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fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.2.6.3 SCP profile | SCP profile maintained in an NRF includes the following information:
- SCP ID.
- FQDN or IP address of SCP.
- Indication that the profile is of an SCP (e.g. NF type parameter set to type SCP).
- SCP capacity information.
- SCP load information.
- SCP priority.
- Location information for the SCP (see locality in clause 6.1.6.2.2 of TS 29.510 [58]).
- Served Location(s) (see servingScope in clause 6.1.6.2.2 of TS 29.510 [58]).
- Network Slice related Identifier(s) e.g. S-NSSAI, NSI ID.
- Remote PLMNs reachable through SCP.
- Endpoint addresses accessible via the SCP.
- NF sets of NFs served by the SCP.
- SCP Domain the SCP belongs to. If an SCP belongs to more than one SCP Domain, the SCP will be able bridge these domains, i.e. sending messages between these domains.
- If the SCP acts as service producer: Names of supported services, NF Service Set ID of the NF service instance, NF Specific Service authorization information.
NOTE: Service definition defines optional and mandatory parameters, see TS 23.502 [3]. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.2.7 UDM | The Unified Data Management (UDM) includes support for the following functionality:
- Generation of 3GPP AKA Authentication Credentials.
- User Identification Handling (e.g. storage and management of SUPI for each subscriber in the 5G system).
- Support of de-concealment of privacy-protected subscription identifier (SUCI).
- Access authorization based on subscription data (e.g. roaming restrictions).
- UE's Serving NF Registration Management (e.g. storing serving AMF for UE, storing serving SMF for UE's PDU Session).
- Support to service/session continuity e.g. by keeping SMF/DNN assignment of ongoing sessions.
- MT-SMS delivery support.
- Lawful Intercept Functionality (especially in outbound roaming case where UDM is the only point of contact for LI).
- Subscription management.
- SMS management.
- 5G-VN group management handling.
- Support of external parameter provisioning (Expected UE Behaviour parameters or Network Configuration parameters).
- Support for the Disaster Roaming as described in clause 5.40.
- Support for the control of time synchronization service based on subscription data as described in clause 5.27.1.11.
To provide this functionality, the UDM uses subscription data (including authentication data) that may be stored in UDR, in which case a UDM implements the application logic and does not require an internal user data storage and then several different UDMs may serve the same user in different transactions.
NOTE 1: The interaction between UDM and HSS, when they are deployed as separate network functions, is defined in TS 23.632 [102] and TS 29.563 [103] or it is implementation specific.
NOTE 2: The UDM is located in the HPLMN of the subscribers it serves and access the information of the UDR located in the same PLMN. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.2.8 AUSF | The Authentication Server Function (AUSF) supports the following functionality:
- Supports authentication for 3GPP access and untrusted non-3GPP access as specified in TS 33.501 [29].
- Supports authentication of UE for a Disaster Roaming service as specified in TS 33.501 [29]. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.2.9 N3IWF | The functionality of N3IWF in the case of untrusted non-3GPP access includes the following:
- Support of IPsec tunnel establishment with the UE: The N3IWF terminates the IKEv2/IPsec protocols with the UE over NWu and relays over N2 the information needed to authenticate the UE and authorize its access to the 5G Core Network.
- Termination of N2 and N3 interfaces to 5G Core Network for control - plane and user-plane respectively.
- Relaying uplink and downlink control-plane NAS (N1) signalling between the UE and AMF.
- Handling of N2 signalling from SMF (relayed by AMF) related to PDU Sessions and QoS.
- Establishment of IPsec Security Association (IPsec SA) to support PDU Session traffic.
- Relaying uplink and downlink user-plane packets between the UE and UPF. This involves:
- De-capsulation/ encapsulation of packets for IPSec and N3 tunnelling.
- Enforcing QoS corresponding to N3 packet marking (e.g. DSCP), taking into account QoS requirements associated to such marking received over N2. QoS includes 5QI, the Priority Level (if explicitly signalled) and optionally, the ARP priority level.
