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23.501
5.17.2.3.2 Mobility for UEs in single-registration mode
When the UE supports single-registration mode and network supports interworking procedure without N26 interface: - For mobility from 5GC to EPC, the UE with at least one PDU Session established in 5GC may either: - if supported and if it has received the network indication that interworking without N26 is supported, pe...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.17.2.3.3 Mobility for UEs in dual-registration mode
To support mobility in dual-registration mode, the support of N26 interface between AMF in 5GC and MME in EPC is not required. A UE that supports dual registration mode may operate in this mode when it receives an indication from the network that interworking without N26 is supported. For UE operating in dual-registrat...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.17.2.3.4 Redirection for UEs in connected state
When the UE supports single-registration mode or dual-registration mode without N26 interface: - If the UE is in CM-CONNECTED state in 5GC, the NG-RAN may perform RRC Connection Release with Redirection to E-UTRAN based on certain criteria (e.g. based on local configuration in NG-RAN, or triggered by the AMF upon recei...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.17.2.4 Mobility between 5GS and GERAN/UTRAN
IP address preservation upon direct mobility between 5GS and GERAN/UTRAN is not supported. Upon mobility from 5GS to GERAN/UTRAN (e.g. upon leaving NG-RAN coverage) the UE shall perform the A/Gb mode GPRS Attach procedure or Iu mode GPRS Attach procedure (see TS 23.060 [56]). As a UE option, to support IP address prese...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.17.2.5 Secondary DN authentication and authorization in EPS Interworking case
Secondary authentication/authorization by a DN-AAA server during the establishment of a PDN connection over 3GPP access to EPC, is supported based on following principles: - It is optional for the UE to support EAP-based secondary authentication and authorization by DN-AAA over EPC, - A SMF+PGW-C shall be used to serve...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.17.3 Interworking with EPC in presence of Non-3GPP PDU Sessions
When a UE is simultaneously connected to the 5GC over a 3GPP access and a non-3GPP access, it may have PDU Sessions associated with 3GPP access and PDU Sessions associated with non-3GPP access. When inter-system handover from 5GS to EPS is performed for PDU Sessions associated with 3GPP access, the PDU Sessions associa...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.17.4 Network sharing support and interworking between EPS and 5GS
The detailed description for supporting network sharing and interworking between EPS and 5GS is described in clauses 4.11.1.2.1, 4.11.1.2.2, 4.11.1.3.2 and 4.11.1.3.3 of TS 23.502 [3].
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.17.5 Service Exposure in Interworking Scenarios
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23.501
5.17.5.1 General
Clause 4.3.5 shows the Service Exposure Network Architecture in scenarios where for EPC-5GC Interworking is required. In scenarios where interworking between 5GS and EPC is possible, the network configuration is expected to associate UEs with SCEF+NEF node(s) for Service Capability Exposure. The SCEF+NEF hides the unde...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.17.5.2 Support of interworking for Monitoring Events
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.17.5.2.1 Interworking with N26 interface
In addition to the interworking principles documented in clause 5.17.2.2, the following applies for interworking with N26: - When UE moves from EPS to 5GS, when the AMF registers in UDM, if no event subscription via UDM is available, the AMF indicates the situation to the UDM and in this case the UDM can decide if the ...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.17.5.2.2 Interworking without N26 interface
In addition to the interworking principles documented in clause 5.17.2.3, the additional behaviour at EPS to 5GS mobility in clause 5.17.5.2.1 also applies. When SCEF+NEF performs the procedure of monitoring via the AMF as described in clause 4.15.3.2.4 ("Exposure with bulk subscription") in TS 23.502 [3], if the AMF d...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.17.5.3 Availability or expected level of a service API
A service related with common north-bound API may become unavailable due to UE being served by a CN node not supporting the service. If the availability or expected level of support of a service API associated with a UE changes, for example due to a mobility between 5GC and EPC, the AF shall be made aware of the change...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.17.6 Void
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23.501
5.17.7 Configuration Transfer Procedure between NG-RAN and E-UTRAN
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23.501
5.17.7.1 Architecture Principles for Configuration Transfer between NG-RAN and E-UTRAN
The purpose of the Configuration Transfer between NG-RAN and E-UTRAN is to enable the transfer the RAN configuration information between the gNB and eNodeB via MME and AMF. In order to make the information transparent for the MME and AMF, the information is included in a transparent container. The source and target RAN...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.17.7.2 Addressing, routing and relaying
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.17.7.2.1 Addressing
All the Configuration Transfer messages contain the addresses of the source and destination RAN nodes. An gNB node is addressed by the Target NG-RAN node identifier as described in TS 38.413 [34]. An eNodeB is addressed by the Target eNodeB identifier as described in TS 36.413 [100].
