDS partnership and subscription.
+- 9) The user then uses the service using MDS between the user and the third-party provider or between the user and another user.
+
+
+
+The diagram illustrates the subscription-based MDS provisioning mechanism – Type I. It shows the interaction between a 3rd party provider service platform, the NGN control platform, and users.
+
+**Entities and Components:**
+
+- 3rd party provider service platform:** An orange box at the top center.
+- NGN control platform:** A yellow box in the middle, containing:
+ - Management functions (vertical oval)
+ - Application support functions and service support functions (horizontal oval)
+ - Session control functions (horizontal oval)
+ - Transport control functions (horizontal oval)
+- MDS partnership and subscription management platform:** A green box to the right of the NGN control platform, containing:
+ - MDS partnership and subscription management platform (top section)
+ - MDS partnership and subscription management functions (bottom section)
+- Users:** Represented by stick figures at the bottom left and right.
+- Transport functions:** A blue cloud at the bottom center.
+- ANI (Access Network Interface):** A thick blue horizontal line separating the 3rd party provider from the NGN control platform.
+
+**Flow of Operations:**
+
+- (1) MDS partnership:** A solid blue line connecting the 3rd party provider and the NGN control platform.
+- (2) MDS subscription request:** A dashed arrow from the 3rd party provider to the NGN control platform.
+- (3) MDS subscription request:** A dashed arrow from the 3rd party provider to the MDS partnership and subscription management platform.
+- (4) MDS subscription reply:** A dashed arrow from the MDS partnership and subscription management platform to the 3rd party provider.
+- (5) MDS subscription reply:** A dashed arrow from the 3rd party provider to the user on the left.
+- (6) Network access:** A solid arrow from the user on the left to the Transport functions cloud.
+- (7) User's network access info:** A dashed arrow from the Transport functions cloud to the NGN control platform.
+- (8) Transport control:** A dashed arrow from the NGN control platform to the Transport functions cloud.
+
+The diagram is labeled Y.2212(08)\_F10-1 in the bottom right corner.
+
+Figure 10-1: Subscription-based MDS provisioning mechanism – Type I. The diagram illustrates the flow of MDS subscription requests and network access between a 3rd party provider, the NGN control platform, and users.
+
+**Figure 10-1 – Subscription-based MDS provisioning mechanism – Type I**
+
+The subscription-based MDS Type I service scenario is as follows (see Figure 10-2):
+
+- 1) It is recommended that the third-party provider have an MDS partnership with the NGN provider. This partnership may be formed online and/or offline. MDS subscription between the user and the third-party provider via the NGN provider is processed.
+- 2) The network connection information of the user is transferred to transport resource control FE (T-17) via access node.
+- 3) Transport resource control FE (T-17) transfers information related to the session and topology to policy decision FE (T-16) in access node.
+- 4) Policy decision FE (T-16) enforces the resource control policy on transport resource control FE (T-17) and terminal access control function.
+- 5) Transport resource control FE (access node: T-17) applies the policy to access node and terminal access control function applies the policy to end-user functions.
+- 6) The user starts to use MDS as the result of MDS resource control and/or routing control.
+
+
+
+Figure 10-2: Subscription-based MDS service scenario – Type I. This diagram illustrates the architecture and data flow for MDS Type I service. At the top, a row of service boxes includes 'Network storage service with BoD', 'VoD service', 'Virtual private leased line service', 'Network controlled e-learning services', 'Video phone service', 'Video conferencing/collaboration service', and 'IP-TV service', all connected to a '3rd party provider service platform'. Below this is the 'NGN control platform' which is divided into 'Management functions' and 'End-user functions'. The 'Management functions' section includes 'Service provider management (Note 1)', 'S-5: S. user profile FE', 'S-4: Subscription locator FE', 'S-6: S. authentication and authorization FE', 'S-1: Serving call session control FE', 'S-2: Proxy call session control FE', 'S-3: Interrogating call session control FE', 'S-13: Media resource control FE', 'S-14: Media resource broker FE', and 'S-15: General service control FE'. The 'End-user functions' section includes 'Terminal access control (Note 3)', 'T-10: Network access configuration FE', 'T-12: T. user profile FE', 'T-13: T. location management FE', 'T-11: T. authentication and authorization FE', 'T-16: Policy decision FE in access node', 'T-16: Policy decision FE in core node', 'T-17: Transport resource control FE in access node', and 'T-17: Transport resource control FE in core node'. At the bottom, 'Transport functions' are shown with 'Access node', 'Edge node', and 'Core node'. Red dashed arrows with numbers 1 through 6 indicate the sequence of operations: 1) from 3rd party platform to MDS partnership management; 2) from Access node to T-17 in core node; 3) from T-17 in core node to T-16 in core node; 4) from T-16 in core node to T-16 in access node; 5) from T-16 in access node to T-17 in access node; 6) from T-17 in access node to the user. A vertical bar on the left indicates 'Management functions' and 'End-user functions' are interconnected. A vertical bar on the right indicates 'MDS partnership and subscription management platform' and 'MDS partnership and subscription management functions' are interconnected. The diagram is labeled 'Y.2212(08)\_F10-2' at the bottom right.
+
+**Figure 10-2 – Subscription-based MDS service scenario – Type I**
+
+#### 10.1.2 Subscription-based MDS service scenario – Type II
+
+After being informed of the user's network access by the NGN provider, the third-party provider requests for network control related to MDS in the subscription-based MDS Type II service scenario.
+
+The subscription-based MDS Type II provisioning mechanism is as follows (see Figure 10-3):
+
+- 1) It is recommended that the third-party provider have an MDS partnership with the NGN provider. This partnership may be formed by online and/or offline.
+- 2) A user requests for MDS subscription from the third-party provider online and/or offline.
+- 3) The third-party provider queries the NGN provider regarding the availability of the user's desired subscription. This will depend on the status of partnership between the third-party provider and the NGN provider.
+- 4) The NGN provider informs the third-party provider of the query result regarding the user's desired MDS subscription.
+- 5) The third-party provider informs the user requesting for MDS of the result of the service subscription.
+- 6) The user of the third-party provider connects to the network.
+- 7) The NGN provider recognizes this network connection through the network connection information of the user.
+- 8) The NGN provider informs the third-party provider of the user's network access information.
+- 9) The third-party provider requests for MDS related network controls from the NGN provider.
+- 10) The NGN provider carries out MDS related network controls, according to the agreements formed during the MDS partnership and subscription.
+- 11) The user then uses the service using MDS between the user and the third-party provider, or between the user and another user.
+
+
+
+The diagram illustrates the interaction between a User, a 3rd party provider service platform, an NGN control platform, and an MDS partnership and subscription management platform. The flow is as follows:
+
+- (1) MDS partnership established between the 3rd party provider and the MDS partnership platform.
+- (2) User sends an MDS subscription request to the 3rd party provider.
+- (3) 3rd party provider forwards the MDS subscription request to the MDS partnership platform.
+- (4) MDS partnership platform sends an MDS subscription reply back to the 3rd party provider.
+- (5) 3rd party provider sends an MDS subscription reply to the User.
+- (6) User performs Network access via Transport functions.
+- (7) User's network access info is sent from Transport functions to the NGN control platform.
+- (8) User's network access info is relayed from the NGN control platform to the 3rd party provider.
+- (9) 3rd party provider sends a Transport control request to the NGN control platform.
+- (10) NGN control platform sends Transport control commands to the Transport functions.
+
+The NGN control platform contains Management functions, Application support functions and service support functions, Session control functions, and Transport control functions. The MDS partnership platform contains MDS partnership and subscription management functions. An ANI (Application Network Interface) line separates the 3rd party provider from the NGN infrastructure.
+
+Figure 10-3 – Subscription-based MDS provisioning mechanism – Type II
+
+**Figure 10-3 – Subscription-based MDS provisioning mechanism – Type II**
+
+The subscription-based MDS Type II service scenario is as follows (see Figure 10-4):
+
+- 1) It is recommended that the third-party provider have an MDS partnership with the NGN provider. This partnership may be formed online and/or offline. MDS subscription between the user and the third-party provider via the NGN provider is processed.
+- 2) The network connection information of the MDS user is transferred to transport resource control FE (access node: T-17) via access node.
+- 3) Transport resource control FE (access node: T-17) transfers information related to the dynamic session and topology to policy decision FE (access node: T-16). Transport resource control FE (access node: T-17) also transfers information related to dynamic session and accounting to service provider management function (A-2) via service user profile FE (S-5) and subscription locator FE (S-4).
+- 4) Service provider management function (A-2) relays to the third-party provider information on the status of the user connected to the network, as obtained from service user profile FE (S-5) and subscription locator FE (S-4).
+- 5) The third-party provider requests for MDS from service provider management function (A-2).
+- 6) Service provider management function (A-2) requests for MDS related resources and/or relevant routing control from service coordination function (A-3).
+- 7) Service coordination function (A-3) requests for the relevant resources control from policy decision FE.
+- 8) Policy decision FE (T-16) enforces the resource control policy on transport resource control FE (T-17) and terminal access control function.
+- 9) Transport resource control FE (access node: T-17) applies the policy to access node and terminal access control function applies the policy to end-user functions.
+- 10) The user starts to use MDS as the result of MDS resource control and/or routing control.
+
+**Rec. ITU-T Y.2212 (02/2008)** 21
+
+
+
+The diagram illustrates the functional architecture for a Subscription-based MDS service scenario (Type II) within an NGN (Next Generation Network) framework. It is divided into several horizontal and vertical planes:
+
+- Top Layer (Services):** Includes boxes for Network storage service with BoD, VoD service, Virtual private leased line service, Network controlled e-learning services, Video phone service, Video conferencing/collaboration service, and IP-TV service. A '3rd party provider service platform' is on the far right.
+- NGN Control Platform (Yellow Box):** Contains 'Application support functions and service support functions' and 'Service control functions'. Key components include 'Service provider management', 'S-6: S. authentication and authorization FE', 'Session control' (with S-1, S-2, S-3 FEs), 'S-5: S. user profile FE', 'S-4: Subscription locator FE', 'S-15: General service control FE', 'Service coordination', and media resource control/broker FEs (S-13, S-14).
+- Transport Control Functions (Lower Yellow Box):** Includes 'T-10: Network access configuration FE', 'T-12: T. user profile FE', 'T-13: T. location management FE', 'Terminal access control', 'T-11: T. authentication and authorization FE', and various 'Policy decision FEs' (T-16) and 'Transport resource control FEs' (T-17) for access and core nodes.
+- Transport Functions (Bottom Layer):** Shows 'Access node', 'Edge node', and 'Core node' connected by transport lines.
+- Management Functions (Left):** A vertical block interacting with the control platform.
+- End-user Functions (Left):** A vertical block interacting with transport and control functions.
+- MDS Management (Right):** Includes 'MDS partnership and subscription management platform' and 'MDS partnership and subscription management functions'.
+
+Numbered red circles (1 through 10) indicate a flow of control and data signals between these various entities, starting from the 3rd party provider and moving through the NGN control platform down to the transport layer.
+
+Figure 10-4 – Subscription-based MDS service scenario – Type II
+
+**Figure 10-4 – Subscription-based MDS service scenario – Type II**
+
+### 10.1.3 Subscription-based MDS service scenario – Type III
+
+The subscription-based MDS Type III provisioning mechanism is as follows (see Figure 10-5):
+
+- 1) It is recommended that the third-party provider have an MDS partnership with the NGN provider. This partnership may be formed online and/or offline.
+- 2) A user may request for an MDS subscription from the third-party provider online and/or offline.
+- 3) The third-party provider queries the subscription availability of the user with the NGN provider. This will depend on the status of the partnership between the third-party provider and the NGN provider.
+- 4) The NGN provider informs the third-party provider of the result of the user's MDS subscription.
+- 5) The third-party provider informs the user requesting for MDS of the result of the service subscription.
+- 6) A user requests for MDS from the third-party provider online.
+- 7) The third-party provider requests for MDS from the NGN provider.
+- 8) The NGN provider checks the availability of the requested MDS provision and carries out the relevant network resources control, according to the requested MDS.
+
+22 Rec. ITU-T Y.2212 (02/2008)
+
+- 9) The NGN provider informs the third-party provider of the service availability result, as obtained from the network resources control.
+- 10) The third-party provider informs the user of the result of the service request.
+- 11) The user then uses the service using MDS between the user and the third-party provider, or between the user and another user.
+
+
+
+Y.2212(08)\_F10-5
+
+Figure 10-5: Subscription-based MDS provisioning mechanism – Type III. The diagram illustrates the interaction between a 3rd party provider service platform, an NGN control platform, an MDS partnership and subscription management platform, and users. The 3rd party provider service platform (orange box) sends a (2) MDS subscription request and a (6) Service request to the NGN control platform (yellow box). The NGN control platform sends a (5) MDS subscription reply and a (10) Service provision to the 3rd party provider. The 3rd party provider also sends a (3) MDS subscription request and a (4) MDS subscription reply to the MDS partnership and subscription management platform (green box). The MDS platform sends a (1) MDS partnership request to the NGN control platform. The NGN control platform sends a (7) Resource control request to the 3rd party provider and a (9) Resource control reply to the MDS platform. The NGN control platform sends a (8) Transport control to the Transport functions (cloud). The Transport functions connect two Users. The ANI (Application Network Interface) is shown as a horizontal line separating the 3rd party provider from the NGN control platform.
+
+**Figure 10-5 – Subscription-based MDS provisioning mechanism – Type III**
+
+The subscription-based MDS Type III service scenario is as follows (see Figure 10-6):
+
+- 1) It is recommended that the third-party provider have an MDS partnership with the NGN provider. This partnership may be formed online and/or offline. MDS subscription between the user and the third-party provider via the NGN provider is processed.
+- 2) A user requests for MDS from the third-party provider.
+- 3) The third-party provider requests for the use of MDS from service provider management function (A-2).
+- 4) Service provider management function (A-2) evaluates the MDS request, and then requests for the relevant network resources control and/or route control from service coordination function (A-3).
+- 5) Service coordination function (A-3) requests for the resources control from policy decision FE.
+- 6) Policy decision FE (T-16) enforces the resource control policy on transport resource control FE (T-17) and terminal access control function.
+- 7) Transport resource control FE (access node: T-17) applies the policy to access node, and terminal access control function applies the policy to end-user functions.
+- 8) The NGN provider responds to the MDS request made from the third-party provider through service provider management function (A-2).
+
+- 9) The user starts to use MDS as the result of MDS resources control.
+
+
+
+Figure 10-6: Subscription-based MDS service scenario – Type III. This diagram illustrates the architecture and service flow for a subscription-based MDS service. At the top, a '3rd party provider service platform' (labeled 1) contains services like Network storage, VoD, Virtual private line, Network controlled e-learning, Video phone, Video conferencing, and IP-TV. This platform connects via ANI to the 'NGN control platform'. The NGN control platform is divided into 'Management functions' (Application support, Service control) and 'Transport control functions'. It includes various functional elements like S-1 to S-15 and T-10 to T-17. A '3rd party provider service platform' also connects to an 'MDS partnership and subscription management platform' (labeled 2), which in turn connects to the NGN control platform. The NGN control platform connects to 'Access node', 'Edge node', and 'Core node' via 'Transport functions' (labeled 9). The diagram is labeled Y.2212(08)\_F10-6.
+
+Figure 10-6 – Subscription-based MDS service scenario – Type III
+
+### 10.2 Non-subscription based MDS service scenario
+
+The non-subscription based MDS provisioning mechanism (Type IV) is as follows (see Figure 10-7):
+
+- 1) It is recommended that the third-party provider have an MDS partnership with the NGN provider. This partnership may be formed online and/or offline.
+- 2) A user requests for MDS from the third-party provider online.
+- 3) The third-party provider requests for MDS from the NGN provider.
+- 4) The NGN provider checks the availability of the requested MDS provision, and carries out the relevant network resources control, according to the requested MDS.
+- 5) The NGN provider informs the third-party provider of the service availability result, as obtained from the network resources control.
+- 6) The third-party provider informs the user of the result of the service request.
+- 7) The user then uses the service using MDS between the user and the third-party provider, or between the user and another user.
+
+
+
+Y.2212(08)\_F10-7
+
+Figure 10-7: Non-subscription based MDS provisioning mechanism – Type IV. The diagram illustrates the interaction between a 3rd party provider service platform, an NGN control platform, an MDS partnership and subscription management platform, and users. The 3rd party provider service platform (orange box) sends a (2) Service request to the NGN control platform (yellow box) and receives a (1) MDS partnership from the MDS partnership and subscription management platform (green box). The NGN control platform sends a (3) Resource control request to the MDS partnership and subscription management platform and receives a (5) Resource control reply. The MDS partnership and subscription management platform sends a (4) Transport control to the Transport functions (cloud). The Transport functions connect to two Users. The NGN control platform also sends a (6) Service provision to the 3rd party provider service platform. The ANI (Application Network Interface) is shown as a horizontal line separating the 3rd party provider service platform from the NGN control platform and the MDS partnership and subscription management platform.
+
+**Figure 10-7 – Non-subscription based MDS provisioning mechanism – Type IV**
+
+The non-subscription based MDS scenario is as follows (see Figure 10-8):
+
+- 1) It is recommended that the third-party provider have an MDS partnership with the NGN provider. This partnership may be formed online and/or offline.
+- 2) A user requests for MDS from the third-party provider.
+- 3) The third-party provider requests for the use of MDS from service provider management function (A-2).
+- 4) Service provider management function (A-2) evaluates the MDS request, and then requests for the relevant network resources control and/or route control from service coordination function (A-3).
+- 5) Service coordination function (A-3) requests for the resources control from policy decision FE.
+- 6) Policy decision FE (T-16) enforces the resource control policy on transport resource control FE (T-17) and terminal access control function.
+- 7) Transport resource control FE (access node: T-17) applies the policy to access node, and terminal access control function applies the policy to end-user functions.
+- 8) The NGN provider responds to the MDS request made from the third-party provider through service provider management function (A-2).
+- 9) The user starts to use MDS as the result of MDS resources control.
+
+
+
+Figure 10-8: Non-subscription based MDS service scenario – Type IV. The diagram illustrates a complex NGN architecture. At the top are various services: Network storage service with BoD, VoD service, Virtual private leased line service, Network controlled e-learning services, Video phone service, Video conferencing/collaboration service, and IP-TV service. A 3rd party provider service platform is on the far right. Below these is the NGN control platform (yellow box) containing Application support functions, Service control functions, and Transport control functions. Key functional entities (FEs) include Service provider management, S-5: S. user profile FE, S-4: Subscription locator FE, S-6: S. authentication and authorization FE, Session control (S-1, S-2, S-3), Media resource control (S-13, S-14), and S-15: General service control FE. The Transport control functions section includes T-10: Network access configuration FE, T-12: T. user profile FE, T-13: T. location management FE, Terminal access control, T-11: T. authentication and authorization FE, and Policy decision/Transport resource control FEs (T-16, T-17) for both access and core nodes. At the bottom are Transport functions: Access node, Edge node, and Core node. Numbered red circles (1-9) indicate specific signaling or data paths between these components. Management functions and End-user functions are shown as vertical bars on the left. MDS partnership and subscription management platforms are on the right. The ANI interface is marked between the NGN platform and the 3rd party provider.
+
+**Figure 10-8 – Non-subscription based MDS service scenario – Type IV**
+
+# 11 Security considerations
+
+Three key players are involved in MDS: the user, the NGN provider and the third-party provider. Each provider should equip its systems (or elements) to request for, use, control, and manage MDS, according to their roles and positions. Two interfaces should have a key role in communicating MDS: UNI between the user and the NGN provider, and ANI between the NGN provider and the third-party provider.
+
+The overall security framework of MDS is required to comply with [ITU-T Y.2701], which specifies the NGN security framework.
+
+The security trust relationship of MDS is described in Figure 11-1, based on the trust model identified in [ITU-T Y.2701].
+
+![Diagram illustrating the trust relationship of MDS based on [ITU-T Y.2701]. The diagram is divided into two main sections: 'Network elements owned by the NGN provider' and 'Network elements not necessarily owned by the NGN provider'. The first section is further divided into 'Trusted zone' (containing NGN elements) and 'Trusted but vulnerable zone' (containing Border elements). The second section is divided into 'Untrusted zone' (containing CPE, CPE-BE, and Provider-operated equipment). Arrows labeled 'MDS' point from these zones to a simplified architecture on the right, which includes 'NGN control platform', 'Elements for UNI', 'Elements for ANI', 'End user function', and '3rd party service platform'.](08dce7ad4c512fdf0c0cde60415fade6_img.jpg)
+
+The diagram illustrates the trust relationship of MDS based on [ITU-T Y.2701]. It is divided into two main sections: 'Network elements owned by the NGN provider' and 'Network elements not necessarily owned by the NGN provider'.
+
+**Network elements owned by the NGN provider:**
+
+- Trusted zone:** Contains NGN elements.
+- Trusted but vulnerable zone:** Contains Border elements.
+
+**Network elements not necessarily owned by the NGN provider:**
+
+- Untrusted zone:** Contains CPE, CPE-BE, and Provider-operated equipment (e.g. outside plant equipment).
+
+Arrows labeled 'MDS' indicate the mapping from these zones to a simplified architecture on the right:
+
+- NGN control platform** (from Trusted zone)
+- Elements for UNI** (from Trusted but vulnerable zone)
+- Elements for ANI** (from Trusted but vulnerable zone)
+- End user function** (from Untrusted zone)
+- 3rd party service platform** (from Untrusted zone)
+
+Y.2212(08)F11-1
+
+Diagram illustrating the trust relationship of MDS based on [ITU-T Y.2701]. The diagram is divided into two main sections: 'Network elements owned by the NGN provider' and 'Network elements not necessarily owned by the NGN provider'. The first section is further divided into 'Trusted zone' (containing NGN elements) and 'Trusted but vulnerable zone' (containing Border elements). The second section is divided into 'Untrusted zone' (containing CPE, CPE-BE, and Provider-operated equipment). Arrows labeled 'MDS' point from these zones to a simplified architecture on the right, which includes 'NGN control platform', 'Elements for UNI', 'Elements for ANI', 'End user function', and '3rd party service platform'.
+
+**Figure 11-1 – Trust relationship of MDS based on [ITU-T Y.2701]**
+
+
+
+
+
+## SERIES OF ITU-T RECOMMENDATIONS
+
+| | |
+|-----------------|--------------------------------------------------------------------------------------------------|
+| Series A | Organization of the work of ITU-T |
+| 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 | 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 |
\ No newline at end of file
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@@ -0,0 +1,847 @@
+
+
+# ITU-T
+
+TELECOMMUNICATION
+STANDARDIZATION SECTOR
+OF ITU
+
+## Y.2305
+
+(05/2018)
+
+SERIES Y: GLOBAL INFORMATION
+INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS,
+NEXT-GENERATION NETWORKS, INTERNET OF
+THINGS AND SMART CITIES
+
+Next Generation Networks – Enhancements to NGN
+
+# --- **Unified management of content delivery networks**
+
+Recommendation ITU-T Y.2305
+
+## ITU-T Y-SERIES RECOMMENDATIONS
+
+## GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS, NEXT-GENERATION NETWORKS, INTERNET OF THINGS AND SMART CITIES
+
+## GLOBAL INFORMATION INFRASTRUCTURE
+
+| | |
+|-------------------------------------------|-------------|
+| General | Y.100–Y.199 |
+| Services, applications and middleware | Y.200–Y.299 |
+| Network aspects | Y.300–Y.399 |
+| Interfaces and protocols | Y.400–Y.499 |
+| Numbering, addressing and naming | Y.500–Y.599 |
+| Operation, administration and maintenance | Y.600–Y.699 |
+| Security | Y.700–Y.799 |
+| Performances | Y.800–Y.899 |
+
+## INTERNET PROTOCOL ASPECTS
+
+| | |
+|--------------------------------------------------------------------|---------------|
+| General | Y.1000–Y.1099 |
+| Services and applications | Y.1100–Y.1199 |
+| Architecture, access, network capabilities and resource management | Y.1200–Y.1299 |
+| Transport | Y.1300–Y.1399 |
+| Interworking | Y.1400–Y.1499 |
+| Quality of service and network performance | Y.1500–Y.1599 |
+| Signalling | Y.1600–Y.1699 |
+| Operation, administration and maintenance | Y.1700–Y.1799 |
+| Charging | Y.1800–Y.1899 |
+| IPTV over NGN | Y.1900–Y.1999 |
+
+## NEXT GENERATION NETWORKS
+
+| | |
+|-------------------------------------------------------------------|----------------------|
+| Frameworks and functional architecture models | Y.2000–Y.2099 |
+| Quality of Service and performance | Y.2100–Y.2199 |
+| Service aspects: Service capabilities and service architecture | Y.2200–Y.2249 |
+| Service aspects: Interoperability of services and networks in NGN | Y.2250–Y.2299 |
+| Enhancements to NGN | Y.2300–Y.2399 |
+| Network management | Y.2400–Y.2499 |
+| Network control architectures and protocols | Y.2500–Y.2599 |
+| Packet-based Networks | Y.2600–Y.2699 |
+| Security | Y.2700–Y.2799 |
+| Generalized mobility | Y.2800–Y.2899 |
+| Carrier grade open environment | Y.2900–Y.2999 |
+
+## FUTURE NETWORKS
+
+| | |
+|-----------------|---------------|
+| CLOUD COMPUTING | Y.3000–Y.3499 |
+| | Y.3500–Y.3999 |
+
+## INTERNET OF THINGS AND SMART CITIES AND COMMUNITIES
+
+| | |
+|---------------------------------------------------------|---------------|
+| General | Y.4000–Y.4049 |
+| Definitions and terminologies | Y.4050–Y.4099 |
+| Requirements and use cases | Y.4100–Y.4249 |
+| Infrastructure, connectivity and networks | Y.4250–Y.4399 |
+| Frameworks, architectures and protocols | Y.4400–Y.4549 |
+| Services, applications, computation and data processing | Y.4550–Y.4699 |
+| Management, control and performance | Y.4700–Y.4799 |
+| Identification and security | Y.4800–Y.4899 |
+| Evaluation and assessment | Y.4900–Y.4999 |
+
+*For further details, please refer to the list of ITU-T Recommendations.*
+
+## Recommendation ITU-T Y.2305
+
+# Unified management of content delivery networks
+
+## Summary
+
+Recommendation ITU-T Y.2305 specifies requirements, mechanisms and security considerations for unified management of multiple content delivery networks (CDNs), in order to support simple and optimized interconnection between different CDNs.
+
+This Recommendation provides a technical solution of a CDN manager with capabilities of content synchronization, user's request routing and other related unified management functionalities, to build up a global CDN.
+
+## History
+
+| Edition | Recommendation | Approval | Study Group | Unique ID* |
+|---------|----------------|------------|-------------|------------------------------------------------------------------------------|
+| 1.0 | ITU-T Y.2305 | 2018-05-29 | 13 | 11.1002/1000/13615 |
+
+## Keywords
+
+Content delivery network, management.
+
+---
+
+\* To access the Recommendation, type the URL in the address field of your web browser, followed by the Recommendation's unique ID. For example, .
+
+## 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 .
+
+© ITU 2018
+
+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 Convention..... | 2 |
+| 6 Introduction..... | 3 |
+| 6.1 Motivation for unified management of CDNs..... | 3 |
+| 6.2 Scenarios for unified management of CDNs ..... | 4 |
+| 7 Requirements for unified management of CDNs ..... | 5 |
+| 7.1 Request routing..... | 5 |
+| 7.2 Routing policy management..... | 5 |
+| 7.3 Requirements for CDN status management ..... | 6 |
+| 7.4 Requirements for content storage metadata management ..... | 6 |
+| 7.5 Requirements of network management ..... | 6 |
+| 7.6 Requirements of charging..... | 6 |
+| 8 Mechanisms for unified management of CDNs ..... | 7 |
+| 8.1 Framework for unified management of CDNs..... | 7 |
+| 8.2 Procedures of unified management on CDNs ..... | 9 |
+| 9 Security considerations for unified management of CDNs ..... | 12 |
+| Appendix I – Use cases of unified management of CDNs ..... | 13 |
+| Appendix II – Introduction of a DNS CNAME and URL forwarding mechanism ..... | 18 |
+| Bibliography..... | 19 |
+
+
+
+# Recommendation ITU-T Y.2305
+
+# Unified management of content delivery networks
+
+# 1 Scope
+
+This Recommendation specifies unified management of content delivery networks (CDNs), with the following aspects:
+
+- scenarios for unified management of CDNs;
+- requirements including request routing-related, CDN content, status, network-related, and charging-related descriptions;
+- mechanisms including the framework, procedures and other related functions for unified management of CDNs;
+- security considerations for unified management of CDNs.
+
+# 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 Y.2019] ITU-T Recommendation Y.2019 (2010), *Content delivery functional architecture in NGN*.
+
+# 3 Definitions
+
+### 3.1 Terms defined elsewhere
+
+This Recommendation uses the following terms defined elsewhere:
+
+**3.1.1 charging** [b-ITU-T Q.825]: The set of functions needed to determine the price assigned to the service utilization.
+
+**3.1.2 content** [b-ITU-T H.780]: A combination of audio, still image, graphic, video, or data.
+
+NOTE – A variety of formats is classified as the "data" (e.g., text, encoded values, multimedia description language introduced by [b-ITU-T H.760]).
+
+**3.1.3 content provider** [b-ITU-T Y.1910]: The entity that owns or is licensed to sell content or content assets.
+
+**3.1.4 end user** [b-ITU-T Y.1910]: The actual user of the products or services.
+
+**3.1.5 service** [b-ITU-T Y.2091]: A set of functions and facilities offered to a user by a provider.
+
+**3.1.6 service provider** [b-ITU-T M.1400]: A general reference to an operator that provides telecommunication services to customers and other users, either on a tariff or contract basis. A service provider may or may not operate a network. A service provider may or may not be a customer of another service provider.
+
+## 3.2 Terms defined in this Recommendation
+
+This Recommendation defines the following term:
+
+**3.2.1 content storage metadata:** The descriptive information of what the name of the content is and which content delivery network (CDN) it is stored in.
+
+NOTE – Often this metadata takes the form of an identifier and location (CDN name) that the content illustrates.
+
+# 4 Abbreviations and acronyms
+
+This Recommendation uses the following abbreviations and acronyms:
+
+| | |
+|-------|---------------------------------|
+| ACL | Access Control List |
+| AS | Application Server |
+| CDN | Content Delivery Network |
+| CNAME | Canonical Name |
+| CP | Content Provider |
+| DNS | Domain Name System |
+| EPC | Evolved Packet Core |
+| FCDN | Fixed Content Delivery Network |
+| IP | Internet Protocol |
+| KPI | Key Performance Indicator |
+| MCDN | Mobile Content Delivery Network |
+| NGN | Next Generation Network |
+| QoS | Quality of Service |
+| RAN | Radio Access Network |
+| SLA | Service Level Agreement |
+| URL | Uniform Resource Locator |
+
+# 5 Convention
+
+In this Recommendation:
+
+The keywords "is required to" indicate a requirement which must be strictly followed and from which no deviation is permitted if conformance to this document is to be claimed.
+
+The keywords "is prohibited from" indicate a requirement which must be strictly followed and from which no deviation is permitted if conformance to this document is to be claimed.
+
+The keywords "is recommended" indicate a requirement which is recommended but which is not absolutely required. Thus this requirement need not be present to claim conformance.
+
+The keywords "is not recommended" indicate a requirement which is not recommended but which is not specifically prohibited. Thus, conformance with this specification can still be claimed even if this requirement is present.
+
+The keywords "can optionally" indicate an optional requirement which is permissible, without implying any sense of being recommended. This term is not intended to imply that the vendor's implementation must provide the option and the feature can be optionally enabled by the network
+
+operator or service provider. Rather, it means the vendor may optionally provide the feature and still claim conformance with the specification.
+
+# 6 Introduction
+
+## 6.1 Motivation for unified management of CDNs
+
+Nowadays there are many kinds of CDN operator in the network, including specific service providers who provide CDN rental service for Internet content, and traditional telecom operators with self-built CDN for their self-own services or third parties' services. There are also some operators who build and operate CDNs in different regions of the network independently.
+
+Different CDNs (owned by one or multiple operators) provide content services for users in their own independent domains, and the drawbacks of lacking interconnection between them are as follows:
+
+- the content inside a CDN is only enjoyed by users in CDN's own domain, and such content cannot be shared by other users by cross-domain mechanisms, which leads to insufficient resource utilization;
+- in an overloading or bandwidth-constrained scenario, one independent CDN cannot realize the best load balance without dispatching users' requests across domains;
+- for an operator who is short of content inside his own CDN, it takes time and endeavour to introduce Internet content one content provider (CP) by CP, so that the operator cannot maximize the benefits of the investment in a short time.
+
+This Recommendation discusses unified management of multiple CDNs, which aims to provide a technical solution of a CDN manager above CDNs and interconnections among CDNs, by introducing capabilities of content synchronization, user request routing, and other related unified management functionalities, to build up a global CDN.
+
+The CDN described in this Recommendation follows the capabilities of content delivery identified in [ITU-T Y.2019].
+
+Figure 1 illustrates the basic scheme of unified management of CDNs.
+
+
+
+Y.2305(18)\_F01
+
+Figure 1: Basic scheme of unified management of CDNs. The diagram shows a central 'CDN manager' at the top, connected by dashed arrows to three separate CDN clouds labeled 'CDN A', 'CDN B', and 'CDN C'. Each CDN cloud contains three server icons. Below these, a horizontal dashed line separates the CDNs from a group of 'User' icons. Arrows point from each of the three CDN clouds down to their respective groups of users. The user groups are: three users under CDN A, five users under CDN B, and five users under CDN C. The text 'Y.2305(18)\_F01' is located at the bottom right of the diagram area.
+
+**Figure 1 – Basic scheme of unified management of CDNs**
+
+NOTE – The CDNs in Figure 1 can be attributed to one or more operators. The CDN manager can be attributed to one operator that operates one or more CDNs or can be attributed to a third party that does not operate any CDN.
+
+## 6.2 Scenarios for unified management of CDNs
+
+### 6.2.1 Content synchronization between CDNs
+
+Figure 2 shows the scenario for content synchronization among CDNs.
+
+
+
+The diagram illustrates the scenario of content synchronization between CDNs. It shows a Content provider at the top left, which injects content into CDN A (represented by a cloud containing three server icons). A dashed arrow labeled 'Content injection' points from the Content provider to CDN A. Above the CDNs is a CDN manager, represented by a stack of server icons, which has dashed arrows pointing to both CDN A and CDN B. A solid arrow labeled 'Content synchronization' points from CDN A to CDN B. Below each CDN is a User icon, with a double-headed vertical arrow connecting each user to their respective CDN. The identifier 'Y.2305(18)\_F02' is located at the bottom right of the diagram.
+
+Diagram illustrating the scenario of content synchronization between CDNs.
+
+**Figure 2 – Scenario of content synchronization between CDNs**
+
+In the scenario of content synchronization between CDNs, first, the CP injects its new content into CDN A to which it subscribes. Second, under the synchronization control of the CDN manager, CDN A duplicates and transfers this content to CDN B, and then a user in the domain of CDN B can effectively access the new content.
+
+### 6.2.2 Request routing under dispatch control of CDN manager
+
+Figure 3 shows a scenario for request routing under the dispatch control of the CDN manager.
+
+
+
+The diagram shows a Content provider at the top left, with an arrow labeled 'Content injection' pointing to a cloud labeled 'CDN A'. Above 'CDN A' is a cloud labeled 'CDN manager'. A dashed arrow labeled 'Request interaction' points from the 'CDN manager' to a 'User' icon at the bottom. Another dashed arrow labeled 'Request interaction' points from the 'User' to a cloud labeled 'CDN B'. A solid arrow labeled 'Content interaction' points from 'CDN A' to the 'User'. The 'CDN manager' cloud contains three server icons, and both 'CDN A' and 'CDN B' clouds also contain three server icons each.
+
+Diagram illustrating the scenario for request routing under the dispatch control of the CDN manager. A Content provider injects content into CDN A. A User sends a request to CDN B, which is then redirected to CDN A under the control of the CDN manager. The CDN manager also interacts with the User via request interaction.
+
+Y.2305(18)\_F03
+
+**Figure 3 – Scenario for request routing under the dispatch control of the CDN manager**
+
+In this scenario, first, a CP injects its new contents into CDN A, but these contents are not synchronized to CDN B. Second, when a user in the CDN B domain sends a request for these new contents to CDN B, the request is redirected to CDN A, under the dispatch control of the CDN manager, to obtain the contents the user requests.
+
+# 7 Requirements for unified management of CDNs
+
+## 7.1 Request routing
+
+A CDN manager is required to route end user content requests globally among several CDNs. The features of global request routing include:
+
+- routing end user content requests to the destination cache server in one CDN according to the traffic control policy pre-defined in the CDN manager;
+
+NOTE – Traffic control policy can allow, for example, the allocation of network resources or steering of traffic concerning the load of cache servers and CDNs, location, time and a service level agreement (SLA) agreed by CPs.
+
+- supporting mechanisms of both domain name system (DNS) canonical name (CNAME) and uniform resource locator (URL) forward processes to route end user content requests.
+
+## 7.2 Routing policy management
+
+- A CDN manager is required to support the following kinds of routing policies:
+ - dispatching requests according to the domain name or destination Internet protocol (IP) address in a user request and being supportive of routing requests with a particular domain name to a particular CDN system;
+ - dispatching requests according to the source IP address of a user and being supportive of routing requests with a particular source IP address (segment) to a particular CDN system;
+
+- the CDN manager is required to support a default policy, that all the requests are routed to a particular CDN;
+- the CDN manager is required to support a general policy for abnormal scenarios, when the CDN manager loses control of a CDN or if a CDN breaks down, all requests are routed to another CDN;
+- the CDN manager is required to manage policies according to operational requirements.
+
+## **7.3 Requirements for CDN status management**
+
+The CDN manager is required to actively monitor the online or offline status of a dispatch subsystem and cache servers in CDN periodically and map the information to the general status of availability of the CDN.
+
+## **7.4 Requirements for content storage metadata management**
+
+- The CDN manager is required to create a new content storage metadata when a CP injects new content into a CDN.
+- The CDN manager is required to update the content storage metadata when content is synchronized between different CDNs.
+- The CDN manager is required to provide content storage metadata according to requests from the CDN.
+- The CDN manager is required to delete the content storage metadata when content is deleted in all CDNs.
+
+NOTE – Content storage metadata includes a set of information about the content stored in CDNs, including identifier (e.g., domain name, hash value), location (e.g., CDN A)
+
+## **7.5 Requirements of network management**
+
+A CDN manager is required to support network-related management capabilities with the following aspects:
+
+- receiving service logs generated by cache servers and dispatch sub-systems in a CDN;
+- receiving service performance reports from the CDN and generating a global key performance indicator (KPI) report to a CP by domain granularity;
+- receiving equipment performance report from the CDN;
+- monitoring alarm status of the CDN.
+
+## **7.6 Requirements of charging**
+
+A CDN manager is required to support charging features that include the following aspects:
+
+- charging policy management and enforcement;
+- generating data records according to charging policies or traffic or content properties (content type, size, encoding, bitrates and application-specific parameters, such as video resolution and frame rate).
+
+NOTE 1 – Traffic flows may have different charging rates, e.g., some flows from a particular CP may be free of charge, while other traffic flows are charged at normal rates.
+
+NOTE 2 – If user traffic was routed to a cache server deployed in a CDN, it is the cache server's responsibility to generate the traffic data records and interact with the CDN manager for effective charging record generation.
+
+NOTE 3 – "Traffic data records" in this Recommendation are charging records according to the charging policy and traffic parameters, while "charging data record" is a specific term used for charging of communication or traffic. To avoid confusion, the term traffic data record is used in this Recommendation.
+
+NOTE 4 – Traffic data records do not contain any private user data.
+
+# 8 Mechanisms for unified management of CDNs
+
+## 8.1 Framework for unified management of CDNs
+
+Figure 4 shows the framework for unified management of CDNs:
+
+
+
+The diagram illustrates the framework for unified management of CDNs. A Content provider application server is connected to a CDN manager. The CDN manager is a central component containing five modules: Content management, System management, Status management, Dispatch control, and Access control. The CDN manager is connected to two CDNs, CDN A and CDN B. CDN A is connected to the End user. A dotted line indicates a candidate connection from CDN B to the End user. The diagram is labeled Y.2305(18)\_F04.
+
+Figure 4: Framework for unified management of CDNs. The diagram shows a Content provider application server connected to a CDN manager. The CDN manager contains modules for Content management, System management, Status management, Dispatch control, and Access control. The CDN manager is connected to CDN A and CDN B. CDN A is connected to the End user. A dotted line indicates a candidate connection from CDN B to the End user.
+
+**Figure 4 – Framework for unified management of CDNs**
+
+NOTE – The lines between the end user, CDN A and CDN B indicate that the end user is able to send content requests and receive the content from CDN A and CDN B. The continuous line means CDN A is primary for the end user. The dotted line means CDN B is a candidate for the end user.
+
+In this framework, the CDN manager plays a key role in unified management of CDNs, in which the modules described in clauses 8.1.1 to 8.1.5 are identified.
+
+### 8.1.1 Content management
+
+This module creates, provides, processes and synchronizes the information of content in CDNs, with the following specific functionalities:
+
+- receiving the creation request from the CP's application server (AS) when new content is injected into a CDN;
+- creating content storage metadata according to the creation request, which includes what the content's name is and which CDN it is stored in;
+- receiving the updating request from CDNs when the content is synchronized between them;
+- updating content storage metadata according to the updating request;
+- receiving the deletion request from a CDN when content is removed;
+- deleting content storage metadata according to the deletion request;
+- receiving the enquiry request from a CDN;
+- providing content storage metadata to a CDN according to the enquiry request.
+
+### 8.1.2 Status management
+
+This module receives, provides, processes and synchronizes the status of CDNs, with the following specific functionalities:
+
+- updating online or offline status of a CDN, including online or offline status of dispatch subsystem and cache servers in this CDN;
+- mapping online or offline status of a CDN to this CDN's general status of availability;
+- receiving the enquiry request of a CDN availability status from other CDNs;
+
+- providing the required CDN availability status according to the enquiry request.
+
+### **8.1.3 Dispatch control**
+
+This module routes content requests from an end user, with the following specific functionalities:
+
+- receiving the content request from an end user;
+- providing the destination CDN to end users according to the content request from end users.
+
+### **8.1.4 Access control**
+
+This module provides the capability for IP access control to enable the CDN manager to be connected with external legal CDNs, with the following functionalities:
+
+- transmitting data packages from certificated CDNs and end users in the access control list (ACL);
+- supporting creation, reading, updating and deletion of the ACL.
+
+### **8.1.5 System management**
+
+This module is in charge of routing policy management, network-related management and generation of charging information, with the following functionalities:
+
+- supporting creation, reading, updating and deletion of routing policies;
+- receiving service logs and equipment performance report from CDNs;
+- monitoring alarm status of CDNs;
+- generating a global KPI report in the service domain;
+- generating charging information according to the KPI report;
+- providing the KPI report and charging information to the CP AS.
+
+## 8.2 Procedures of unified management on CDNs
+
+### 8.2.1 Content management
+
+
+
+The diagram illustrates the procedures for content management involving four entities: CDN A, CDN B, Content provider AS, and CDN manager. The process is divided into two main phases: 1. New content injection and 2. Content synchronization between CDNs.
+
+**1. New content injection:**
+
+- 1.1. Injecting content: Content provider AS sends content to CDN B.
+- 1.2. Reporting content storage information: Content provider AS reports to the CDN manager.
+- 1.3. Creating content storage metadata: The CDN manager creates metadata.
+
+**2. Content synchronization between CDNs:**
+
+- 2.1. Content requirement detection: CDN B detects a requirement.
+- 2.2. Request to inquire content storage metadata: CDN B requests metadata from the CDN manager.
+- 2.3. Content storage metadata: The CDN manager provides metadata to CDN B.
+- 2.4. Content request: CDN B requests content from CDN A.
+- 2.5. Content synchronization: CDN A synchronizes content with CDN B.
+- 2.6. Request to update content storage metadata: CDN B requests metadata update from the CDN manager.
+- 2.7. Updating content storage metadata: The CDN manager updates metadata.
+
+Y.2305(18)\_F05
+
+Sequence diagram showing content management procedures between CDN A, CDN B, Content provider AS, and CDN manager.
+
+**Figure 5 – Procedures for content management**
+
+#### **i New content injection**
+
+**i.1** A CP injects new content into a CDN.
+
+**i.2** The CP reports the descriptive information of what the content name is and which CDN it is stored in to the CDN manager.
+
+**i.3** The CDN manager creates the content storage metadata according to the report from the CP.
+
+#### **ii Content synchronization between CDNs**
+
+**ii.1** CDN B detects some content that is very popular, but not stored locally, and generates a requirement for this content.
+
+**ii.2** CDN B sends a content storage metadata request to CDN manager.
+
+**ii.3** The CDN manager responds to CDN B with the requested metadata, which indicates the content is stored in CDN A.
+
+**ii.4** CDN B resolves the metadata and sends the request to CDN A to get the content.
+
+**ii.5** CDN A transfers the content to CDN B.
+
+**ii.6** CDN B reports the descriptive information of what the content name is and which CDN it is stored in to the CDN manager.
+
+**ii.7** The CDN manager creates the content storage metadata according to the report from CDN B.
+
+### 8.2.2 Status management
+
+
+
+```
+
+sequenceDiagram
+ participant A as CDN A
+ participant B as CDN B
+ participant M as CDN manager
+
+ Note over A, B, M: 1. Global status management
+ A->>M: 1.1. Reporting status information
+ B->>M: 1.2. Reporting status information
+ M->>M: 1.3. Creating CDNs' availability status
+ M->>B: 1.4. Providing global availability status
+ M->>A: 1.5. Providing global availability status
+
+ Note over A, B, M: 2. Active detection of status
+ M->>B: 2.1. Detect CDN B's status
+ B->>M: 2.2. Providing CDN B's status information
+ M->>M: 2.3. Creating CDN B's availability status
+
+ Note over A, B, M: 3. Inquired status management
+ B->>M: 3.1. Requesting CDN A's status
+ M->>B: 3.2. Providing CDN A's availability status
+
+```
+
+Y.2305(18)\_F06
+
+Sequence diagram illustrating the procedure for status management between CDN A, CDN B, and the CDN manager. The diagram is divided into three main phases: 1. Global status management, 2. Active detection of status, and 3. Inquired status management. In the first phase, both CDNs report status to the manager, which then provides global availability status back to both. In the second phase, the manager detects CDN B's status and provides it back to CDN B. In the third phase, CDN B requests CDN A's status from the manager, which provides it back to CDN B.
+
+**Figure 6 – Procedure for status management**
+
+#### **i Global status management**
+
+- i.1** CDN A reports the online/offline status to the CDN manager periodically.
+- i.2** CDN B reports the online/offline status to the CDN manager periodically
+- i.3** The CDN manager maps the online/offline status of each CDN to the general status of availability of this CDN, and creates the global availability status of all CDNs.
+- i.4** The CDN manager provides the global availability status to CDN A.
+- i.5** The CDN manager provides the global availability status to CDN B.
+
+#### **ii Active detection of status**
+
+- ii.1** The CDN manager detects the online/offline status of CDN B.
+- ii.2** CDN B replies with the status information to the CDN manager.
+- ii.3** The CDN manager maps the status of CDN B to general status of availability of this CDN.
+
+#### **iii Enquired status management**
+
+- iii.1** CDN B sends an availability status of CDN A request to the CDN manager.
+- iii.2** The CDN manager provides the availability status of CDN A to CDN B.
+
+### 8.2.3 Request routing
+
+
+
+```
+
+sequenceDiagram
+ participant End user
+ participant CDN A
+ participant CDN manager
+ participant CDN B
+
+ Note left of End user: 1. Request routing (direct way)
+ End user->>CDN A: 1.1. Requesting content
+ CDN A->>CDN manager: 1.2. Redirecting to CDN Manager
+ End user->>CDN manager: 1.3. Requesting content
+ Note right of CDN manager: 1.4. Searching content storage metadata
+ Note right of CDN manager: 1.5. Availability status detection
+ CDN manager-->>CDN B: 1.5. Availability status detection
+ CDN manager-->>End user: 1.6. Providing destination IP
+ End user->>CDN B: 1.7. Requesting content
+ CDN B-->>End user: 1.8. Providing content
+
+ Note left of End user: 2. Request routing (indirect way)
+ End user->>CDN A: 2.1. Requesting content
+ CDN A->>CDN manager: 2.2. Requesting content
+ Note right of CDN manager: 2.3. Searching content storage metadata
+ Note right of CDN manager: 2.4. Availability status detection
+ CDN manager-->>CDN B: 2.4. Availability status detection
+ CDN manager-->>CDN A: 2.5. Providing content storage metadata
+ CDN A-->>End user: 2.6. Providing destination IP
+ End user->>CDN B: 2.7. Requesting content
+ CDN B-->>End user: 2.8. Providing content
+
+```
+
+Y.2305(18)\_F07
+
+Sequence diagram illustrating the procedure of request routing between End user, CDN A, CDN manager, and CDN B. The diagram is divided into two sections: 1. Request routing (direct way) and 2. Request routing (indirect way).
+
+**Figure 7 – Procedure of request routing**
+
+#### **i Request routing (direct way)**
+
+- i.1** An end user requests access to the content in CDN A.
+- i.2** CDN A does not store the requested content, and redirects the end user to the CDN manager.
+- i.3** The end user sends the content request to the CDN manager.
+- i.4** The CDN manager searches the content storage metadata and finds out the content is stored in CDN B.
+- i.5** The CDN manager actively detects the availability status of CDN B (see 8.2.2-ii).
+- i.6** The CDN manager provides the destination IP address (where the requested content is stored in CDN B) to the end user.
+- i.7** The end user sends a request for the content to CDN B.
+- i.8** CDN B responds with the content to the end user.
+
+#### **ii Request routing (indirect way)**
+
+- ii.1** An end user requests access to the content in CDN A.
+- ii.2** CDN A does not store the requested content, but requests the content storage metadata from the CDN manager.
+
+- ii.3** The CDN manager searches the content storage metadata and discovers that the content is stored in CDN B.
+- ii.4** The CDN manager actively detects the availability status of CDN B (see 8.2.2-ii).
+- ii.5** The CDN manager provides the content storage metadata to CDN A.
+- ii.6** CDN A resolves the metadata and replies with the destination IP address to the end user.
+- ii.7** The end user sends a request for the content to CDN B. **ii.8** CDN B responds with the content to the end user.
+
+# **9 Security considerations for unified management of CDNs**
+
+The security considerations for unified CDNs management are aligned with the content delivery functional architecture security requirements of the next generation network (NGN) according to [ITU-T Y.2019], with the following additions:
+
+- the CDN manager is required to provide security mechanisms for managed CDNs that are authorized and authenticated legally, avoiding connexion to any CDN from a third party;
+- the CDN manager is required to provide protected ACLs to prevent tampering or hacking by illegal parties;
+- the CDN manager is required to provide secure authentication and authorization mechanisms for CPs who sign a SLA with the operator of the CDN manager.
+
+## Appendix I
+
+### Use cases of unified management of CDNs
+
+(This appendix does not form an integral part of this Recommendation.)
+
+### I.1 Use case I: Control capability 1 – content sharing
+
+Content caching has gained rapid growth of interest as a solution to improve content accessibility and quality of service (QoS) as well as to accelerate responses to user requests. Traditionally, CPs deploy lots of servers in the datacentres as fixed content delivery networks (FCDNs), to improve the experience for fixed network users, which attracts CPs to inject their content into FCDNs.
+
+The fast development of smart phones and pads means that users now often watch videos on these smart terminals. Recently, telecom carriers have established mobile content delivery networks (MCDNs) on which content cache servers are deployed, such as radio access networks (RANs) or an evolved packet core (EPC), to improve experience for mobile users.
+
+Subject to the storage volume of the servers deployed in mobile networks, content with highest popularity should be placed on cache servers in RANs or an EPC, while, content with low popularity should be placed on cache servers deployed in the FCDNs. Therefore, the CDN manager should provide the capability to implement content sharing between different CDNs.
+
+NOTE – Content popularity (which may depend on not only content itself, but also the profiles of the viewers) can be determined by the frequency of the user requests and the review duration of the contents. Therefore, user mobility may cause the content in the cache to change frequently, resulting in inefficiency in content caching. Therefore, the data analytics function needs to analyse the data related to both content and users in order to accurately determine or predict content popularity.
+
+Figure I.1 depicts content sharing between different CDNs.
+
+
+
+The diagram illustrates a network architecture for content sharing. At the top, a 'CDN manager' (represented by a cluster of server icons) is connected via numbered paths to two main blocks: 'MCDN' (Mobile CDN) on the left and 'FCDN' (Fixed CDN) on the right.
+
+The MCDN block contains mobile base stations (antennas), routers, and servers. A 'User' icon with a mobile device is shown moving between base stations.
+
+The FCDN block contains a 'Cache server' cluster and a router.
+
+Numbered arrows indicate the flow of control and data:
+
+
+- 1: From MCDN to CDN manager.
+- 2: From CDN manager to FCDN.
+- 3: Data transfer from FCDN cache server to MCDN server.
+- 4: From MCDN to CDN manager (triggered by user movement).
+- 5: From CDN manager to FCDN.
+- 6: Data transfer from FCDN cache server to a new MCDN server.
+
+ The diagram is labeled 'Y.2305(18)\_FI.1' at the bottom right.
+
+Diagram showing content sharing between MCDN and FCDN managed by a CDN manager.
+
+**Figure I.1 – Content sharing between different CDNs**
+
+- i.1 Lots of mobile users watch videos on mobile networks. The MCDN notifies the CDN manager to transfer the content from the FCDN.
+- i.2 The CDN manager requests the FCDN to transfer the content.
+- i.3 The FCDN transfers the content to the related server deployed in the MCDN.
+- i.4 When the MCDN notices that users have moved to another base station, then the MCDN requests the CDN manager to transfer content to the new server.
+- i.5 The CDN manager requests the FCDN to transfer the content.
+- i.6 The FCDN transfers the content to the new server deployed in the MCDN.
+
+**I.2 Use case II: Control capability 2 – request routing (direct way)**
+
+If a user wants to access contents stored in a certain CDN, the CDN manager provides a direct solution to route the user DNS request to the appropriate cache server in this CDN.
+
+Figure I.2 shows a specific case of request routing (direct way) under the control of the CDN manager.
+
+14 Rec. ITU-T Y.2305 (05/2018)
+
+
+
+The diagram illustrates the direct way of request routing under the control of a CDN manager. It shows the following components and their interactions:
+
+- Content provider (CP):** Represented by a server icon with an upload/download arrow. It lists files: `logo.jpg`, `background.mp3`, `index.html`, and `...`.
+- CDN manager:** Represented by a stack of server icons in a blue oval.
+- CDN A:** Represented by a stack of server icons in a grey cloud.
+- CDN B:** Represented by a stack of server icons in a grey cloud.
+- User (Domain B):** Represented by a stick figure icon.
+
+The process is numbered 1 through 5:
+
+1. Dashed arrow from CP to CDN manager.
+2. Solid arrow from CP to CDN A.
+3. Dashed arrow from User to CDN B.
+4. Dashed arrow from CDN B to CDN manager.
+5. Solid arrow from CDN manager to CDN A.
+
+Y.2305(18)\_FI.2
+
+Diagram illustrating request routing (direct way) under the control of the CDN manager. The diagram shows a Content provider (CP) interacting with a CDN manager and two CDNs (CDN A and CDN B). A User (Domain B) sends a request to CDN B, which redirects it to the CDN manager, which then routes it to CDN A. The process is numbered 1 through 5.
+
+**Figure I.2 – Request routing (direct way) under the control of the CDN manager**
+
+The following is the specific process.
+
+- 1 When the CP is ready to inject its new content (e.g., `newLogo.png`) into CDN A (provided by the operator), it interacts with the CDN manager to get the permission to inject contents into CDN A.
+- 2 If it is allowed, the CP injects new content into CDN A;
+- 3 A user (who is in the domain of CDN B) in the operator's network requests the “`newLogo.png`” (e.g., whose domain name is “`xxx.com`”) of the CP. The user sends a DNS request (for the resolution of `xxx.com`) to CDN B. CDN B detects that the target content is not stored locally and redirects this request to the CDN manager (by responding to the user to resend it to the CDN manager).
+- 4 The user resends the DNS request (for the resolution of `xxx.com`) to the CDN manager. The CDN manager detects the requested content (`newLogo.png` with a domain name `xxx.com`) is stored in CDN A, and responds with CDN A as the request's destination to the user.
+- 5 The user sends the DNS request (for the resolution of `xxx.com`) to CDN A, and after a series of processes inside CDN, finally gets the `newLogo.png` from a suitable cache server.
+
+### **I.3 Use case III: Control capability 2 – request routing (indirect way)**
+
+In contrast to use case II, in this case, the CDN manager does not participate in the user requesting routing activity. The request of the user (who is in the domain of CDN B) is directly routed by CDN B to the CDN A cache server that stores the target content, according to the content storage metadata and availability status of CDN A provided by the CDN manager.
+
+Figure I.3 shows a specific case of request routing (indirect way) under the control of the CDN manager.
+
+
+
+The diagram illustrates the request routing process. A Content provider (CP) is shown on the left, sending content (logo.jpg, background.mp3, index.html, ...) to CDN A. The CDN manager is at the top, receiving requests from the CP (1) and responding (2). The CDN manager also receives requests from CDN B (4) and responds (5). The user (Domain B) sends a request to CDN B (3) and receives a response from CDN A (6).
+
+Diagram illustrating request routing (indirect way) under the control of the CDN manager. The diagram shows a Content provider (CP) interacting with a CDN manager and two CDNs (CDN A and CDN B). The CP sends content (logo.jpg, background.mp3, index.html, ...) to CDN A. The CDN manager receives requests from the CP (1) and responds (2). The CDN manager also receives requests from CDN B (4) and responds (5). The user (Domain B) sends a request to CDN B (3) and receives a response from CDN A (6).
+
+**Figure I.3 – Request routing (indirect way) under the control of the CDN manager**
+
+The following is the specific process.
+
+- 1 When the CP is ready to inject its new content (e.g., newLogo.png) into CDN A (provided by the operator), it interacts with the CDN manager to get the permission to inject contents into CDN A.
+- 2 If it is allowed, the CP injects new content into CDN A.
+- 3 A user (who is in the domain of CDN B) requests the newLogo.png (e.g., whose domain name is xxx.com) of the CP. The user sends a DNS request (for the resolution of xxx.com) to CDN B.
+- 4 CDN B addresses this content storage metadata request to the CDN manager. The CDN manager detects the content is in CDN A and responds with the content storage metadata (identifier and location of the content included) and the availability status of CDN A to CDN B.
+- 5 CDN B examines the content storage metadata and status. If CDN A is available, CDN B responds with CDN A as the request's destination to the user.
+- 6 The user sends the DNS request (for the resolution of xxx.com) to CDN A, and after a series of processes inside CDN, finally gets the newLogo.png from a suitable cache server.
+
+### **I.4 Use case IV: Management capability**
+
+In this use case, the CDN manager receives operational information both from CPs and CDNs, which are intended to be managed globally by the CDN manager.
+
+Figure I.4 shows interactions between the CP, CDN manager and CDN.
+
+
+
+Y.2305(18)\_Fl.4
+
+Diagram illustrating interactions between a Content provider, a CDN manager, and a CDN. The Content provider (CP) sends content identifications (A.1) to the CDN manager and receives KPIs (A.2) in return. The CDN manager sends service performance reports (B.1) to the CDN, receives alarm status (B.2), service logs (B.3), and online/offline status (B.4) from the CDN. The CDN is represented by a cloud icon containing server icons.
+
+**Figure I.4 – Interactions between the content provider, CDN manager and CDN**
+
+The following are specific items with examples provided by each part.
+
+- Between CP and CDN manager:
+ - A.1: The CDN manager receives content identifications and their locations from a CP.
+For example, if CP A injects new content (with domain name xxx.com) into CDN A, it will report this domain name (xxx.com) as an identification, and content location (CDN A) to the CDN manager.
+ - A.2: The CDN manager provides KPIs to a CP by domain granularity.
+For example, contents with domain name xxx.com have already stored in a CDN that is managed by the CDN manager, and the CDN manager provides indicators of xxx.co' to the CP according to its requirements.
+
+| Domain name | Request times | Success rate | ... |
+|----------------|---------------|--------------|-----|
+| xxx.com | 132,65 | 96.3% | ... |
+| ... | ... | ... | ... |
+
+- Between CDN and the CDN manager:
+ - B.1: The CDN manager receives a service performance report from the CDN.
+For example, the CDN reports operation and service information regularly to the CDN manager.
+
+| Key | Value |
+|-------------------------------|---------------|
+| CDN Name | CDN A |
+| Service Traffic Volume | 96,236,863 GB |
+| Source Traffic Volume | 612,963 GB |
+| Hit Rate | 83% |
+| ... | ... |
+
+- B.2: The CDN manager receives an alarm status from the CDN.
+For example, in particular conditions, such as one cache server's utilization ratio of hardware reaching the alarm line (90%), the CDN reports related information to the CDN manager, to avoid further content injection into this server.
+- B.3: The CDN manager receives service logs from the CDN.
+For example, CDNs collect service logs generated by cache servers and upload them to the CDN manager.
+- B.4: The CDN manager receives the online/offline status from the CDN.
+For example, the CDN manager detects heartbeat messages from the CDN to determine whether the CDN is alive.
+
+## **Appendix II**
+
+### **Introduction of a DNS CNAME and URL forwarding mechanism**
+
+(This appendix does not form an integral part of this Recommendation.)
+
+### **II.1 DNS CNAME**
+
+CNAME records can be used to alias one name to another [b-IETF RFC 2219].
+
+For example, if a content/service provider owns a server with IP address 10.1.1.1, it might normally be accessed through "xxx.com" (DNS A record). This provider may also want to access it through "yyy.com". One way is to add a CNAME record that points "yyy.com" to "xxx.com". During a visit to "yyy.com", a user will see the exact same content as "xxx.com".
+
+DNS CNAME has the following advantages:
+
+- several CNAMEs can point to one DNS A record;
+- when an IP address is changed, the provider just needs to change the DNS A record accordingly, without changing any CNAME.
+
+### **II.2 URL forwarding**
+
+URL forwarding allows a provider to redirect, or "point", its domain name to a URL [b-IETF RFC 7231]. This is useful when the provider wants multiple domain names to go to the same website, or make use of an existing website.
+
+# Bibliography
+
+- [b-ITU-T H.760] Recommendation ITU-T H.760 (2009), *Overview of multimedia application frameworks for IPTV services.*
+- [b-ITU-T H.780] Recommendation ITU-T H.780 (2012), *Digital signage: Service requirements and IPTV based architecture.*
+- [b-ITU-T M.1400] Recommendation ITU-T M.1400 (2015), *Designations for interconnections among operators' networks.*
+- [b-ITU-T Q.825] Recommendation ITU-T Q.825 (1998), *Specification of TMN applications at the Q3 interface: Call detail recording.*
+- [b-ITU-T Y.1910] Recommendation ITU-T Y.1910 (2008), *IPTV functional architecture.*
+- [b-ITU-T Y.2091] Recommendation ITU-T Y.2091 (2011), *Terms and definitions for next generation networks.*
+- [b-IETF RFC 2219] IETF RFC 2219 (1997), *Use of DNS aliases for network services.*
+- [b-IETF RFC 7231] IETF RFC 7231 (2014), *Hypertext transfer protocol (HTTP/1.1): Semantics and content.*
+
+
+
+
+
+## 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 |
+| 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 | 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 |
\ No newline at end of file
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@@ -0,0 +1,819 @@
+
+
+# ITU-T
+
+TELECOMMUNICATION
+STANDARDIZATION SECTOR
+OF ITU
+
+# Y.3108
+
+(12/2019)
+
+SERIES Y: GLOBAL INFORMATION
+INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS,
+NEXT-GENERATION NETWORKS, INTERNET OF
+THINGS AND SMART CITIES
+
+Future networks
+
+# --- Capability exposure function in IMT-2020 networks
+
+Recommendation ITU-T Y.3108
+
+## ITU-T Y-SERIES RECOMMENDATIONS
+
+# GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS, NEXT-GENERATION NETWORKS, INTERNET OF THINGS AND SMART CITIES
+
+| | |
+|--------------------------------------------------------------------|----------------------|
+| GLOBAL INFORMATION INFRASTRUCTURE | |
+| General | Y.100–Y.199 |
+| Services, applications and middleware | Y.200–Y.299 |
+| Network aspects | Y.300–Y.399 |
+| Interfaces and protocols | Y.400–Y.499 |
+| Numbering, addressing and naming | Y.500–Y.599 |
+| Operation, administration and maintenance | Y.600–Y.699 |
+| Security | Y.700–Y.799 |
+| Performances | Y.800–Y.899 |
+| INTERNET PROTOCOL ASPECTS | |
+| General | Y.1000–Y.1099 |
+| Services and applications | Y.1100–Y.1199 |
+| Architecture, access, network capabilities and resource management | Y.1200–Y.1299 |
+| Transport | Y.1300–Y.1399 |
+| Interworking | Y.1400–Y.1499 |
+| Quality of service and network performance | Y.1500–Y.1599 |
+| Signalling | Y.1600–Y.1699 |
+| Operation, administration and maintenance | Y.1700–Y.1799 |
+| Charging | Y.1800–Y.1899 |
+| IPTV over NGN | Y.1900–Y.1999 |
+| NEXT GENERATION NETWORKS | |
+| Frameworks and functional architecture models | Y.2000–Y.2099 |
+| Quality of Service and performance | Y.2100–Y.2199 |
+| Service aspects: Service capabilities and service architecture | Y.2200–Y.2249 |
+| Service aspects: Interoperability of services and networks in NGN | Y.2250–Y.2299 |
+| Enhancements to NGN | Y.2300–Y.2399 |
+| Network management | Y.2400–Y.2499 |
+| Network control architectures and protocols | Y.2500–Y.2599 |
+| Packet-based Networks | Y.2600–Y.2699 |
+| Security | Y.2700–Y.2799 |
+| Generalized mobility | Y.2800–Y.2899 |
+| Carrier grade open environment | Y.2900–Y.2999 |
+| FUTURE NETWORKS | Y.3000–Y.3499 |
+| CLOUD COMPUTING | Y.3500–Y.3999 |
+| INTERNET OF THINGS AND SMART CITIES AND COMMUNITIES | |
+| General | Y.4000–Y.4049 |
+| Definitions and terminologies | Y.4050–Y.4099 |
+| Requirements and use cases | Y.4100–Y.4249 |
+| Infrastructure, connectivity and networks | Y.4250–Y.4399 |
+| Frameworks, architectures and protocols | Y.4400–Y.4549 |
+| Services, applications, computation and data processing | Y.4550–Y.4699 |
+| Management, control and performance | Y.4700–Y.4799 |
+| Identification and security | Y.4800–Y.4899 |
+| Evaluation and assessment | Y.4900–Y.4999 |
+
+*For further details, please refer to the list of ITU-T Recommendations.*
+
+# Recommendation ITU-T Y.3108
+
+# Capability exposure function in IMT-2020 networks
+
+## Summary
+
+Recommendation ITU-T Y.3108 specifies the design principles, architecture and reference points of the capability exposure function (CEF) in International Mobile Telecommunication 2020 (IMT-2020) networks.
+
+Recommendation ITU-T Y.3108 specifies exposed capabilities brought by network softwarization and the architecture of IMT-2020 and functionalities that support the capability exposure of IMT-2020.
+
+## History
+
+| Edition | Recommendation | Approval | Study Group | Unique ID* |
+|---------|----------------|------------|-------------|---------------------------------------------------------------------------|
+| 1.0 | ITU-T Y.3108 | 2019-12-14 | 13 | 11.1002/1000/14129 |
+
+## Keywords
+
+5G, IMT-2020, capability exposure function, CEF.
+
+---
+
+\* To access the Recommendation, type the URL in the address field of your web browser, followed by the Recommendation's unique ID. For example, .
+
+## 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 .
+
+© ITU 2020
+
+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 | Definition..... | 1 |
+| | 3.1 Terms defined elsewhere..... | 1 |
+| | 3.2 Terms defined in this Recommendation..... | 2 |
+| 4 | Abbreviations and acronyms ..... | 2 |
+| 5 | Conventions ..... | 3 |
+| 6 | Design principles of the capability exposure function in IMT-2020 networks..... | 3 |
+| 7 | Framework of the capability exposure function ..... | 4 |
+| | 7.1 General aspects..... | 4 |
+| | 7.2 Exposure of network capabilities ..... | 5 |
+| 8 | Capability exposure function functionalities and reference points..... | 6 |
+| | 8.1 Capability exposure function functional architecture..... | 6 |
+| | 8.2 Capability exposure function reference points ..... | 6 |
+| 9 | Procedures for the exposure of network capabilities..... | 7 |
+| | 9.1 General aspects of the capability exposure procedure ..... | 7 |
+| | 9.3 Edge-computing exposure procedure ..... | 11 |
+| | 9.4 Network data analytics exposure procedure..... | 12 |
+| | 9.5 Fixed and mobile convergence exposure procedure ..... | 12 |
+| | 9.6 Customization of QoS capability exposure procedure ..... | 13 |
+| | 10 Security considerations ..... | 14 |
+| | Bibliography..... | 15 |
+
+
+
+# Recommendation ITU-T Y.3108
+
+# Capability exposure function in IMT-2020 networks
+
+## 1 Scope
+
+This Recommendation specifies the design principles, functional architecture and reference points of the capability exposure function (CEF) in International Mobile Telecommunication 2020 (IMT-2020) networks.
+
+## 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 Y.3101] Recommendation ITU-T Y.3101 (2018), *Requirements of the IMT-2020 network*.
+- [ITU-T Y.3102] Recommendation ITU-T Y.3102 (2018), *Framework of the IMT-2020 network*.
+- [ITU-T Y.3104] Recommendation ITU-T Y.3104 (2018), *Architecture of the IMT-2020 network*.
+- [ITU-T Y.3105] Recommendation ITU-T Y.3105 (2018), *Requirements of capability exposure in the IMT-2020 network*.
+- [ITU-T Y.3110] Recommendation ITU-T Y.3110 (2017), *IMT-2020 network management and orchestration requirements*.
+- [ITU-T Y.3111] Recommendation ITU-T Y.3111 (2017), *IMT-2020 network management and orchestration framework*.
+- [ITU-T Y.3131] Recommendation ITU-T Y.3131 (2019), *Functional architecture for supporting fixed mobile convergence in IMT-2020 networks*.
+
+## 3 Definition
+
+### 3.1 Terms defined elsewhere
+
+This Recommendation uses the following terms defined elsewhere:
+
+**3.1.1 control plane** [b-ITU-T Y.2011]: The set of functions that controls the operation of entities in the stratum or layer under consideration, plus the functions required to support this control.
+
+**3.1.2 IMT-2020** [b-ITU-T Y.3100]: Systems, system components, and related aspects that support to provide far more enhanced capabilities than those described in [b-ITU-R M.1645].
+
+NOTE – [b-ITU-R M.1645] defines the framework and overall objectives of the future development of IMT-2000 and systems beyond IMT-2000 for the radio access network.
+
+**3.1.3 network function** [b-ITU-T Y.3100]: In the context of IMT-2020, a processing function in a network.
+
+NOTE 1 – Network functions include but are not limited to network node functionalities, e.g., session management, mobility management and transport functions, whose functional behaviour and interfaces are defined.
+
+NOTE 2 – Network functions can be implemented on a dedicated hardware or as virtualized software functions.
+
+NOTE 3 – Network functions are not regarded as resources, but rather any network functions can be instantiated using the resources.
+
+**3.1.4 network slice** [b-ITU-T Y.3100]: A logical network that provides specific network capabilities and network characteristics.
+
+NOTE 1 – Network slices enable the creation of customized networks to provide flexible solutions for different market scenarios which have diverse requirements, with respect to functionalities, performance and resource allocation.
+
+NOTE 2 – A network slice may have the ability to expose its capabilities.
+
+NOTE 3 – The behaviour of a network slice is realized via network slice instance(s).
+
+**3.1.5 PDU session** [b-ITU-T Y.3100]: In the context of IMT-2020, an association between a user equipment (UE) and a data network that provides a protocol data unit (PDU) connectivity service.
+
+NOTE – The type of the association includes IP type, non-IP type and Ethernet type.
+
+**3.1.6 third party (3rd party)** [b-ITU-T.Y.3100]: In the context of IMT-2020, with respect to a given network operator and network end-users, an entity which consumes network capabilities and/or provides applications and/or services.
+
+NOTE 1 – An example of 3rd party, a virtual network operator (VNO) may use capabilities exposed by a network operator, e.g., to manage specific network slices. Another example of 3rd party, a service and/or application provider (e.g., an over the top (OTT) player) may provide applications and/or services to enhance the network capabilities.
+
+NOTE 2 – Network end-users are not regarded as 3rd parties.
+
+### **3.2 Terms defined in this Recommendation**
+
+None.
+
+## **4 Abbreviations and acronyms**
+
+This Recommendation uses the following abbreviations and acronyms:
+
+| | |
+|----------|---------------------------------------------|
+| AF | Application Function |
+| AN | Access Network |
+| API | Application Programming Interface |
+| AS | Application Server |
+| ASF | Authentication Server Function |
+| CEF | Capability Exposure Function |
+| CN | Core Network |
+| CP | Control Plane |
+| EC | Edge Computing |
+| FMC | Fixed and Mobile Convergence |
+| HTTP | Hypertext Transfer Protocol |
+| ID | Identifier |
+| IMT-2020 | International Mobile Telecommunication 2020 |
+| NACF | Network Access Control Function |
+| NF | Network Function |
+
+| | |
+|------|----------------------------------|
+| NFR | Network Function Repository |
+| NSSF | Network Slice Selection Function |
+| NWDA | Network Data Analytics |
+| OTT | Over The Top |
+| PCF | Policy Control Function |
+| PDU | Protocol Data Unit |
+| RP | Reference Point |
+| QoS | Quality of Service |
+| REST | Representational State Transfer |
+| SLA | Service Level Agreement |
+| SMF | Session Management Function |
+| UE | User Equipment |
+| UPF | User Plane Function |
+| USM | Unified Subscription Management |
+| UNIC | Unified Network Integrated Cloud |
+| V2X | Vehicle to Everything |
+| VNF | Virtual Network Function |
+| VNO | Virtual Network Operator |
+
+## 5 Conventions
+
+In this Recommendation:
+
+The keywords "is required to" indicate a requirement which must be strictly followed and from which no deviation is permitted, if conformance to this Recommendation is to be claimed.
+
+The keywords "is recommended" indicate a requirement which is recommended but which is not absolutely required. Thus, this requirement need not be present to claim conformance.
+
+## 6 Design principles of the capability exposure function in IMT-2020 networks
+
+Based on requirements identified in [ITU-T Y.3101], [ITU-T Y.3105] and other relevant studies, the following principles and characteristics are considered for the design of the CEF in IMT-2020 networks:
+
+- the architectural design of the CEF should be flexible to adapt to the changes in third party applications and core network (CN) functions;
+- the exposure of the IMT-2020 capabilities relies on the architecture of the CEF providing interaction between the IMT-2020 network and third parties;
+- the architectural design of the CEF should support a unified northbound interface to facilitate easy invocation of the CEF by third party applications.
+
+Key network capabilities that are expected to be exposed include, but are not limited to [ITU-T Y.3105]:
+
+- network slicing management;
+- edge computing (EC);
+
+- network data analytics (NWDA);
+- fixed and mobile convergence (FMC);
+- quality of service (QoS).
+
+**7 Framework of the capability exposure function**
+**7.1 General aspects**
+
+This clause describes the framework of the CEF and provides an overview of its role in IMT-2020 networks.
+
+Based on the architecture of an IMT-2020 network [ITU-T Y.3104], Figure 7-1 shows the framework of the CEF, and its interaction with third party applications, NWDA, network management and orchestration, and other IMT-2020 network functions (NFs).
+
+
+
+The diagram illustrates the IMT-2020 network architecture. At the top are two blocks: 'Network management and orchestration' and 'Network data analytics', connected by a double-headed arrow. Below them is the 'Core network (CN)' containing various functions: CEF (highlighted in orange), NFR, PCF, USM, AF, NACF, NSSF, ASF, and SMF. These are divided into a 'Control plane' and a 'User plane'. The 'User plane' includes the UPF. To the left is 'User Equip. (UE)' and 'Access network (AN)'. To the right is a 'Third-party application' containing an AF and an AS (within a DN cloud). Various reference points (RP-em, RP-ed, RP-ea, RP-tn, RP-an, RP-su, RP-au, RP-ud) connect these components. Solid blue lines indicate control plane interactions, while white arrows indicate data transport.
+
+Figure 7-1 – Framework of capability exposure function in the IMT-2020 network
+
+ASF: authentication server function; NFR: network function repository; NSSF: network slice selection function; UPF: user plane function
+
+**Figure 7-1 – Framework of capability exposure function in the IMT-2020 network**
+
+CEF is a control plane (CP) NF that provides functionalities for NFs to expose their capabilities as a service to third parties in the IMT-2020 network [ITU-T Y.3102].
+
+A third party's application can be logically divided into two parts: application server (AS) and application function (AF). The AS interacts with the IMT-2020 network in the user plane, and executes the service logic of an application. The AF interacts with the IMT-2020 network in the CP to exchange configuration information. For example, the AF can provide session-related information to a policy control function (PCF) (directly or via CEF) so that a session management function (SMF) can finally use this information for session management.