NOTE: Based on operator policy and/or regional/national regulations, the N3IWF can apply a different DSCP value to the outer ESP tunnel packet than the DSCP value of the inner IP packet.
- Packet marking, e.g. setting the DSCP value based on the Establishment cause on N2 and based on 5QI, the Priority Level (if explicitly signalled) and optionally, the ARP priority level on N3.
- Local mobility anchor within untrusted non-3GPP access networks using MOBIKE per IETF RFC 4555 [57].
- Supporting AMF selection.
- Support of ECN marking for L4S: The SMF, if applicable, provides ECN marking request per QoS flow level to the N3IWF as part of PDU session management procedures.
- When ECN marking for L4S at N3IWF is enabled for downlink or uplink, the N3IWF should set the Congestion Experienced (CE) codepoint in downlink or uplink as per the recommendations in IETF RFC 9330 [159], IETF RFC 9331 [160], IETF RFC 9332 [161], IETF RFC 6040 [198] and IETF RFC 9599 [199].
- Optionally, supporting PDU Set based Handling as defined in clause 5.37.5.
6.2.9A TNGF
The functionality of TNGF in the case of trusted non-3GPP access includes the following:
- Terminates the N2 and N3 interfaces.
- Terminates the EAP-5G signalling and behaves as authenticator when the UE attempts to register to 5GC via the TNAN.
- Implements the AMF selection procedure.
- Transparently relays NAS messages between the UE and the AMF, via NWt.
- Handles N2 signalling with SMF (relayed by AMF) for supporting PDU sessions and QoS.
- Transparently relays PDU data units between the UE and UPF(s).
- Implements a local mobility anchor within the TNAN.
- Packet marking in the downlink and the uplink on N2 and N3, as for the N3IWF (clause 6.2.9).
- ECN marking for L4S, as for N3IWF (clause 6.2.9).
- Optionally, supporting PDU Set based Handling as defined in clause 5.37.5. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.2.10 AF | The Application Function (AF) interacts with the 3GPP Core Network in order to provide services, for example to support the following:
- Application Function influence on traffic routing (see clause 5.6.7);
- Application Function influence on Service Function Chaining (see clause 5.6.16.2);
- Accessing Network Exposure Function (see clause 5.20);
- Interacting with the Policy and charging control framework (see clause 5.14);
- Time synchronization service (see clause 5.27.1.8);
- IMS interactions with 5GC (see clause 5.16).
- Support PDU Set Handling as defined in clause 5.37.5.
- Support Vertical Federated Learning (VFL) as VFL Server or VFL Client (see clause 5.4 of TS 23.288 [50]).
Based on operator deployment, Application Functions considered to be trusted by the operator can be allowed to interact directly with relevant Network Functions.
Application Functions not allowed by the operator to access directly the Network Functions shall use the external exposure framework (see clause 7.3) via the NEF to interact with relevant Network Functions.
The functionality and purpose of Application Functions are only defined in this specification with respect to their interaction with the 3GPP Core Network. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.2.11 UDR | The Unified Data Repository (UDR) supports the following functionality:
- Storage and retrieval of subscription data by the UDM.
- Storage and retrieval of policy data by the PCF.
- Storage and retrieval of structured data for exposure.
- Application data (including Packet Flow Descriptions (PFDs) for application detection, AF request information for multiple UEs, 5G-VN group information for 5G-VN management, Non-3GPP Device Identifier Information).
- Storage and retrieval of NF Group ID corresponding to subscriber identifier (e.g. IMPI, IMPU, SUPI).
The Unified Data Repository is located in the same PLMN as the NF service consumers storing in and retrieving data from it using Nudr. Nudr is an intra-PLMN interface.
NOTE 1: Deployments can choose to collocate UDR with UDSF. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.2.12 UDSF | The UDSF is an optional function that supports the following functionality:
- Storage and retrieval of information as unstructured data by any NF. Notify a NF consumer if information validity has expired.
- Timer service to any NF.
NOTE 1: Structured data in this specification refers to data for which the structure is defined in 3GPP specifications. Unstructured data refers to data for which the structure is not defined in 3GPP specifications.