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.17.7.2.2 Routing
The source RAN node sends a message to its core network node including the source and destination addresses. MME uses the destination address to route the message to the correct AMF via N26 interface. AMF uses the destination address to route the message to the correct MME via N26 interface. The AMF connected to the de...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.17.7.2.3 Relaying
The AMF performs relaying between N2 and N26 messages as described in TS 38.413 [34] and TS 29.274 [101]. The MME performs relaying between S1 and N26 message as described in TS 36.413 [100] and TS 29.274 [101].
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.17.8 URSP Provisioning in EPS
When the UE registers in 5GS, the UE includes the Indication of URSP Provisioning Support in EPS in the UE Policy Container carried in Registration Request. On receiving this indication in the UE Policy Container, the PCF will enable the provisioning of the URSP to UE in EPS. The UE may include the indication of URSP P...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.18 Network Sharing
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23.501
5.18.1 General concepts
A network sharing architecture shall allow multiple participating operators to share resources of a single shared network according to agreed allocation schemes. The shared network includes a radio access network. The shared resources include radio resources. The shared network operator allocates shared resources to th...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.18.2 Broadcast system information for network sharing
If a shared NG-RAN is configured to indicate available networks (PLMNs and/or SNPNs) for selection by UEs, each cell in the shared radio access network shall in the broadcast system information include available core network operators in the shared network, including the PLMN IDs which represent the participating opera...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.18.3 Network selection by the UE
NOTE 1: This clause applies to UEs not operating in SNPN access mode. Network selection for UEs set to operate in SNPN access mode is described in clause 5.30.2.4. A UE that has a subscription to one of the sharing core network operators shall be able to select this core network operator while within the coverage area ...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.18.4 Network selection by the network
The NG-RAN uses the selected PLMN/SNPN (provided by the UE at RRC establishment, or, provided by the AMF/source NG-RAN at N2/Xn handover) to select target cells for future handovers (and radio resources in general) appropriately. The network should not move the UE to another available PLMN/SNPN, e.g. by handover, as lo...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.18.5 Network Sharing and Network Slicing
As defined in clause 5.15.1, a Network Slice is defined within a PLMN or SNPN. Network sharing is performed among different PLMNs and/or SNPNs. In the case of 5G MOCN, each PLMN or SNPN sharing the NG-RAN defines and supports its PLMN- or SNPN- specific set of slices that are supported by the common NG-RAN. In the case...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.19 Control Plane Load Control, Congestion and Overload Control
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.19.1 General
In order to ensure that the network functions within 5G System are operating under nominal capacity for providing connectivity and necessary services to the UE. Thus, it supports various measures to guard itself under various operating conditions (e.g. peak operating hour, extreme situations). It includes support for l...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.19.2 TNLA Load Balancing and TNLA Load Re-Balancing
AMF can support load balancing and re-balancing of TNL associations between 5G-AN and AMF by using mechanisms specified in clause 5.21.1.
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.19.3 AMF Load Balancing
The AMF Load Balancing functionality permits UEs that are entering into an AMF Region/AMF Set to be directed to an appropriate AMF in a manner that achieves load balancing between AMFs. This is achieved by setting a Weight Factor for each AMF, such that the probability of the 5G-AN selecting an AMF is proportional to W...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.19.4 AMF Load Re-Balancing
The AMF load re-balancing functionality permits cross-section of its subscribers that are registered on an AMF (within an AMF Set) to be moved to another AMF within the same AMF set with minimal impacts on the network and end users. AMF may request some or all of the 5G-AN node(s) to redirect a cross-section of UE(s) r...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.19.5 AMF Control Of Overload
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.19.5.1 General
The AMF shall contain mechanisms for avoiding and handling overload situations. This includes the following measures: - N2 overload control that could result in RRC reject, RRC Connection Release and unified access barring. - NAS congestion control.