+
+NOTE – AFs considered to be trusted by the operator can be allowed to interact directly with relevant NFs. AFs not allowed to access directly the NFs are required to use CEF to interact with relevant NFs. This Recommendation focuses on the second scenario.
+
+4 Rec. ITU-T Y.3108 (12/2019)
+
+NWDA [ITU-T Y.3105] comprise an NF that provides operator-managed network analytics capabilities. NWDA support data collection from NFs, AFs and network management and orchestration, as well as supporting analytics information provisioning to NFs and the AF.
+
+Network management and orchestration [ITU-T Y.3111] is a network subsystem for managing and orchestrating virtual network functions (VNFs) and other software components. More detail is specified in [ITU-T Y.3111].
+
+Other CP NFs (e.g., SMF, network access control function (NACF), PCF) that support capability exposure are specified in [ITU-T Y.3104].
+
+All the interactions between the CEF and other CP NFs (including the AF) are realized by service-based interfaces as specified in [ITU-T Y.3104].
+
+The CEF has three distinct interfaces with: third party applications; network management and orchestration; and NWDA capabilities.
+
+- Interface with a third-party application: the CEF can expose specific UE events and network status-related information to the AF of a third party to support the optimization of that party's application. The CEF can collect data from the AF of a third party for NWDA and network configuration.
+- Interface with network management and orchestration: the CEF can deliver network management requirements of the third party to network management and orchestration, in supporting the customization of network slicing and mobile EC.
+- Interface with NWDA capabilities: the CEF can forward collected data from the AF of a third party to NWDA, from which it obtains network status information that can be exposed to that party.
+
+The CEF also needs to interact with other CN functions (e.g., SMF, NACF or PCF), to obtain information about the UE (e.g., reachability, location or roaming status) and network (e.g., status information or congestion level).
+
+### **7.2 Exposure of network capabilities**
+
+#### **7.2.1 Exposure of control plane capabilities**
+
+The CEF supports exposure of the control plane capabilities of the IMT-2020 network to third parties with the following functionalities.
+
+- a) Monitoring of network events
+The CEF exposes interfaces for the authorized third party to monitor specific network events (e.g., roaming of UE, communication failure, UE location, UE connectivity status) mainly triggered by NACF and unified subscription management (USM) operations [ITU-T Y.3102]. The CEF maintains the subscription of a third party to notification of network events and notifies that party when one occurs.
+- b) Provisioning of information by a third party
+The CEF exposes interfaces for the authorized third party to provision the parameters for network configuration, UE communication configuration, and service-specific configuration (e.g., UE mobility patterns, communication characteristics) maintained by USM [ITU-T Y.3102]. On request by the third party, the CEF requests USM to update the provisioned configuration parameters.
+
+NOTE – The update of network configuration parameters can cause operational changes in other NFs.
+
+#### **7.2.2 Exposure of network management and orchestration capabilities**
+
+In terms of interaction with the CEF, network management and orchestration capabilities [ITU-T Y.3110] expose a set of management data required by the customer and authorized by the
+
+network operator. For example, network operation status and current network performance can be exposed to third parties through the CEF within operator's policy.
+
+#### 7.2.3 Exposure of network data analytics capabilities
+
+The NWDA capabilities provide network analytics information (e.g., network load level information and network slice QoE data analytics) to application and services via CEF functionalities.
+
+## 8 Capability exposure function functionalities and reference points
+
+Clause 8.1 describes the CEF functionalities; while clause 8.2 describes CEF reference points (internal to CEF and external to the network capabilities to be exposed).
+
+### 8.1 Capability exposure function functional architecture
+
+Figure 8-1 depicts the architecture of the CEF.
+
+
+
+The diagram illustrates the functional architecture of the Capability Exposure Function (CEF). At the top is a yellow box labeled "Third party's AF". Below it is a large box labeled "Capability exposure function" which contains four sub-boxes: "Authorization and validation", "Collection", "Translation", and "Exposure". At the bottom are three boxes: "Network management and orchestration", "Network data analytics", and "Other CN NFs". Arrows indicate the flow of information: a single upward arrow from the CEF to the Third party's AF, and a single downward arrow from the Third party's AF to the CEF. Between the CEF and the bottom boxes, there are pairs of arrows (one upward, one downward) for each of the three bottom boxes, indicating bidirectional communication.
+
+Y.3108(19)\_F8-1
+
+Functional architecture of the capability exposure function diagram
+
+**Figure 8-1 – Functional architecture of the capability exposure function**
+
+The CEF may include the following functionalities.
+
+- Exposure: the CEF supports secured exposure to an authorized third party of network information, which is collected from IMT-2020 NFs and translated by the translation functionality.
+- Collection: the CEF retrieves and stores network information as structured data using standardized interfaces with network management and orchestration [ITU-T Y.3110], network analytics capabilities and other core NFs.
+- Authorization and validation: the CEF supports secure access of a third party to the exposed CEF interfaces, e.g., for monitoring and provisioning of network information.
+- Translation: the CEF translates between information exchanged with third parties and that with NFs. As an example, the translation from service level agreement (SLA) requirements to specific network parameters.
+
+The CEF handles masking of network and user sensitive information from external applications according to the network policy.
+
+### 8.2 Capability exposure function reference points
+
+The NFs within the CN CP interact using service-based interfaces. These service interfaces can be implemented by common protocols such as the hypertext transfer protocol (HTTP) 2.0 and RESTful application programming interfaces (APIs). The details of service-based interfaces lie outside the scope of this Recommendation.
+
+The following reference points (RPs) are defined in the framework of capabilities exposure function:
+
+- RP-ea: between the CEF and third party's AF;
+- RP-em: between the CEF and the network management and orchestration;
+- RP-ed: between the CEF and NWDA.
+
+## 9 Procedures for the exposure of network capabilities
+
+### 9.1 General aspects of the capability exposure procedure
+
+This clause describes general procedures to provide each of the basic network services specified in clause 7.1 of [ITU-T Y.3105] for capability exposure services: authentication and authorization of third parties; facilitation of authorized third party subscription to and notification of a specific event concerning changes in exposed network information; and facilitation of authorized third parties to provision configuration parameters of the IMT-2020 network.
+
+#### 9.1.1 Authentication and authorization of third parties
+
+See Figure 9-1.
+
+
+
+```
+
+sequenceDiagram
+ participant TP as The third party
+ participant CEF as Capability exposure function
+ TP->>CEF: 1. Authorization request
+ CEF->>TP: 2. Validation of the authentication of the third party
+ CEF-->>TP: 3. Authorization response
+
+```
+
+The diagram is a sequence diagram illustrating the procedure for third party authorization and authentication. It involves two main entities: 'The third party' and 'Capability exposure function'. The process follows three steps: 1. 'The third party' sends an 'Authorization request' to the 'Capability exposure function'. 2. The 'Capability exposure function' sends a response labeled '2. Validation of the authentication of the third party' back to 'The third party'. 3. Finally, the 'Capability exposure function' sends an 'Authorization response' back to 'The third party'.
+
+Sequence diagram showing the procedure for third party authorization and authentication between 'The third party' and 'Capability exposure function'.
+
+**Figure 9-1 – Procedure for third party authorization and authentication**
+
+- 1) The third party sends an authorization request to the CEF to obtain permission to access a specific network capability by including the third-party identity information and any other information required for authentication of that party.
+- 2) The CEF validates the authentication of the third party (using authentication information) and checks whether the third party is permitted to access the requested network capability.
+- 3) Based on the third-party subscription information, authorization information for access by the third party is sent to that party as an authorization response.
+
+#### 9.1.2 Subscription and notification of network event monitoring
+
+Specific network events, such as loss of UE network connectivity, UE roaming and communication failure, can be monitored by the CEF and notified to the third party on occurrence. The CEF provides exposed interfaces to support the subscription to and notification of network events by monitoring them in the NACF and USM.
+
+Figure 9-2 depicts the detailed procedure.
+
+
+
+```
+
+sequenceDiagram
+ participant TP as Third party
+ participant CEF
+ participant NF as NACF or USM
+
+ TP->>CEF: 1. Network event subscription request
+ activate CEF
+ CEF->>CEF: 2. Authorization check
+ CEF->>NF: 3. Network event subscription request
+ NF-->>CEF: 4. Network event subscription response
+ deactivate NF
+ CEF-->>TP: 5. Network event subscription response
+ deactivate CEF
+ NF->>CEF: 6. Network event notification
+ activate CEF
+ CEF->>CEF: 7. Translation
+ CEF-->>TP: 8. Network event notification
+ deactivate CEF
+
+```
+
+Y.3108(19)\_F9-2
+
+Sequence diagram showing the procedure for subscription and notification of network event monitoring between Third party, CEF, and NACF or USM.
+
+**Figure 9-2 – Procedure for subscription and notification of network event monitoring**
+
+- 1) The third party (application) subscribes to the network event by sending a network event subscription request to the CEF, specifying the target event(s), which may include loss of UE network connectivity, UE roaming status or communication failure.
+- 2) The CEF checks whether the third party is authorized for the request. If not, the procedure proceeds to step 5).
+- 3) The CEF subscribes the target event(s) to the corresponding NF (NACF or USM) by sending a network event subscription request.
+- 4) The corresponding NF (NACF or USM) registers and maintains the association of the target monitoring event and the CEF to be notified; and the NF acknowledges the subscription by sending a network event subscription response to the CEF.
+- 5) The CEF registers and maintains the association of the target monitoring event and the target third party to be notified; and the CEF acknowledges the subscription by sending a network event subscription response to the third party. If authorization fails, the CEF responds indicating the authorization failure and the procedure ends at this step.
+- 6) When the corresponding NF detects that a target monitoring event occurred, the NF notifies it to the target CEF by sending a network event notification.
+- 7) The CEF translates the internal network information by masking it from the external use.
+- 8) The CEF notifies the monitoring event to the target third party by sending a network event notification.
+
+NOTE – The subscription and notification procedure can be used for one-time retrieval of network information from the third party.
+
+#### 9.1.3 Provisioning of configuration parameters
+
+The operations of the CP NFs of an IMT-2020 network can be customized by third parties by provisioning the configuration parameters for network configuration, UE communication configuration and service-specific configuration, such as UE mobility patterns, communication characteristics and QoS parameters.
+
+The CEF provides exposed interfaces to support the provisioning of configuration parameters by updating the target configuration parameters in USM.
+
+Figure 9-3 depicts the detailed procedure.
+
+
+
+```
+
+sequenceDiagram
+ participant TP as Third party
+ participant CEF
+ participant USM
+
+ TP->>CEF: 1. Configuration parameter update request
+ Note over CEF: 2. Authorization check
+ CEF->>USM: 3. Configuration parameter update request
+ USM-->>CEF: 4. Configuration parameter update response
+ CEF-->>TP: 5. Configuration parameter update response
+
+```
+
+Y.3108(19)\_F9-3
+
+Sequence diagram for Figure 9-3: Procedure for provisioning of configuration parameters. The diagram shows three lifelines: Third party, CEF, and USM. 1. Third party sends '1. Configuration parameter update request' to CEF. 2. CEF performs an internal '2. Authorization check'. 3. CEF sends '3. Configuration parameter update request' to USM. 4. USM sends '4. Configuration parameter update response' to CEF. 5. CEF sends '5. Configuration parameter update response' to Third party. Reference: Y.3108(19)\_F9-3
+
+**Figure 9-3 – Procedure for provisioning of configuration parameters**
+
+- 1) The third party (application) sends a configuration parameter update request to the CEF, specifying the target parameter(s), which may include network configuration, UE communication configuration and service-specific configuration.
+- 2) The CEF checks whether the third party is authorized for the request. If not, the procedure proceeds to step 5).
+- 3) The CEF sends a target configuration parameter(s) update request to the USM.
+- 4) The USM updates the given configuration parameter(s) in its repository and responds by sending a configuration parameter update response to the CEF.
+- 5) The CEF sends a configuration parameter update response to the third party. If authorization fails, the CEF responds, indicating the authorization failure.
+
+### 9.2 Network slice management capability exposure procedure
+
+#### 9.2.1 Creation of a network slice
+
+This clause describes general procedures to provide each of the basic network services specified in clause 7.2 of [ITU-T Y.3105] for network slice management.
+
+See Figure 9-4.
+
+
+
+```
+
+sequenceDiagram
+ participant TP as The third party
+ participant CEF as Capability exposure function
+ participant NMO as Network management and orchestration
+
+ TP->>CEF: 1. Slice create request
+ Note over CEF: 2. Authorization check
+ CEF->>NMO: 3. Slice create request
+ Note over NMO: 4. Slice creation and identifier allocation
+ NMO-->>CEF: 5. Slice create response
+ CEF-->>TP: 6. Slice create response
+
+```
+
+Y.3108(19)\_F9-4
+
+Sequence diagram for Figure 9-4: Procedure for network slice management capability exposure – creation of a network slice. The diagram shows three lifelines: The third party, Capability exposure function, and Network management and orchestration. 1. The third party sends '1. Slice create request' to Capability exposure function. 2. Capability exposure function performs an internal '2. Authorization check'. 3. Capability exposure function sends '3. Slice create request' to Network management and orchestration. 4. Network management and orchestration performs an internal '4. Slice creation and identifier allocation'. 5. Network management and orchestration sends '5. Slice create response' to Capability exposure function. 6. Capability exposure function sends '6. Slice create response' to The third party. Reference: Y.3108(19)\_F9-4
+
+**Figure 9-4 – Procedure for network slice management capability exposure – creation of a network slice**
+
+- 1) The third party AF applies for the creation of a new network slice. The functional and performance requirements of the network slice are carried in the slice create request message.
+- 2) The CEF performs a validation and authorization check: the CEF authorizes the third party request.
+- 3) After step 2), the CEF transfers the network slice creation request to network management and orchestration [ITU-T Y.3110].
+- 4) Based on resource availability and operator policy, network management and orchestration decides whether the network slice creation request is accepted. If the request is accepted, network management and orchestration creates the customized network slice for the third party (application) and allocates the identifier (ID) for this slice.
+- 5) Network management and orchestration sends a response to the CEF. The network slice ID and information is delivered if the network slice is created.
+- 6) The CEF forwards the network management and orchestration response to the third party.
+
+#### 9.2.2 Modification of a network slice
+
+See Figure 9-5.
+
+
+
+```
+
+sequenceDiagram
+ participant TP as The third party
+ participant CEF as Capability exposure function
+ participant NMO as Network management and orchestration
+
+ TP->>CEF: 1. Slice modification request
+ Note over CEF: 2. Authorization check
+ CEF->>NMO: 3. Slice modification request
+ Note over NMO: 4. Slice modification and resource reallocation
+ NMO->>CEF: 5. Slice modification response
+ CEF->>TP: 6. Slice modification response
+
+```
+
+The diagram illustrates the procedure for network slice modification. It involves three main entities: The third party, Capability exposure function (CEF), and Network management and orchestration (NMO). The process follows these steps: 1. The third party sends a 'Slice modification request' to the CEF. 2. The CEF performs an 'Authorization check'. 3. The CEF sends the 'Slice modification request' to the NMO. 4. The NMO performs 'Slice modification and resource reallocation'. 5. The NMO sends a 'Slice modification response' back to the CEF. 6. The CEF forwards the 'Slice modification response' to the third party.
+
+Sequence diagram for network slice modification procedure
+
+Y.3108(19)\_F9-5
+
+**Figure 9-5 – Procedure for network slice management capability exposure – modification of a network slice**
+
+- 1) The third party (application) indicates the functional and performance requirements of the network slice in the request message.
+- 2) The CEF performs a validation and authorization check: CEF authorizes the third-party request.
+- 3) After step 2), the CEF transfers the network slice modification request to network management and orchestration [ITU-T Y.3110]. It also considers the network slice sharing scenario and determine the network parameters and resources related to modification of the non-sharing part.
+- 4) Network management and orchestration determine whether the network slice modification-related resources are allowed (according to the configuration for this third party) and, if allowed, update all network resources which have been determined in step 3).
+- 5) The network management and orchestration notifies the CEF whether the resource request is granted.
+- 6) If it is granted, the CEF notifies the third party of the result.
+
+#### 9.2.3 Deletion of a network slice
+
+See Figure 9-6.
+
+
+
+```
+
+sequenceDiagram
+ participant TP as The third party
+ participant CEF as Capability exposure function
+ participant NMO as Network management and orchestration
+
+ TP->>CEF: 1. Slice deletion request
+ activate CEF
+ CEF->>CEF: 2. Authorization check
+ deactivate CEF
+ CEF->>NMO: 3. Slice deletion request
+ activate NMO
+ NMO->>NMO: 4. Slice deletion and resource release
+ deactivate NMO
+ NMO->>CEF: 5. Slice deletion response
+ deactivate NMO
+ CEF->>TP: 6. Slice deletion response
+ deactivate CEF
+
+```
+
+Y.3108(19)\_F9-6
+
+Sequence diagram for Figure 9-6: Deletion of a network slice. The diagram shows three lifelines: 'The third party', 'Capability exposure function', and 'Network management and orchestration'. The process starts with 'The third party' sending a '1. Slice deletion request' to 'Capability exposure function'. 'Capability exposure function' then performs an internal action '2. Authorization check'. Next, 'Capability exposure function' sends a '3. Slice deletion request' to 'Network management and orchestration'. 'Network management and orchestration' performs an internal action '4. Slice deletion and resource release'. Then, 'Network management and orchestration' sends a '5. Slice deletion response' back to 'Capability exposure function'. Finally, 'Capability exposure function' sends a '6. Slice deletion response' back to 'The third party'.
+
+**Figure 9-6 –Deletion of a network slice**
+
+- 1) The third party (application) identifies the network slice to be deleted in a request message to the CEF.
+- 2) The CEF performs a third-party request validation related to the deletion: the CEF authorizes the third party request.
+- 3) After step 2, the CEF transfers the network slice deletion request to network management and orchestration [ITU-T Y.3110]. It also considers sharing network slices and determines the network parameters and resources related to deletion of non-sharing resources.
+- 4) Network management and orchestration determines whether the network slice deletion of the related resources is allowed (according to the configuration for this third party) and, if allowed, releases all network resources that have been determined in step 3).
+- 5) Network management and orchestration notifies the CEF whether the network slice deletion request has been granted.
+- 6) The CEF notifies the third party of the response.
+
+### 9.3 Edge-computing exposure procedure
+
+This clause describes general procedures to provide each of the basic network services specified in clause 7.3 of [ITU-T Y.3105] for EC.
+
+See Figure 9-7.
+
+
+
+```
+
+sequenceDiagram
+ participant TP as The third party
+ participant CEF as Capability exposure function
+ participant PCF as PCF/USM
+
+ TP->>CEF: 1. Traffic offload request
+ activate CEF
+ CEF->>CEF: 2. Authorization check
+ deactivate CEF
+ CEF->>PCF: 3. Traffic offload policy request
+ activate PCF
+ PCF->>PCF: 4. Trigger the policy of session management
+ deactivate PCF
+ PCF->>CEF: 5. Traffic offload policy response
+ deactivate PCF
+ CEF->>TP: 6. Traffic offload response
+ deactivate CEF
+
+```
+
+Y.3108(19)\_F9-7
+
+Sequence diagram for Figure 9-7: Procedure for the edge-computing capability exposure. The diagram shows three lifelines: 'The third party', 'Capability exposure function', and 'PCF/USM'. The process starts with 'The third party' sending a '1. Traffic offload request' to 'Capability exposure function'. 'Capability exposure function' then performs an internal action '2. Authorization check'. Next, 'Capability exposure function' sends a '3. Traffic offload policy request' to 'PCF/USM'. 'PCF/USM' performs an internal action '4. Trigger the policy of session management'. Then, 'PCF/USM' sends a '5. Traffic offload policy response' back to 'Capability exposure function'. Finally, 'Capability exposure function' sends a '6. Traffic offload response' back to 'The third party'.
+
+**Figure 9-7 – Procedure for the edge-computing capability exposure**
+
+- 1) According to the location of the UEs, service area of EC, and operator policy, the third party application sends a traffic offload request to CEF in order to re-route the UE traffic to EC. The request can target a specific UE or a group of UEs.
+- 2) The CEF checks whether the third party is authorized for the request. If not, the procedure proceeds to step 6).
+- 3) The CEF translates the information provided by the third party's AF into the information needed by the IMT-2020 NF (e.g., PCF or USM) and forwards the policy request to the targeting NFs.
+- 4) The NF (PCF or USM) can determine whether the existing PDU sessions are affected by the traffic-offloading policy in the AF request. For an affected PDU session, the PCF triggers the SMF for the PDU session modification procedure.
+- 5) The NF (PCF or USM) send a response to the CEF to update the result of policy enforcement.
+- 6) Based on the determination of the NF, the CEF sends a response to the third party for an UE application context update.
+
+### 9.4 Network data analytics exposure procedure
+
+This clause describes the procedures to provide each of the basic network services specified in clause 7.4 of [ITU-T Y.3105].
+
+See Figure 9-8.
+
+
+
+```
+
+sequenceDiagram
+ participant T as The third party
+ participant CEF as Capability exposure function
+ participant NDA as Network data analytics
+
+ T->>CEF: 1. Analytical data request
+ CEF->>CEF: 2. Authorization check
+ CEF->>NDA: 3. Data information request
+ NDA->>CEF: 4. Performing data analysis and determine policy
+ NDA->>CEF: 5. Data information response
+ CEF->>T: 6. Analytical data response
+
+```
+
+Y.3108(19)\_F9-8
+
+Sequence diagram for network data analytics exposure procedure showing interactions between The third party, Capability exposure function, and Network data analytics.
+
+**Figure 9-8 – Procedure for network data analytics exposure**
+
+- 1) The third party (e.g., automotive vehicle to everything (V2X) application) sends a network status information request to the CEF.
+- 2) The CEF authorizes the third party.
+- 3) After successful authorization, the CEF sends the data information request to NWDA.
+- 4) NWDA perform network data analysis based on the collected data from other NFs, e.g., third party information, network performance related information, network slice load level or QoS experience.
+- 5) The output of NWDA is delivered to the CEF via data information response.
+- 6) The CEF notifies the third party about the analytical data result.
+
+### 9.5 Fixed and mobile convergence exposure procedure
+
+This clause describes general procedures to provide each of the basic network services specified in clause 7.5 of [ITU-T Y.3105] for FMC.
+
+See Figure 9-9.
+
+
+
+```
+sequenceDiagram
+ participant TP as The third party
+ participant CEF as Capability exposure function
+ participant UNIC_CP as UNIC-CP
+ participant CE as Capability exposure
+
+ TP->>CEF: 1. AN types request
+ Note over CEF: 2. Authorization check
+ CEF->>UNIC_CP: 3. AN types request
+ UNIC_CP->>CEF: 4. AN types response
+ CEF->>TP: 5. AN types response
+```
+
+Y.3108(19)\_F9-9
+
+Sequence diagram showing the procedure for fixed and mobile convergence capability exposure between The third party, Capability exposure function, and UNIC-CP.
+
+**Figure 9-9 – Procedure for fixed and mobile convergence capability exposure**
+
+- 1) The third party (application) requests exposed network information by sending an access network (AN) type request to the CEF, specifying the target information that may also include UE location, UE connectivity status, UE reachability and network status.
+- 2) The CEF checks whether the third party is authorized for the request. If not, the procedure proceeds to step 5).
+- 3) The CEF sends an AN types request for the target information to the corresponding CEF in the unified network integrated cloud-control plane (UNIC-CP) [ITU-T Y.3131].
+- 4) The CEF in UNIC-CP [ITU-T Y.3131] responds with the exposed network information by sending an AN types response to the CEF.
+- 5) The CEF responds with the exposed network information by sending an AN type response to the third party. The third-party application can provide different services or contents based on the UE AN type.
+
+NOTE – The CEF in UNIC-CP [ITU-T Y.3131] enables the UNIC-CP to provide network capabilities and desensitized user data to applications through capability exposure interfaces.
+
+### 9.6 Customization of QoS capability exposure procedure
+
+This clause describes general procedures to provide each of the basic network services specified in clause 7.6 of [ITU-T Y.3105] for customization of QoS capabilities.
+
+See Figure 9-10.
+
+
+
+```
+
+sequenceDiagram
+ participant TP as The third party
+ participant CEF as Capability exposure function
+ participant PCF as PCF
+
+ TP->>CEF: 1. QoS request
+ activate CEF
+ CEF->>CEF: 2. Authorization check
+ CEF->>PCF: 3. QoS policy request
+ activate PCF
+ PCF-->>CEF: 4. QoS policy response
+ deactivate PCF
+ CEF-->>TP: 5. QoS response
+ deactivate CEF
+
+```
+
+Y.3108(19)\_F9-10
+
+Sequence diagram showing the procedure for a third party QoS request authorization and authentication. The diagram involves three entities: 'The third party', 'Capability exposure function', and 'PCF'. The process flow is: 1. 'The third party' sends a 'QoS request' to 'Capability exposure function'. 2. 'Capability exposure function' performs an 'Authorization check'. 3. 'Capability exposure function' sends a 'QoS policy request' to 'PCF'. 4. 'PCF' sends a 'QoS policy response' to 'Capability exposure function'. 5. 'Capability exposure function' sends a 'QoS response' to 'The third party'.
+
+**Figure 9-10 – Procedure for a third party QoS request authorization and authentication**
+
+- 1) The third party AF sends a QoS request message (e.g., UE ID, third party ID, SLA) to the CEF.
+- 2) The CEF authorizes the third party's QoS request and may apply policies to create or modify QoS flows for the third party.
+- 3) The CEF interacts with the PCF to notify it of the QoS request from a third party.
+- 4) The PCF analyses the requested QoS information provided by the CEF and determines whether a new QoS flow or modification to the existing QoS flow is required. The PCF may further interact with other NFs (e.g., SMF, USM) to implement the QoS configuration. The PCF notifies the CEF via a QoS policy response. If the requested QoS flow is accepted, the QoS parameters are delivered with the response.
+- 5) The CEF sends a QoS response message to the third party. If the requested QoS flow is accepted, the QoS parameters are delivered with the response.
+
+## 10 Security considerations
+
+The IMT-2020 network is subject to security and privacy measures. Sensitive information should be protected as a high priority in order to avoid leaking and unauthorized access. The security and privacy-related requirements specified in [ITU-T Y.3101] [ITU-T Y.3105] apply to this Recommendation.
+
+Specific security concerns related to the CEF are addressed in clause 9.
+
+## Bibliography
+
+- [b-ITU-T Y.2011] Recommendation ITU-T Y.2011 (2004), *General principles and general reference model for Next Generation Networks*.
+- [b-ITU-T Y.3100] Recommendation ITU-T Y.3100 (2017), *Terms and definitions for IMT-2020 network*.
+- [b-ITU-R M.1645] Recommendation ITU-R M.1645 (2003), *Framework and overall objectives of the future development of IMT-2000 and systems beyond IMT-2000*.
+
+
+
+
+
+## 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 |
+| 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 | 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 |
\ No newline at end of file
diff --git a/marked/Y/T-REC-Y.3138-202209-I_PDF-E/raw.md b/marked/Y/T-REC-Y.3138-202209-I_PDF-E/raw.md
new file mode 100644
index 0000000000000000000000000000000000000000..1efd9041b8874f8cf0b895de9ade4761ede52f81
--- /dev/null
+++ b/marked/Y/T-REC-Y.3138-202209-I_PDF-E/raw.md
@@ -0,0 +1,501 @@
+
+
+I n t e r n a t i o n a l T e l e c o m m u n i c a t i o n U n i o n
+
+# ITU-T
+
+TELECOMMUNICATION
+STANDARDIZATION SECTOR
+OF ITU
+
+# Y.3138
+
+(09/2022)
+
+SERIES Y: GLOBAL INFORMATION
+INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS,
+NEXT-GENERATION NETWORKS, INTERNET OF
+THINGS AND SMART CITIES
+
+Future networks
+
+# --- **Unified multiaccess edge computing for supporting fixed mobile convergence in IMT-2020 networks**
+
+Recommendation ITU-T Y.3138
+
+## ITU-T Y-SERIES RECOMMENDATIONS
+
+## GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS, NEXT-GENERATION NETWORKS, INTERNET OF THINGS AND SMART CITIES
+
+## GLOBAL INFORMATION INFRASTRUCTURE
+
+| | |
+|-------------------------------------------|-------------|
+| General | Y.100–Y.199 |
+| Services, applications and middleware | Y.200–Y.299 |
+| Network aspects | Y.300–Y.399 |
+| Interfaces and protocols | Y.400–Y.499 |
+| Numbering, addressing and naming | Y.500–Y.599 |
+| Operation, administration and maintenance | Y.600–Y.699 |
+| Security | Y.700–Y.799 |
+| Performances | Y.800–Y.899 |
+
+## INTERNET PROTOCOL ASPECTS
+
+| | |
+|--------------------------------------------------------------------|---------------|
+| General | Y.1000–Y.1099 |
+| Services and applications | Y.1100–Y.1199 |
+| Architecture, access, network capabilities and resource management | Y.1200–Y.1299 |
+| Transport | Y.1300–Y.1399 |
+| Interworking | Y.1400–Y.1499 |
+| Quality of service and network performance | Y.1500–Y.1599 |
+| Signalling | Y.1600–Y.1699 |
+| Operation, administration and maintenance | Y.1700–Y.1799 |
+| Charging | Y.1800–Y.1899 |
+| IPTV over NGN | Y.1900–Y.1999 |
+
+## NEXT GENERATION NETWORKS
+
+| | |
+|-------------------------------------------------------------------|---------------|
+| Frameworks and functional architecture models | Y.2000–Y.2099 |
+| Quality of Service and performance | Y.2100–Y.2199 |
+| Service aspects: Service capabilities and service architecture | Y.2200–Y.2249 |
+| Service aspects: Interoperability of services and networks in NGN | Y.2250–Y.2299 |
+| Enhancements to NGN | Y.2300–Y.2399 |
+| Network management | Y.2400–Y.2499 |
+| Computing power networks | Y.2500–Y.2599 |
+| Packet-based Networks | Y.2600–Y.2699 |
+| Security | Y.2700–Y.2799 |
+| Generalized mobility | Y.2800–Y.2899 |
+| Carrier grade open environment | Y.2900–Y.2999 |
+
+## **FUTURE NETWORKS**
+
+**Y.3000–Y.3499**
+
+### CLOUD COMPUTING
+
+Y.3500–Y.3599
+
+### BIG DATA
+
+Y.3600–Y.3799
+
+### QUANTUM KEY DISTRIBUTION NETWORKS
+
+Y.3800–Y.3999
+
+### INTERNET OF THINGS AND SMART CITIES AND COMMUNITIES
+
+| | |
+|---------------------------------------------------------|---------------|
+| General | Y.4000–Y.4049 |
+| Definitions and terminologies | Y.4050–Y.4099 |
+| Requirements and use cases | Y.4100–Y.4249 |
+| Infrastructure, connectivity and networks | Y.4250–Y.4399 |
+| Frameworks, architectures and protocols | Y.4400–Y.4549 |
+| Services, applications, computation and data processing | Y.4550–Y.4699 |
+| Management, control and performance | Y.4700–Y.4799 |
+| Identification and security | Y.4800–Y.4899 |
+| Evaluation and assessment | Y.4900–Y.4999 |
+
+For further details, please refer to the list of ITU-T Recommendations.
+
+## Recommendation ITU-T Y.3138
+
+# Unified multiaccess edge computing for supporting fixed mobile convergence in IMT-2020 networks
+
+## Summary
+
+A unified and cloud-based edge computing platform allows operators to flexibly deploy network functions and support infrastructure for fixed mobile convergence (FMC) to provide unified multiaccess edge computing capabilities for all access network technologies in IMT-2020 networks.
+
+Recommendation ITU-T Y.3138 specifies the requirements, architecture and functions of unified multiaccess edge computing for supporting FMC in networks.
+
+## History
+
+| Edition | Recommendation | Approval | Study Group | Unique ID* |
+|---------|----------------|------------|-------------|---------------------------------------------------------------------------|
+| 1.0 | ITU-T Y.3138 | 2022-09-29 | 13 | 11.1002/1000/15055 |
+
+## Keywords
+
+Fixed mobile convergence, IMT-2020 networks, unified edge computing.
+
+---
+
+\* To access the Recommendation, type the URL in the address field of your web browser, followed by the Recommendation's unique ID. For example, .
+
+## 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 .
+
+© ITU 2022
+
+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 | Conventions ..... | 3 |
+| 6 | Overview of unified multiaccess edge computing in IMT-2020 FMC networks..... | 3 |
+| 7 | Unified multiaccess edge computing requirements of FMC ..... | 4 |
+| | 7.1 Edge cloud-based network infrastructure..... | 4 |
+| | 7.2 Customizing the FMC network ..... | 4 |
+| | 7.3 Multi-access edge computing platform ..... | 4 |
+| | 7.4 Support of mobility..... | 5 |
+| | 7.5 Support of access network capability exposure..... | 5 |
+| | 7.6 Flexible routeing..... | 6 |
+| | 7.7 Multiaccess network collaboration..... | 6 |
+| 8 | Unified multiaccess edge computing architecture of FMC ..... | 6 |
+| | 8.1 MEP..... | 7 |
+| | 8.2 Edge management and orchestration..... | 9 |
+| 9 | Security considerations..... | 9 |
+| | Bibliography..... | 11 |
+
+
+
+## Recommendation ITU-T Y.3138
+
+# Unified multiaccess edge computing for supporting fixed mobile convergence in IMT-2020 networks
+
+## 1 Scope
+
+This Recommendation specifies the requirements, architecture and functions of unified multiaccess edge computing for supporting fixed mobile convergence (FMC), including security considerations; it discusses unified multiaccess edge computing capabilities for all access network technologies in IMT-2020 networks.
+
+## 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 Y.3101] Recommendation ITU-T Y.3101 (2018), *Requirements of the IMT-2020 network*.
+
+## 3 Definitions
+
+### 3.1 Terms defined elsewhere
+
+This Recommendation uses the following term defined elsewhere:
+
+**3.1.1 fixed mobile convergence** [b-ITU-T Y.3100]: In the context of IMT-2020, the capabilities that provide services and applications to end users regardless of the fixed or mobile access technologies being used and independently of the users' location.
+
+### 3.2 Terms defined in this Recommendation
+
+This Recommendation defines the following term:
+
+**3.2.1 unified multiaccess edge computing:** System which provides a unified and cloud-based edge computing platform, which allows operators to flexibly deploy network functions and support infrastructure for fixed mobile network convergence (FMC) and thereby to provide unified multiaccess edge computing capabilities for all access network technologies in IMT-2020 networks.
+
+NOTE – It conforms to the design considerations of the IMT-2020 FMC network, converged with regard to fixed access and mobile access, and interacts with the FMC network to provide collaborative capabilities and services. The management and orchestration functions of the unified multiaccess edge computing platform interact with the management and orchestration of the FMC network to achieve unified operation and maintenance.
+
+## 4 Abbreviations and acronyms
+
+This Recommendation uses the following abbreviations and acronyms:
+
+| | |
+|---------|-------------------------------------------------------------|
+| AI | Artificial Intelligence |
+| API | Application Program Interface |
+| APP | Application |
+| AR/VR | Augmented Reality / Virtual Reality |
+| CDN | Content Delivery Network |
+| CPU | Central Processing Unit |
+| DevOps | Development and Operations |
+| DNS | Domain Name System |
+| FMC | Fixed Mobile Convergence |
+| GPU | Graphic Processing Unit |
+| ICT | Information and Communication Technology |
+| ID | Identifier |
+| MEAO | Multiaccess Edge Computing Application Orchestration system |
+| MEC | Multiaccess Edge Computing |
+| MEP | Multiaccess Edge computing Platform |
+| ME-PAAS | Multiaccess Edge Platform As A Service |
+| MEPM | Multiaccess Edge computing Platform Management system |
+| ML | Machine Learning |
+| NFV | Network Function Virtualization |
+| NFVI | Network Function Virtualization Infrastructure |
+| NFVO | Network Function Virtualization Orchestrator |
+| NUMA | Non-Uniform Memory Access |
+| O&M | Operation and Maintenance |
+| OLT | Optical Line Terminal |
+| OTT | Over The Top |
+| PAAS | Platform As A Service |
+| PGW | Public data network Gateway |
+| PLMN | Public Land Mobile Network |
+| RNIS | Radio Network Information Service |
+| SDN | Software Defined Network |
+| SGW | Serving Gateway |
+| SLA | Service Level Agreement |
+| SR-IOV | Single Root Input/Output Virtualization |
+| TCP | Transmission Control Protocol |
+
+| | |
+|--------|----------------------------------------------------|
+| UE | User Equipment |
+| UHD | Ultra-High Definition |
+| UPF | User Plane Function |
+| vCPU | virtualized Central Processing Unit |
+| vBRAS | virtualized Broadband Access Server |
+| vCPE | virtualized Customer Premise Equipment |
+| VM | Virtualize Machine |
+| VNFM | Virtualized Network Function Manager |
+| vOLT | virtualized Optical Line Terminal |
+| vPGW-U | virtualized Packet Data Network Gateway User plane |
+| vSGW-U | virtualized Serving Gateway User plane |
+| WLAN | Wireless Local Area Network |
+
+## 5 Conventions
+
+In this Recommendation:
+
+The keywords "is required to" indicate a requirement which must be strictly followed and from which no deviation is permitted, if conformance to this Recommendation is to be claimed.
+
+The keywords "is recommended" indicate a specification which is recommended but which is not absolutely required. Thus, this specification need not be present to claim conformance.
+
+## 6 Overview of unified multiaccess edge computing in IMT-2020 FMC networks
+
+Multiaccess edge computing enables services to be hosted close to the UE's access point so as to achieve efficient service delivery through reduced end-to-end latency and load on the transport network, while providing edge services in a variety of ways.
+
+As a product of information and communication technology (ICT) convergence, a multiaccess edge computing platform can support network function virtualization deployment with cloud-based FMC architecture, such as a central unit, user plane function (UPF), virtualized serving gateway user plane (vSGW-U), virtualized packet data network (PDN) gateway user plane (vPGW-U), virtualized customer premise equipment (vCPE), virtualized broadband access server (vBRAS) and virtualized optical line terminal (vOLT). On the basis of cloud-based architecture, operators can open the storage, computing, network, and security capabilities of the edge computing platform to third-party application developers and content providers with application program interfaces (APIs) and provide over the top (OTT) applications with unified edge deployment and management. Furthermore, the multiaccess edge computing platform can abstract and encapsulate ICT network capabilities into a variety of services (for example, radio network information service (RNIS), location services, user equipment (UE) identifier, bandwidth management and transmission control protocol (TCP) optimization), and open them to third-party applications and vertical applications to improve the communications capabilities and performance of their services.
+
+A unified and cloud-based multiaccess edge computing platform allows operators to flexibly deploy network functions, and support the cloud-based infrastructure of FMC specified in [b-ITU-T Y.3131]. The infrastructure and service capabilities of the platform itself can help third-party applications to improve user experience, and maximize the value of both applications and networks.
+
+The unified multiaccess edge computing platform conforms to the design considerations of the IMT-2020 FMC network. The unified multiaccess edge computing platform is converged with regard to fixed access and mobile access, and interacts with the FMC network to provide collaborative capabilities and services. The management and orchestration functions of the unified multiaccess edge computing platform interact with the management and orchestration of the FMC network to achieve unified operation and maintenance.
+
+## **7 Unified multiaccess edge computing requirements of FMC**
+
+### **7.1 Edge cloud-based network infrastructure**
+
+The cloud-based network infrastructure is a set of interconnected multilayer data centres (e.g., edge data centres) with general purpose standardized hardware, centralized management and orchestration enabled by network function virtualization (NFV) and software defined network (SDN) technologies.
+
+- 1) It is required to support flexible and automatic network deployment, extension, scalability and life cycle management, which is expected to be deployed on cloud-based infrastructure as one of the IMT-2020 FMC network capabilities.
+- 2) It is required to support network functions to be designed and deployed in a cloud native way, such as the edge data centre.
+- 3) It is recommended to support a resource-saving mode, which can be achieved by temporarily disabling some management functions, as resources of the edge cloud are insufficient in some cases.
+- 4) It is recommended to support automatic disaster recovery with cloud-based technologies.
+
+### **7.2 Customizing the FMC network**
+
+As an important means of customizing the FMC network, the unified MEC can apply the following scenario-based implementation functions:
+
+- 1) It is required to provide users with customized access networks with multiple access options based on localized networks, such as 4G / 5G / wireless local area network (WLAN) / fixed broadband network.
+- 2) It is required to select the most appropriate access link for different services based on link capability, link status, user attributes and service requirements, and to perform handover between the access networks to guarantee service continuity and to improve user experience.
+- 3) It is required to provide access capability through fixed mobile converged UPF to achieve unified service bearer and unified user management in the IMT-2020 network.
+- 4) It is recommended to provide a customized policy control function and customized charging function for users.
+- 5) It is recommended to provide a network isolation capability for vertical industry users; in this way, a logically dedicated network can be deployed for different vertical industry users.
+- 6) It is recommended to apply artificial intelligence (AI) / machine learning (ML) technologies in customizing the FMC network; in this way, the automation and timeliness of service provision to users can be guaranteed.
+
+### **7.3 Multiaccess edge computing platform**
+
+As a computing platform on the edge of the FMC network, a multiaccess computing platform provides edge cache, content delivery network (CDN) and other edge network capabilities for the
+
+fixed and mobile converged network, implements MEC-based unified services and provides opportunities for cooperation with content providers.
+
+- 1) It is required to route the mobile user's service requests directly to the nearest fixed network exit. This is responsible for video cache content regeneration for services that have deployed CDN resources on the fixed network using the distributed features of the fixed network gateway.
+- 2) It is required to implement local services for fixed and mobile users, used as an edge node of a specific edge cache or service CDN.
+- 3) It is recommended to expose the edge cache and CDN capabilities to third-party applications through APIs.
+- 4) It is recommended to expose other edge network capabilities to third-party applications through APIs, such as network status information, user identifier, user location and bandwidth management.
+
+### **7.4 Support of mobility**
+
+Due to user or application mobility, service continuity and session continuity may be required based on the requirements of the service or the IMT-2020 FMC network.
+
+- 1) It is required to maintain connectivity between UE and an application (APP) instance when UE performs a handover to another network connection associated with the same MEC host.
+- 2) It is required to maintain connectivity between UE and an APP instance when UE performs a handover to another network connection not associated with the same MEC host.
+- 3) It is required to use available fixed and mobile network information to optimize the mobility procedures required to support service continuity and session continuity.
+- 4) It is required to use available user information to optimize the mobility procedures required to support service continuity and session continuity.
+- 5) It is required to perform location update if UE performs a handover, whether the new network connection is associated with the same MEC host or not.
+- 6) It is required to perform connection management for UE and APP on the basis of their mobility.
+
+### **7.5 Support of access network capability exposure**
+
+The IMT-2020 FMC network is required to provide access network information APIs to the MEC system; the need for MEC service that exposes up-to-date information regarding specific access network technology exists and the access network information is required to include:
+
+- 1) Access type, including 4G, 5G, WLAN, fixed broadband accesses, etc.
+- 2) Bidirectional bandwidth information delivered to/from the specific user.
+- 3) Granular bidirectional bandwidth information delivered to/from the specific user on the level of specific application, class of service, etc.
+- 4) Latency information, such as delays due to packet assembly in the network sublayer and queuing delays in the link sublayer.
+- 5) Access technology specific information, such as network identifiers, fixed link conditions and radio link conditions.
+- 6) Network conditions, such as congestion, overload and link failure.
+- 7) User subscription information, including current user subscription information and history user subscription information.
+
+- 8) Public land mobile network (PLMN) information, including the broadcast PLMN identifier (ID) and its access requirements.
+
+### **7.6 Flexible routing**
+
+In the IMT-2020 FMC network, the mobile access network and the fixed access network have their own advantages, and the advantages of different access networks can be exerted through the flexible routing feature of the MEC.
+
+- 1) It is recommended that the mobile access backhaul link be used to carry the fixed broadband access service, or the fixed broadband access network be used to share the pressure of 5G high throughput on the backhaul bandwidth of the mobile access network.
+
+### **7.7 Multiaccess network collaboration**
+
+In order to make full use of the service resources in each network, MEC can realize multiaccess network collaboration, decouple the access network and the backhaul network, and improve the user's service experience and network resource utilization.
+
+- 1) It is recommended that the user's service access request select an appropriate backhaul link according to the location, service bandwidth and speed of the service deployment.
+- 2) It is recommended that business applications based on multiaccess edge computing platforms serve users under different access networks at the same time, and ensure the same user's consistent experience under different access networks.
+
+## **8 Unified multiaccess edge computing architecture of FMC**
+
+The architecture design of unified multiaccess edge computing is based on the IMT-2020 FMC architecture. The unified multiaccess edge computing platform may reuse the NFV infrastructure and its management functionality of the FMC network, and make some enhancements to network functions and cloud-based architecture. The unified multiaccess edge computing platform is deployed at the edge of the IMT-2020 FMC core network, such as at the aggregation points, gateways, etc. The services and applications of edge computing are deployed at FMC unified multiaccess edge computing platform or at data centre.
+
+As shown in Figure 8-1, the architecture of unified MEC is based on the architecture of FMC in IMT-2020 networks, and consists of network function virtualization infrastructure (NFVI), multiaccess edge computing platform (MEP) and edge management and orchestration function. MEP includes multiaccess edge (ME) platform as a service (ME-PAAS), MEC network services, capability exposure function and MEC applications. On the basis of FMC networks, the unified MEC platform provides flexible capabilities (in the form of APIs) and services for developers to enable third-party applications and vertical industry service.
+
+
+
+The diagram illustrates the architecture of unified MEC in IMT-2020 FMC networks, organized into several layers and components:
+
+- TIC (Top Interconnectivity Core):**
+ - UNIC - CP (Unified Network Control Plane):**
+ - Common functionalities:** Authentication and authorization, Address allocation, Charging, Policy, Lawful interception, Mobility management, Session management, Capability exposure.
+ - Dedicated functionalities:**
+ - Cellular dedicated functionalities: MM, SM, QoS.
+ - WLAN dedicated functionalities: QoS.
+ - Fixed BB dedicated functionalities: QoS.
+- Management and orchestration:** Connected to UNIC - CP via **Umo** (Management and Orchestration interface).
+- Converged user data:** Connected to UNIC - CP via **Ud** (User Data interface).
+- MEP (Multi-Edge Platform):**
+ - Contains **ME-PAAS** (Multi-Edge Platform as a Service).
+ - Includes **Capability exposure layer** with **Network services** (LBS, RNIS, DNS, ...) and **Application** (vCDN, AI, Transcoding, ...).
+ - Supports various applications (APP1, APP2, APP3, ...).
+- Uc (User Plane Control):** Connects MEP to the User Plane.
+- UNIC - UP (Unified Network User Plane):**
+ - Contains **User plane for 5G, 4G, WLAN, and fixed BB**.
+- Service chain:** Includes Firewall, DPI, and other network functions.
+- NFVI (Network Function Virtualization Infrastructure):** The base layer supporting the service chain.
+- MEAO (Multi-Edge Access Orchestrator), MEPM (Multi-Edge Policy Manager), and VIM (Virtualized Infrastructure Manager):** External components interacting with the architecture.
+
+Reference: Y.3138(22)
+
+Architecture of unified MEC in IMT-2020 FMC networks diagram
+
+**Figure 8-1 – Architecture of unified MEC in IMT-2020 FMC networks**
+
+### 8.1 MEP
+
+#### 8.1.1 ME-PAAS
+
+Unified MEC in IMT-2020 FMC networks is required to provide platform as a service (PAAS) functions to ensure the quick integration of storage, computing, network and security capabilities, and to build up an ecosystem for operator's and third-party's services and applications. The ME-PAAS is required to support the following functions:
+
+- 1) **Virtualization compatibility:** ME-PAAS supports the unified orchestration and deployment of containers, supports bare metal containers and virtualize machine (VM) containers, and shields the difference of NFVI layers for services and applications.
+- 2) **Container management:** Secure containers are supported to provide security isolation for services and applications. Container images and templates are also supported to ensure software compatibility for services and applications.
+- 3) **Software management:** The ME-PAAS provides software repositories, supports security verification, version management, secure storage for container images and software packages, and supports deployment suites.
+
+NOTE – One example of a deployment suite is Helm.
+
+- 4) **DevOps capability:** ME-PAAS supports development and operations (DevOps) toolchains to provide an end-to-end development and verification environment for services and applications.
+- 5) **Optimization and acceleration**
+ - a) The PAAS platform provides different heterogeneous hardware acceleration capabilities for different MEC service scenarios. The capabilities include graphic processing units (GPU) acceleration, hardware encryption and decryption, hardware forwarding, high-speed storage and AI computing.
+
+- b) The PAAS platform supports container huge page tables, non-uniform memory access (NUMA) node binding, virtualized central processing unit (vCPU) and central processing unit (CPU) set binding, and single root input/output virtualization (SR-IOV) networking.
+
+##### **6) Micro services**
+
+- a) The PAAS platform provides basic service governance functions for services and applications, including service registration, service discovery, service release, service proxy and domain name system (DNS) functions.
+- b) For multi-instance and service offloading from services and applications, the PAAS platform supports load balancing, such as the load balancing and service chain.
+- c) The PAAS platform provides support for service and application reliability, meets fault tolerance and self-recovery service level agreement (SLA), and ensures automatic scaling of services and applications.
+- d) The PAAS platform provides basic platform capabilities for the quick integration of services and applications. It also provides various platform middleware, such as distributed messages, distributed transactions, distributed databases, distributed caches and API gateways, for different application scenarios.
+- e) For better service management, the PAAS platform is required to monitor and manage the performance status of services and applications, and accurately and effectively display service status.
+
+##### **7) O&M management**
+
+- a) In the unified MEC edge computing scenario, the PAAS platform is required to support centralized operation and maintenance (O&M) management, and collaborates with the multiaccess edge computing platform management system (MEPM) and multiaccess edge computing application orchestration system (MEAO) for unified O&M management.
+- b) To ensure the automated and centralized deployment of services and applications, the PAAS platform is required to support SDN network automation.
+- c) The multitenant management function is required. This supports sharing of the same system or program components in a multiuser environment while still ensuring data isolation between users.
+- d) The PAAS platform provides centralized software repository and unified software management to support O&M operations, such as centralized rollout, synchronization and upgrade of service and application software.
+- e) Layered O&M is required. The PAAS platform is required to monitor the basic load and status of services and applications, collect data and display the data in a unified manner.
+
+#### **8.1.2 MEC network service**
+
+An MEC network service is a service provided and deployed either by the MEC platform or an MEC application. When provided by an MEC application, it can be registered in the list of services to the MEC platform. The services of MEC platform include RNIS, location services, UE identifier, bandwidth management and TCP optimization, which can be categorized as MEC network services; while the services of MEC application include CDN, AI/ML, and transcoding, which can be categorized as MEC application services.
+
+#### **8.1.3 MEC application**
+
+An MEC application runs on top of the virtualization infrastructure, and can interact with the MEC platform to provide and deploy MEC services. In certain cases, MEC applications can interact with the MEC platform to perform the procedures related to the lifecycle management of the application, such as indicating availability, preparing relocation of user state, etc. MEC applications can have a
+
+certain number of rules and requirements associated to them, such as required resources, minimum bandwidth, maximum latency, required services, etc.
+
+The applications use the exposed network capabilities, infrastructure capabilities and service capabilities of the capability exposure layer of MEP and the capability exposure function in UNIC-CP, to provide various services and applications to end users of public network and dedicated network, such as ultra-high-definition (UHD) video service, augmented reality / virtual reality (AR/VR) service, cloud gaming service, broadcasting service, multicasting service, vertical industry service and vehicular service.
+
+#### **8.1.4 Capability exposure**
+
+The capability exposure layer of MEP provides an integrated development environment for services and applications, offers secure and efficient network capabilities and application enabling functions for services and applications, and orchestrates and manages services and applications to meet diverse service requirements.
+
+The capability exposure layer of MEP exposes the network capabilities and infrastructure capabilities of ME-PAAS, and the service capabilities of network services and application services, to the APP layer of MEP and third-party applications outside MEP.
+
+The exposed capabilities include those specified in clause 7 of this Recommendation.
+
+The capability exposure layer of MEP is recommended to interact with the capability exposure function in UNIC-CP of the FMC network, to provide non-edge capabilities of the FMC network to APP layer of MEP.
+
+### **8.2 Edge management and orchestration**
+
+The edge management and orchestration, which includes MEAO and MEPM, is the brain of the entire FMC edge computing platform. It receives scheduling instructions from O&M personnel, terminals and management interfaces, and schedules edge resources for services and applications deployed at the edge. In this way, edge services and applications can be deployed, and the lifecycles of services and applications can be managed automatically or manually.
+
+MEAO is the service orchestration management centre of the FMC edge computing platform. It is responsible for the overall ME-APP orchestration and lifecycle management. The network functions virtualization orchestrator (NFVO) is the overall orchestration and lifecycle management centre of network components. The MEAO and NFVO cooperate with each other to manage a massive number of FMC edge cloud sites. Based on service requirements and policies, the MEAO manages and orchestrates the required ME-APP in specific regions, while the NFVO manages and orchestrates the UPF or vPGW-U.
+
+The MEPM manages the lifecycles of ME-APPs and MEPs, while the virtualized network function manager (VNFM) manages the lifecycles of the UPFs. The MEPM and VNFM carry out deployment tasks delivered by the MEAO and NFVO, respectively, allocate resources to FMC edge cloud sites and deploy the required ME-APPs and user plane NFs.
+
+## **9 Security considerations**
+
+The unified FMC edge computing platform is required to take into account the issues of security and privacy. Each component of the unified FMC edge computing platform is required to adopt the measures of network information protection and user information protection, to avoid unauthorized access and information leaking.
+
+Security and privacy concerns should be aligned with the requirements specified in [ITU-T Y.3101] and [b-ITU-T Y.2701]. The aspects of physical security, deployment security, communications security, data security and service/application security are required for a unified FMC edge computing platform.
+
+## Bibliography
+
+- [b-ITU-T Y.2701] Recommendation ITU-T Y.2701 (2007), *Security requirements for NGN release 1*.
+- [b-ITU-T Y.3100] Recommendation ITU-T Y.3100 (2017), *Terms and definitions for IMT-2020 network*.
+- [b-ITU-T Y.3131] Recommendation ITU-T Y.3131 (2019), *Functional architecture for supporting fixed mobile convergence in IMT-2020 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 |
+| 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 | 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 |
\ No newline at end of file
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@@ -0,0 +1,693 @@
+
+
+I n t e r n a t i o n a l T e l e c o m m u n i c a t i o n U n i o n
+
+**ITU-T**
+
+TELECOMMUNICATION
+STANDARDIZATION SECTOR
+OF ITU
+
+**Y.3200**
+
+(02/2022)
+
+SERIES Y: GLOBAL INFORMATION
+INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS,
+NEXT-GENERATION NETWORKS, INTERNET OF
+THINGS AND SMART CITIES
+
+Future networks
+
+# --- **Fixed, mobile and satellite convergence – Requirements for IMT-2020 networks and beyond**
+
+Recommendation ITU-T Y.3200
+
+## ITU-T Y-SERIES RECOMMENDATIONS
+
+## GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS, NEXT-GENERATION NETWORKS, INTERNET OF THINGS AND SMART CITIES
+
+## GLOBAL INFORMATION INFRASTRUCTURE
+
+| | |
+|-------------------------------------------|-------------|
+| General | Y.100–Y.199 |
+| Services, applications and middleware | Y.200–Y.299 |
+| Network aspects | Y.300–Y.399 |
+| Interfaces and protocols | Y.400–Y.499 |
+| Numbering, addressing and naming | Y.500–Y.599 |
+| Operation, administration and maintenance | Y.600–Y.699 |
+| Security | Y.700–Y.799 |
+| Performances | Y.800–Y.899 |
+
+## INTERNET PROTOCOL ASPECTS
+
+| | |
+|--------------------------------------------------------------------|---------------|
+| General | Y.1000–Y.1099 |
+| Services and applications | Y.1100–Y.1199 |
+| Architecture, access, network capabilities and resource management | Y.1200–Y.1299 |
+| Transport | Y.1300–Y.1399 |
+| Interworking | Y.1400–Y.1499 |
+| Quality of service and network performance | Y.1500–Y.1599 |
+| Signalling | Y.1600–Y.1699 |
+| Operation, administration and maintenance | Y.1700–Y.1799 |
+| Charging | Y.1800–Y.1899 |
+| IPTV over NGN | Y.1900–Y.1999 |
+
+## NEXT GENERATION NETWORKS
+
+| | |
+|-------------------------------------------------------------------|---------------|
+| Frameworks and functional architecture models | Y.2000–Y.2099 |
+| Quality of Service and performance | Y.2100–Y.2199 |
+| Service aspects: Service capabilities and service architecture | Y.2200–Y.2249 |
+| Service aspects: Interoperability of services and networks in NGN | Y.2250–Y.2299 |
+| Enhancements to NGN | Y.2300–Y.2399 |
+| Network management | Y.2400–Y.2499 |
+| Computing power networks | Y.2500–Y.2599 |
+| Packet-based Networks | Y.2600–Y.2699 |
+| Security | Y.2700–Y.2799 |
+| Generalized mobility | Y.2800–Y.2899 |
+| Carrier grade open environment | Y.2900–Y.2999 |
+
+## **FUTURE NETWORKS**
+
+**Y.3000–Y.3499**
+
+### CLOUD COMPUTING
+
+Y.3500–Y.3599
+
+### BIG DATA
+
+Y.3600–Y.3799
+
+### QUANTUM KEY DISTRIBUTION NETWORKS
+
+Y.3800–Y.3999
+
+### INTERNET OF THINGS AND SMART CITIES AND COMMUNITIES
+
+| | |
+|---------------------------------------------------------|---------------|
+| General | Y.4000–Y.4049 |
+| Definitions and terminologies | Y.4050–Y.4099 |
+| Requirements and use cases | Y.4100–Y.4249 |
+| Infrastructure, connectivity and networks | Y.4250–Y.4399 |
+| Frameworks, architectures and protocols | Y.4400–Y.4549 |
+| Services, applications, computation and data processing | Y.4550–Y.4699 |
+| Management, control and performance | Y.4700–Y.4799 |
+| Identification and security | Y.4800–Y.4899 |
+| Evaluation and assessment | Y.4900–Y.4999 |
+
+*For further details, please refer to the list of ITU-T Recommendations.*
+
+## Recommendation ITU-T Y.3200
+
+# Fixed, mobile and satellite convergence – Requirements for IMT-2020 networks and beyond
+
+## Summary
+
+Recommendation ITU-T Y.3200 specifies the service requirements, network capability requirements, and use cases of fixed, mobile and satellite convergence in the context of the IMT-2020 networks and beyond. Fixed, mobile and satellite convergence (FMSC) are the capabilities that provide services and applications to end users regardless of the fixed, mobile or satellite access technologies being used and independently of the users' location.
+
+## History
+
+| Edition | Recommendation | Approval | Study Group | Unique ID* |
+|---------|----------------|------------|-------------|---------------------------------------------------------------------------|
+| 1.0 | ITU-T Y.3200 | 2022-02-13 | 13 | 11.1002/1000/14857 |
+
+## Keywords
+
+FMSC, IMT-2020, requirements, satellite network.
+
+---
+
+\* To access the Recommendation, type the URL in the address field of your web browser, followed by the Recommendation's unique ID. For example, .
+
+## 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 .
+
+© ITU 2022
+
+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..... | 2 |
+| 4 Abbreviations and acronyms ..... | 2 |
+| 5 Conventions ..... | 3 |
+| 6 Overview ..... | 3 |
+| 7 Service requirements of fixed, mobile and satellite converged network..... | 5 |
+| 7.1 General requirements..... | 5 |
+| 7.2 Service requirements ..... | 6 |
+| 8 Network capability requirements of fixed, mobile and satellite converged networks..... | 6 |
+| 8.1 General requirements..... | 6 |
+| 8.2 Requirements of converged network functions..... | 7 |
+| 8.3 Requirements of applying enabling technologies..... | 11 |
+| 9 Security considerations..... | 12 |
+| Appendix I – Use cases of fixed, mobile and satellite convergence..... | 13 |
+| Bibliography..... | 14 |
+
+
+
+## Recommendation ITU-T Y.3200
+
+# Fixed, mobile and satellite convergence – Requirements for IMT-2020 networks and beyond
+
+## 1 Scope
+
+This Recommendation specifies the service requirements, network capability requirements, and use cases of fixed, mobile and satellite convergence (FMSC) in the IMT-2020 network and beyond. Fixed, mobile and satellite convergence are the capabilities that provide services and applications to end users regardless of the fixed, mobile or satellite access technologies being used and independently of the users' location. This Recommendation specifies the following aspects of fixed, mobile and satellite convergence in the context of the IMT-2020 network and beyond:
+
+- Service requirements, which include general requirements of converged service and requirements of supported converged services.
+- Network capability requirements, which include general requirements of converged network, requirements of converged network functions, and requirements of applying enabling technologies.
+- Use cases of fixed, mobile and satellite convergence.
+
+## 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 Y.3101] Recommendation ITU-T Y.3101 (2018), *Requirements of the IMT-2020 network*.
+
+[ITU-T Y.3102] Recommendation ITU-T Y.3102 (2018), *Framework of the IMT-2020 network*.
+
+[ITU-T Y.3130] Recommendation ITU-T Y.3130 (2018), *Requirements of IMT-2020 fixed mobile convergence*.
+
+[ITU-T Y.3172] Recommendation ITU-T Y.3172 (2019), *Architectural framework for machine learning in future networks including IMT-2020*.
+
+## 3 Definitions
+
+### 3.1 Terms defined elsewhere
+
+This Recommendation uses the following terms defined elsewhere:
+
+**3.1.1 control plane** [b-ITU-T Y.2011]: The set of functions that controls the operation of entities in the stratum or layer under consideration and the functions required to support this control.
+
+**3.1.2 data plane** [b-ITU-T Y.2011]: The set of functions used to transfer data in the stratum or layer under consideration.
+
+**3.1.3 fixed mobile convergence** [b-ITU-T Y.3100]: In the context of IMT-2020, the capabilities that provide services and applications to end users regardless of the fixed or mobile access technologies being used and independently of the users' location.
+
+**3.1.4 IMT-2020** [b-ITU-T Y.3100]: Systems, system components, and related technologies that provide far more enhanced capabilities than those described in [b-ITU-R M.1645].
+
+**3.1.5 machine learning (ML)** [ITU-T Y.3172]: Processes that enable computational systems to understand data and gain knowledge from it without necessarily being explicitly programmed.
+
+**3.1.6 machine learning overlay** [ITU-T Y.3172]: A loosely coupled deployment model of machine learning functionalities whose integration and management with network functions are standardized.
+
+NOTE – A machine learning overlay aims to minimise interdependencies between machine learning functionalities and network functions using standard interfaces, allowing for parallel evolution of functionalities of the two.
+
+**3.1.7 network function** [b-ITU-T Y.3100]: In the context of IMT-2020, a processing function in a network.
+
+**3.1.8 user plane** [b-ITU-T Y.2011]: A synonym for data plane.
+
+### **3.2 Terms defined in this Recommendation**
+
+This Recommendation defines the following term:
+
+**3.2.1 fixed, mobile and satellite convergence:** The capabilities that provide services and applications to end users regardless of the fixed, mobile or satellite access technologies being used independently of the users' location.
+
+## **4 Abbreviations and acronyms**
+
+This Recommendation uses the following abbreviations and acronyms:
+
+| | |
+|------|------------------------------------------|
+| AF | Application Function |
+| AI | Artificial Intelligence |
+| ASF | Authentication Server Function |
+| CEF | Capability Exposure Function |
+| CPE | Customer Premise Equipment |
+| DLT | Distributed Ledger Technology |
+| FMC | Fixed Mobile Convergence |
+| FMSC | Fixed, Mobile and Satellite Convergence |
+| FQDN | Fully Qualified Domain Name |
+| GBR | Guaranteed Bit Rate |
+| GEO | Geostationary Earth Orbit |
+| HEO | Highly Elliptical Orbit |
+| IMSI | International Mobile Subscriber Identity |
+| IoT | Internet of Things |
+| ISDN | Integrated Services Digital Network |
+| LEO | Low Earth Orbit |
+
+| | |
+|--------|------------------------------------------|
+| MEO | Medium Earth Orbit |
+| ML | Machine Learning |
+| MSISDN | Mobile Station ISDN Number |
+| NACF | Network Access Control Function |
+| NFR | Network Function Registry function |
+| NFV | Network Function Virtualization |
+| NGSO | Non-Geostationary Satellite Orbit |
+| NSSF | Network Slice Selection Function |
+| PCF | Policy Control Function |
+| PDU | Protocol Data Unit |
+| QIT | Quantum Information Technology |
+| QoS | Quality of Service |
+| RAN | Radio Access Network |
+| RCS | Rich Communication Suite |
+| SDN | Software-Defined Networking |
+| SMF | Session Management Function |
+| UE | User Equipment |
+| UPF | User Plane Function |
+| URL | Uniform Resource Locator |
+| USM | Unified Subscription Management function |
+
+## 5 Conventions
+
+In this Recommendation:
+
+The keywords "is required to" indicate a requirement that must be strictly followed and from which no deviation is permitted, if conformance to this Recommendation is to be claimed.
+
+The keywords "is recommended" indicate a requirement that is recommended but which is not absolutely required. Thus, this requirement need not be present to claim conformance.
+
+## 6 Overview
+
+With the development of satellite communications technologies especially low earth orbit (LEO) satellite communications technologies, the technical capabilities of satellite communications are enhanced and the use cases and services of satellite communications are also enriched. It is technically possible that a satellite-based network could complement and interact with IMT-2020 land-based network. Fixed, mobile and satellite convergence are the capabilities that provide services and applications to end users regardless of the fixed, mobile or satellite access technologies being used independently of the users' location. The main purpose of fixed, mobile and satellite convergence for a multi-access network is to federate all means of access technologies including fixed, mobile and satellite accesses, providing users with the capability to access the network ubiquitously and enjoy the best service experience under the circumstance. Users and operators benefit from network convergence of fixed, mobile and satellite, in the aspects of seamless service, connection reliability, service continuity, network efficiency, load balancing, disaster recovery, etc.
+
+Figure 6-1 depicts the high-level framework of fixed, mobile and satellite convergence in the IMT-2020 network and beyond. In the high-level framework, the multi-access user equipment (UE) has all the fixed access, mobile access and satellite access. Apart from fixed access networks and mobile access networks, satellite access networks including satellites and satellite gateways are introduced. The converged core network has connections to all the access networks, including fixed access networks, mobile access networks, and satellite access networks; it also connects to the service platform and data network. The control plane functions, user plane functions, service plane functions, and management plane functions are included in the converged core network, in which the control plane functions include network access control function (NACF), session management function (SMF), policy control function (PCF), capability exposure function (CEF), network function registry function (NFR), unified subscription management function (USM), network slice selection function (NSSF), authentication server function (ASF), an application function (AF), the user plane functions include user plane function (UPF) for mobile access, UPF for fixed access and UPF for satellite access [ITU-T Y.3102].
+
+A satellite link is used as the backhaul between the converged core network and fixed/mobile access networks as shown in Figure 6-2. The satellite backhaul network consists of one satellite and two satellite gateways. The satellite gateways connecting to the access network and the core network are used for transporting data via the satellite.
+
+Considering the new features such as low bandwidth, high latency, limited capacity, wide coverage, and dynamic topology of satellite communications, some enabling technologies are required to be introduced in fixed, mobile and satellite converged networks, which may include, but are not limited to, mobility management, session management, connection management, subscription management, service continuity, traffic scheduling, network slicing, multi-access edge computing, and network self-organizing. It is also recommended to apply enabling technologies including artificial intelligence (AI)/ML, distributed ledger technology (DLT), and quantum information technology (QIT) in fixed, mobile and satellite converged networks.
+
+
+
+```
+
+graph LR
+ UE[Multi-access UE] --- FAN[Fixed access network
+(Fixed gateway)]
+ UE --- MAN[Mobile access network
+(Base station)]
+ UE --- SAN[Satellite access network
+(Satellite and satellite gateway)]
+ FAN --- CCN
+ MAN --- CCN
+ SAN --- CCN
+ subgraph CCN [Converged core network]
+ CPF[Control plane functions]
+ UPF[User plane functions]
+ SPF[Service plane functions]
+ MPF[Management plane functions]
+ end
+ CCN --- DN[Data network]
+ DN --- SP[Service platform]
+
+```
+
+Y.3200(22)
+
+Figure 6-1: High-level framework of fixed, mobile and satellite convergence from the viewpoint of satellite access. The diagram shows a Multi-access UE connected to three access networks: Fixed access network (Fixed gateway), Mobile access network (Base station), and Satellite access network (Satellite and satellite gateway). These access networks connect to a Converged core network, which contains Control plane functions, User plane functions, Service plane functions, and Management plane functions. The Converged core network is connected to a Data network, which in turn connects to a Service platform.
+
+**Figure 6-1 – High-level framework of fixed, mobile and satellite convergence from the viewpoint of satellite access**
+
+
+
+```
+
+graph LR
+ UE[Multi-access UE] --> FAN[Fixed access network
+(Fixed gateway)]
+ UE --> MAN[Mobile access network
+(Base station)]
+ FAN --> SBN[Satellite backhaul network
+(Satellite and satellite gateway)]
+ MAN --> SBN
+ SBN --> CCN[Converged core network]
+ subgraph CCN [Converged core network]
+ CPF[Control plane functions]
+ UPF[User plane functions]
+ SPF[Service plane functions]
+ MPF[Management plane functions]
+ end
+ CCN --> DN[Data network]
+ CCN --> SP[Service platform]
+
+```
+
+Figure 6-2: High-level framework of fixed, mobile and satellite convergence from the viewpoint of satellite backhaul. The diagram shows a Multi-access UE connected to both a Fixed access network (Fixed gateway) and a Mobile access network (Base station). Both access networks connect to a Satellite backhaul network (Satellite and satellite gateway). This backhaul network connects to a Converged core network, which contains Control plane functions, User plane functions, Service plane functions, and Management plane functions. The Converged core network then connects to a Data network and a Service platform. Reference: Y.3200(22)
+
+**Figure 6-2 – High-level framework of fixed, mobile and satellite convergence from the viewpoint of satellite backhaul**
+
+## **7 Service requirements of fixed, mobile and satellite converged network**
+
+### **7.1 General requirements**
+
+The general requirements of fixed, mobile and satellite converged services provided by the IMT-2020 network and beyond are as follows.
+
+In the converged network, the user identity used in the fixed access network, mobile access network, satellite access network, and converged core network is unified, in which the user identity is the identification of the user, including but not limited to mobile station integrated services digital network number (MSISDN) and international mobile subscriber identity (IMSI). The processes of mobility management, session management, subscription management, authentication and authorization, policy control, charging, etc. are based on the unified user identity. It is an enhanced requirement on the basis of [ITU-T Y.3130].
+
+- It is required for fixed, mobile and satellite converged networks to support a unified user identity.
+
+In the converged network, the seamless service experience is supported, when there is a handover between fixed access and mobile access, or between fixed access and satellite access, or between mobile access and satellite access, or between satellite accesses, no matter if the handover is initiated by the network side or user side. It is an enhanced requirement on the basis of [ITU-T Y.3130].
+
+- It is required for fixed, mobile and satellite converged network to support service continuity during handover between different access networks.
+
+In the converged network, the best-effort quality of service (QoS) handling and guaranteed bit rate (GBR) QoS handling for fixed access, mobile access, and satellite access are supported. It is an enhanced requirement on the basis of [ITU-T Y.3130].
+
+- It is required for fixed, mobile and satellite converged networks to support best-effort QoS for supported services and applications.
+- It is recommended for fixed, mobile and satellite converged networks to support GBR QoS for supported services and applications, if network capabilities and network resources allow.
+- It is required for fixed, mobile and satellite converged networks to provide QoS for the services and applications that are better than the corresponding non-converged networks.
+
+In the converged network, the service provision method, service charging method, and user account for fixed access, mobile access, and satellite access are unified. It is an enhanced requirement on the basis of [ITU-T Y.3130].
+
+- It is required for fixed, mobile and satellite converged networks to support unified service provision and unified charging.
+
+In the converged network, various types of user equipment, including but not limited to mobile phones, wearable devices, vehicular devices, customer premise equipment (CPE), satellite terminals are to be supported. It is a new requirement compared to [ITU-T Y.3130].
+
+- It is required for fixed, mobile and satellite converged networks to support various types of user equipment.
+
+Service scheduling is the capability to collect information from the application layer, network layer, and user layer to make service scheduling policies such as traffic scheduling and access selection. In the converged network, service scheduling is supported in a fixed access network, mobile access network, satellite access network, and converged core network to achieve efficient use of network capabilities and better QoS. It is a new requirement compared to [ITU-T Y.3130].
+
+- It is recommended for fixed, mobile and satellite converged networks to support service scheduling among different access networks.
+
+### **7.2 Service requirements**
+
+The service requirements of fixed, mobile and satellite converged services provided by the IMT-2020 network and beyond are as follows.
+
+In the converged network, converged voice services, video services, message services, data services, broadcast services, multicast services are to be supported.
+
+- It is required for fixed, mobile and satellite converged networks to support converged voice services and converged video services.
+- It is required for fixed, mobile and satellite converged networks to support converged message services, including short message service, multimedia message service, and rich communication suite (RCS) services.
+- It is required for fixed, mobile and satellite converged networks to support converged data services.
+- It is required for fixed, mobile and satellite converged networks to support converged broadcast services and converged multicast services.
+
+In the converged network, multi-access edge computing services, vertical industry services, and international services are to be supported.
+
+- It is recommended for fixed, mobile and satellite converged networks to support multi-access edge computing services.
+- It is recommended for fixed, mobile and satellite converged networks to support vertical industry services.
+- It is recommended for fixed, mobile and satellite converged networks to support international roaming services and international communications services.
+
+## **8 Network capability requirements of fixed, mobile and satellite converged networks**
+
+### **8.1 General requirements**
+
+The general requirements of fixed, mobile and satellite converged networks of IMT-2020 and beyond are as follows.
+
+In the converged network, the control plane for fixed access, mobile access, and satellite access is unified, providing the functions of mobility management, session management, connection management, subscription management, authentication and authorization, policy control, and capability exposure. It is an enhanced requirement on the basis of [ITU-T Y.3130].
+
+- It is required to support fixed, mobile and satellite converged control planes.
+
+In the converged network, the user planes for fixed access, mobile access, and satellite access are separate, they collaborate with each other to provide the functions of traffic routing and forwarding, traffic filtering, traffic off-load, protocol data unit (PDU) session tunnel management, QoS enforcement, service identification, and fully qualified domain name (FQDN)/uniform resource locator (URL) resolution. It is an enhanced requirement on the basis of [ITU-T Y.3130].
+
+- It is required to support fixed, mobile and satellite collaborative user planes.
+
+In the converged network, the service plane for fixed access, mobile access, and satellite access is unified, providing the services and applications specified in clause 7.2 of this Recommendation with the service plane functions inside of the converged core network and the service platform outside of the converged core network. It is a new requirement compared to [ITU-T Y.3130].
+
+- It is required to support fixed, mobile and satellite converged service planes.
+
+In the converged network, the management plane for fixed access, mobile access, and satellite access is unified, providing the functions of network function management, network connection management, service and application management, user management, and resource management and orchestration. It is an enhanced requirement on the basis of [ITU-T Y.3130].
+
+- It is required to support fixed, mobile and satellite converged management planes.
+
+In the converged network, cloud-based infrastructure and corresponding enabling technologies, which include but are not limited to network function virtualization (NFV) and software-defined networking (SDN), are to be supported. It is an enhanced requirement on the basis of [ITU-T Y.3130].
+
+- It is required to support cloud-based infrastructure enabled by NFV and SDN technologies.
+
+In the converged network, enabling technologies include but are not limited to AI/ML, DLT, and QIT. In some use cases, these enabling technologies are expected to be applied in the converged network. Considering the high mobility of non-geostationary satellite orbit (NGSO) satellite, to predict the NGSO satellite connected to the multi-access UE and core network at a specific time, AI/ML could be applied. Considering the satellite network is decentralized, to realize efficient authentication, authorization, information exchange, and information processing between satellites of the same constellation and different constellations, DLT could be applied. Considering the heterogeneity and security issues of the converged network, to realize authentication and authorization with extremely high reliability, QIT could be applied. It is a new requirement compared to [ITU-T Y.3130].
+
+- It is recommended to apply AI/ML related enabling technologies in fixed, mobile and satellite converged networks.
+- It is recommended to apply DLT related enabling technologies in fixed, mobile and satellite converged networks.
+- It is recommended to apply QIT related enabling technologies in fixed, mobile and satellite converged networks.
+
+### **8.2 Requirements of converged network functions**
+
+#### **8.2.1 Requirements of mobility management**
+
+The converged network is required to support unified mobility management for fixed access, mobile access and satellite access. The speed of the satellite is different from that of the earth so the satellite connecting to the UE may be changed to another. The UE on the earth handovers to a new
+
+satellite if possible. If a UE fails to connect to an access network, then different access networks may be connected to the UE. The detailed requirements of mobility management are as follows.
+
+- It is required to support unified UE access control and satellite access control.
+
+NOTE – Satellite access control is the access control of geostationary earth orbit (GEO) satellite (with no mobility) and NGSO satellite (with high mobility) connected to a satellite gateway and a converged core network.
+
+- It is required to support a unified UE registration management and satellite registration management.
+- It is required to support a unified UE location management and satellite location management.
+- It is required to support a unified UE handover management and satellite handover management.
+- It is required to support a unified UE selection and satellite selection of network functions.
+- It is recommended to support inter-satellite handover between different satellites.