NOTE 2: Deployments can choose to collocate UDSF with UDR. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.2.13 SMSF | The SMSF supports the following functionality to support SMS over NAS:
- SMS management subscription data checking and conducting SMS delivery accordingly.
- SM-RP/SM-CP with the UE (see TS 24.011 [6]).
- Relay the SM from UE toward SMS-GMSC/IWMSC/SMS-Router.
- Relay the SM from SMS-GMSC/IWMSC/SMS-Router toward the UE.
- SMS charging.
- Lawful Interception.
- Interaction with AMF and SMS-GMSC for notification procedure that the UE is unavailable for SMS transfer (i.e, notifies SMS-GMSC to inform UDM when UE is unavailable for SMS). |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.2.14 NSSF | The Network Slice Selection Function (NSSF) supports the following functionality:
- Selecting the set of Network Slice instances serving the UE;
- Determining the Allowed NSSAI and, if needed, the mapping to the Subscribed S-NSSAIs;
- Determining the Configured NSSAI and, if needed, the mapping to the Subscribed S-NSSAIs;
- Determining the AMF Set to be used to serve the UE, or, based on configuration, a list of candidate AMF(s), possibly by querying the NRF;
- The NSSF may provide support for Network Slice restriction and Network Slice instance restriction based on NWDAF analytics.
- Determining whether an S-NSSAI has to be replaced and providing to the AMF the indication that the S-NSSAI is unavailable and a corresponding Alternative S-NSSAI, e.g. based on received NWDAF analytics (e.g. for Service Experience for a Network Slice or Slice load level), or local trigger from the OAM system. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.2.15 5G-EIR | The 5G-EIR is an optional network function that supports the following functionality:
- Check the status of PEI (e.g. to check that it has not been prohibited). |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.2.16 LMF | The functionality of LMF is defined in clause 4.3.8 of TS 23.273 [87].
6.2.16A GMLC
The functionality of GMLC is defined in clause 4.3.8 of TS 23.273 [87]. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.2.17 SEPP | The Security Edge Protection Proxy (SEPP) is a non-transparent proxy and supports the following functionality:
- Message filtering and policing on inter-PLMN control plane interfaces.
NOTE: The SEPP protects the connection between Service Consumers and Service Producers from a security perspective, i.e. the SEPP does not duplicate the Service Authorization applied by the Service Producers as specified in clause 7.1.4.
- Topology hiding.
Detailed functionality of SEPP, related flows and the N32 reference point, are specified in TS 33.501 [29].
The SEPP applies the above functionality to every Control Plane message in inter-PLMN signalling, acting as a service relay between the actual Service Producer and the actual Service Consumer. For both Service Producer and Consumer, the result of the service relaying is equivalent to a direct service interaction. Every Control Plane message in inter-PLMN signalling between the SEPPs may pass via IPX entities. More details on SEPPs and the IPX entities are described in TS 29.500 [49] and TS 33.501 [29]. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.2.18 Network Data Analytics Function (NWDAF) | The Network Data Analytics Function (NWDAF) includes one or more of the following functionalities:
- Support data collection from NFs and AFs;
- Support data collection from OAM;
- Support retrieval of information from data repositories (e.g. UDR via UDM for subscriber-related information or via NEF(PFDF) for PFD information);
- Support data collection of location information from LCS system;
- NWDAF service registration and metadata exposure to NFs and AFs;
- Support analytics information provisioning to NFs and AFs;
- Support analytics collection from MDAF;
- Support Machine Learning (ML) model training and provisioning to NWDAF containing AnLF, NWDAF containing MTLF, or LMF;
- Support ML Model storage to and retrieval from ADRF;
- Support bulked data related to Analytics ID(s) provisioning for NFs;
- Support accuracy information about Analytics IDs provisioning for NFs;
- Support accuracy information or accuracy degradation about ML model provisioning for NFs;
- Support roaming exchange capability to exchange data and analytics between PLMNs;
- Support Horizontal Federated Learning (HFL) to train an ML model among multiple NWDAFs (containing MTLF);
- Support Vertical Federated Learning (VFL) as VFL Server or VFL Client.