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.19.5.2 AMF Overload Control
Under unusual circumstances, if AMF has reached overload situation or there is high probability that signalling storm will happen based on received analytics of signalling storm caused by NF(s) abnormal signalling or set of UEs in specific group, slice or priority as described in clause 6.22 in TS 23.288 [86], the AMF ...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.19.6 SMF Overload Control
The SMF shall contain mechanisms for avoiding and handling overload situations. This can include the following measures: - SMF overload control that could result in rejections of NAS requests. The SMF overload control may be activated by SMF due to congestion situation at SMF e.g. configuration, by a restart or recover...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.19.7 NAS level congestion control
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23.501
5.19.7.1 General
NAS level congestion control may be applied in general (i.e. for all NAS messages), per DNN, per S-NSSAI, per DNN and S-NSSAI, or for a specific group of UEs. NAS level congestion control is achieved by providing the UE a back-off time. To avoid that large amounts of UEs initiate deferred requests (almost) simultaneous...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.19.7.2 General NAS level congestion control
This clause only applies to NAS Mobility Management congestion control. Under general overload conditions the AMF may reject NAS messages from UEs using any 5G-AN. When a NAS request is rejected, a Mobility Management back-off time may be sent by the AMF to the UE. While the Mobility Management back-off timer is runnin...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.19.7.3 DNN based congestion control
DNN based congestion control is designed for the purpose of avoiding and handling of NAS SM signalling congestion for the UEs with a back-off timer associated with or without a DNN regardless of the presence of an S-NSSAI. Both UE and 5GC shall support the functionality to enable DNN based congestion control. SMFs may ...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.19.7.4 S-NSSAI based congestion control
S-NSSAI based congestion control is designed for the purpose of avoiding and handling of NAS signalling congestion for the UEs with back-off timer associated with or without an S-NSSAI regardless of the presence of a DNN. The UE associates the received back-off time with the S-NSSAI and DNN (i.e. no S-NSSAI and no DNN,...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.19.7.5 Group specific NAS level congestion control
The group specific NAS level congestion control applies to a specific group of UEs. Group specific NAS level congestion control is performed at the 5GC only and it is transparent to UE. The AMF or SMF or both may apply NAS level congestion control for a UE associated to an Internal-Group Identifier (see clause 5.9.7). ...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.19.7.6 Control Plane data specific NAS level congestion control
Under overload conditions the AMF may restrict requests from UEs for data transmission via Control Plane CIoT 5GS Optimisation. A Control Plane data back-off timer may be returned by the AMF (e.g. in Registration Accept messages, Service Reject message or Service Accept message). While the Control Plane data back-off t...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.20 External Exposure of Network Capability
The Network Exposure Function (NEF) supports external exposure of capabilities of network functions. External exposure can be categorized as Monitoring capability, Provisioning capability, Policy/Charging capability, Analytics reporting capability and Member UE selection capability. The Monitoring capability is for mon...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.21 Architectural support for virtualized deployments
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5.21.0 General
5GC supports different virtualized deployment scenarios, including but not limited to the options below: - A Network Function instance can be deployed as distributed, redundant, stateless and scalable NF instance that provides the services from several locations and several execution instances in each location. - This ...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.21.1 Architectural support for N2
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5.21.1.1 TNL associations
5G-AN node shall have the capability to support multiple TNL associations per AMF, i.e. AMF name. An AMF shall provide the 5G-AN node with the weight factors for each TNL association of the AMF. The AMF shall be able to request the 5G-AN node to add or remove TNL associations to the AMF. The AMF shall be able to indica...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.21.1.2 NGAP UE-TNLA-binding
While a UE is in CM-Connected state the 5G-AN node shall maintain the same NGAP UE-TNLA-binding (i.e. use the same TNL association and same NGAP association for the UE) unless explicitly changed or released by the AMF. An AMF shall be able to update the NGAP UE-TNLA-binding (i.e. change the TNL association for the UE) ...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.21.1.3 N2 TNL association selection
The 5G-AN node shall consider the following factors for selecting a TNL association for the AMF for the initial N2 message e.g. N2 INITIAL UE MESSAGE: - Availability of candidate TNL associations. - Weight factors of candidate TNL associations. The AMF may use any TNL association intended for non-UE associated signalli...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.21.2 AMF Management
fbecc7f0dcf9784c6066646052ab0c0e
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5.21.2.1 AMF Addition/Update