+- It is recommended to support inter-access handover between different accesses.
+
+#### **8.2.2 Requirements of session management**
+
+The converged network is required to support unified session management for fixed access, mobile access, and satellite access. The detailed requirements of session management are as follows.
+
+- It is required to support a unified session life cycle management, including control of PDU session tunnel establishment, modification and release.
+- It is required to support a unified address allocation.
+
+NOTE 1 – In the fixed access network, mobile access network, satellite access network, and converged core network, the address is allocated by using the same method.
+
+- It is required to support a unified routing selection, including traffic steering, traffic splitting, and traffic switching on both the network side and the user equipment side.
+
+NOTE 2 – Traffic steering refers to selecting access network(s) to transport traffic; traffic splitting refers to dividing traffic into multiple pieces which are transported through access networks; traffic switching refers to moving traffic from one access network to another access network.
+
+- It is required to support a unified session continuity, including the ability of the user to maintain continuity of ongoing sessions while changing between terminal devices and across various accesses and core networks.
+
+NOTE 3 – For example, the user of a terminal may wish to switch from a mobile access network to a satellite access network. This should be supported without any session discontinuity.
+
+#### **8.2.3 Requirements of connection management**
+
+The converged network is required to support a unified connection management for fixed access, mobile access and satellite access. The detailed requirements of connection management are as follows.
+
+- It is required to support connection status management, including marking the connection status and efficient utilization of network resources.
+- It is required to provide session continuity and service continuity for rapid movement of NGSO satellites.
+- It is required to support unified signalling connection management, including establishing, migrating, and releasing a signalling connection between a UE and the control plane functions including NACF.
+- It is required to support a unified user plane connection management, including activation, reactivation and deactivation of user plane connections.
+
+- It is required to support dual connectivity, either for transparent or regenerative satellite access and in combination with or without fixed access and mobile access.
+
+NOTE – Dual connectivity includes the addition, modification, and release of secondary user plane connection, transfer of connection information flows between different access networks and different satellites.
+
+#### **8.2.4 Requirements of subscription management**
+
+The converged network is required to support a unified subscription management for fixed access, mobile access and satellite access. The detailed requirements of subscription management are as follows.
+
+- It is required to support a unified user data structure, of which the data segments are specific for different types of multi-access users.
+- It is required to support a unified user data management.
+- It is required to support a user data synchronization between land-based networks and satellite-based networks.
+
+#### **8.2.5 Requirements of authentication and authorization**
+
+The converged network is required to support a unified authentication and authorization for fixed access, mobile access and satellite access. The detailed requirements of authentication and authorization are as follows.
+
+- It is required to support a unified authentication and authorization for multi-access UE and corresponding users.
+- It is required to support a unified authentication and authorization for converged services and applications.
+- It is required to support authentication information synchronization and authorization information synchronization between land-based networks and satellite-based networks.
+
+#### **8.2.6 Requirements of policy control**
+
+The converged network is required to support a unified policy control for fixed access, mobile access and satellite access. The detailed requirements of policy control are as follows.
+
+- It is required to support unified policies unrelated to a session, including UE access policy and UE mobility policy.
+- It is required to support unified policies related to session, including traffic control policy, QoS control policy, event monitoring policy, usage amount monitoring policy and charging policy.
+- It is required to support QoS mechanisms (including best-effort QoS and GBR QoS) for multi-access UE.
+
+#### **8.2.7 Requirements of capability exposure**
+
+The converged network is required to support a unified capability exposure for fixed access, mobile access and satellite access. The exposed capabilities include common capabilities of the IMT-2020 network and specific capabilities of fixed, mobile and satellite convergence. The detailed requirements of capability exposure are as follows.
+
+- It is required to support unified exposure of control plane capabilities.
+- It is required to support unified exposure of user plane capabilities.
+- It is required to support unified exposure of end-to-end QoS capabilities.
+- It is required to support unified exposure of network slicing capabilities.
+- It is required to support unified exposure of multi-access edge computing capabilities.
+
+- It is required to support unified exposure of network management and orchestration capabilities.
+- It is required to support unified exposure of network data analytics capabilities.
+- It is required to support unified exposure of multi-access convergence capabilities, including fixed mobile convergence (FMC) capabilities and FMSC capabilities.
+
+#### **8.2.8 Requirements of user planes**
+
+The converged network is required to support collaborative user planes for fixed access, mobile access and satellite access. The detailed requirements of the user plane are as follows.
+
+- It is required to support unified traffic routing and forwarding.
+- It is required to support unified traffic filtering.
+- It is required to support unified traffic off-load.
+- It is required to support unified PDU session tunnel management.
+- It is required to support unified QoS enforcement.
+- It is required to support unified service identification.
+- It is required to support unified FQDN/URL resolution.
+
+#### **8.2.9 Requirements of service planes**
+
+The converged network is required to support a converged service plane for fixed access, mobile access and satellite access. The detailed requirements of a service plane are as follows.
+
+- It is required to support the service plane functions (inside of the converged core network).
+- It is required to support the service platform (outside of the converged core network).
+
+NOTE – The service plane functions, and the service platform work together to provide the services and applications specified in clause 7.2.
+
+#### **8.2.10 Requirements of management plane**
+
+The converged network is required to support a converged management plane for fixed access, mobile access and satellite access. The detailed requirements of a management plane are as follows.
+
+- It is required to support unified network function management and network connection management.
+- It is required to support unified service and application management.
+- It is required to support unified user management.
+- It is required to support unified resource management and orchestration.
+
+#### **8.2.11 Requirements of satellite classes**
+
+A couple of satellite classes are identified [b-3GPP TR 22.822]. The class is fundamentally defined based on the altitude of the satellite position. The following describes several classes.
+
+- GEO satellites: It is located precisely in the plane of the Equator at an altitude of 35 786 km and these satellites rotate at the same rate as the Earth's rotation.
+- NGSO satellites: NGSO satellites do not stand still with respect to Earth. In order to support service continuity over time, several satellites (a constellation) are required to meet this requirement.
+
+Different classes of NGSO satellites are listed below.
+
+- LEO satellites with altitudes ranging from 500 km to 2 000 km.
+- Medium earth orbit (MEO) satellites with altitude ranging from 8 000 km to 20 000 km.
+
+- Highly elliptical orbit (HEO) satellites with a range of operational altitudes between 7 000 km and more than 45 000 km.
+
+As described above each satellite class can have different QoS requirements (e.g., latency) since the QoS is closely related to the altitude of the satellite position.
+
+The general requirements of fixed, mobile and satellite converged networks of IMT-2020 and beyond are as follows.
+
+- IMT-2020 is recommended to support all of the satellite classes, as many as possible.
+- IMT-2020 is required to support at least one satellite class.
+- IMT-2020 is required to select a proper satellite class for meeting QoS requirements (e.g., latency).
+
+#### **8.2.12 Requirements of satellite link**
+
+A satellite link [b-3GPP TR 22.822] is applied to a satellite access and a satellite backhaul. The satellite access is used for connecting to a UE and a satellite gateway inside the access network. The capabilities of UE support satellite access as well as fixed / mobile accesses. On the other hand, the satellite backhaul is used for transporting data between the access network and the core network. In this case, the UE would be capable of fixed / mobile accesses only.
+
+The requirements of satellite links for fixed, mobile and satellite converged networks of IMT-2020 and beyond are as follows.
+
+- IMT-2020 is required to support at least one satellite link, either satellite access or satellite backhaul.
+- IMT-2020 is recommended to support all of the satellite links as many as possible.
+
+#### **8.2.13 Requirements of multi-connectivity**
+
+A UE has different access interfaces such as terrestrial and satellite. The satellite access interfaces are LEO, MEO, and GEO. The UE may support multiple satellite access interfaces. In this condition, the UE can appropriately select a single access interface that matches the feature of the requesting service. Furthermore, the UE can use multiple access interfaces at the same time and transmit more data by aggregating the accesses. In other words, it is considered as multi-connectivity.
+
+Multi-connectivity may be applied to backhaul between radio access network (RAN) node and a core network.
+
+The requirements of multi-connectivity for fixed, mobile and satellite converged networks of IMT-2020 and beyond are as follows.
+
+- IMT-2020 is required to select a single access interface that matches the feature of a requesting service.
+- IMT-2020 is recommended to support multi-connectivity.
+
+### **8.3 Requirements of applying enabling technologies**
+
+#### **8.3.1 Requirements of applying AI/ML**
+
+The converged network is recommended to support AI/ML in the aspects of mobility management, connection management, subscription management, policy control, capability exposure, network self-organizing, and management and orchestration.
+
+The converged network is recommended to support the high-level architectural requirements of the AI/ML overlay.
+
+NOTE 1 – The use case of applying AI/ML in the FMSC network includes predicting the NGSO satellite connected to the multi-access UE and the core network at a specific time, in which AI/ML could accelerate the process of prediction and increase the accuracy of prediction.
+
+NOTE 2 – AI/ML overlay is specified in [ITU-T Y.3172].
+
+#### **8.3.2 Requirements of applying DLT**
+
+The converged network is recommended to support DLT in the aspects of mobility management, session management, connection management, authentication and authorization, and network self-organizing.
+
+NOTE – The use case of applying DLT in the FMSC network includes realizing efficient authentication, authorization, information exchange and information processing between satellites of the same constellation and of different constellations, in which DLT could help to build the FMSC network in a decentralized, trustworthy and efficient way.
+
+#### **8.3.3 Requirements of applying QIT**
+
+The converged network is recommended to support QIT in the aspect of authentication and authorization, including the authentication and authorization of land to satellite, satellite to land and inter-satellite.
+
+NOTE – The use case of applying QIT in the FMSC network includes realizing the authentication and authorization between satellites with extremely high reliability, in which QIT could guarantee the security of information being transmitted between network entities.
+
+## **9 Security considerations**
+
+The security and privacy considerations of fixed, mobile and satellite convergence in the IMT-2020 network and beyond include the following aspects.
+
+- Control plane security, which includes the security considerations on NACF, SMF, PCF, CEF, NFR, USM, NSSF, ASF, and AF, which have been enhanced to support fixed, mobile and satellite convergence.
+- User plane security, which includes the security considerations on UPF for mobile access, UPF for fixed access, and UPF for satellite access, which have been enhanced to support collaboration in fixed access, mobile access and satellite access.
+- Service plane security, which includes the security considerations on converged voice services, video services, message services, data services, broadcast services, multicast services, multi-access edge computing services, vertical industry services, international services, and converged capability exposure and corresponding applications.
+- Management plane security, which includes the security considerations on the converged management and orchestration functions of network, capability, service and application, user and resource.
+- User privacy, which includes the privacy considerations on converged core network, fixed access network, mobile access network, and satellite access network, which could store, cache and process user data related to privacy.
+
+In addition, the security and privacy considerations of fixed, mobile and satellite convergence should be aligned with the requirements specified in [ITU-T Y.3101] and [b-ITU-T Y.2701].
+
+## **Appendix I**
+
+### **Use cases of fixed, mobile and satellite convergence**
+
+(This appendix does not form an integral part of this Recommendation.)
+
+The use cases of fixed, mobile and satellite convergence are as follows.
+
+#### **Use case 1: Land-based network with low speed**
+
+The use cases of land-based networks with low speed include a remote village, remote settlement, ecoregion, small isle, etc., in which there are land-based networks with low speed, that could not meet the requirements of users and the communications services. Fixed, mobile and satellite convergence facilitates the provision of services specified in clause 7.2 and enhances the QoS in the above use cases.
+
+#### **Use case 2: Land-based network with low capacity**
+
+The use cases of land-based networks with low capacity include remote Internet of things (IoT), remote industrial networks, remote vehicular networks, etc., in which there are land-based networks with low capacity, that could not meet the requirements of users and the communications services. Fixed, mobile and satellite convergence facilitates the provision of services specified in clause 7.2 and enhances the QoS in the above use cases.
+
+#### **Use case 3: No land-based network of a specific operator**
+
+The use cases of no land-based networks of specific operators include domestic roaming between operators, international roaming between operators and international communications service provision, in which there are no land-based networks of specific operators. The precondition is, the above use cases should conform to the local communications regulations. Given this precondition, the above use cases could be supported with fixed, mobile and satellite convergence. Fixed, mobile and satellite convergence facilitates the provision of services specified in clause 7.2 and enhances the QoS in the above use cases.
+
+#### **Use case 4: Disaster recovery**
+
+The use cases of disaster recovery include large-scale disaster recovery and local disaster recovery, where land-based networks cannot work properly, or the capacity of a land-based network cannot meet the requirements of users and the communications services. Fixed, mobile and satellite convergence facilitates the provision of services specified in clause 7.2 and enhances the QoS in the above use cases.
+
+## Bibliography
+
+- [b-ITU-T Y.2011] Recommendation ITU-T Y.2011 (2004), *General principles and general reference model for Next Generation Networks*.
+- [b-ITU-T Y.2701] Recommendation ITU-T Y.2701 (2007), *Security requirements for NGN release 1*.
+- [b-ITU-T Y.3100] Recommendation ITU-T Y.3100 (2017), *Terms and definitions for IMT-2020 network*.
+- [b-ITU-R M.1645] Recommendation ITU-R M.1645 (2003), *Framework and overall objectives of the future development of IMT-2000 and systems beyond IMT-2000*.
+- [b-3GPP TR 22.822] 3GPP TR 22.822 (2018), *Study on using satellite access in 5G, Stage 1 (Release 16)*.
+<>
+
+
+
+## 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 |
+| 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 | 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 |
\ No newline at end of file
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new file mode 100644
index 0000000000000000000000000000000000000000..cd691867a02fa71f73f2be5bee5fb8c5a3de236e
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+++ b/marked/Y/T-REC-Y.3211-202503-I_PDF-E/raw.md
@@ -0,0 +1,387 @@
+
+
+# Recommendation
+
+## **ITU-T Y.3211 (03/2025)**
+
+SERIES Y: Global information infrastructure, Internet protocol aspects, next-generation networks, Internet of Things and smart cities
+
+Future networks
+
+---
+
+**Fixed, mobile and satellite convergence –
+Requirements of supporting airborne
+broadband communications for IMT-2020
+networks and beyond**
+
+## ITU-T Y-SERIES RECOMMENDATIONS
+
+# Global information infrastructure, Internet protocol aspects, next-generation networks, Internet of Things and smart cities
+
+| | |
+|--------------------------------------------------------------------|----------------------|
+| GLOBAL INFORMATION INFRASTRUCTURE | Y.100-Y.999 |
+| General | Y.100-Y.199 |
+| Services, applications and middleware | Y.200-Y.299 |
+| Network aspects | Y.300-Y.399 |
+| Interfaces and protocols | Y.400-Y.499 |
+| Numbering, addressing and naming | Y.500-Y.599 |
+| Operation, administration and maintenance | Y.600-Y.699 |
+| Security | Y.700-Y.799 |
+| Performances | Y.800-Y.899 |
+| INTERNET PROTOCOL ASPECTS | Y.1000-Y.1999 |
+| General | Y.1000-Y.1099 |
+| Services and applications | Y.1100-Y.1199 |
+| Architecture, access, network capabilities and resource management | Y.1200-Y.1299 |
+| Transport | Y.1300-Y.1399 |
+| Interworking | Y.1400-Y.1499 |
+| Quality of service and network performance | Y.1500-Y.1599 |
+| Signalling | Y.1600-Y.1699 |
+| Operation, administration and maintenance | Y.1700-Y.1799 |
+| Charging | Y.1800-Y.1899 |
+| IPTV over NGN | Y.1900-Y.1999 |
+| NEXT GENERATION NETWORKS | Y.2000-Y.2999 |
+| Frameworks and functional architecture models | Y.2000-Y.2099 |
+| Quality of Service and performance | Y.2100-Y.2199 |
+| Service aspects: Service capabilities and service architecture | Y.2200-Y.2249 |
+| Service aspects: Interoperability of services and networks in NGN | Y.2250-Y.2299 |
+| Enhancements to NGN | Y.2300-Y.2399 |
+| Network management | Y.2400-Y.2499 |
+| Computing power networks | Y.2500-Y.2599 |
+| Packet-based Networks | Y.2600-Y.2699 |
+| Security | Y.2700-Y.2799 |
+| Generalized mobility | Y.2800-Y.2899 |
+| Carrier grade open environment | Y.2900-Y.2999 |
+| FUTURE NETWORKS | Y.3000-Y.3499 |
+| CLOUD COMPUTING | Y.3500-Y.3599 |
+| BIG DATA | Y.3600-Y.3799 |
+| QUANTUM KEY DISTRIBUTION NETWORKS | Y.3800-Y.3999 |
+| INTERNET OF THINGS AND SMART CITIES AND COMMUNITIES | Y.4000-Y.4999 |
+| General | Y.4000-Y.4049 |
+| Definitions and terminologies | Y.4050-Y.4099 |
+| Requirements and use cases | Y.4100-Y.4249 |
+| Infrastructure, connectivity and networks | Y.4250-Y.4399 |
+| Frameworks, architectures and protocols | Y.4400-Y.4549 |
+| Services, applications, computation and data processing | Y.4550-Y.4699 |
+| Management, control and performance | Y.4700-Y.4799 |
+| Identification and security | Y.4800-Y.4899 |
+| Evaluation and assessment | Y.4900-Y.4999 |
+
+For further details, please refer to the list of ITU-T Recommendations.
+
+# Recommendation ITU-T Y.3211
+
+# Fixed, mobile and satellite convergence – Requirements of supporting airborne broadband communications for IMT-2020 networks and beyond
+
+## Summary
+
+Airborne broadband communications can provide data services for the transmission of cabin passenger data. Supporting airborne broadband communications for fixed, mobile and satellite convergence (FMSC) for IMT-2020 networks and beyond can guarantee the network connection of aircraft from take-off to landing. Recommendation ITU-T Y.3211 specifies the non-radio aspects' requirements of supporting airborne broadband communications for fixed, mobile and satellite convergence for IMT-2020 networks and beyond.
+
+## History\*
+
+| Edition | Recommendation | Approval | Study Group | Unique ID |
+|---------|----------------|------------|-------------|--------------------|
+| 1.0 | ITU-T Y.3211 | 2025-03-10 | 13 | 11.1002/1000/16144 |
+
+## Keywords
+
+Airborne broadband communication, FMSC, IMT-2020, satellite network.
+
+---
+
+\* To access the Recommendation, type the URL 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 .
+
+© 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 Scope ..... | 1 |
+| 2 References..... | 1 |
+| 3 Definitions ..... | 1 |
+| 3.1 Terms defined elsewhere..... | 1 |
+| 3.2 Terms defined in this Recommendation..... | 2 |
+| 4 Abbreviations and acronyms ..... | 2 |
+| 5 Conventions ..... | 2 |
+| 6 Overview ..... | 3 |
+| 7 Requirements of supporting airborne broadband communications for FMSC..... | 4 |
+| 7.1 General requirements..... | 4 |
+| 7.2 Functional requirements ..... | 4 |
+| 8 Security considerations of supporting airborne broadband communications for
FMSC..... | 6 |
+| Appendix I – Use cases of supporting airborne broadband communications for FMSC ..... | 7 |
+| Bibliography..... | 9 |
+
+
+
+# Recommendation ITU-T Y.3211
+
+# Fixed, mobile and satellite convergence – Requirements of supporting airborne broadband communications for IMT-2020 networks and beyond
+
+## 1 Scope
+
+This Recommendation specifies the requirements of supporting airborne broadband communications for fixed, mobile and satellite convergence for IMT-2020 networks and beyond.
+
+The scope of this Recommendation includes:
+
+- overview of supporting airborne broadband communications for FMSC;
+- requirements of supporting airborne broadband communications for FMSC;
+- security considerations of supporting airborne broadband communications for FMSC.
+
+Some relevant use cases are provided in Appendix I.
+
+## 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 Y.3101] Recommendation ITU-T Y.3101 (2018), *Requirements of the IMT-2020 network*.
+
+[ITU-T Y.3200] Recommendation ITU-T Y.3200 (2022), *Fixed, mobile and satellite convergence – Requirements for IMT-2020 networks and beyond*.
+
+## 3 Definitions
+
+### 3.1 Terms defined elsewhere
+
+This Recommendation uses the following terms defined elsewhere:
+
+**3.1.1 backhaul** [b-ITU-T Y.3100]: A network path between base station systems and a core network.
+
+**3.1.2 control plane** [b-ITU-T Y.2011]: The set of functions that controls the operation of entities in the stratum or layer under consideration and the functions required to support this control.
+
+**3.1.3 data plane** [b-ITU-T Y.2011]: The set of functions used to transfer data in the stratum or layer under consideration.
+
+**3.1.4 fixed, mobile and satellite convergence (FMSC)** [ITU-T Y.3200]: The capabilities that provide services and applications to end users regardless of the fixed, mobile or satellite access technologies being used independently of the users' location.
+
+**3.1.5 IMT-2020** [b-ITU-T Y.3100]: Systems, system components, and related technologies that provide far more enhanced capabilities than those described in [b-ITU-R M.1645].
+
+NOTE – [b-ITU-R M.1645] defines the framework and overall objectives of the future development of IMT-2000 and systems beyond IMT-2000 for the radio access network.
+
+**3.1.6 network function** [b-ITU-T Y.3100]: In the context of IMT-2020, a processing function in a network.
+
+### **3.2 Terms defined in this Recommendation**
+
+None.
+
+## **4 Abbreviations and acronyms**
+
+This Recommendation uses the following abbreviations and acronyms:
+
+| | |
+|------|------------------------------------------|
+| AF | Application Function |
+| AP | Access Point |
+| API | Application Programming Interface |
+| ASF | Authentication Server Function |
+| ATG | Air To Ground |
+| BS | Base Station |
+| CEF | Capability Exposure Function |
+| FMSC | Fixed, Mobile and Satellite Convergence |
+| NACF | Network Access Control Function |
+| NFR | Network Function Registry function |
+| NFV | Network Function Virtualization |
+| NSSF | Network Slice Selection Function |
+| PCF | Policy Control Function |
+| PDU | Protocol Data Unit |
+| PLMN | Public Land Mobile Network |
+| QoS | Quality of Service |
+| SDN | Software Defined Networking |
+| SMF | Session Management Function |
+| UE | User Equipment |
+| UPF | User Plane Function |
+| USM | Unified Subscription Management Function |
+
+## **5 Conventions**
+
+In this Recommendation:
+
+The keywords "is required to" indicate a requirement which must be strictly followed and from which no deviation is permitted, if conformance to this Recommendation is to be claimed.
+
+The keywords "is recommended" indicate a requirement which is recommended but which is not absolutely required. Thus, this requirement need not be present to claim conformance.
+
+# 6 Overview
+
+With the development of land mobile communication technology, mobile broadband services are becoming more common on land, but the growing demand for airborne broadband communications still cannot be satisfied. Air-to-ground (ATG) refers to an in-flight connectivity technique, using ground-based cells connected to an aircraft's onboard access device. Onboard access devices can also realize broadband communications via satellite communications. Compared with satellite communications, ATG communications have the advantage of high throughput, low propagation delay and low-cost application. Satellite links are clearly also needed for long-haul trans-oceanic routes with relatively costly and exhibit increased latency.
+
+The ground connection will be converted into Wi-Fi by a cabin access point (AP) or mobile cell by an airborne base station (BS) and provided to passengers. At the same time, the airborne server can provide entertainment for passengers through cabin AP access. Standardization and establishing relevant requirements for in-cabin communications increase safety of airborne broadband communications. In addition, the increasingly strong demand from air passengers for data services can be satisfied by airborne broadband communications. It can also cooperate with airlines or service providers to expand value-added services, enrich in-flight entertainment content and improve travel experience.
+
+Normally, satellite and ATG communications are utilized to independently serve airborne broadband communications. When the aircraft is on the ground, the terrestrial public land mobile network (PLMN) can also be utilized for aircraft communications. With the development of IMT-2020 and beyond, fixed, mobile and satellite access are converging, making it possible to integrate satellite, ATG and terrestrial PLMN networks to provide reliable airborne broadband communications from aircraft take-off to landing. Both air passengers and operators can benefit from a seamless service, connection reliability, service continuity, network efficiency, load balancing etc.
+
+[ITU-T Y.3200] specifies the service requirements, network capability requirements, and use cases of fixed, mobile and satellite convergence in the context of IMT-2020 networks and beyond but it only considers supporting satellite backhaul in FMSC networks. For airborne broadband communications, ATG, satellite or terrestrial PLMN networks can be the backhaul network for the in-cabin fixed access network in airborne broadband communications. Therefore, the FMSC network needs to be enhanced to support these types of backhauls.
+
+
+
+```
+graph LR; InCabinUE[In-cabin UE] --- FixedAccessNetwork[Fixed access network]; FixedAccessNetwork --- ATGBackhaul[ATG backhaul network]; FixedAccessNetwork --- SatelliteBackhaul[Satellite backhaul network]; FixedAccessNetwork --- TerrestrialPLMNBackhaul[Terrestrial PLMN backhaul network]; ATGBackhaul --- CoreNetwork[Converged core network—airborne broadband communication enhancements]; SatelliteBackhaul --- CoreNetwork; TerrestrialPLMNBackhaul --- CoreNetwork; subgraph CoreNetwork [Converged core network—airborne broadband communication enhancements]; direction TB; CP[Control plane functions]; UP[User plane functions]; SP[Service plane functions]; MP[Management plane functions]; end;
+```
+
+Figure 6-1: Converged core network enhancements of supporting airborne broadband communications for FMSC. The diagram shows an 'In-cabin UE' connected to a 'Fixed access network'. This network then branches into three backhaul options: 'ATG backhaul network', 'Satellite backhaul network', and 'Terrestrial PLMN backhaul network'. All three backhaul networks connect to a large box labeled 'Converged core network—airborne broadband communication enhancements'. Inside this box are four stacked components: 'Control plane functions', 'User plane functions', 'Service plane functions', and 'Management plane functions'. The reference 'Y.3211(25)' is at the bottom right.
+
+**Figure 6-1 – Converged core network enhancements of supporting airborne broadband communications for FMSC**
+
+Figure 6-1 shows the converged core network enhancements of supporting airborne broadband communications for FMSC. The converged core network of supporting airborne broadband communications includes control plane functions, user plane functions, service plane functions and management plane functions. To obtain the advantages of supporting airborne broadband
+
+communications for FMSC, some of the network functions in the converged network need to be enhanced to support multiple types of backhauls for in-cabin fixed access networks.
+
+NOTE 1 – From a geographical point of view, both ATG networks and terrestrial PLMNs have ground-based deployment; the difference is that ATG networks are dedicated to serving aircraft in the air, while terrestrial PLMNs serve ground users. Here, the terrestrial PLMN refers to IMT-2020 networks and beyond in this Recommendation, which is different from legacy ATG networks.
+
+NOTE 2 – In-cabin user equipment means ordinary user equipment like smartphones, laptops, etc. used for connecting to airborne base stations or access points of fixed access networks operated by public communication providers.
+
+# **7 Requirements of supporting airborne broadband communications for FMSC**
+
+## **7.1 General requirements**
+
+The general requirements of supporting airborne broadband communications for FMSC are as follows:
+
+- It is required to support at least one backhaul (ATG, satellite or terrestrial PLMN backhaul) of supporting airborne broadband communications for FMSC.
+- It is required to monitor and identify the backhaul status of supporting airborne broadband communications for FMSC.
+- It is required to ensure advanced techniques to improve the robustness and reliability of backhaul connection of supporting airborne broadband communications for FMSC.
+- It is recommended to support all means of backhauls (ATG, satellite and terrestrial PLMN backhaul) of supporting airborne broadband communications for FMSC.
+- It is recommended to support multiconnection between in-cabin user equipment (UE) and converged core networks through ATG, satellite or terrestrial PLMN backhauls.
+
+### **7.2 Functional requirements**
+
+### **7.2.1 Converged control plane functional requirements**
+
+The converged control plane function is required to be enhanced to support multiple backhauls. The detailed requirements are as follows:
+
+- It is required to support adding or deleting backhauls when the connection quality of the backhaul changes.
+- It is required to support switching among different backhauls to select the most appropriate backhaul to achieve a reliable connection.
+- It is required to support backhaul switching when a certain backhaul has broken down.
+- It is required to have the capability to manage and maintain the protocol data unit (PDU) sessions during backhaul switching procedure.
+- It is required to support collecting status information from backhaul networks (ATG, satellite and terrestrial PLMN backhaul) and providing it to the service plane.
+- It is recommended to support a unified register, and manage and expose the ATG, satellite and terrestrial PLMN backhauls capabilities.
+- It is recommended to manage a dedicated repository for the storage of the information to be exposed from supporting airborne broadband communications for FMSC.
+- It is recommended to expose quality of service (QoS) information related to backhaul capabilities that is accessible to authorized third parties.
+- It is recommended to provide application programming interfaces (APIs) that allow authorized third parties to get information related to in-cabin UE backhaul types and status.
+
+### **7.2.2 Converged user plane functional requirements**
+
+The converged user plane function is required to be enhanced to manage multiple types of in-cabin UE data. The detailed requirements are as follows:
+
+- It is required to support managing the transmitted user equipment data. As aviation scenarios have special requirements for data guarantee and monitoring, it is necessary to provide differentiated protection for in-cabin UE data.
+- It is required to support separate user plane functions (UPFs) that are connected to different backhauls and collaborate with each other for forwarding data packets under the instructions of the corresponding control plane functions.
+- It is required to support an enhanced QoS mechanism that enables in-cabin UE to use the received downlink packets to map the uplink packets' QoS flow.
+
+#### **7.2.3 Converged service plane functional requirements**
+
+The converged service plane function is required to be enhanced to support service consistency for airborne broadband communications. The detailed requirements are as follows:
+
+- It is required to support unified service scheduling policies to steer, split and switch services between ATG, satellite and terrestrial PLMN backhauls.
+- It is required to support service scheduling policies which are based on the backhaul status information (ATG, satellite and terrestrial) collected and provided by the control plane.
+- It is required to guarantee service continuity during ATG, satellite and terrestrial PLMN backhaul switching.
+- It is required to support uniform QoS metrics regardless of backhaul types of supporting airborne broadband communications for FMSC.
+- It is required to support different QoS service priorities, such as cockpit and cabin services. The mapping relationship between the QoS and different types of services should be unified in supporting airborne broadband communications for FMSC.
+- It is required to support a high bandwidth service for supporting airborne broadband communications for FMSC.
+- It is recommended to support low latency services of supporting airborne broadband communications for FMSC.
+- It is recommended to support seamless communication roaming and handoff throughout the flight.
+
+#### **7.2.4 Converged management plane functional requirements**
+
+The converged management plane function is required to be enhanced to support appropriate management services for airborne broadband communications. The detailed requirements are as follows:
+
+- It is required to support network element status management, life cycle management and orchestration, e.g., based on software-defined networking (SDN)/network function virtualization (NFV).
+- It is required to support unified management of the converged core network of supporting airborne broadband communications, including performance management, fault management, configuration management, accounting management and security management, regardless of backhaul type.
+- It is required to support the real-time management of various types of in-cabin UEs and in-flight broadband communication services.
+
+## **8 Security considerations of supporting airborne broadband communications for FMSC**
+
+The security and privacy considerations of supporting airborne broadband communications for FMSC include the following aspects:
+
+- Control plane security, which includes the security considerations of the network access control function (NACF), session management function (SMF), policy control function (PCF), capability exposure function (CEF), network function registry (NFR) function, unified subscription management (USM) function, network slice selection function (NSSF), authentication server function (ASF) and application function (AF), which have been enhanced to support airborne broadband communications with ATG, satellite and terrestrial PLMN backhaul for fixed, mobile and satellite convergence;
+- user plane security, which includes the security considerations on UPF for ATG, satellite and terrestrial PLMN backhaul, which have been enhanced to support airborne broadband communications for fixed access, mobile access and satellite access;
+- service plane security, which includes the security considerations on different QoS service priorities of cockpit and cabin services such as voice services, video services, message services, data services, broadcast services, multicast services, and converged capability exposure and corresponding applications;
+- management plane security, which includes the security considerations on the management and orchestration functions;
+- data security, which includes the security and end-to-end encryption for data integrity and privacy protection with ATG, satellite and terrestrial PLMN backhauls;
+- user privacy, which includes the privacy considerations on airborne broadband communications with ATG, satellite and terrestrial PLMN backhauls.
+
+In addition to the above, the security and privacy considerations should be aligned with the requirements specified in [ITU-T Y.3200], [ITU-T Y.3101] and [b-ITU-T Y.2701].
+
+## Appendix I
+
+### Use cases of supporting airborne broadband communications for FMSC
+
+(This appendix does not form an integral part of this Recommendation.)
+
+The use cases of supporting airborne broadband communications for FMSC are as follows.
+
+### Use case 1: Trans-oceanic long-haul flight
+
+
+
+Terrestrial PLMN backhaul
+
+Y.3211(25)
+
+Diagram illustrating the trans-oceanic long-haul flight use case for supporting airborne broadband communications for FMSC. The diagram shows a sequence of aircraft connected by a red dashed line, representing the flight path. A satellite in the sky is connected to the aircraft via a black curved line labeled 'Satellite backhaul'. The aircraft are connected to ground stations via yellow lightning bolts labeled 'ATG backhaul'. The ground stations are connected to terrestrial PLMN backhaul networks via red dashed lines. The diagram includes images of an aircraft, a ground station, the ocean, another ground station, and another aircraft. The labels 'Terrestrial PLMN backhaul' are placed below the ground station images. The label 'Y.3211(25)' is located at the bottom right of the diagram.
+
+**Figure I.1 – Trans-oceanic long-haul flight of supporting airborne broadband communications for FMSC**
+
+As a special mobile network with airline connection, airborne broadband communications will become an important part of FMSC networks. Depending on the aircraft status, ATG, satellite and terrestrial PLMN backhaul can be selected as the backhaul network for airborne broadband communications. Trans-oceanic long-haul flights of supporting airborne broadband communications for FMSC is shown in Figure I.1:
+
+- Low-altitude stage: When the aircraft is in the state of landing, just taking off or approaching landing, the flight altitude is relatively low in this scenario. There is usually good terrestrial PLMN network connection near the airport, which can be used as the backhaul network for the in-cabin UEs.
+- High-altitude stage with good ATG network connection: When the aircraft is flying at a high altitude, such as in cruise state, ATG connection has good coverage in the air but the terrestrial PLMN network cannot cover it at this time. ATG backhaul can be used as the backhaul network for the in-cabin UEs.
+- High-altitude stage with poor ATG network connection: When the aircraft is flying over a remote area or flying over the ocean, the ground ATG connection cannot be covered. Satellite backhaul is the only choice for the in-cabin UEs.
+
+### **Use case 2: Limited satellite connection**
+
+An aircraft is flying over an urban area with limited satellite connection. The onboard entertainment system relies on satellite connections to provide passengers with data services, streaming services, and real-time flight information updates. However, due to the limited satellite connection in the area, data speeds are poor, and latency is high. Thanks to the aircraft being connected to the FMSC network of supporting airborne broadband communications, the aircraft can switch to an ATG connection as a backup option. ATG can provide passengers with stable and faster connectivity. This ensures that passengers can continue to access their entertainment content, stay updated with their flight information and remain connected throughout the journey.
+
+## Bibliography
+
+- [b-ITU-T Y.2011] Recommendation ITU-T Y.2011 (2004), *General principles and general reference model for Next Generation Networks*.
+- [b-ITU-T Y.2701] Recommendation ITU-T Y.2701 (2007), *Security requirements for NGN release 1*.
+- [b-ITU-T Y.3100] Recommendation ITU-T Y.3100 (2017), *Terms and definitions for IMT-2020 network*.
+- [b-ITU-R M.1645] Recommendation ITU-R M.1645 (2003), *Framework and overall objectives of the future development of IMT-2000 and systems beyond IMT-2000*.
+
+## 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 |
+| 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 | 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 |
\ No newline at end of file
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@@ -0,0 +1,968 @@
+
+
+# Recommendation
+
+## **ITU-T Y.3260 (09/2024)**
+
+SERIES Y: Global information infrastructure, Internet protocol aspects, next-generation networks, Internet of Things and smart cities
+
+Future networks
+
+## --- **Assessing trust evaluation models for telecommunication networks**
+
+## ITU-T Y-SERIES RECOMMENDATIONS
+
+### Global information infrastructure, Internet protocol aspects, next-generation networks, Internet of Things and smart cities
+
+| | |
+|--------------------------------------------------------------------|----------------------|
+| GLOBAL INFORMATION INFRASTRUCTURE | Y.100-Y.999 |
+| General | Y.100-Y.199 |
+| Services, applications and middleware | Y.200-Y.299 |
+| Network aspects | Y.300-Y.399 |
+| Interfaces and protocols | Y.400-Y.499 |
+| Numbering, addressing and naming | Y.500-Y.599 |
+| Operation, administration and maintenance | Y.600-Y.699 |
+| Security | Y.700-Y.799 |
+| Performances | Y.800-Y.899 |
+| INTERNET PROTOCOL ASPECTS | Y.1000-Y.1999 |
+| General | Y.1000-Y.1099 |
+| Services and applications | Y.1100-Y.1199 |
+| Architecture, access, network capabilities and resource management | Y.1200-Y.1299 |
+| Transport | Y.1300-Y.1399 |
+| Interworking | Y.1400-Y.1499 |
+| Quality of service and network performance | Y.1500-Y.1599 |
+| Signalling | Y.1600-Y.1699 |
+| Operation, administration and maintenance | Y.1700-Y.1799 |
+| Charging | Y.1800-Y.1899 |
+| IPTV over NGN | Y.1900-Y.1999 |
+| NEXT GENERATION NETWORKS | Y.2000-Y.2999 |
+| Frameworks and functional architecture models | Y.2000-Y.2099 |
+| Quality of Service and performance | Y.2100-Y.2199 |
+| Service aspects: Service capabilities and service architecture | Y.2200-Y.2249 |
+| Service aspects: Interoperability of services and networks in NGN | Y.2250-Y.2299 |
+| Enhancements to NGN | Y.2300-Y.2399 |
+| Network management | Y.2400-Y.2499 |
+| Computing power networks | Y.2500-Y.2599 |
+| Packet-based Networks | Y.2600-Y.2699 |
+| Security | Y.2700-Y.2799 |
+| Generalized mobility | Y.2800-Y.2899 |
+| Carrier grade open environment | Y.2900-Y.2999 |
+| FUTURE NETWORKS | Y.3000-Y.3499 |
+| CLOUD COMPUTING | Y.3500-Y.3599 |
+| BIG DATA | Y.3600-Y.3799 |
+| QUANTUM KEY DISTRIBUTION NETWORKS | Y.3800-Y.3999 |
+| INTERNET OF THINGS AND SMART CITIES AND COMMUNITIES | Y.4000-Y.4999 |
+| General | Y.4000-Y.4049 |
+| Definitions and terminologies | Y.4050-Y.4099 |
+| Requirements and use cases | Y.4100-Y.4249 |
+| Infrastructure, connectivity and networks | Y.4250-Y.4399 |
+| Frameworks, architectures and protocols | Y.4400-Y.4549 |
+| Services, applications, computation and data processing | Y.4550-Y.4699 |
+| Management, control and performance | Y.4700-Y.4799 |
+| Identification and security | Y.4800-Y.4899 |
+| Evaluation and assessment | Y.4900-Y.4999 |
+
+For further details, please refer to the list of ITU-T Recommendations.
+
+# Recommendation ITU-T Y.3260Assessing trust evaluation models for telecommunication networks
+
+## Summary
+
+To build a trustworthy telecommunication network, it is considered that trust needs to be evaluated across end-devices, access networks, and core networks. As a result, many trust evaluation models have been proposed for telecommunication networks. However, these trust evaluation models are designed using different approaches, making it difficult for network operators to compare and analyse the performance of said trust evaluation models. To solve this issue, Recommendation ITU-T Y.3260 provides a comprehensive set of metrics, recommended approaches and procedures for assessing trust evaluation models for telecommunication networks. This Recommendation will serve as a guide for network operators when comparing and selecting suitable trust evaluation models for their networks.
+
+## History\*
+
+| Edition | Recommendation | Approval | Study Group | Unique ID |
+|---------|----------------|------------|-------------|--------------------|
+| 1.0 | ITU-T Y.3260 | 2024-09-13 | 13 | 11.1002/1000/16129 |
+
+## Keywords
+
+Trust evaluation, trust model assessment, trust model evaluation.
+
+---
+
+\* To access the Recommendation, type the URL 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 .
+
+© 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 | Scope ..... | 1 |
+| 2 | References..... | 1 |
+| 3 | Definitions ..... | 1 |
+| | 3.1 Terms defined elsewhere..... | 1 |
+| | 3.2 Terms defined in this Recommendation..... | 2 |
+| 4 | Abbreviations and acronyms ..... | 2 |
+| 5 | Conventions..... | 2 |
+| 6 | Motivations to assess trust evaluation models for telecommunication networks..... | 2 |
+| 7 | Overview of trust evaluation models for telecommunication networks..... | 3 |
+| | 7.1 Key concepts of trust evaluation models..... | 3 |
+| | 7.2 Typical trust evaluation procedures..... | 3 |
+| 8 | Metrics for assessing trust evaluation models for telecommunication networks ..... | 5 |
+| 9 | Approaches for assessing trust evaluation models for telecommunication networks .. | 8 |
+| | 9.1 Binary-level assessment ..... | 9 |
+| | 9.2 Coarse-grained assessment..... | 10 |
+| | 9.3 Fine-grained assessment..... | 11 |
+| | 9.4 Semantic-level assessment ..... | 13 |
+| 10 | Procedures for assessing trust evaluation models for telecommunication networks.... | 14 |
+| | 10.1 Procedures for assessing trust evaluation models using non-semantic
approaches ..... | 14 |
+| | 10.2 Procedures for assessing trust evaluation models using the semantic
approach ..... | 17 |
+| | Appendix I – Overview of existing trust evaluation models ..... | 20 |
+| | I.1 Classical methods ..... | 20 |
+| | I.2 Graph methods..... | 20 |
+| | I.3 Probability methods..... | 21 |
+| | I.4 Machine learning methods ..... | 21 |
+| | Appendix II – Trust model assessment metrics ..... | 23 |
+| | II.1 Comprehensiveness ..... | 23 |
+| | II.2 Usability ..... | 24 |
+| | II.3 Functionality..... | 25 |
+| | II.4 Security..... | 25 |
+| | II.5 Robustness..... | 26 |
+| | II.6 Neutrality..... | 27 |
+| | II.7 Explicability ..... | 28 |
+| | Appendix III – Overview of metrics aggregation methods..... | 29 |
+| | Bibliography..... | 31 |
+
+
+
+# Recommendation ITU-T Y.3260
+
+## Assessing trust evaluation models for telecommunication networks
+
+# 1 Scope
+
+This Recommendation provides a comprehensive set of metrics, recommended approaches and procedures for assessing trust evaluation models for telecommunication networks. The scope of this Recommendation is as follows:
+
+- Overview of trust evaluation models for telecommunication networks;
+- The metrics recommended for assessing trust evaluation models;
+- The approaches recommended for assessing trust evaluation models;
+- The procedures recommended for assessing trust evaluation models.
+
+# 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 Y.3052] Recommendation ITU-T Y.3052 (2017), *Overview of trust provisioning in information and communication technology infrastructures and services*.
+
+# 3 Definitions
+
+## 3.1 Terms defined elsewhere
+
+This Recommendation uses the following terms defined elsewhere:
+
+**3.1.1 access control** [b-ITU-T X.800]: The prevention of unauthorized use of a resource, including the prevention of use of a resource in an unauthorized manner.
+
+**3.1.2 trust** [ITU-T Y.3052]: The measurable belief and/or confidence which represents accumulated value from history and the expecting value for future.
+
+NOTE – Trust is quantitatively and/or qualitatively calculated and measured. Trust is used to evaluate values of entities, value-chains among multiple stakeholders, and human behaviours including decision-making.
+
+**3.1.3 trust index** [b-ITU-T Y.3057]: A composite and relative value that combines multiple trust indicators for representing trust of an entity quantitatively into one benchmark measure.
+
+**3.1.4 trust provisioning** [b-ITU-T Y.3057]: A process to evaluate trust and provide trust-related information (e.g., trust index) to help decision-making of stakeholders through identifying characteristics of entities.
+
+NOTE – Various trust perspectives can be considered separately for trust evaluation.
+
+**3.1.5 user** [b-ITU-R F.1399]: Any entity external to the network which utilizes connections through the network for communication.
+
+## **3.2 Terms defined in this Recommendation**
+
+This Recommendation defines the following term:
+
+**3.2.1 trust evaluation:** A process to evaluate the trustworthiness of a trustee based on relevant events occurring in a certain time period.
+
+# **4 Abbreviations and acronyms**
+
+This Recommendation uses the following abbreviations and acronyms:
+
+AS Application Scenario
+
+HMI Human Machine Interface
+
+LAN Local Area Network
+
+MAN Metropolitan Area Network
+
+TMA Trust Model Assessment
+
+WAN Wide Area Network
+
+# **5 Conventions**
+
+None.
+
+# **6 Motivations to assess trust evaluation models for telecommunication networks**
+
+With the rapid development of telecommunication technology, the physical world and digital world have become connected and integrated. The relationships among people and the connections among things have become more and more complex, and new threats and challenges are emerging. Billions of end-devices, such as sensors, cell phones, and new human machine interfaces (HMIs) will form the basic stratum of such threats. On the networks side, the open interfaces, heterogeneous networks, and millions of untrusted dynamic specialized sub-networks will redefine the arena for attacks. Trust is considered a promising approach to tackle these new challenges.
+
+To tackle such challenges and build a trustworthy telecommunication network, it is considered that trust [ITU-T Y.3052] needs to be evaluated across end-devices, access networks, and core networks. As a result, many trust evaluation models have been proposed. However, these trust evaluation models are proposed using different approaches, making it difficult to compare and analyse their performance. Thus, one motivation of this Recommendation is a compelling need to evaluate the design and performance of trust evaluation models, as well as the approaches and corresponding metrics which can be applied. Other motivations of this Recommendation can be summarized as follows: (i) Lack of commonly agreed metrics and criteria for assessing trust evaluation models. In existing works, researchers usually evaluate the performance of their developed trust evaluation models based on their own metrics. However, these metrics are often non-comprehensive and are usually reduced to a specific scope. For instance, metrics such as security, robustness, and usability are often ignored in the evaluation. Hence, a complete and comprehensive set of criteria is needed for the evaluation and refinement of a trust model, which will greatly benefit both the trust model developers and its users. (ii) Lack of guiding and systematic methodologies for assessing trust evaluation models. In existing works, researchers usually evaluate the performance of their developed trust evaluation models using their own methods. However, these approaches are usually dedicated to a specific trust model for a specific scenario, and thus cannot be directly applied to assess other trust models developed for other scenarios. This is due to the fact that different trust models may perform differently in different circumstances. Hence, a set of systematic methodologies for assessing trust evaluation models is needed.
+
+Considering these motivations there is a compelling need to assess trust evaluation models comprising a set of comprehensive metrics, systematic approaches, and corresponding procedures. This Recommendation will serve as a guide for mobile network operators to compare and select suitable trust evaluation models for their networks and will also benefit researchers and developers when designing new trust evaluation models, as it provides a basic guideline for researchers and developers to decide which requirements their models should satisfy. Moreover, it can be used to identify the advantages and shortcomings of an existing trust evaluation model, and developers can then make refinements based on the feedback provided by this Recommendation. Overall, this Recommendation will significantly facilitate the comparison and analysis of different trust evaluation models, lower the barrier for choosing trust models for different scenarios, and encourage the development of high-quality trust models.
+
+# **7 Overview of trust evaluation models for telecommunication networks**
+
+## **7.1 Key concepts of trust evaluation models**
+
+A trust evaluation model is used by a trustor to evaluate the trustworthiness of a trustee based on relevant events occurring in a finite time period. The relevant events are input to the trust evaluation model in the form of data, and an output known as the evaluation result is then produced. This evaluation result of the trust evaluation model reflects the overall assessment and quantification of trustworthiness of the trustee during a specific amount of time. There are two types of key trust information defined in trust modelling: trust information and trust index.
+
+- **Trust information:** Trust information in a trust evaluation model is specific to information distilled from various data of a trustee. This is produced after data is input for result generation in a trust evaluation model. Trust information should reflect current trust properties and features of the trustee. The comprehensiveness of trust information is an important factor impacting the evaluation result, and thus trust information should cover characteristics of the trustee as much as possible from both a direct trust aspect and an indirect trust aspect. Direct trust and indirect trust are specified in [ITU-T Y.3052]. The definitions of trust attributes and trust indicators specified in [ITU-T Y.3052] could also be referred to in the implementation.
+- **Trust index:** Trust index defined in [b-ITU-T Y.3057] is a composite and relative value that combines multiple trust indicators for representing trust of an entity quantitatively into one benchmark measure. It is a value representing the overall trustworthiness of an entity given by the trust evaluation model. In a trust evaluation model, the trust index reflects the trustor's trust of the current trustee in a quantitative measure based on the events happening in a specific period of time. Trust index is time-varying and it will change with time depending on up-to-date trust information. Different trust evaluation models may have different mechanisms to accumulate the trust information, and thus there is no specific requirement for the form of the trust index, as long as it presents the characteristics of trust defined in [ITU-T Y.3052].
+
+## **7.2 Typical trust evaluation procedures**
+
+As shown in Figure 1, the typical procedure of trust modelling between two entities involves data collection, data processing, trust calculation, and decision-making. The data collection phase requires the trustor to gather data from the trustee. Collected data will be processed into trust information in the data processing phase. The trust calculation phase will then calculate the trust index based on the trust information, and the result will be used to support making decisions in the decision-making phase.
+
+
+
+Figure 1 – Typical trust evaluation procedures. The diagram illustrates the process of trust evaluation between a Trustor and a Trustee. At the top, a dashed box labeled 'Trust modelling' contains a 'Trustor' icon and a box listing 'Knowledge', 'Experience', and 'Reputation'. A 'Collect' arrow points from the Trustor to this box. Below this, a yellow-bordered process flow includes 'Data collection', 'Data sets', 'Data processing', 'Trust information', 'Trust calculation', 'Trust index', and 'Decision making'. An arrow labeled 'Data sets' connects 'Data collection' to 'Data processing'. An arrow labeled 'Trust information' connects 'Data processing' to 'Trust calculation'. An arrow labeled 'Trust index' connects 'Trust calculation' to 'Decision making'. A dashed arrow labeled 'Interaction' connects the Trustor and Trustee. A solid arrow labeled 'Action' points from the Trustee back to the Trustor. The 'Trust modelling' box also feeds into the 'Data sets' stage. The reference 'Y.3260(24)' is at the bottom right.
+
+**Figure 1 – Typical trust evaluation procedures**
+
+#### 7.2.1 Data collection
+
+Data collection is to gather relevant data from the trustee. From [ITU-T Y.3052], three main sources of trust information should be considered when a trustor collects data of a trustee: knowledge, experience, and reputation.
+
+- **Knowledge:** Knowledge refers to the trustor's own understanding of the trustee's characteristics and features. Knowledge could provide direct trust information when evaluating trust, since it could be gained from the primary data of the trustee even before the first interaction [ITU-T Y.3052].
+- **Experience:** Experience, which is defined in [ITU-T Y.3052], refers to the trustor's insight and personal observation about previous interactions with the trustee. It is achieved by accumulating the state of interactions among entities over time.
+- **Reputation:** Reputation is a public assessment of the trustor with respect to the prior behaviour and performance of the trustee. Reputation can be evaluated based on the accumulated experience of trustors about the trustee. To acquire trust information based on the reputation of a trustee, two kinds of information require examination: a) previous trust transactions from all entities to the trustee; b) the relationship between a trustor and the trustee.
+
+Other data collection requirements specified in [ITU-T Y.3052] are also applicable. Additionally, data should be collected with the supervision of relevant policies and regulations. Integrity, confidentiality and security of data should be achieved, and mechanisms protecting the trustee's privacy should be followed.
+
+#### 7.2.2 Data processing
+
+Data processing is to produce valid trust information with data gathered from a trustee for further trust calculation. The requirement of trust information depends on the trust evaluation model, but in general trust information should be concise, comprehensive, and could describe the characteristics of the trustee from both a direct trust perspective and an indirect trust perspective. The integrity and confidentiality of data and trust information should be guaranteed during this process.
+
+#### 7.2.3 Trust calculation
+
+Trust calculation is to calculate the trust index of a trustee with trust information from the data processing phase. Such a value is an accumulation of trust information in a specific time interval. Time should be considered in the calculation to reflect the dynamicity of trust. Both direct trust information and indirect trust information should be involved, but they may have different weights in the calculation depending on the calculation scheme and implemented trust modelling approaches. The validity of a trust index should be limited by time, and the trust index should reflect both characteristics of the trustee and characteristics of the trust in a quantitative measure.
+
+#### 7.2.4 Decision-making
+
+Decision-making, which is the last stage of trust modelling, usually happens after the trust index of the trustee is generated from the trust calculation. The target of decision-making is to take a certain action against the trustee, usually in the form of access control, resource allocation, or policy enforcement. However, it is worth pointing out that the trust modelling is an on-going process. After the decision-making, the trustor needs to continually re-evaluate the trust index of the trustee.
+
+# 8 Metrics for assessing trust evaluation models for telecommunication networks
+
+Metrics are the criteria or indicators used to quantitatively or qualitatively measure the trustworthiness of a trust evaluation model. Each metric will assess one aspect of a trust model, and the metrics will reflect the trust model's performance. Metrics will play an important role in the subsequent trust model evaluation process. However, existing metrics for trust model evaluation are often very limited and dedicated to specific scenarios. Some important metrics are often ignored during the model evaluation process, such as security, robustness and usability, which may lead to unfair comparison between two trust models. Therefore, in order to facilitate fair model comparisons and optimal model selection, it is indispensable to define a set of complete and comprehensive metrics that can be widely applied to assess various trust evaluation models. For this reason, as shown in Figure 2, a comprehensive set of metrics for trust model evaluation are defined, which cover seven aspects: comprehensiveness, usability, functionality, security, robustness, neutrality, and explicability. In each aspect, some related detailed metrics are given, which suggest the targets that trust evaluation models should hit, and potential challenges that trust evaluation models should address. Definitions and details of the metrics will be given in the appendices.
+
+| | | | | | | |
+|--------------------------|------------------------------------------------------------------------------------------------------------------------------------|------------------------------------------------------------------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------|---------------------------------------------------------------------------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------|
+| Comprehensiveness | Dynamicity
Captures variation of trust over time | Asymmetry
Trust formed between trustor and trustee should be directional | Transitivity
Trustor's preceding trust in the recommender should imply a trust in the Recommendation | Context awareness
Considers prevailing contextual features in trust management | Imbalance
Trust should be easy to lose but hard to gain | Subjectivity
Trust management considers nodes' preferences and features |
+| Usability | Computational efficiency
Resources required should meet constraints on devices | | Data usability
Variables should be obtained from the environment either directly or via additional non-intensive calculations | | Node diversity
Able to provide a usable trust value for all types of nodes | Network diversity
Able to provide a usable trust value regardless of the types of the network |
+| Functionality | Trust-based access control
Provides corresponding access rights based on different trust values or trust levels | | Service-oriented access control
Tailors level of security in trust management system to the needs of the user or device | | Dynamic access rights management
Revokes on-going access rights of a user if its trust value is below a certain threshold | |
+| Security | Privacy
Protects users' private data and sensitive information | Confidentiality
Avoids data leakage and prevents unauthorized access | Availability
Usable whenever needed under different network conditions | Integrity
Assures completeness, authenticity as well as accuracy of data and code | Non-repudiation
Able to hold nodes responsible for their actions | Authenticity
Users' identities should be verifiable |
+| Robustness | Network disturbance
Trust model's functions and service should be available even when network disturbances occur | | Propagation errors
Able to account for propagation errors in the network and adjust trust values accordingly | | Cold start problem
Able to address the problem of lack of sufficient information to indicate a new node's trustworthiness of when it is being added to the network | |
+| Neutrality | Non-discrimination
Does not discriminate against nodes based on certain sensitive attributes | | Non-bias
Mitigates bias in both dataset and algorithm | | Transparency
The trust evaluation process should be accessible and transparent for auditing | |
+| Explicability | Perceivability
Provides model inspection by textual or visual artifacts or extracts representative instances as examples | | Simplicity/Decomposability
The model should embody simplicity, and the evaluation function can be decomposed into a sum of components | | Feature relevance
Explains by investigating the influence of each input variable | Causality
Represents the level of causal reasoning that human can achieve given model's self-explanation |
+
+Y.3260(24)
+
+**Figure 2 – Metrics for assessing trust evaluation models**
+
+1. Comprehensiveness
+ - a. Dynamicity: The model can update the trust index of devices periodically. For example, the trust indexes of sensor nodes can change dynamically based on their
+
+- direct observation of each other's actions, such as forwarding packets or dropping packets in a communication network. The trust indexes can also change based on the feedback from other nodes in the network that have interacted with the same nodes. The trust indexes can also change based on the context information of the network, such as the network topology, the network traffic, or the network security.
+- b. Asymmetry: The trust formed by the model should be directional. For example, the trust relationship between the sensor nodes and the base station is asymmetric, meaning that the base station trusts the sensor nodes more than the sensor nodes trust the base station. This is because the base station can verify the data from the sensor nodes using cryptographic techniques, while the sensor nodes cannot verify the commands from the base station due to resource constraints.
+ - c. Transitivity: The trust indexes should be able to be transferrable. For example, suppose a user trusts a router in a communication network A, and the router trusts a server in another communication network B. The user does not know the server directly, but the user can infer how much the user can trust the server in network B based on transitivity. However, the trust index of the user for the server may fade as it passes through the chain of trust from network A to network B.
+ - d. Context awareness: The model should consider the context features in trust management. For example, the router considers its own context, such as location, time, and activity, to adjust its trust threshold. If the router is in an emergency situation, it may lower its trust threshold and communicate with the switch even if it has a low trust score. On the other hand, if the router is in a normal situation, it may raise its trust threshold and communicate with the switch only if it has a high trust score.
+ - e. Imbalance: Trust captured by the model should be easy to lose and hard to gain. For example, once the data packet received by a cellular device is of poor quality, the trust index of the receiving cellular device to the transmitting cellular device would be decreased dramatically. However, the trust index can only increase a little with respect to a high number of data transmissions in good quality.
+ - f. Subjectivity: The model should consider the subjective preference and the features of the devices when evaluating trust, such as sensors' preference to specific sources or networks, device capabilities, device reputation, or device location. For example, a device user may prefer to trust a source or a network that has similar interests or values, or a device may trust an entity that has higher capabilities, reputation, or proximity. Different users may have different expectations and preferences about the quality and security of the data transmission. For example, some users may value speed over accuracy, while others may value privacy over convenience. Some users may trust certain devices or networks more than others, based on their reputation, experience, or recommendation. Therefore, the trust in a telecommunication network is not a fixed or objective value, but a dynamic and subjective perception that depends on various factors and contexts.
+
+### 2. Usability
+
+- a. Computational efficiency: Resources required should meet the constraints of devices. The trust evaluation of a service may require a lot of computational resources, such as memory, central processing unit (CPU), or bandwidth. For example, a resource may need to collect, store, and process a large amount of feedback or reputation information from other resources. If the computational resource is overloaded in the trust evaluation process, the resource may not be able to detect the malicious attacks or provide the service in time data.
+- b. Data usability: The model should consider the difficulty of obtaining the data. The trust index of an entity may depend on multiple parameters, such as signal strength, packet
+
+loss, delay, throughput, or energy consumption. Therefore, devices need to consider the difficulty of obtaining the data in trust evaluation.
+
+- c. Node diversity: The model should be available for all types of nodes, such as routers, switches, servers, clients, modems, access points and other network-connected entities.
+- d. Network diversity: The model should be available for all types of networks, such as local area networks (LANs), metropolitan area networks (MANs), wide area networks (WANs), Wireless networks, and Inter networks (Internet).
+
+### 3. Functionality
+
+- a. Trust-based access control [b-ISO/IEC 10027]: The model should control the access rights of devices according to the trust index or trust levels. For example, the trust index or level determines the access rights of the device, such as which network functions it can communicate with, what data it can access or transmit, and how much bandwidth it can use. The trust index or level is also dynamic and updated continuously based on the device's performance and feedback.
+- b. Service-oriented access control [b-ISO/IEC 10027]: The model should have the ability to give the device access rights according to its service requests. For example, the trust model should have the ability to give the client access rights according to its service request, such as read-only, write-only, or full access, and for a specific time period.
+- c. Dynamic access rights management: The model should evaluate the trust indexes of the cellular device dynamically, and check the trust level of the cellular device frequently. When a cellular device is evaluated as being under the trust threshold, the model would revoke the access rights of the cellular device to other devices or systems.
+
+### 4. Security
+
+- a. Privacy: The model should protect users' private data and sensitive information, which means the model should have the protection mechanism to assure the users' private information would not be leaked or abused during the information exchange in communication networks. For example, a trust model should require users to authenticate themselves before they are granted access to sensitive data. This authentication process can involve the use of passwords, biometric data, or other forms of identification that are unique to each user. Once a user has been authenticated, they are granted access to the data that they are authorized to view.
+- b. Confidentiality: The model should avoid data leakage and prevent unauthorized access, which means the model should have an access control mechanism to ensure that access to resources such as hardware components, sensor data or private information are only granted to authorized actors, whether they are users or processes.
+- c. Availability: The model should always be usable whenever needed under different communication network conditions. The trust evaluation model should adapt to different communication network conditions such as bandwidth, latency, and congestion.
+- d. Integrity: The model should assure the completeness and authenticity as well as the accuracy of data. For example, a large number of sensor nodes in a communication network may collect and transmit data to a base station. The data may be sensitive or critical, such as environmental monitoring, military surveillance, health care, etc. The model should detect and isolate malicious nodes that provide incomplete, false or inaccurate data and ensure the integrity of data collection and transmission.
+- e. Non-repudiation: The model should be able to hold nodes responsible for their actions by labelling each action with the information of the nodes' initial identity, which can be verified by blockchain.
+
+- f. Authenticity: The users' identities of devices should be verifiable. For example, the model should be able to certify the transmitting routers and receiving routers and their identities during the data transmission.
+
+### 5. Robustness
+
+- a. Network disturbance: The model should be available when power supply failures of network devices, noise, transmission errors, signal attenuation, etc. occur in the communication networks. Additionally, the above causes should not influence the trust evaluation of the transmitting routers in the network.
+- b. Propagation errors: The model should consider propagation errors caused by noise, signal attenuation, distortion and interference in the network, and this should not affect the trust evaluation of the transmitting routers in the network.
+- c. Cold start problem: The model should be able to address the problem of lack of sufficient information to indicate a new node's trustworthiness when it is being added to the communication network. For example, the model can use techniques such as regular equivalence, feedback ratings, etc. to overcome cold start problems when a new sensor is added into the network.
+
+### 6. Neutrality
+
+- a. Non-discrimination: The model should not discriminate against nodes based on certain sensitive attributes. It should aim to ensure that all network entities, such as routers, sensors, base stations or any other mobile devices are treated equally and fairly in terms of trust evaluation, regardless of their characteristics or attributes, such as type, capability, domain, owner, etc.
+- b. Non-bias: The model should detect and mitigate the bias of datasets and algorithms, which means the information overall should be evaluated in trust assessment to mitigate the cognitive bias impact.
+- c. Transparency: The trust evaluation process should be transparent in the processing, data handling, algorithm, etc. during the trust evaluation to all network entities, such as routers, sensors, base stations or any other mobile devices.
+
+### 7. Explicability
+
+- a. Perceivability: The model should provide model inspection by for example textual or visual artifact representative instances.
+- b. Simplicity/decomposability: The model should embody simplicity, and the evaluation function that can be decomposed into a sum of components.
+- c. Future relevance: The model should be explained by investigating the influence of each input variable.
+- d. Causality: The model should represent the level of causal reasoning that humans can achieve given the model's self-explanation.
+
+# 9 Approaches for assessing trust evaluation models for telecommunication networks
+
+In this Recommendation, four different approaches for assessing the quality of a trust evaluation model are introduced. These approaches mainly differ in terms of granularity of assessment with the aim of suiting the needs of different use cases. The recommended approaches are discussed in clauses 9.1 to 9.4.
+
+
+
+Y.3260(24)
+
+Figure 3: Four levels of evaluation approaches. A pyramid diagram with four levels: Semantic-level (top, blue), Fine-grained (green), Coarse-grained (yellow), and Binary (bottom, orange). Arrows point from each level to a corresponding box on the right. The Semantic-level box contains 'Goal satisfied or not? Why not? How to improve?'. The Fine-grained box contains 'Quality scores, continuous, e.g., QS 0-100'. The Coarse-grained box contains 'Quality levels, discrete, e.g., level 1-5'. The Binary box contains 'Good or bad, binary, e.g., 1 or 0'. The reference Y.3260(24) is at the bottom right.
+
+**Figure 3 – Four levels of evaluation approaches**
+
+Figure 3 shows the four levels of evaluation approaches, comprising binary level, coarse-grained level, fine-grained level and semantic level approaches. Their assessments range from coarse to fine, and the semantic level assessment approach offers an intelligent way to evaluate the trust model semantically. The applicability in different use cases and their associated strengths and weaknesses will be discussed as in this clause.
+
+## 9.1 Binary-level assessment
+
+Binary assessment of the quality of a trust evaluation model aims to output a binary evaluation of the suitability of the model for its targeted application scenario. To accomplish this, the metrics discussed in clause 8, including all the sub-criteria within each metric, should be given a binary evaluation on whether they have been fulfilled. The simplistic nature of the result generated by the binary-level assessment is well suited for quick or preliminary assessment of the quality of trust models.
+
+The recommended key requirements for binary-level assessment are as follows:
+
+- Appropriate binary set of values should be clearly defined: 'true' vs 'false', 'good' vs 'bad', '0' vs '1', etc.
+- A binary output should be generated at each level of the assessment, from the sub-criteria level to the final output.
+- Any specific implementation for aggregating values to generate the next level's value should be clearly defined, such as the majority rule, or the k out of n rule.
+
+| Metric | Sub-criteria | | | | | | Metric assessment | Overall assessment | | | |
+|-------------------|----------------------------------|-----------------|-------------------------------|---------------|-------------------|-----------------------------|------------------------------|---------------------------|--|--|--|
+| Comprehensiveness | Dynamicity | Asymmetric | Transitivity | Context aware | Imbalance | Subjective | ✓ | ✓ | | | |
+| | ✓ | ✓ | ✓ | | | | | | | | |
+| Usability | Computational efficiency | | Data usability | | Device diversity | | Usable in different networks | | | | |
+| | ✓ | | ✓ | | | | | | | | |
+| Functionality | Corresponding access | | Service oriented data control | | | Continuity of access rights | | | | | |
+| | ✓ | | ✓ | | | | | | | | |
+| Security | Privacy | Confidentiality | Availability | Transparency | Integrity | Non-repudiation | Authenticity | | | | |
+| | ✓ | ✓ | ✓ | ✓ | | | | | | | |
+| Robustness | Network disturbance | | Propagation errors | | | Cold start problem | | | | | |
+| | ✓ | | | | | | | | | | |
+| Neutrality | No discrimination/Non-subjective | | No bias | | | Transparency | | | | | |
+| | ✓ | | | | | | | | | | |
+| Explicability | Visualization | | Simplicity/decomposition | | Feature relevance | | Explanation by example | | | | |
+| | ✓ | | | | | | | | | | |
+
+Y.3260(24)
+
+**Figure 4 – Sample binary-level assessment**
+
+Figure 4 presents an example for the binary assessment where a majority rule (a criterion is deemed satisfied if at least half of its sub-criteria are satisfied) is adopted. For the 'comprehensiveness' metric, half of the sub-criteria are satisfied as indicated by the ticks, hence the metric is also considered satisfied. On the other hand, the 'robustness' metric only has a third of its sub-criteria satisfied, so it is not considered to be a satisfied metric. Extending this to all the metrics, as 4 out of the 7 metrics are satisfied, the model in assessment is considered satisfactory under the binary assessment.
+
+The strengths of binary-level assessment can be seen very intuitively: it is the simplest approach to clearly present whether the trust evaluation model is good or not. The simple outputs require the smallest resources and take least time to complete for the assessment process.
+
+However, binary outputs can result in the loss of nuance or detail that may be relevant. For example, even in cases where the model barely fulfils most of the metrics, the trust evaluation model may not be as perfect as the results suggest because even if all the satisfied metrics are just up to the standard score it still shows 'good' outputs. A binary evaluation of each sub-criteria leaves a lot of room for subjective interpretation on edge cases which makes it prone to bias from the assessor. Also, because this approach can only differentiate whether the model is good or not, it cannot compare different models. Therefore, it is appropriate to treat this method as a first level for quick preliminary assessment.
+
+### 9.2 Coarse-grained assessment
+
+Coarse-grained assessment relies on an ordinal scale to evaluate the trust model, based on the standard metrics given in clause 8. It aims to strike a balance between the complexity and the ease of interpretation for the assessment of a trust model.
+
+The rubrics used in the binary assessment given in clause 9.1 can be adapted here by converting the assessment columns from binary into a suitable scale instead. The specific ratings used in the scale can be varied, as long as they are clear in meaning and can be differentiated from each other.
+
+The recommended key requirements for coarse-grained assessment are as follows:
+
+- An ordered scale system should be clearly defined to rate each sub-criterion and metric, e.g., a 5-level scale system: bad, poor, mediocre, good, excellent.
+- A set of guidelines for each rating in the scale should be established to clearly distinguish among different levels.
+- The rules to aggregate the ratings of the sub-criteria in each specific metric, and aggregate the ratings of each metric should be clearly defined in order to generate an overall rating.
+
+| Metric | Sub-criteria | | | | | | Metric assessment | Overall assessment | |
+|-------------------|----------------------------------|-----------------|-------------------------------|---------------|-----------------------------|-----------------|--------------------------|---------------------------|--|
+| Comprehensiveness | Dynamicity | Asymmetric | Transitivity | Context aware | Imbalance | Subjective | Mediocre | Mediocre | |
+| | Mediocre | Bad | Poor | Mediocre | Poor | Good | | | |
+| Usability | Computational efficiency | | Data usability | | Device diversity | | Good | | |
+| | Excellent | | Good | | Good | | | | |
+| Functionality | Corresponding access | | Service oriented data control | | Continuity of access rights | | Good | | |
+| | Mediocre | | Excellent | | Good | | | | |
+| Security | Privacy | Confidentiality | Availability | Transparency | Integrity | Non-repudiation | Authenticity | | |
+| | Excellent | Mediocre | Good | Mediocre | Mediocre | Mediocre | Bad | | |
+| Robustness | Network disturbance | | Propagation errors | | Cold start problem | | Poor | | |
+| | Bad | | Poor | | Good | | | | |
+| Neutrality | No discrimination/Non-subjective | | No bias | | Transparency | | Good | | |
+| | Good | | Mediocre | | Excellent | | | | |
+| Explicability | Visualization | | Simplicity/decomposition | | Feature relevance | | Mediocre | | |
+| | Good | | Good | | Mediocre | | | | |
+
+Scale: 5 – Excellent 4 – Good 3 – Mediocre 2 – Poor 1 – Bad
+
+Y.3260(24)
+
+**Figure 5 – Sample coarse-grained assessment**
+
+Figure 5 presents an example of the coarse-grained assessment. The method adopted to aggregate values is to assign an integer numerical value to each sub-criterion, averaging the values and rounding off to the nearest integer to obtain the corresponding rating for the metric. Then, the procedure is repeated to aggregate all the metrics to reach an overall assessment.
+
+The coarse-grained level approach measures the metrics' scores more specifically than the binary level approach. For example, a binary-level approach can only distinguish the entities as "trustworthy" or "untrustworthy", but cannot measure which entity is more trustworthy among trusted entities or which is less trustworthy among untrustworthy entities. The coarse-level approach provides a way to compare the trustworthiness with more granularity. In addition, the coarse-level approach is still relatively simple and saves resources during assessment.
+
+### 9.3 Fine-grained assessment
+
+Fine-grained assessment provides an even more detailed rating of the quality of a trust model. Fine-grained assessment is able to establish a more concrete relationship between the scores and the metrics. Particularly, for the fine-grained assessment, the evaluation values can be obtained through mathematical modelling of each sub-criterion. The exact range of the scale used for the assessment can vary, as long as it spans a continuous range and can be used to consistently calculate the score of the metric that the criteria belong to. The exact relation used to calculate the final score may also change depending on the rationale.
+
+The recommended key requirements for fine-grained assessment are as follows:
+
+- A continuous scale (such as from 0 to 100, or from 0 to 1) should be used to assess the trust model's quality in each sub-criterion.
+- A set of guidelines or formulas for computing ratings in the scale should be clearly defined.
+- A clear rule should be defined to aggregate each metric's sub-criteria to obtain the rating for that metric.
+- A clear rule should be defined to aggregate each metric to obtain the overall rating.
+
+| Metric | Sub-criteria | | | | | | Metric assessment | Metric priority | Overall assessment | |
+|-------------------|----------------------------------|-----------------|-------------------------------|---------------|-----------------------------|-----------------|--------------------------|------------------------|---------------------------|--|
+| Comprehensiveness | Dynamicity | Asymmetric | Transitivity | Context aware | Imbalance | Subjective | 55.83 | 1 | 56.41 | |
+| | 60 | 75 | 81 | 63 | 74 | 52 | | | | |
+| Usability | Computational efficiency | | Data usability | | Device diversity | | 60.50 | 2 | | |
+| | 53 | | 63 | | 67 | | | | | |
+| Functionality | Corresponding access | | Service oriented data control | | Continuity of access rights | | 65.33 | 3 | | |
+| | 74 | | 36 | | 86 | | | | | |
+| Security | Privacy | Confidentiality | Availability | Transparency | Integrity | Non-repudiation | 37.29 | 4 | | |
+| | 39 | 31 | 44 | 53 | 48 | 27 | | | | |
+| Robustness | Network disturbance | | Propagation errors | | Cold start problem | | 48.33 | 5 | | |
+| | 54 | | 45 | | 46 | | | | | |
+| Neutrality | No discrimination/Non-subjective | | No bias | | Transparency | | 80.67 | 6 | | |
+| | 85 | | 81 | | 76 | | | | | |
+| Explicability | Visualization | | Simplicity/decomposition | | Feature relevance | | 43.50 | 7 | | |
+| | 48 | | 44 | | 35 | | | | | |
+
+Y.3260(24)
+
+**Figure 6 – Sample fine-grained assessment**
+
+Figure 6 presents an example of the fine-grained assessment. Given that the scores for the sub-criteria in the 'comprehensiveness' metric are 60, 75, 81, 63, 74, and 52 respectively, the score for the 'comprehensiveness' metric would be the average score, which is 55.83. The importance of each metric to the overall assessment is then assessed, and each metric is given a priority value. The overall assessed score is then the weighted averaged of all the metrics. Given the relative priorities shown above, the metric scores would be aggregated using the formula
+
+$$[55.83*(8-1) + 60.5*(8-2) + 65.33*(8-3) + \dots + 43.5*(8-7)]/[(8-1) + (8-2) + (8-3) + \dots + (8-7)]$$
+
+giving the overall score 56.41.
+
+Fine-grained assessment provides an objective method of determining the overall performance of a trust model, as every metric must be given a clear score according to predetermined rubrics. It can also capture subtle differences or variations in quality that a coarse-grained approach might miss, and it allows for more customized and flexible evaluation criteria that suit the specific task or goal. Since the overall score will be aggregated based on fixed formulas, the consistency of the total score is ensured. Additionally, the process is fast and consistent, and more details are retained.
+
+While the approach provides more precise results, it can be more complex and time-consuming to implement and apply than a coarse-grained approach or a binary level approach. Compared to the intuitive output such as "good" vs "excellent" or "trustworthy" vs "untrustworthy", the fine-grained assessment may require more domain knowledge and expertise to interpret and use the results.
+
+## 9.4 Semantic-level assessment
+
+Semantic-level assessment of the quality of a trust model will not only provide the overall evaluation, but also point out the strengths or weaknesses contributing to the evaluation and, recommendations for improvement or change will also be generated. Semantic-level assessment is more complex and more intelligent, and may have different types of implementation formation.
+
+
+
+```
+
+graph TD
+ AS[Application scenario] --> EM1[Extraction module]
+ H[Human] --> EM2[Extraction module]
+ T[Things] --> EM2
+ EM1 -- Extract --> C1[Characteristics]
+ EM2 -- Extract --> C2[Characteristics]
+ C1 --> FM[Fusion module]
+ C2 --> FM
+ FM -- "Specify the metrics" --> MSM[Metrics storage module]
+ MSM -- "Metric-specific testbed requirement: Attack models, sub-metrics, etc." --> FM
+ FM -- Generate --> TB[Testbed]
+ subgraph TB
+ A[Agents] -- Perform --> AC[Actions]
+ AC -- "Acts on / Affect" --> S[States]
+ E[Environment] -- Generate --> S
+ end
+ TB --> PM[Parsing module]
+ PM --> ER[Evaluation report]
+ ER -- Feedback --> TM[Trust models]
+ ER --> FM
+
+```
+
+Figure 7 – Semantic assessment framework diagram. The diagram illustrates the flow of information in a semantic assessment framework. It starts with 'Application scenario' and 'Human'/'Things' inputs, which go through 'Extraction module' to produce 'Characteristics'. These are then processed by a 'Fusion module'. The 'Fusion module' interacts with a 'Metrics storage module' (containing Comprehensiveness, Usability, Functionality, Security, Robustness, Neutrality, and Explicability) to 'Specify the metrics' and receive a 'Metric-specific testbed requirement: Attack models, sub-metrics, etc.'. The 'Fusion module' then 'Generate' a 'Testbed'. The 'Testbed' contains 'Agents' and 'Environment'. 'Agents' 'Perform' 'Actions', which 'Affect' 'States' in the 'Environment'. The 'Environment' also 'Generate' 'States'. The 'Testbed' outputs to a 'Parsing module', which produces an 'Evaluation report'. This report is used for 'Feedback' to 'Trust models' and also feeds back into the 'Fusion module'.