The details of the NWDAF functionality are defined in TS 23.288 [86].
NOTE 1: Some or all of the NWDAF functionalities can be supported in a single instance of an NWDAF.
NOTE 2: NWDAF functionality beyond its support for Nnwdaf is out of scope of 3GPP. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.2.19 SCP | The Service Communication Proxy (SCP) includes one or more of the following functionalities. Some or all of the SCP functionalities may be supported in a single instance of an SCP:
- Indirect Communication (see clause 7.1.1 for details).
- Delegated Discovery (see clauses 7.1.1 and 6.3.1 for details).
- Message forwarding and routing to destination NF/NF service.
- Message forwarding and routing to a next hop SCP.
- Communication security (e.g. authorization of the NF Service Consumer to access the NF Service Producer API), load balancing, monitoring, overload control, etc.
- Optionally interact with UDR, to resolve the UDM Group ID/UDR Group ID/AUSF Group ID/PCF Group ID/CHF Group ID/HSS Group ID based on UE identity, e.g. SUPI or IMPI/IMPU (see clause 6.3.1 for details).
- Optionally interact with NF and NWDAF, to support network abnormal behaviours (i.e. signalling storm) mitigation and prevention.
- Optionally expose events related to service-agnostic characteristics of messages the SCP passes such as Load, Delay, Error rate, number of messages.
NOTE 1: The use of received analytic information for routing optimisation/efficiency at SCP can be left to implementation.
NOTE 2: NWDAF can leverage service-agnostic characteristics of messages provided by SCP.
NOTE 3: Communication security, e.g. authorization of the NF Service Consumer to access the NF Service Producer's API is specified in TS 33.501 [29].
NOTE 4: Load balancing, monitoring, overload control functionality provided by the SCP is left up to implementation.
- Network protection (for example, SCP may take measures to prevent or mitigate network signalling overload based on analytics from NWDAF (e.g. signalling storm analytics, NF load analytics).
The SCP may be deployed in a distributed manner.
NOTE 3: More than one SCP can be present in the communication path between NF Services.
SCPs can be deployed at PLMN level, shared-slice level and slice-specific level. It is left to operator deployment to ensure that SCPs can communicate with relevant NRFs.
In order to enable SCPs to route messages through several SCPs (i.e. next SCP hop discovery, see clause 6.3.16), an SCP may register its profile in the NRF. Alternatively, local configuration may be used. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.2.20 W-AGF | The functionality of W-AGF is specified in TS 23.316 [84]. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.2.21 UE radio Capability Management Function (UCMF) | The UCMF is used for storage of dictionary entries corresponding to either PLMN-assigned or Manufacturer-assigned UE Radio Capability IDs. An AMF may subscribe with the UCMF to obtain from the UCMF new values of UE Radio Capability ID that the UCMF assigns for the purpose of caching them locally.
Provisioning of Manufacturer-assigned UE Radio Capability ID entries in the UCMF is performed from an AF that interacts with the UCMF either directly or via the NEF (or via Network Management) using a procedure defined in TS 23.502 [3]. A UCMF that serves both EPS and 5GS shall require provisioning the UE Radio Capability ID with the TS 36.331 [51] format or TS 38.331 [28] format or both the formats of the UE radio capabilities.
The UCMF also assigns the PLMN-assigned UE Radio Capability ID values.
Each PLMN-assigned UE Radio Capability ID is also associated to the TAC of the UE model(s) that it is related to. When an AMF requests the UCMF to assign a UE Radio Capability ID for a set of UE radio capabilities, it indicates the TAC of the UE that the UE Radio Capability information is related to.
The UCMF stores a Version ID value for the PLMN assigned UE Radio Capability IDs so it is included in the PLMN assigned UE Radio Capability IDs it assigns. This shall be configured in the UCMF.
The UCMF may be provisioned with a dictionary of Manufacturer-assigned UE Radio Capability IDs which include a "Vendor ID" that applies to the Manufacturers of these UE and a list of TACs for which the PLMN has obtained-Manufacturer-assigned UE Radio Capability IDs.