The 5G System should support establishment of association between AMF and 5G-AN node. A new AMF can be added to an AMF set and association between AMF and GUAMI can be created and/or updated as follows: - AMF shall be able to dynamically update the NRF with the new or updated GUAMI(s) to provide mapping between GUAMI(s...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.21.2.2 AMF planned removal procedure
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5.21.2.2.1 AMF planned removal procedure with UDSF deployed
An AMF can be taken graciously out of service as follows: - If an UDSF is deployed in the network, then the AMF stores the context for registered UE(s) in the UDSF. The UE context includes the AMF UE NGAP ID that is unique per AMF set. In order for the AMF planned removal procedure to work graciously, 5G-S-TMSI shall b...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.21.2.2.2 AMF planned removal procedure without UDSF
An AMF can be taken graciously out of service as follows: - The AMF can forward registered UE contexts, UE contexts grouped by the same GUAMI value, to target AMF(s) within the same AMF set, including the source AMF name used for redirecting UE's MT transaction. The UE context includes the per AMF Set unique AMF UE NGA...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.21.2.3 Procedure for AMF Auto-recovery
In order to try and handle AMF failure in a graceful manner (i.e. without impacting the UE), AMF can either back up the UE contexts in UDSF, or per GUAMI granularity in other AMFs (serving as backup AMF for the indicated GUAMI). NOTE 1: Frequency of backup is left to implementation. For deployments without UDSF, for ea...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.21.3 Network Reliability support with Sets
fbecc7f0dcf9784c6066646052ab0c0e
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5.21.3.1 General
A Network Function instance can be deployed such that several network function instances are present within an NF Set to provide distribution, redundancy and scalability together as a Set of NF instances. The same is also supported for NF Services. This can be achieved when the equivalent NFs and NF Services share the ...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.21.3.2 NF Set and NF Service Set
Equivalent Control Plane NFs may be grouped into NF Sets, e.g. several SMF instances are grouped into an SMF Set. NFs within a NF Set are interchangeable because they share the same context data and may be deployed in different locations, e.g. different data centres. In the case of SMF, multiple instances of SMFs withi...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.21.3.3 Reliability of NF instances within the same NF Set
The NF producer instance is the NF instance which host the NF Service Producer. When the NF producer instance is not available, another NF producer instance within the same NF Set is selected. For Direct Communication mode, the NF Service consumer may subscribe to status change notifications of NF instance from the NRF...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.21.3.4 Reliability of NF Services
When multiple NF Service instances within a NF Service Set are exposed to the NF Service consumer or SCP and the failure of NF Service instance is detected or notified by the NRF, i.e. it is not available anymore, the NF Service consumer or SCP selects another NF Service instance of the same NF Service Set within the N...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.21.4 Network Function/NF Service Context Transfer
fbecc7f0dcf9784c6066646052ab0c0e
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5.21.4.1 General
Network Function/NF Service Context Transfer Procedures allow transfer of Service Context of a NF/NF Service from a Source NF/NF Service Instance to the Target NF/NF Service Instance e.g. before the Source NF/NF Service can gracefully close its NF/NF Service. Service Context Transfer procedures are supported as specifi...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.22 System Enablers for priority mechanism
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5.22.1 General
The 5GS and the 5G QoS model allow classification and differentiation of specific services such as listed in clause 5.16, based on subscription-related and invocation-related priority mechanisms. These mechanisms provide abilities such as invoking, modifying, maintaining and releasing QoS Flows with priority and delive...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.22.2 Subscription-related Priority Mechanisms
Subscription-related mechanisms which are always applied: - (R)AN: During initial Access Network RRC Connection Establishment procedure or RRC Connection Resume procedure, the Establishment Cause or Resume Cause, respectively is set to indicate that special treatment is to be applied by the (R)AN in the radio resource ...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.22.3 Invocation-related Priority Mechanisms
The generic mechanisms used based on invocation-related Priority Mechanisms for prioritised services are based an interaction with an Application Function and between the Application Function and the PCF over Rx/N5 interface. These mechanisms apply to mobile originated as well as mobile terminated SIP call/sessions (cl...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.22.4 QoS Mechanisms applied to established QoS Flows
Mechanisms applied to established QoS Flows: - (R)AN: QoS Flows requested in the Xn "Handover Request" or N2 "Handover Request" which are marked as entitled to priority by virtue of inclusion of an ARP value from the set allocated by the Service Provider for prioritised services are given priority over requests for QoS...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.23 Supporting for Asynchronous Type Communication