+
+Figure 7 – Semantic assessment framework
+
+The basic framework of semantic-level methods is shown in Figure 7. The key components of the framework are discussed as follows:
+
+**User input:** The foundation of the framework is the user [b-ITU-R F.1399] input information. It can be divided into two main categories: application scenario and assessed entities. Before evaluating a trust model, the user should first define the specific application scenario where the trust model used. The evaluated entities, including humans and things should also be specified. Then the input settings will be processed by an extraction module to extract the characteristics. In some cases, the user may be not an expert in the domain, which leads to the difficulty of describing clear and accurate information about the input scenario. The extraction module can be simplified as an application scenario (AS) module to offer existing choices of the application scenarios.
+
+**Fusion module:** The fusion module aggregates the characteristics of the application scenario and assessed entities to deploy the environment of the testbed. The metric-specified testbed requirement is also fused in this module.
+
+**Metrics storage module:** The metrics are stored and retrieved in this module. The fusion module sends the request to the metrics storage module and it specifies the environment deployment settings of the specific metric according to the extracted characteristics. Then the metrics storage module will return the metric-specified requirement of the testbed to the fusion module to combine all the settings. In more advanced designs, the metrics are not limited to the categories mentioned before. The characteristics extracted may relate to some evaluation metrics that are not covered in the existing storage module. Therefore, a metrics generation module is introduced to generate new metrics learned from the testing characteristics and adds the new metrics to the metrics storage module according to some rules.
+
+**Testbed:** The core simulation tests take place in the testbed module. After the fusion module combines the users' requirement and the metric-specified requirement, the settings will be sent to
+
+the testbed to generate agents and the environment. The agents perform actions to act on the environment, while the environment generates states to affect the agents at the same time. The testing process is similar to a reinforcement learning, which is a dynamic evolution process. The evaluation process is actually performed in this component. The trust model is directly input in the testbed, and after evaluation, the overall assessment result will be sent back.
+
+**Trust model and evaluation report:** The trust model is the assessed objective of the evaluation framework. It is input into the testbed and evaluated, then the assessment result is returned to the parsing module to be parsed to an evaluation report. In an automated self-improvement mechanism, the report is sent to the trust model directly. The trust model can improve itself repeatedly through every cycle of the evaluation. In other cases, the report should be sent to the user first to get permission to perform optimization or not. This mechanism is relatively less automated, but it reserves the participation of the user's subjective judgment and the specific requirement of application.
+
+Figure 7 shows the major components of the semantic-level evaluation framework. The basic idea of the proposed framework is: the trust model assessment (TMA) system obtains the evaluation metric (or metrics), the information of the application scenario where the trust model will be deployed, and the information of the entity that the trust model will be applied to. Based on this information, the TMA system generates the test environment, i.e., an application environment simulating where the entity will be. Then, the TMA system calls the trust model which is the model to be assessed, and uses this trust model to evaluate the trust index of the entity. With the obtained evaluation result/results (which correspond(s) to one or more evaluation metrics), TMA assesses the trust model and obtains the trust model assessment result/results, which reflect(s) the trust evaluation capability of the trust model within the dimension of the used metric(s). The semantic level method can understand the users' requirements, and the methods most concerned with the problem have the highest ability to process the information. In addition, the evaluation report is easy to understand semantically due to the processing of the intelligent module.
+
+Different levels of assessment approaches have different characteristics, and they all have their own strengths and weaknesses. The selection of methods should be based on the actual scenario requirement, and the computing resources should also be considered comprehensively.
+
+# **10 Procedures for assessing trust evaluation models for telecommunication networks**
+
+## **10.1 Procedures for assessing trust evaluation models using non-semantic approaches**
+
+The general procedures for assessing trust evaluation models using non-semantic approaches are the same, and the procedures are shown in Figure 8:
+
+
+
+```
+
+sequenceDiagram
+ participant User
+ participant Model evaluator
+ participant Evaluation metrics
+ participant Trust model
+
+ User->>Model evaluator: 1. Send assessment parameters (Test parameters, test environment, test detail)
+ Model evaluator->>Model evaluator: 2. Begin trust model assessment
+ Model evaluator->>Evaluation metrics: 3. Retrieve metric for testing
+ Evaluation metrics-->>Model evaluator: Metric
+ Model evaluator->>Model evaluator: 4. Begin metric assessment
+ Model evaluator->>Evaluation metrics: 5. Retrieve sub-criterion for testing
+ Evaluation metrics-->>Model evaluator: Sub-criterion
+ Model evaluator->>Model evaluator: 6. Begin sub-criterion assessment
+ Model evaluator->>Trust model: 7. Pass evaluation parameters (Test parameters, test environment, sub-criterion)
+ Trust model->>Trust model: 8. Run tests and log performance metrics
+ Trust model->>Model evaluator: 9. Send performance data
+ Model evaluator->>Model evaluator: 10. Evaluate performance of trust model with respect to sub-criterion (Sub-criterion, performance data)
+ Model evaluator->>Model evaluator: 12. Evaluate performance of trust model with respect to metric (Metric, sub-criterion assessment)
+ Model evaluator->>Model evaluator: 14. Evaluate performance of trust model based on overall evaluation metrics (Metric assessments)
+ Model evaluator->>User: 15. Presents overall assessment of trust model
+
+```
+
+Y.3260(24)
+
+Sequence diagram showing the sequential evaluation process between User, Model evaluator, Evaluation metrics, and Trust model.
+
+**Figure 8 – Sequential evaluation process**
+
+The steps outlined in Figure 8 can be broken down as follows:
+
+0. The user first determines and prepares their test environment, including the test parameters, as well as the level of detail in the assessment they wish to achieve.
+1. These parameters are then passed by the user into the model evaluator.
+2. The model evaluator begins the trust model assessment.
+3. The model evaluator first retrieves a metric it needs to evaluate from the evaluation metrics, then begins the metric assessment after obtaining a valid metric.
+4. The model evaluator begins the metric assessment procedure.
+5. The model evaluator retrieves a sub-criterion under the metric being assessed from the evaluation metrics database.
+6. The model evaluator begins the sub-criterion assessment after obtaining a valid, unassessed sub-criterion.
+
+7. The model evaluator passes the test parameters set by the user to the trust model
+8. The trust model will carry out the specified tests in order to generate some statistics on its performance which are logged.
+9. The trust model sends the performance data to the model evaluator.
+10. The model evaluator carries out the assessment of the trust evaluation model with respect to the sub-criterion using the performance data received.
+11. The model evaluator continues with the assessment of the current metric by retrieving the next sub-criterion as per step 5, looping until no more valid sub-criteria are left.
+12. After the model evaluator has assessed all of the sub-criteria under the metric being assessed, it will then complete assessment of the current metric by evaluating the performance of the trust evaluation model using all the sub-criteria assessed.
+13. The model evaluator continues assessment of the trust model by retrieving the next metric as per step 3, looping until all the metrics have been assessed by the same process.
+14. The model evaluator assesses the performance of the model using all the data on the assessed metrics.
+15. The overall assessment obtained is then displayed to the user for further action.
+
+The procedure of parallel evaluators is similar to the above procedure. The only difference is that a set of model evaluators evaluates the metrics simultaneously to save the evaluation time.
+
+
+
+```
+
+sequenceDiagram
+ participant User
+ participant Model evaluator
+ participant Evaluation metrics
+ participant Trust model
+
+ Note over User: 0. Determine test parameters, test environment, and level of detail in assessment
+ User->>Model evaluator: 1. Send assessment parameters (Test parameters, test environment, test detail)
+ Note over Model evaluator: 2. Begin trust model assessment
+ Model evaluator->>Evaluation metrics: 3. Retrieve metric for testing
+ Evaluation metrics-->>Model evaluator: Metric
+ Note over Model evaluator: 4. Begin metric assessment
+ Model evaluator->>Evaluation metrics: 5. Retrieve sub-criterion for testing
+ Evaluation metrics-->>Model evaluator: Sub-criterion
+ Note over Model evaluator: 6. Begin sub-criterion assessment
+ Model evaluator->>Trust model: 7. Pass evaluation parameters (Test parameters, test environment, sub-criterion)
+ Note over Trust model: 8. Run tests and log performance metrics
+ Trust model->>Model evaluator: 9. Send performance data
+ Note over Model evaluator: 10. Evaluate performance of trust model with respect to sub-criterion (Sub-criterion, performance data)
+ Note over Model evaluator: 11. Evaluate performance of trust model with respect to metric (Metric, sub-criterion assessment)
+ Note over Model evaluator: 12. Evaluate performance of trust model based on overall evaluation metrics (Metric assessments)
+ Model evaluator->>User: 13. Presents overall assessment of trust model
+
+```
+
+Y.3260(24)
+
+Sequence diagram showing the parallel evaluation process between User, Model evaluator, Evaluation metrics, and Trust model.
+
+**Figure 9 – Parallel evaluation process**
+
+## 10.2 Procedures for assessing trust evaluation models using the semantic approach
+
+Figure 10 shows the semantic-level evaluation process.
+
+
+
+```
+
+sequenceDiagram
+ participant User
+ participant Testbed
+ participant Trust model
+ participant Metrics storage module
+ participant Fusion module
+ participant Extraction module
+ participant Parsing module
+
+ User->>User: 1. Determine the application scenario and assessed entities (human, things)
+ User->>Extraction module: 2. Send assessment requirement (Application scenario, assessed entities, ...)
+ Extraction module->>Extraction module: 3. Extract the characteristics of agents and environment
+ Extraction module->>Fusion module: 4. Send the extracted characteristics
+ Fusion module->>Fusion module: 5. Fuse all characteristics
+ Fusion module->>Metrics storage module: 6. Specify metrics
+ Metrics storage module->>Metrics storage module: 7. Check if the metrics exists. If not, add the metrics accordingly
+ Metrics storage module->>Fusion module: 8. Send the metric-specified requirement of the testbed (Attack model, sub-metrics, etc.)
+ Fusion module->>Fusion module: 9. Generate agents and environment
+ Fusion module->>Testbed: 10. Send the testbed set-up (Agents, environment, ...)
+ Testbed->>Trust model: 11. Call the trust model
+ Trust model->>Testbed: 12. Model response
+ Testbed->>Testbed: 13. Evaluate the metric of the trust model
+ Testbed->>Parsing module: 14. Send the evaluation result of the metric
+ Parsing module->>Parsing module: 16. Store and parse the evaluation result
+ Parsing module->>Fusion module: 17. Send feedback of the evaluation report
+ Fusion module->>Metrics storage module: 18. Improve the model based on the assessment report
+ Metrics storage module->>Fusion module: 15. Retrieve next metric
+ Fusion module->>Extraction module: 19. Evaluate model repeatedly until the goal satisfied
+
+```
+
+Y.3260(24)
+
+Sequence diagram illustrating the Semantic-level evaluation process across seven modules: User, Testbed, Trust model, Metrics storage module, Fusion module, Extraction module, and Parsing module. The process involves 19 steps, including determining application scenarios, extracting characteristics, fusing metrics, setting up the testbed, evaluating the trust model, and providing feedback for model improvement.
+
+**Figure 10 – Semantic-level evaluation process**
+
+The semantic-level assessment approach has relatively different procedures, and the elements are also different from the general evaluation framework. The procedures are outlined as follows:
+
+1. The user should first determine the application scenario and the assessed entities where the trust model applies. This step decides the environment settings in the following steps, so the user should take care when determining the application scenario and the assessed entities where the trust model applies. In advanced cases, the AS module can offer choices of the application scenarios.
+2. The assessment requirement, including application scenario, assessed entities, etc. is sent to the extraction module.
+3. The extraction module extracts the characteristics of the agents and environment using artificial intelligence (AI) tools.
+4. The extracted characteristics are then be sent to the fusion module.
+5. The fusion module combines the characteristics of both the application scenario and the assessed entities to obtain overall settings.
+
+6. Besides the user settings, the metrics should also be specified according to the requirement, so the fusion module sends a request to the metrics storage module to specify the metrics.
+7. The metrics are specified based on the extracted characteristics, but the metrics related may not exist in metrics storage module. Therefore, the metrics storage module checks if the metrics exist. If not, the metrics can be added according to some rules. A metrics generation module can also be introduced to learn the metrics based on the application patterns in more advanced designs.
+8. Then the metrics storage module sends the metric-specified requirement of the testbed, including the sub-metrics, attack models, etc. to the fusion module.
+9. The fusion module aggregates all the information to testbed settings, and generates agents and the environment accordingly.
+10. The testbed settings consisting of the generated agents and the environment are sent to the testbed.
+11. The testbed calls the trust model.
+12. The trust model responds to the testbed and executes the simulation.
+13. The testbed evaluates the performance of the trust model through the simulation tests.
+14. Each cycle of the evaluation involves one metric, and the evaluation result of the metric is sent to the parsing module per cycle to be stored.
+15. Once an evaluation of a metric finishes, the testbed requests the metrics storage module to retrieve the next metric.
+16. After the assessment results of all metrics are received and stored by the parsing module, it parses the evaluation results to an overall evaluation report, containing the strengths and the weaknesses of the trust models.
+17. The feedback of the evaluation report is sent to trust model.
+18. The trust model improves itself automatically based on the assessment report. In other designs, the report can also be sent to the user to decide whether to improve the model exactly according to the report.
+19. Once the evaluation process is completed, and the evaluation will be performed repeatedly until the model performance satisfies the user's requirement.
+
+# Appendix I
+
+## Overview of existing trust evaluation models
+
+(This appendix does not form an integral part of this Recommendation.)
+
+Existing trust evaluation models can be summarized into four categories: classical methods, graph methods, probability methods, and machine learning methods. All the methods design trust models to satisfy both the general requirements of trust evaluation as well as the specific requirements of scenarios, however, each of them may use different schemes to process data and generate a trust index.
+
+### I.1 Classical methods
+
+Classical trust modelling generally involves common mathematical constructions with heuristics to represent trust-related processes in a digital environment. Equation constructions for trust modelling are flexible in this case.
+
+- **Weight average:** Weight average is a method that combines values of a set and normalizes this sum by the number of elements to achieve a representation of the set that considers all its elements. It is a simple method that is commonly used in trust modelling. A set of trust information is input, and the output trust index is the comprehensive accumulation of trust elements. The weight assigning for each element in this set is flexible and heuristic depending on the use cases of the trust model. The adjustment of such heuristic methods is easy as well.
+- **Game theory:** In trust modelling, game theory, has been used to model the interactions between rational agents and the payoffs received from cooperating or defecting. Game theory provides the payoff structure which can be built upon to determine long term payoffs and then, the incentive to cooperate/defect and finally, a trust metric based of these factors. Additional heuristics specific to trust modelling can be introduced. For example, weight has been reduced when combining different interactions for agents that have less time remaining in an e-commerce market.
+- **Fuzzy logic:** Fuzzy logic is a form of many-valued logic where the trust indexes can be any real number between 0 and 1. The process usually involves fuzzifying all input values into membership functions; Execute all applicable rules in the rule base to compute the fuzzy output; De-fuzzify to get continuous values for the output. Fuzzifying involves assigning a real valued number to an input to indicate the degree to which it belongs to some set. The rule base contains 'If-Then' rules and operators which can be Boolean or analogous fuzzy operators. De-fuzzifying can be done using a variety of algorithms.
+- **Relational measures:** Relational measures, including similarity measures, and correlation measures, are simple constructions meant to represent how far two variables are related, whether positively or negatively. This relation can give insight into whether these two users are likely to trust each other.
+
+### I.2 Graph methods
+
+Graph methods are useful to describe the structure of a network, since most digital networks could be simplified into graphs with nodes and edges. Such methods are typically useful for both inferring trust indexes about other nodes based on the trust indexes of surrounding nodes or along paths, and for transferring information that can be modelled into features for trust.
+
+- **Adjacency matrix:** Adjacency matrix is used to present a finite graph. An adjacency matrix is a square matrix with entries that represent the relationship between entities in the graph. Each $(i,j)$ entry demonstrates the relationship between node $i$ and node $j$ . This
+
+method is efficient for illustrating the trust relationship between different entities in trust modelling. It is also useful when seeking a chain of trust between multiple entities, since it gives a visualization of the trust relationship with others for each entity in a closure network.
+
+- **Hypergraph:** Hypergraphs are generalizations of graphs where an edge can join any number of vertices. Paths in hypergraphs have similar definitions to paths in graphs. Hypergraphs are useful for measuring and finding paths to groups of nodes rather than individual nodes, and therefore they are typically helpful when multiple parties are involved in trust modelling. For situations where there exists one trustor and multiple trustees, trust confidence tuples are attached to hyperedges, combining the trustor and trustees as a single tuple to describe the trust relationship.
+
+### I.3 Probability methods
+
+Interactions in digital environments can be modelled as probabilistic models which involve both observable and unobservable factors to evaluate the uncertainty of future outcomes, and the trust of another entity before interacting can be measured by the believed probability of positive interactions in the trusted environment. Probability methods allow the combination of data and prior knowledge to produce evidence-based probabilities for trust modelling and decision-making.
+
+- **Bayesian theory:** Bayesian theory uses Bayes rule to integrate evidence and prior information and output a posterior probability for some random variable. Conjugate priors (e.g., binomial and beta) are frequently used to provide closed form solutions. Characteristically, model parameters can be further modelled as random variables. In trust modelling, a trust relationship between two entities could be modelled using such a probabilistic model. Trust information is served as evidence, combining together with prior information to evaluate the trustworthiness of the trustee in terms of uncertainty.
+- **Dempster-Shafer theory:** Dempster-Shafer (DS) theory is an evidence theory to represent the uncertainty of an event. It is a generalization of Bayesian probability, and it resolves the single evidence problem and ignorance by combining all possible evidences from different sources. These evidences are measurable with degrees of belief and plausibility. DS theory is often used with other methods in trust modelling. Evidences from the trustor's knowledge, experience and reputation provide different belief assessments for the interactions with trustee. They are combined together using combination rules to generate the uncertainty to evaluate the trustworthiness of the trustee.
+- **Chernoff bound:** Chernoff bound is a theorem that provides exponentially decreasing bounds on tail distributions of sums of independent random variables. It is used to measure accuracy in trust modelling. It has a sharper bound than some other common inequalities.
+
+### I.4 Machine learning methods
+
+Machine learning methods are often applied to trust evaluation, since machine learning models could learn different trust factors and assign weights to them based on data in trust modelling.
+
+- **Classification:** Classification in machine learning is a type of supervised learning that distinguishes given data points to different classes with classification algorithms. A trained classifier takes a data set as input and gives predictions of possible classes as output. There are various classification algorithms, and the implementation depends on the occasions. In trust modelling, classification is used to identify the trustworthiness of a trustee given data of the trustee as input. The trustworthiness in classification is a set of two or more classes depending on the deployed algorithm.
+- **Clustering:** Clustering is a type of unsupervised learning that identifies and groups similar data points based on specific criteria. The main idea is to simplify large datasets to clusters. A similarity measure is implemented on data points before grouping. In trust modelling,
+
+different nodes and entities are organized into clusters by their trust characteristics, and the trustor could determine whether the trustee is trustworthy or not by referring to its cluster ID.
+
+- **Reinforcement learning:** Reinforcement learning teaches an agent how to choose an action from its action space, within an environment to maximize rewards over time. Characteristically, reinforcement learning 1) is a closed loop problem (actions influence later inputs) 2) the agent tries actions to discover the rewards and 3) may have actions affect immediate and all subsequent rewards. For learning interactions and deciding whether to interact, if the expected payoff is good, the agent decides to trust and interact with the trustee. For learning path strengths and choosing best paths, the agent chooses to trust a node that offers the best expected payoff.
+
+# Appendix II
+
+## Trust model assessment metrics
+
+(This appendix does not form an integral part of this Recommendation.)
+
+This appendix presents some of the characteristics of trust model assessment metrics.
+
+### II.1 Comprehensiveness
+
+A good trust model should be comprehensive. A comprehensive trust model is required to accurately capture and represent characteristics of trust, to consider all the related aspects of its application scenario, and should be able to adaptively adjust itself to account for these aspects. The metrics that should be considered under the comprehensiveness category are recommended and discussed in clauses II.1.1 to II.1.6:
+
+#### II.1.1 Dynamicity
+
+Dynamicity is one of the fundamental characteristics of trust. Dynamicity reflects the fact that the trustworthiness of a trustee changes over time.
+
+- A trust model is required to take the dynamicity of trust into account, by considering the freshness of the direct evidence, indirect recommendations, and the current trust indexes.
+- Time-sensitivity of trust needs to be reflected. It is suggested that the older the evidences are, the less reliable they will be, since older evidences are often less reflective of the entity's future behaviours.
+- Trust decay rate should embody self-adaptability. Since the importance of interactions and involved nodes are varied, the trust decay rate needs to be adjusted according to the degree of significance. Moreover, the decay rate should increase as time passes.
+- Historical evidence of interactions should not be written off completely, otherwise the latest interaction failure will erase the trust index established previously.
+
+#### II.1.2 Asymmetry
+
+Asymmetry means that trust is inherently not necessarily mutual or reciprocal. That is to say, if entity A trusts B, there is no guarantee that B will trust A. A trust relationship is directional, and the direction is from the trustor to the trustee. This important feature should be embedded into the trust management process to correctly evaluate realistic trust relationships in digital environments.
+
+#### II.1.3 Transitivity
+
+Transitivity embodies the transferrable nature of trust. When a trusted entity offers recommendations, the trustor's preceding trust in the recommender implies a trust in the recommendation. Transitivity is indispensable for propagating and aggregating trust over a trust chain. Transitivity should be qualified, which means that trust in transition needs to be diluted with increasing length of the trust chain. Moreover, the extent of transitivity should depend on the digital environment, usage scenarios and evolved entities.
+
+#### II.1.4 Context awareness
+
+Context awareness means that trust models need to evaluate trust based on specific context. Trust is context-dependent, indicating that the trust index of an entity may vary significantly in different scenarios. Given the heterogeneity of networks as well as increasingly expanding network coverage, the extraction of contextual features becomes a key step for trust management. Trust models are required to extract contextual features in diverse situations correspondingly, and extracted features will later be used for trust evaluation to achieve context awareness.
+
+#### **II.1.5 Imbalance**
+
+Imbalance represents the unequal updating rate of trust in terms of loss and gain. Trust, in heterogenous digital environments, is considered to be easy to lose but hard to gain. A substantial amount of caution is needed for trust index calculation. Whenever an entity performs poorly, the trust model should significantly reduce its trust index. A previously established trust relationship should be forfeited if the current trust index is below a threshold. The deducted trust index should be regained only if the entity behaves benevolently for a relatively long period of time.
+
+#### **II.1.6 Subjectivity**
+
+Subjectivity refers to the fact that trust is judged differently from person to person, and is often influenced by or based on personal feelings. Trust management in networks should consider nodes' preferences and features extensively. A widely applicable trust model should be able to adjust itself to address users' different needs, making it comprehensive for all types of users. Ignorance of trust subjectivity will decrease the model's flexibility. Meanwhile, trust indexes measured by a trust model that does not consider subjectivity might misrepresent the true trust index of each entity.
+
+### **II.2 Usability**
+
+Usability measures whether a trust model is useable and can be implemented easily in real-world scenarios. To achieve usability, the trust model needs to consider a number of factors, such as computational efficiency, data usability, node diversity and different networks.
+
+#### **II.2.1 Computational efficiency**
+
+Computational efficiency is mainly measured in model complexity, including the time and space complexity of applied algorithms. Trust models should carefully design their algorithms to achieve high computational efficiency, since resource-constrained devices in the networks may not have the capability to apply trust models with computationally demanding algorithms.
+
+#### **II.2.2 Data usability**
+
+Data usability means a trust model's accessibility to necessary inputs. Alternatively, it requires that variables should be able to be obtained from the environment either directly or via additional non-intensive calculations. To ensure usability, a trust model needs to consider whether the data it requires is available in different scenarios, and whether the acquired data is computable. In certain scenarios, the data may not be accessible due to unavailability or privacy concerns.
+
+#### **II.2.3 Node diversity**
+
+Node diversity requires trust management to provide usable trust indexes for all types of nodes, regardless of their system age. Nodes of different types may have disparate features for trust measurement. A widely applicable trust model needs to implement various trust evaluation methods that can cater to the needs of all the possible different users in the network.
+
+#### **II.2.4 Network diversity**
+
+Trust models need to be usable in different types of networks in a heterogenous digital environment. A number of current trust models have applied graph theory as well as graph-related path-finding algorithms to extract trust behaviour and trust relationships. However, this solution is not generally feasible in different types of networks, as some networks are very sparse, while others are extremely dense, or have other problematic graph characteristics. Furthermore, heterogenous networks are characterized by various features and requirements, but most existing trust models do not have such flexibility to be highly compatible. Hence, trust models should consider alternative approaches to address the aforementioned problems so as to ensure the usability in different networks.
+
+### **II.3 Functionality**
+
+A functional trust model should be able to provide corresponding access rights based on different trust indexes and levels. The functionality of a trust model will be reflected in that the model offers an efficient decision-making framework. Service-orientated access control and continuity of access rights are two issues that need to be particularly considered.
+
+#### **II.3.1 Trust-based access control**
+
+A functional trust model should be able to provide corresponding access rights based on different trust indexes and levels. It is suggested that the user with a higher trust index should be given easier and faster access than the user with a lower trust index. For example, a low trust index user is required to do a two-factor authentication in order to gain access to service, while the high trust index user only needs a single-factor authentication.
+
+#### **II.3.2 Service-orientated access control**
+
+Corresponding access control needs to be service-oriented. This means that the number of thresholds, how narrow the bands are and the strictness for different access levels need to be tailored according to the corresponding service. It should additionally be aware of the provision-context, the user and the device to which the service is provided.
+
+#### **II.3.3 Dynamic access rights management**
+
+The continuity of access rights of a user is determined by the user's trustworthiness. Each malicious behaviour will reduce the user's trust degree. If the trust degree is less than a certain threshold, the user should be identified as untrustworthy by access control, and the user's access rights need to be revoked accordingly. To decide whether a user is trustworthy greatly depends on the specific application. Thus, even for trustworthy agents, their trust indexes still need to be tracked and frequently updated.
+
+### **II.4 Security**
+
+A trust model is useful only when it is secure. Thus, a trust model should protect user privacy, defend against attacks, and provide trustworthy methods for authentication and identification. The metrics related to security are listed and discussed in clauses II.4.1 to II.4.6.
+
+#### **II.4.1 Privacy**
+
+Privacy refers to the protection of a user's private data and personal information from malicious attackers. A reliable trust model is required to prevent the invasion of privacy while minimising the use and exposure of personal information during trust management. User information should never be retrieved without validation or the user's permission. Moreover, the user should be allowed to control the use of their own identifying information. Lack of privacy will likely cause distress as well as significantly undermine the degree of trust given by the user to the trust model.
+
+#### **II.4.2 Confidentiality**
+
+Confidentiality requires a trust model to safeguard collected personal data on different aspects, such as avoiding data leakage and preventing unauthorized access. Data of different states, including data in storage, data in use, as well as data in transmission, should never be disclosed by any trust model to an external party without the user's permission. To protect confidentiality, a trust model needs to encrypt the data by converting them from plaintext to cyphertext, so that untitled entities will not be able to sniff the real content. Moreover, access to confidential data should be strictly restricted and deliberately evaluated by the model.
+
+#### **II.4.3 Availability**
+
+Availability means that a trust model should be available whenever needed. The services provided by a trustworthy model should be accessible to users under different network conditions, even if the network is being invaded or attacked by malevolent parties. As cyberattacks are varied and may compromise availability severely, the trust model should monitor and filter out malicious behaviours that aim to jam the network and reduce availability, such as spams and virus attacks. Compromised availability will make the trust model inaccessible to users. Such inaccessibility may pose numerous trust-related security threats, as the trust model is unable to provide underlying trust services.
+
+#### **II.4.4 Integrity**
+
+Integrity mainly stands for assuring the completeness, and authenticity as well as accuracy of data and code. For data integrity, trust models should prevent their data from being tampered with. For code integrity, trust models need to protect their code from being modified or even replaced without authorization. Moreover, it also requires the trust model's behaviour to be consistent and adhere to a set of predefined rules. Loss of integrity will greatly weaken a network's resilience to various cyberattacks. In this case, the privacy and confidentiality of user information, as well as the trust model's availability will also be threatened.
+
+#### **II.4.5 Non-repudiation**
+
+Non-repudiation refers to holding all users accountable for their actions. Malicious interactions should be traceable and back-tracked to the relevant perpetrators. To fulfil the need for traceability, a trust index will be calculated and assigned to each entity. The trust index will reflect the degree of benevolence analysed from previous behaviours. Intuitively, a low trust index suggests that the current entity might have had several malicious interactions before, as each harmful behaviour will deduct from its trust index. Thus, entities with low trust indexes are believed to be untrustworthy, and should not be allowed to interact in the environment.
+
+#### **II.4.6 Authenticity**
+
+Authenticity means that users' identities are verifiable. This metric is intricately linked to non-repudiation and its implementation, given that a trust index is used as indicator of an entity's trustworthiness. A problem of using trust indexes is that a user, or an entity, may possess multiple identities with different trust indexes. This will make it difficult to identify the true perpetrator who could be responsible for malicious behaviours. Thus, an entity should be verified to ensure the authenticity and effectiveness of both trust indexes as well as the management system.
+
+### **II.5 Robustness**
+
+The robustness of a trust model is mainly reflected in the trust model's ability to perform normally while withstanding network disturbance and system errors, and to address cold start problems.
+
+#### **II.5.1 Network disturbance**
+
+In the data transmission process, a trust model may find itself vulnerable to network disturbances like hardware malfunctions, unstable connections, or signal interferences, etc. In a heterogenous environment, disturbances are hard to avoid, and will even occur frequently. To preserve robustness, trust models are required to be insensitive to network disturbances. In other words, the trust model should remain stable and its behaviour should not vary drastically under all types of network disturbance.
+
+#### **II.5.2 Propagation errors**
+
+Propagation errors occur in the transmission of information between two nodes. A robust trust model should account for potential errors of trust indexes during transmission and adjust the
+
+incorrect trust indexes accordingly. Moreover, the model should ensure the reliability of communication links, and thus perpetuate the overall trustworthiness of the digital environment.
+
+#### II.5.3 Cold start problem
+
+A cold start problem arises when a new node is being added into the network. Since the newly added node lacks the necessary information for trust evaluation, such as experience, reputation and feedback, it becomes a demanding task for a trust model to calculate and assign a trust index to it. In such a case, a robust trust model is required to produce a reasonable and usable trust index even without certain essential information.
+
+### II.6 Neutrality
+
+A trust model is neutral if it displays no discriminatory behaviour, contains no bias in either model's data or algorithm, and is transparent to be audited and evaluated. Metrics related to neutrality include non-discrimination, non-bias and transparency, which are discussed in clauses II.6.1 to II.6.3.
+
+#### II.6.1 Non-discrimination
+
+Non-discrimination means that trust models should not discriminate against users based on certain sensitive attributes. A non-discriminatory model should not hold unethical discrimination towards users of certain features, in terms of racial origin, age, disability, religion and gender. Discrimination will cause the users to withhold their information from the service provider, which may impede the trust evaluation process.
+
+#### II.6.2 Non-bias
+
+Non-bias represents the elimination of biases that may exist in a trust model's data and algorithm.
+
+- **Data biases** can be caused by various factors in different stages, ranging from data sampling to data aggregation. Data biases include but are not limited to: sampling bias, omitted variable bias, and reporting bias. (i) **Sampling bias** originates from inappropriate sampling approaches in the stage of data collection. For instance, some sub-groups of small size might get under-sampled or even completely ignored. Sampling bias will possibly cause a model to perform discriminately against certain groups based on their sampling distribution; (ii) **Omitted-variable bias** is caused by unintentionally leaving out one or more relevant explanatory variables. The omission of relevant variables will possibly cause the coefficient of one or more explanatory variables in the model to be biased; (iii) **Reporting bias** is a form of selection bias. It occurs when original data is manipulated intentionally such that only partial and unrepresentative data are selected based on certain concerns.
+- **Algorithmic bias** is mainly caused by flawed design of algorithms. Possible aspects include selection of regularization methods, choice of optimization functions, and in which way that the algorithms are applied. Given that algorithms will perpetuate data biases, while biased algorithms will even amplify existing biases, it is indispensable for unbiased trust models to have comprehensive debiasing approaches accordingly.
+
+#### II.6.3 Transparency
+
+Transparency represents the extent to which the trust model's structure, parameters, as well as algorithms can be inspected and audited by interested parties. A transparent trust model should enable its model information to be accessible, in order to effectively reduce the occurrence of errors, and concurrently facilitate incremental improvements on the model's design. The model should also make its evaluation and decision-making process auditable to prevent certain parties from unfairly manipulating the model. Meanwhile, transparency is also closely related to a model's
+
+explicability. In other words, if a model achieves high explicability, it should be transparent enough to be explicable.
+
+### **II.7 Explicability**
+
+A trust model is explicable if it is able to provide explanations for why certain trust is given to a certain user and how that decision has been made. It should offer an insight into which features, and how different features will affect the evaluation results. Four factors need to be considered for achieving explicability: perceivability, simplicity/decomposability, feature relevance and causality.
+
+#### **II.7.1 Perceivability**
+
+Perceivability requires a trust model to provide human-comprehensible explanations, such as visual or textual artefacts, or example-based interpretations.
+
+- As for visual artefacts, a number of machine learning models use decision trees, charts or graphs to demonstrate the trust evaluation process.
+- Textual artefacts should generate natural language descriptions of certain behaviours of a model, and human-readable explanations for why a decision has been made. The generated descriptions should be both intelligible and persuasive.
+- Example-based explanation methods explain a trust model's behaviour by selecting a few representative instances from the dataset. The methods are feasible only if selected instances can be represented in a human-understandable way.
+
+#### **II.7.2 Simplicity/decomposability**
+
+Simplicity and decomposability both measure the design complexity of trust models. Model simplicity can be affected by several factors, including but not limited to model size, model structure, number of adjustable parameters, as well as algorithm complexity. Decomposability stands for the extent to which the model can be decomposed into individual components, including input, parameters and output with their intuitive explicability. A highly explicable trust model should adopt simpler design for better decomposability.
+
+#### **II.7.3 Feature relevance**
+
+Feature relevance is a model-agnostic method for model explanation, by quantifying the influence that each input feature has on the final output. It is measured by observing the model's response to input changes. A small change of a highly relevant input feature may cause the model's output to change significantly. Since feature relevance, as a model-agnostic method, is applicable to a wide range of models, it should be adopted by all trust models for comparing their explanations with that of other models.
+
+#### **II.7.4 Causality**
+
+Causality represents the level of causal reasoning that a human can achieve with efficiency, effectiveness and satisfaction from the model's self-explanation. Aside from providing post-hoc explanations, a highly explicable trust model should also generate explanations that can describe necessary cause-and-effect relationships. The description of causal relationships should indicate which features or nodes contribute most to the result and how they will affect trust evaluation.
+
+# Appendix III
+
+## Overview of metrics aggregation methods
+
+(This appendix does not form an integral part of this Recommendation.)
+
+The aforementioned samples all adopt a weighted average method to aggregate the metrics' score for simplicity. There are many other aggregation methods that can be applied into the model evaluation, and they will be introduced in the following:
+
+**Simple weighting:** The simplest aggregation method is the most commonly used and simple one that uses the weighted linear equations, which have the form: $T = w_1 * T_1 + w_2 * T_2 + \dots + w_N * T_N$ . The above samples also use the simple weighting method. This method requires that the metric values have interval scales to combine them. For instance, discrete values like "bad", "mediocre", and "good" should be rescaled into interval scales like 1 to 3. There are a lot of works that use weighted linear equation to aggregate the assessment rate in model evaluation. However, sometimes it may not be meaningful to convert the score to interval scales, and studies also show that subjective weights lack consensus among developers, which makes it difficult to convince people of the assessment result.
+
+**Geometric mean:** The simple linear weighting methods adopt the arithmetic mean, which is applicable in some cases. However when the model is required to have high quality for all the metrics, the geometric mean is more useful in this situation. The choice between arithmetic mean and geometric mean can be decided with the model requirement.
+
+**Probabilistic:** The probabilistic methods add probabilistic "goodness" function into the weighted aggregation methods. This method integrates the ambiguity element caused by the lack of consensus of subjective weights. Some works adopt the methods to compensate for the shortcomings of the simple weighting methods. However, the probabilistic "goodness" function needs a benchmark to unify aggregation standards, but the benchmark is always undisclosed. The unobtainability of the benchmark leads to trouble when using this aggregation method, but its improvement on the simple weighting method cannot be ignored.
+
+**Fuzzy logic:** Sometimes, the assessment of a model cannot be simply divided into discrete categories. Fuzzy logic is an extension of Boolean operation to deal with partially real concepts and it is widely used in quality assessment aggregation. This method uses a fuzzy membership function to represent the ratings and weights and the fuzzy operations are used in multiplications and additions operations. The most significant improvement of fuzzy logic is that the method takes the uncertainty in quality evaluation into consideration. Fuzzy logic is relatively easy to be understood, and can output a definite result even if the input is indefinite. However, the metrics need to be fuzzified with specified criteria formulated by experts, and there remain not commonly accepted criteria.
+
+**Outranking:** Simple linear weighted equations need to rescale the score categories into intervals, and this transformation may cause problems. The outrank relation is proposed in some works to deal with the ordinal scale of metrics' scores. Outrank relationship is a partial order relationship used to compare the advantages and disadvantages of two or more objects. In model quality assessment, this method is used to address the semantic uncertainty, such as excellent, good, fair, poor, etc.
+
+**Machine learning:** The machine learning methods can also be used in metrics values aggregation by extracting feature patterns of metrics and overall assessment score. The wide range of machine learning methods give developers choices to select the most suitable methods, and a lot of works adopted it to aggregate the metrics scores. The most important disadvantage of these methods is that they need prior cause-and-effect knowledge about the metrics values and overall assessment values,
+
+which is not available in some cases. Sometimes it can be compensated by expert experience, but there are still limitations to use of the pre-defined machine learning methods.
+
+**Expert experience:** Many studies formulate the aggregation method based on the domain expert experience and knowledge. This method is always performed with pre-defined guidelines and templates of the score table from expert opinions. The expert-based methods usually involve large consumption of manpower and material resources. Additionally, the subjective opinions may lead to problems like deviations and lack of consensus.
+
+# Bibliography
+
+- [b-ITU-T X.800] Recommendation ITU-T X.800 (1991), *Security architecture for Open Systems Interconnection for CCITT applications*.
+- [b-ITU-T Y.3057] Recommendation ITU-T Y.3057 (2021), *A trust index model for information and communication technology infrastructures and services*.
+- [b-ITU-R F.1399] Recommendation ITU-R F.1399 (2001), *Vocabulary of terms for wireless access*.
+- [b-ISO/IEC 10027] ISO/IEC 10027:1990, *Information technology – Information Resource Dictionary System (IRDS) framework*.
+
+
+
+
+
+## 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 |
+| 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 | 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 |
\ No newline at end of file
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@@ -0,0 +1,635 @@
+
+
+I n t e r n a t i o n a l T e l e c o m m u n i c a t i o n U n i o n
+
+# ITU-T
+
+TELECOMMUNICATION
+STANDARDIZATION SECTOR
+OF ITU
+
+# Y.3320
+
+(08/2014)
+
+SERIES Y: GLOBAL INFORMATION
+INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS
+AND NEXT-GENERATION NETWORKS
+
+Future networks
+
+# --- Requirements for applying formal methods to software-defined networking
+
+Recommendation ITU-T Y.3320
+
+## ITU-T Y-SERIES RECOMMENDATIONS **GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS AND NEXT- GENERATION NETWORKS**
+
+| | |
+|--------------------------------------------------------------------|----------------------|
+| GLOBAL INFORMATION INFRASTRUCTURE | |
+| General | Y.100–Y.199 |
+| Services, applications and middleware | Y.200–Y.299 |
+| Network aspects | Y.300–Y.399 |
+| Interfaces and protocols | Y.400–Y.499 |
+| Numbering, addressing and naming | Y.500–Y.599 |
+| Operation, administration and maintenance | Y.600–Y.699 |
+| Security | Y.700–Y.799 |
+| Performances | Y.800–Y.899 |
+| INTERNET PROTOCOL ASPECTS | |
+| General | Y.1000–Y.1099 |
+| Services and applications | Y.1100–Y.1199 |
+| Architecture, access, network capabilities and resource management | Y.1200–Y.1299 |
+| Transport | Y.1300–Y.1399 |
+| Interworking | Y.1400–Y.1499 |
+| Quality of service and network performance | Y.1500–Y.1599 |
+| Signalling | Y.1600–Y.1699 |
+| Operation, administration and maintenance | Y.1700–Y.1799 |
+| Charging | Y.1800–Y.1899 |
+| IPTV over NGN | Y.1900–Y.1999 |
+| NEXT GENERATION NETWORKS | |
+| Frameworks and functional architecture models | Y.2000–Y.2099 |
+| Quality of Service and performance | Y.2100–Y.2199 |
+| Service aspects: Service capabilities and service architecture | Y.2200–Y.2249 |
+| Service aspects: Interoperability of services and networks in NGN | Y.2250–Y.2299 |
+| Enhancements to NGN | Y.2300–Y.2399 |
+| Network management | Y.2400–Y.2499 |
+| Network control architectures and protocols | Y.2500–Y.2599 |
+| Packet-based Networks | Y.2600–Y.2699 |
+| Security | Y.2700–Y.2799 |
+| Generalized mobility | Y.2800–Y.2899 |
+| Carrier grade open environment | Y.2900–Y.2999 |
+| FUTURE NETWORKS | Y.3000–Y.3499 |
+| CLOUD COMPUTING | Y.3500–Y.3999 |
+
+*For further details, please refer to the list of ITU-T Recommendations.*
+
+# Recommendation ITU-T Y.3320
+
+# Requirements for applying formal methods to software-defined networking
+
+## Summary
+
+Recommendation ITU-T Y.3320 provides a descriptive overview and requirements for applying formal methods to software-defined networking (SDN).
+
+Appendix I, introduces an example demonstrating how formal methods are applied to SDN environments.
+
+Formal methods are mathematics-based techniques used for specifying, developing, and verifying software and hardware systems and are expected to increase the reliability and robustness of the system. In SDN environments the consistency, reliability and security of applications are important as incomplete or malicious programmable entities could cause a break-down of underlying networks. In this sense, the use of formal methods can be an effective approach to the mitigation of such problems.
+
+## History
+
+| Edition | Recommendation | Approval | Study Group | Unique ID* |
+|---------|----------------|------------|-------------|---------------------------------------------------------------------------|
+| 1.0 | ITU-T Y.3320 | 2014-08-29 | 13 | 11.1002/1000/12284 |
+
+## Keywords
+
+Formal methods, formal specification, formal verification, future network, software defined networking.
+
+---
+
+\* To access the Recommendation, type the URL in the address field of your web browser, followed by the Recommendation's unique ID. For example, .
+
+## 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 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 .
+
+© ITU 2015
+
+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..... | 2 |
+| 4 Abbreviations and acronyms ..... | 2 |
+| 5 Conventions ..... | 2 |
+| 6 Introduction..... | 2 |
+| 7 Overview of applying formal methods to software-defined networking..... | 3 |
+| 8 Functional requirements ..... | 5 |
+| 8.1 General requirements (GR) ..... | 5 |
+| 8.2 Requirements of formal specification (FS) ..... | 5 |
+| 8.3 Requirements of formal verification (FV)..... | 5 |
+| 8.4 Miscellaneous ..... | 6 |
+| 9 Environmental considerations ..... | 6 |
+| 10 Security considerations..... | 7 |
+| Appendix I – Overview of formal methods for networking ..... | 8 |
+| I.1 High level operational model of SDN and formal methods tool..... | 8 |
+| I.2 Formal specification tool..... | 8 |
+| I.3 Formal verification tool..... | 9 |
+| Bibliography..... | 11 |
+
+
+
+# Recommendation ITU-T Y.3320
+
+## Requirements for applying formal methods to software-defined networking
+
+# 1 Scope
+
+This Recommendation describes requirements for using formal methods. Formal methods are mathematics-based techniques used to specify, develop and verify software and hardware systems in the context of software-defined networking (SDN) for future networks (FN).
+
+The scope of this Recommendation covers:
+
+- an overview of formal methods (formal specification and formal verification) for SDN, and
+- requirements for applying formal methods to SDN.
+
+An example of how to apply formal methods to SDN is provided in Appendix I.
+
+# 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 Y.3001] Recommendation ITU-T Y.3001 (2011), *Future networks: Objectives and design goals*.
+
+[ITU-T Y.3011] Recommendation ITU-T Y.3011 (2012), *Framework of network virtualization for future networks*.
+
+[ITU-T Y.3300] Recommendation ITU-T Y.3300 (2014), *Framework of software-defined networking*.
+
+# 3 Definitions
+
+## 3.1 Terms defined elsewhere
+
+This Recommendation uses the following terms defined elsewhere:
+
+**3.1.1 future network** [ITU-T Y.3001]: A network able to provide services, capabilities and facilities difficult to provide using existing network technologies. A future network is either:
+
+- a) A new component network or an enhanced version of an existing one, or
+- b) A heterogeneous collection of new component networks or of new and existing component networks that is operated as a single network.
+
+**3.1.2 network virtualization** [ITU-T Y.3011]: A technology that enables the creation of logically isolated network partitions over shared physical networks so that heterogeneous collections of multiple virtual networks can simultaneously coexist over the shared networks. This includes the aggregation of multiple resources in a provider and appearing as a single resource.
+
+**3.1.3 software-defined networking** [ITU-T Y.3300]: A set of techniques that enables to directly program, orchestrate, control and manage network resources, which facilitates the design, delivery and operation of network services in a dynamic and scalable manner.
+
+## 3.2 Terms defined in this Recommendation
+
+None.
+
+# 4 Abbreviations and acronyms
+
+This Recommendation uses the following abbreviations and acronyms:
+
+FN Future Network
+
+SDN Software-Defined Networking
+
+# 5 Conventions
+
+In this Recommendation, the following conventions are used:
+
+The keywords "**is required to**" indicate a requirement which must be strictly followed and from which no deviation is permitted, if conformance to this Recommendation is to be claimed.
+
+The keywords "**is recommended**" indicate a requirement which is recommended but which is not absolutely required. Thus this requirement need not be present to claim conformance.
+
+The keywords "**can optionally**" indicate an optional requirement which is permissible, without implying any sense of being recommended. This term is not intended to imply that the vendor's implementation must provide the option and the feature can be optionally enabled by the network operator/service provider. Rather, it means the vendor may optionally provide the feature and still claim conformance with the specification.
+
+# 6 Introduction
+
+Formal methods are software engineering techniques based on the mathematical representation and analysis of software programs and/or hardware. They include formal specification, analysis of specification and formal verification of software and/or hardware behaviour [b-Clarke]. The formal specification describes the semantics of a system using mathematical representation. The formal verification is the act of proving or disproving the correctness of designs or implementations with respect to the formal specification.
+
+Objectives and design goals for future networks are described in [ITU-T Y.3001] which also identifies the high-level capabilities and characteristics that need to be supported by such future networks. To design and implement systems that conform to the design goals identified in [ITU-T Y.3001], the structure and behaviour of the systems need to be described in a way that prevents misinterpretation of the intended meanings and that avoids inconsistency in the systems. FNs may be used for mission critical systems and/or other areas, such as private clouds and data centers, where systems have significant requirements for reliability and consistency and where otherwise a catastrophic disaster could occur.
+
+[ITU-T Y.3300] describes the framework and fundamentals of SDN which it describes as a new networking approach that enables network resources to be directly programmed, orchestrated and controlled.
+
+Finally [ITU-T Y.3011] describes network abstraction into networks that manage the virtualization of the networks.
+
+SDN facilitates network operators to introduce new capabilities by writing simple software programs that control the network in a programmable way. In SDN based networks it is important to check the consistency and security properties of these programs before their installation or deployment in the network.
+
+As described previously, an effective approach to increasing reliability and reducing any misunderstanding or inconsistency of the meaning of the systems or programs is the adoption of formal methods. Formal methods help network operators and application developers protect their systems from unexpected errors that might not be caught during the development and deployment process.
+
+# 7 Overview of applying formal methods to software-defined networking
+
+Figure 1 illustrates the overall flow from the informal description of the conceptual model, logical design and domain specific network through to the implementation of a system using formal methods.
+
+
+
+```
+
+graph TD
+ subgraph Informal_Descriptions [Informal description]
+ A[Conceptual model]
+ B[Logical switch design]
+ C[Domain specific network description]
+ D[Virtual network configuration]
+ end
+
+ subgraph Formal_Specifications [Formal specification]
+ E[Textual representation]
+ F[Graphical representation]
+ end
+
+ subgraph Analysis [Analysis]
+ G[Validation
+Verification
+Conformance testing]
+ end
+
+ subgraph Designers [Designers and Experts]
+ H[System and network designers]
+ I[Domain experts]
+ J[Formal methods experts]
+ end
+
+ subgraph Tools [Formal Methods Tools]
+ K[Theorem proving]
+ L[Model checking]
+ M[Static analysis]
+ end
+
+ Implementation[Implementation]
+
+ A --> E
+ A --> F
+ B --> E
+ B --> F
+ C --> E
+ C --> F
+ D --> E
+ D --> F
+ E --> G
+ F --> G
+ H -.-> G
+ I -.-> G
+ J -.-> G
+ K -.-> G
+ L -.-> G
+ M -.-> G
+ G <--> Implementation
+
+```
+
+Figure 1: Overall flow of formal methods. The diagram shows a process starting with four 'Informal description' boxes: 'Conceptual model', 'Logical switch design', 'Domain specific network description', and 'Virtual network configuration'. Arrows from these boxes point to two 'Formal specification' boxes: 'Textual representation' and 'Graphical representation'. From these, arrows point to an 'Analysis' box containing 'Validation', 'Verification', and 'Conformance testing'. This 'Analysis' box is supported by three groups of inputs: 'System and network designers', 'Domain experts', and 'Formal methods experts' on the left; 'Theorem proving', 'Model checking', and 'Static analysis' on the right. A double-headed arrow connects the 'Analysis' box to an 'Implementation' box at the bottom.
+
+**Figure 1 – Overall flow of formal methods**
+
+Traditional methods for realizing network protocols and devices are based on community agreements on informal descriptions of such mechanisms [b-Griffin]. As depicted in Figure 1, these traditional methods can be improved by applying formal methods to the development process of software-defined networking [b-Wang]. Targets of specification can conceptually model components or mechanisms, logical switch/router models, network protocols, topologies of virtual networks and so on. Informal descriptions of those targets can be encoded in formal specification languages that can reflect the features of targets of the existing methods. The formal specification can be in textual or graphical form to represent their semantics. Once the specifications are described formally, system and network designers can check for the existence of inconsistencies and possible errors in the specification with the help of formal methods experts and/or supporting tools. Various types of formal verification methods (e.g., theorem proving, model checking and static analysis) can be applied to the validation and verification process.
+
+The high-level architecture of SDN consists of four layers as defined in [ITU-T Y.3300]:
+
+- Application layer
+- SDN control layer
+- Resource layer
+- Management functions multi-layer
+
+In order to provide formal methods to SDN, additional functions comprised in the formal methods component are needed to process the formal specification and the formal verification, (see Figure 2). The formal specification function provides an application-formal methods interface for
+
+SDN applications to express their semantics in a formal representation. The formal verification function provides a control-formal methods interface for the SDN controller to check whether new semantics can cause errors or operational conflicts within the network.
+
+
+
+Figure 2: Relationship between the formal methods component and the high-level SDN architecture. The diagram shows a 'Management' block on the left, divided into three sections by dashed lines: 'Application-control interface' (top), 'Control-formal methods interface' (middle), and 'Resource-control interface' (bottom). The top section contains two 'Application' boxes. The middle section contains 'Application support', 'Orchestration', and 'Abstraction' boxes. The bottom section contains 'Control support' and 'Data transport and processing' boxes. To the right, the 'Formal methods component' is shown, containing 'Formal specification' and 'Formal verification' boxes. Dashed lines connect the 'Application' boxes to the 'Formal methods component' via the 'Application-formal methods interface'. Dashed lines connect the 'Orchestration' and 'Abstraction' boxes to the 'Formal methods component' via the 'Control-formal methods interface'. The label 'Y.3320(14)\_F02' is at the bottom right.
+
+**Figure 2 – Relationship between the formal methods component and the high-level SDN architecture**
+
+The formal methods component supports different operation modes which correspond to off-line operation mode and on-line operation mode. In the off-line operation mode, the formal methods component receives a request from applications via the application-formal methods interface and performs the necessary functions to process the specification or verification without interaction with the SDN controller. In the on-line operation mode, the formal methods component receives a request from the SDN controller via the control-formal methods interface during the runtime of the network.
+
+Figure 3 illustrates operational procedures of these different modes.
+
+
+
+Figure 3: Off-line and on-line modes of formal verification. (a) Off-line mode: An 'Application' box sends a '1. Request verification' message to the 'Formal verification' box within the 'Formal method component' via the 'Application-formal methods interface'. The 'Formal verification' box performs '2. Process verification' and sends a '3. Reply verification result' message back to the 'Application' box. (b) On-line mode: An 'SDN controller' box sends a '1. Request verification' message to the 'Formal verification' box within the 'Formal method component' via the 'Control-formal methods interface'. The 'Formal verification' box performs '2. Process verification' and sends a '3. Reply verification result' message back to the 'SDN controller' box. The 'SDN controller' box then sends a '4. Install rules if verified successfully' message to the 'SDN resources (switches)' box. The label 'Y.3320(14)\_F03' is at the bottom right.
+
+**Figure 3 – Off-line and on-line modes of formal verification**
+
+# **8 Functional requirements**
+
+This clause identifies a set of functional requirements that must be supported by the formal methods component.
+
+## **8.1 General requirements (GR)**
+
+GR-1: It is recommended that the formal methods component guarantees that the design and implementation of programmable network resources conforms to the standards, both in terms of correctness and in respect of security properties.
+
+NOTE – Programmable network resources can be customized in software or hardware, or in a combination of both, depending on the requirements from service providers, application/service developers and network operators to produce an optimal solution for their uses.
+
+GR-2: It is required that the formal methods component provides open interfaces to interact with the application and/or SDN controller.
+
+NOTE 1 – The application and/or SDN controller sends requests to use formal specification and/or verification functions provided by the formal methods component.
+
+NOTE 2 – After performing the specification or verification process, the formal methods component sends results back to the application and SDN controller.
+
+GR-3: It is recommended that the formal methods component supports policies or rules required by applications in heterogeneous network environments.
+
+NOTE – Control and management entities that span across SDN-based networks which are owned by different stake-holders, management authorities or vendors, need to be controlled in distributed environments according to nature. Multiple entities may need to be coordinated to conform to the higher level requirements of heterogeneous networks.
+
+GR-4: It is recommended that the formal methods component supports authentication and authorization to confirm the identity and access rights of users.
+
+## **8.2 Requirements of formal specification (FS)**
+
+FS-1: It is recommended that the formal methods component supports formal syntax and semantics in high-level languages, APIs and underlying protocols for SDN.
+
+NOTE 1 – High-level languages that interface with control and management entities need to have formal semantics to avoid any confusion in the interpretation of the underlying mechanism and/or network configuration.
+
+NOTE 2 – Specifications of programmable network devices such as switches and protocols for controlling those devices need to be proved safe and consistent to provide a stable foundation for the SDN application and services.
+
+NOTE 3 – Properties that need to be satisfied with SDN should be described in notations with formal semantics.
+
+NOTE 4 – An action or a set of actions associated with target properties must be described in notations with formal semantics. Examples of actions include packet forwarding, packet modifications and group table or pipeline processing.
+
+FS-2: It is recommended that the formal methods component supports a conceptual model to reason properties and behaviors about networks defined, configured and/or implemented by software and/or hardware for SDN.
+
+## **8.3 Requirements of formal verification (FV)**
+
+### **8.3.1 Consistency and security**
+
+FV-1: It is required that the formal methods component checks the consistency and security of network configurations, the virtual/physical topologies and the intended properties of the network resources.
+
+NOTE 1 – Examples of intended properties include the following:
+
+- No routing loops and/or non-reachable points in the network
+- No conflicts between logical and physical networking resource assignment for applications
+- No conflicts in dynamic network update where new or update configurations conform to properties of the network and do not break the consistency of existing networks
+
+FV-2: It is required that the formal methods component checks the consistency of the application and policies against conflicts that can occur between SDN entities or in network configurations.
+
+NOTE – Examples of conflicts include the following:
+
+- Rule or behaviour conflicts between multiple applications in a controller.
+
+### **8.3.2 Operations**
+
+FV-3: It is recommended that the formal methods component supports different verification modes (e.g., off-line mode and on-line mode) and different verification methodologies (e.g., symbolic or non-symbolic manners).
+
+FV-4: For the symbolic verification methodology, it is recommended that the formal methods component supports symbolic model checking technologies in order to verify whether the application meets the specification.
+
+FV-5: The formal verification component can optionally support the following operations.
+
+- Collecting the information of network topology and data forwarding paths (e.g., a flow table in OpenFlow [b-ONF]) from an SDN controller
+- Creating description code in a predefined formal language based on the collected information and generating a symbolic transition graph using the created description code in the formal language
+- Applying a verification operation to the created transition graph
+- Providing verification results in the formula based on the Boolean expression (e.g., binary decision diagram or conjunctive normal form)
+
+### **8.3.3 Resource information discovery**
+
+FV-6: It is required that the formal methods component obtains the information on network resources and SDN entities including static information (e.g., network topology and capability of SDN entities) and dynamic information (e.g., re-configured topology and status of SDN entities).
+
+FV-7: It is recommended that the formal methods component obtains the entire network topology information within an administrative domain from the SDN controller(s).
+
+## **8.4 Miscellaneous**
+
+Mic-1: The formal methods component can optionally provide statistics about the verification process such as a summary of verification results, processing time and other performance data.
+
+# **9 Environmental considerations**
+
+Applying formal methods to SDN reduces any inconsistency or ambiguity of SDN applications by enabling the application to be specified and verified before an execution in the network. It can prevent malfunctions, misuses and unexpected behaviour of SDN applications and so should optimize the resource usage, which reduces energy consumption.
+
+However, the verification process requires additional computational resources to examine SDN applications in the network and energy consumption may increase.
+
+# **10 Security considerations**
+
+SDN facilitates network operator's control of their networks in an automatic and programmable way. In other words, SDN network operators including application developers can introduce a new capability by writing a program. Many important properties such as programmability, reliability, flexibility and customization of network resources, need to be supported by SDN. However, these properties can cause unexpected security problems in SDN environments as incomplete or malicious programs can also be introduced easily into the networks. Consequently, programs need to be thoroughly examined before their installation to the networks. For SDN therefore, the use of formal methods can be an effective approach to checking that programs are operating correctly and avoiding possible inconsistency or misinterpretation of their networking behaviours. Security issues therefore should be considered and resolved during the formal specification and verification stage.
+
+# Appendix I
+
+## Overview of formal methods for networking
+
+(This appendix does not form an integral part of this Recommendation.)
+
+The objective of this appendix is to provide an example showing how a formal specification and verification process can be applied to SDN. In SDN environments consistency and security are important to help ensure that errors or operational conflicts are not introduced into the networks. In this sense, formal methods are effective in the specification and verification of applications or programs in order to avoid inconsistency or misinterpretation of their networking behaviours.
+
+In order to avoid implementation dependency in describing the example used in this appendix, logical functional descriptions are used to describe behaviours and operations related to formal specification and verification.
+
+## I.1 High level operational model of SDN and formal methods tool
+
+Figure I.1 illustrates a high level operational model of SDN including the formal methods tool that provides the specification syntax and semantics for applications and the verification procedures to check their operational behaviours within the networks.
+
+The following assumptions are considered in this example [b-Canini].
+
+- It is an OpenFlow based SDN environment where the OpenFlow protocol (version 1.0 ~ 1.3) is used for communication between the controller and switches.
+- The controller manages the OpenFlow based global network information and it needs to provide this global network information when it receives a request from the formal methods tool.
+- The formal description code considered in this section is based on the fields defined in the OpenFlow protocol.
+
+
+
+Y.3320(14)\_Fl.1
+
+Figure I.1: High level operational model of SDN and formal methods tool. The diagram shows a dashed box at the top containing four 'Application' blocks. Below this is the 'Application-formal methods interface' which connects to the 'Formal methods tool' block. The 'Formal methods tool' block contains 'Formal specification' and 'Formal verification' sub-blocks. A 'Control-formal methods interface' connects the 'Formal methods tool' to the 'SDN controller' block. The 'SDN controller' block is connected to a 'Global network view (OF based flow entry)' database. Below the controller is a network topology of five 'SDN switch' blocks connected in a mesh. Dashed lines represent 'OpenFlow protocol' communication between the controller and the switches. A label 'Y.3320(14)\_Fl.1' is in the bottom right corner.
+
+Figure I.1 – High level operational model
+
+## I.2 Formal specification tool
+
+Applications need to express their policies or rules in a formal specification supported by the formal methods tool. The formal specification is a representation expressed in a language whose semantics are formally defined based on logics and mathematics (i.e., it is not a natural language).
+
+Figure I.2 shows the interaction between the application and the formal methods tool [b-Shin]. The application uses the application programming interface (API) of the formal specification to request the conversion of their rules and receive formal description code as a result.
+
+
+
+```
+
+S1 := ch1?x.S11(x) + ch2?x.S12(x) + {}; S1
+S11(x) := matchSrcIP(x,10)->{}:S13(x)
+ + ~matchSrcIP(x,10)->{}:S1 // no rule to match
+S12(x) := matchSrcIP(x,10)->{}:S13(x)
+ + ~matchSrcIP(x,10)->tau.S14(x)
+S13(x) := ch3!x.S1
+S14(x) := matchSrcIP(x,11)->{}:S13(x)
+ + ~matchSrcIP(x,11)->{}:S1 // no rule to match
+S2 := ch3?x.S21(x) + {}; S2
+S21(x) := matchSrcIP(x,10)->{}:S22(x)
+ + ~matchSrcIP(x,10)->tau.S22(x)
+S22(x) := matchSrcIP(x,11)->{}:S2 // drop
+ + ~matchSrcIP(x,11)->{}:S2 // no rule to match
+S23(x) := ch4!x.S2
+S3 := ch4?x.S31(x) + {}; S3
+S31(x) := matchSrcIP(x,10)->{}:S32(x)
+ + ~matchSrcIP(x,10)->{}:S3 // no rule to match
+S32(x) := ch2!x.S3
+E := ch1!x.E1
+E1 := {}; E1
+SDN := (S1 || S2 || S3 || E) / {ch1,ch2,ch3,ch4}
+
+```
+
+*Formal description code*
+Y.3320(14)\_FI.2
+
+Figure I.2: Formal specification tool with interfaces. The diagram shows an 'Application' box and a 'Formal methods tool' box. The Application sends a request '1. Request conversion to formal specification' to the tool, which contains 'Formal specification' and 'Formal verification' components. The tool returns a '2. Reply formal description code' to the Application. A sample of the 'Formal description code' is shown in a dashed box, containing rules S1, S2, S3, S4, E, and an SDN definition.
+
+**Figure I.2 – Formal specification tool with interfaces**
+
+Figure I.3 illustrates in greater detail how the formal specification is processed. When the formal specification receives the request, it gathers the application policy and the global network information from the controller. Then it converts these inputs into a formal description code using the formal language defined. Finally, it returns the formal description code to the application.
+
+
+
+```
+
+S1 := ch1?x.S11(x) + ch2?x.S12(x) + {}; S1
+...
+S2 := ch3?x.S21(x) + {}; S2
+S21(x) := matchSrcIP(x,10)->{}:S23(x)
+ + ~matchSrcIP(x,10)->tau.S22(x)
+S22(x) := matchSrcIP(x,11)->{}:S2
+ + ~matchSrcIP(x,11)->{}:S2
+S23(x) := ch4!x.S2
+...
+E := ch1!x.E1
+E1 := {}; E1
+SDN := (S1 || S2 || S3 || E) / {ch1,ch2,ch3,ch4}
+
+```
+
+**Annotations:**
+
+- Switch S1 gets packet from ch1 or ch2 and becomes S11 or S12, respectively. Otherwise, idle one time unit
+- Switch S2 gets packet through ch3, otherwise, idle.
+- Check if source IP of packet 'x' is matched with 10
+- Otherwise, try to match other rules
+- Check if source IP of packet 'x' is matched with 11, and if so, drop it
+- No rule to match, so become S2
+- Egress packet 'x' through ch4
+- Send packet 'x' to ch1
+- Idle forever
+- Switch S1, S2, S3, and environment E is running in parallel
+
+Formal description code
+Y.3320(14)\_FI.3
+
+Figure I.3: Specification procedures and formal description code. The diagram shows the 'Formal specification' process: 'Get application policy' -> 'Get global network information from the controller' -> 'Conversion application policy and global network inf. to formal description code'. The resulting 'Formal description code' is shown with annotations explaining each part of the code.
+
+**Figure I.3 – Specification procedures and formal description code**
+
+## I.3 Formal verification tool
+
+When the application gets the formal description code, it can request the verification tool to check whether any errors or operational conflicts may occur within the networks. Figure I.4 shows the verification procedures in more detail. When the formal verification receives the request, it parses the formal description code received, builds a transition graph and starts to traverse the transition graph created previously to check the consistency or correctness with respect to the application rules and the global network operations.
+
+Figure I.5 shows an example of a transition graph whose construction was based on the formal description code. The transition graph is a directed graph where boolean, action and assignments are labelled [b-Shin]. From each state, when boolean holds, action and assignments are performed and
+
+the current state proceeds to the next state. In this transition graph, each field in a flow entry and a packet can be represented symbolically as a binary decision diagram or as a conjunctive normal form. In order to verify the existence of a loop in this example, it can apply a first search starting from the root state "S1||S2||S3" and identify every loop. To find the loops that a packet is looping, actions on the edge should be detected based on the rules defined for the loop detection. The red line in Figure I.5 indicates that looping may occur in the networks. Finally, the formal verification tool sends back the verification results to the application.
+
+
+
+**Figure I.4 – Verification procedures**
+
+```
+
+S1 = ch1?x.S11(x) + ch2?x.S12(x) + {} . S1
+S11(x) = match(x(P),10) -> {} . S13(x)
+ + ~match(x(P),10) -> {} . S1 no rule to match
+S12(x) = match(x(P),10) -> {} . S13(x)
+ + ~match(x(P),10) -> tau . S14(x)
+S13(x) = ch3!x.S1
+S14(x) = match(x(P),11) -> {} . S13(x)
+ + ~match(x(P),11) -> {} . S1 no rule to match
+
+S2 = ch3?x.S21(x) + {} . S2
+S21(x) = match(x(P),10) -> {} . S23(x)
+ + ~match(x(P),10) -> tau . S22(x)
+S22(x) = match(x(P),11) -> S2 ! drop
+ + ~match(x(P),11) -> {} . S2 no rule to match
+S23(x) = ch4!x.S2
+
+S3 = ch4?x.S31(x) + {} . S3
+S31(x) = match(x(P),10) -> {} . S32(x)
+ + ~match(x(P),10) -> {} . S3 no rule to match
+S32(x) = ch2!x.S3
+
+E = ch1!x.E1
+E1 = {} . E1
+
+SDN = (S1 || S2 || S3 || E) \ {ch1,ch2,ch3,ch4}
+
+```
+
+Formal description code
+
+**Formal methods tool**
+
+Formal verification
+
+Parsing the format description code
+
+Build transition graph
+
+Traverse transition graph and check the application rules
+
+Application
+
+1. Request verification
+
+2. Reply verification results
+
+Y.3320(14)\_FI.4
+
+Figure I.4 – Verification procedures
+
+
+
+**Figure I.5 – Transition graph and traverse results**
+
+Y.3320(14)\_FI.5
+
+The left graph shows a state transition diagram starting from root state S1||S2||S3||E. Transitions are labeled with actions like tau@ch1, m(x, 10); {}, ~m(x, 10); {}, tau@ch3, m(x, 11); {}, etc. States include S11||S2||S3||E1, S13||S2||S3||E1, S1||S2||S3||E1, S1||S21||S3||E1, S13||S22||S3||E1, S1||S23||S3||E1, S1||S2||S31||E1, S1||S2||S32||E1, S12||S2||S3||E1, and S14||S2||S3||E1.
+
+The right graph is identical to the left but highlights a specific path in red, indicating a loop. The red path starts from S13||S2||S3||E1, goes to S1||S21||S3||E1 via tau@ch3, then to S1||S23||S3||E1 via m(x, 10); {}, then to S1||S2||S31||E1 via tau@ch4, then to S1||S2||S32||E1 via m(x, 10); {}, then to S12||S2||S3||E1 via tau@ch2, and finally back to S13||S2||S3||E1 via m(x, 10); {}. This loop is labeled with $\hat{ab}$ .
+
+Figure I.5 – Transition graph and traverse results
+
+10 Rec. ITU-T Y.3320 (08/2014)
+
+# Bibliography
+
+- [b-Bishop] Steve Bishop, *et. al.* (2005), *Rigorous specification and conformance testing techniques for network protocols, as applied to TCP, UDP, and Sockets*.
+.
+- [b-Canini] Marco Canini, *et. al.* (2012), *A NICE way to test OpenFlow applications*.
+
+- [b-Clarke] Edmund M. Clarke and Jeannette M. Wing (1996), "*Formal methods: state of the art and future directions*".
+[https://www.site.uottawa.ca/~afelty/csi5110/state\\_art\\_future.pdf](https://www.site.uottawa.ca/~afelty/csi5110/state_art_future.pdf).
+- [b-Griffin] Timothy G. Griffin, *Do Formal Methodists have Bell-Shaped Heads?* Proceedings of the First Workshop on Automated Theory Engineering.
+- [b-ONF] Open Networking Foundation, *OpenFlow/Software-Defined Networking (SDN)*,
+
+- [b-Shin] M. Shin, H. Kwak, *et. al.* (2013), *Process Algebra Based Symbolic Verification Framework for Software-Defined Networking*. Telecommunications Review Vol. 23 No. 5.
+- [b-Wang] Anduo Wang, *et. al.* (2011), *FSR: Formal analysis and implementation toolkit for safe interdomain routing*, ACM SIGCOMM Conference on Data Communication.
+
+
+
+
+
+# SERIES OF ITU-T RECOMMENDATIONS
+
+| | |
+|-----------------|--------------------------------------------------------------------------------------------------|
+| Series A | Organization of the work of ITU-T |
+| 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 | 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 |
\ No newline at end of file
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@@ -0,0 +1,472 @@
+
+
+# ITU-T
+
+TELECOMMUNICATION
+STANDARDIZATION SECTOR
+OF ITU
+
+# Y.4004
+
+(11/2021)
+
+SERIES Y: GLOBAL INFORMATION
+INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS,
+NEXT-GENERATION NETWORKS, INTERNET OF
+THINGS AND SMART CITIES
+
+Internet of things and smart cities and communities –
+General
+
+---
+
+**Overview of smart oceans and seas, and
+requirements for their information and
+communication technology implementation**
+
+Recommendation ITU-T Y.4004
+
+# ITU-T Y-SERIES RECOMMENDATIONS
+
+## GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS, NEXT-GENERATION NETWORKS, INTERNET OF THINGS AND SMART CITIES
+
+## GLOBAL INFORMATION INFRASTRUCTURE
+
+| | |
+|-------------------------------------------|-------------|
+| General | Y.100–Y.199 |
+| Services, applications and middleware | Y.200–Y.299 |
+| Network aspects | Y.300–Y.399 |
+| Interfaces and protocols | Y.400–Y.499 |
+| Numbering, addressing and naming | Y.500–Y.599 |
+| Operation, administration and maintenance | Y.600–Y.699 |
+| Security | Y.700–Y.799 |
+| Performances | Y.800–Y.899 |
+
+## INTERNET PROTOCOL ASPECTS
+
+| | |
+|--------------------------------------------------------------------|---------------|
+| General | Y.1000–Y.1099 |
+| Services and applications | Y.1100–Y.1199 |
+| Architecture, access, network capabilities and resource management | Y.1200–Y.1299 |
+| Transport | Y.1300–Y.1399 |
+| Interworking | Y.1400–Y.1499 |
+| Quality of service and network performance | Y.1500–Y.1599 |
+| Signalling | Y.1600–Y.1699 |
+| Operation, administration and maintenance | Y.1700–Y.1799 |
+| Charging | Y.1800–Y.1899 |
+| IPTV over NGN | Y.1900–Y.1999 |
+
+## NEXT GENERATION NETWORKS
+
+| | |
+|-------------------------------------------------------------------|---------------|
+| Frameworks and functional architecture models | Y.2000–Y.2099 |
+| Quality of Service and performance | Y.2100–Y.2199 |
+| Service aspects: Service capabilities and service architecture | Y.2200–Y.2249 |
+| Service aspects: Interoperability of services and networks in NGN | Y.2250–Y.2299 |
+| Enhancements to NGN | Y.2300–Y.2399 |
+| Network management | Y.2400–Y.2499 |
+| Computing power networks | Y.2500–Y.2599 |
+| Packet-based Networks | Y.2600–Y.2699 |
+| Security | Y.2700–Y.2799 |
+| Generalized mobility | Y.2800–Y.2899 |
+| Carrier grade open environment | Y.2900–Y.2999 |
+
+## FUTURE NETWORKS
+
+| | |
+|-----------------|---------------|
+| CLOUD COMPUTING | Y.3500–Y.3599 |
+|-----------------|---------------|
+
+| | |
+|----------|---------------|
+| BIG DATA | Y.3600–Y.3799 |
+|----------|---------------|
+
+| | |
+|-----------------------------------|---------------|
+| QUANTUM KEY DISTRIBUTION NETWORKS | Y.3800–Y.3999 |
+|-----------------------------------|---------------|
+
+## INTERNET OF THINGS AND SMART CITIES AND COMMUNITIES
+
+| | |
+|---------------------------------------------------------|----------------------|
+| General | Y.4000–Y.4049 |
+| Definitions and terminologies | Y.4050–Y.4099 |
+| Requirements and use cases | Y.4100–Y.4249 |
+| Infrastructure, connectivity and networks | Y.4250–Y.4399 |
+| Frameworks, architectures and protocols | Y.4400–Y.4549 |
+| Services, applications, computation and data processing | Y.4550–Y.4699 |
+| Management, control and performance | Y.4700–Y.4799 |
+| Identification and security | Y.4800–Y.4899 |
+| Evaluation and assessment | Y.4900–Y.4999 |
+
+*For further details, please refer to the list of ITU-T Recommendations.*
+
+## Recommendation ITU-T Y.4004
+
+## Overview of smart oceans and seas, and requirements for their information and communication technology implementation
+
+## Summary
+
+Smart oceans and seas (SO&S) permit the use of telecommunications or information and communication technologies to conserve and sustainably use the oceans, seas and marine resources. Recommendation ITU-T Y.4004 provides an overview of SO&S and specifies high-level requirements for their implementation. SO&S use cases are also provided in an appendix.
+
+## History
+
+| Edition | Recommendation | Approval | Study Group | Unique ID* |
+|---------|----------------|------------|-------------|---------------------------------------------------------------------------|
+| 1.0 | ITU-T Y.4004 | 2021-11-29 | 20 | 11.1002/1000/14812 |
+
+## Keywords
+
+Implementation, overview, smart oceans and seas.
+
+---
+
+\* To access the Recommendation, type the URL in the address field of your web browser, followed by the Recommendation's unique ID. For example, .
+
+## 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 .
+
+© ITU 2022
+
+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 | Conventions ..... | 2 |
+| 6 | Introduction to smart oceans and seas ..... | 2 |
+| | 6.1 Goals of smart oceans and seas ..... | 2 |
+| | 6.2 Conceptual model of smart oceans and seas ..... | 2 |
+| | 6.3 Common characteristics of smart oceans and seas..... | 4 |
+| 7 | General requirements for smart oceans and seas..... | 4 |
+| 8 | Requirements for information and communication technology implementation of smart oceans and seas ..... | 5 |
+| | 8.1 Service support requirements ..... | 5 |
+| | 8.2 Communication requirements ..... | 5 |
+| | 8.3 Platform requirements for smart oceans and seas ..... | 5 |
+| | 8.4 Device requirements..... | 6 |
+| | 8.5 Data management requirements ..... | 6 |
+| | Appendix I – Use cases of SO&S ..... | 7 |
+| | I.1 Shipping..... | 7 |
+| | I.2 Marine fisheries ..... | 7 |
+| | I.3 Resource exploitation ..... | 7 |
+| | I.4 Marine tourism ..... | 7 |
+| | I.5 Disaster warning..... | 8 |
+| | I.6 Maritime safety..... | 8 |
+| | I.7 Environmental protection and tackling climate change ..... | 8 |
+| | Bibliography..... | 9 |
+
+
+
+# Recommendation ITU-T Y.4004
+
+## Overview of smart oceans and seas, and requirements for their information and communication technology implementation
+
+## 1 Scope
+
+This Recommendation provides an overview of smart oceans and seas (SO&S), including their goals, conceptual model and common characteristics, and specifies high-level requirements for their information and communication technology (ICT) implementation. Some SO&S use cases are also provided in an appendix.
+
+## 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.
+
+None.