Asynchronous type communication (ATC) enables 5GC to delay synchronizing UE context with the UE, so as to achieve an efficient signalling overhead and increase system capacity. The support of ATC is optional for the AMF. 5GC supports asynchronous type communication with the following functionality: - Capability to stor...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.24 3GPP PS Data Off
This feature, when activated by the user, prevents traffic via 3GPP access of all IP packets, Unstructured and Ethernet data except for those related to 3GPP PS Data Off Exempt Services. The 3GPP PS Data Off Exempt Services are a set of operator services, defined in TS 22.011 [25] and TS 23.221 [23], that are the only ...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.25 Support of OAM Features
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.25.1 Support of Tracing: Signalling Based Activation/Deactivation of Tracing
5GS supports tracing as described in TS 32.421 [66]. 5GS support may include subscriber tracing (tracing targeting a SUPI) or equipment tracing (tracing targeting a PEI) but also other forms of tracing further described in TS 32.421 [66] and TS 32.422 [192]. NOTE 1: TS 23.501 / TS 23.502 [3] / TS 23.503 [45] only descr...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.25.2 Support of OAM-based 5G VN group management
5GS supports 5G LAN-type service as defined in clause 5.29. 5G LAN-type service includes the 5G VN group management that can be configured by a network administrator. The parameters for 5G VN group is defined in clause 5.29. The 5G VN group parameters about a UE may be configured in subscription data of the UE and deli...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.25.3 Signalling Based Activation of QoE Measurement Collection
5GS may support QoE Measurement Collection (QMC) as described in TS 28.405 [190]. 5GS may support Signalling based activation and Management based activation as specified in TS 38.300 [27] and TS 28.405 [190]. To enable signalling based activation in NR, the QMC Configuration information is configured in subscription d...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.26 Configuration Transfer Procedure
The purpose of the Configuration Transfer is to enable the transfer of information between two RAN nodes at any time via NG interface and the Core Network. An example of application is to exchange the RAN node's IP addresses in order to be able to use Xn interface between the NG-RAN node for Self-Optimised Networks (SO...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.26.1 Architecture Principles for Configuration Transfer
Configuration Transfer between two RAN node provides a generic mechanism for the exchange of information between applications belonging to the RAN nodes. In order to make the information transparent for the Core Network, the information is included in a transparent container that includes source and target RAN node add...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.26.2 Addressing, routing and relaying
fbecc7f0dcf9784c6066646052ab0c0e
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5.26.2.1 Addressing
All the Configuration Transfer messages contain the addresses of the source and destination RAN nodes. An NG-RAN node is addressed by the Target NG-RAN node identifier.
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.26.2.2 Routing
The following description applies to all the Configuration Transfer messages used for the exchange of the transparent container. The source RAN node sends a message to its core network node including the source and destination addresses. The AMF uses the destination address to route the message to the correct AMF via t...
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.26.2.3 Relaying
The AMF performs relaying between N2 and N14 messages as described in TS 38.413 [34], TS 29.518 [71].
fbecc7f0dcf9784c6066646052ab0c0e
23.501
5.27 Enablers for Time Sensitive Communications, Time Synchronization and Deterministic Networking
fbecc7f0dcf9784c6066646052ab0c0e
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5.27.0 General
This clause describes 5G System features that can be used independently or in combination to enable time-sensitive communication, time synchronization and deterministic networking: - Delay-critical GBR; - A hold and forward mechanism to schedule traffic as defined in IEEE Std 802.1Q [98] for Ethernet PDU Sessions in DS...
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5.27.1 Time Synchronization
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5.27.1.1 General
For supporting time synchronization service, the 5GS is configured to operate in one or multiple PTP instances and to operate in one of the following modes (if supported) for each PTP instance: 1) as time-aware system as described in IEEE Std 802.1AS [104], 2) as Boundary Clock as described in IEEE Std 1588 [126], prov...
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23.501
5.27.1.2 Distribution of timing information
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5.27.1.2.1 Distribution of 5G internal system clock
The 5G internal system clock shall be made available to all user plane nodes in the 5G system. The UPF and NW-TT may get the 5G internal system clock via the underlying PTP compatible transport network with mechanisms outside the scope of 3GPP. The 5G internal system clock shall be made available to UE with signalling ...
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23.501
5.27.1.2.2 Distribution of grandmaster clock and time-stamping
5.27.1.2.2.1 Distribution of gPTP Sync and Follow_Up messages The mechanisms for distribution of TSN GM clock and time-stamping described in this clause are according to IEEE Std 802.1AS [104]. NOTE 1: It means Externally-observable behaviour of the 5GS bridge needs to comply with IEEE Std 802.1AS [104]. For downlink T...
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23.501
5.27.1.3 Support for multiple (g)PTP domains
This clause describes support for multiple domains for gPTP and PTP and for GM clocks connected to DS-TT and NW-TT and only applies if DS-TT and NW-TT support the related functionality. PTP support and support of gPTP for GM clocks connected to DS-TT by DS-TT and NW-TT may be determined as described in clause K.2.1. Ea...
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23.501
5.27.1.4 DS-TT and NW-TT Time Synchronization functionality
This clause describes the support of Time Synchronization functionality supported by the 5G System. Synchronization between UPF/NW-TT and NG-RAN is outside scope of 3GPP. DS-TT and NW-TT may support the following PTP instance types: - Boundary Clock as defined in IEEE Std 1588 [126] as described in clause 5.27.1.1; - E...
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23.501
5.27.1.5 Detection of (g)PTP Sync and Announce timeouts
The procedure described in this clause is applicable when the PTP instance in 5GS is configured to operate as a time-aware system or as a Boundary Clock and the PTP grandmaster is external to the 5GS and the BMCA procedure (Method a) is used as described in clause 5.27.1.6. The NW-TT processes Announce messages accordi...
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23.501
5.27.1.6 Distribution of Announce messages and best master clock selection
The procedure described in this clause is applicable if DS-TT and NW-TT support operating as a Boundary Clock described in IEEE Std 1588 [126] or as a time-aware system (support of the IEEE 802.1AS [104] PTP profile) and when the PTP instance in 5GS is configured to operate as a time-aware system or as a Boundary Clock...
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23.501
5.27.1.7 Support for PTP grandmaster function in 5GS
The 5GS that is configured to operate as a time-aware system or Boundary Clock may support acting as a PTP grandmaster for a (g)PTP domain. The configuration of PTP instances in DS-TT and NW-TT for PTP grandmaster function is described in clause K.2. The following options may be supported (per DS-TT) for the 5GS to gen...
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5.27.1.8 Exposure of Time Synchronization
5G System supports time synchronization service that can be activated and deactivated by AF. Exposure of time synchronization comprises the following capabilities: - The AF may learn 5GS and/or UE availability and capabilities for time synchronization service. - The AF controls activation and deactivation of the time s...
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5.27.1.9 Support for derivation of Uu time synchronization error budget
The AF may request a specific time synchronization error budget when requesting a time synchronization service employing the (g)PTP-based or 5G access stratum-based time distribution method. If the AF includes a time synchronization error budget in its request, the TSCTSF uses it to derive an error budget available for...
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5.27.1.10 Support for coverage area filters for time synchronization service
This feature enables the AF to request time synchronization service for a UE or a group of UEs in a specific geographical area (so called coverage area). The requested coverage area contains a list of Tracking Area (TA) or a geographical area (e.g. a civic address or shapes that the NEF transforms to list of TAs based ...
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5.27.1.11 Controlling time synchronization service based on the Subscription
The distribution of timing information, 5G access stratum-based time distribution and (g)PTP-based time distribution, for a UE may be controlled based on subscription data stored in the UDM. The (g)PTP-based or 5G access stratum-based time synchronization service may be provided to a UE based on the UE's subscription w...
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5.27.1.12 Support for network timing synchronization status monitoring
While the time synchronization service is offered by the 5GS, based on 5G access stratum-based time distribution or (g)PTP-based time distribution, the network timing synchronization status of the nodes involved in the operation (e.g. gNBs and/or UPF/NW-TTs) may change. gNBs and UPF/NW-TT can detect timing synchronizat...
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5.27.2 TSC Assistance Information (TSCAI) and TSC Assistance Container (TSCAC)
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5.27.2.1 General
TSC Assistance Information (TSCAI) is defined in Table 5.27.2-1 and describes TSC traffic characteristics for use in the 5G System. It can also be used for services such as XR services (AR/VR applications) and interactive media services as specified in clause 5.37. TSCAI may be used by the 5G-AN, if provided by SMF. Th...
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5.27.2.2 TSC Assistance Container determination based on PSFP
In the case of integration with IEEE TSN network, the TSN AF determines a TSC Assistance Container (defined in Table 5.27.2-2) and provides it to the PCF. The determination of TSC Assistance Container based on Per-Stream Filtering and Policing (PSFP) information applies only to Ethernet type PDU Sessions. NOTE 1: This ...