+
+## 3 Definitions
+
+### 3.1 Terms defined elsewhere
+
+This Recommendation uses the following terms defined elsewhere:
+
+**3.1.1 device** [b-ITU-T Y.4000]: With regard to the Internet of things, this is a piece of equipment with the mandatory capabilities of communication and the optional capabilities of sensing, actuation, data capture, data storage and data processing.
+
+**3.1.2 high altitude platform station (HAPS)** [b-ITU-R F.592-4]: A station located on an object at an altitude of 20 to 50 km and at a specified, nominal, fixed point relative to the Earth.
+
+**3.1.3 personal terminal** [b-ITU-R M.1224-1]: A light-weight, small, portable terminal providing the capability for the user to be either stationary or in motion while accessing and using telecommunication services.
+
+**3.1.4 service** [b-ITU-T Y.2091]: A set of functions and facilities offered to a user by a provider.
+
+### 3.2 Terms defined in this Recommendation
+
+This Recommendation defines the following terms:
+
+**3.2.1 smart oceans and seas (SO&S)**: Use of telecommunications or information and communication technology in the oceans and seas, to enable advanced services in different areas such as marine economy, marine public management and marine environment protection, so as to conserve and sustainably use the oceans, seas and marine resources.
+
+**3.2.2 smart oceans and seas platform (SO&S platform)**: A telecommunications or computer system or integration of these systems, equipped on carriers such as ships, oil and gas platforms, buoys and planes that use information and communication technology to access data sources and process them to offer SO&S services in a marine environment.
+
+## 4 Abbreviations and acronyms
+
+This Recommendation uses the following abbreviations and acronyms:
+
+| | |
+|------|------------------------------------------|
+| HAPS | High Altitude Platform Station |
+| ICT | Information and Communication Technology |
+| SO&S | Smart Oceans and Seas |
+
+## 5 Conventions
+
+In this Recommendation:
+
+The phrase "**is required to**" indicates a requirement that must be strictly followed and from which no deviation is permitted if conformity to this document is to be claimed.
+
+The phrase "**is recommended**" indicates a requirement that is recommended but which is not absolutely required. Thus this requirement need not be present to claim conformity.
+
+The phrases "**can optionally**" and "**may**" indicate an optional requirement that is permissible, without implying any sense of being recommended. These terms are not intended to imply that the vendor's implementation must provide the option and the feature can be optionally enabled by the network operator or service provider. Rather, it means the vendor may optionally provide the feature and still claim conformity to the specification.
+
+## 6 Introduction to smart oceans and seas
+
+### 6.1 Goals of smart oceans and seas
+
+Human livelihoods and economic activities are closely related to the oceans and seas, such as shipping and fisheries. Marine information, such as that relating to meteorology, hydrology and pollution, is important for human activities in and on oceans and seas. However, it is more difficult to collect information about oceans and seas than the land. ICTs, such as marine sensor technology, satellite communications, navigation technology, remote sensing, unmanned technology, big data and artificial intelligence, make it easier for humans to get information about oceans and seas, so as to provide better services, such as more economical and safer shipping, sustainable fisheries and predictions of marine hazard weather.
+
+The goals of SO&S are to use telecommunications or ICTs to enable advanced services in different marine areas such as economy, public management and environmental protection, so as to conserve and sustainably use the resources.
+
+### 6.2 Conceptual model of smart oceans and seas
+
+Figure 1 shows that SO&S has two parts: marine and onshore. The marine part contains SO&S platforms and devices thereon. There are two types of SO&S platform: manned and unmanned. The marine and the onshore parts are connected by a marine communication network.
+
+
+
+The diagram illustrates the conceptual model of smart oceans and seas, divided into the Marine part and the Onshore part.
+
+**Marine part:**
+
+- Manned SO&S platform:** Includes an Onboard device and a Personal terminal connected to a Platform internal network. It is connected to the Marine communication network.
+- Unmanned SO&S platform:** Includes an Onboard device connected to a Platform internal network. It is connected to the Marine communication network.
+- Marine communication network:** A central hub connecting the platforms to the onshore services.
+
+**Onshore part:**
+
+- SO&S platform operation service providers:** Shipping company, Fishery company, Marine scientific research institution.
+- Third party service providers:** Marine rescue, Locating service, Meteorological and hydrological forecast, Port.
+- Regulatory departments:** Fishery administration, Customs, Marine environment authority.
+- Smart city systems:** Logistics, E-commerce, Finance and insurance.
+
+**Legend:**
+
+- Communicate
+- - - - Interface
+
+Y.4004(21)
+
+Figure 1 – Conceptual model of smart oceans and seas. The diagram illustrates the architecture of smart oceans and seas, divided into Marine part and Onshore part. The Marine part includes Manned SO&S platforms and Unmanned SO&S platforms, both connected to a central Marine communication network. The Onshore part includes SO&S platform operation service providers, Third party service providers, Regulatory departments, and Smart city systems. Solid lines represent communication, and dashed lines represent interfaces.
+
+**Figure 1 – Conceptual model of smart oceans and seas**
+
+Manned SO&S platforms operate with humans, such as operators, crews and passengers, on board. Examples of manned SO&S platforms are the computer systems on various kinds of ships, oil platforms and helicopters.
+
+Unmanned SO&S platforms are usually designed to operate autonomously or controlled remotely by humans. Examples of unmanned SO&S platforms are computer systems on unmanned surface vehicles, unmanned underwater vehicles, buoys, drones, fish farms and wind power generators.
+
+The devices on SO&S platforms are connected through platform internal networks that can be those used to connect devices, such as wireless fidelity and industrial field bus, usually connect to the marine network through gateways.
+
+A marine communication network connects various kinds of SO&S platform, devices and humans at sea with service providers and onshore service users. A marine communication network is usually hybrid multi-method in nature, involving communication by methods such as satellite, short-wave radio, shore-based cellular, HAPS and underwater acoustic.
+
+Personal terminals, such as cell phones, laptops and wearable electronics, usually connect to a SO&S platform through a platform internal network.
+
+The onshore part of SO&S consists of service providers and onshore service users. There are three types of service providers and users.
+
+- SO&S platform operation service providers are usually the owners of SO&S platforms, such as shipping companies, fishery companies and marine scientific research institutions. They acquire data from SO&S platforms, devices or human at sea, and send data to onshore data centres for processing, so as to provide services for their SO&S platforms or personnel at sea and other users. They are not only data providers, but also data consumers.
+- Third-party information service providers usually provide marine infrastructure and marine services to other users, such as maritime rescue, meteorological and hydrological forecasts, as well as port and location services.
+- Regulatory authorities, such as fishery administration, customs and marine environment authorities.
+
+SO&S also have interfaces with smart city systems, such as logistics, e-commerce, finance and insurance, to enable more smart services for users.
+
+### **6.3 Common characteristics of smart oceans and seas**
+
+The ICT implementations of SO&S are different from those on land in many aspects, such as the technologies used and deployment sites. Special considerations are required for SO&S ICT implementation.
+
+- Spatial complexity of the oceans and seas. Mobile SO&S platforms and devices may travel across different zones of oceans and sea, which are probably under different regulatory requirements according to regulation and laws, such as the *United Nations convention on the law of the sea* [b-UNCLOS].
+- Limited communication conditions. The main means of marine communication are achieved by satellite, radio, shore-based wireless and underwater acoustic methods, so usually bandwidth and communication range are limited and the costs high.
+- Unstable energy supply of devices. The energy for offshore sensors and other devices is usually supplied by batteries, as well as renewable sources such as solar, wind and ocean energy, that are limited in power and low in stability.
+- Human operation and maintenance are limited. Human activities at sea rely on special carriers, such as ships, submersibles and aircraft, so operation and maintenance of platforms or devices are not easy. As a consequence, various kinds of unmanned ship, as well as underwater and unmanned aerial vehicles have been widely used to replace human intervention.
+- Marine environmental protection requirements. The marine environment is more vulnerable than that on land to hazards from various devices, such as harmful chemical substances in batteries and electromagnetic signals that may impact marine life.
+
+## **7 General requirements for smart oceans and seas**
+
+The following are general requirements for SO&S related to its common characteristics. It is required
+
+- to provide precise and reliable locating capability and location-based services, in order to comply with international regulation and laws;
+- to specify the quality of services according to different application scenarios, e.g., real-time control and emergency communication;
+- to consider the energy efficiency of ICT equipment and means to reduce the hazards caused by power loss;
+
+- to reduce manpower and to improve reliability by use of remote monitoring, diagnosis and self-maintenance;
+- for the unmanned SO&S platforms, to have positioning and communication capabilities for navigation, tracking and rescue;
+- to monitor and trace the SO&S platforms and the devices if they have harmful impacts on the marine environment.
+
+## **8 Requirements for information and communication technology implementation of smart oceans and seas**
+
+### **8.1 Service support requirements**
+
+- Location-based services. Service providers are recommended to obtain SO&S platform location information based on authorization and provide location-based services.
+- Traceability. It is recommended to provide traceability services at sea, e.g., tracing goods, seafood or marine pollutants.
+- Time synchronization. For time-sensitive services, time synchronization support capabilities are required, including time synchronization of device times within an SO&S platform internal network and between the SO&S platform internal and a marine communication networks.
+- Service prioritization. Service prioritization is required to be specified, so that service users can rank services according to their importance and optimize the use of limited resources on SO&S platforms.
+
+NOTE – Due to the limitation of maritime communication bandwidth and processing capacity, it is required to give high priority to important services, such as disaster alerts, and then deal with less important services, such as entertainment and news information.
+
+### **8.2 Communication requirements**
+
+- Regional temporary networking requirements. The ability rapidly to form regional broadband access is required for marine activities, such as maritime rescue.
+- Heterogeneous communication support. Support for integration of heterogeneous communication networks, such as satellite, short wave radio, and shore-based cellular communication, is required.
+- Communication control. Ability to control communication of an SO&S platforms is required to select the appropriate communication path and timing according to network conditions and the data for transmission, so as to improve communication efficiency and reduce cost.
+
+NOTE – For example, a large amount of oil consumption data would be transmitted to an onshore data centre until a ship approaches port, when it communicates through an onshore cellular network instead of satellite communication at much higher cost.
+
+- Communication prioritization. Networked SO&S platforms are required to prioritize communication tasks according to their importance and network conditions.
+- Device communication backup. Networked SO&S platforms are recommended to have backup means of communication.
+
+### **8.3 Platform requirements for smart oceans and seas**
+
+- Locating ability. Locating ability is required for SO&S platforms.
+- Heterogeneous locating ability: It is required to support more than one means of location and to provide coherent location information.
+
+NOTE – Location information is very important for SO&S platforms in many scenarios, such as marine rescue. There are many locating means, such as the automatic identification system [b-ITU-R M.585-8] and global navigation satellite system, with different coverages and precisions, and more than one means are usually used. When there are conflicts in location results, data fusion methods are required to generate a uniform location.
+
+- Uniform time reference: An SO&S platform is required to provide a uniform time reference for all its devices.
+- Uniform location reference. An SO&S platform is required to provide a uniform location reference for all its devices.
+- Gateway ability. An SO&S platform is required to provide a gateway to connect its internal network and marine communication network.
+- Status monitoring. An SO&S platform is required to monitor the status of its devices, networking status and the status of other important equipment, such as power supply.
+- Reporting ability. An SO&S platform is required to report its status information to its onshore operation service providers.
+
+### **8.4 Device requirements**
+
+- Status monitoring. An SO&S device is required to monitor its status.
+- Reporting ability. An SO&S device is required to report its status to the SO&S platform.
+- Locating ability. An SO&S device is required to obtain location information through its own location module or from an SO&S platform.
+- Remote maintenance. Remote maintenance capabilities, such as remote diagnostics, configurations and software updates, are required for SO&S devices.
+- Energy consumption management. An SO&S device is required to control its applications so as to manage its power consumption.
+- Environmentally friendly. It is required to take appropriate measures in the processes of device design, manufacture, installation and maintenance, to prevent and mitigate the harmful impacts of a device on the marine environment and the living world.
+
+### **8.5 Data management requirements**
+
+- Device data compression. It is recommended for an SO&S platform or its devices to compress data before transmission to reduce bandwidth usage, when the communication condition is limited.
+
+NOTE 1 – Limited communication condition refers to situations where the communication bandwidth is low and the communication cost is high.
+
+NOTE 2 – Data processing for extracting features is one data compression method.
+
+- Common data format. Common data format is required to transmit data between SO&S platforms, service providers and other data users.
+- Crucial data recording. SO&S platforms are required to record crucial data in real time and hold data after power loss.
+- Crucial data transmission recovery. If crucial data transmission is interrupted due to power loss or network interruption, SO&S platforms are required to recover the data transmission after power and network recovery.
+- Data encryption. Sensitive data is required to be encrypted when stored on SO&S platforms or transmitted over marine communication networks.
+
+## Appendix I
+
+### Use cases of SO&S
+
+(This appendix does not form an integral part of this Recommendation.)
+
+### I.1 Shipping
+
+- Ship transport management. For ships, reducing the operating cost and ensuring safe passage are important concerns in transport management. ICTs can provide integrated information services and auxiliary decision-making support for maritime shipping vessels, and realize the detailed management of vessels and optimize transport routes. With the help of ICTs, intelligent and unmanned ships can be used in maritime transport to reduce labour costs.
+- Marine trade. The use of ICTs enables maritime transport to seamlessly connect to urban logistics and e-trade systems, optimizes the entire logistics management process by acquiring the status of goods at sea and supports financial services such as insurance.
+- Smart ports. ICT improves port operation efficiency and cost-effectiveness.
+- Maritime supervision. Because oceans and seas may span different administrative areas, there are many difficulties in maritime supervision. ICTs provide governments and intergovernmental organizations with maritime regulatory means, such as ship identification, ship behaviour monitoring and ship sewage monitoring.
+
+### I.2 Marine fisheries
+
+- Marine fishery services. Provide services for marine environment and marine life activity monitoring, data analysis, early warning and other services for marine fisheries.
+- Marine fishing services. To provide meteorological, hydrological, environmental and other information services for fishing vessels and fleets, as well as value-added services including fishing detection services, remote monitoring, positioning and navigation, fleet management and emergency rescue information.
+- Aquatic product traceability. Support the identification and tracing of aquatic products.
+- Fisheries resource conservation. Monitor global fishery resources, evaluate maximum fishing capacity that can be adapted, monitor fishing vessel behaviour, identify violations and improve traceability of fish from fishing to transport so as to support governments to develop policies for restoration of marine fish resources, management of fisheries organizations and support of international action plans to prevent and eliminate illegal, unreported and unregulated fishing.
+
+### I.3 Resource exploitation
+
+- Marine resource exploration. Marine oil, gas and seabed deposits can be explored using various sensors and data analysis techniques.
+- Offshore operations services. ICTs can provide services including equipment health management, personnel safety and health management, and operation environment monitoring for offshore operations such as offshore oil and gas production.
+
+### I.4 Marine tourism
+
+- Public tourism services. ICTs can provide public services, such as for weather, tour guide, transportation, immigration and marine rescue information, for coastal, island and cruise ship tourism.
+
+### **I.5 Disaster warning**
+
+- Marine disaster warning services. ICTs can provide monitoring and early warning services for marine disasters such as tsunamis, typhoons, storm surges, sea ice and red tides, and enable different countries or institutions to share information and to cooperate.
+
+### **I.6 Maritime safety**
+
+Challenges to maritime security include maritime rescue, disaster relief, combating piracy, transnational crime at sea, drug trafficking, human trafficking and armed attacks. ICTs can provide the following support.
+
+- Monitoring and identification of maritime target information, such as vessel and personnel status and location information.
+- Rapidly deploying regional broadband networks and computing power to support offshore data, video, voice communications and information sharing.
+
+### **I.7 Environmental protection and tackling climate change**
+
+Marine environmental issues include marine environmental pollution and environmental degradation caused by climate change, including emissions of industrial, life, port pollutants, eutrophication caused by marine aquaculture, oil spills caused by offshore oil platform and tanker accidents, radioactive material discharge from nuclear power plant, ocean temperature rise due to climate change, ocean and coastal acidification, sea level rise, shrinking polar ice cover, coastal erosion and extreme weather events. The ICTs provide more effective means of monitoring the marine environment.
+
+- Various types of networked devices, such as distributed sensors, radar and remote sensing devices, reduce manual sampling, analysis and recording, and provide real-time environmental monitoring and accurate early warning.
+- Improve traceability of monitoring data.
+
+## Bibliography
+
+- [b-ITU-T Y.2091] Recommendation ITU-T Y.2091 (2011), *Terms and definitions for next generation networks*.
+- [b-ITU-T Y.4000] Recommendation ITU-T Y.4000/Y.2060 (2012), *Overview of the Internet of things*.
+- [b-ITU-R F.592-4] Recommendation ITU-R F.592-4 (2007), *Vocabulary of terms for the fixed service*.
+- [b-ITU-R M.585-8] Recommendation ITU-R M.585-8 (2019), *Assignment and use of identities in the maritime mobile service*.
+- [b-ITU-R M.1224-1] Recommendation ITU-R M.1224-1 (2012), *Vocabulary of terms for international mobile telecommunications (IMT)*.
+- [b-UNCLOS] United Nations (1982). *United Nations convention on the law of the sea*. Geneva:United Nations. 202 pp. Available [viewed 2021-12-17] at:
+[https://www.un.org/Depts/los/convention\\_agreements/texts/unclos/unclos\\_e.pdf](https://www.un.org/Depts/los/convention_agreements/texts/unclos/unclos_e.pdf)
+
+
+
+
+
+## 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 |
+| 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 | 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 |
\ No newline at end of file
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@@ -0,0 +1,644 @@
+
+
+# ITU-T
+
+TELECOMMUNICATION
+STANDARDIZATION SECTOR
+OF ITU
+
+## Y.4122
+
+(07/2021)
+
+SERIES Y: GLOBAL INFORMATION
+INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS,
+NEXT-GENERATION NETWORKS, INTERNET OF
+THINGS AND SMART CITIES
+
+Internet of things and smart cities and communities –
+Requirements and use cases
+
+# --- **Requirements and capability framework of the edge-computing-enabled gateway in the Internet of things**
+
+Recommendation ITU-T Y.4122
+
+## ITU-T Y-SERIES RECOMMENDATIONS
+
+## GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS, NEXT-GENERATION NETWORKS, INTERNET OF THINGS AND SMART CITIES
+
+## GLOBAL INFORMATION INFRASTRUCTURE
+
+| | |
+|-------------------------------------------|-------------|
+| General | Y.100–Y.199 |
+| Services, applications and middleware | Y.200–Y.299 |
+| Network aspects | Y.300–Y.399 |
+| Interfaces and protocols | Y.400–Y.499 |
+| Numbering, addressing and naming | Y.500–Y.599 |
+| Operation, administration and maintenance | Y.600–Y.699 |
+| Security | Y.700–Y.799 |
+| Performances | Y.800–Y.899 |
+
+## INTERNET PROTOCOL ASPECTS
+
+| | |
+|--------------------------------------------------------------------|---------------|
+| General | Y.1000–Y.1099 |
+| Services and applications | Y.1100–Y.1199 |
+| Architecture, access, network capabilities and resource management | Y.1200–Y.1299 |
+| Transport | Y.1300–Y.1399 |
+| Interworking | Y.1400–Y.1499 |
+| Quality of service and network performance | Y.1500–Y.1599 |
+| Signalling | Y.1600–Y.1699 |
+| Operation, administration and maintenance | Y.1700–Y.1799 |
+| Charging | Y.1800–Y.1899 |
+| IPTV over NGN | Y.1900–Y.1999 |
+
+## NEXT GENERATION NETWORKS
+
+| | |
+|-------------------------------------------------------------------|---------------|
+| Frameworks and functional architecture models | Y.2000–Y.2099 |
+| Quality of Service and performance | Y.2100–Y.2199 |
+| Service aspects: Service capabilities and service architecture | Y.2200–Y.2249 |
+| Service aspects: Interoperability of services and networks in NGN | Y.2250–Y.2299 |
+| Enhancements to NGN | Y.2300–Y.2399 |
+| Network management | Y.2400–Y.2499 |
+| Computing power networks | Y.2500–Y.2599 |
+| Packet-based Networks | Y.2600–Y.2699 |
+| Security | Y.2700–Y.2799 |
+| Generalized mobility | Y.2800–Y.2899 |
+| Carrier grade open environment | Y.2900–Y.2999 |
+
+## FUTURE NETWORKS
+
+### CLOUD COMPUTING
+
+### BIG DATA
+
+### QUANTUM KEY DISTRIBUTION NETWORKS
+
+## INTERNET OF THINGS AND SMART CITIES AND COMMUNITIES
+
+| | |
+|---------------------------------------------------------|----------------------|
+| General | Y.4000–Y.4049 |
+| Definitions and terminologies | Y.4050–Y.4099 |
+| Requirements and use cases | Y.4100–Y.4249 |
+| Infrastructure, connectivity and networks | Y.4250–Y.4399 |
+| Frameworks, architectures and protocols | Y.4400–Y.4549 |
+| Services, applications, computation and data processing | Y.4550–Y.4699 |
+| Management, control and performance | Y.4700–Y.4799 |
+| Identification and security | Y.4800–Y.4899 |
+| Evaluation and assessment | Y.4900–Y.4999 |
+
+For further details, please refer to the list of ITU-T Recommendations.
+
+## Recommendation ITU-T Y.4122
+
+# Requirements and capability framework of the edge-computing-enabled gateway in the Internet of things
+
+## Summary
+
+The gateway is an important component of Internet of things (IoT) systems, enabling IoT devices to connect to communication networks. Edge computing technologies can benefit the IoT, providing computation, storage, networking and intelligence in proximity to IoT devices.
+
+Compared with the common gateway [ITU-T Y.4101], the edge-computing-enabled gateway in the IoT (EC-enabled IoT gateway) has additional capabilities supporting service layer interworking, and application layer interworking between IoT devices, IoT platforms and IoT application servers. In addition, the EC-enabled IoT gateway supports data transmission capabilities for IoT applications sensitive to time, latency, jitter and packet loss.
+
+Based on the common requirements and capabilities of a gateway for IoT applications [ITU-T Y.4101] and IoT requirements for support of edge computing [ITU-T Y.4208], additional capabilities and capability framework of the edge-computing-enabled gateway in the IoT are specified. Examples of applicability of the edge-computing-enabled gateway in the IoT are also given.
+
+## History
+
+| Edition | Recommendation | Approval | Study Group | Unique ID* |
+|---------|----------------|------------|-------------|---------------------------------------------------------------------------|
+| 1.0 | ITU-T Y.4122 | 2021-07-14 | 20 | 11.1002/1000/14735 |
+
+## Keywords
+
+Capability, capability framework, edge computing, gateway, internet of things, IoT, requirement.
+
+---
+
+\* To access the Recommendation, type the URL in the address field of your web browser, followed by the Recommendation's unique ID. For example, .
+
+## 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 .
+
+© ITU 2021
+
+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 | Introduction of the edge-computing-enabled gateway in the IoT ..... | 3 |
+| 7 | Requirements of the edge-computing-enabled gateway in the IoT ..... | 3 |
+| | 7.1 Service layer interworking ..... | 4 |
+| | 7.2 Application layer interworking..... | 4 |
+| | 7.3 Network QoS and time sensitiveness ..... | 4 |
+| 8 | Capabilities of the edge-computing-enabled gateway in the IoT ..... | 4 |
+| | 8.1 Protocol translation capabilities ..... | 5 |
+| | 8.2 Data processing capabilities ..... | 5 |
+| | 8.3 Remote updating capabilities ..... | 5 |
+| | 8.4 Network support capabilities..... | 5 |
+| | 8.5 Management capabilities ..... | 6 |
+| 9 | Capability framework of the edge-computing-enabled gateway in the IoT ..... | 6 |
+| | 9.1 Application layer capabilities..... | 7 |
+| | 9.2 Service support and application support layer capabilities ..... | 8 |
+| | 9.3 Network layer capabilities..... | 8 |
+| | 9.4 Device layer capabilities..... | 8 |
+| | 9.5 Management capabilities ..... | 9 |
+| | 9.6 Security capabilities..... | 9 |
+| | Appendix I – Examples of applicability of the edge-computing-enabled gateway
in the IoT..... | 10 |
+| | I.1 EC-enabled IoT gateway in crane control ..... | 10 |
+| | I.2 EC-enabled IoT gateway in product inspection ..... | 11 |
+| | Bibliography..... | 13 |
+
+
+
+## Recommendation ITU-T Y.4122
+
+# Requirements and capability framework of the edge-computing-enabled gateway in the Internet of things
+
+# 1 Scope
+
+Compared with the common gateway [ITU-T Y.4101], the edge-computing-enabled gateway in the Internet of things (IoT) – abbreviated as the EC-enabled IoT gateway – has additional capabilities supporting service layer interworking and application layer interworking between IoT devices, IoT platforms and IoT application servers. In addition, the EC-enabled IoT gateway supports data transmission capabilities for IoT applications sensitive to time, latency, jitter and packet loss.
+
+Based on common requirements and capabilities of a gateway for IoT applications [ITU-T Y.4101] and IoT requirements for support of edge computing [ITU-T Y.4208], additional capabilities and a capability framework of the edge-computing-enabled gateway in the IoT are specified.
+
+The scope of this Recommendation includes:
+
+- The introduction of the EC-enabled IoT gateway;
+- The requirements of the EC-enabled IoT gateway;
+- The capabilities of the EC-enabled IoT gateway;
+- The capability framework of the EC-enabled IoT gateway.
+
+The appendix provides examples of applicability of the EC-enabled IoT gateway.
+
+NOTE – Direct communication of the EC-enabled gateway with other gateways in the IoT is out of scope of this Recommendation.
+
+# 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 Y.4000] Recommendation ITU-T Y.4000/Y.2060 (2012), *Overview of the Internet of Things*.
+- [ITU-T Y.4101] Recommendation ITU-T Y.4101/Y.2067 (2017), *Common Requirements and Capabilities of a Gateway for Internet of Things Applications*.
+- [ITU-T Y.4113] Recommendation ITU-T Y.4113 (2016), *Requirements of the Network for the Internet of Things*.
+- [ITU-T Y.4208] Recommendation ITU-T Y.4208 (2020), *Internet of Things Requirements for Support of Edge Computing*.
+
+# 3 Definitions
+
+## 3.1 Terms defined elsewhere
+
+This Recommendation uses the following terms defined elsewhere:
+
+**3.1.1 access control** [b-ITU-T F.500]: Method of controlling access to information held in the directory either for retrieval, managing or updating purposes.
+
+**3.1.2 authentication** [b-ITU-T Y.1271]: The act or method used to verify a claimed identity.
+
+**3.1.3 authorization** [b-ITU-T X.800]: The granting of rights, which includes the granting of access based on access rights.
+
+**3.1.4 gateway** [ITU-T Y.4101]: A unit in the Internet of things which interconnects the devices with the communication networks. It performs the necessary translation between the protocols used in the communication networks and those used by devices.
+
+**3.1.5 internet of things (IoT)** [ITU-T Y.4000]: A global infrastructure for the information society, enabling advanced services by interconnecting (physical and virtual) things based on existing and evolving interoperable information and communication technologies.
+
+NOTE 1 – Through the exploitation of identification, data capture, processing and communication capabilities, the IoT makes full use of things to offer services to all kinds of applications, whilst ensuring that security and privacy requirements are fulfilled.
+
+NOTE 2 – From a broader perspective, the IoT can be perceived as a vision with technological and societal implications.
+
+## 3.2 Terms defined in this Recommendation
+
+None.
+
+# 4 Abbreviations and acronyms
+
+This Recommendation uses the following abbreviations and acronyms:
+
+| | |
+|-------|-----------------------------------------|
+| APP | Application |
+| CPU | Central Processing Unit |
+| EC | Edge Computing |
+| IoT | Internet of Things |
+| PLC | Programmable Logic Controller |
+| QoS | Quality of Service |
+| SS&AS | Service Support and Application Support |
+
+# 5 Conventions
+
+In this Recommendation:
+
+The keywords "**is required to**" indicate a requirement which must be strictly followed and from which no deviation is permitted if conformance to this document is to be claimed.
+
+The keywords "**is recommended**" indicate a requirement which is recommended but which is not absolutely required. Thus, this requirement need not be present to claim conformance.
+
+The keywords "**can optionally**" and "**may**" indicate an optional requirement which is permissible, without implying any sense of being recommended. These terms are not intended to imply that the vendor's implementation must provide the option and the feature can be optionally enabled by the
+
+network operator/service provider. Rather, it means the vendor may optionally provide the feature and still claim conformance with the specification.
+
+The expressions "edge-computing-enabled gateway in the Internet of things (IoT)" and "edge-computing (EC)-enabled IoT gateway" are used interchangeably.
+
+# **6 Introduction of the edge-computing-enabled gateway in the IoT**
+
+The IoT is a global infrastructure that interconnects (physical and virtual) things and makes full use of things to offer services to all kinds of applications while ensuring security and privacy per corresponding requirements [ITU-T Y.4000].
+
+To realize the vision of the IoT, the gateway is an important component to support the interconnection of devices which cannot connect to communication networks directly.
+
+The EC-enabled IoT gateway is a kind of gateway with common gateway capabilities [ITU-T Y.4101] and additional capabilities for the support of edge computing.
+
+Compared with the common requirements and capabilities of a gateway in the IoT [ITU-T Y.4101], the EC-enabled IoT gateway can provide flexible capabilities and can cooperate efficiently with IoT technical components (e.g., IoT device, IoT platform, application server, IoT area network, access network [ITU-T Y.4113]).
+
+The EC-enabled IoT gateway can efficiently make usage of the capabilities of IoT application servers, IoT platforms and IoT devices, and this enables the gateway's self-configuration in order to fulfil the service requirements identified in [ITU-T Y.4208].
+
+IoT applications may be sensitive to time synchronization, latency, jitter, packet loss and other network quality of service (QoS) parameters. The EC-enabled IoT gateway can provide computation, storage, networking and intelligence in proximity to IoT devices, reducing network resource consumption (for example, spectrum and bandwidth resources) while meeting IoT application requirements at the same time.
+
+# **7 Requirements of the edge-computing-enabled gateway in the IoT**
+
+The EC-enabled IoT gateway supports common requirements of the gateway specified in [ITU-T Y.4101]. The additional requirements of the gateway for the support of edge computing are a key target of this Recommendation.
+
+Referring to the IoT reference model [ITU-T Y.4000] and the basic model of the network for the IoT [ITU-T Y.4113], the EC-enabled IoT gateway and the technical components interworking with it are shown in Figure 1.
+
+NOTE 1 – The service support and application support (SS&AS) layer is optional for some IoT devices.
+
+NOTE 2 – The IoT area network and the access network provide the underlying network connectivity for the EC-enabled IoT gateway and its interworking with other IoT technical components.
+
+
+
+Figure 1: EC-enabled IoT gateway and its interworking with other IoT technical components. The diagram shows three main components: an IoT device, an EC-enabled IoT gateway, and an IoT platform/IoT application server. Each component has a layered architecture. The IoT device and IoT platform/IoT application server have four layers: Application layer, Service support and application support layer (dashed box), Network layer, and Device layer. The EC-enabled IoT gateway has four layers: Application layer, Service support and application support layer, Network layer, and Device layer. The IoT device and EC-enabled IoT gateway are connected via an IoT area network. The EC-enabled IoT gateway and IoT platform/IoT application server are connected via an Access network. A reference Y.4122(21) is noted at the bottom right.
+
+**Figure 1 – EC-enabled IoT gateway and its interworking with other IoT technical components**
+
+## 7.1 Service layer interworking
+
+Compared with the gateway [ITU-T Y.4101], the EC-enabled IoT gateway is required to additionally support service layer interworking in order to enable collaboration between IoT devices, IoT platforms and IoT application servers.
+
+NOTE – As an example, the EC-enabled IoT gateway can support time-sensitive tasks on behalf of IoT devices.
+
+## 7.2 Application layer interworking
+
+Compared with the gateway [ITU-T Y.4101], it is recommended that the EC-enabled IoT gateway additionally support application layer interworking with IoT devices, IoT platforms and IoT application servers in order to enable application collaboration across these components.
+
+## 7.3 Network QoS and time sensitiveness
+
+Based on clauses 7.2.3 and 8.3.2 of [ITU-T Y.4208], "Internet of Things Requirements for Support of Edge Computing", compared with the common requirements of the gateway in the IoT [ITU-T Y.4101], it is recommended that the EC-enabled IoT gateway additionally support networking with bounded network QoS, including bounded latency, bounded jitter and bounded packet loss, between the EC-enabled IoT gateway and other IoT technical components.
+
+It is also recommended that the EC-enabled IoT gateway additionally support time-sensitive data transmission in order to ensure low latency and time synchronization between the EC-enabled IoT gateway and other IoT technical components.
+
+# 8 Capabilities of the edge-computing-enabled gateway in the IoT
+
+The EC-enabled IoT gateway supports the common capabilities of the gateway specified in [ITU-T Y.4101]. The additional capabilities of the gateway with support of edge computing are a key target of this document.
+
+Based on IoT requirements for the support of edge computing [ITU-T Y.4208], the functional framework and capabilities of the IoT [ITU-T Y.4401] and common capabilities of the gateway in the IoT [ITU-T Y.4101], the capabilities of the EC-enabled IoT gateway (for simplicity, "the gateway" in the following clauses) can be classified into the following categories: protocol translation capabilities, data processing capabilities, remote updating capabilities, network support capabilities and management capabilities.
+
+## **8.1 Protocol translation capabilities**
+
+Compared with the communication protocol translation capabilities specified in clause 8.2 of [ITU-T Y.4101], the gateway provides additional protocol translation capabilities in the SS&AS layer and/or application layer.
+
+The gateway is required to provide SS&AS layer protocol translation to support the generic support capabilities of the SS&AS layer.
+
+NOTE 1 – The generic support capabilities of the SS&AS layer are common capabilities which can be used by different IoT applications, such as data processing or data storage. These capabilities may also be invoked by specific support capabilities, e.g., to build other specific support capabilities [ITU-T Y.4000].
+
+Since computation, storage and intelligence may migrate from the IoT platforms and IoT application servers to the gateway, it is recommended that the gateway provide application layer protocol translation to support application layer interworking with IoT platforms and IoT application servers. Based on the protocol translation capabilities in the application layer, the gateway can cooperate with IoT platforms and IoT application servers with heterogeneous application layer protocols.
+
+It is recommended that the gateway provide application layer protocol translation to support application layer interworking with the IoT devices. Based on the protocol translation capabilities in the application layer, the gateway can manage IoT devices with heterogeneous application layer protocols.
+
+NOTE 2 – Refer to clause 8.3 of [ITU-T Y.4101] for more details.
+
+## **8.2 Data processing capabilities**
+
+The data processing capabilities of the gateway include data collecting capability, data storage capability, data analysis capability and data delivery capability.
+
+It is recommended that the gateway provide data processing capabilities to IoT platforms and IoT application servers so that IoT platforms and IoT application servers can deploy some data operations at the edge of the network. With respect to data operations in the IoT platforms and IoT application servers, due to shortened data transmission path and data processing capabilities provided by the gateway, processing speed may be increased.
+
+It is recommended that the gateway allocate or reserve data processing related resources (e.g., memory, central processing unit (CPU), data flow priority, bandwidth) according to requests from IoT platforms and IoT application servers in preset mode and/or dynamic mode.
+
+It is recommended that the gateway provide IoT devices with data storage, data analysis and data delivery capabilities in order to, on behalf of the IoT devices, collaborate with other IoT devices, IoT platforms and IoT application servers.
+
+NOTE – For example, the deployment of the data analysis capability in the gateway may allow the reduction of transmission latency and jitter against the deployment of the data analysis capability in remote IoT platforms and IoT application servers.
+
+## **8.3 Remote updating capabilities**
+
+To support service layer interworking and application layer interworking, it is recommended that the gateway provide remote updating capabilities, periodically or based on event triggering.
+
+The remote updating capabilities are required to enable software loading, starting, stopping, updating and unloading, as well as application (APP) hosting and other operations according to commands from IoT platforms and IoT application servers.
+
+## **8.4 Network support capabilities**
+
+In order to satisfy bounded network QoS, low latency and time synchronization requirements, the gateway is required to support time-sensitive data transmission capabilities (enabling technologies
+
+include, but are not limited to, frame pre-emption [b-IEEE 802.1Q], traffic scheduling and time synchronization [b-IEEE 802.1AS]).
+
+## **8.5 Management capabilities**
+
+### **8.5.1 Network access management**
+
+The gateway is required to support network access management and related protocols.
+
+The gateway is required to have self-healing ability in order to ensure normal connection and reconnection to the IoT area network and access network after normal restart and abnormal power failure.
+
+#### **8.5.2 Log management**
+
+The gateway is required to support log recording, including recording of system log, access log, firewall log, alarm log and other logs, which enables, for example, monitoring of login operations and gateway configuration operations, as well as of access operations that violate preset rules or policies (such as illegal attack, access to some Internet sites, etc.).
+
+The gateway is required to support the querying and clearing of log records.
+
+The gateway is required to support the time stamping of log records.
+
+The gateway is required to support a lack of loss of log records in case of power failure.
+
+It is recommended that the gateway support detection of abnormal log records.
+
+#### **8.5.3 Power management**
+
+It is recommended that the gateway have power management to manage the power status of the IoT devices which are connected to the gateway.
+
+NOTE – The management of the power status includes, but is not limited to, start, shutdown and restart of the power.
+
+It is recommended that the gateway provide IoT platforms and IoT application servers with power management to start, shutdown and restart the power of the gateway.
+
+### **8.5.4 Firmware management**
+
+The gateway is required to support firmware management from the IoT platforms and IoT application servers, including, but not limited to, firmware update and firmware fall-back.
+
+# **9 Capability framework of the edge-computing-enabled gateway in the IoT**
+
+The capability framework of EC-enabled gateway in the IoT is shown in Figure 2.
+
+The **application layer capabilities** provide application-dependent capabilities to applications of the EC-enabled IoT gateway in order to support application layer interworking between IoT devices, IoT platforms and IoT application servers. Application protocol translation, metadata management and service provisioning are basic capabilities.
+
+The **SS&AS layer capabilities** provide application-independent capabilities in order to support applications deployed in the EC-enabled IoT gateway. SS&AS layer protocol translation, hardware virtualization and scheduling are basic capabilities.
+
+The **network layer capabilities** include network quality monitoring and time-sensitive data transmission support, which are basic capabilities to support application layer interworking and service layer interworking.
+
+The **device layer capabilities** include interface and functionality support, which is a basic capability to support upper layer capabilities.
+
+The **management capabilities** include maintenance support, power management and firmware management.
+
+The **security capabilities** include authentication, authorization, encryption support and access control.
+
+
+
+| | | | | |
+|-------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------|--|--|------------------------------------------------------------------------------------------------------|
+| Security capabilities
Authentication
Authorization
Encryption support
Access control | Application layer capabilities
Application protocol translation Metadata management Service provisioning | | | Management capabilities
Maintenance support
Power management
Firmware management |
+| | SS&AS layer capabilities
SS&AS layer protocol translation Hardware virtualization Scheduling | | | |
+| | Network layer capabilities
Network quality monitoring Time-sensitive data transmission support | | | |
+| | Device layer capabilities
Interface and functionality support | | | |
+| | | | | |
+
+Y.4122(21)
+
+**Figure 2 – Capability framework of EC-enabled IoT gateway**
+
+## 9.1 Application layer capabilities
+
+#### 9.1.1 Application protocol translation
+
+According to clause 8.1, it is recommended that the gateway provide application protocol translation capability in order to support heterogeneous protocols at the application layer between IoT devices, IoT platforms and IoT application servers.
+
+#### 9.1.2 Metadata management
+
+According to clause 8.1, the gateway has the capability of protocol identification. Protocol related metadata is required to be managed.
+
+According to clause 8.2, the gateway provides data processing capabilities to IoT devices, IoT platforms and IoT application servers. The gateway is required to provide metadata management to enable these capabilities.
+
+The gateway is required to provide metadata management capability to support application layer interworking between IoT devices, IoT platforms and IoT application servers.
+
+Metadata addition, deletion, modification and lookup are four basic operations that metadata management is required to provide.
+
+#### 9.1.3 Service provisioning
+
+According to clause 8.2, the gateway is required to provide service provisioning capability to support application layer interworking between IoT devices, IoT platforms and IoT application servers. Via service provisioning capability, IoT platforms and IoT application servers can, for example, activate and deactivate the gateway (fully or partially, i.e., with only some specific capabilities).
+
+## **9.2 Service support and application support layer capabilities**
+
+### **9.2.1 SS&AS layer protocol translation**
+
+According to clause 8.1, in order to support the interworking of IoT devices with IoT platforms and IoT application servers, the gateway adapts the protocols between the IoT devices, IoT platforms and IoT application servers.
+
+According to clause 8.1, the gateway is required to provide a protocol translation capability in the SS&AS layer to support SS&AS layer interworking between IoT devices, IoT platforms and IoT application servers.
+
+#### **9.2.2 Hardware virtualization**
+
+According to clause 8.2, it is recommended that the gateway provide hardware virtualization capability in the SS&AS layer in order to support application software independence from the gateway's hardware.
+
+NOTE – Hardware virtualization aims to abstract the functionalities of the hardware and cover up the differences of the hardware in order to, for example, simplify the hardware development.
+
+#### **9.2.3 Scheduling**
+
+According to clause 8.2, the gateway is required to provide resource scheduling capability (for example, network priority scheduling of different application data flows), in order to support application layer interworking and SS&AS layer interworking.
+
+### **9.3 Network layer capabilities**
+
+#### **9.3.1 Network quality monitoring**
+
+According to clause 8.2, it is recommended that the gateway provide network quality monitoring capability as this is critical to effectively support interworking between the gateway, IoT platforms and IoT application servers, and make good usage of the network resources.
+
+It is recommended that the network quality monitoring capability collect network quality related data in order to support network quality analysis and network problem diagnosis (for example, data associated with wireless signal strength).
+
+It is recommended that the network quality monitoring capability report the network quality related data to IoT platforms and IoT application servers so that IoT platforms and IoT application servers can adjust their network strategy (e.g., traffic priorities, spectrum allocation) according to the network status, as appropriate.
+
+#### **9.3.2 Time-sensitive data transmission support**
+
+According to clause 8.4, the gateway is required to support time-sensitive data transmission capabilities.
+
+### **9.4 Device layer capabilities**
+
+### **9.4.1 Interface and functionality support**
+
+According to clause 8.4, the gateway is required to support network interfaces and corresponding functionalities to ensure time-sensitive data transmission with the IoT area network as well as the access network.
+
+### **9.5 Management capabilities**
+
+### **9.5.1 Maintenance support**
+
+According to clause 8.5.2, the gateway is required to provide maintenance capability to support recovery from errors, and restoration from previous backups.
+
+### **9.5.2 Power management**
+
+According to clause 8.5.3, it is recommended that the gateway provide power management capability in order to enable the IoT platforms and IoT application servers to manage the power of the gateway.
+
+NOTE – The IoT platforms and IoT application servers can invoke the power management capability provided by the gateway, for example, to lower the energy consumption of the gateway.
+
+According to clause 8.5.3, it is recommended that the gateway provide the IoT platforms and IoT application servers with power management capability in order to manage the power of the IoT devices connected with the gateway on their behalf.
+
+#### **9.5.3 Firmware management**
+
+According to clause 8.5.4, the gateway is required to provide firmware management capability, including, but not limited to, firmware release, firmware update and firmware fall-back, in order to enable interworking with IoT devices, IoT platforms and IoT application servers as appropriate.
+
+## **9.6 Security capabilities**
+
+### **9.6.1 Authentication**
+
+According to clauses 8.1, 8.2, 8.3 and 8.5, the gateway interworks with IoT platforms, IoT application servers and IoT devices.
+
+It is recommended that the gateway provide authentication capability, e.g., to verify the identity of the gateway's access requester. The access requester may include IoT devices, IoT platforms and IoT application servers.
+
+#### **9.6.2 Authorization**
+
+According to clauses 8.1, 8.2, 8.3 and 8.4, the gateway interworks with IoT platforms, IoT application servers and IoT devices. Authorization is necessary for the gateway to ensure that interworking operations work under proper rights.
+
+It is recommended that the gateway provide authorization capability, e.g., to grant the corresponding access rights to the access requester.
+
+#### **9.6.3 Encryption support**
+
+According to clauses 8.1, 8.2, 8.3 and 8.4, the gateway interworks with IoT platforms, IoT application servers and IoT devices. Some sensitive data may be transmitted: as an example, the data for power management of the production devices in a factory is critical to production safety.
+
+It is recommended that the gateway provide encryption support capability, including but not limited to support of encryption for storage and communication.
+
+NOTE – Communication encryption may be used between the gateway and other IoT technical components such as IoT devices, IoT platforms and IoT application servers.
+
+#### **9.6.4 Access control**
+
+According to clause 8.1, it is recommended that the gateway provide access control capability, e.g., to prevent access to information stored in the gateway itself in case no access right is granted to the requester.
+
+# Appendix I
+
+## Examples of applicability of the edge-computing-enabled gateway in the IoT
+
+(This appendix does not form an integral part of this Recommendation.)
+
+### I.1 EC-enabled IoT gateway in crane control
+
+In factories, the EC-enabled IoT gateway can be used to support interworking between the IoT platform and IoT devices in industrial deployments.
+
+Figure I.1 is an example of EC-enabled IoT gateway usage in crane control.
+
+Industrial cranes are large mechanical pieces of equipment which are composed of mechanical structures, sensors and actuators. Remote control of industrial cranes is usually used in large-scale factories, harbours and mines.
+
+
+
+The diagram illustrates the architecture of an EC-enabled IoT gateway in crane control. On the left, an industrial crane is shown with its mechanical structure, sensor, and actuator. It is connected to a PLC and an IoT area network. The IoT area network is connected to an EC-enabled IoT gateway, which is connected to an access network. The access network is connected to an edge cloud, which is connected to a PLC server and a video server. The video server is connected to a centre control room. A vehicle and a freighter are also shown connected to the IoT area network.
+
+Y.4122(21)
+
+Figure I.1: Example of EC-enabled IoT gateway usage in crane control. The diagram shows an industrial crane (mechanical structure, sensor, actuator) connected to a PLC and an IoT area network. The IoT area network is connected to an EC-enabled IoT gateway, which is connected to an access network. The access network is connected to an edge cloud, which is connected to a PLC server and a video server. The video server is connected to a centre control room. A vehicle and a freighter are also shown connected to the IoT area network.
+
+**Figure I.1 – Example of EC-enabled IoT gateway usage in crane control
+(PLC – programmable logic controller)**
+
+Figure I.2 shows typical crane control before the introduction of EC-enabled gateway usage.
+
+
+
+The diagram illustrates the typical crane control before the introduction of EC-enabled gateway usage. It shows an industrial crane (mechanical structure, sensor, actuator) connected to a PLC and an IoT area network. The IoT area network is connected to the PLC.
+
+Y.4122(21)
+
+Figure I.2: Typical crane control before the introduction of EC-enabled gateway usage. The diagram shows an industrial crane (mechanical structure, sensor, actuator) connected to a PLC and an IoT area network. The IoT area network is connected to the PLC.
+
+**Figure I.2 – Typical crane control before the introduction of EC-enabled gateway usage**
+
+With respect to Figure I.2, the basic process of crane control is as follows:
+
+1. The crane sensors collect status information relating to the crane;
+2. The crane sensors send this status information to the programmable logic controllers (PLCs);
+3. Based on the status provided by the crane sensors, the PLCs make decisions and send control commands to the crane actuators;
+4. The crane actuators execute the received commands;
+5. Based on the execution of the actuators, the crane performs the actions.
+
+The limitation of crane control without EC-enabled gateway usage is that when there is more than one PLC, these PLCs cannot make decisions collaboratively and efficiently.
+
+Compared with typical crane control before the introduction of EC-enabled gateway usage, the EC-enabled IoT gateway can provide resources, for example, computation, storage and network, to support the collaborative decision making of multiple PLCs, and can support interworking between the servers deployed at the central control room and the PLCs deployed on the field.
+
+As shown in Figure I.1, via the IoT area network, the gateway can support interworking between crane sensors, actuators, PLCs and other devices, for example, video cameras. Therefore, decision making can be based on statuses from multiple crane sensors and the control commands can be sent to multiple actuators. Cooperation between these actuators can then be achieved.
+
+Additionally, via access network, the gateway can support interworking between PLCs, PLC servers and other devices (for example, video cameras) and those devices' servers (for example, video servers). Therefore, decision making can not only be based on statuses from multiple crane sensors but can also be based on information from multiple servers deployed in the centre control room. The crane control can then cooperate with other equipment, for example, vehicles and freighters.
+
+In summary, the EC-enabled IoT gateway can help to improve the efficiency of crane control and broaden the scope of crane application.
+
+## I.2 EC-enabled IoT gateway in product inspection
+
+The EC-enabled IoT gateway can be used in product inspection. In order to improve the yield rate of products, they must pass through a strict inspection. The inspection is often composed of a complex set of test items. The IoT platform can deliver the test items or inspection models to the gateway. With the help of the gateway, the product inspection can be carried out more easily and efficiently.
+
+
+
+The diagram illustrates the workflow of an EC-enabled IoT gateway in product inspection. On the left, 'Industrial products' (represented by images of a metal rod and a flange) are captured by 'Cameras'. The cameras send data to an 'EC-enabled IoT gateway' (a blue server icon). This gateway is connected to an 'Edge cloud' (a dashed box containing a radio tower and a cloud icon). Inside the edge cloud is an 'IoT platform' (a box labeled 'IoT platform'). The IoT platform interacts with 'Model iteration' and 'Historic data' (represented by a blue cube icon). The edge cloud also connects to 'Mechanical arms' (a blue robotic arm icon), which can interact with the 'Industrial products'.
+
+Diagram illustrating the EC-enabled IoT gateway usage in product inspection. The diagram shows a flow from Industrial products to Cameras, which send data to an EC-enabled IoT gateway. The gateway connects to an Edge cloud containing an IoT platform. The IoT platform interacts with Model iteration and Historic data. The Edge cloud also connects to Mechanical arms, which can interact with the Industrial products.
+
+**Figure I.3 – Example of EC-enabled IoT gateway usage in product inspection**
+
+As shown in Figure I.3, the gateway can be used in product inspection:
+
+1. Cameras take photos of the industrial products;
+2. Cameras send these photos to the gateway;
+3. The gateway invokes a photo-based defect analysis program to inspect the defective products;
+4. When a defective product is found, the gateway controls mechanical arms to remove the defective product.
+
+To improve the accuracy of the analysis results of the photo-based defect analysis program, the edge cloud can keep a large amount of historical data from photos. Based on this historical data from photos, an inspection model for the photo-based defect analysis program can be iterated.
+
+When the model is iterated, the iterated inspection model can be sent to the gateway. Then the gateway is updated, and the yield rate may consequently be improved.
+
+The benefits of the EC-enabled IoT gateway in this use case include but are not limited to:
+
+1. That the gateway can be configured by the IoT platform in the edge cloud in Figure I.3, so that the capabilities of the gateway can be iteratively enhanced.
+
+2. That the gateway can support diverse IoT devices, for example, cameras and mechanical arms as shown in Figure I.3, so that cooperation between IoT devices can be achieved.
+3. That the gateway can provide data processing at the edge near to the production line, which may reduce pressure on the transport network and IoT platform, and enable real-time operations, for example, the removal of defective products from the production line.
+
+# Bibliography
+
+- [b-ITU-T F.500] Recommendation ITU-T F.500 (1992), *International public directory services*.
+- [b-ITU-T X.800] Recommendation ITU-T X.800 (2019) | ISO/IEC 9594-1:2019, *Information technology – Open Systems Interconnection – The Directory: Overview of concepts, models and services*.
+- [b-ITU-T Y.1271] Recommendation ITU-T Y.1271 (2014), *Framework(s) on network requirements and capabilities to support emergency telecommunications over evolving circuit-switched and packet-switched networks*.
+- [b-IEEE 802.1AS] IEEE 802.1AS (2011), *Standard for Local and Metropolitan Area Networks – Timing and Synchronization for Time-Sensitive Applications in Bridged Local Area Networks*.
+- [b-IEEE 802.1Q] IEEE 802.1Q (2014), *Standard for Local and Metropolitan Area Networks — Bridges and Bridged 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 |
+| 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 | 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 |
\ No newline at end of file
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+
+
+I n t e r n a t i o n a l T e l e c o m m u n i c a t i o n U n i o n
+
+**ITU-T**
+
+TELECOMMUNICATION
+STANDARDIZATION SECTOR
+OF ITU
+
+**Y.4451**
+
+(09/2016)
+
+SERIES Y: GLOBAL INFORMATION
+INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS
+AND NEXT-GENERATION NETWORKS, INTERNET OF
+THINGS AND SMART CITIES
+
+Internet of things and smart cities and communities –
+Frameworks, architectures and protocols
+
+# --- **Framework of constrained device networking in the IoT environments**
+
+Recommendation ITU-T Y.4451
+
+## ITU-T Y-SERIES RECOMMENDATIONS
+
+# GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS AND NEXT-GENERATION NETWORKS, INTERNET OF THINGS AND SMART CITIES
+
+| | |
+|--------------------------------------------------------------------|----------------------|
+| GLOBAL INFORMATION INFRASTRUCTURE | |
+| General | Y.100–Y.199 |
+| Services, applications and middleware | Y.200–Y.299 |
+| Network aspects | Y.300–Y.399 |
+| Interfaces and protocols | Y.400–Y.499 |
+| Numbering, addressing and naming | Y.500–Y.599 |
+| Operation, administration and maintenance | Y.600–Y.699 |
+| Security | Y.700–Y.799 |
+| Performances | Y.800–Y.899 |
+| INTERNET PROTOCOL ASPECTS | |
+| General | Y.1000–Y.1099 |
+| Services and applications | Y.1100–Y.1199 |
+| Architecture, access, network capabilities and resource management | Y.1200–Y.1299 |
+| Transport | Y.1300–Y.1399 |
+| Interworking | Y.1400–Y.1499 |
+| Quality of service and network performance | Y.1500–Y.1599 |
+| Signalling | Y.1600–Y.1699 |
+| Operation, administration and maintenance | Y.1700–Y.1799 |
+| Charging | Y.1800–Y.1899 |
+| IPTV over NGN | Y.1900–Y.1999 |
+| NEXT GENERATION NETWORKS | |
+| Frameworks and functional architecture models | Y.2000–Y.2099 |
+| Quality of Service and performance | Y.2100–Y.2199 |
+| Service aspects: Service capabilities and service architecture | Y.2200–Y.2249 |
+| Service aspects: Interoperability of services and networks in NGN | Y.2250–Y.2299 |
+| Enhancements to NGN | Y.2300–Y.2399 |
+| Network management | Y.2400–Y.2499 |
+| Network control architectures and protocols | Y.2500–Y.2599 |
+| Packet-based Networks | Y.2600–Y.2699 |
+| Security | Y.2700–Y.2799 |
+| Generalized mobility | Y.2800–Y.2899 |
+| Carrier grade open environment | Y.2900–Y.2999 |
+| FUTURE NETWORKS | Y.3000–Y.3499 |
+| CLOUD COMPUTING | Y.3500–Y.3999 |
+| INTERNET OF THINGS AND SMART CITIES AND COMMUNITIES | |
+| General | Y.4000–Y.4049 |
+| Definitions and terminologies | Y.4050–Y.4099 |
+| Requirements and use cases | Y.4100–Y.4249 |
+| Infrastructure, connectivity and networks | Y.4250–Y.4399 |
+| Frameworks, architectures and protocols | Y.4400–Y.4549 |
+| Services, applications, computation and data processing | Y.4550–Y.4699 |
+| Management, control and performance | Y.4700–Y.4799 |
+| Identification and security | Y.4800–Y.4899 |
+| Evaluation and assessment | Y.4900–Y.4999 |
+
+*For further details, please refer to the list of ITU-T Recommendations.*
+
+## Recommendation ITU-T Y.4451
+
+# Framework of constrained device networking in the IoT environments
+
+## Summary
+
+In Internet of things (IoT) environments, constrained devices, equipped with various low-power wireless interfaces, have connection capability to locally available networks for the purpose of interacting with the real world. Constrained devices have many different characteristics. Recommendation ITU-T Y.4451 specifies the framework of constrained device networking in the Internet of things (IoT) environments. This Recommendation therefore describes the concept and features of constrained device networking as well as network architectures of constrained device networking including functional requirements, such as fragmentation, reassembly, header compression, address configuration, network management, multi-hop routing protocol and higher layer considerations.
+
+This Recommendation specifies the framework of constrained device networking in the Internet of things (IoT) environments with respect to IoT device communications. This Recommendation describes the concept of constrained device networking in the IoT environments and the communication of constrained devices. This Recommendation also describes network architecture and mechanisms of constrained device networking.
+
+## History
+
+| Edition | Recommendation | Approval | Study Group | Unique ID* |
+|---------|----------------|------------|-------------|---------------------------------------------------------------------------|
+| 1.0 | ITU-T Y.4451 | 2016-09-13 | 20 | 11.1002/1000/13026 |
+
+## Keywords
+
+Constrained device networking, Internet of Things, IoT.
+
+---
+
+\* To access the Recommendation, type the URL in the address field of your web browser, followed by the Recommendation's unique ID. For example, .
+
+## 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 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 .
+
+© 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 ..... | 2 |
+| | 3.1 Terms defined elsewhere..... | 2 |
+| | 3.2 Terms defined in this Recommendation..... | 2 |
+| 4 | Abbreviations and acronyms ..... | 2 |
+| 5 | Conventions ..... | 2 |
+| 6 | Overview of constrained device networking in the IoT environments..... | 3 |
+| | 6.1 IoT environments and constrained device networking..... | 3 |
+| | 6.2 General characteristics of constrained devices..... | 3 |
+| 7 | Communication features and attributes ..... | 4 |
+| | 7.1 Features of constrained devices in IoT environment..... | 4 |
+| | 7.2 Considerations for constrained device networking ..... | 4 |
+| 8 | Constrained device network architectures ..... | 5 |
+| | 8.1 Network components..... | 5 |
+| | 8.2 Network topologies ..... | 5 |
+| | 8.3 Protocol stacks for constrained device networking..... | 7 |
+| 9 | Functional requirements of constrained device networking..... | 8 |
+| | 9.1 Fragmentation and reassembly ..... | 8 |
+| | 9.2 Header compression ..... | 9 |
+| | 9.3 Address configuration ..... | 9 |
+| | 9.4 Network management..... | 9 |
+| | 9.5 Higher layer considerations..... | 9 |
+| | 9.6 Multi-hop routing protocol..... | 9 |
+| 10 | Security considerations..... | 9 |
+| | Annex A – Network scalability in constrained devices ..... | 10 |
+| | Annex B – Mechanism for providing network stability through IP continuity of NFC
devices in the Internet..... | 12 |
+| | Bibliography..... | 15 |
+
+
+
+## Recommendation ITU-T Y.4451
+
+# Framework of constrained device networking in the IoT environments
+
+# 1 Scope
+
+The scope of this Recommendation includes the following:
+
+- An overview of constrained device networking in the IoT environments.
+- Communication of constrained devices.
+- Architectures of constrained device networking.
+- Functionalities of constrained device networking.
+
+# 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 G.9959] Recommendation ITU-T G.9959 (2015), *Short range narrow-band digital radiocommunication transceivers – PHY, MAC, SAR and LLC layer specifications*.
+- [ITU-T Y.4000] Recommendation ITU-T Y.4000/Y.2060 (2012), *Overview of the Internet of things*.
+- [ITU-T Y.4109] Recommendation ITU-T Y.4109/Y.2061 (2012), *Requirements for the support of machine-oriented communication applications in the next generation network environment*.
+- [IETF RFC 4862] IETF RFC 4862 (2007), *IPv6 Stateless Address Autoconfiguration*.
+- [IETF RFC 4944] IETF RFC 4944 (2007), *Transmission of IPv6 Packets over IEEE 802.15.4 Networks*.
+- [IETF RFC 5225] IETF RFC 5225 (2008), *RObust Header Compression Version 2 (ROHCv2): Profiles for RTP, UDP, IP, ESP and UDP-Lite*.
+- [IETF RFC 6282] IETF RFC 6282 (2011), *Compression Format for IPv6 Datagrams over IEEE 802.15.4-Based Networks*.
+- [IETF RFC 6550] IETF RFC 6550 (2012), *RPL: IPv6 Routing Protocol for Low-Power and Lossy Networks*.
+- [IETF RFC 7400] IETF RFC 7400 (2014), *6LoWPAN-GHC: Generic Header Compression for IPv6 over Low-Power Wireless Personal Area Networks (6LoWPANs)*.
+- [IETF RFC 7428] IETF RFC 7428 (2015), *Transmission of IPv6 Packets over ITU-T G.9959 Networks*.
+- [IETF RFC 7668] IETF RFC 7668 (2015), *IPv6 over BLUETOOTH(R) Low Energy*.
+- [IETF RFC 7721] IETF RFC 7721 (2016), *Security and Privacy Considerations for IPv6 Address Generation Mechanisms*.
+
+# 3 Definitions
+
+### 3.1 Terms defined elsewhere
+
+This Recommendation uses the following terms defined elsewhere:
+
+**3.1.1 device** [ITU-T Y.4000]: With regard to the Internet of things, this is a piece of equipment with the mandatory capabilities of communication and the optional capabilities of sensing, actuation, data capture, data storage and data processing.
+
+**3.1.2 Internet of things (IoT)** [ITU-T Y.4000]: A global infrastructure for the information society, enabling advanced services by interconnecting (physical and virtual) things based on existing and evolving interoperable information and communication technologies.
+
+NOTE 1 – Through the exploitation of identification, data capture, processing and communication capabilities, the IoT makes full use of things to offer services to all kinds of applications, whilst ensuring that security and privacy requirements are fulfilled.
+
+NOTE 2 – From a broader perspective, the IoT can be perceived as a vision with technological and societal implications.
+
+### 3.2 Terms defined in this Recommendation
+
+This Recommendation defines the following terms:
+
+**3.2.1 constrained device:** A device that has constraints on characteristics such as limited processing capability, small memory capability, limited battery power, short range and low bit rate.
+
+**3.2.2 adaptation layer:** A layer that is required for binding the network layer and the datalink layer in low-power network technologies.
+
+# 4 Abbreviations and acronyms
+
+This Recommendation uses the following abbreviations and acronyms:
+
+| | |
+|--------|------------------------------------------|
+| BLE | Bluetooth Low Energy |
+| IoT | Internet of Things |
+| LLCP | Logical Link Control Protocol |
+| LoWPAN | Low-power Wireless Personal Area Network |
+| MP2P | Multipoint-to-Point (MP2P) |
+| MTU | Maximum Transmission Unit |
+| NFC | Near Field Communication |
+| POS | Personal Operating Space |
+| P2MP | Point-to-Multipoint |
+| P2P | Point-to-Point |
+| QoS | Quality of Service |
+| SNMP | Simple Network Management Protocol |
+| SSAP | Source Service Access Point |
+
+# 5 Conventions
+
+None.
+
+# 6 Overview of constrained device networking in the IoT environments
+
+## 6.1 IoT environments and constrained device networking
+
+The ITU Report 2005 [b-ITU Report] states that Internet of things (IoT) can be defined as a vision "First, in order to connect everyday objects and devices to large databases and networks a simple, unobtrusive and cost-effective system of item identification is indispensable. Second, data collection can of course benefit from the ability to detect changes in the physical status of things. Finally, advances in miniaturization and nanotechnology mean that smaller and smaller things will have the ability to interact and connect".
+
+According to the vision of the IoT, the smaller things, i.e., constrained IoT devices, equipped with various low-power wireless interfaces (e.g., IEEE 802.15.4, Bluetooth low energy (BLE), near field communication (NFC), etc.), need to have connection capability to locally available networks for the purpose of interacting with the real world including non-constrained IoT devices, see example in Figure 1. Various types of advanced IoT services applications can be deployed using the different types of connections and interactions.
+
+
+
+The diagram shows a central cloud labeled "Network". Ten circular icons are arranged around the cloud, connected to it by dashed lines. The icons represent various IoT devices: a monitor, a pair of glasses, a yellow car, a smart meter, a smartphone, a traffic light, a smartwatch, a server, a desktop PC, and a tablet. A legend at the bottom indicates that yellow circles represent "Non-constrained devices" and grey circles represent "Constrained devices".
+
+Y.4451(16)\_F01
+
+Diagram illustrating connected constrained and non-constrained devices. A central cloud labeled 'Network' is connected via dashed lines to ten circular icons representing various devices. The devices are arranged in a circle around the network cloud. A legend at the bottom indicates that yellow circles represent 'Non-constrained devices' and grey circles represent 'Constrained devices'.
+
+Figure 1 – Connected constrained and non-constrained devices
+
+## 6.2 General characteristics of constrained devices
+
+To develop the advanced IoT services and applications, various aspects of the requirements should be considered in advance. One such aspect is the type of constraint that characterizes the IoT devices. Constraint types for IoT devices are listed as follows:
+
+- **Limited processing capability:** The constrained IoT devices have limited processing capability. For example, the smallest common low-power wireless personal area network (LoWPAN) nodes have 8-bit processors with clock rates of around 10 MHz. Other models exist with 16-bit and 32-bit cores (typically ARM7), running at frequencies in the range of tens of MHz.
+- **Small memory capacity:** In the case of monitoring and target-tracking IoT services, the constrained IoT devices have a limited memory capacity. These constrained IoT devices have a few kilobytes of RAM with a few dozen kilobytes of ROM/flash memory. While
+
+memory sizes of nodes continue to grow, the nature of small memory capacity for the constrained IoT devices remains a challenge.
+
+- **Limited battery power and low power consumption:** Wireless radios for mobile devices are normally battery-operated. For the sake of longevity, mobile devices should conserve energy and not waste the limited battery power.
+- **Short range:** The personal operating space (POS) defined by [b-IEEE 802.15.4] and Bluetooth LE implies a range of 10 metres and NFC implies a range of 10 centimetres. Likewise, almost all constrained IoT devices have short ranges.
+- **Low bit rate:** A maximum over-the-air rate of 250 kbit/s, which is most commonly used in current deployments, is defined in [b-IEEE 802.15.4]. Alternatively, three lower data rates of 20, 40 and 100 kbit/s are defined. Furthermore, the over-the-air data rate of Bluetooth LE is 1 Mbit/s and NFC is 424 kbit/s.
+
+# 7 Communication features and attributes
+
+## 7.1 Features of constrained devices in IoT environment
+
+As defined in [ITU-T Y.4000] and [ITU-T Y.4109], the communication and networking paradigms in the IoT environments are focused on the domain of devices and machines. The new dimension introduced in the IoT is communication and it includes the communication between computers, of human to human, of human to things and between things [b-ITU Report]. With regard to the IoT, things are objects of the physical world or the information world. Physical things exist in the physical world and are capable of being sensed, actuated and connected. Virtual things exist in the information world and are capable of being stored, processed and accessed. Physical things include devices and gateways. With regard to the IoT, the mandatory capability of a device is communication and optional capabilities are sensing, actuation, data capture, data storage and data processing. In [ITU-T Y.4000], there are three types of device communications;
+
+- Communication through the communication network via a gateway
+- Communication through the communication network without a gateway
+- Communication without using the communication network (directly)
+
+The devices in the IoT environments are heterogeneous and are based on different hardware and network access technologies. There are various types of IoT devices and some of them have low performance and limited functionality while others have powerful capabilities. Constrained IoT devices have different features of communication.
+
+### 7.2 Considerations for constrained device networking
+
+Some networking mechanisms such as routing protocols, address generation and network configuration are not suitable for the constrained IoT devices. Considerations for constrained device networking are as follows:
+
+- **Deployment:** Deployment can occur at once, or as an iterative process. The selected type of deployment has an impact on node density and location.
+- **Network size:** The network size takes into account devices that provide the intended network capability. The number of devices involved in a service could be small, moderate (several hundred), or large (over a thousand).
+- **Power source:** The power source of devices, which are battery-powered or mains-powered, influences the service and application design.
+- **Connectivity:** Devices can be considered "always connected" when there is a network connection among any two or more devices. However, due to external factors, such as mobility and device failures, network connectivity can be from "intermittent" to "sporadic".
+
+- **Multi-hop communication:** When there is a network connection among three or more devices, multi-hop communication can be required from a device to another device which is not directly connected, depending on their network topology.
+- **Traffic pattern:** Several traffic patterns may be used in point-to-multipoint (P2MP), multipoint-to-point (MP2P) and point-to-point (P2P) manners.
+- **Security level:** IoT services and applications may carry sensitive information and require high-level security support where the availability, integrity and confidentiality of the information are crucial.
+- **Mobility:** According to the wireless characteristics of IoT services and applications, devices can move or be moved around.
+- **Quality of service (QoS):** Parameters for QoS could consider collective data for latency, packet loss, data throughput and so on. In addition, QoS requirements can be different based on the data delivery model, such as event-driven, query-driven, continuous real-time and continuous non-real-time.
+
+# 8 Constrained device network architectures
+
+### 8.1 Network components
+
+Constrained devices having various network interface technologies (e.g., IEEE 802.15.4, Bluetooth low energy, near field communication, etc.) can communicate with each other in IoT environments. However, two or more devices having different network interfaces cannot communicate with each other directly and use a gateway with each of the two different network interfaces to relay data between the two heterogeneous devices. Likewise, network architectures, to which constrained devices belong, can be different from those of legacy networks.
+
+A constrained device network consists of constrained devices, gateways and proxies as follows:
+
+- **Constrained devices:** They have limited processing capability, small memory capability, limited battery power, short range and low bit rate; thus, they use low-energy based network interfaces, such as NFC, BLE, IEEE 802.15.4 and so on for networking.
+- **Gateways:** There are two types of gateways in constrained device networks. One type of gateway is a border gateway. The border gateway provides connectivity to a legacy network. The other type of gateway is an intermediate gateway. The intermediate gateway provides connectivity between two different constrained devices, such as a NFC device and a BLE device.
+
+### 8.2 Network topologies
+
+Constrained device networks have two types of network topologies and they are described as follows:
+
+- **Connected constrained device networks:** Connected constrained device networks are access networks which have connectivity to the legacy network. One of the constrained devices serves as a border gateway for connectivity to the legacy network. In addition, two different connected constrained device networks can be linked with each other by an intermediate gateway.
+- **Isolated constrained device networks:** Isolated constrained device networks do not have any connections to the legacy network, but they can have connections to other constrained device networks through intermediate gateways.
+
+#### 8.2.1 Connected constrained device networks
+
+Figure 2 shows an example of three connected networks to which different constrained devices belong.
+
+
+
+Y.4451(16)\_F02
+
+Figure 2: Connected constrained device networks. This diagram illustrates a network architecture where three types of constrained device networks (NFC, BLE, and IEEE 802.15.4) are connected to a central 'Network' cloud. The connections are made through 'Border gateways' (represented by circles). Additionally, 'Intermediate gateways' (represented by squares with a cross-hatch pattern) facilitate communication between these networks. The legend identifies the components: NFC devices (red circles), BLE devices (green circles), IEEE 802.15.4 devices (blue circles), and IEEE 802.11 devices (grey circles). Links are color-coded: NFC (red dashed), BLE (green dashed), IEEE 802.15.4 (blue dashed), and IEEE 802.11 (grey dashed).
+
+**Figure 2 – Connected constrained device networks**
+
+Three access networks, such as a NFC device network, a BLE device network and an IEEE 802.15.4 network as well as an IEEE 802.11 legacy network, are connected through border gateways. Furthermore, some heterogeneous devices (e.g., a NFC-enabled device and a Bluetooth device) are indirectly connected via an intermediate gateway having both a NFC interface and a Bluetooth interface. In this case, there are two communication types: one is a communication between two heterogeneous constrained devices and the other is a communication between a constrained device and a non-constrained device.
+
+#### 8.2.2 Isolated constrained device networks
+
+If each access network is not connected to the network, the constrained device networks become isolated networks as shown in Figure 3. In isolated constrained device networks, there are only communications between constrained devices.
+
+
+
+Y.4451(16)\_F03
+
+Figure 3: Isolated constrained device networks. This diagram shows the same three types of constrained device networks (NFC, BLE, and IEEE 802.15.4) as in Figure 2, but they are now isolated from the central 'Network' cloud. The networks are enclosed in dashed circles, and the connections to the network are removed. The legend identifies the components: NFC devices (red circles), BLE devices (green circles), IEEE 802.15.4 devices (blue circles), and Intermediate gateways (squares with a cross-hatch pattern). Links are color-coded: NFC (red dashed), BLE (green dashed), and IEEE 802.15.4 (blue dashed).
+
+**Figure 3 – Isolated constrained device networks**
+
+## 8.3 Protocol stacks for constrained device networking
+
+Low-power network interface technologies (e.g., IEEE 802.15.4, BLE, NFC, etc.) are equipped with constrained devices. Low-power network interface technologies have characteristics that differ from legacy network interfaces such as IEEE 802.11 [b-IEEE 802.11] and IEEE 802.3 [b-IEEE 802.3]. For example, they are specialized for less energy consumption in packet transmission. Therefore, the size of their maximum transmission unit (MTU) is smaller than that of IEEE 802.3 and IEEE 802.11.
+
+For this reason, an "adaptation layer" is required for binding the network layer and the datalink layer of low-power network interfaces. Figure 4 shows protocol stacks for constrained device networking. The adaptation layer supports packet header compression, packet fragmentation and reassembly and network address configurations, etc., for constrained device networking.
+
+These functions are related to network architectures and networking features, so capabilities of the adaptation layer can be included in the network layer in the IoT reference model of [ITU-T Y.4000].
+
+
+
+| |
+|-------------------|
+| Application |
+| Presentation |
+| Session |
+| Transport |
+| Network |
+| Adaptation |
+| Data link |
+| Physical |
+
+Y.4451(16)\_F04
+
+Figure 4: Protocol stacks for constrained device networking. A vertical stack of nine layers: Application, Presentation, Session, Transport, Network, Adaptation (highlighted with a thick border), Data link, and Physical. The label Y.4451(16)\_F04 is at the bottom.
+
+**Figure 4 – Protocol stacks for constrained device networking**
+
+Figure 5 and Figure 6 describe two types of constrained device networking. Figure 5 shows networking between two heterogeneous constrained devices, where the two heterogeneous constrained devices require an intermediate gateway to communicate with each other. Figure 6 shows networking between a constrained device and a non-constrained device.
+
+Figure 5 shows an example of networking between a NFC device and a BLE device.
+
+
+
+Y.4451(16)\_F05
+
+Figure 5: Protocol stacks for NFC device, Gateway, and BLE device. The NFC device stack has layers: Application, Presentation, Session, Transport, Network, Adaptation (red), Data link, and Physical. The Gateway stack has a central Network layer connected to two Adaptation layers (red and green), each with Data link and Physical layers below. The BLE device stack has layers: Application, Presentation, Session, Transport, Network, Adaptation (green), Data link, and Physical. Dashed arrows show connections between the Adaptation layers of the NFC device and Gateway, and between the Gateway and BLE device Adaptation layers. A dashed line also connects the Physical layers of the NFC device and Gateway. Another dashed line connects the Physical layers of the Gateway and BLE device.
+
+**Figure 5 – An example of constrained device networking**
+
+The NFC device should be indirectly connected to a Bluetooth device via a gateway that has both a NFC and a Bluetooth interface. Thus, the gateway has two adaptation layers, one for NFC and the other for Bluetooth.
+
+Figure 6 shows an example of the protocol stacks when a constrained device communicates with a non-constrained device in a legacy network. The constrained device belongs to an access network and is indirectly connected to the legacy network through a border gateway.
+
+
+
+Y.4451(16)\_F06
+
+Figure 6: Protocol stacks for NFC device, NFC border gateway, and IEEE 802.11. The NFC device stack has layers: Application, Presentation, Session, Transport, Network, Adaptation (red), Data link, and Physical. The NFC border gateway stack has a central Network layer connected to one Adaptation layer (red), which has Data link and Physical layers below. The IEEE 802.11 stack has layers: Application, Presentation, Session, Transport, Network, Data link, and Physical. Dashed arrows show connections between the Adaptation layer of the NFC device and the NFC border gateway, and between the Network layer of the NFC border gateway and the Network layer of the IEEE 802.11 stack. A dashed line also connects the Physical layers of the NFC device and NFC border gateway. Another dashed line connects the Physical layers of the NFC border gateway and IEEE 802.11.
+
+**Figure 6 – Example of networking between a constrained device and non-constrained device**
+
+# 9 Functional requirements of constrained device networking
+
+### 9.1 Fragmentation and reassembly
+
+The MAC/PHY protocol data units may be smaller than upper layer protocol data units. For example, the MTU of IEEE 802.15.4 is 127 bytes, but the minimum IPv6 packet size is 1280 bytes. The upper layer packet should be divided based on the size of lower layer protocol data unit. Then the divided packets, delivered to the destination device, should be reassembled into the original packet for the upper layer protocol [IETF RFC 4944]. Fragmentation and reassembly functions are required on the adaptation layer.
+
+### **9.2 Header compression**
+
+Given that in the worst case the maximum size available for transmitting IP packets over an IEEE 802.15.4 frame is 81 octets, while the IPv6 header is 40 octets long, (without optional headers), this leaves only 41 octets for upper-layer protocols, like UDP and TCP [IETF RFC 4944], [IETF RFC 6282], [IETF RFC 7400], [IETF RFC 5225]. This would lead to excessively fragmented packets. The upper layer headers should be compressed to the minimum in the adaptation layer.
+
+## **9.3 Address configuration**
+
+The adaptation layer is required for the stateless address autoconfiguration method for the network layer [IETF RFC 4944], [IETF RFC 7668], [IETF RFC 7428]. Stateless autoconfiguration [IETF RFC 4862] is effective for the protocol of the adaptation layer, because it reduces the configuration overhead on the constrained devices. There is a need for a method to generate a "network address" assigned to the constrained device. The network address can be generated with link layer identifiers of the constrained devices. Lengths of the link layer identifiers of the constrained devices may not be long enough for network scalability. Therefore, network address generation is required to extend network scalability and avoid address duplication. Annex A describes network scalability in constrained devices.
+
+In addition, when addresses are configured, network stability should be considered due to network connectivity and continuity. In the case that dynamic link layer addresses are used for the generation of network addresses, network sessions can be changed frequently. This would produce a negative effect on network stability. Annex B shows an example of a mechanism for providing stability through network continuity.
+
+## **9.4 Network management**
+
+The adaptation layer is required to address relevant network management solutions based on the resource constraints as well as the minimal configuration and self-healing functionality. The existing network management protocol (e.g., SNMP) can be widely used for monitoring data sources and sensors in conventional networks. However, network management protocol should be designed for the resource constraints, such as the memory, processing and message size constraints.
+
+## **9.5 Higher layer considerations**
+
+The networking performance also depends on the efficiency of application layer protocols. Heavyweight protocols may not be suitable for constrained devices. More compact higher layer protocols (e.g., at the application layer) may be required.
+
+## **9.6 Multi-hop routing protocol**
+
+Support of multi-hop routing protocol [IETF RFC 6550] is required. There are many existing multi-hop routing protocols, but these protocols are designed to use IP-based addresses with large overheads. For example, some routing protocol uses 48 octets for a route request based on IPv6 addressing. It is hard to use this routing protocol in constrained device networking.
+
+# **10 Security considerations**
+
+In constrained device networking, address configurations in the adaptation layer may have security issues, especially when generating network addresses by using link layer identifiers. Various security threats such as correlation of protocol over time, location tracking, device-specific vulnerability exploitation and address scanning may exist [IETF RFC 7721]. These threats should be mitigated.
+
+## Annex A
+
+### Network scalability in constrained devices
+
+(This annex forms an integral part of this Recommendation.)
+
+Constrained devices, which are based on low-power link layer technologies, such as Z-Wave [ITU-T G.9959], LoBAC (MS/TP), NFC, etc., use short addresses for node identifiers. This node identifier is used for a link layer address. For instance, NFC devices have a node identifier (i.e., SSAP) of 6 bits as shown in Figure A.1 and MS/TP devices have 8 bits. Such short length node identifiers can result in a scalability problem of the local network topology.
+
+
+
+| LLCP header | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | LLCP payload | | | | | | | | | | | | | | | | |
+|---------------|---|---|---|---|---|--------|---|---------------|---|--------|---|---|---|---|---|-------------------------|---|---|---|---|---|---|---|---------------------------------------|---|---|---|---|---|---|---|--------------|---|---|---|---|---|---|---|---|--|--|--|--|--|--|--|--|
+| DSAP | | | | | | PTYPE | | | | SSAP | | | | | | Sequence
N(S) N(R) | | | | | | | | | | | | | | | | Information | | | | | | | | | | | | | | | | |
+| 6 bits | | | | | | 4 bits | | | | 6 bits | | | | | | 0 or 8 bits | | | | | | | | | | | | | | | | M × 8 bits | | | | | | | | | | | | | | | | |
+| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | ... | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | | | | | | | | |
+| Byte offset 0 | | | | | | | | Byte offset 1 | | | | | | | | Byte offset 2 | | | | | | | | Byte offset 2 or 3 – depends on PTYPE | | | | | | | | | | | | | | | | | | | | | | | | |
+
+Y.4451(16)\_FA.1
+
+**Figure A.1 – Format of I PDU in NFC [b-LLCP1.1]**
+
+In an instance of NFC link layer, the maximum number of network device addresses using a node identifier length of 6 bits is $2^6$ . In other words, a local network of NFC can consist of $2^6$ devices at the most. Furthermore, the node identifier or source service access point (SSAP) is not a permanent physical value but temporary logical value. When two NFC devices make a connection, their SSAP values are created. As shown in Figure A.2, if $2^6+n$ devices belong to a local network, the $n$ devices can have redundant addresses. NFC link layer does not support mesh-under. This means redundant addresses can be created in not only the link layer but also in the network layer. This can result in a network scalability problem of constrained device networks.
+
+
+
+0 ID: 0×00
+
+1 ID: 0×01
+
+2 ID: 0×02
+
+⋮
+
+$2^6-2$ ID: 0×3e
+
+$2^6-1$ ID: 0×3f
+
+$2^6$ ID: 0×00
+
+$2^6+1$ ID: 0×01
+
+⋮
+
+$2^6+n-1$ ID: 0×??
+
+} $2^6$ constrained devices:
+identified
+
+} $n$ constrained devices:
+*NOT identified*
+→ redundant addresses
+
+Y.4451(16)\_FA.2
+
+Diagram showing a cloud of yellow nodes on the left. On the right, a vertical list of device indices and their corresponding IDs. Indices 0 to 2^6-1 map to IDs 0x00 to 0x3f and are grouped as '2^6 constrained devices: identified'. Indices 2^6 to 2^6+n-1 map to IDs 0x00 to 0x?? and are grouped as 'n constrained devices: NOT identified -> redundant addresses'.
+
+**Figure A.2 – Network scalability problem of a constrained device network**
+
+The solutions required to support two kinds of mechanisms are as follows:
+
+- Mechanisms for extending the limited network addresses
+- Mechanisms for avoiding network address duplication.
+
+NOTE – As one of possible mechanisms to extend the limited network address, there is an example method, which is applicable for various network schemes (e.g., IPv6), for redefining the short node identifier. The method comprises evenly defining two parts of the node identifier. The first part and the second part in the node identifier are located into a network address identifier. The network address identifier is also evenly separated into two parts with a predefined value. The first part of the node identifier is assigned to the first part of network address identifier and the second part of the node identifier is assigned to the second part of network address identifier. According to the network connecting condition of a communication device, one of the two parts of the network address identifier can additionally correspond to the other value except when assigning one of the parts of the node identifier for address duplication avoidance. Likewise, the new created network address identifier can be used for supporting extended size of a local constrained device network.
+
+## Annex B
+
+### Mechanism for providing network stability through IP continuity of NFC devices in the Internet
+
+(This annex forms an integral part of this Recommendation.)
+
+NFC devices have an extremely short radio range (i.e., 10cm), so they use a single-touch based approach to communicate between two devices. Every single-touch has a different network connection. Thus, Internet connection between them is also extremely short and can be unstable. Owing to such a physical constraint of NFC devices, mechanisms for providing network stability are required. Figure B.1 shows networking between two NFC devices based on the Internet as an example.
+
+
+
+The diagram illustrates the networking mechanism between two NFC devices based on the Internet. At the top, two NFC devices (represented by circuit boards) are shown, connected by a horizontal red dotted line. Below each device is a vertical protocol stack diagram. Each stack consists of the following layers from top to bottom: 'Upper layers', 'Network layer', 'Adaptation layer for NFC' (highlighted in pink), 'Binding to NFC' (highlighted in green), 'NFC logical link layer', and 'NFC physical layer'. A red dotted line connects the 'NFC physical layer' of the left stack to the 'NFC physical layer' of the right stack, representing the physical connection. The label 'Y.4451(16)\_FB.1' is located at the bottom right of the diagram.
+
+Diagram illustrating the networking mechanism between two NFC devices based on the Internet. Two NFC devices are shown at the top, connected by a dotted line. Below each device is a protocol stack diagram. The left stack consists of: Upper layers, Network layer, Adaptation layer for NFC (pink), Binding to NFC (green), NFC logical link layer, and NFC physical layer. The right stack is identical. A dotted line connects the NFC physical layers of both devices, passing through the Internet (labeled Y.4451(16)\_FB.1).
+
+**Figure B.1 – Example of networking between two NFC devices based on the Internet**
+
+To guarantee network stability through IP continuity, a cooperative mechanism of the adaptation layer for NFC and a "Binding to NFC" function of the NFC logical link layer are required. The binding to NFC function has the following operations:
+
+- Binding logical link layer address of the NFC to the adaptation layer
+- Caching logical link layer address for network connection
+
+In addition, each of the adaptation layers for NFC and binding to NFC requires an algorithm as shown in Figure B.2 and Figure B.3.
+
+- Adaptation layer for NFC
+
+
+
+```
+
+graph TD
+ Start([Start]) --> Init[IP continuity ← 0
+link layer node ID ← 0
+IPv6 IID ← 0]
+ Init --> IPReq{IP continuity
+required?}
+ IPReq -- Yes --> SetIP1[IP continuity ← 1]
+ IPReq -- No --> Request[Request for link layer node ID
+(parameters: IP continuity)]
+ SetIP1 --> Request
+ Request --> Conn1{{1}}
+ Conn2{{2}} --> CreateIID[IPv6 IID ← IPv6 IID created
+(parameters: link layer node ID)]
+ CreateIID --> IIDDup{IID duplicated?}
+ IIDDup -- Yes --> SetIP1
+ IIDDup -- No --> CreateIPv6[128 bit IPv6 creation
+(parameters: IPv6 IID)]
+ CreateIPv6 --> End([End])
+
+```
+
+Y.4451(16)\_FB.2
+
+Flowchart for requesting link layer node ID for IP continuity. The process starts with 'Start', initializes IP continuity and link layer node ID to 0, and IPv6 IID to 0. It then checks if IP continuity is required. If yes, it sets IP continuity to 1. If no, it requests a link layer node ID. Both paths lead to connector 1. From connector 2, it creates an IPv6 IID and checks if it's duplicated. If yes, it sets IP continuity to 1. If no, it creates a 128-bit IPv6 address and ends.
+
+**Figure B.2 – Algorithm for requesting link layer node ID for IP continuity**
+
+As a starting point, the adaptation layer for NFC checks whether IP continuity is required or not and then the result of IP continuity is delivered to binding to NFC.
+
+– Binding to NFC
+
+
+
+```
+
+graph TD
+ Conn1{{1}} --> Init[link layer node ID ← 0]
+ Init --> Random[link layer node ID ← 6 bit
+random value]
+ Random --> IPCont{IP continuity
+== 1 ?}
+ IPCont -- No --> SetCache0[cache ← 0]
+ IPCont -- Yes --> CacheEq0{cache == 0 ?}
+ CacheEq0 -- Yes --> SetCache[cache ← link layer node ID]
+ CacheEq0 -- No --> SetNodeID[link layer node ID ← cache]
+ SetCache0 --> Returns[link layer node ID returns
+(parameters: link layer node ID)]
+ SetCache --> Returns
+ SetNodeID --> Returns
+ Returns --> Conn2{{2}}
+
+```
+
+Y.4451(16)\_FB.3
+
+Flowchart for creating link layer node ID for IP continuity. It starts at connector 1, initializes link layer node ID to 0, then to a 6-bit random value. It checks if IP continuity is 1. If yes, it checks if cache is 0. If cache is 0, it sets cache to link layer node ID. If cache is not 0, it sets link layer node ID to cache. If IP continuity is not 1, it sets cache to 0. Both paths lead to returning the link layer node ID and connector 2.
+
+**Figure B.3 – Algorithm for creating link layer node ID for IP continuity**
+
+If IP continuity is required, binding to NFC returns a link layer node ID which is stored in cache. If the cache is empty, a new link layer node ID is created and stored in cache and is returned to the adaptation layer for NFC. When IP continuity is not required, the cache becomes empty and a newly created link layer node ID is just returned to the adaptation layer for NFC.
+
+## Bibliography
+
+- [b-ITU Report] ITU Internet Reports (2005), *The Internet of Things*.
+
+- [b-IEEE 802.3] IEEE Std. 802.3 (2012), *IEEE Standard for Ethernet*.
+
+- [b-IEEE 802.11] IEEE Std. 802.11 (2012), *IEEE Standard for Information technology – Telecommunications and information exchange between systems Local and metropolitan area networks-Specific requirements Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications*.
+
+- [b-IEEE 802.15.4] IEEE Std. 802.15.4 (2006), *IEEE Standard for Local and metropolitan area networks--Part 15.4: Low-Rate Wireless Personal Area Networks (LR-WPANs)*.
+
+- [b-LLCP1.1] NFC Forum Technical Specification (2011), *Logical Link Control Protocol version 1.1*.
+[http://members.nfc-forum.org/specs/spec\\_list/#llcp](http://members.nfc-forum.org/specs/spec_list/#llcp)
+
+
+
+
+
+## SERIES OF ITU-T RECOMMENDATIONS
+
+| | |
+|-----------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Series A | Organization of the work of ITU-T |
+| 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 | 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 |
\ No newline at end of file
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new file mode 100644
index 0000000000000000000000000000000000000000..e4d47d0cd1f20916066403b09e77136004057987
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@@ -0,0 +1,865 @@
+
+
+I n t e r n a t i o n a l T e l e c o m m u n i c a t i o n U n i o n
+
+# ITU-T
+
+TELECOMMUNICATION
+STANDARDIZATION SECTOR
+OF ITU
+
+## Y.4462
+
+(01/2020)
+
+SERIES Y: GLOBAL INFORMATION
+INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS,
+NEXT-GENERATION NETWORKS, INTERNET OF
+THINGS AND SMART CITIES
+
+Internet of things and smart cities and communities –
+Frameworks, architectures and protocols
+
+# --- **Requirements and functional architecture of open IoT identity correlation service**
+
+Recommendation ITU-T Y.4462
+
+## ITU-T Y-SERIES RECOMMENDATIONS
+
+## GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS, NEXT-GENERATION NETWORKS, INTERNET OF THINGS AND SMART CITIES
+
+## GLOBAL INFORMATION INFRASTRUCTURE
+
+| | |
+|-------------------------------------------|-------------|
+| General | Y.100–Y.199 |
+| Services, applications and middleware | Y.200–Y.299 |
+| Network aspects | Y.300–Y.399 |
+| Interfaces and protocols | Y.400–Y.499 |
+| Numbering, addressing and naming | Y.500–Y.599 |
+| Operation, administration and maintenance | Y.600–Y.699 |
+| Security | Y.700–Y.799 |
+| Performances | Y.800–Y.899 |
+
+## INTERNET PROTOCOL ASPECTS
+
+| | |
+|--------------------------------------------------------------------|---------------|
+| General | Y.1000–Y.1099 |
+| Services and applications | Y.1100–Y.1199 |
+| Architecture, access, network capabilities and resource management | Y.1200–Y.1299 |
+| Transport | Y.1300–Y.1399 |
+| Interworking | Y.1400–Y.1499 |
+| Quality of service and network performance | Y.1500–Y.1599 |
+| Signalling | Y.1600–Y.1699 |
+| Operation, administration and maintenance | Y.1700–Y.1799 |
+| Charging | Y.1800–Y.1899 |
+| IPTV over NGN | Y.1900–Y.1999 |
+
+## NEXT GENERATION NETWORKS
+
+| | |
+|-------------------------------------------------------------------|---------------|
+| Frameworks and functional architecture models | Y.2000–Y.2099 |
+| Quality of Service and performance | Y.2100–Y.2199 |
+| Service aspects: Service capabilities and service architecture | Y.2200–Y.2249 |
+| Service aspects: Interoperability of services and networks in NGN | Y.2250–Y.2299 |
+| Enhancements to NGN | Y.2300–Y.2399 |
+| Network management | Y.2400–Y.2499 |
+| Network control architectures and protocols | Y.2500–Y.2599 |
+| Packet-based Networks | Y.2600–Y.2699 |
+| Security | Y.2700–Y.2799 |
+| Generalized mobility | Y.2800–Y.2899 |
+| Carrier grade open environment | Y.2900–Y.2999 |
+
+## FUTURE NETWORKS
+
+Y.3000–Y.3499
+
+### CLOUD COMPUTING
+
+Y.3500–Y.3999
+
+## INTERNET OF THINGS AND SMART CITIES AND COMMUNITIES
+
+| | |
+|---------------------------------------------------------|----------------------|
+| General | Y.4000–Y.4049 |
+| Definitions and terminologies | Y.4050–Y.4099 |
+| Requirements and use cases | Y.4100–Y.4249 |
+| Infrastructure, connectivity and networks | Y.4250–Y.4399 |
+| Frameworks, architectures and protocols | Y.4400–Y.4549 |
+| Services, applications, computation and data processing | Y.4550–Y.4699 |
+| Management, control and performance | Y.4700–Y.4799 |
+| Identification and security | Y.4800–Y.4899 |
+| Evaluation and assessment | Y.4900–Y.4999 |
+
+For further details, please refer to the list of ITU-T Recommendations.
+
+## Recommendation ITU-T Y.4462
+
+# Requirements and functional architecture of open IoT identity correlation service
+
+## Summary
+
+Open Internet of things (IoT) identity correlation service (ICS), or open IoT ICS, is a service to map identities among devices, third party services, and transactions. Recommendation ITU-T Y.4462 specifies the reference architecture of open IoT ICS which supports Internet of things (IoT) devices to access multiple third party service providers. This Recommendation clarifies the concept of the open IoT ICS, identifies its basic capabilities and common requirements and also provides the reference architecture and relevant high-level common procedures for open IoT ICS.
+
+## History
+
+| Edition | Recommendation | Approval | Study Group | Unique ID* |
+|---------|----------------|------------|-------------|---------------------------------------------------------------------------|
+| 1.0 | ITU-T Y.4462 | 2020-01-13 | 20 | 11.1002/1000/14165 |
+
+## Keywords
+
+ICS, ID, identity mapping, IoT, platform.
+
+---
+
+\* To access the Recommendation, type the URL in the address field of your web browser, followed by the Recommendation's unique ID. For example, .
+
+## 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 .
+
+© ITU 2020
+
+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..... | 2 |
+| 4 | Abbreviations and acronyms ..... | 2 |
+| 5 | Conventions ..... | 3 |
+| 6 | Overview..... | 3 |
+| 7 | Requirements of open IoT identity correlation service ..... | 4 |
+| | 7.1 Requirements for establishing identity mapping..... | 4 |
+| | 7.2 Requirements for deleting identity mapping..... | 4 |
+| | 7.3 Requirements for querying identity mapping..... | 4 |
+| | 7.4 Security requirements..... | 4 |
+| 8 | Functional architecture of open IoT ICS ..... | 5 |
+| 9 | Reference points of open IoT ICS ..... | 6 |
+| 10 | Basic capabilities and common procedures of open IoT ICS ..... | 6 |
+| | 10.1 Identity mapping..... | 6 |
+| | 10.2 Identity de-mapping..... | 8 |
+| | 10.3 Identity relationship inquiry ..... | 9 |
+| | 10.4 Service provider authentication and access control..... | 10 |
+| 11 | Security considerations ..... | 11 |
+| | 11.1 Discovery mechanisms in identity information exchange..... | 11 |
+| | 11.2 Communication security..... | 12 |
+| | Appendix I – Use cases..... | 13 |
+| | I.1 Use case 1: Smart refrigerator ..... | 13 |
+| | I.2 Use case 2: Smart lock ..... | 13 |
+| | I.3 Use case 3: Device based service charge sharing..... | 14 |
+| | I.4 Use case 4: Promoting data package sharing between different services ..... | 15 |
+| | Bibliography..... | 16 |
+
+
+
+## Recommendation ITU-T Y.4462
+
+# Requirements and functional architecture of open IoT identity correlation service
+
+## 1 Scope
+
+This Recommendation provides information on the:
+
+- Concept and requirements of the open Internet of things (IoT) identity correlation service.
+- Functional architecture of the open IoT identity correlation service.
+- Basic capabilities, relevant reference points and procedures of the open IoT identity correlation service.
+
+## 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 G.9961] Recommendation ITU-T G.9961 (2018), *Unified high-speed wireline-based home networking transceivers – Data link layer specification*.
+- [ITU-T Q.1743] Recommendation ITU-T Q.1743 (2016), *IMT-Advanced references to Release 11 of LTE-Advanced evolved packet core network*.
+- [ITU-T X.1570] Recommendation ITU-T X.1570 (2011), *Discovery mechanisms in the exchange of cybersecurity information*.
+- [ITU-T Y.4000] Recommendation ITU-T Y.4000/Y.2060 (2012), *Overview of the Internet of things*.
+- [ITU-T Y.4100] Recommendation ITU-T Y.4100/Y.2066 (2014), *Common requirements of the Internet of things*.
+- [ITU-T Y.4203] Recommendation ITU-T Y.4203 (2019), *Requirements of things description in the Internet of things*.
+- [IETF RFC 4122] IETF RFC 4122 (2005), *A Universally Unique Identifier (UUID) URN Namespace*.
+- [IETF RFC 8446] IETF RFC 8446 (2018), *The Transport Layer Security (TLS) Protocol Version 1.3*.
+
+## 3 Definitions
+
+### 3.1 Terms defined elsewhere
+
+This Recommendation uses the following terms defined elsewhere:
+
+**3.1.1 device** [ITU-T Y.4000]: With regard to the Internet of things, this is a piece of equipment with the mandatory capabilities of communication and the optional capabilities of sensing, actuation, data capture, data storage and data processing.
+
+**3.1.2 identifier** [b-ITU-T Y.2091]: An identifier is a series of digits, characters and symbols or any other form of data used to identify subscriber(s), user(s), network element(s), function(s), network entity(ies) providing services/applications, or other entities (e.g., physical or logical objects). Identifiers can be used for registration or authorization. They can be either public to all networks, shared between a limited number of networks or private to a specific network (private IDs are normally not disclosed to third parties).
+
+**3.1.3 identity management** [b-ITU-T X.1252]: A set of functions and capabilities (e.g., administration, management and maintenance, discovery, communication exchanges, correlation and binding, policy enforcement, authentication and assertions) used for assurance of identity information (e.g., identifiers, credentials, attributes); assurance of the identity of an entity and supporting business and security applications.
+
+**3.1.4 Internet of things (IoT)** [ITU-T Y.4000]: A global infrastructure for the information society, enabling advanced services by interconnecting (physical and virtual) things based on existing and evolving interoperable information and communication technologies.
+
+NOTE 1 – Through the exploitation of identification, data capture, processing and communication capabilities, the IoT makes full use of things to offer services to all kinds of applications, whilst ensuring that security and privacy requirements are fulfilled.
+
+NOTE 2 – In a broad perspective, the IoT can be perceived as a vision with technological and societal implications.
+
+**3.1.5 device ID** [ITU-T G.9961]: A unique identifier allocated to a node operating in the network by the domain master during registration.
+
+### **3.2 Terms defined in this Recommendation**
+
+This Recommendation defines the following terms:
+
+**3.2.1 IoT identity correlation service:** IoT identity correlation service or IoT ICS, is a service to map relationships among the identities of Internet of things (IoT) related entities (e.g., devices, services and transactions) and also open the capabilities to third party applications.
+
+**3.2.2 unique transaction identifier (UTI):** An identifier that is generated by a third party service provider upon the initial authorization by the user and made available to the open Internet of things (IoT) identity correlation service (ICS). This identifier needs to be globally unique, anonymous and revocable.
+
+**3.2.3 IoT device serial number:** A provenance information related to the Internet of things (IoT) device so that each of the IoT devices can be identified physically, as described in [ITU-T Y.4203].
+
+## **4 Abbreviations and acronyms**
+
+This Recommendation uses the following abbreviations and acronyms:
+
+| | |
+|-----|------------------------------|
+| BSS | Business Service System |
+| ICS | Identity Correlation Service |
+| ID | Identity |
+| IdM | Identity Management |
+| IoT | Internet of Things |
+| PKI | Public Key Infrastructure |
+| SP | Service Provider |
+| TLS | Transport Layer Security |
+| URI | Uniform Resource Identifier |
+
+UTI Unique Transaction Identifier
+
+**5 Conventions**
+
+In this Recommendation:
+
+ The keywords "**is required to**" indicate a requirement which must be strictly followed and from which no deviation is permitted if conformance to this document is to be claimed.
+
+ The keywords "**is recommended**" indicate a requirement which is recommended but which is not absolutely required. Thus this requirement need not be present to claim conformance.
+
+**6 Overview**
+
+The Internet of things (IoT) as described in [ITU-T Y.4000] has become an important area in the telecommunication and information technology industry. In recent years, many new and novel services based on IoT technologies have emerged in the market and many of them have been deployed widely.
+
+Many of these IoT systems already have IoT identity management. The interoperability between those systems is required, for example, to leverage existing mechanism for the open IoT identity correlation service (open IoT ICS) which maps the third party services and IoT devices to provide identity mapping service, etc.
+
+
+
+```
+
+ graph LR
+ subgraph "IoT device (Refrigerator)"
+ D[Refrigerator Image]
+ end
+
+ subgraph "IoT service provider (Refrigerator company cloud)"
+ C[Cloud Icon]
+ end
+
+ ICS((Open IoT ICS))
+
+ subgraph "Third-party service provider A"
+ SPA[Cloud Icon]
+ subgraph "Service applications by service provider A to N"
+ APP[Smartphones Image]
+ end
+ end
+
+ subgraph "Third-party service provider N"
+ SPN[Cloud Icon]
+ end
+
+ D -- "Order service" --> C
+ C -- "Set up" --> ICS
+ C -- "Order service" --> SPA
+ ICS -- "Set up" --> SPA
+ SPA -- "Notification" --> APP
+
+ C -- "Order service" --> SPN
+ ICS -- "Set up" --> SPN
+ SPN -- "Notification" --> APP
+
+```
+
+Detailed description: The diagram illustrates the flow of 'Order service', 'Set up', and 'Notification' between various entities. An IoT device (refrigerator) sends an 'Order service' request to its IoT service provider (refrigerator company cloud). This cloud provider interacts with an 'Open IoT ICS' and multiple 'Third-party service providers' (A and N). 'Set up' signals occur between the cloud and Open IoT ICS, and between Open IoT ICS and the third-party providers. 'Order service' signals also flow from the cloud to the third-party providers. Finally, 'Notification' signals are sent from the third-party providers to 'Service applications' on mobile devices.
+
+Figure 1 – Overview of open IoT ICS function
+
+**Figure 1 – Overview of open IoT ICS function**
+
+As shown in Figure 1, the user may hold several accounts in different third party service providers who can provide a variety of services, such as online shopping service, digital movie and music rental service and e-commerce. Also, the IoT device (for example, a smart refrigerator) has connected to its own IoT service provider which is allocated in the IoT device manufacturer's cloud. The IoT service provider offers cloud-based IoT device management functionalities, such as notification, instruction, firmware updating, etc. The IoT service provider which runs on the IoT device manufacturer's cloud needs to associate with third party service provider(s) to obtain a variety of services for the IoT device. For instance, the smart refrigerator could order eggs from an online market (third party service) automatically when it detects that the eggs stock is running low, or play on-demand songs using refrigerator's internal speaker from a music rental company (third party service).
+
+Typically, an IoT device only has access to its own IoT service provider, but has limited access to other third party service providers. So, IoT devices can only acquire services from an IoT service
+
+ Rec. ITU-T Y.4462 (01/2020) 3
+
+provider, but may not be able to fully utilize a variety of third party services provided by other entities or enterprises. In order to let the IoT device access multiple third party services, the open IoT identity correlation service (open IoT ICS) provides an effective way to connect an IoT service provider and various third party service providers, then the IoT device can access the third party services via the relationship mapped by open IoT ICS. The open IoT ICS provides the identity mapping as a service for the IoT service provider(s) and third party service provider(s). Also, the open IoT ICS shall be a non-proprietary service and service provider independent and irrespective of the IoT device vendor or vertical industry.
+
+The open IoT ICS shall map the third party services and the IoT device. In order to form relationship mapping, a unique transaction identifier (UTI) provided by third party service providers, an identifier of a certain service, and an identifier of an IoT device need to be filled in a mapping relationship. Once the mapping relationship is established, via the IoT service provider, the IoT device could be able to request multiple services from third party service providers, as shown in Figure 1. The open IoT ICS shall provide the identifier of a service and a UTI to the IoT device, and the IoT device could use this information to request third party services.
+
+## **7 Requirements of open IoT identity correlation service**
+
+### **7.1 Requirements for establishing identity mapping**
+
+The open IoT ICS is required to collect the identifier of an IoT device, service and UTI. The open IoT ICS is required to provide the mapping function for the identifier that it has collected. Through the identity mapping function, the open IoT ICS establishes the mapping of the specific IoT device to single or multiple third party services that the user has selected.
+
+### **7.2 Requirements for deleting identity mapping**
+
+The open IoT ICS is required to delete identity mapping in one or more of following situations:
+
+- IoT device is unregistered from IoT service provider.
+- The UTI is invalid.
+- The third party service is invalid.
+- The third party service no longer authorized by the user.
+
+### **7.3 Requirements for querying identity mapping**
+
+The open IoT ICS is required to respond with the identity mapping information, including the identifier of the IoT device, the identifier of the service, and a UTI when an IoT device (via IoT service provider) or third party service provider query the identity mapping.
+
+### **7.4 Security requirements**
+
+The open IoT ICS is required to provide authorization and access control functions for IoT service provider(s) and third party service provider(s) to prevent unauthorized access to the open IoT ICS.
+
+To initialize a connection between an IoT service provider and any third party service provider(s) using the open IoT ICS, it is required that the entities are entered in a commercial contract or agreement governing this relationship prior to initialization. Moreover, user consent and agreement to using a third party service shall also be required before initializing this connection.
+
+The open IoT ICS is required to provide an authorization mechanism for IoT service provider(s), and third party service provider(s) before establishing, deleting and querying identity mapping. The third party service provider is only authorized to access data that are strictly relevant to its own service provision and any IoT device is only authorized to access data relevant to services with which it has an initialized and unrevoked connection.
+
+NOTE – This Recommendation will not define how to initialize connection among the open IoT ICS, IoT service provider(s), and third party service provider(s).
+
+## 8 Functional architecture of open IoT ICS
+
+The functional architecture of open IoT ICS is presented in Figure 2.
+
+
+
+Y.4462(20)\_F02
+
+Figure 2: Functional architecture of open IoT ICS. The diagram shows a layered architecture. At the top, a dashed box contains 'Third party service provider' and 'IoT service provider'. Below this is the 'Service and application layer'. In the center, a solid box labeled 'Open IoT identity correlation service' contains four functional entities: 'Identity mapping', 'Identity de-mapping', 'Service provider authentication and access control', and 'Identity relationship inquiry'. Above this box are eight ICS components labeled ICS-1 through ICS-8. At the bottom are two dashed boxes: 'Network layer' and 'Device layer'. Lines indicate connections from the service providers through the ICS components to the functional entities, and from the functional entities through the network and device layers.
+
+**Figure 2 – Functional architecture of open IoT ICS**
+
+The open IoT ICS has four functional entities: identity mapping, identity de-mapping, identity relationship inquiry and finally service provider authentication and access control functions.
+
+A brief description of these four functional entities of open IoT ICS is provided below:
+
+- **Identity mapping:** This function is used to create a mapping table between multiple identities of IoT related entities (UTI, IoT device and third party service). The identity mapping table contains three elements: device ID, service URI and unique transaction identifier (UTI). The identity mapping table will be stored in the open IoT ICS.
+- **Identity de-mapping:** This function is used to delete the mapping between multiple identities of IoT related entities (UTI, IoT device and third party service). Both IoT service provider and third party service providers can request to delete the identity mapping table through this function.
+- **Identity relationship inquiry:** This function is used to query the identity mapping of IoT related entities (UTI, IoT device and third party services) and check on the existence of the identity mapping before the interaction between the IoT device and third party service(s).
+- **Service provider authentication and access control:** This function is used to manage the access control and provide an authentication service to IoT service provider and third party services.
+
+NOTE – The IoT service provider will provide identity management (IdM) for the IoT device. The IdM is outside of the scope in this Recommendation.
+
+## 9 **Reference points of open IoT ICS**
+
+A description of reference points of open IoT ICS, as shown in Figure 2, is provided below:
+
+- ICS-1: Reference point ICS-1 supports communication between a third party service provider and open IoT ICS. It enables the open IoT ICS to interact with the third party service provider in order to provide the identity mapping function.
+- ICS-2: Reference point ICS-2 supports communication between the IoT service provider and open IoT ICS. It enables the open IoT ICS to interact with the IoT service provider in order to provide the identity mapping function.
+- ICS-3: Reference point ICS-3 supports communication between a third party service provider and open IoT ICS. It enables the open IoT ICS to interact with the third party service provider in order to provide the identity de-mapping function.
+- ICS-4: Reference point ICS-4 supports communication between the IoT service provider and open IoT ICS. It enables the open IoT ICS to interact with the IoT service provider in order to provide the identity de-mapping function.
+- ICS-5: Reference point ICS-5 supports communication between a third party service provider and open IoT ICS. It enables the open IoT ICS to interact with the third party service provider in order to provide security functions as needed, such as authentication and access control.
+- ICS-6: Reference point ICS-6 supports communication between an IoT service provider and open IoT ICS. It enables the open IoT ICS to interact with the IoT service provider in order to provide security functions as needed, such as authentication and access control.
+- ICS-7: Reference point ICS-7 supports communication between a third party service provider and open IoT ICS. It enables the open IoT ICS to interact with the third party service provider in order to provide the identity relationship inquiry function.
+- ICS-8: Reference point ICS-8 supports communication between an IoT service provider and open IoT ICS. It enables the open IoT ICS to interact with the IoT service provider in order to provide the identity relationship inquiry function.
+
+## 10 **Basic capabilities and common procedures of open IoT ICS**
+
+### 10.1 **Identity mapping**
+
+The identity mapping function is used to map the relationship between multiple identities of IoT related entities.
+
+The open IoT ICS establishes a service relationship among the identities of IoT related entities - between devices, services and transactions. In this case, a mapping table with a flat data model [b-FG-DPM TS D2.3] should be established, which consists of a two-dimensional array of data elements where all elements of a given row are related to one another and all elements of a given column are similar objects. For example, a single row of the mapping table consists of the device ID, service URI and UTI which are related to each other, as shown in Table 1.
+
+Table 1 shows the elements involved in the identity mapping function.
+
+**Table 1 – Identity mapping table**
+
+| | | |
+|-----------|-------------|-----|
+| Device ID | Service URI | UTI |
+|-----------|-------------|-----|
+
+The description of each element in Table 1 is as follows:
+
+- Device ID: For each IoT device which registered in the IoT service provider. The IoT service provider shall define and assign a unique, anonymous, and revocable identifier (Device ID [ITU-T G.9961]) for the individual IoT device. The revocation function that solely performed by IoT service provider.
+
+NOTE 1 – This Recommendation will not define the format of device ID.
+
+- Service URI: A URI provided by a third party service provider to indicate a specific service that the user selects in their third party service application [ITU-T Q.1743].
+
+NOTE 2 – This Recommendation will not define the format of service URI.
+
+- UTI: A unique transaction identifier (UTI) is an identifier to identify a user transaction that is generated by the third party service provider upon the authorization by the user. UTI is defined in the clause 3.2.2. The relationship between the specific IoT device and a third party service provider is identified with this unique transaction identifier. Upon establishing a mapping, both the IoT device and user (via the service provider) should be able to revoke an Identifier to signal that the relationship is terminated and transactions are no longer authorized. This UTI shall be administered by the third party service provider who generated it until this UTI has been revoked. A framework describing how to create an identifier that meets these requirements is described in [IETF RFC 4122].
+
+To initiate the process of establishing an identity mapping, the user of a third party service shall execute the following operations:
+
+- Step 1.1: The user shall login in the service application which is a service enabler deployed by third party service provider [ITU-T Q.1743].
+- Step 1.2: The user collects the IoT device serial number using the service application from the IoT device casing that manufacturer physically printed.
+- Step 1.3: The user selects the service offered by the third party service provider that plans to have the interact with the IoT device.
+- Step 1.4: The service application informs the third party service provider that it is ready to initiate the identity mapping process with open IoT ICS, and send the IoT device serial number and user selected service to the third party service provider.
+- Step 1.5: The third party service provider can start the identity mapping process with open IoT ICS.
+
+By accomplishing these steps, the third party service provider gains the following identities:
+
+- Service URI which is generated by the third party service provider based on the service that the user selects in step 1.3.
+- UTI which is generated by the third party service provider based on the login account in step 1.1.
+- IoT device serial number that the user scanned or typed in step 1.2.
+
+The process of establishing a mapping between the device ID, the service URI and the UTI is shown in Figure 3 and described below:
+
+
+
+```
+
+sequenceDiagram
+ participant IoT_device as IoT device
+ participant IoT_service_provider as IoT service provider
+ participant Open_IoT_ICS as Open IoT identity correlation service platform
+ participant Third_party_service_providers as Third party service providers
+
+ Third_party_service_providers->>Open_IoT_ICS: 1. Request for mapping IoT device
+ Note over Open_IoT_ICS: 2. Stores UTI, service URI
+ Open_IoT_ICS->>IoT_service_provider: 3. Sends mapping information
+ IoT_service_provider->>IoT_device: 4. Sends mapping information
+ Note over IoT_device: 5. Stores UTI, service URI
+ IoT_device->>IoT_service_provider: 6. Acknowledge
+ IoT_service_provider->>Open_IoT_ICS: 7. Reply device ID
+ Note over Open_IoT_ICS: 8. Creates mapping table
+ Open_IoT_ICS->>IoT_service_provider: 9. Mapping response
+ Open_IoT_ICS->>Third_party_service_providers: 9. Mapping response
+
+```
+
+Y.4462(20)\_F03
+
+Sequence diagram showing the procedures of establishing an identity mapping between IoT device, IoT service provider, Open IoT identity correlation service platform, and Third party service providers.
+
+**Figure 3 – Procedures of establishing an identity mapping**
+
+Step 1: Third party service provider sends a mapping IoT device request to the open IoT ICS through the reference point ICS-1. The request includes information such as the service URI, UTI, and IoT device serial number.
+
+Step 2: Upon receiving the request, the open IoT ICS stores the service URI and UTI as an initial identity mapping table, the full table will be created in step 8.
+
+Step 3: Open IoT ICS sends the mapping information to the IoT service provider through the reference point ICS-2, including service URI, UTI and IoT device serial number.
+
+Step 4: The IoT service provider finds the IoT device that corresponds to IoT device serial number and then sends the mapping information to the IoT device, including service URI and UTI.
+
+Step 5: The IoT device stores the service URI and UTI in the internal storage.
+
+Step 6: The IoT device acknowledges the receipt of service URI and UTI to IoT service provider.
+
+Step 7: The IoT service provider sends the IoT device ID to the open IoT ICS.
+
+Step 8: Open IoT ICS creates an identity mapping table with device ID, service URI and UTI.
+
+Step 9: Open IoT ICS sends a response to both third party service provider and IoT service provider to indicate the result of identity mapping.
+
+### 10.2 Identity de-mapping
+
+Identity de-mapping function is to remove the relationship between multiple identities of IoT related entities.
+
+Identity de-mapping can be requested by the third party service provider or IoT service provider through reference point ICS-3 or ICS-4 if one of the following conditions is met:
+
+- IoT device is unregistered from IoT service provider;
+- the UTI is invalid;
+- third party service is invalid;
+- third party service no longer authorized by the user.
+
+If the IoT service provider or third party service provider needs to terminate the mapping between IoT device and third party service, the IoT service provider or third party service provider shall send a request to open IoT ICS to delete the identity mapping, then the open IoT ICS responds to the related entities that the identity mapping table has been successfully deleted.
+
+
+
+```
+
+sequenceDiagram
+ participant IoT as IoT service provider
+ participant Platform as Open IoT identity correlation service platform
+ participant Third as Third party service providers
+
+ IoT->>Platform: 1.1 De-mapping request
+ Third->>Platform: 1.2 De-mapping request
+ Note over Platform: 2. Delete the mapping
+ Platform-->>IoT: 3. De-mapping response
+ Platform-->>Third: 3. De-mapping response
+
+```
+
+Y.4462(20)\_F04
+
+Sequence diagram for identity de-mapping procedures. It shows three entities: IoT service provider, Open IoT identity correlation service platform, and Third party service providers. Step 1.1 shows a 'De-mapping request' from the IoT service provider to the platform. Step 1.2 shows a 'De-mapping request' from the Third party service providers to the platform. Step 2 is a process box 'Delete the mapping' on the platform. Step 3 shows 'De-mapping response' from the platform to both the IoT service provider and the Third party service providers.
+
+**Figure 4 – Procedures of identity de-mapping**
+
+Step 1 (1.1 and 1.2) represents the de-mapping workflow. There are 2 options:
+
+- Case 1 (shown as 1.1 in Figure 4) represents the de-mapping request initiated from the IoT service provider through the reference point ICS-4.
+- Case 2 (shown as 1.2 in Figure 4) represents the de-mapping request initiated from the third party service provider through the reference point ICS-3.
+
+Step 2 upon receiving the request, the open IoT ICS is responsible for processing the request locally, such as delete the mapping.
+
+Step 3 open IoT ICS returns a response to indicate the result of deletion of mapping to both IoT service provider and third party service provider.
+
+### 10.3 Identity relationship inquiry
+
+The identity relationship inquiry function, as shown in Figure 5, is used to query the relationship of identities of IoT related entities and check the existence of the identity mapping before the interaction between the IoT device and a third party service.
+
+There are two cases of inquiry, Case 1 is shown as Figure 5 and Case 2 is shown as Figure 6.
+
+Case 1: The IoT device requests for query mapping information by sending its own device ID. In this case, the IoT device has access to query the service URI and UTI corresponding to that device ID which is located in a specific row of the mapping table.
+
+
+
+```
+
+sequenceDiagram
+ participant Device as IoT device
+ participant Provider as IoT service provider
+ participant Platform as Open IoT identity correlation service platform
+
+ Device->>Provider: 1. Request for query mapping information
+ Provider->>Platform: 2. Forward the query request
+ Note over Platform: 3. Lookup for mapping information
+ Platform-->>Provider: 4. Query response
+ Provider-->>Device: 5. Query response
+
+```
+
+Y.4462(20)\_F05
+
+Sequence diagram for identity relationship inquiry (Case 1). It shows three entities: IoT device, IoT service provider, and Open IoT identity correlation service platform. Step 1 shows a 'Request for query mapping information' from the IoT device to the IoT service provider. Step 2 shows 'Forward the query request' from the IoT service provider to the platform. Step 3 is a process box 'Lookup for mapping information' on the platform. Step 4 shows a 'Query response' from the platform to the IoT service provider. Step 5 shows a 'Query response' from the IoT service provider to the IoT device.
+
+**Figure 5 – Procedures of identity relationship inquiry (Case 1)**
+
+Step 1 represents the IoT device's request to query identity mapping information with its own device ID.
+
+Step 2 the IoT service provider forwards the request to open IoT ICS through reference point ICS-6.
+
+Step 3 upon receiving the request, the open IoT ICS is responsible for looking-up the mapping table to retrieve the service URI and UTI correspond to that device ID.
+
+Step 4 if the mapping table exists, the open IoT ICS returns a response with the service URI and UTI which correspond to that device ID to the IoT service provider. Otherwise, returns an error message.
+
+Step 5 the IoT service provider forwards the response to the IoT device.
+
+Case 2: The third party service provider requests query mapping information by sending both service URI and UTI. In this case, only when the combination of service URI and UTI exist in the same row of the mapping table, will the open IoT ICS respond to the query with the device ID. Otherwise, the open IoT ICS will respond with an error message.
+
+
+
+```
+sequenceDiagram
+ participant OI as Open IoT identity correlation service platform
+ participant TP as Third party service providers
+ TP->>OI: 1. Request for query mapping information
+ OI->>OI: 2. Lookup for mapping information
+ OI->>TP: 3. Query response
+```
+
+Y.4462(20)\_F06
+
+Sequence diagram showing the procedures of identity relationship inquiry (Case 2) between an Open IoT identity correlation service platform and Third party service providers.
+
+**Figure 6 – Procedures of identity relationship inquiry (Case 2)**
+
+Step 1 represents one third party service provider request to query identity mapping information with both service URI and UTI.
+
+Step 2 upon receiving the request, the open IoT ICS is responsible for looking-up the mapping table using service URI and UTI. Only if both of the service URI and UTI are located in one single row in the mapping table, the open IoT ICS shall then retrieve the device ID corresponding to the combination of service URI and UTI.
+
+Step 3 if the given row from the mapping table exists, the open IoT ICS returns a response with the device ID to the third party service provider. Otherwise, the open IoT ICS will respond with an error message.
+
+### **10.4 Service provider authentication and access control**
+
+To set up a secure connection with IoT service provider(s) and third party service provider(s), the open IoT ICS should provide authorization and access control functions. The certificates of [b-ITU-T X.509] and public key infrastructure (PKI) is recommended for the open IoT ICS to provide these authorization and access control functions. The authorization and access control flow are shown in Figure 7 and described below:
+
+
+
+```
+
+sequenceDiagram
+ participant IoT as IoT service provider
+ participant OpenIoT as Open IoT identity correlation service platform
+
+ IoT->>OpenIoT: 1. Provide credential
+ activate OpenIoT
+ OpenIoT->>OpenIoT: 2. Verify credential
+ deactivate OpenIoT
+ OpenIoT->>IoT: 3. Issue a certificate
+ activate IoT
+ IoT->>OpenIoT: 4. Use a certificate for certification
+ deactivate IoT
+ activate OpenIoT
+ OpenIoT->>OpenIoT: 5. Verify certificate
+ deactivate OpenIoT
+ OpenIoT->>IoT: 6. Response with the result
+ deactivate OpenIoT
+
+```
+
+Y.4462(20)\_F07
+
+Sequence diagram showing the procedure of authorization and access control flow between an IoT service provider and an Open IoT identity correlation service platform.
+
+**Figure 7 – Procedure of authorization and access control flow**
+
+Step 1 represents the IoT service provider's provision of credentials to open IoT ICS through reference point ICS-5.
+
+Step 2 represents open IoT ICS verifying the validity of the credentials.
+
+Step 3 represents the open IoT ICS issuing of certificates to the IoT service providers.
+
+Steps 4 to 6 represents the process of certification of IoT service providers.
+
+## 11 Security considerations
+
+### 11.1 Discovery mechanisms in identity information exchange
+
+As mentioned in clause 10.3 which describes the identity relationship inquiry, for security considerations, only the IoT device already existing in the mapping list has permission to initiate a query operation. Based on that requirement, the whole system needs a mechanism to publish identity information, obtain the mapping list and acquire the needed information. The framework for discovering cybersecurity information and the mechanism presented in [ITU-T X.1570] is recommended.
+
+The stages of discovery in the framework of identifying and locating the source of cybersecurity information is shown in Figure 8.
+
+
+
+```
+
+sequenceDiagram
+ participant Retriever
+ participant Directory
+ participant Source
+
+ Source->>Directory: } Information publishing stage
+ activate Directory
+ deactivate Directory
+
+ Retriever->>Directory: } Candidate list reception stage
+ activate Directory
+ Directory->>Retriever: }
+ deactivate Directory
+
+ Retriever->>Source: } Information acquisition stage
+ activate Source
+ Source->>Retriever: }
+ deactivate Source
+
+```
+
+Y.4462(20)\_F08
+
+Sequence diagram showing the stages of discovery in the framework of identifying and locating the source of cybersecurity information between a Retriever, Directory, and Source.
+
+**Figure 8 – Stages of discovery in the framework of identifying and locating the source of cybersecurity information**
+
+A unique identifier is needed to identify identity information. Any globally unique identifier used for global cybersecurity information exchange shall have the following characteristics:
+
+- Simplicity, usability, flexibility, extensibility, scalability, and deployability.
+- Distributed management of diverse identifier schemes.
+- Long-term reliability of identifier registrars, and the availability of high-performance tools for discovering information associated with any given identifier.
+
+According to the description from clause 8.8 (Security and privacy protection requirements) in [ITU-T Y.4100], in order to meet these requirements, the following characteristics of device identity are recommended:
+
+- Tamper-resistant, anti-counterfeiting, unpredictable, unique.
+- Including vendor and product model information.
+
+Other identity schemes which comply with these requirements could be implemented with arbitrary mechanisms.
+
+### **11.2 Communication security**
+
+For security consideration, the services provided by open IoT ICS such as identity mapping, de-mapping, and access control need communication security capabilities. The implementation of transport layer security (TLS) Version 1.3, as specified in [IETF RFC 8446], for securing communication between open IoT ICS and an IoT service provider/third party service provider is recommended.
+
+TLS provides a secure communication path between two entities. It allows open IoT ICS to communicate in a way that is designed to prevent eavesdropping, tampering, or message forgery and mutual authentication on both parties.
+
+These capabilities fulfil the IoT common requirements on security and privacy protection specified in [ITU-T Y.4100].
+
+## Appendix I
+
+### Use cases
+
+(This appendix does not form an integral part of this Recommendation.)
+
+This appendix provides some use cases to illustrate the concept of the open IoT identity correlation service.
+
+### I.1 Use case 1: Smart refrigerator
+
+A smart refrigerator can monitor the food left in it. When it finds that there is not enough food, for example, not enough milk in the refrigerator, it can notify the user's e-commerce mobile application, to remind the user to buy milk from the user's e-commerce mobile application.
+
+When the refrigerator vendor's device management platform detects that the light bulb of the refrigerator is broken, the refrigerator vendor's device management platform can send a notification message to the e-commerce server to remind the user to buy a new light bulb.
+
+Figure I.1 shows a refrigerator sending notification to a third party e-commerce service provider.
+
+
+
+```
+graph TD; SR[Smart refrigerator] -- Notification --> RMDMP[Refrigerator vendor's device management platform]; RMDMP -- Notification --> OIICS[Open IoT identity correlation service]; OIICS -- Notification --> ECP[E-commerce service provider]; ECP <--> EMA[E-commerce mobile application];
+```
+
+The diagram illustrates the notification flow for a smart refrigerator. At the bottom left is a 'Smart refrigerator' icon. An arrow labeled 'Notification' points from the refrigerator to a server rack icon labeled 'Refrigerator vendor's device management platform'. From there, another arrow labeled 'Notification' points to a cloud icon labeled 'Open IoT identity correlation service'. A third arrow labeled 'Notification' points from this cloud to another cloud icon labeled 'E-commerce service provider'. Finally, a double-headed arrow connects the 'E-commerce service provider' cloud to a smartphone icon labeled 'E-commerce mobile application'. Below the smartphone icon is the reference 'Y.4462(20)\_F1.1'.
+
+Diagram illustrating the notification flow from a Smart refrigerator to an E-commerce mobile application via the Open IoT identity correlation service and the Refrigerator vendor's device management platform.
+
+**Figure I.1 – Smart refrigerator sending notification to a third party e-commerce service provider**
+
+In this use case, there is a need to provide the mapping between the refrigerator's identifier and user's e-commerce UTI and to open this capability to other entity.
+
+### I.2 Use case 2: Smart lock
+
+In the case of a smart house, one smart lock can interact with other smart things such as lights and an air-conditioning system. Once the smart lock is unlocked, it can trigger the switch of the smart light and can set the temperature on the air-conditioning system.
+
+In the scenario where there is a third party smart home service provider which had connected to multiple smart things such as light bulbs or an air-conditioning system. Once a new smart lock is installed, the user of a third party service provider can bind this lock to the smart home service provider via open IoT ICS and establish the connection with other smart things in the house.
+
+Figure I.2 shows the mapping of a new lock to a third party smart home service.
+
+
+
+```
+
+graph TD
+ User((Third-party smart home service provider (User)))
+ Correlation((Open IoT identity correlation service))
+ LockProvider[Lock service provider]
+ SmartLock[Smart lock (Device ID)]
+ AC[AC]
+ LightBulb[Light bulb]
+
+ User -- "Request to bind lock" --> Correlation
+ Correlation -- "Bind the lock" --> LockProvider
+ LockProvider -- "Bind the lock" --> SmartLock
+ User -.-> AC
+ User -.-> LightBulb
+
+```
+
+Y.4462(20)\_F1.2
+
+Figure I.2: Mapping a new lock to a third party smart home service. The diagram shows a flow from a Third-party smart home service provider (User) to an Open IoT identity correlation service, then to a Lock service provider, and finally to a Smart lock (Device ID). Dashed lines also connect the Third-party smart home service provider to an AC and a Light bulb.
+
+**Figure I.2 – Mapping a new lock to a third party smart home service**
+
+### I.3 Use case 3: Device based service charge sharing
+
+In this use case, one smart loudspeaker can use third party music services. Based on the business agreement, the smart loudspeaker box's software vendor may charge the music provider according to how much music is consumed by the smart loudspeaker. The rationale for this business model is that the software vendor provides the integration capability with the third party music service and hence will increase the consumption of the third party's music service. The revenue is shared with the hardware vendor of the smart loudspeaker.
+
+In this use case, the identity service platform is used to map/bind the smart loudspeaker's device identifier and the URI from the music service provider.
+
+Figure I.3 shows mapping of a smart speaker device ID with a third party music service URI.
+
+
+
+```
+
+graph TD
+ MusicA((Music provider A))
+ MusicB((Music provider B))
+ Correlation((Open IoT identity correlation service))
+ SpeakerSoftware[Speaker software vendor]
+ SpeakerHardware[Speaker hardware vendor]
+
+ SpeakerHardware -- "Speaker ID" --> SpeakerSoftware
+ SpeakerSoftware -- "Create mapping relationship table" --> Correlation
+ Correlation -- "Bind music user ID with speaker ID" --> MusicA
+ Correlation -- "Bind music user ID with speaker ID" --> MusicB
+ Correlation -.-> SpeakerSoftware
+
+```
+
+Y.4462(20)\_F1.3
+
+Figure I.3: Mapping a smart speaker device ID with a third party music service URI. The diagram shows a flow from a Speaker hardware vendor to a Speaker software vendor, then to an Open IoT identity correlation service, which in turn connects to Music provider A and Music provider B. Dashed lines also connect the Open IoT identity correlation service to the Speaker software vendor.
+
+**Figure I.3 – Mapping a smart speaker device ID with a third party music service URI**
+
+### I.4 Use case 4: Promoting data package sharing between different services
+
+This use case uses a simple example to illustrate how the open IoT ICS promotes the users sharing data communication packages among a family's IoT devices. As shown in Figure I.4, a family (user) has three IoT devices (a watch, a bulb and a car), and the family subscribes to a data communication package which binds those three IoT devices. In this data communication package, data communication traffic is free if those three IoT devices access indicated services respectively (such as the watch for the message service, the bulb for the monitoring service and the car for the navigation service).
+
+Each month, the network operator should combine the bills for data communication traffic for the family's IoT devices with that from the three services. Each of the family's IoT devices has a special identity in the service (named service-id), and in the communication network it also has another identity (named network-id, for example an E.164/E.212 number or a special IP address). The family (user) has a user identity (named user-id) in the network's business service system (BSS). Typically, the BSS should coordinate with each of the services one by one to exchange identity-related information, which leads to high costs and has a lack of scalability and operational capabilities.
+
+The open IoT ICS provides a uniform open identity mapping service (see Figure I.4) for the BSS and those services. Those services and the BSS can forward dynamically (or periodically) their identity-related information to the identity correlation service, and they can also get dynamically (or periodically) relevant information from the identity correlation service. Through the open IoT ICS, the BSS does not coordinate with each of those services one by one to exchange identity-related information, which can cut the costs and improve the scalability and operational capabilities.
+
+
+
+The diagram illustrates the architecture for promoting data package sharing between different services. It is organized into three main layers: Service providers, Network operators, and Users.
+
+- Service providers:** Includes Message service, Monitoring service, and Navigation service, each represented by a server icon.
+- Network operators:** Includes Communication networks (represented by a cloud) and BSS (Business Service System, represented by a server icon).
+- Users:** Includes Watch, Bulb, and Car, each represented by an icon.
+
+Key interactions and components shown:
+
+- Data consumption traffic:** Dashed lines show traffic from the Watch to the Message service, from the Bulb to the Monitoring service, and from the Car to the Navigation service.
+- Mapping/binding identities:** Dashed lines show the BSS interacting with the three service providers for mapping/binding identities.
+- Identity correlation service:** A vertical server icon on the right that receives mapping/binding information from the three service providers and provides it back to the BSS.
+
+Y.4462(20)\_F1.4
+
+Diagram illustrating the architecture for promoting data package sharing between different services. The diagram shows three layers: Service providers, Network operators, and Users. Service providers include Message service, Monitoring service, and Navigation service. Network operators include Communication networks and BSS. Users include Watch, Bulb, and Car. The diagram shows data consumption traffic from users to services, and mapping/binding identities between services and the BSS, and between services and the Identity correlation service.
+
+Figure I.4 – Promoting data package sharing between different services
+
+## Bibliography
+
+- [b-ITU-T X.509] Recommendation ITU-T X.509 (2019), *Information technology – Open Systems Interconnection – The Directory: Public-key and attribute certificate frameworks*.
+- [b-ITU-T X.1252] Recommendation ITU-T X.1252 (2010), *Baseline identity management terms and definitions*.
+- [b-ITU-T X.1311] Recommendation ITU-T X.1311 (2011), *Information technology – Security framework for ubiquitous sensor networks*.
+- [b-ITU-T Y.2091] Recommendation ITU-T Y.2091 (2011), *Terms and definitions for next generation networks*.
+- [b-ITU-T Y.4050] Recommendation ITU-T Y.4050/Y.2069 (2012), *Terms and definitions for the Internet of Things*.
+- [b-ITU-T Y.4101] Recommendation ITU-T Y.4101/Y.2067 (2017), *Common requirements and capabilities of the gateway for Internet of things applications*.
+- [b-ITU-T Y.4400] Recommendation ITU-T Y.4400/Y.2063 (2012), *Framework of the web of things*.
+- [b-ITU-T Y.4401] Recommendation ITU-T Y.4401/Y.2068 (2015), *Functional framework and capabilities of the Internet of things*.
+- [b-ITU-T Y.4800] Recommendation ITU-T Y.4800/F.747.5 (2014), *Requirements and functional architecture of an automatic location identification system for ubiquitous sensor network applications and services*.
+- [b-ITU-T Y.4801] Recommendation ITU-T Y.4801/F.748.1 (2014), *Requirements and common characteristics of the IoT identifier for the IoT service*.
+- [b-ITU-T Y.4802] Recommendation ITU-T Y.4802/H.642.2 (2012), *Multimedia information access triggered by tag-based identification – Registration procedures for identifiers*.
+- [b-ITU-T Y.4803] Recommendation ITU-T Y.4803/H.642.3 (2012), *Information technology – Automatic identification and data capture technique – Identifier resolution protocol for multimedia information access triggered by tag-based identification*.
+- [b-ITU-T Y.4804] Recommendation ITU-T Y.4804/H.642.1 (2012), *Multimedia information access triggered by tag-based identification – Identification scheme*.
+- [b-FG-DPM TS D2.3] ITU-T Technical Report D2.3, *Web based data model for IoT and smart city*.
+- [b-ISO/IEC 24760-1] ISO/IEC 24760-1:2011, *Information technology – Security techniques – A framework for identity management – Part 1: Terminology and concepts*.
+
+
+
+## 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 |
+| 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 | 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 |
\ No newline at end of file
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@@ -0,0 +1,1047 @@
+
+
+I n t e r n a t i o n a l T e l e c o m m u n i c a t i o n U n i o n
+
+# ITU-T
+
+TELECOMMUNICATION
+STANDARDIZATION SECTOR
+OF ITU
+
+# Y.4470
+
+(08/2020)
+
+SERIES Y: GLOBAL INFORMATION
+INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS,
+NEXT-GENERATION NETWORKS, INTERNET OF
+THINGS AND SMART CITIES
+
+Internet of things and smart cities and communities –
+Frameworks, architectures and protocols
+
+# --- **Reference architecture of artificial intelligence service exposure for smart sustainable cities**
+
+Recommendation ITU-T Y.4470
+
+ITU-T
+
+## ITU-T Y-SERIES RECOMMENDATIONS
+
+## GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS, NEXT-GENERATION NETWORKS, INTERNET OF THINGS AND SMART CITIES
+
+## GLOBAL INFORMATION INFRASTRUCTURE
+
+| | |
+|-------------------------------------------|-------------|
+| General | Y.100–Y.199 |
+| Services, applications and middleware | Y.200–Y.299 |
+| Network aspects | Y.300–Y.399 |
+| Interfaces and protocols | Y.400–Y.499 |
+| Numbering, addressing and naming | Y.500–Y.599 |
+| Operation, administration and maintenance | Y.600–Y.699 |
+| Security | Y.700–Y.799 |
+| Performances | Y.800–Y.899 |
+
+## INTERNET PROTOCOL ASPECTS
+
+| | |
+|--------------------------------------------------------------------|---------------|
+| General | Y.1000–Y.1099 |
+| Services and applications | Y.1100–Y.1199 |
+| Architecture, access, network capabilities and resource management | Y.1200–Y.1299 |
+| Transport | Y.1300–Y.1399 |
+| Interworking | Y.1400–Y.1499 |
+| Quality of service and network performance | Y.1500–Y.1599 |
+| Signalling | Y.1600–Y.1699 |
+| Operation, administration and maintenance | Y.1700–Y.1799 |
+| Charging | Y.1800–Y.1899 |
+| IPTV over NGN | Y.1900–Y.1999 |
+
+## NEXT GENERATION NETWORKS
+
+| | |
+|-------------------------------------------------------------------|---------------|
+| Frameworks and functional architecture models | Y.2000–Y.2099 |
+| Quality of Service and performance | Y.2100–Y.2199 |
+| Service aspects: Service capabilities and service architecture | Y.2200–Y.2249 |
+| Service aspects: Interoperability of services and networks in NGN | Y.2250–Y.2299 |
+| Enhancements to NGN | Y.2300–Y.2399 |
+| Network management | Y.2400–Y.2499 |
+| Network control architectures and protocols | Y.2500–Y.2599 |
+| Packet-based Networks | Y.2600–Y.2699 |
+| Security | Y.2700–Y.2799 |
+| Generalized mobility | Y.2800–Y.2899 |
+| Carrier grade open environment | Y.2900–Y.2999 |
+
+## FUTURE NETWORKS
+
+### CLOUD COMPUTING
+
+### BIG DATA
+
+### QUANTUM KEY DISTRIBUTION NETWORKS
+
+### INTERNET OF THINGS AND SMART CITIES AND COMMUNITIES
+
+| | |
+|---------------------------------------------------------|----------------------|
+| General | Y.4000–Y.4049 |
+| Definitions and terminologies | Y.4050–Y.4099 |
+| Requirements and use cases | Y.4100–Y.4249 |
+| Infrastructure, connectivity and networks | Y.4250–Y.4399 |
+| Frameworks, architectures and protocols | Y.4400–Y.4549 |
+| Services, applications, computation and data processing | Y.4550–Y.4699 |
+| Management, control and performance | Y.4700–Y.4799 |
+| Identification and security | Y.4800–Y.4899 |
+| Evaluation and assessment | Y.4900–Y.4999 |
+
+For further details, please refer to the list of ITU-T Recommendations.
+
+# Recommendation ITU-T Y.4470
+
+# Reference architecture of artificial intelligence service exposure for smart sustainable cities
+
+## Summary
+
+Recommendation ITU-T Y.4470 establishes artificial intelligence service exposure (AISE) for smart sustainable cities (SSCs), and provides the common characteristics and high-level requirements, reference architecture and relevant common capabilities of AISE.
+
+AISE is one of the basic supporting functional entities for SSCs, with which SSC services can use uniform reference points (exposed by AISE) to integrate and access the artificial intelligence (AI) capabilities of AI services (e.g., machine learning services for image recognition, natural language processing services and traffic prediction services). In addition, AISE can collect and open SSC data, and it supports AI services to train and supply AI capabilities in AISE in SSCs.
+
+## History
+
+| Edition | Recommendation | Approval | Study Group | Unique ID* |
+|---------|----------------|------------|-------------|---------------------------------------------------------------------------|
+| 1.0 | ITU-T Y.4470 | 2020-08-29 | 20 | 11.1002/1000/14373 |
+
+## Keywords
+
+Artificial intelligence service; exposure; smart sustainable city.
+
+---
+
+\* To access the Recommendation, type the URL in the address field of your web browser, followed by the Recommendation's unique ID. For example, .
+
+## 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 .
+
+© ITU 2020
+
+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..... | 2 |
+| 4 | Abbreviations and acronyms ..... | 2 |
+| 5 | Conventions..... | 3 |
+| 6 | Introduction of AISE ..... | 3 |
+| 7 | Common characteristics and high-level requirements of AISE ..... | 4 |
+| | 7.1 Common characteristics ..... | 4 |
+| | 7.2 High-level requirements ..... | 5 |
+| 8 | Reference architecture of AISE..... | 6 |
+| | 8.1 Resource management-functional component ..... | 8 |
+| | 8.2 Task management-functional component..... | 8 |
+| | 8.3 AI model management-functional component ..... | 8 |
+| | 8.4 Policy management-functional component ..... | 8 |
+| | 8.5 AI capability management-functional component ..... | 9 |
+| | 8.6 AI capability performer-functional component..... | 9 |
+| | 8.7 AI model-functional component..... | 9 |
+| | 8.8 AI model agent-functional component..... | 9 |
+| | 8.9 Reference points ..... | 10 |
+| 9 | Common capabilities of AISE..... | 10 |
+| | 9.1 Training of AI models ..... | 10 |
+| | 9.2 Publication of AI capabilities ..... | 10 |
+| | 9.3 Subscription to AI capabilities ..... | 11 |
+| | 9.4 Access to AI capabilities ..... | 11 |
+| 10 | Security consideration ..... | 11 |
+| | Appendix I – Working modes of AISE to provide AI services to SSC services ..... | 12 |
+| | I.1 Tightly coupled working mode ..... | 12 |
+| | I.2 Loosely coupled working mode ..... | 13 |
+| | I.3 Hybrid working mode..... | 14 |
+| | Appendix II – Use cases of AISE for SSCs..... | 15 |
+| | II.1 Use case: promoting smart traffic controlling services ..... | 15 |
+| | II.2 Use case: promoting smart appliance voice control services ..... | 16 |
+| | II.3 Use case: promoting smart urban geographical information services..... | 17 |
+| | Appendix III – Common procedures of AISE for SSCs..... | 19 |
+| | III.1 Publication of the AI capabilities to be exposed ..... | 19 |
+| | III.2 Subscription to exposed AI capabilities ..... | 20 |
+| | III.3 Accessing the subscribed AI capabilities in AISE ..... | 21 |
+| | III.4 Accessing the subscribed AI capabilities outside of AISE ..... | 22 |
+| | Bibliography..... | 24 |
+
+
+
+# Recommendation ITU-T Y.4470
+
+# Reference architecture of artificial intelligence service exposure for smart sustainable cities
+
+# 1 Scope
+
+This Recommendation establishes the concept of artificial intelligence service exposure (AISE) for smart sustainable cities (SSCs).
+
+The scope of this Recommendation includes for AISE:
+
+- the concept, analysis of common characteristics and high-level requirements;
+- reference architecture and relevant common capabilities.
+
+In addition, working modes for AISE to supply AI capabilities to SSC services are provided. Use cases are given in appendices.
+
+# 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 Y.4000] Recommendation ITU-T Y.4000/Y.2060 (2012), *Overview of the Internet of things*.
+
+# 3 Definitions
+
+## 3.1 Terms defined elsewhere
+
+This Recommendation uses the following terms defined elsewhere:
+
+**3.1.1 application** [b-ITU-T Y.2091]: A structured set of capabilities, which provide value-added functionality supported by one or more services, which may be supported by an API interface.
+
+**3.1.2 artificial intelligence (AI)** [b-ETSI GR ENI 004]: Computerized system that uses cognition to understand information and solve problems.
+
+NOTE 1 – [b-ISO/IEC 2382] defines AI as "interdisciplinary field, usually regarded as a branch of computer science, dealing with models and systems for the performance of functions generally associated with human intelligence, such as reasoning and learning".
+
+NOTE 2 – In computer science AI research is defined as the study of "intelligent agents": any device that perceives its environment and takes actions to achieve its goals.
+
+NOTE 3 – This includes pattern recognition and the application of machine learning and related techniques.
+
+NOTE 4 – Artificial intelligence is the whole idea and concepts of machines being able to carry out tasks in a way that mimics the human intelligence and would be considered "smart".
+
+**3.1.3 capability** [b-ITU-R M.1224-1]: The ability of an item to meet a service demand of given quantitative characteristics under given internal conditions.
+
+**3.1.4 device** [ITU-T Y.4000]: With regard to the Internet of things, this is a piece of equipment with the mandatory capabilities of communication and the optional capabilities of sensing, actuation, date capture, data storage and data processing.
+
+**3.1.5 Internet of things (IoT)** [ITU-T Y.4000]: A global infrastructure for the information society, enabling advanced services by interconnecting (physical and virtual) things based on existing and evolving interoperable information and communication technologies.
+
+NOTE 1 – Through the exploitation of identification, data capture, processing and communication capabilities, the IoT makes full use of things to offer services to all kinds of applications, whilst ensuring that security and privacy requirements are fulfilled.
+
+NOTE 2 – From a broad perspective, the IoT can be perceived as a vision with technological and societal implications.
+
+**3.1.6 machine learning (ML)** [b-ITU-T Y.3172]: Processes that enable computational systems to understand data and gain knowledge from it without necessarily being explicitly programmed.
+
+NOTE – This definition is adapted from [b-ETSI GR ENI 004].
+
+**3.1.7 service** [b-ITU-T Y.2091]: A set of functions and facilities offered to a user by a provider.
+
+**3.1.8 smart sustainable city** [b-ITU-T Y.4900]: A smart sustainable city is an innovative city that uses information and communication technologies (ICTs) and other means to improve quality of life, efficiency of urban operation and services and competitiveness, while ensuring that it meets the needs of present and future generations with respect to economic, social, environmental, as well as cultural aspects.
+
+NOTE – City competitiveness refers to policies, institutions, strategies and processes that determine the city's sustainable productivity.
+
+**3.1.9 thing** [ITU-T Y.4000]: With regard to the Internet of things, this is an object of the physical world (physical things) or of the information world (virtual things), which is capable of being identified and integrated into the communication networks.
+
+## **3.2 Terms defined in this Recommendation**
+
+None.
+
+# **4 Abbreviations and acronyms**
+
+This Recommendation uses the following abbreviations and acronyms:
+
+| | |
+|--------|-----------------------------------------------|
+| 3D | Three Dimensional |
+| ACM-FC | AI Capability Management-Functional Component |
+| ACP-FC | AI Capability Performer-Functional Component |
+| AI | Artificial Intelligence |
+| AISE | Artificial Intelligence Service Exposure |
+| AM-FC | AI Model-Functional Component |
+| AMA-FC | AI Model Agent-Functional Component |
+| AMM-FC | AI Model Management-Functional Component |
+| API | Application Programming Interface |
+| DM-FC | Data Management-Functional Component |
+| FC | Functional Component |
+| IoT | Internet of Things |
+
+| | |
+|--------|------------------------------------------------|
+| IP | Internet Protocol |
+| ML | Machine Learning |
+| MTM-FC | Model-Training Management-Functional Component |
+| PM-FC | Policy Management-Functional Component |
+| RM-FC | Resource Management-Functional Component |
+| SAVC | Smart Appliance Voice Control |
+| STC | Smart Traffic Controlling |
+| SSC | Smart Sustainable City |
+| TM-FC | Task Management-Functional Component |
+| UGI | Urban Geographic Information |
+
+# 5 Conventions
+
+The following conventions are used in this Recommendation:
+
+- The keywords "is required to" indicate a requirement which must be strictly followed and from which no deviation is permitted, if conformance to this Recommendation is to be claimed.
+- The keywords "is recommended" indicate a requirement which is recommended but which is not absolutely required. Thus, this requirement need not be present to claim conformance.
+
+# 6 Introduction of AISE
+
+AISE is a functional entity (see Figure 6-1) in an SSC that facilitates SSC services (e.g., $S_1$ to $S_n$ ) to integrate and access the capabilities of AI services (e.g., $AI_1$ to $AI_m$ ) provided by AI service providers (e.g., $A_1$ to $A_k$ ). AI service(s) can be deployed in AISE and part or whole of their AI capabilities can be exposed to SSC services. AISE provides uniform reference points to support SSC services to subscribe and access the AI capabilities exposed in AISE. SSC services can subscribe and access one or multiple AI capabilities that can be provided by different AI services.
+
+AISE can collect SSC data from SSC services, and can support AI service providers to design and train AI services in the SSC using the collected SSC data. AISE provides a security and privacy protection mechanism for collected SSC data.
+
+NOTE – The SSC data can be opened and shared with AI services and can be accessed only in the SSC. Specification of mechanisms for SSC data openness lies outside the scope of this Recommendation.
+
+AISE also supplies AI services to SSC services (e.g., for inference or prediction).
+
+
+
+Y.4470(20)\_F6-1
+
+Figure 6-1: Overview of AISE architecture. The diagram shows a multi-layered system. At the top, 'AI service providers' (AI service A1, AI service A2, ..., AI service Ak) are located in 'Clouds'. These providers send data to a central 'AISE provider' (containing AI1, ..., AI\_m) via 'Deployment' arrows. The AISE provider acts as a 'Reference points (For AI and data)' between 'SSC service providers' (SSC service S1, ..., SSC service Sn) and 'SSC service consumers' (IoT devices). The SSC service providers are located in 'Smart sustainable cities (SSCs)'. The SSC service consumers are represented by icons of people and devices (laptop, smartphone, etc.).
+
+**Figure 6-1 – Overview of AISE**
+
+AISE can provide benefits to AI service providers and SSC service providers. From the perspective of AI service providers, they can design and train AI capabilities with SSC data in AISE and provide AI capabilities to SSC services through AISE. From the perspective of SSC service providers, they can integrate and access AI capabilities exposed by AI services through AISE.
+
+# **7 Common characteristics and high-level requirements of AISE**
+
+## **7.1 Common characteristics**
+
+This clause provides the general characteristics of AISE.
+
+### **7.1.1 Integrating multiple AI models**
+
+AISE supports the integration of multiple AI models that have been provided by the same or different AI services.
+
+In the tightly coupled working mode (see clause I.1), integrated AI models work within AISE. Conversely, in the loosely coupled working mode (see clause I.2), integrated AI models work outside AISE, and there are corresponding AI model agents in AISE to interact with the integrated AI models.
+
+### **7.1.2 Supporting AI model training**
+
+AISE collects and manages SSC data, and opens it to authorized AI services for training their AI models. The opened SSC data in AISE can be accessed by SSC services.
+
+In the tightly coupled working mode (see clause I.1), opened SSC data is accessed in AISE, and the training for AI models is also performed in AISE. In this mode, AISE provides underlying infrastructures for data openness and model training.
+
+In the loosely coupled working mode (see clause I.2), opened SSC data is accessed through uniform reference points by authorized AI services, which train AI models. In this mode, AISE does not provide underlying infrastructures for model training.
+
+### **7.1.3 Exposing AI capabilities**
+
+AISE exposes uniform reference points for AI services, which can access opened SSC data, and can deploy trained AI models in AISE or train AI models in AISE.
+
+AISE publishes the AI capabilities exposed by the AI services.
+
+In addition, AISE exposes uniform reference points for SSC services, which can discover, subscribe and access AI capabilities as exposed by the same or different AI services, even if the AI capabilities use different AI technologies.
+
+### **7.1.4 Performing AI capabilities**
+
+AISE provides underlying infrastructures to supply AI capabilities to AI models. In the tightly coupled working mode (see clause I.1), the AI capabilities of AI models can be performed within AISE. Furthermore, in the loosely coupled working mode (see clause I.2), the AI model agents in AISE interact with the external AI models and their AI capabilities are performed outside AISE.
+
+## **7.2 High-level requirements**
+
+This clause provides the high-level requirements of AISE.
+
+### **7.2.1 Requirements for model training of AI capabilities**
+
+The requirements and recommendations for model training of AI capabilities are as follows:
+
+- AISE is required to support authorized AI services to subscribe to and access opened SSC data for training the AI model;
+- AISE is recommended to support authorized AI services to train the AI model in AISE.
+
+### **7.2.2 Requirements for publication of exposed AI capabilities**
+
+The requirements and recommendations for publication of exposed AI capabilities are as follows:
+
+- AISE is required to support authorized AI services to publish their AI capabilities;
+- AISE is required to support authorized AI services to manage (e.g., add, update, delete and search) their published AI capabilities;
+- AISE is recommended to allow authorized AI services to define access policies (such as when AI capabilities can be available) for SSC services to access exposed AI capabilities;
+- AISE is recommended to support authorized AI services to monitor the subscription status of their AI capabilities.
+
+### **7.2.3 Requirements for subscription to exposed AI capabilities**
+
+The requirements and recommendations for subscription to exposed AI capabilities are as follows:
+
+- AISE is required to support SSC services to discover and subscribe to exposed AI capabilities;
+- AISE is required to support SSC services to subscribe multiple exposed AI capabilities provided by the same or different AI service(s);
+- AISE is recommended to notify SSC services of the status of their subscribed AI capabilities, if needed, such as whether the relevant AI capabilities are available;
+
+- AISE is recommended to notify authorized AI services of the subscription information of their exposed AI capabilities, if needed, such as who subscribed to and unsubscribed from relevant AI capabilities.
+
+### **7.2.4 Requirements for accessing exposed AI capabilities**
+
+The requirements and recommendations for accessing exposed AI capabilities are as follows:
+
+- AISE is required to support authorized SSC services to access one or more subscribed AI capabilities provided by the same or different AI services;
+- AISE is recommended to establish access policies for exposed AI capabilities based on configuration parameters (e.g., time of day, day of the week, location).
+
+### **7.2.5 Security requirement**
+
+The following are the security requirements for AISE;
+
+- AISE is required to authorize and authenticate AI services to access the opened SSC data in AISE;
+- AISE is required to authorize and authenticate AI services to train, deploy and expose AI capabilities in AISE;
+- AISE is required to authorize and authenticate SSC services to access exposed SSC capabilities as published by AISE.
+
+#### **7.2.6 Other requirement**
+
+In addition to the items listed in clauses 7.2.1 to 7.2.5:
+
+- AISE is required to support statistics functions.
+
+# **8 Reference architecture of AISE**
+
+AISE works on the service support and application support layer of the Internet of things (IoT) reference model specified in [ITU-T Y.4000], and it utilizes the capabilities provided by the underlying smart city infrastructures (such as networks, clouds, big data and security). Figure 8-1 is a schematic diagram of the reference architecture of AISE.
+
+
+
+Y.4470(20)\_F8-1
+
+Figure 8-1 – Reference architecture diagram of AISE. The diagram shows a central AISE block with internal components: Data management, Model training management, AI model management, AI capability management, AI models, Policy management, AI model agents, AI capability performer, Resource management, and Task management. AISE is connected to AI services (left) and SSC services (right) via reference points AISE-1 to AISE-6. AI services include External model training and External AI models. SSC services include SSC services. All components are supported by Smart city infrastructures (Networks, clouds, big data, security, etc.) at the bottom. A reference point AISE-5 connects AI services to AISE, and AISE-6 connects AISE to SSC services. AISE-3 connects AI services to AISE, and AISE-4 connects AISE to AI services. AISE-1 connects AISE to SSC services, and AISE-2 connects SSC services to AISE.
+
+**Figure 8-1 – Reference architecture diagram of AISE**
+
+AISE includes three groups of logical functional components (FCs) intended for: AI model-training and data management, supplying AI capabilities, and resource and task management.
+
+- The FCs in the first group include resource management (RM-FC) and task management (TM-FC).
+- The FCs in the second group include AI model management (AMM-FC), policy management (PM-FC), AI capability management (ACM-FC), AI capability performer (ACP-FC), and multiple AI models (AM-FC) and AI model agents (AMA-FC).
+- The FCs in the third group include model-training management (MTM-FC) and data management (DM-FC).
+
+AISE exposes a group of reference points to interact with AI services and SSC services, including:
+
+- AISE-1: for SSC services to discover and subscribe to exposed AI capabilities in AISE;
+- AISE-2: for SSC services to access the subscribed AI capabilities exposed in AISE;
+- AISE-3: for AI services to deploy and expose AI capabilities in AISE;
+- AISE-4: for interaction between the AI model agents of AISE and the external AI models of the AI services;
+- AISE-5: for SSC data-related interaction between the AI services and AISE, with which the AI services access exposed SSC data through AISE to train their AI models;
+- AISE-6: for SSC data-related interaction between AISE and SSC services.
+
+AISE, AI services and SSC services work on the underlying smart city infrastructures (such as networks, clouds, big-data and security).
+
+NOTE 1 – The MTM-FC utilizes the underlying resources and SSC data in AISE to train AI models. The FCs for model-training management and data management lie outside the scope of this Recommendation.
+
+NOTE 2 – The DM-FC exposes two reference points, AISE-5 and AISE-6, to collect SSC data from SSC services and to open SSC data to other FCs or external AI services. The reference points AISE-5 and AISE-6 lie outside the scope of this Recommendation.
+
+## **8.1 Resource management-functional component**
+
+The RM-FC monitors and manages underlying resources to support training AI models, supplying AI capabilities and managing SSC data in AISE. The RM-FC virtualizes the underlying resources and exposes uniform internal interfaces to leverage other FCs of AISE to utilize them.
+
+The underlying resources may be hosted by multiple devices, which include at least:
+
+- computational resources, such as a central processing unit and a graphics processing unit;
+- storage resources;
+- network resources, such as Internet protocol (IP) addresses and ports, and network bandwidth;
+- micro-services, such as a timer service and messaging service.
+
+The RM-FC, coordinating with other FCs of AISE, provides the following functionalities:
+
+- monitoring and managing the underlying resources of one or multiple devices;
+- virtualizing the underlying resources;
+- exposing uniform internal interfaces to allow other FCs of AISE to utilize the virtualized underlying resources.
+
+## **8.2 Task management-functional component**
+
+The TM-FC orchestrates and manages tasks in AISE, such as training AI models, supplying AI capabilities and sharing SSC data. A task can be performed by one or multiple micro-service(s) of AISE.
+
+The TM-FC, coordinating with other FCs of AISE, provides the following functionalities:
+
+- task orchestration and creation ;
+- task monitoring and management.
+
+## **8.3 AI model management-functional component**
+
+The AMM-FC manages the AI models (see clause 8.7) and AI model agents (see clause 8.8) in AISE.
+
+The AMM-FC exposes reference point AISE-3 for external AI services to interact with AISE.
+
+The AMM-FC, coordinating with other FCs of AISE, provides the following functionalities:
+
+- managing the AI models (such as adding, deleting and updating the AI models);
+- managing the AI model agents (such as creating, deleting, updating the AI model agents and their relationships with corresponding external AI models).
+
+## **8.4 Policy management-functional component**
+
+The PM-FC provides access control for AI services to expose their AI capabilities and provides access control for SSC services to discover, subscribe to and access AI capabilities exposed by AI services. In addition, the PM-FC provides access control to expose and share SSC data with AI services.
+
+The PM-FC, coordinating with other FCs of AISE, manages access permissions for:
+
+- exposed AI capabilities;
+- the discovery, subscriptions and accessing of exposed AI capabilities;
+
+- exposure of SSC data;
+- the discovery, subscriptions to and accessing of exposed SSC data;
+- training AI models in AISE.
+
+## **8.5 AI capability management-functional component**
+
+The ACM-FC manages and publishes information about exposed AI capabilities, and exposes reference point AISE-1 to support SSC services to discover and subscribe to the AI capabilities exposed in AISE.
+
+The ACM-FC, coordinating with other FCs of AISE, through reference point AISE-1, manages information about:
+
+- the AI capabilities exposed by the AI models;
+- the AI capabilities exposed by the external AI models;
+- the subscriptions to AI capabilities from SSC services.
+
+## **8.6 AI capability performer-functional component**
+
+The ACP-FC exposes reference point AISE-2 to support SSC services to access subscribed AI capabilities.
+
+The ACP-FC, coordinating with other FCs of AISE, through reference point AISE-2, provides the followed functionalities:
+
+- supporting SSC services to access subscribed AI capabilities;
+- notifying the SSC services of the status of their subscribed AI capabilities, if needed.
+
+With reference point AISE-2, SSC services can use uniform approaches to access subscribed AI capabilities.
+
+## **8.7 AI model-functional component**
+
+A group of AM-FCs provides AI capabilities, such as predicting weather, recognizing images and voices, and controlling robots. The AI models can be deployed both within and outside AISE.
+
+AISE provides underlying infrastructures to allow the AI models to be performed.
+
+## **8.8 AI model agent-functional component**
+
+The AMA-FCs interact directly with corresponding external AI models through reference point AISE-4 subject to the requests of SSC services. The AMA-FCs transfer the requests for AI capabilities from SSC services to the corresponding external AI models, and transfer the responses in the opposite direction.
+
+An AMA-FC can interact with one or multiple AI capabilities at the same time.
+
+The AMA-FCs, coordinating with other FCs of AISE, provide the following functionalities:
+
+- tracking the status of exposed AI capabilities, e.g., available or unavailable;
+- interacting with corresponding external AI models to support SSC services to access exposed AI capabilities.
+
+NOTE 1 – When an SSC service subscribes to one AI capability published in AISE, if needed, AMA-FC can interact with the corresponding external AI models that expose the AI capability to check remote access permission.
+
+NOTE 2 – The AMA-FCs can provide data format transformation between AISE and the external AI models. This Recommendation does not specify mechanisms for data or protocol format transformation between the AMA-FCs and the external AI models.
+
+## **8.9 Reference points**
+
+### **8.9.1 AISE-1**
+
+Reference point AISE-1 is exposed by the ACM-FC, which supports SSC services to discover and subscribe to exposed AI capabilities in AISE.
+
+### **8.9.2 AISE-2**
+
+Reference point AISE-2 is exposed by the ACP-FC, which supports SSC services accessing the subscribed AI capabilities, and get notifications for the status of their subscribed AI capabilities, if needed.
+
+### **8.9.3 AISE-3**
+
+Reference point AISE-3 is exposed by the AMM-FC, which supports external AI services to deploy and expose AI capabilities in AISE.
+
+### **8.9.4 AISE-4**
+
+Reference point AISE-4 is exposed by the AMA-FC, which supports interaction between the AI model agents of AISE and external AI models of the AI services.
+
+# **9 Common capabilities of AISE**
+
+This clause provides common capabilities that correspond to the requirements listed in clause 7.
+
+## **9.1 Training of AI models**
+
+AISE can provide underlying infrastructures (such as computational devices, computational frameworks, models) to support the training of AI models in AISE.
+
+The trained AI models can be deployed in AISE, and can be retrained and updated according to its policies.
+
+AISE may open SSC data to AI services according to the rules and policies of AISE. This Recommendation does not specify how to open SSC data to AI services.
+
+## **9.2 Publication of AI capabilities**
+
+AISE is able to allow exposed AI capabilities to be performed both within and outside AISE.
+
+AISE is able to collect information on AI capabilities to be exposed to SSC services. The information about exposed AI capabilities includes, but is not limited to:
+
+- names of the AI capabilities;
+- descriptions of the AI capabilities;
+- access approaches and relevant parameters; and
+- access profiles.
+
+AISE is able to publish collected information about AI capabilities, in order to allow SSC services to discover and subscribe.
+
+If AI models are deployed in AISE, AI services can directly expose their AI capabilities in AISE.
+
+If an AI model is deployed outside AISE, AISE can deploy a corresponding AI model agent, which enables AISE and external AI model interaction. In this case, external AI models can use reference point AISE-3 to expose their AI capabilities.
+
+Clause III.1 provides a reference procedure for publishing AI capabilities.
+
+## **9.3 Subscription to AI capabilities**
+
+AISE is able to allow SSC services to discover and subscribe to published AI capabilities in AISE, through exposed reference point AISE-1.
+
+AISE is able to support an SSC service to subscribe to one or more AI capability and the subscribed AI capabilities may be exposed by one or more AI services.
+
+In the subscription process, AISE is able to validate access permissions according to the policies of AISE and the access profiles related to AI capabilities.
+
+Alternatively, AISE is also able to connect to AI services that expose AI capabilities to negotiate access permission.
+
+Clause III.2 provides a reference procedure for subscribing to published AI capabilities.
+
+NOTE – This Recommendation does not specify a mechanism of interaction between AISE and AI services.
+
+## **9.4 Access to AI capabilities**
+
+When an SSC service requests access to subscribed AI capabilities through exposed reference point AISE-2, AISE is able to verify the access permission, if needed.
+
+If the AI capabilities are exposed by the AI models in AISE, then AISE is able to call the AI models to perform the requested AI capabilities. Clause III.3 provides reference procedures for accessing subscribed AI capabilities in this scenario.
+
+If the AI capabilities are exposed by external AI models outside of AISE, then AISE is able to invoke the AI model agents to access the target AI capabilities, through exposed reference point AISE-3. Clause III.4 provides reference procedures for accessing subscribed AI capabilities in this scenario.
+
+# **10 Security consideration**
+
+AISE, SSC services and AI services are usually deployed in different domains and may be in untrusted environments. AISE is required to provide security mechanisms to authorize and authenticate SSC services to discover, subscribe and access AI capabilities.
+
+Additionally, the security mechanism should support security transportation technologies when the SSC data is transported between AISE and the SSC services, and between AISE and the AI services.
+
+# Appendix I
+
+## Working modes of AISE to provide AI services to SSC services
+
+(This appendix does not form an integral part of this Recommendation.)
+
+There are three types of working modes, classified by the management methods of AI capabilities in AISE: tightly coupled, loosely coupled and hybrid.
+
+### I.1 Tightly coupled working mode
+
+In the tightly coupled working mode, AI models are tightly coupled with AISE (see Figure I.1). AISE manages the AI models and SSC data, exposes their AI capabilities and supplies them to IoT devices via SSC services.
+
+In this working mode, AI service providers deploy external AI models (such as models $M_1 \dots M_k$ ) in AISE as internal AI models (such as AI models $A_1 \dots A_k$ ). Furthermore, AI service providers also can train their AI models in AISE using SSC data as opened by AISE.
+
+When SSC services receive requests from IoT devices related to AI capabilities exposed by AISE, the SSC services forward them to AISE. Then AISE invokes the internal AI models to perform the requested AI services.
+
+
+
+The diagram illustrates the tightly coupled working mode architecture. It is divided into two main sections by a dashed line labeled 'Clouds' and 'SSC'.
+
+**Top Section (AI service providers):** Contains two dashed boxes representing 'AI service A1' and 'AI service Ak'. Each box contains an icon of a server rack and a box labeled 'AI model M1' and 'AI model Mk' respectively. Ellipses between the boxes indicate additional services.
+
+**Middle Section (AISE provider):** A solid rectangular box labeled 'AISE provider' contains 'AI model A1' and 'AI model Ak' with ellipses between them. A dashed arrow labeled 'Deploy models in SSC' points from the AI service providers to the AISE provider. A double-headed arrow labeled 'Access AI capabilities' connects the AISE provider to the SSC service providers.
+
+**Bottom Section (SSC service providers and IoT devices):** Contains two dashed boxes representing 'SSC service C1' and 'SSC service Cn' with ellipses between them. A dashed arrow labeled 'Access SSC services' points from the IoT devices to the SSC service providers. A double-headed arrow labeled 'Access AI capabilities' connects the AISE provider to the SSC service providers.
+
+**IoT devices:** A dashed box at the bottom contains icons of a camera, a mobile phone, a desktop computer, and a laptop, labeled 'IoT devices'.
+
+**Labels and Arrows:**
+
+- 'Clouds' and 'SSC' are labels for the dashed line separating the top and bottom sections.
+- 'Deploy models in SSC' is a dashed arrow pointing from AI service providers to the AISE provider.
+- 'Access AI capabilities' is a double-headed arrow connecting the AISE provider and the SSC service providers.
+- 'Access SSC services' is a dashed arrow pointing from IoT devices to the SSC service providers.
+
+Y.4470(20)\_FI.1
+
+Diagram of the tightly coupled working mode showing the flow from AI service providers to AISE provider and then to SSC service providers and IoT devices.
+
+Figure I.1 – Tightly coupled working mode
+
+### I.2 Loosely coupled working mode
+
+In the loosely coupled working mode, AI models are loosely coupled with AISE (see Figure I.2). AISE manages SSC data and supports the AI service providers to train and deploy their AI models (such as models $M_1 \dots M_k$ ) in SSC. These AI models are external AI models and are deployed outside of AISE.
+
+In this working mode, AISE may create internal AI agents (such as AI model agents $A_1 \dots A_k$ ) corresponding to the external AI models and expose related AI capabilities. The internal AI model agents act as bridge. When SSC services receive requests from IoT devices related to AI capabilities exposed by AISE, the SSC services forward these requests to AISE. AISE then invokes the external AI models, via corresponding internal AI model agents, to perform the requested AI capabilities.
+
+
+
+The diagram illustrates the loosely coupled working mode architecture, organized into three main layers separated by dashed lines: Clouds, SSC, and IoT devices.
+
+- Clouds Layer:** Contains **AI service providers** (AI service $A_1$ to $A_k$ ) each hosting an **AI model** ( $M_1$ to $M_k$ ). A dashed line labeled "Clouds" separates this layer from the SSC layer.
+- SSC Layer:** Contains **AI service providers** (AI service $A_1$ to $A_k$ ) each hosting an **AI model** ( $M_1$ to $M_k$ ). A dashed line labeled "SSC" separates this layer from the IoT devices layer.
+- IoT devices Layer:** Contains **SSC service consumers** (IoT devices) and **SSC service providers** (SSC service $C_1$ to $C_n$ ).
+
+**Interactions:**
+
+- Deploy models in SSC:** Dashed arrows point from the AI models in the Clouds layer to the AI models in the SSC layer.
+- Access external AI capabilities:** Double-headed arrows connect the AI models in the SSC layer to the **AISE provider** (AI model agent $A_1$ to $A_k$ ).
+- Access AI capabilities:** Double-headed arrows connect the AISE provider to the SSC service providers.
+- Access SSC services:** Double-headed arrows connect the SSC service providers to the IoT devices.
+
+**Legend:**
+
+- AI service providers
+- AI model
+- AI model agent $A_1$ to $A_k$
+- SSC service providers
+- SSC service consumers
+- IoT devices
+
+Y.4470(20)\_FI.2
+
+Diagram of the loosely coupled working mode showing the interaction between AI service providers, AISE, SSC service providers, and IoT devices.
+
+Figure I.2 – Loosely coupled working mode
+
+### I.3 Hybrid working mode
+
+In the hybrid working mode, some AI models are tightly coupled with AISE, and some AI models are loosely coupled with AISE.
+
+In this working mode, when SSC services receive requests, from IoT devices, related to AI capabilities exposed by AISE, the SSC services forward these requests to AISE. If the AI capabilities are performed by external AI models, the AI model agents forward the requests to the corresponding AI services to perform the requested AI capabilities. If the AI capabilities are performed by internal AI models, AISE then invokes internal AI models to perform the requested AI capabilities.
+
+
+
+The diagram illustrates the Hybrid working mode architecture, organized into several layers separated by dashed lines:
+
+- Clouds:** Contains **AI service providers** with **AI services** and **AI models**. A dashed line separates this layer from the **SSC** layer.
+- SSC:** Contains **AI service providers** with **AI services** and **AI models**. A dashed line separates this layer from the **AISE provider** layer.
+- AISE provider:** Contains **AI model agents**, **AI models**, and **AISE**. It is connected to the **SSC** layer via **Access external AI capabilities** and **Access AI capabilities**.
+- SSC service providers:** Contains **SSC service C1**, **SSC service Cn**, and **SSC services**. It is connected to the **AISE provider** layer via **Access AI capabilities** and **Access SSC services**.
+- SSC service consumers:** Contains **IoT devices** (represented by icons of a camera, a mobile phone, a desktop computer, and a laptop). It is connected to the **SSC service providers** layer via **Access SSC services**.
+
+Arrows indicate the flow of data and requests between these components. The diagram is labeled **Y.4470(20)\_F1.3** in the bottom right corner.
+
+Diagram of the Hybrid working mode architecture showing the flow from IoT devices through SSC services and AISE to AI service providers.
+
+Figure I.3 – Hybrid working mode
+
+# Appendix II
+
+## Use cases of AISE for SSCs
+
+(This appendix does not form an integral part of this Recommendation.)
+
+This appendix provides use cases to illustrate the concept of AISE.
+
+### II.1 Use case: promoting smart traffic controlling services
+
+This case shows smart traffic controlling (STC) services in an SSC that utilizes AISE to integrate and access AI capabilities for SSC traffic control.
+
+The STC services can collect a large volume of traffic-related data from diverse resources (e.g., city citizens, traffic sensors and traffic tools) in a short time. The data format may be, for example, video, audio or text. Usually STC services need to process data in real time and make decisions to control SSC traffic.
+
+Generally, STC service providers are the local government of the SSC or its contractors, which usually do not have enough technical and financial resources to develop their AI capabilities. Therefore, it is natural that STC service providers will integrate the AI capabilities of third parties, which, however, are usually not particular to a special STC service, because it may be that third parties do not get enough traffic-related SSC data to train their AI capabilities for STC services.
+
+AISE can be deployed by a government or its contractors; this is shown in Figure II.1. AISE is in the SSC and it can collect traffic-related data through STC services.
+
+AI service providers can deploy their common AI capabilities (e.g., for video, audio or text) in AISE, and if permitted, they also can design and train local AI capabilities in AISE. Because of the use of local traffic-related data, locally trained AI capabilities are more applicable to special STC services.
+
+
+
+Figure II.1 – Use case for smart traffic controlling services. The diagram illustrates a multi-layer architecture. At the top, 'AI service providers' offer 'AI services' (video, audio, text) from the 'Clouds'. These services are accessed by 'Smart sustainable cities (SSCs)' through an 'AISE' (Artificial Intelligence Service Engine) block. AISE is designed and trained for smart traffic controlling. It exchanges traffic-related data with an 'STC service' (Smart Traffic Controlling service) and accesses AI capabilities like video analysis and image/audio recognition. The STC service is responsible for 'Smart traffic controlling' and collects data from various sources including cameras, sensors, and 'Offices for traffic controlling'. The diagram is labeled Y.4470(20)\_FII.1.
+
+**Figure II.1 – Use case for smart traffic controlling services**
+
+In this case, through AISE, STC services can integrate and access applicable AI capabilities for SSC traffic control.
+
+### **II.2 Use case: promoting smart appliance voice control services**
+
+This case shows a smart appliance voice control (SAVC) service in smart homes using AISE to process and understand users' voices.
+
+The SAVC service enables users to simply speak to a terminal (e.g., smart phone, smart speaker) in a natural way to open, close or operate appliances conveniently, instead of using specific applications.
+
+Generally, SAVC service providers are smart appliance manufacturers, which only integrate communication modules into their traditional home appliances to make them smarter, but do not have enough AI capabilities to develop a voice control service. For this purpose, AISE may help SAVC service providers integrate third-party AI capabilities easily and flexibly.
+
+As shown in Figure II.2, the SAVC service provider can access AISE, which contains the common AI capabilities for audio deployed by the AI service provider. In this case, the SAVC service receives voice input from users and sends it to AISE for processing, then the instructions derived from the input by relevant AI capabilities in AISE is transmitted back to smart appliances to respond to user requests.
+
+
+
+Figure II.2 – Use case for smart appliance voice control service. The diagram illustrates a system architecture across two layers: Clouds and Sustainable smart cities (SSCs). In the Clouds layer, 'AI services' (represented by server icons) provide 'AI for audio' to the SSCs layer. In the SSCs layer, 'AISE' (AI for Intelligent Service Exposure, represented by server icons in a blue box) 'Access AI capabilities' from the 'SAVC service' (Smart Appliance Voice Control service, represented by server icons). The 'SAVC service' interacts with 'Users' (represented by people and mobile phones) through 'Voice interaction'. The 'SAVC service' then sends 'Control' signals to 'Smart appliances' (represented by icons for an Air cleaner, Air conditioner, Water heater, and others).
+
+Y.4470(20)\_FII.2
+
+**Figure II.2 – Use case for smart appliance voice control service**
+
+### II.3 Use case: promoting smart urban geographical information services
+
+This case shows a smart urban geographic information (UGI) service in an SSC integrating and accessing AI capabilities exposed by AISE to process SSC geographical information.
+
+The UGI service can collect a large volume of urban geographical data from diverse resources in an SSC in a short time, such as city geographical information, digital maps, vehicle radars, cameras, traffic sensors and tools (see Figure II.3).
+
+Using the AI capabilities exposed by AISE (e.g., related to the processing of images, video, audio, text and data searching), the UGI service can reconstruct geographical information according to user requests.
+
+Take the three-dimensional (3D) map reconstruction as an example.
+
+The UGI service can reconstruct and simulate the real world with 3D effects and bound the 3D maps with some other information (e.g., hotels). Making 3D maps is not only based on multiple data sources including at least data collected in real time, historical collected data and location data, but also on AI models and AI algorithms.
+
+With exposed AI capabilities (such as for voice intelligent interaction), the UGI service can more accurately understand the needs of users and output more information to them. For example, users only need to input their demands to book hotels by voice and the 3D maps can quickly recommend hotels according to user preferences, while also helping users complete the reservation, plan the best route and remind them of the departure time. It can provide users with personalized one-stop travel decisions.
+
+
+
+The diagram illustrates the use case for promoting smart urban geographical information services. It shows the following components and interactions:
+
+- AI models/AI model agents (Processing of video, image, text, space, etc.) AISE**: A solid light-blue box at the top containing server icons and the text "AISE".
+ - A self-loop arrow on the right is labeled "Design and train AI capabilities for geographic information processing".
+ - Two double-headed arrows connect the AISE box to the UGI service box, labeled "AI capability accessing" and "SSC data sharing".
+- UGI service**: A dashed box in the middle containing server icons.
+ - A dashed arrow labeled "SSC data collecting" points from the UGI service box down to the Urban geographic data box.
+ - A dashed arrow labeled "Access UGI service" points from the UGI application on the right to the UGI service box.
+- Urban geographic data (Video, image, text, space, etc.)**: A dashed box at the bottom representing the data source.
+- UGI application**: Represented by a smartphone and a person icon on the right side of the diagram.
+
+Y.4470(20)\_FII.3
+
+Diagram illustrating the use case for promoting smart urban geographical information services. The diagram shows the flow of data and services between AI models (AISE), UGI services, and urban geographic data.
+
+**Figure II.3 – Use case for promoting smart urban geographical information services**
+
+In this case, through AISE, the UGI service can integrate and access applicable AI capabilities, and provide citizens and business entities with more geographical information.
+
+# Appendix III
+
+## Common procedures of AISE for SSCs
+
+(This appendix does not form an integral part of this Recommendation.)
+
+This appendix provides some common procedures to illustrate the reference architectures (see clause 8) and common capabilities (see clause 9) of AISE.
+
+### III.1 Publication of the AI capabilities to be exposed
+
+Figure III.1 shows two common procedures of an AI service to expose and publish its AI capabilities in AISE; the major procedures are outlined in steps 1 to 6.
+
+Step 1: The AI service registers its AI capabilities to AISE through the reference point AISE-1. The registration data provided by the AI service includes the information on the AI service and the information on the AI capabilities to be exposed (see clause 9.2).
+
+Steps 2 and 3: The AMM-FC, collaborating with other FCs of AISE, processes the registration request, including validating the information and checking permissions.
+
+If the registration request is validated and accepted, the AI capabilities are exposed in AISE and relevant information is published by AISE.
+
+Steps 4 and 5: AISE sends a response to the AI service. The response information includes whether the registration request is accepted, whether the AI capabilities are exposed and the publishing information if published.
+
+Step 6: If the registration request is accepted and exposed AI capabilities are published, the AI service should update the status of the AI capabilities to AISE when the status is changed.
+
+
+
+```
+sequenceDiagram
+ participant AISE as AISE
+
+ participant AMM-FC as AMM-FC
+
+ participant ACM-FC as ACM-FC
+
+ participant PM-FC as PM-FC
+
+ participant AI_service as AI service
+
+ AISE-->>AMM-FC
+ AISE-->>ACM-FC
+ AISE-->>PM-FC
+
+ AI_service->>ACM-FC: 1. Registration
+ ACM-FC->>AMM-FC: 2. Check permission
+ AMM-FC->>PM-FC: 3. Publish AI capabilities
+ PM-FC->>ACM-FC: 4. Response
+ ACM-FC->>AI_service: 5. Response
+ AI_service->>ACM-FC: 6. Status notification
+ ACM-FC->>AMM-FC: 6. Status notification
+ AMM-FC->>PM-FC: 6. Status notification
+```
+
+The diagram illustrates the sequence of operations for exposing and publishing AI capabilities. It involves three main entities: the AI service and the AISE functional components (AMM-FC, ACM-FC, and PM-FC). The AISE components are grouped within a dashed box. The process follows six steps: 1. Registration from the AI service to ACM-FC; 2. Check permission from ACM-FC to AMM-FC; 3. Publish AI capabilities from AMM-FC to PM-FC; 4. Response from PM-FC to ACM-FC; 5. Response from ACM-FC to the AI service; and 6. Status notification from the AI service to ACM-FC, which then propagates to AMM-FC and PM-FC.
+
+Sequence diagram showing the flow for exposing and publishing AI capabilities between the AI service and AISE (AMM-FC, ACM-FC, PM-FC).
+
+Y.4470(20)\_FIII.1
+
+Figure III.1 – Flow for exposing and publishing AI capabilities
+
+### **III.2 Subscription to exposed AI capabilities**
+
+Figure III.2 shows the common procedures of an SSC service subscribing to exposed AI capabilities in AISE; the major procedures are outlined in steps 1 to 7.
+
+Step 1: The SSC service sends a subscription request to AISE to subscribe to one or a group of exposed AI capabilities. The target AI capabilities can be exposed by one or more AI services.
+
+Step 2: AISE validates the subscription request and checks access permission of the SSC service for subscribing to the target exposed AI capabilities.
+
+AISE checks access permission according to the access policies of the target exposed AI capabilities and the policies of AISE.
+
+AISE, if needed, can get external access permission from the AI services that expose the target AI capabilities. In this case, if the target AI capabilities are provided by different AI services, AISE connects them one by one.
+
+Steps 3, 4, 5 and 6: After checking the access permission, AISE sends a subscription response to the SSC service and sends a subscription notification to the AI services that expose the target AI capabilities.
+
+If the subscription request is validated and accepted, the subscription response to the SSC service includes information about subscribed AI capabilities (see clause 9.2). In this case, the subscription notification sent to AI services includes subscription information (e.g., who is subscribing to the AI capabilities and which AI capabilities are subscribed).
+
+If the subscription request is not validated or not accepted, the subscription response to the SSC service will include the rejection information and AISE may not send subscription information to the AI services.
+
+Step 7: If the subscription request is accepted, AISE sends the SSC service the status notification that is received from the AI services continuously; otherwise, AISE will not send anything to the SSC service.
+
+NOTE – From the perspective of the SSC service, it is transparent that the ACM-FCs interact with AI services which exposing AI capabilities. The SSC service subscribes to the published AI capabilities from AISE and does not interact directly with the AI services.
+
+
+
+```
+
+sequenceDiagram
+ participant SSC as SSC service
+ participant AISE as AISE
+ACM-FC
+AM-FC
+AMP-FC
+ participant PM as PM-FC
+ participant AI as AI service
+
+ SSC->>AISE: 1. Subscription request
+ activate AISE
+ AISE->>AISE: 2. Access control
+ AISE->>PM: 2. Access control
+ AISE-->>AI: 2. Access control
+ deactivate AISE
+ AISE->>PM: 3. Subscription request
+ AISE-->>AI: 4. Subscription notification
+ deactivate AISE
+ PM->>AISE: 5. Subscription response
+ AISE-->>SSC: 6. Subscription response
+ deactivate AISE
+ AISE->>PM: 7. Status notification
+ AISE-->>AI: 7. Status notification
+ deactivate AISE
+ PM->>SSC: 7. Status notification
+ deactivate PM
+
+```
+
+Y.4470(20)\_FIII.2
+
+Sequence diagram showing the flow for subscribing exposed AI capabilities between SSC service, AISE (ACM-FC, AM-FC, AMP-FC, PM-FC), and AI service.
+
+**Figure III.2 – Flow for subscribing exposed AI capabilities**
+
+### III.3 Accessing the subscribed AI capabilities in AISE
+
+Figure III.3 shows the common procedures of an SSC service accessing subscribed AI capabilities through AISE; the major procedures are outlined in steps 1 to 5.
+
+Step 1: The SSC service sends AISE the request to access the subscribed AI capabilities, through the reference point AISE-2. In the access request, it may include one or more AI capabilities and the target AI capabilities may be exposed by one or more AI services.
+
+Step 2: AISE validates the access request and checks access permission. If part or all of the target AI capabilities in the access request are not subscribed, AISE may reject the access request.
+
+NOTE – There are many methods to control access permission. The method in step 2 is a simple example. This Recommendation does not limit the methods to control access permission.
+
+Steps 3, 4 and 5: If the access request is rejected, AISE sends the SSC service the access response, which includes the reasons for the rejection. AISE then ends the processes for the access request.
+
+If the access request is accepted, the ACP-FCs of AISE send access requests to the AI services as exposing the target AI capabilities. In this case, if the target AI capabilities are exposed by different AI services, AISE will call the corresponding AM-FC to connect the appropriate AI services.
+
+AISE receives the access response from the AI services and forwards it to the SSC service.
+
+When the access response is received for its access request, the SSC service may end this access request.
+
+
+
+```
+
+sequenceDiagram
+ participant SSC as SSC service
+ participant AISE as AISE
+ participant PMFC as PM-FC
+AMA-FC
+ participant ACPFC as ACP-FC
+ participant AMFCs as AM-FCs
+
+ SSC->>ACRFC: 1. Access request
+ activate ACPFC
+ ACPFC->>PMFC: 2. Access control
+ ACPFC->>AMFCs: 2. Access control
+ activate PMFC
+ activate AMFCs
+ AMFCs->>ACRFC: 3. Access capabilities
+ deactivate AMFCs
+ ACPFC->>PMFC: 4. Access response
+ deactivate ACPFC
+ PMFC->>SSC: 5. Access response
+ deactivate PMFC
+
+```
+
+Y.4470(20)\_FIII.3
+
+Sequence diagram showing the flow for accessing subscribed AI capabilities in AISE. The diagram involves four lifelines: SSC service, PM-FC AMA-FC, ACP-FC, and AM-FCs. The AISE entity is represented by a dashed box containing PM-FC AMA-FC, ACP-FC, and AM-FCs. The flow is as follows: 1. Access request from SSC service to ACP-FC. 2. Access control from PM-FC AMA-FC to ACP-FC and from ACP-FC to AM-FCs. 3. Access capabilities from AM-FCs to ACP-FC. 4. Access response from ACP-FC to PM-FC AMA-FC. 5. Access response from PM-FC AMA-FC to SSC service.
+
+**Figure III.3 – Flow for accessing subscribed AI capabilities in AISE**
+
+### III.4 Accessing the subscribed AI capabilities outside of AISE
+
+Figure III.4 shows the common procedures of an SSC service to access subscribed AI capabilities through AISE. The main difference is the AI capabilities are performed by external AI models through the supports of the AMA-FCs.
+
+The major procedures are outlined in steps 1 to 5.
+
+Step 1: Same as step 1 in clause III.3.
+
+Step 2: Similar to step 2 in clause III.3.
+
+NOTE – The access permission may be checked further by external AI services because they provide the requested AI capabilities. Furthermore, this Recommendation does not limit the methods to control access permission.
+
+Steps 3, 4 and 5: The ACP-FC forwards the requests to the AMA-FC that is bound to the requested AI capabilities, and then the AMA-FC interacts with external AI services (invoking AI capabilities) according to the requests and forwards the responses from external AI services to the SSC service.
+
+
+
+```
+
+sequenceDiagram
+ participant SSC as SSC service
+ participant AISE as AISE
+ participant PM as PM-FC
+AMM-FC
+ participant ACP as ACP-FC
+ participant AMA as AMA-FCs
+ participant AI as AI service
+
+ SSC->>ACP: 1. Accessing request
+ activate ACP
+ ACP->>AMA: 2. Access control
+ activate AMA
+ AMA->>PM: 2. Access control
+ deactivate AMA
+ ACP->>AMA: 3. Accessing request
+ activate AMA
+ AMA->>AI: 4. Invoking AI capabilities
+ activate AI
+ AI-->>AMA:
+ deactivate AI
+ AMA->>ACP: 5. Response
+ deactivate AMA
+ ACP->>SSC: 5. Response
+ deactivate ACP
+
+```
+
+Y.4470(20)\_FIII.4
+
+Sequence diagram showing the flow for accessing subscribed AI capabilities outside of AISE. The diagram involves four main entities: SSC service, AISE (containing PM-FC/AMM-FC, ACP-FC, and AMA-FCs), and AI service. The process follows five steps: 1. Accessing request from SSC service to ACP-FC; 2. Access control between PM-FC/AMM-FC and AMA-FCs; 3. Accessing request from ACP-FC to AMA-FCs; 4. Invoking AI capabilities from AMA-FCs to AI service; 5. Response from ACP-FC to SSC service.
+
+**Figure III.4 – Flow for accessing subscribed AI capabilities outside of AISE**
+
+# Bibliography
+
+- [b-ITU-T Y.2091] Recommendation ITU-T Y.2091 (2011), *Terms and definitions for next generation networks*.
+- [b-ITU-T Y.3172] Recommendation ITU-T Y.3172 (2019), *Architectural framework for machine learning in future networks including IMT-2020*.
+- [b-ITU-T Y.4900] Recommendation ITU-T Y.4900/L.1600 (2016), *Overview of key performance indicators in smart sustainable cities*.
+- [b-ITU-R M.1224-1] Recommendation ITU-R M.1224-1 (2012), *Vocabulary of terms for international mobile telecommunications (IMT)*.
+- [b-ETSI GR ENI 004] ETSI GR ENI 004 V2.1.1 (2019); *Experiential networked intelligence (ENI); Terminology for main concepts in ENI*.
+- [b-ISO/IEC 2382] ISO/IEC 2382:2015, *Information technology – Vocabulary*.
+
+
+
+## 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 |
+| 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 | 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 |
\ No newline at end of file
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new file mode 100644
index 0000000000000000000000000000000000000000..5d13c989be3b6edf039b6f0f7fe84f2c007d3a41
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+++ b/marked/Y/T-REC-Y.4604-202309-I_PDF-E/raw.md
@@ -0,0 +1,749 @@
+
+
+# Recommendation
+
+## **ITU-T Y.4604 (09/2023)**
+
+SERIES Y: Global information infrastructure, Internet protocol aspects, next-generation networks, Internet of Things and smart cities
+
+Internet of things and smart cities and communities –
+Services, applications, computation and data processing
+
+---
+
+## **Metadata for camera sensing information of autonomous mobile Internet of things devices**
+
+## ITU-T Y-SERIES RECOMMENDATIONS
+
+## Global information infrastructure, Internet protocol aspects, next-generation networks, Internet of Things and smart cities
+
+| | |
+|----------------------------------------------------------------|----------------------|
+| GLOBAL INFORMATION INFRASTRUCTURE | Y.100-Y.999 |
+| INTERNET PROTOCOL ASPECTS | Y.1000-Y.1999 |
+| NEXT GENERATION NETWORKS | Y.2000-Y.2999 |
+| FUTURE NETWORKS | Y.3000-Y.3499 |
+| CLOUD COMPUTING | Y.3500-Y.3599 |
+| BIG DATA | Y.3600-Y.3799 |
+| QUANTUM KEY DISTRIBUTION NETWORKS | Y.3800-Y.3999 |
+| INTERNET OF THINGS AND SMART CITIES AND COMMUNITIES | Y.4000-Y.4999 |
+| General | Y.4000-Y.4049 |
+| Definitions and terminologies | Y.4050-Y.4099 |
+| Requirements and use cases | Y.4100-Y.4249 |
+| Infrastructure, connectivity and networks | Y.4250-Y.4399 |
+| Frameworks, architectures and protocols | Y.4400-Y.4549 |
+| Services, applications, computation and data processing | Y.4550-Y.4699 |
+| Management, control and performance | Y.4700-Y.4799 |
+| Identification and security | Y.4800-Y.4899 |
+| Evaluation and assessment | Y.4900-Y.4999 |
+
+*For further details, please refer to the list of ITU-T Recommendations.*
+
+# Recommendation ITU-T Y.4604
+
+# Metadata for camera sensing information of autonomous mobile Internet of things devices
+
+## Summary
+
+Recommendation ITU-T Y.4604 specifies metadata for camera sensing information (MCSI) and describes characteristics and features of individual pieces of MCSI working on autonomous mobile Internet of things (IoT) devices.
+
+In the case of low-cost and low-resolution IoT camera sensor devices, it is not possible to support full-featured camera sensing information due to their resource-limited capabilities. Traditional full-performance digital camera devices provide complex metadata such as camera settings (stimulus, sensitivity, shutter speed, etc.), time, location information and camera model.
+
+There is no guidance for compliant and compromised IoT camera-sensing metadata from different manufacturers. This causes problems related to interchangeable metadata. It is essential therefore to provide basic and minimal camera-sensing metadata to enable interoperability between IoT applications and services.
+
+## History \*
+
+| Edition | Recommendation | Approval | Study Group | Unique ID |
+|---------|----------------|------------|-------------|--------------------|
+| 1.0 | ITU-T Y.4604 | 2023-09-13 | 20 | 11.1002/1000/15480 |
+
+## Keywords
+
+IoT autonomous mobile device, IoT image sensor, metadata, sensing information.
+
+---
+
+\* To access the Recommendation, type the URL 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 .
+
+© ITU 2023
+
+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..... | 2 |
+| 4 Abbreviations and acronyms ..... | 2 |
+| 5 Conventions ..... | 2 |
+| 6 Introduction ..... | 3 |
+| 7 General MCSI metadata characteristics..... | 4 |
+| 7.1 Sensing methods for MCSI ..... | 4 |
+| 7.2 Data structure for MCSI ..... | 5 |
+| 8 MCSI metadata elements..... | 5 |
+| 8.1 Sensor information metadata..... | 5 |
+| 8.2 Time information metadata ..... | 10 |
+| 8.3 Location and position information metadata..... | 11 |
+| 8.4 Spatial information metadata..... | 13 |
+| 8.5 Device information metadata ..... | 17 |
+| Appendix I – Use case for a building defect monitoring service using autonomous
mobile Internet of things devices..... | 18 |
+| Bibliography..... | 21 |
+
+
+
+# Recommendation ITU-T Y.4604
+
+# Metadata for camera sensing information of autonomous mobile Internet of things devices
+
+# 1 Scope
+
+This Recommendation specifies metadata for camera sensing information (MCSI) and describes details of characteristics and features of MCSI working on autonomous mobile Internet of things (IoT) devices (AMIDs).
+
+In particular, the scope of this Recommendation includes:
+
+- sensing methods and data structure for MCSI;
+- specification of characteristics and features of individual pieces of MCSI.
+
+NOTE 1 – Regulation-related information metadata, such as privacy, personally identifiable information and face recognition, lie outside the scope of this Recommendation.
+
+NOTE 2 – This Recommendation is not intended to apply to all vehicles, environments or applications, but does apply primarily to sensors for aviation or unmanned aircraft system devices and delivery service robots.
+
+# 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.
+
+None.
+
+# 3 Definitions
+
+## 3.1 Terms defined elsewhere
+
+This Recommendation uses the following terms defined elsewhere:
+
+**3.1.1 application** [b-ITU-T Y.2091]: A structured set of capabilities, which provide value-added functionality supported by one or more services, which may be supported by an API interface.
+
+**3.1.2 device** [b-ITU-T Y.4000]: With regard to the Internet of things, this is a piece of equipment with the mandatory capabilities of communication and the optional capabilities of sensing, actuation, data capture, data storage and data processing.
+
+**3.1.3 Internet of things (IoT)** [b-ITU-T Y.4000]: A global infrastructure for the information society, enabling advanced services by interconnecting (physical and virtual) things based on existing and evolving interoperable information and communication technologies.
+
+NOTE 1 – Through the exploitation of identification, data capture, processing and communication capabilities, the IoT makes full use of things to offer services to all kinds of applications, whilst ensuring that security and privacy requirements are fulfilled.
+
+NOTE 2 – From a broader perspective, the IoT can be perceived as a vision with technological and societal implications.
+
+**3.1.4 metadata** [b-ITU-T Y.1901]: Structured, encoded data that describe characteristics of information-bearing entities to aid in the identification, discovery, assessment and management of the described entities.
+
+**3.1.5 smart sustainable city** [b-ITU-T Y.4900]: A smart sustainable city is an innovative city that uses information and communication technologies (ICTs) and other means to improve quality of life, efficiency of urban operation and services and competitiveness, while ensuring that it meets the needs of present and future generations with respect to economic, social, environmental, as well as cultural aspects.
+
+**3.1.6 terminal device (TD)** [b-ITU-T Y.1901]: An end-user device which typically presents and/or processes the content, such as a personal computer, a computer peripheral, a mobile device, a TV set, a monitor, a VoIP terminal or an audio-visual media player.
+
+## **3.2 Terms defined in this Recommendation**
+
+This Recommendation defines the following term:
+
+**3.2.1 metadata camera sensing information (MCSI)**: A metadata of sensing information captured from an Internet of things camera sensor.
+
+# **4 Abbreviations and acronyms**
+
+This Recommendation uses the following terms and abbreviations:
+
+| | |
+|-------|---------------------------------------------|
+| AMID | Autonomous Mobile Internet of things Device |
+| API | Application Programming Interface |
+| AR | Augmented Reality |
+| BIM | Building Information Modelling |
+| EO | Electro-Optical |
+| EXIF | Exchangeable Image File Format |
+| GNSS | Global Navigation Satellite System |
+| ICT | Information and Communication Technology |
+| IoT | Internet of Things |
+| IR | Infrared Radiation |
+| JPEG | Joint Photographic Experts Group |
+| LiDAR | Light Detection and Ranging |
+| MCSI | Metadata Camera Sensing Information |
+| MSI | Multispectral Image |
+| TD | Terminal Device |
+| TIFF | Tagged Image File Format |
+| TV | Television |
+| VoIP | Voice over Internet Protocol |
+| VR | Virtual Reality |
+
+# **5 Conventions**
+
+None.
+
+# 6 Introduction
+
+In general, traditional full-performance digital camera devices provide a lot of metadata including information such as camera settings (stimulus, sensitivity, shutter speed), time, location information and camera model. For example, for image file formats, there are exchangeable image file format (EXIF) metadata formats such as Joint Photographic Experts Group (JPEG) and tagged image file format (TIFF). EXIF is a format that stores metadata containing information about images or voice files acquired by digital cameras, including image size, file format, resolution, and camera information such as focal distance, brightness and exposure time. The EXIF format provides complicated and full-featured camera sensing information [b-Exif].
+
+However, in the case of low-cost and low-resolution IoT camera sensor devices, it is not necessary to support full-featured camera sensing information in resource-limited device capabilities. Additionally, there is no guidance currently for compliant and compromised metadata from different manufacturers. Therefore, it is crucial to provide guidance for basic and minimal sensing metadata of IoT camera sensors to enable interoperable IoT applications and services. Consequently, this Recommendation focuses on describing the basic metadata that are essentially required in such environments. Such metadata allow developers to launch IoT application services, and can be complemented with interoperability and provided without conflicting with existing metadata such as EXIF.
+
+An AMID is a type of IoT device with an embedded or connected IoT sensor camera. AMIDs such as delivery service robots, home appliances (robot vacuum cleaners, etc.), and autonomous driving cars are already becoming common in the IoT services market. Recent AMIDs with cameras including different metadata (location, angle of view, temperature, time, etc.) cannot support compliant metadata among different device manufacturers in the market. AMIDs also experience problems due to the lack of common metadata on image sensor information, differences in specifications (units, resolution, criteria, etc.) and specific metadata that are dependent on manufacturers.
+
+Concerning AMIDs, it is important to avoid non-compliant metadata processing while capturing camera sensing information. By standardizing IoT camera sensing metadata, the metadata conflict problem can be resolved and development costs of interoperable data standards for IoT camera-based devices reduced. This standardized IoT camera sensing metadata can be used as a foundational metadata for IoT camera-based services, such as autonomous robot services, building management services and augmented reality or virtual reality (AR/VR) services. Autonomous mobile IoT services can demand metadata of image and video data and these metadata can be applied for various application services. In most IoT application services, these metadata can be combined and applied for visualizing and 3-dimensional spatial information generation.
+
+Figure 6-1 shows an example of a service environment of AMIDs.
+
+
+
+The diagram illustrates a service environment for autonomous mobile IoT devices. It is structured into three main layers:
+
+- IoT applications:** This top layer includes four services: Autonomous robot service, Building management service, AR/VR service, and Map application service.
+- Metadata for camera sensing information (MCSI):** This middle layer, enclosed in a dashed box, contains five types of metadata: Sensor information metadata, Time information metadata, Location and position metadata, Spatial information metadata, and Device information metadata. Below the metadata is a section for **IoT camera sensing methods**, which includes EO (Electro-Optical), MSI (Multispectral Image), and IR (Infrared).
+- Smart city environments:** The bottom layer features a cloud representing **Autonomous mobile IoT devices**. A dashed arrow points from these devices up to the sensing methods, indicating data flow.
+
+Y.4604(23)
+
+Figure 6-1: Example of a service environment of autonomous mobile IoT devices. The diagram shows a hierarchy of components. At the top is 'IoT applications' with four services: Autonomous robot service, Building management service, AR/VR service, and Map application service. Below this is 'Metadata for camera sensing information (MCSI)', which is enclosed in a dashed box. It contains 'Sensor information metadata', 'Time information metadata', 'Location and position metadata', 'Spatial information metadata', and 'Device information metadata'. Below the metadata is 'IoT camera sensing methods' with three methods: EO, MSI, and IR. At the bottom is 'Smart city environments' containing 'Autonomous mobile IoT devices'. A dashed arrow points from the IoT devices up to the sensing methods.
+
+**Figure 6-1 – Example of a service environment of autonomous mobile IoT devices**
+
+# 7 General MCSI metadata characteristics
+
+This clause describes the characteristics of camera sensing and the data structure on which MCSI metadata is based.
+
+## 7.1 Sensing methods for MCSI
+
+IoT camera sensing devices vary and have different characteristics according to sensing types. In general, typical sensing data types include methods such as electro-optical (EO), infrared radiation (IR), multispectral image (MSI), and light detection and ranging (LiDAR) [b-ISO 19130-1].
+
+EO image data digitally acquires images up to a visible light area and an infrared area based on a charge-coupling element. This sensor provides better results than optical sensor data in long-distance and low-clock situations and is the most commonly used sensor.
+
+IR thermal image data detects IR energy emitted by the target to measure the surface temperature of the target. This sensor is characterized in that it maps colours according to the measured temperature value to configure a screen, thereby providing an identification power that EO data cannot provide.
+
+MSI data protect wavelength-specific images divided into about 10 bands in the band of visible or near infrared spectrum. This sensor has fewer bands than hyperspectral data and has a relatively low price compared to hyperspectral sensors. Hyperspectral data also protect all wavelength-specific images subdivided into hundreds to thousands of continuous spectral bands in a narrow band of the near-infrared or intermediate infrared spectrum. This sensor can identify unique components of the target and provides more detailed interpretation information because it has a higher spatial or spectral resolution than a multispectral sensor.
+
+LiDAR image data analyse reflected light by irradiating a target with a laser. This sensor is likely to be used in various fields for storing distance, direction, speed, temperature, and characteristic data.
+
+A gimbal reduces movement vibration to prevent deterioration of the quality of the captured image. By providing metadata such as the photographic angle of the camera or sensor, additional meaning may be added to the acquired image data.
+
+## **7.2 Data structure for MCSI**
+
+This clause explains the data structure used in this Recommendation. This Recommendation aligns with the existing metadata standard format. Table 1 describes the data structure of the MCSI metadata in order to explain features for understanding this Recommendation. The table includes the tag name, a description, and M (mandatory) and O (optional) support levels respectively. It also lists attributes including the unit, the minimum value and maximum value, the exception value, and the resolution, as well as an example and notes.
+
+**Table 1 – MCSI description format used in this Recommendation**
+
+| | | | | |
+|-------------|-----------|-----------|-----------------|---------------------|
+| Tag name | – | | | |
+| Description | | | | Support level (M/O) |
+| – | | | | – |
+| Unit | Min value | Max value | Exception value | Resolution |
+| – | – | – | – | – |
+| Example | – | | | |
+| Note | – | | | |
+
+# **8 MCSI metadata elements**
+
+This clause specifies common and basic camera sensing metadata for IoT camera-based services.
+
+## **8.1 Sensor information metadata**
+
+### **8.1.1 EO sensing type**
+
+The sensor specifies a sensor identifier that acquires sensing data. The type, model name, attachment position, etc. of the sensor may be described. It provides important functions in the distribution of sensing data because the characteristics and specifications of sensing data that can be acquired vary depending on the characteristics and specifications of the sensor.
+
+The sensor information acquired by an AMID depends on the support information of the sensor itself. For example, the geographic area information included in the acquired image may be calculated only when combined with position posture information.
+
+The field of view is an angle at which the sensor can hold an image. When the angle of view, position, and posture information are combined, geographic range information included in the image may be calculated by assuming the altitude as being sea level.
+
+**Table 2 – MCSI EO sensing type for sensor information**
+
+| Tag name | Image.Model | | | |
+|-----------------------------------------------------------------------------------------------------------|-------------|-----------|-----------------|---------------------|
+| Description | | | | Support level (M/O) |
+| Specifies a sensor identifier that acquires sensing data. The type, model name, attachment position, etc. | | | | O |
+| Unit | Min value | Max value | Exception value | Resolution |
+| – | – | – | – | – |
+| Example | – | | | |
+| Note | – | | | |
+
+| Tag name | FieldOfView | | | |
+|-----------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------|-----------|-----------------|---------------------------------|
+| Description | | | | Support level (M/O) |
+| Angle of view of the sensor | | | | M |
+| Unit | Min value | Max value | Exception value | Resolution |
+| ° | 0 | 180 | –1 | $\sim 2.7 \times 10^{-3}^\circ$ |
+| Example | 72.481 2° | | | |
+| Note | Vertical angle is specified as proportional to horizontal angle.
When the angle information is not obtained, a special value (–1) is used. | | | |
+
+### 8.1.2 MSI sensing type
+
+The MSI still image metadata is limited to a still image processed to transmit sensor data acquired by a spectroscopic sensor to a human visual. The MSI sensor metadata includes the definition of the EO still image metadata item, the support level and the geographic reference model, and additional MSI still image fields are added and specified for interpretation.
+
+The spectral sensor measures a value for each wavelength band by dividing the visible light spectrum into several wavelength bands. If the number of wavelength bands to be divided is small, it is divided into multi-spectral, if large, hyper-spectral, and IR sensors are also included in the multi-spectral sensor.
+
+Since the spectroscopic sensor provides a measured value for each divided area by dividing a visible light area within a given measurement range, a sensor standard should be referred to for analysis of the sensed data itself. A sensor standard should also be referred to even when processed into an image.
+
+As previously described, the spectral sensor measures by dividing the visible light area, and the measurement performance is determined according to the number of bands that can be divided and the range of spectra that the sensor can measure. The spectral range means the range of wavelengths that sensors can detect.
+
+MSI information is a reference for the spectral range within the acquired image itself. Information and names of spectral ranges (bands) set to acquire each image are specified. Each pixel in the image has a measured value within an actually divided spectral range, and the arrangement of
+
+colours varies according to the visualization method. Table 3 describes the MCSI MSI sensing type for sensor information.
+
+**Table 3 – MCSI MSI sensing type for sensor information**
+
+| Tag name | MaxNumberOfBands | | | |
+|---------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------|-----------------|---------------------|
+| Description | | | | Support level (M/O) |
+| Number of measurable bands (spectral bands) | | | | O |
+| Unit | Min value | Max value | Exception value | Resolution |
+| – | 1 | 150 | 0 | 1 |
+| Example | 6 | | | |
+| Note | Number of bands can be measured by dividing the visible light area.
Since the image sensor has at least one band, the special value (0) means that a value cannot be input. | | | |
+
+| Tag name | CentralWavelength | | | |
+|---------------------------------------------|---------------------------------------------------------------------------------------------------------------|-----------|-----------------|---------------------|
+| Description | | | | Support level (M/O) |
+| Centre wavelength value in the image (band) | | | | O |
+| Unit | Min value | Max value | Exception value | Resolution |
+| nm | – | – | 0 | 10 |
+| Example | 500 nm | | | |
+| Note | It is specified in units of micro- or nanometres.
If a value cannot be input, a special value (0) is used. | | | |
+
+| Tag name | BandWidth | | | |
+|------------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------|-----------------|---------------------|
+| Description | | | | Support level (M/O) |
+| Bandwidth in an image (band) | | | | O |
+| Unit | Min value | Max value | Exception value | Resolution |
+| nm | – | – | 0 | 10 |
+| Example | 50 nm | | | |
+| Note | Determines the size (bandwidth) of the band around the central wavelength. For example, if the central wavelength is 500 nm and the bandwidth is 50 nm, the band has a spectral range of 450 to 550 nm.
Use a special value (0) if a value cannot be entered. | | | |
+
+| Tag name | BandName | | | |
+|---------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------|-----------------|---------------------|
+| Description | | | | Support level (M/O) |
+| Band name in image (band) | | | | O |
+| Unit | Min value | Max value | Exception value | Resolution |
+| – | 3 | 127 | 000 | – |
+| Example | Red, Green, Blue, RedEdge, NIR | | | |
+| Note | The name of each band is expressed as a string. For example, major bands commonly used in the industry include red, green, blue, red edge, near infrared (NIR), as well as short wavelength infrared, medium wavelength infrared, long wavelength infrared and far infrared.
When a band name is not separately specified, it is expressed as a special value ("000").
| | | |
+
+### 8.1.3 IR sensing type
+
+The IR sensor provides a value measured within the range of the sensor's own standard for infrared rays within a given screen range. The IR sensor metadata includes the definition of the EO still image metadata item, the support level and the geographic reference model, and additional IR still image fields are added and specified for interpretation. In order to interpret the IR sensor data itself, it is necessary to refer to the sensor specification and to refer to it even when processed into an image. The main items corresponding to this are described in Table 4.
+
+IR image information is a reference for the temperature range within the acquired image itself. Each pixel in the image has a value expressed by mapping a colour to an actual measured temperature value, and the arrangement of colours varies according to the visualization method. The maximum and minimum values of the temperature expressed by each pixel of the image are specified as metadata items.
+
+**Table 4 – MCSI IR sensing type for sensor information**
+
+| Tag name | SensorNEDT | | | |
+|-----------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------|-----------------|---------------------|
+| Description | | | | Support level (M/O) |
+| Thermal sensitivity of IR sensors | | | | O |
+| Unit | Min value | Max value | Exception value | Resolution |
+| millikelvins (mK) | 5 | – | –1 | – |
+| Example | 50 mK (0.05°C) | | | |
+| Note | Thermal sensitivity of the thermal image camera, and may be confirmed through signal-to-noise generated when the same signal is generated.
When a value cannot be input, a special value (–1) is used.
| | | |
+
+| Tag name | SensorTemperatureRangeMax | | | |
+|---------------------------------------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------|-----------------|------------------------------------|
+| Description | | | | Support level (M/O) |
+| Maximum temperature value that an IR sensor can measure | | | | O |
+| Unit | Min value | Max value | Exception value | Resolution |
+| °C (Degree) | −50 | 1500 | −1500 | $5 \times 10^{-3}^{\circ}\text{C}$ |
+| Example | 52.325°C | | | |
+| Note | For the resolution of the highest temperature value that the IR sensor can measure, refer to SensorNEDT. When a value cannot be input, a special value −1 500 is used. | | | |
+
+| Tag name | SensorTemperatureRangeMin | | | |
+|---------------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------|-----------------|------------------------------------|
+| Description | | | | Support level (M/O) |
+| Minimum temperature value that an IR sensor can measure | | | | O |
+| Unit | Min value | Max value | Exception value | Resolution |
+| °C (Degree) | −50 | 1500 | −1500 | $5 \times 10^{-3}^{\circ}\text{C}$ |
+| Example | 52.325°C | | | |
+| Note | For the resolution of the lowest temperature value that the IR sensor can measure, refer to SensorNEDT. When a value cannot be input, a special value −1500 is used. | | | |
+
+| Tag name | SensorSpectralRangeMax | | | |
+|---------------------------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------|-----------------|---------------------------------|
+| Description | | | | Support level (M/O) |
+| Maximum wavelength detectable by IR sensors | | | | O |
+| Unit | Min value | Max value | Exception value | Resolution |
+| μm | 0.75 | 1000 | −1000 | $25 \times 10^{-3} \mu\text{m}$ |
+| Example | 1.25 μm | | | |
+| Note | Most IR sensors that can be mounted on a TD have a range of 1 to 14 μm, and this Recommendation specifies the entire IR band to be representable.
If a value cannot be input, a special value (−1000) is used. | | | |
+
+| Tag name | SensorSpectralRangeMin | | | |
+|---------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------|-----------------|---------------------------------|
+| Description | | | | Support level (M/O) |
+| Minimum wavelength detectable by IR sensors | | | | O |
+| Unit | Min value | Max value | Exception value | Resolution |
+| $\mu\text{m}$ | 0.75 | 1000 | −1000 | $25 \times 10^{-3} \mu\text{m}$ |
+| Example | 1.25 $\mu\text{m}$ | | | |
+| Note | Most IR sensors that can be mounted on a TD have a range of 1 to 14 $\mu\text{m}$ , and this Recommendation specifies the entire IR band to be representable.
If a value cannot be input, a special value (−1 000) is used. | | | |
+
+| Tag name | ImageTemperatureRangeMax | | | |
+|----------------------------------------|---------------------------------------------------------|-----------|-----------------|-------------------------------------|
+| Description | | | | Support level (M/O) |
+| Maximum temperature value in the image | | | | O |
+| Unit | Min value | Max value | Exception value | Resolution |
+| $^{\circ}\text{C}$ (Degree) | −50 | 1500 | −1500 | $5 \times 10^{-3} ^{\circ}\text{C}$ |
+| Example | 52.325 $^{\circ}\text{C}$ | | | |
+| Note | The resolution of this value is referred to SensorNEDT. | | | |
+
+| Tag name | ImageTemperatureRangeMin | | | |
+|----------------------------------------|----------------------------------------------------------------------------------------------------------------------|-----------|-----------------|-------------------------------------|
+| Description | | | | Support level (M/O) |
+| Minimum temperature value in the image | | | | O |
+| Unit | Min value | Max value | Exception value | Resolution |
+| $^{\circ}\text{C}$ (Degree) | −50 | 1500 | −1500 | $5 \times 10^{-3} ^{\circ}\text{C}$ |
+| Example | 52.325 $^{\circ}\text{C}$ | | | |
+| Note | The resolution of this value is referred to SensorNEDT. When a value cannot be input, a special value −1500 is used. | | | |
+
+## 8.2 Time information metadata
+
+Time information such as image generation, photographing and storage time is necessary for image generation. Most have an optional support level and include time information, such as image.date, photo.datetime.original, photo.datetime.digitized, TimeStamp and DateStamp. Table 5 describes MCSI for time information.
+
+**Table 5 – MCSI for time information**
+
+| Tag name | Description | Support level (M/O) | Note |
+|-------------------------|------------------------------|---------------------|------|
+| Image.Date | Image creation date and time | O | |
+| Photo.DateTimeOriginal | Date and time of shooting | O | |
+| Photo.DateTimeDigitized | File storage date and time | O | |
+| TimeStamp | UTC time | O | |
+| DateStamp | UTC time | O | |
+
+## 8.3 Location and position information metadata
+
+Location and position information describes the position and attitude of the IoT device. In order to calculate the spatial information of the still image, not only the device but also the attitude of the sensor mounted on the device is required.
+
+The location and position information in Table 6 is specified to have the same unit and value range and resolution, and the altitude and position are specified using a coordinate system. Table 6 describes MCSI for location and position information.
+
+**Table 6 – MCSI for location and position information**
+
+| Tag name | AbsoluteAltitude | | | |
+|-------------------------------------------------------------------------|---------------------------------------------------------------------------------------------------------------------------------------|-----------|-----------------|---------------------|
+| Description | | | | Support level (M/O) |
+| Absolute altitude of the sensor measured based on the average sea level | | | | O |
+| Unit | Min value | Max value | Exception value | Resolution |
+| M | −900 | 19 000 | −19 000 | ~0.3 m |
+| Example | 150.00 m | | | |
+| Note | Feet may be used, but metres are used in this Recommendation. When an altitude value is not input, a special value (−19 000) is used. | | | |
+
+| Tag name | RelativeAltitude | | | |
+|------------------------------------------------------------------------------------------------------------------------|---------------------------------------------------------------------------------------------------------------------------------------|-----------|-----------------|---------------------|
+| Description | | | | Support level (M/O) |
+| Relative elevation of the sensor measured based on the lower surface closest to the gas containing the ground surface. | | | | O |
+| Unit | Min value | Max value | Exception value | Resolution |
+| M | −900 | 19 000 | −19 000 | ~0.3 m |
+| Example | 150.00 m | | | |
+| Note | Feet may be used, but metres are used in this Recommendation. When an altitude value is not input, a special value (−19 000) is used. | | | |
+
+| Tag name | FlightYawDegree | | | |
+|-------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------|-----------------|-----------------------------------|
+| Description | | | | Support level (M/O) |
+| Yaw angle (heading) value of device | | | | M |
+| Unit | Min value | Max value | Exception value | Resolution |
+| ° (Degree) | 0 | 360 | −360 | $\sim 5.5 \times 10^{-3}^{\circ}$ |
+| Example | 159.974 365° | | | |
+| Note | The angle formed by the north direction and the device base direction is measured clockwise, with 0° in the north direction, 180° in the south direction and 270° in the west direction. When a value cannot be input, a special value (−360) is used. | | | |
+
+| Tag name | FlightPitchDegree | | | |
+|-------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------|-----------------|-----------------------------------|
+| Description | | | | Support level (M/O) |
+| The pitch angle value of the device | | | | M |
+| Unit | Min value | Max value | Exception value | Resolution |
+| ° (Degree) | −20 | 20 | −360 | $\sim 610 \times 10^{-6}^{\circ}$ |
+| Example | −0.431531724° | | | |
+| Note | The angle formed by the device base direction (flex axis) and the horizontal plane is measured, with a positive value above and a negative value below. When a value cannot be input, a special value (−360) is used. | | | |
+
+| Tag name | FlightRollDegree | | | |
+|--------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------|-----------------|------------------------------------|
+| Description | | | | Support level (M/O) |
+| Roll angle value of the device | | | | M |
+| Unit | Min value | Max value | Exception value | Resolution |
+| ° (Degree) | −50 | 50 | −360 | $\sim 1525 \times 10^{-6}^{\circ}$ |
+| Example | −3.405 865 66° | | | |
+| Note | The angle formed by the horizontal plane and the horizontal plane of the fuselage from the cross-section of the device is set to a positive angle so that the right wing falls below the plane. When a value cannot be input, a special value (−360) is used. | | | |
+
+| Tag name | GimbalYawDegree | | | |
+|----------------------------------------------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------|-----------------|----------------------------------|
+| Description | | | | Support level (M/O) |
+| Sensor's relative yaw angle relative to device (Heading) value | | | | M |
+| Unit | Min value | Max value | Exception value | Resolution |
+| ° (Degree) | 0 | 360 | −360 | $\sim 84 \times 10^{-3}^{\circ}$ |
+| Example | 159.974 365° | | | |
+| Note | The value obtained by measuring the angle between the direction of the device and the direction of the sensor clockwise from the top of the device. When a value cannot be input, a special value (−360) is used. | | | |
+
+| Tag name | GimbalPitchDegree | | | |
+|-----------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------|-----------------|----------------------------------|
+| Description | | | | Support level (M/O) |
+| Sensor's relative pitch angle to device value | | | | M |
+| Unit | Min value | Max value | Exception value | Resolution |
+| ° (Degree) | −180 | 180 | −360 | $\sim 84 \times 10^{-3}^{\circ}$ |
+| Example | −0.431 531 724° | | | |
+| Note | The same direction as the device base is set to 0°, and the top has a positive value and the bottom has a negative value. When a value cannot be input, a special value (−360) is used. | | | |
+
+| Tag name | GimbalRollDegree | | | |
+|-------------------------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------|-----------------|----------------------------------|
+| Description | | | | Support level (M/O) |
+| Angle of relative roll relative to the device of the sensor | | | | M |
+| Unit | Min value | Max value | Exception value | Resolution |
+| ° (Degree) | −180 | 180 | −360 | $\sim 84 \times 10^{-3}^{\circ}$ |
+| Example | −3.405 865 66° | | | |
+| Note | Angle of rotation counterclockwise when looking at the sensor in front of the sensor (lens axis). When a value cannot be input, a special value (−360) is used. | | | |
+
+## 8.4 Spatial information metadata
+
+Spatial information metadata in the still image are specified in Table 7.
+
+**Table 7 – MCSI for spatial information**
+
+| Tag name | LatitudeOfImageCenter | | | |
+|----------------------------------------------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------|-----------------|----------------------------------|
+| Description | | | | Support level (M/O) |
+| Latitude of the ground point corresponding to the image centre point | | | | M |
+| Unit | Min value | Max value | Exception value | Resolution |
+| ° (Degree) | −90 | 90 | −360 | $\sim 42 \times 10^{-3}^{\circ}$ |
+| Example | −13.542 388 533 146 132° | | | |
+| Note | When the centre of the image does not pass through the surface of the earth, a special value (−360) is used in reference coordinate system, e.g., global navigation satellite system (GNSS), etc. | | | |
+
+| Tag name | LongitudeOfImageCenter | | | |
+|-----------------------------------------------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------|-----------|-----------------|----------------------------------|
+| Description | | | | Support level (M/O) |
+| Longitude of the ground point corresponding to the image centre point | | | | M |
+| Unit | Min value | Max value | Exception value | Resolution |
+| ° (Degree) | −180 | 180 | −360 | $\sim 84 \times 10^{-3}^{\circ}$ |
+| Example | −29.157 890 122 923 014° | | | |
+| Note | When the centre of the image does not pass through the surface of the earth, a special value (−360) is used in reference coordinate system, e.g., GNSS. | | | |
+
+| Tag name | LatitudeOfImageLT | | | |
+|------------------------------------------------------------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------|-----------------|----------------------------------|
+| Description | | | | Support level (M/O) |
+| The latitude of the ground point corresponding to the top left corner of the image | | | | M |
+| Unit | Min value | Max value | Exception value | Resolution |
+| ° (Degree) | −90 | 90 | −360 | $\sim 42 \times 10^{-3}^{\circ}$ |
+| Example | −29.157 890 122 923 014° | | | |
+| Note | When the upper left vertex centre of the image does not pass through the surface of the earth, a special value (−360) is used in reference coordinate system, e.g., GNSS. | | | |
+
+| Tag name | LongitudeOfImageLT | | | |
+|-------------------------------------------------------------------------------------|--------------------|-----------|-----------|---------------------|
+| Description | | | | Support level (M/O) |
+| The longitude of the ground point corresponding to the top left corner of the image | | | | M |
+| Unit | Min value | Max value | Exception | Resolution |
+
+| | | | value | |
+|------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----|-------|--------------------------------|
+| ° (Degree) | −180 | 180 | −360 | $\sim 84 \times 10^{-3}^\circ$ |
+| Example | −29.157 890 122 923 014° | | | |
+| Note | When the upper left vertex centre of the image does not pass through the surface of the earth, a special value (−360) is used in reference coordinate system, e.g., GNSS. | | | |
+
+| Tag name | LatitudeOfImageRT | | | |
+|-------------------------------------------------------------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------|-----------------|--------------------------------|
+| Description | | | | Support level (M/O) |
+| The latitude of the ground point corresponding to the top right corner of the image | | | | M |
+| Unit | Min value | Max value | Exception value | Resolution |
+| ° (Degree) | −90 | 90 | −360 | $\sim 42 \times 10^{-3}^\circ$ |
+| Example | −13.542 388 533 146 132° | | | |
+| Note | When the upper right vertex of the image does not pass through the surface of the earth, a special value (−360) is used in reference coordinate system, e.g., GNSS. | | | |
+
+| Tag name | LongitudeOfImageRT | | | |
+|--------------------------------------------------------------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------|-----------------|--------------------------------|
+| Description | | | | Support level (M/O) |
+| The longitude of the ground point corresponding to the top right corner of the image | | | | M |
+| Unit | Min value | Max value | Exception value | Resolution |
+| ° (Degree) | −180 | 180 | −360 | $\sim 84 \times 10^{-3}^\circ$ |
+| Example | −29.157 890 122 923 014° | | | |
+| Note | When the upper right vertex of the image does not pass through the surface of the earth, a special value (−360) is used in reference coordinate system, e.g., GNSS. | | | |
+
+| Tag name | LatitudeOfImageLB | | | |
+|--------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------|-----------------|--------------------------------|
+| Description | | | | Support level (M/O) |
+| The latitude of the ground point corresponding to the lower left vertex of the image | | | | M |
+| Unit | Min value | Max value | Exception value | Resolution |
+| ° (Degree) | −90 | 90 | −360 | $\sim 42 \times 10^{-3}^\circ$ |
+| Example | −13.542 388 533 146 132° | | | |
+| Note | When the lower left vertex of the image does not pass through the surface of the earth, a special value (−360) is used in reference coordinate system, e.g., GNSS. | | | |
+
+| Tag name | LongitudeOfImageLB | | | |
+|---------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------|-----------------|----------------------------------|
+| Description | | | | Support level (M/O) |
+| The longitude of the ground point corresponding to the lower left vertex of the image | | | | M |
+| Unit | Min value | Max value | Exception value | Resolution |
+| ° (Degree) | −180 | 180 | −360 | $\sim 84 \times 10^{-3}^{\circ}$ |
+| Example | −29.157 890 122 923 014° | | | |
+| Note | When the lower left vertex of the image does not pass through the surface of the earth, a special value (−360) is used in reference coordinate system, e.g., GNSS. | | | |
+
+| Tag name | LatitudeOfImageRB | | | |
+|---------------------------------------------------------------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------|-----------------|----------------------------------|
+| Description | | | | Support level (M/O) |
+| The latitude of the ground point corresponding to the lower right vertex of the image | | | | M |
+| Unit | Min value | Max value | Exception value | Resolution |
+| ° (Degree) | −90 | 90 | −360 | $\sim 42 \times 10^{-3}^{\circ}$ |
+| Example | −13.542 388 533 146 132° | | | |
+| Note | When the lower right vertex of the image does not pass through the surface of the earth, a special value (−360) is used in reference coordinate system, e.g., GNSS. | | | |
+
+| Tag name | LongitudeOfImageRB | | | |
+|----------------------------------------------------------------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------|-----------------|----------------------------------|
+| Description | | | | Support level(M/O) |
+| The longitude of the ground point corresponding to the lower right vertex of the image | | | | M |
+| Unit | Min value | Max value | Exception value | Resolution |
+| ° (Degree) | −180 | 180 | −360 | $\sim 84 \times 10^{-3}^{\circ}$ |
+| Example | −29.157 890 122 923 014° | | | |
+| Note | When the lower right vertex of the image does not pass through the surface of the earth, a special value (−360) is used in reference coordinate system, e.g., GNSS. | | | |
+
+## 8.5 Device information metadata
+
+Device information, such as device and task information, is specified in Table 8.
+
+**Table 8 – MCSI for device information**
+
+| Tag name | Mission | | | |
+|------------------------------------------------|------------------------------------------------------------------------------------------------------------------------------|-----------|-----------------|---------------------|
+| Description | | | | Support level (M/O) |
+| Information to identify performed device tasks | | | | O |
+| Unit | Min value | Max value | Exception value | Resolution |
+| – | 4 | 127 | N/A | – |
+| Example | | | | |
+| Note | Record it as a string with a maximum of 127 characters. The internal expression method expresses device mission performance. | | | |
+
+| Tag name | PlatformTailNumber | | | |
+|----------------------|-------------------------------------------------------------------------|-----------|-----------------|---------------------|
+| Description | | | | Support level (M/O) |
+| Device serial number | | | | O |
+| Unit | Min value | Max value | Exception value | Resolution |
+| – | 4 | 127 | N/A | – |
+| Example | | | | |
+| Note | Record it as a string with a maximum of 127 characters for each device. | | | |
+
+| Tag name | PlatformDesignation | | | |
+|-------------------|------------------------------------------------------------------------|-----------|-----------------|---------------------|
+| Description | | | | Support level (M/O) |
+| Device model name | | | | O |
+| Unit | Min value | Max value | Exception value | Resolution |
+| – | 4 | 127 | N/A | – |
+| Example | | | | |
+| Note | Record it as a string with a maximum of 127 characters for model name. | | | |
+
+# Appendix I
+
+## **Use case for a building defect monitoring service using autonomous mobile Internet of things devices**
+
+(This appendix does not form an integral part of this Recommendation.)
+
+This appendix explains an example of a use case that informs on the location of building defects in three dimensions to a user using IoT sensing devices that are capable of moving about or flying while adjusting angles. In the case of a model that contains 3D spatial information of a structure, generated using an application such as building information modelling (BIM), emergency measures can be taken by identifying in real time the risks to the building structure (falling, shearing, cracking, etc.) or abnormal situations in images obtained from IoT sensing devices.
+
+The IoT sensing metadata standard is necessary to guarantee interoperability in IoT image or video-based applications, and provide value added IoT services through the IoT sensing metadata standard by reducing development time and human costs.
+
+The building defect monitoring service is shown in Figure I.1 and described as follows.
+
+Step 1 – IoT devices acquire sensing information, e.g., mission, image, video, space and time, for the building defect monitoring service.
+
+Step 2 – The IoT metadata system converts acquired mission information, space information and time information into standard metadata, which yields additional information and applies it as metadata for still images or videos.
+
+Step 3 – The IoT metadata system sends still images or videos with metadata to the building defect detection system and the building defect detection system transmits data to the safety management system when detecting defects in the building.
+
+Step 4 – The safety management system detects the defect using BIM from the image metadata from the surface of the building and the location of the building.
+
+Step 5 – The safety management system reports the actual position of defects in the building to the user (administrator) for final action.
+
+
+
+Y.4604(23)
+
+Figure I.1: Use case of building defect monitoring service using autonomous mobile IoT devices. The diagram is divided into four main sections: IoT devices, Network, Service, and User. In the IoT devices section, (1) Data acquisition shows a robot, car, and drone sensing a building. (2) Standard metadata shows an IoT metadata system. In the Network section, data is transmitted. In the Service section, (3) Defect detection shows data entering a Building defect detection system, which feeds into a Safety management system. (4) Defect position mapping shows a BIM model with a defect location. (5) Report shows the Safety management system sending a report to an Administrator in the User section.
+
+**Figure I.1 – Use case of building defect monitoring service using autonomous mobile IoT devices**
+
+On the IoT device side of Figure I.1, autonomous mobile IoT conceptual processes may experience additional problems such as:
+
+- differences in specification (units, resolution, criteria);
+- lack of common metadata on image sensing information among IoT sensor devices;
+- dedicated metadata depending on manufacturer.
+
+As shown in Figure I.2, to resolve these types of problems, it is necessary to specify the minimum metadata that can be commonly provided in IoT camera sensors. These minimum metadata specifications can be used as a foundational image metadata for IoT camera-based services, such as autonomous robot services, building management service and AR/VR services.
+
+
+
+Y.4604(23)
+
+Figure I.2: Conceptual process for sensing metadata-based service. The process starts with 'Autonomous mobile IoT devices with camera' (robot, car, drone) sending a 'Signal (Image, video, etc.)' to a 'Sensing type' box containing EO, MSI, and IR. This leads to 'Data' being sent to an 'IoT metadata system (for standardization)' box containing Time, Sensor, Location position, Spatial, and Device. Finally, 'Metadata' is sent to a 'Service' box containing Autonomous robot service, Building management service, and AR/VR service.
+
+**Figure I.2 – Conceptual process for sensing metadata-based service**
+
+Table I.1 summarizes major differences between traditional digital camera devices and AMIDs. Generally, existing digital camera devices support full-performance capabilities and high resolution,
+
+so the metadata is complex and heavy. However, AMIDs are resource limited and not interchangeable among IoT camera sensors. AMID metadata do not need to cover complex metadata. An AMID is therefore characterized as basic, minimum and lightweight compared to a traditional digital camera device.
+
+**Table I.1 – Difference between typical digital camera devices and AMIDs**
+
+| Metadata | Digital camera device | AMIDs with camera | Description |
+|----------------------------------|-------------------------------------------------------------------|-----------------------------------|--------------------|
+| Time information | Supported | Supported | EXIF, etc. |
+| Sensor specification information | Supported | Supported | EXIF, etc. |
+| Field of view | Calculation as a combination from different sensor specifications | Direct input of calculated values | |
+| Image information | Supported | Supported | EXIF, etc. |
+| Image spatial information | Not supported | Supported | |
+| Location/Position information | Supported in part | Supported | |
+| Location of attachment | Supported | Supported | EXIF, etc. |
+| Position of attachment | Not supported | Supported | |
+| Location of sensor | Not supported | Supported | |
+| Position of sensor | Not supported | Supported | |
+| Device information | Not supported | Supported | |
+
+# Bibliography
+
+- [b-ITU-T Y.1901] Recommendation ITU-T Y.1901 (2009), *Requirements for the support of IPTV services*.
+- [b-ITU-T Y.2091] Recommendation ITU-T Y.2091 (2011), *Terms and definitions for next generation networks*.
+- [b-ITU-T Y.4000] Recommendation ITU-T Y.4000/Y.2060 (2012), *Overview of the Internet of things*.
+- [b-ITU-T Y.4900] Recommendation ITU-T Y.4900/L.1600 (2016), *Overview of key performance indicators in smart sustainable cities*.
+- [b-ISO 19130-1] International Standard ISO 19130-1:2018, *Geographic information – Imagery sensor models for geopositioning – Part 1: Fundamentals*.
+- [b-Exif] Hedley, J. (2023). *Exifinfo.org: An online tool to analyze and display the metadata in images and other media files*. Available [viewed 2023-10-07] at:
+
+
+
+
+
+## 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 |
+| 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 | 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 |
\ No newline at end of file
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new file mode 100644
index 0000000000000000000000000000000000000000..7185162895f86acda3352c5b6112156758a01ba1
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@@ -0,0 +1,486 @@
+
+
+# Recommendation
+
+# **ITU-T Y.4909 (03/2023)**
+
+SERIES Y: Global information infrastructure, Internet protocol aspects, next-generation networks, Internet of Things and smart cities
+
+Internet of things and smart cities and communities –
+Evaluation and assessment
+
+---
+
+## **Assessment framework of Internet of things sensing quality**
+
+## ITU-T Y-SERIES RECOMMENDATIONS
+
+## GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS, NEXT-GENERATION NETWORKS, INTERNET OF THINGS AND SMART CITIES
+
+## GLOBAL INFORMATION INFRASTRUCTURE
+
+| | |
+|-------------------------------------------|-------------|
+| General | Y.100–Y.199 |
+| Services, applications and middleware | Y.200–Y.299 |
+| Network aspects | Y.300–Y.399 |
+| Interfaces and protocols | Y.400–Y.499 |
+| Numbering, addressing and naming | Y.500–Y.599 |
+| Operation, administration and maintenance | Y.600–Y.699 |
+| Security | Y.700–Y.799 |
+| Performances | Y.800–Y.899 |
+
+## INTERNET PROTOCOL ASPECTS
+
+| | |
+|--------------------------------------------------------------------|---------------|
+| General | Y.1000–Y.1099 |
+| Services and applications | Y.1100–Y.1199 |
+| Architecture, access, network capabilities and resource management | Y.1200–Y.1299 |
+| Transport | Y.1300–Y.1399 |
+| Interworking | Y.1400–Y.1499 |
+| Quality of service and network performance | Y.1500–Y.1599 |
+| Signalling | Y.1600–Y.1699 |
+| Operation, administration and maintenance | Y.1700–Y.1799 |
+| Charging | Y.1800–Y.1899 |
+| IPTV over NGN | Y.1900–Y.1999 |
+
+## NEXT GENERATION NETWORKS
+
+| | |
+|-------------------------------------------------------------------|---------------|
+| Frameworks and functional architecture models | Y.2000–Y.2099 |
+| Quality of Service and performance | Y.2100–Y.2199 |
+| Service aspects: Service capabilities and service architecture | Y.2200–Y.2249 |
+| Service aspects: Interoperability of services and networks in NGN | Y.2250–Y.2299 |
+| Enhancements to NGN | Y.2300–Y.2399 |
+| Network management | Y.2400–Y.2499 |
+| Computing power networks | Y.2500–Y.2599 |
+| Packet-based Networks | Y.2600–Y.2699 |
+| Security | Y.2700–Y.2799 |
+| Generalized mobility | Y.2800–Y.2899 |
+| Carrier grade open environment | Y.2900–Y.2999 |
+
+## FUTURE NETWORKS
+
+Y.3000–Y.3499
+
+### CLOUD COMPUTING
+
+Y.3500–Y.3599
+
+### BIG DATA
+
+Y.3600–Y.3799
+
+### QUANTUM KEY DISTRIBUTION NETWORKS
+
+Y.3800–Y.3999
+
+### INTERNET OF THINGS AND SMART CITIES AND COMMUNITIES
+
+| | |
+|---------------------------------------------------------|----------------------|
+| General | Y.4000–Y.4049 |
+| Definitions and terminologies | Y.4050–Y.4099 |
+| Requirements and use cases | Y.4100–Y.4249 |
+| Infrastructure, connectivity and networks | Y.4250–Y.4399 |
+| Frameworks, architectures and protocols | Y.4400–Y.4549 |
+| Services, applications, computation and data processing | Y.4550–Y.4699 |
+| Management, control and performance | Y.4700–Y.4799 |
+| Identification and security | Y.4800–Y.4899 |
+| Evaluation and assessment | Y.4900–Y.4999 |
+
+For further details, please refer to the list of ITU-T Recommendations.
+
+# Recommendation ITU-T Y.4909
+
+# Assessment framework of Internet of things sensing quality
+
+## Summary
+
+Internet of things (IoT) systems are implemented by relevant stakeholders to increase the effectiveness, efficiency and the quality of sensing services. All IoT systems depend on the acquisition and use of sensing information. Sensing quality directly impacts the quality of service provided by the IoT systems. The sensing quality assessment framework of IoT systems provides a unified framework for both developers and users to evaluate sensing quality in IoT systems.
+
+Recommendation ITU-T Y.4909 specifies an assessment framework of IoT sensing quality.
+
+## History
+
+| Edition | Recommendation | Approval | Study Group | Unique ID* |
+|---------|----------------|------------|-------------|---------------------------------------------------------------------------|
+| 1.0 | ITU-T Y.4909 | 2023-03-28 | 20 | 11.1002/1000/15488 |
+
+## Keywords
+
+Assessment framework, IoT system, sensing quality, sensing service.
+
+---
+
+\* To access the Recommendation, type the URL in the address field of your web browser, followed by the Recommendation's unique ID. For example, .
+
+## 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 .
+
+© ITU 2023
+
+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 | Conventions ..... | 2 |
+| 6 | Sensing services in the IoT ..... | 2 |
+| | 6.1 Introduction to sensing services in the IoT ..... | 3 |
+| | 6.2 The sensing quality assessment framework and its benefits for sensing
service of IoT systems..... | 4 |
+| 7 | Sensing quality assessment factors of IoT systems..... | 5 |
+| | 7.1 Coverage quality ..... | 5 |
+| | 7.2 Data quality ..... | 5 |
+| | 7.3 Response performance ..... | 5 |
+| | 7.4 Security ..... | 6 |
+| | 7.5 Ease of use ..... | 6 |
+| | 7.6 System openness..... | 6 |
+| 8 | Sensing quality assessment framework of IoT systems..... | 6 |
+| | 8.1 Coverage quality ..... | 7 |
+| | 8.2 Data quality ..... | 7 |
+| | 8.3 Response performance ..... | 7 |
+| | 8.4 Security ..... | 8 |
+| | 8.5 Ease of use ..... | 8 |
+| | 8.6 System openness..... | 9 |
+
+
+
+# Recommendation ITU-T Y.4909
+
+## Assessment framework of Internet of things sensing quality
+
+# 1 Scope
+
+This Recommendation specifies an assessment framework of Internet of things (IoT) sensing quality.
+
+The scope of this Recommendation includes:
+
+- Sensing services in the IoT,
+- Sensing quality assessment factors of IoT systems, and
+- Sensing quality assessment framework of IoT systems.
+
+NOTE – Policy and regulation are out of the scope of this Recommendation.
+
+# 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.
+
+None.
+
+# 3 Definitions
+
+### 3.1 Terms defined elsewhere
+
+This Recommendation uses the following terms defined elsewhere:
+
+**3.1.1 application** [b-ITU-T Y.2091]: A structured set of capabilities, which provide value-added functionality supported by one or more services, which may be supported by an API interface.
+
+**3.1.2 device** [b-ITU-T Y.4000]: With regard to the Internet of things, this is a piece of equipment with the mandatory capabilities of communication and the optional capabilities of sensing, actuation, data capture, data storage and data processing.
+
+**3.1.3 Internet of things (IoT)** [b-ITU-T Y.4000]: A global infrastructure for the information society, enabling advanced services by interconnecting (physical and virtual) things based on existing and evolving interoperable information and communication technologies.
+
+NOTE 1 – Through the exploitation of identification, data capture, processing and communication capabilities, the IoT makes full use of things to offer services to all kinds of applications, whilst ensuring that security requirements are fulfilled.
+
+NOTE 2 – From a broader perspective, the IoT can be perceived as a vision with technological and societal implications.
+
+**3.1.4 sensor** [b-ITU-T Y.4105]: An electronic device that senses a physical condition or chemical compound and delivers an electronic signal proportional to the observed characteristic.
+
+### 3.2 Terms defined in this Recommendation
+
+This Recommendation defines the following terms:
+
+**3.2.1 sensing services:** A collection of services including device service, security service, data service, management service, monitoring service, etc.
+
+**3.2.2 sensing service provider:** An organization, which provides organization-oriented sensing services to sensing service organization consumers and/or individual-oriented sensing services to sensing service individual consumers.
+
+**3.2.3 sensing solution provider:** An organization, which realizes required software and hardware for a sensing service provider, sensing service organization consumer and/or a sensing service individual consumer, in order to implement sensing services.
+
+## **4 Abbreviations and acronyms**
+
+This Recommendation uses the following abbreviations and acronyms:
+
+| | |
+|-------|------------------------------------------------------------|
+| ALCOA | Attributable, Legible, Contemporaneous, Original, Accurate |
+| FE | Functional Entity |
+| IoT | Internet of Things |
+| PII | Personal Identifiable Information |
+
+# **5 Conventions**
+
+In this Recommendation:
+
+The keywords "is required" indicate a requirement which must be strictly followed and from which no deviation is permitted if conformance to this document is to be claimed.
+
+The keyword "may" and "is recommended" indicates an optional requirement which is permissible, without implying any sense of being recommended. These terms are not intended to imply that the vendor's implementation must provide the option and the feature can be optionally enabled by the network operator/service provider. Rather, it means the vendor may optionally provide the feature and still claim conformance with the specification.
+
+# **6 Sensing services in the IoT**
+
+Sensing services are important to Internet of things (IoT) systems. Sensing services are the fundamental basis of IoT system operation and the provision of services. In many fields, sensing services are the essential capability of IoT systems such as for example, environmental monitoring, traffic monitoring, e-health care, climate monitoring, etc. Sensing service is the basis of various services provided by IoT systems, including among others information collection, information management, and sensing quality assessment.
+
+## 6.1 Introduction to sensing services in the IoT
+
+
+
+Environment management system users
+
+Environment management system
+
+Sensing devices
+
+IoT network
+
+Environment management platform
+
+Sensing service
+
+Data storage service
+
+Smart transportation system
+
+Smart water system
+
+Smart gas system
+
+Smart factory system
+
+...
+
+Y.4909(23)
+
+Interface
+
+Communication
+
+Figure 1: Sensing services of an environment management system. The diagram illustrates the architecture of an environment management system. At the top, 'Environment management system users' are connected via a double-headed arrow (Interface) to the 'Environment management system' box. Inside this box, 'Sensing devices' (represented by icons for temperature, humidity, gas, and noise) are connected via a dashed line (Communication) to the 'IoT network'. The 'IoT network' is represented by a stack of blue cylinders. The 'IoT network' is connected via a double-headed arrow (Interface) to the 'Environment management platform' box. Inside this platform, there are two sub-boxes: 'Sensing service' and 'Data storage service'. The 'Environment management platform' is connected via double-headed arrows (Interface) to 'Smart transportation system', 'Smart water system', 'Smart gas system', 'Smart factory system', and an ellipsis (...). A legend at the bottom left indicates that a double-headed arrow represents an 'Interface' and a dashed line represents 'Communication'. The reference 'Y.4909(23)' is located at the bottom right of the diagram.
+
+**Figure 1 – Sensing services of an environment management system**
+
+Figure 1 shows a typical example of sensing services in an environment management system which includes the process, function and users of sensing services. The sensing devices can collect various environmental data, such as temperature, humidity, gas concentration, noise, etc., and upload them to the environment management platform through the IoT network. Inside the IoT system, the sensing service in the platform can evaluate the sensing quality and store data. Outside the IoT system, the platform can provide sensing services to environment management system users through interfaces to help users understand the environment sensing result, as well as sensing services to other systems, such as smart transportation systems, smart water systems, smart gas systems and smart factory systems.
+
+## 6.2 The sensing quality assessment framework and its benefits for sensing service of IoT systems
+
+
+
+Figure 2 – Sensing service framework of IoT system. The diagram illustrates a multi-layered architecture. At the top is the 'Application layer' containing 'IoT sensing applications'. Below this is the 'Service support and application support layer', which is the core of the framework. This layer includes a 'Sensing quality optimization strategy FE' (containing 'Intelligent analysis FE' and 'Strategy Recommendation FE'), a 'Low sensing quality alert FE', and three assessment Functional Entities (FEs): 'Coverage quality assessment FE' (with 'Time coverage assessment module' and 'Space coverage assessment module'), 'Data quality assessment FE' (with 'Quality assessment for data pre-processing module' and 'Quality assessment for raw data module'), and 'Response performance assessment FE' (with 'Response time assessment module' and 'Response rate assessment module'). Below the service support layer are the 'Network layer' and the 'Device layer'. On the left, a vertical dashed box labeled 'Management capabilities' spans the application and service support layers. On the right, a vertical dashed box labeled 'Security capabilities' contains 'Sensing data security protection FE' and 'Personal information security protection FE'. The reference 'Y.4909(23)' is at the bottom right.
+
+**Figure 2 – Sensing service framework of IoT system**
+
+In Figure 2, the IoT system contains three major functions: sensing quality assessment, low sensing quality alert and sensing quality optimization. Sensing quality assessment includes coverage quality assessment (time coverage and space coverage), data quality assessment (raw data, pre-processed data, and intelligent processed data) and response performance assessment (response time and response rate) which are evaluated by the coverage quality assessment functional entity (FE), data quality assessment FE and response performance assessment FE. Then, the sensing quality assessment result will be passed to the low sensing quality alert FE. If the sensing quality does not meet the requirements of the system, the result will be passed to the sensing quality optimization strategy FE, so as to analyse the causes of low sensing quality by the intelligent analysis FE and develop the sensing quality optimization strategy by the strategy recommendation FE.
+
+Sensing quality is an important factor affecting IoT applications. The acquisition and use of sensing information is a basis of IoT services provided by many IoT systems, and thus their services are directly affected by the sensing quality.
+
+A sensing quality assessment framework is required by considering many factors such as coverage, data, response time, etc., in order to help the users of IoT systems. This performance assessment framework will identify the requirements of IoT systems and will in turn help in providing solutions.
+
+The sensing quality assessment framework of IoT has the following benefits:
+
+- The sensing quality assessment framework can improve the performance of the IoT systems and applications;
+
+- The sensing assessment framework can assist in selecting an IoT systems with better sensing quality.
+
+# **7 Sensing quality assessment factors of IoT systems**
+
+The IoT sensing quality assessment framework includes three major parts: coverage quality, data quality, and response time. The indicators of each part are closely related to the sensing quality evaluation results.
+
+## **7.1 Coverage quality**
+
+Coverage quality is divided into time coverage quality and space coverage quality. The time coverage quality focuses on measuring time-sensitive sensing tasks, which indicates whether the sensing node has collected a certain amount of data during the task time.
+
+For example, in order to monitor urban traffic congestion during peak hours, sensors such as location and speed need to upload data at a certain time during the peak hour period (for every single sensor).
+
+The space coverage quality focuses on sensing tasks that are sensitive to space coverage. It indicates whether the sensing node can cover the sensing range required by the sensing task.
+
+For example, the percentage of the manhole covers that can be captured by the cameras in the city can be calculated with the accounts for the total number of urban manhole covers (for the sensor group).
+
+The quality of coverage indicates whether the sensing nodes in the IoT systems can meet the basic criteria for sensing task completion.
+
+## **7.2 Data quality**
+
+The IoT systems have three types of data: raw data, pre-processed data, and intelligent processed data. The quality of data directly affects sensing quality. Data quality evaluation indicators include: data validity, reliability, completeness, accuracy, timeliness, consistency, redundancy, etc. The data assessment services include:
+
+- Raw data assessment service: The raw data is divided into static data and dynamic data according to the different sensing devices. Raw data assessment services are based on verifying the integrity, validity, consistency, etc. of sensing information and provide the assessment results.
+- Pre-processed data assessment service: Pre-processed data assessment services are based on data cleaning, data fusion, data unification of different data sources, identification of valuable data and evaluating data quality, thus providing assessment results.
+- Intelligent processed data assessment service: According to the needs of different tasks and the situation of data preprocessing, intelligent data processing can provide artificial intelligence-based sensing quality management service such as data enhancement, key information extraction, and removal of redundant data, etc. Sensing services will evaluate the sensing quality of intelligently processed data and provide the assessment results.
+
+## **7.3 Response performance**
+
+The response time is determined by the performance of the sensing system and the network state, etc.
+
+The response rate is determined by the number of sensing devices, device idle rate and other factors.
+
+### 7.4 Security
+
+As an IoT sensing system can perform different sensing tasks, involving multi-user access and data reception of multi-sensing nodes, etc., a large amount of personal identifiable information (PII) and sensing data are stored in the system, and therefore security protection services for relevant data and information are required.
+
+## 7.5 Ease of use
+
+Ease of use is a reflection of the applicability, functionality and effectiveness of the interoperability between an IoT sensing system and other third-party systems. Ease of use can ensure that IoT sensing system users can quickly learn how to deliver sensing tasks, view the execution process and check the results. The IoT sensing system is recommended to be easy to use in order to improve operational efficiency.
+
+Ease of use includes but is not limited to easy to understand, easy to learn, and easy to operate.
+
+## 7.6 System openness
+
+IoT sensing system needs to consider the requirements of existing users, it also needs to consider the scalability, so as to better meet the expansion of future applications of IoT sensing systems.
+
+System openness includes the potential information interaction mechanism and external interface guarantee. Potential information interaction mechanism can support the expansion of information interaction modes, such as the cooperation of different types of sensing devices, supporting different communication protocols, and the information interaction between an IoT sensing system and different applications, etc. External interface guarantee can provide diverse interfaces to interact with other systems, such as IoT sensing systems, software service systems, etc.
+
+# 8 Sensing quality assessment framework of IoT systems
+
+The sensing quality assessment framework of IoT systems includes six factors: coverage quality, data quality, response performance, security, ease of use and system openness of IoT systems. These factors together determine whether the IoT system can provide users with sensing services that meet the requirements of sensing tasks.
+
+Figure 3 shows the sensing quality assessment framework of IoT systems.
+
+
+
+The diagram illustrates the Sensing quality assessment framework of IoT sensing systems. It features a central horizontal bar labeled "Sensing quality assessment framework of IoT sensing systems". Below this bar, six factors are arranged in a grid-like structure: "Ease of use" (leftmost vertical bar), "Coverage quality" (top-left square), "Data quality" (top-middle square), "Response performance" (top-right square), "Security" (bottom horizontal bar), and "System openness" (rightmost vertical bar). The factors "Coverage quality", "Data quality", and "Response performance" are positioned above the "Security" bar, while "Ease of use" and "System openness" are positioned to the left and right of the "Security" bar respectively.
+
+Y.4909(23)
+
+Sensing quality assessment framework of IoT sensing systems diagram
+
+**Figure 3 – Sensing quality assessment framework of IoT systems**
+
+## 8.1 Coverage quality
+
+Coverage quality includes two parameters (see Table 1): time coverage quality and space coverage quality. Time coverage quality indicates whether the time period of sensing data collection meets the task requirements, and space coverage quality indicates whether the spatial distribution of collected sensing data meets the task requirements.
+
+**Table 1 – Parameters of coverage quality**
+
+| Parameter | Details |
+|------------------------|---------------------------------------------------------------|
+| Time coverage quality | The interval of sensing grid area be covered twice in a row. |
+| Space coverage quality | Proportion of effective sensing area to overall sensing area. |
+
+## 8.2 Data quality
+
+Data quality includes seven parameters (see Table 2): validity, reliability, completion, malicious data, redundant data, timeliness and consistency. These parameters together determine whether the collected sensing data is available for sensing task and whether it can be used as the basis for subsequent analysis.
+
+**Table 2 – Parameters of data quality**
+
+| Parameter | Details |
+|----------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Validity | Whether the data is valid needs to be judged whether the data meets the requirements of sensing task. The methods of judgment include but are not limited to: whether the data reporting time is within the specified time, whether the data is within the specified interval, whether the data type is the specified type, and the data format is correct. |
+| Reliability | Data reliability requirements meet ALCOA principles: attributable, legible, contemporaneous, original or true copy, accurate. |
+| Completion | Data completion refers to the logical consistency, correctness, validity and compatibility of data. |
+| Malicious data | There may be malicious sensing nodes in the sensing task, and this part of data needs to be evaluated and removed.
NOTE – Malicious data may be correct, but not derived from the required sensing node. |
+| Redundant data | Duplicate and invalid data. |
+| Timeliness | Valid duration of data. |
+| Consistency | The parameter of data consistency includes missing updates, undetermined dependencies, inconsistent analysis and processing. |
+
+### 8.3 Response performance
+
+Response performance includes two parameters (see Table 3): response time and response rate. The response time indicates the efficiency of the IoT sensing system to complete a sensing task, and the response rate indicates how many sensing nodes of the IoT sensing system can provide for a sensing task.
+
+**Table 3 – Parameters of response performance**
+
+| Parameter | Details |
+|---------------|------------------------------------------------------------------------------|
+| Response time | The time from the initiation of the task to the completion of the task. |
+| Response rate | The ratio of the tasks with sensing nodes response to total number of tasks. |
+
+## 8.4 Security
+
+Security includes two parameters (see Table 4): sensing data security and personal identifiable information (PII) security. The security factor indicates the capability and level of data and information security protection provided by IoT sensing system.
+
+NOTE – PII in this context is defined as a user's username and password.
+
+**Table 4 – Parameters of security**
+
+| Parameter | Details |
+|-----------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Sensing data security | The degree of security for sensing data storage and processing in the IoT perception system, including prevention of malicious data attacks, data theft, data insecurity, etc. |
+| PII security | The degree of security for PII registration, management, and deletion in the IoT sensing system, including prevention of malicious data attacks, data theft, data insecurity, etc. |
+
+## 8.5 Ease of use
+
+Ease of use includes three parameters (see Table 5): easy to understand, easy to learn and easy to operate. The ease of use factor allows users to better use IoT sensing systems, including, but not limited to, initiating and completing a sensing task, and understanding the results.
+
+**Table 5 – Parameters of ease of use**
+
+| Parameter | Details |
+|--------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Easy to understand | How easy it is for users to recognize the structure, function, logic, concept, application scope, interface and other content of the IoT sensing system. All documents formed in the system development process are required to have a concise language, consistent, easy to understand, and unambiguous sentences, including: 1) function names, icons, prompt information, etc. should be straightforward, clear, without ambiguity, and easy to understand; 2) the user manual fully considers the acceptance level of ordinary users, the language is straightforward, the description is detailed, and the logic is clear; 3) try to avoid professional terms, etc. |
+| Easy to learn | How easy it is for users to learn software applications (operation control, input, output). This feature requires: 1) detailed user documentation, clear structure and accurate language; 2) intuitive operation interface information, easy for users to find the required function menu; 3) prevent the stacking of irrelevant information; 4) The prompt information for operation or handling errors is clear and sufficient; the |
+
+**Table 5 – Parameters of ease of use**
+
+| Parameter | Details |
+|-----------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| | user manual is detailed and clear, allowing users to easily get help. |
+| Easy to operate | How easy it is for users to operate and run the IoT sensing system. It requires that the software has a friendly human-machine interface, a scientific and reasonable interface design, and a simplified operation process. |
+
+## 8.6 System openness
+
+System openness includes two parameters (see Table 6): number and types of information interaction mechanism and number and types of external interfaces. System openness reflects the diversity and expandability of IoT services.
+
+**Table 6 – Parameters of system openness**
+
+| Parameter | Details |
+|-------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Number and types of information interaction mechanism | The number and types of information interaction mechanism reflects the diversity and expandability of IoT services.
NOTE 1 – example of information interaction: data protocols, communication protocols. |
+| Number and types of external interfaces | The number and types of external interfaces reflects the diversity and expandability of IoT services.
NOTE 2 – example of interfaces: platform interfaces, system interfaces, device interfaces. |
+
+# Bibliography
+
+- [b-ITU-T Y.2091] Recommendation ITU-T Y.2091 (2011), *Terms and definitions for next generation networks*.
+- [b-ITU-T Y.4000] Recommendation ITU-T Y.4000/Y.2060 (2012), *Overview of the Internet of things*.
+- [b-ITU-T Y.4105] Recommendation ITU-T Y.4105/Y.2221 (2010), *Requirements for support of ubiquitous sensor network (USN) applications and services in the NGN environment*.
+
+
+
+## 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 |
+| 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 | 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 |
\ No newline at end of file
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+
+
+# Recommendation
+
+## **ITU-T Y.4911 (09/2025)**
+
+SERIES Y: Global information infrastructure, Internet protocol aspects, next-generation networks, Internet of Things and smart cities
+
+Internet of things and smart cities and communities –
+Evaluation and assessment
+
+---
+
+**Key performance indicators of information and communication technology (ICT)-based data support capabilities for urban flood disaster prevention and mitigation**
+
+## ITU-T Y-SERIES RECOMMENDATIONS
+
+### Global information infrastructure, Internet protocol aspects, next-generation networks, Internet of Things and smart cities
+
+| | |
+|---------------------------------------------------------|----------------------|
+| GLOBAL INFORMATION INFRASTRUCTURE | Y.100-Y.999 |
+| INTERNET PROTOCOL ASPECTS | Y.1000-Y.1999 |
+| NEXT GENERATION NETWORKS | Y.2000-Y.2999 |
+| FUTURE NETWORKS | Y.3000-Y.3499 |
+| CLOUD COMPUTING | Y.3500-Y.3599 |
+| BIG DATA | Y.3600-Y.3799 |
+| QUANTUM KEY DISTRIBUTION NETWORKS | Y.3800-Y.3999 |
+| INTERNET OF THINGS AND SMART CITIES AND COMMUNITIES | Y.4000-Y.4999 |
+| General | Y.4000-Y.4049 |
+| Definitions and terminologies | Y.4050-Y.4099 |
+| Requirements and use cases | Y.4100-Y.4249 |
+| Infrastructure, connectivity and networks | Y.4250-Y.4399 |
+| Frameworks, architectures and protocols | Y.4400-Y.4549 |
+| Services, applications, computation and data processing | Y.4550-Y.4699 |
+| Management, control and performance | Y.4700-Y.4799 |
+| Identification and security | Y.4800-Y.4899 |
+| Evaluation and assessment | Y.4900-Y.4999 |
+
+*For further details, please refer to the list of ITU-T Recommendations.*
+
+# Recommendation ITU-T Y.4911
+
+## **Key performance indicators of information and communication technology (ICT)-based data support capabilities for urban flood disaster prevention and mitigation**
+
+## **Summary**
+
+Flood disaster is a critical issue influencing the safety of a city. There are many kinds of data support for flood disaster prevention and mitigation; however, a comprehensive assessment of data support capabilities would be highly beneficial for cities.
+
+Recommendation ITU-T Y.4911 specifies a set of key performance indicators to assess information and communication technology (ICT)-based data support capabilities for urban flood disaster prevention and mitigation.
+
+## **History\***
+
+| Edition | Recommendation | Approval | Study Group | Unique ID |
+|---------|----------------|------------|-------------|--------------------|
+| 1.0 | ITU-T Y.4911 | 2025-09-23 | 20 | 11.1002/1000/16209 |
+
+## **Keywords**
+
+Flood, information and communication technologies, key performance indicators.
+
+---
+
+\* To access the Recommendation, type the URL 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 .
+
+© 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 | 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 | Conventions ..... | 2 |
+| 6 | Overview..... | 2 |
+| | 6.1 Urban flood disaster prevention and mitigation ..... | 2 |
+| | 6.2 General principles for selecting KPIs..... | 3 |
+| 7 | Structure of KPIs ..... | 4 |
+| 8 | KPIs: Dimension of flood-related data collection ..... | 7 |
+| | 8.1 Rationality of sensor layout..... | 7 |
+| | 8.2 Fulfilment of daily decision-making ..... | 8 |
+| | 8.3 Fulfilment of emergency decision-making..... | 9 |
+| 9 | KPIs: Dimension of flood-related data transmission..... | 10 |
+| | 9.1 Daily reliability..... | 10 |
+| | 9.2 Emergency reliability ..... | 11 |
+| 10 | KPIs: Dimension of flood-related data processing..... | 13 |
+| | 10.1 Fulfilment of daily decision-making ..... | 14 |
+| | 10.2 Fulfilment of emergency decision-making..... | 15 |
+| 11 | KPIs: Dimension of flood-related applications ..... | 16 |
+| | 11.1 Functions ..... | 16 |
+| | 11.2 Performance..... | 17 |
+| | 11.3 Analysis and data mining capability..... | 17 |
+| | 11.4 Simulation capability ..... | 18 |
+| | 11.5 Prediction capability ..... | 19 |
+| | 11.6 Visualization capability ..... | 19 |
+| | Appendix I – Use case for KPIs of ICT-based data support capabilities for urban flood
disaster prevention and mitigation..... | 21 |
+| | I.1 Use case of KPIs: Dimension of flood-related data collection..... | 21 |
+| | I.2 Use case of KPIs: Dimension of flood-related data transmission ..... | 22 |
+| | I.3 Use case of KPIs: Dimension of flood-related data processing ..... | 22 |
+| | I.4 Use case of KPIs: Dimension of flood-related applications..... | 23 |
+| | Bibliography..... | 25 |
+
+
+
+# Recommendation ITU-T Y.4911
+
+## Key performance indicators of information and communication technology (ICT)-based data support capabilities for urban flood disaster prevention and mitigation
+
+# 1 Scope
+
+This Recommendation includes a set of key performance indicators to assess ICT-based data support capabilities for urban flood disaster prevention and mitigation.
+
+# 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.
+
+[ISO 19123-1] ISO 19123-1:2023, *Geographic information – Schema for coverage geometry and functions. Part 1: Fundamentals*.
+
+# 3 Definitions
+
+### 3.1 Terms defined elsewhere
+
+This Recommendation uses the following terms defined elsewhere:
+
+**3.1.1 internet of things (IoT)** [b-ITU-T Y.4000]: A global infrastructure for the information society, enabling advanced services by interconnecting (physical and virtual) things based on existing and evolving interoperable information and communication technologies.
+
+NOTE 1 – Through the exploitation of identification, data capture, processing and communication capabilities, the IoT makes full use of things to offer services to all kinds of applications, whilst ensuring that security and privacy requirements are fulfilled.
+
+NOTE 2 – From a broader perspective, the IoT can be perceived as a vision with technological and societal implications.
+
+**3.1.2 sensor** [b-ITU-T Y.4105]: An electronic device that senses a physical condition or chemical compound and delivers an electronic signal proportional to the observed characteristic.
+
+**3.1.3 smart sustainable city** [b-ITU-T Y.4900]: A smart sustainable city is an innovative city that uses information and communication technologies (ICTs) and other means to improve quality of life, efficiency of urban operation and services and competitiveness, while ensuring that it meets the needs of present and future generations with respect to economic, social, environmental, as well as cultural aspects.
+
+NOTE – City competitiveness refers to policies, institutions, strategies and processes that determine the city's sustainable productivity.
+
+### 3.2 Terms defined in this Recommendation
+
+None.
+
+# **4 Abbreviations and acronyms**
+
+This Recommendation uses the following abbreviations and acronyms:
+
+| | |
+|-----|------------------------------------------|
+| 2D | Two Dimensional |
+| 3D | Three Dimensional |
+| ICT | Information and Communication Technology |
+| KPI | Key Performance Indicator |
+| SSC | Smart Sustainable City |
+| UAV | Unmanned Aerial Vehicle |
+
+# **5 Conventions**
+
+In this Recommendation:
+
+The keyword "core" indicates this key performance indicator (KPI) should be included during the evaluation process of ICT-based data support capabilities for urban flood disaster prevention and mitigation.
+
+The keyword "optional" indicates this KPI can be alternatively included during the evaluation process of data support capabilities for urban flood disaster prevention and mitigation.
+
+# **6 Overview**
+
+### **6.1 Urban flood disaster prevention and mitigation**
+
+Urban flood disasters occur frequently worldwide and cause severe casualties and huge economic losses. Prevention and mitigation operations are of vital significance to provide relief for urban flood disasters.
+
+High quality, accurate and comprehensive data support is of great importance to the decision making for urban flood disaster prevention and mitigation. In particular, the three aspects of spatiotemporal coverage, accuracy and timeliness of data are very important for urban flood response. Spatiotemporal coverage [ISO 19123-1] ensures that there is data available when and where urban flood disasters occur. Accuracy ensures that the data quality is sufficient for use. Timeliness means up-to-date data items instead of outdated ones are available. Data support capabilities, including the richness of data, the accuracy of data and the timeliness of data, for urban flood disaster prevention and mitigation are critical for cities to combat urban flood disasters.
+
+There are usually two scenarios for urban flood disaster prevention and mitigation: daily management and emergency management. As shown in Figure 1, ICT can be used in the four dimensions of collecting various types of data from the physical world, transmitting data to the data centre, processing data and supporting decision-making through domain-specific applications.
+
+Hence, ICT-based data support capabilities for urban flood disaster prevention and mitigation can contribute to decision-making in two different application scenarios of daily and emergency management.
+
+
+
+Scenarios:
+
+- Daily management
+- Emergency management
+
+ICT-based urban flood disaster prevention and mitigation
+
+- ① Data collection
+- ② Data transmission
+- ③ Data processing
+- ④ Applications
+
+Figure 1 illustrates the scenarios and dimensions related to ICT-based data support for urban flood disaster prevention and mitigation. The diagram shows a 3D perspective of an urban environment with a river. Various sensors are shown: Satellites for data collection, UAVs for data collection, Ground sensors (Cellar flow, Pipeline density, Soil type, Meteorological stations, Hydrologic station, Water level), and Damaged buildings. Data flows from these sensors to a Data centre (Data transmission) and then to a Processing centre (Data processing). The final output is Applications (Decision-making service). A legend on the right lists the four dimensions: 1 Data collection, 2 Data transmission, 3 Data processing, and 4 Applications. A box on the left lists the scenarios: Daily management and Emergency management.
+
+Figure 1: Scenarios and dimensions related to ICT-based data support for urban flood disaster prevention and mitigation. The diagram illustrates a 3D perspective of an urban environment with a river. Various sensors are shown: Satellites for data collection, UAVs for data collection, Ground sensors (Cellar flow, Pipeline density, Soil type, Meteorological stations, Hydrologic station, Water level), and Damaged buildings. Data flows from these sensors to a Data centre (Data transmission) and then to a Processing centre (Data processing). The final output is Applications (Decision-making service). A legend on the right lists the four dimensions: 1 Data collection, 2 Data transmission, 3 Data processing, and 4 Applications. A box on the left lists the scenarios: Daily management and Emergency management.
+
+**Figure 1 – Scenarios and dimensions related to ICT-based data support for urban flood disaster prevention and mitigation**
+
+**Data collection:** The overall layout of sensors determines the spatial distribution of the data, which is very important. For daily and emergency decision-making, whether the spatial, temporal and accuracy properties of data can fulfil the tasks has significant impacts. Thus, they should be included as part of the KPIs.
+
+**Data transmission:** Daily and emergency reliability for data transmission is of great significance during urban flood disaster prevention and mitigation. Therefore, they should be included as part of the KPIs.
+
+**Data processing:** Similar to data collection, whether the spatial and temporal coverage of data and its accuracy can fulfil the requirements of daily and emergency decision-making matters. So, they should be included as part of the KPIs.
+
+**Applications:** The availability of analysis, data mining, simulation, prediction and visualization functions, and their performances are important for flood disaster decision-making. They should be included as part of the KPIs.
+
+## 6.2 General principles for selecting KPIs
+
+The selection of ICT-based data supporting KPIs for floods is based on the following principles:
+
+- Independent: The KPIs should be mutually exclusive or orthogonal (i.e., overlapping of KPIs should be avoided as much as possible), and changes to one KPI should not impact the evaluation of, or preferences given to other KPIs.
+- Consistent: The meaning of each KPI should be clear, simple and easy to understand. A widely accepted definition of the KPIs (not open to different interpretations) assists different users to interpret them in the same way. Also, the calculation of the associated data should be intuitive and simple.
+- Measurable: The KPIs should be defined in a way that the value can be measured and compared scientifically between different cities, i.e., the KPIs should be comparable over time and space. The measurement should be as objective as possible. The historic and current data should be either available or easy to collect.
+- Achievable: The goal of the KPIs should be achievable and the set of indicators should cover flood disaster responding aspects of smart sustainable cities (SSCs). It should also be possible to extend and amend the set of KPIs according to the development of ICT.
+
+- Insightful: The KPIs should provide insight on the capability evaluation of the city for flood disaster response. Indicators as a whole should reflect the level of cities' general development and provide guidance for further improvement in flood disaster response.
+
+# 7 Structure of KPIs
+
+KPIs of ICT-based data support capabilities for urban flood disaster prevention and mitigation can be used to assess cities' capabilities in the aspect of preparing and fighting for flood disasters. The KPIs in this Recommendation focus on the ICT-related data support capabilities of cities in flood disasters. As shown in Figure 2, KPIs of ICT-based data support capabilities for urban flood disaster prevention and mitigation can be categorized into four types: flood-related data collection, flood-related data transmission, flood-related data processing, and flood-related applications.
+
+
+
+```
+
+graph TD
+ Root([Key performance indicators of ICT-based data support capability for urban flood disaster prevention and mitigation])
+ Root --> DC[Flood-related data collection]
+ Root --> DT[Flood-related data transmission]
+ Root --> DP[Flood-related data processing]
+ Root --> FA[Flood-related applications]
+
+ DC --> DC1(Rationality of sensor layout)
+ DC --> DC2(Fulfilment of daily decision-making)
+ DC --> DC3(Fulfilment of emergency decision-making)
+
+ DT --> DT1(Daily reliability)
+ DT --> DT2(Emergency reliability)
+
+ DP --> DP1(Fulfilment of daily decision-making)
+ DP --> DP2(Fulfilment of emergency decision-making)
+
+ FA --> FA1(Functions)
+ FA --> FA2(Performances)
+ FA --> FA3(Analysis and data mining capability)
+ FA --> FA4(Simulation capability)
+ FA --> FA5(Visualization capability)
+ FA --> FA6(Prediction capability)
+
+```
+
+Y.4911(25)
+
+Figure 2: Structure of KPIs for ICT-based data support capabilities for urban flood disaster prevention and mitigation. The diagram is a hierarchical tree. At the top is an oval labeled 'Key performance indicators of ICT-based data support capability for urban flood disaster prevention and mitigation'. It branches into four rectangular boxes: 'Flood-related data collection', 'Flood-related data transmission', 'Flood-related data processing', and 'Flood-related applications'. Each of these boxes has a corresponding vertical stack of smaller rounded rectangular boxes below it. 'Flood-related data collection' includes 'Rationality of sensor layout', 'Fulfilment of daily decision-making', and 'Fulfilment of emergency decision-making'. 'Flood-related data transmission' includes 'Daily reliability' and 'Emergency reliability'. 'Flood-related data processing' includes 'Fulfilment of daily decision-making' and 'Fulfilment of emergency decision-making'. 'Flood-related applications' includes 'Functions', 'Performances', 'Analysis and data mining capability', 'Simulation capability', 'Visualization capability', and 'Prediction capability'.
+
+**Figure 2 – Structure of KPIs for ICT-based data support capabilities for urban flood disaster prevention and mitigation**
+
+The KPIs for ICT-based flood-related data collection consider the rationality of sensor layout, and spatiotemporal fulfilment of daily and emergency decision-making, as shown in Table 1.
+
+**Table 1 – List of KPIs for ICT-based flood-related data collection**
+
+| Dimension | Sub-dimension | KPI name | Type |
+|-------------------------------|------------------------------|----------------------------------------|------|
+| Flood-related data collection | Rationality of sensor layout | Coverage ratio of waterlogging regions | Core |
+| | | Coverage ratio of key monitoring means | Core |
+
+**Table 1 – List of KPIs for ICT-based flood-related data collection**
+
+| Dimension | Sub-dimension | KPI name | Type |
+|-----------|-----------------------------------------|-----------------------------------------------------------|----------|
+| | | Coverage ratio of key observation variables | Core |
+| | | Sensor density | Optional |
+| | Fulfilment of daily decision-making | Temporal coverage fulfilment of daily decision-making | Core |
+| | | Spatial coverage fulfilment of daily decision-making | Core |
+| | | Accuracy fulfilment of daily decision-making | Core |
+| | Fulfilment of emergency decision-making | Temporal coverage fulfilment of emergency decision-making | Core |
+| | | Spatial coverage fulfilment of emergency decision-making | Core |
+| | | Accuracy fulfilment of emergency decision-making | Core |
+
+The KPIs for ICT-based flood-related data transmission consider two aspects of daily and emergency reliability, as shown in Table 2.
+
+**Table 2 – List of KPIs for ICT-based flood-related data transmission**
+
+| Dimension | Sub-dimension | KPI | Type |
+|---------------------------------|-----------------------|------------------------------------------|----------|
+| Flood-related data transmission | Daily reliability | Time delay | Core |
+| | | Error rate | Core |
+| | | Mean recovery time | Core |
+| | Emergency reliability | Time delay | Core |
+| | | Error rate | Core |
+| | | Mean recovery time | Core |
+| | | Existence of emergency data transmission | Core |
+| | | Diversity of emergency data transmission | Optional |
+
+**Table 2 – List of KPIs for ICT-based flood-related data transmission**
+
+| Dimension | Sub-dimension | KPI | Type |
+|-----------|---------------|------------|----------|
+| | | Timeliness | Optional |
+
+The KPIs for ICT-based flood-related data processing usually consider the two aspects of fulfilment of daily and emergency decision-making needs, as shown in Table 3.
+
+**Table 3 – List of KPIs for ICT-based flood-related data processing**
+
+| Dimension | Sub-dimension | KPI | Type |
+|-------------------------------|-----------------------------------------|-----------------------------------------------------------|----------|
+| Flood-related data processing | Fulfilment of daily decision-making | Accuracy fulfilment of daily decision-making | Core |
+| | | Spatial coverage fulfilment of daily decision-making | Core |
+| | | Temporal coverage fulfilment of daily decision-making | Core |
+| | | Time consumption for daily decision-making | Optional |
+| | Fulfilment of emergency decision-making | Accuracy fulfilment of emergency decision-making | Core |
+| | | Spatial coverage fulfilment of emergency decision-making | Core |
+| | | Temporal coverage fulfilment of emergency decision-making | Core |
+| | | Time consumption for emergency decision-making | Optional |
+
+The KPIs for ICT-based flood-related applications consider six aspects: functions, performance, analysis and data mining capability, simulation capability, prediction capability, and visualization capability, as shown in Table 4.
+
+**Table 4 – List of KPIs for ICT-based flood-related applications**
+
+| Dimension | Sub-dimension | KPI | Type |
+|----------------------------|-------------------------------------|----------------------------------------------------|----------|
+| Flood-related applications | Functions | Richness of functions | Core |
+| | Performance | Average failure rate | Core |
+| | | Average failure recovery time | Core |
+| | Analysis and data mining capability | Information fulfilment of analysis and data mining | Core |
+| | | Analysis and data mining accuracy | Core |
+| | Simulation capability | Fulfilment of simulation time | Optional |
+| | | Simulation accuracy | Optional |
+| | Prediction capability | Fulfilment of lead time | Optional |
+| | | Prediction accuracy | Optional |
+
+**Table 4 – List of KPIs for ICT-based flood-related applications**
+
+| Dimension | Sub-dimension | KPI | Type |
+|-----------|--------------------------|--------------------|----------|
+| | Visualization capability | Response time | Core |
+| | | Data throughput | Core |
+| | | Visualization mode | Optional |
+
+The KPIs presented in this Recommendation reflect a set of KPIs that may be adjusted based on national/regional requirements and regulations, operational conditions and scenarios.
+
+## 8 KPIs: Dimension of flood-related data collection
+
+The following section contains the indicators related to the dimension of flood-related data collection.
+
+### 8.1 Rationality of sensor layout
+
+| Dimension | Flood-related data collection |
+|-----------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Sub-dimension | Rationality of sensor layout |
+| KPI name | Coverage ratio of key observation variables |
+| Type: | Core |
+| Definition/
Description | Percentage of local flood observation variables available out of key flood observation variables |
+| Rationale/
Interpretation/
Benchmarking | This indicator demonstrates the percentage of local flood observation variables available out of key flood observation variables.
Key flood observation variables include water level, precipitation, flooded area, land use/land cover, soil moisture, wind direction, wind speed, digital elevation model, underground pipe networks.
An increasing trend and higher values are considered positive. |
+| Unit | Percentage |
+
+| Dimension | Flood-related data collection |
+|-----------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Sub-dimension | Rationality of sensor layout |
+| KPI name | Coverage ratio of waterlogging regions |
+| Type | Core |
+| Definition/
Description | Percentage of historical waterlogging regions deployed with sensors |
+| Rationale/
Interpretation/
Benchmarking | This indicator demonstrates the percentage of historical waterlogging regions deployed with sensors.
Data that includes any type of sensor (e.g., water level sensors, camera sensors) should be collected.
An increasing trend and higher values are considered positive. |
+| Unit | Percentage |
+
+| Dimension | Flood-related data collection |
+|-----------------------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Sub-dimension | Rationality of sensor layout |
+| KPI name | Coverage ratio of key monitoring means |
+| Type | Core |
+| Definition/
Description | Percentage of local flood monitoring means available out of key flood monitoring means |
+| Rationale/
Interpretation/
Benchmarking | This indicator demonstrates the percentage of local flood monitoring means available out of key flood monitoring means.
Key flood monitoring means include remote sensing, unmanned aerial vehicles (UAVs), ground sensing and social sensing.
An increasing trend and higher values are considered positive. |
+| Unit | Percentage |
+
+| Dimension | Flood-related data collection |
+|-----------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Sub-dimension | Rationality of sensor layout |
+| KPI name | Sensor density |
+| Type | Optional |
+| Definition/
Description | Number of flood-related sensors per km 2 |
+| Rationale/
Interpretation/
Benchmarking | This indicator demonstrates the number of flood-related sensors per unit area.
Data that includes any type of flood-related sensors, e.g., satellite sensors, UAVs and ground sensors, should be collected.
An increasing trend and higher values are considered positive. |
+| Unit | Number/ km 2 |
+
+### 8.2 Fulfilment of daily decision-making
+
+| Dimension | Flood-related data collection |
+|-----------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Sub-dimension | Fulfilment of daily decision-making |
+| KPI name | Temporal coverage fulfilment of daily decision-making |
+| Type | Core |
+| Definition/
Description | Percentage of temporal coverage of sensors available out of temporal requirements for daily decision-making |
+| Rationale/
Interpretation/
Benchmarking | This indicator demonstrates the percentage of temporal coverage available out of temporal requirements for daily decision-making.
Data that includes satellite and ground sensors, could be collected.
An increasing trend and higher values are considered positive. |
+| Unit | Percentage |
+
+| Dimension | Flood-related data collection |
+|-----------------------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Sub-dimension | Fulfilment of daily decision-making |
+| KPI name | Spatial coverage fulfilment of daily decision-making |
+| Type | Core |
+| Definition/
Description | Percentage of spatial coverage of sensors available out of spatial requirements for daily decision-making |
+| Rationale/
Interpretation/
Benchmarking | This indicator demonstrates the percentage of spatial coverage available out of spatial requirements for daily decision-making.
An increasing trend and higher values are considered positive. |
+| Unit | Percentage |
+
+| Dimension | Flood-related data collection |
+|-----------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Sub-dimension | Fulfilment of daily decision-making |
+| KPI name | Accuracy fulfilment of daily decision-making |
+| Type | Core |
+| Definition/
Description | Percentage of local accuracy available out of accuracy requirements for daily decision-making |
+| Rationale/
Interpretation/
Benchmarking | This indicator demonstrates the percentage of local accuracy available out of accuracy requirements for daily decision-making.
An increasing trend and higher values are considered positive. |
+| Unit | Percentage |
+
+### 8.3 Fulfilment of emergency decision-making
+
+| Dimension | Flood-related data collection |
+|-----------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Sub-dimension | Fulfilment of emergency decision-making |
+| KPI name | Temporal coverage fulfilment of emergency decision-making |
+| Type | Core |
+| Definition/
Description | Percentage of temporal coverage available out of temporal requirements for emergency decision-making |
+| Rationale/
Interpretation/
Benchmarking | This indicator demonstrates the percentage of temporal coverage available out of temporal requirements for emergency decision-making.
Data that includes any type of sensor, e.g., satellite sensors, UAVs, ground sensors and social sensing, could be collected.
An increasing trend and higher values are considered positive. |
+| Unit | Percentage |
+
+| Dimension | Flood-related data collection |
+|-----------------------------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Sub-dimension | Fulfilment of emergency decision-making |
+| KPI name | Spatial coverage fulfilment of emergency decision-making |
+| Type | Core |
+| Definition/
Description | Percentage of spatial coverage available out of spatial requirements for emergency decision-making |
+| Rationale/
Interpretation/
Benchmarking | This indicator demonstrates the percentage of spatial coverage available out of spatial requirements for emergency decision-making.
An increasing trend and higher values are considered positive. |
+| Unit | Percentage |
+
+| Dimension | Flood-related data collection |
+|-----------------------------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Sub-dimension | Fulfilment of emergency decision-making |
+| KPI name | Accuracy fulfilment of emergency decision-making |
+| Type | Core |
+| Definition/
Description | Percentage of local accuracy available out of accuracy requirements for emergency decision-making |
+| Rationale/
Interpretation/
Benchmarking | This indicator demonstrates the percentage of local accuracy available out of accuracy requirements for emergency decision-making.
An increasing trend and higher values are considered positive. |
+| Unit | Percentage |
+
+## 9 KPIs: Dimension of flood-related data transmission
+
+The following section contains the indicators related to the dimension of flood-related data transmission.
+
+### 9.1 Daily reliability
+
+| Dimension | Flood-related data transmission |
+|-----------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Sub-dimension | Daily reliability |
+| KPI name | Time delay |
+| Type | Core |
+| Definition/
Description | Lag time between the flood observation and the flood occurrence in daily flood management |
+| Rationale/
Interpretation/
Benchmarking | This indicator demonstrates the lag time between the flood observation and the flood occurrence in daily flood management.
A decreasing trend and lower values are considered positive. |
+| Unit | Minutes |
+
+| Dimension | Flood-related data transmission |
+|-----------------------------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Sub-dimension | Daily reliability |
+| KPI name | Error rate |
+| Type | Core |
+| Definition/
Description | Number of failures per unit time |
+| Rationale/
Interpretation/
Benchmarking | This indicator demonstrates the number of failures per unit time.
Data that includes all types of transmissions may be another method for data collection to obtain the number of failures per unit time.
A decreasing trend and lower values are considered positive. |
+| Unit | Number/Month |
+
+| Dimension | Flood-related data transmission |
+|-----------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Sub-dimension | Daily reliability |
+| KPI name | Mean recovery time |
+| Type | Core |
+| Definition/
Description | Time interval between fault occurrence and fault recovery |
+| Rationale/
Interpretation/
Benchmarking | This indicator demonstrates the time interval between fault occurrence and fault recovery in daily flood management.
A decreasing trend and lower values are considered positive. |
+| Unit | Minutes |
+
+### 9.2 Emergency reliability
+
+| Dimension | Flood-related data transmission |
+|-----------------------------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Sub-dimension | Emergency reliability |
+| KPI name | Time delay |
+| Type | Core |
+| Definition/
Description | Lag time between the flood observation and the flood occurrence in emergency management |
+| Rationale/
Interpretation/
Benchmarking | This indicator demonstrates the lag time between the flood observation and the flood occurrence in emergency management.
A decreasing trend and lower values are considered positive. |
+| Unit | Minutes |
+
+| Dimension | Flood-related data transmission |
+|-----------------------------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Sub-dimension | Emergency reliability |
+| KPI name | Error rate |
+| Type | Core |
+| Definition/
Description | Number of failures per unit time |
+| Rationale/
Interpretation/
Benchmarking | This indicator demonstrates the number of failures per unit time.
Data that includes all types of transmissions may be another method for data collection to obtain the number of failures per unit time.
A decreasing trend and lower values are considered positive. |
+| Unit | Number/Month |
+
+| Dimension | Flood-related data transmission |
+|-----------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Sub-dimension | Emergency reliability |
+| KPI name | Mean recovery time |
+| Type | Core |
+| Definition/
Description | Time interval between fault occurrence and fault recovery |
+| Rationale/
Interpretation/
Benchmarking | This indicator demonstrates the time interval between fault occurrence and fault recovery in daily flood management.
A decreasing trend and lower values are considered positive. |
+| Unit | Minutes |
+
+| Dimension | Flood-related data transmission |
+|-----------------------------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Sub-dimension | Emergency reliability |
+| KPI name | Existence of emergency data transmission |
+| Type | Core |
+| Definition/
Description | Whether emergency data transmission means exist or not |
+| Rationale/
Interpretation/
Benchmarking | This indicator demonstrates whether emergency data transmission means exist or not.
The value "yes" indicates there is emergency data transmission means.
The value "no" indicates there is no emergency data transmission means.
The value "yes" is considered positive. |
+| Unit | Enumerated |
+
+| Dimension | Flood-related data transmission |
+|-----------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Sub-dimension | Emergency reliability |
+| KPI name | Diversity of emergency data transmission |
+| Type | Optional |
+| Definition/
Description | Percentage of alternate transmission means available out of all possible alternate transmission means |
+| Rationale/
Interpretation/
Benchmarking | This indicator demonstrates the percentage of alternate transmission means available out of all possible alternate transmission means for emergency data transmission. Data that includes any alternate transmission means for emergencies should be collected.
All possible alternate transmission means include satellite communication, trunking communication, short-wave communication, microwave communication and broadband wireless communication. It can change with the development of new communication technologies.
An increasing trend and higher values are considered positive.
|
+| Unit | Percentage |
+
+| Dimension | Flood-related data transmission |
+|-----------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Sub-dimension | Emergency reliability |
+| KPI name | Timeliness |
+| Type | Optional |
+| Definition/
Description | Lag time between the flood observation and the flood occurrence in emergency |
+| Rationale/
Interpretation/
Benchmarking | This indicator demonstrates the lag time between the flood observation and the flood occurrence in emergency.
Surveys of timeliness for all types of sensors may be another method for data collection to obtain the lag time between the flood observation and the flood occurrence in emergency.
A decreasing trend and lower values are considered positive.
|
+| Unit | Minutes |
+
+## 10 KPIs: Dimension of flood-related data processing
+
+The following clause contains the indicators related to the dimension of flood-related data processing.
+
+### 10.1 Fulfilment of daily decision-making
+
+| Dimension | Flood-related data processing |
+|-----------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Sub-dimension | Fulfilment of daily decision-making |
+| KPI name | Accuracy fulfilment of daily decision-making |
+| Type | Core |
+| Definition/
Description | Percentage of the accuracy of local data processing results available out of the required data processing accuracy for daily decision-making |
+| Rationale/
Interpretation/
Benchmarking | This indicator demonstrates the percentage of the accuracy of local data processing results available out of the required data processing accuracy for daily decision-making.
Data that includes accuracy of any local data processing results for daily decision-making should be collected.
Required data processing accuracy can change with the space-time range in applications.
An increasing trend and higher values are considered positive.
|
+| Unit | Percentage |
+
+| Dimension | Flood-related data processing |
+|-----------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Sub-dimension | Fulfilment of daily decision-making |
+| KPI name | Temporal coverage fulfilment of daily decision-making |
+| Type | Core |
+| Definition/
Description | Percentage of the temporal coverage of local flood-related data processing results available out of the temporal requirements for daily decision-making |
+| Rationale/
Interpretation/
Benchmarking | This indicator demonstrates the percentage of the temporal coverage of flood-related data processing results available out of the temporal requirements for daily decision-making.
An increasing trend and higher values are considered positive.
|
+| Unit | Percentage |
+
+| Dimension | Flood-related data processing |
+|-----------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Sub-dimension | Fulfilment of daily decision-making |
+| KPI name | Spatial coverage fulfilment of daily decision-making |
+| Type | Core |
+| Definition/
Description | Percentage of spatial coverage of local flood-related data processing results available out of the spatial requirements for daily decision-making |
+| Rationale/
Interpretation/
Benchmarking | This indicator demonstrates the percentage of spatial coverage of flood-related data processing results available out of the spatial requirements for daily decision-making.
An increasing trend and higher values are considered positive.
|
+| Unit | Percentage |
+
+| Dimension | Flood-related data processing |
+|-----------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Sub-dimension | Fulfilment of daily decision-making |
+| KPI name | Time consumption for daily decision-making |
+| Type | Optional |
+| Definition/
Description | Time interval between the beginning and the ending of flood-related data processing for daily decision-making |
+| Rationale/
Interpretation/
Benchmarking | This indicator demonstrates the time interval between the beginning and the ending of flood-related data processing for daily decision-making.
A decreasing trend and lower values are considered positive. |
+| Unit | Minutes |
+
+### 10.2 Fulfilment of emergency decision-making
+
+| Dimension | Flood-related data processing |
+|-----------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Sub-dimension | Fulfilment of emergency decision-making |
+| KPI name | Accuracy fulfilment of emergency decision-making |
+| Type | Core |
+| Definition/
Description | Percentage of the accuracy of local data processing results available out of the required data processing accuracy for emergency decision-making |
+| Rationale/
Interpretation/
Benchmarking | This indicator demonstrates the percentage of the accuracy of local data processing results available out of the required data processing accuracy for emergency decision-making.
Data that includes accuracy of any local data processing results for emergency decision-making should be collected.
Required data processing accuracy can change with the space-time range in applications.
An increasing trend and higher values are considered positive. |
+| Unit | Percentage |
+
+| Dimension | Flood-related data processing |
+|-----------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Sub-dimension | Fulfilment of emergency decision-making |
+| KPI name | Temporal coverage fulfilment of emergency decision-making |
+| Type | Core |
+| Definition/
Description | Percentage of the temporal coverage of local flood-related data processing results available out of the temporal requirements for emergency decision-making |
+| Rationale/
Interpretation/
Benchmarking | This indicator demonstrates the percentage of the temporal coverage of flood-related data processing results available out of the temporal requirements for emergency decision-making.
An increasing trend and higher values are considered positive. |
+| Unit | Percentage |
+
+| Dimension | Flood-related data processing |
+|-----------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Sub-dimension | Fulfilment of emergency decision-making |
+| KPI name | Spatial coverage fulfilment of emergency decision-making |
+| Type | Core |
+| Definition/
Description | Percentage of spatial coverage of local flood-related data processing results available out of the spatial requirements for emergency decision-making |
+| Rationale/
Interpretation/
Benchmarking | This indicator demonstrates the percentage of spatial coverage of flood-related data processing results available out of the spatial requirements for emergency decision-making.
An increasing trend and higher values are considered positive. |
+| Unit | Percentage |
+
+| Dimension | Flood-related data processing |
+|-----------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Sub-dimension | Fulfilment of emergency decision-making |
+| KPI name | Time consumption for emergency decision-making |
+| Type: | Optional |
+| Definition/
Description | Time interval between the beginning and the ending of flood-related data processing for emergency decision-making |
+| Rationale/
Interpretation/
Benchmarking | This indicator demonstrates the time interval between the beginning and the ending of flood-related data processing for emergency decision-making.
A decreasing trend and lower values are considered positive. |
+| Unit | Minutes |
+
+## 11 KPIs: Dimension of flood-related applications
+
+The following section contains the indicators related to the dimension of flood-related applications.
+
+### 11.1 Functions
+
+| Dimension | Flood-related applications |
+|-----------------------------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Sub-dimension | Functions |
+| KPI name | Richness of functions |
+| Type | Core |
+| Definition/
Description | Percentage of local decision support flood system functions available out of required flood-related applications functions |
+| Rationale/
Interpretation/
Benchmarking | This indicator demonstrates the percentage of local flood system functions available out of all required flood system functions.
Data that includes any local flood system functions should be collected.
All required flood system functions include daily and emergency analysis and data mining, daily and emergency simulation, daily and emergency prediction, and daily and emergency visualization. It can change with the development of new flood decision support technologies.
An increasing trend and higher values are considered positive. |
+| Unit | Percentage |
+
+### 11.2 Performance
+
+| Dimension | Flood-related applications |
+|-----------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Sub-dimension | Performance |
+| KPI name | Average failure rate |
+| Type | Core |
+| Definition/
Description | Average number of failures per unit time of flood-related applications |
+| Rationale/
Interpretation/
Benchmarking | This indicator demonstrates the average number of failures per unit time of flood-related applications.
Data that includes all types of failures may be another method for data collection to obtain the average number of failures per unit time of flood-related applications.
A decreasing trend and lower values are considered positive. |
+| Unit | Number/Month |
+
+| Dimension | Flood-related applications |
+|-----------------------------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Sub-dimension | Performance |
+| KPI name | Average failure recovery time |
+| Type | Core |
+| Definition/
Description | Average time interval between failure occurrence and failure recovery |
+| Rationale/
Interpretation/
Benchmarking | This indicator demonstrates the average time interval between failure occurrence and failure recovery of flood-related applications.
A decreasing trend and lower values are considered positive. |
+| Unit | Minutes |
+
+### 11.3 Analysis and data mining capability
+
+| Dimension | Flood-related applications |
+|-----------------------------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Sub-dimension | Analysis and data mining capability |
+| KPI name | Information fulfilment of analysis and data mining |
+| Type | Core |
+| Definition/
Description | Percentage of data type analysed and mined in local flood-related applications available out of required data type for analysis and mining for flood-related applications |
+| Rationale/
Interpretation/
Benchmarking | This indicator demonstrates the percentage of data type analysed and mined in local flood-related applications available out of required data type for analysis and mining for flood-related applications.
Data that includes any data type analysed and mined should be collected.
Required data type for analysis and mining for flood-related applications include vector, raster, numeric, data stream, optical image and synthetic aperture radar images, etc. It can change with the development of new data processing and flood decision support technologies.
An increasing trend and higher values are considered positive. |
+| Unit | Percentage |
+
+| Dimension | Flood-related applications |
+|-----------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Sub-dimension | Analysis and data mining capability |
+| KPI name | Analysis and data mining accuracy |
+| Type | Core |
+| Definition/
Description | Percentage of average local analysis and data mining accuracy available out of average analysis and data mining accuracy requirements for flood-related applications |
+| Rationale/
Interpretation/
Benchmarking | This indicator demonstrates the percentage of local analysis and data mining accuracy available out of analysis and data accuracy requirements for flood-related applications.
An increasing trend and higher values are considered positive. |
+| Unit | Percentage |
+
+### 11.4 Simulation capability
+
+| Dimension | Flood-related applications |
+|-----------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Sub-dimension | Simulation capability |
+| KPI name | Fulfilment of simulation time |
+| Type | Optional |
+| Definition/
Description | Percentage of local simulation time available out of required simulation time for flood-related applications |
+| Rationale/
Interpretation/
Benchmarking | This indicator demonstrates the percentage of local simulation time available out of required simulation time for flood-related applications.
An increasing trend and lower values are considered positive. |
+| Unit | Percentage |
+
+| Dimension | Flood-related applications |
+|-----------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Sub-dimension | Simulation capability |
+| KPI name | Simulation accuracy |
+| Type | Optional |
+| Definition/
Description | Percentage of simulation accuracy available out of simulation accuracy requirements for flood-related applications |
+| Rationale/
Interpretation/
Benchmarking | This indicator demonstrates the percentage of simulation accuracy available out of simulation accuracy requirements for flood-related applications.
An increasing trend and higher values are considered positive. |
+| Unit | Percentage |
+
+### 11.5 Prediction capability
+
+| Dimension | Flood-related applications |
+|-----------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Sub-dimension | Prediction capability |
+| KPI name | Fulfilment of lead time |
+| Type | Optional |
+| Definition/
Description | Percentage of local lead time available out of required lead time for flood-related applications |
+| Rationale/
Interpretation/
Benchmarking | This indicator demonstrates the percentage of local lead time available out of required lead time for flood-related applications.
An increasing trend and lower values are considered positive. |
+| Unit | Percentage |
+
+| Dimension | Flood-related applications |
+|-----------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Sub-dimension | Prediction capability |
+| KPI name | Prediction accuracy |
+| Type | Optional |
+| Definition/
Description | Percentage of prediction accuracy available out of prediction accuracy requirements for flood-related applications |
+| Rationale/
Interpretation/
Benchmarking | This indicator demonstrates percentage of prediction accuracy available out of prediction requirements for flood-related applications.
An increasing trend and higher values are considered positive. |
+| Unit | Percentage |
+
+### 11.6 Visualization capability
+
+| Dimension | Flood-related applications |
+|-----------------------------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Sub-dimension | Visualization capability |
+| KPI name | Response Time |
+| Type | Core |
+| Definition/
Description | The time consumption from users' request for data visualization to the completion of data visualization of flood-related applications |
+| Rationale/
Interpretation/
Benchmarking | This indicator demonstrates the time consumption of the visualization function of flood-related applications.
Longer time consumption means weaker data visualization capability. Smaller values are considered positive. |
+| Unit | Milliseconds |
+
+| Dimension | Flood-related applications |
+|-----------------------------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Sub-dimension | Visualization capability |
+| KPI name | Data throughput |
+| Type | Core |
+| Definition/
Description | The largest data volume which the visualization function of flood-related applications can handle in unit time. |
+| Rationale/
Interpretation/
Benchmarking | This indicator demonstrates the largest data volume which the visualization function of flood-related applications can handle in unit time.
The larger the data volume processed at a time means the stronger the data throughput capability is. Greater values are considered positive. |
+| Unit | Gigabytes per second |
+
+| Dimension | Flood-related applications |
+|-----------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Sub-dimension | Visualization capability |
+| KPI name | Visualization mode |
+| Type | Optional |
+| Definition/
Description | User interface display mode of flood-related applications |
+| Rationale/
Interpretation/
Benchmarking | This indicator demonstrates the user interface display mode of flood-related applications.
User interface display mode of flood-related applications usually include 2D, 3D or a higher dimension.
The three or higher dimension values are considered positive. |
+| Unit | Enumerated |
+
+## Appendix I
+
+### Use case for KPIs of ICT-based data support capabilities for urban flood disaster prevention and mitigation
+
+(This appendix does not form an integral part of this Recommendation.)
+
+The KPIs of ICT-based data support capabilities for urban flood disaster prevention and mitigation are the metrics required to evaluate a city's ability to prevent and mitigate urban flood disasters. This evaluation is of great significance for formulating scientific and reasonable flood control strategies and optimizing resource allocation. This appendix explains a use case for assessing ICT-based data support capabilities for flood disasters using KPIs.
+
+City A is often faced with waterlogging. There are recorded regions which are more easily flooded in city A, and the Water Bureau of city A has deployed some equipment in these regions to monitor possible flooding. City A also has many ways to monitor and combat floods in daily or emergency situations. All these ICT-based data support capabilities for flood prevention and mitigation can be quantified by KPIs defined in this document. For example, city A is recorded as having 50 waterlogging sites, of which 40 have sensors. Therefore, the value of the KPI "coverage ratio of waterlogging regions" is $40 / 50 = 80.0\%$ . City A has all the four key flood monitoring means, including remote sensing, UAVs, ground sensing and social sensing. Hence, the value of the KPI "coverage ratio of key monitoring means" of city A is $100.0\%$ . In addition, City A has alternative data transmission for emergencies, so the value of the KPI "Existence of Emergency Data Transmission" is yes. Details of KPIs for floods of city A can be found in Tables I.1 to I.4.
+
+### I.1 Use case of KPIs: Dimension of flood-related data collection
+
+**Table I.1 – Use case of KPIs: Dimension of flood-related data collection**
+
+| KPI name | KPI value | Intended meaning |
+|------------------------------------------------------------------|----------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Coverage ratio of key observation variables | 70.0% | The flood observation variables of city A included is 70.0% of the key flood observation variables. |
+| Coverage ratio of waterlogging regions | 80.0% | The historical waterlogging area deployed with sensors is 80.0% of the entire historical waterlogging area. |
+| Coverage ratio of key monitoring means | 100.0% | The flood monitoring means of city A include all the key flood monitoring means. |
+| Sensor density | 0.63/km 2 | There are 0.63 flood-related sensors per square kilometre. |
+| Temporal coverage fulfilment of daily decision-making | 90.0% | The sensor time coverage is 90.0% of the time frame required for daily decision-making. |
+| Spatial coverage fulfilment of daily decision-making | 60.0% | The spatial coverage of the sensors reached 60.0% of the spatial range required for daily decision-making. |
+| Accuracy fulfilment of daily decision-making | 100.0% | The maximum accuracy of the sensor used for daily decision-making reaches 100.0% of the minimum accuracy requirement of daily decision-making, meeting the minimum accuracy requirement of daily decision-making. |
+| Temporal coverage fulfilment of emergency decision-making | 70.0% | Sensor coverage reached 70.0% of the time frame required for emergency decisions. |
+
+**Table I.1 – Use case of KPIs: Dimension of flood-related data collection**
+
+| KPI name | KPI value | Intended meaning |
+|-----------------------------------------------------------------|-----------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Spatial coverage fulfilment of emergency decision-making | 70.0% | The spatial coverage of the sensors reached 70.0% of the spatial range required for emergency response decisions. |
+| Accuracy fulfilment of emergency decision-making | 100.0% | The maximum accuracy of all types of sensors used for emergency decision-making accounts for 100.0% of the minimum accuracy requirements of emergency decision-making, meeting the minimum accuracy requirements of emergency decision-making. |
+
+### **I.2 Use case of KPIs: Dimension of flood-related data transmission**
+
+**Table I.2 – Use case of KPIs: Dimension of flood-related data transmission**
+
+| KPI name | KPI value | Intended meaning |
+|-------------------------------------------------|------------|---------------------------------------------------------------------------------------------------------------------|
+| Existence of emergency Data transmission | yes | Emergency data transmission facility exists. |
+| Time delay | 15 minutes | The flood observation time in daily flood management is about 15 minutes after the flood occurrence time. |
+| Error rate | 3/month | Average number of failures per month in daily flood management is 3. |
+| Mean recovery time | 45 minutes | The average time required for each fault recovery in daily flood management is 45 minutes. |
+| Diversity of emergency data transmission | 80.0% | City A's alternate transmission means account for 80.0% of all possible alternate transmission means for emergency. |
+| Timeliness | 10 minutes | The lag time between flood observation and flood in emergency is 10 minutes. |
+
+### **I.3 Use case of KPIs: Dimension of flood-related data processing**
+
+**Table I.3 – Use case of KPIs: Dimension of flood-related data processing**
+
+| KPI name | KPI value | Intended meaning |
+|--------------------------------------------------------------|-----------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Accuracy fulfilment of daily decision-making | 100.0% | The accuracy of flood-related data processing results reaches 100.0% of the data processing accuracy required for daily decision-making, which meets the data processing accuracy requirements of daily decision-making. |
+| Temporal coverage fulfilment of daily decision-making | 100.0% | The temporal coverage of flood-related data processing reached 100.0% of the temporal requirements for daily decision-making. |
+| Spatial coverage fulfilment of daily decision-making | 90.0% | The spatial coverage of flood-related data processing reached 90.0% of the spatial requirements for daily decision-making. |
+
+**Table I.3 – Use case of KPIs: Dimension of flood-related data processing**
+
+| KPI name | KPI value | Intended meaning |
+|------------------------------------------------------------------|------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Time consumption for daily decision-making | 30 minutes | The time interval between the start and end of flood-related data processing in daily decision-making is generally 30 minutes. |
+| Accuracy fulfilment of emergency decision-making | 96.4% | The accuracy of flood-related data processing results did not meet the data processing accuracy required for emergency decision-making, which only reached 96.4%. |
+| Temporal coverage fulfilment of emergency decision-making | 100.0% | Temporal coverage of flood-related data processing accounted for 100.0% of the temporal requirements for emergency decision-making. |
+| Spatial coverage fulfilment of emergency decision-making | 100.0% | The spatial coverage of water-related data processing represents 100.0% of the spatial requirements for daily decisions. |
+| Time consumption for emergency decision-making | 40 minutes | The time interval from start to end of flood-related data processing in emergency decisions is generally 40 minutes. |
+
+### **I.4 Use case of KPIs: Dimension of flood-related applications**
+
+**Table I.4 – Use case of KPIs: Dimension of flood-related applications**
+
+| KPI name | KPI value | Intended meaning |
+|-----------------------------------------------------------|------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Richness of functions | 100.0% | City A's flood system functions include all the required flood system functions. |
+| Average failure rate | 3/month | The average number of failures per month is 3. |
+| Average failure recovery time | 45 minutes | The average time interval between the failure and the recovery of flood-related applications is 45 minutes. |
+| Information fulfilment of analysis and data mining | 67.0% | The data types analysed and mined in the flood-related applications reached 67.0% of the data types required for analysis and data mining. |
+| Analysis and data mining accuracy | 88.0% | The accuracy of analysis and data mining in the flood-related applications is 88.0% of the requirements of data accuracy, which does not meet the requirements of system minimum analysis and data mining accuracy. |
+| Fulfilment of simulation time | 86.4% | The simulation time of flood-related applications is 86.4% of the simulation time required by the flood-related applications, which meets the requirements of the simulation time. |
+| Simulation accuracy | 78.7% | The simulation accuracy of flood-related applications accounts for 78.7% of the required simulation, which does not meet the accuracy requirements of simulation. |
+| Fulfilment of lead time | 100.0% | The lead time of city A's flood-related applications is 100.0% of the lead time required by the flood-related applications, which meets the lead time requirements of flood-related applications. |
+| Prediction accuracy | 100.0% | The prediction accuracy of flood-related applications is 100.0% of the prediction accuracy requirements, which |
+
+**Table I.4 – Use case of KPIs: Dimension of flood-related applications**
+
+| KPI name | KPI value | Intended meaning |
+|---------------------------|-------------------------|-----------------------------------------------------------------------------------------------------------------|
+| | | meets the prediction accuracy requirements of flood-related applications. |
+| Response time | 30 milliseconds | The response time for the data visualization module of flood-related applications is 30 milliseconds. |
+| Data throughput | 50 gigabytes per second | The data throughput for the data visualization module of flood-related applications is 50 gigabytes per second. |
+| Visualization mode | 3D | The user interface display mode of flood-related applications is 3D. |
+
+# Bibliography
+
+- [b-ITU-T Y.4000] Recommendation ITU-T Y.4000/Y.2060 (2012), *Overview of the Internet of things*.
+- [b-ITU-T Y.4105] Recommendation ITU-T Y.4105/Y.2221 (2010), *Requirements for support of ubiquitous sensor network (USN) applications and services in the NGN environment*.
+- [b-ITU-T Y.4900] Recommendation ITU-T Y.4900/L.1600 (2016), *Overview of key performance indicators in smart sustainable cities*.
+- [b-ITU-T Y.4902] Recommendation ITU-T Y.4902/L.1602 (2016), *Key performance indicators related to the sustainability impacts of information and communication technology in smart sustainable cities*.
+- [b-ITU-T Y.4903] Recommendation ITU-T Y.4903/L.1603 (2022), *Key performance indicators for smart sustainable cities to assess the achievement of sustainable development goals*.
+
+
+
+
+
+## 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 |
+| 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 | 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 |
\ No newline at end of file