A PLMN-assigned UE Radio Capability IDs is kept in the UCMF storage as long as it is associated with at least a TAC value. When a TAC value is related to a UE model that is earmarked for operation based on Manufacturer assigned UE Radio Capability IDs, this TAC value is disassociated in the UCMF from any PLMN assigned UE Radio Capability IDs.
For the case that the PLMN is configured to store PLMN assigned IDs in the Manufacturer Assigned operation requested list defined in clause 4.4.1a, the UCMF does not remove from storage any PLMN assigned UE Radio Capability ID no longer used and rather quarantines it to avoid any future reassignment.
A UCMF dictionary entry shall include also the related UE Radio Capability for Paging for each RAT. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.2.22 TWIF | The functionality of Trusted WLAN Interworking Function (TWIF) is specified in clause 4.2.8.5.3. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.2.23 NSSAAF | The Network Slice-specific and SNPN Authentication and Authorization Function (NSSAAF) supports the following functionality:
- Support for Network Slice-Specific Authentication and Authorization as specified in TS 23.502 [3] with a AAA Server (AAA-S). If the AAA-S belongs to a third party, the NSSAAF may contact the AAA-S via a AAA proxy (AAA-P).
- Support for access to SNPN using credentials from Credentials Holder using AAA server (AAA-S) as specified in clause 5.30.2.9.2 or using credentials from Default Credentials Server using AAA server (AAA-S) as specified in clause 5.30.2.10.2. If the Credentials Holder or Default Credentials Server belongs to a third party, the NSSAAF may contact the AAA server via a AAA proxy (AAA-P).
NOTE: When the NSSAAF is deployed in a PLMN, the NSSAAF supports Network Slice-Specific Authentication and Authorization, while when the NSSAAF is deployed in a SNPN the NSSAAF can support Network Slice-Specific Authentication and Authorization and/or the NSSAAF can support access to SNPN using credentials from Credentials Holder. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.2.24 DCCF | The Data Collection Coordination Function (DCCF) supports the following functionality:
- Determining Data Sources that can provide data for a received data request.
- Determining whether data is already being collected from a data source.
- Instructing a Messaging Framework to send data to consumers or notification endpoints.
- Instructing a Messaging Framework to do formatting and processing of the data sent via the Messaging Framework.
- Formatting and processing of data.
- Sending data to consumers or notification endpoints.
- Registering NWDAFs and ADRFs that are already receiving data from a Data Source.
The DCCF functionality is specified in TS 23.288 [86]. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.2.25 MFAF | The Messaging Framework Adaptor Function (MFAF) supports the following functionality:
- Interfacing with a DCCF that controls how a messaging framework will process, format and send data to consumers or notification endpoints.
- Receiving data from Data Sources via services offered by those Data Sources.
- Sending data received from Data Sources to a messaging framework (outside the scope of 3GPP).
- Receiving data from a messaging framework (outside the scope of 3GPP).
- Processing, formatting and sending data to specified consumers or notification endpoints.
NOTE: The internal logic of Messaging Framework is outside the scope of 3GPP, only MFAF and the interface between MFAF and other 3GPP defined NF is under 3GPP scope.
The MFAF functionality is specified in TS 23.288 [86]. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.2.26 ADRF | The Analytics Data Repository Function (ADRF) supports the following functionality:
- Storage and retrieval of analytics generated by NWDAFs and collected data.
- Storage and retrieval of ML model files trained by NWDAFs containing MTLF.
The Analytics Data Repository Function (ADRF) is specified in TS 23.288 [86]. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.2.27 MB-SMF | The functionality of MB-SMF is specified in TS 23.247 [129].
6.2.27a MB-UPF
The functionality of MB-UPF is specified in TS 23.247 [129].
6.2.27b MBSF
The functionality of MBSF is specified in TS 23.247 [129].
6.2.27c MBSTF
The functionality of MBSTF is specified in TS 23.247 [129]. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.2.28 NSACF | The Network Slice Admission Control Function (NSACF) supports the following functionality:
- Support of monitoring and controlling the number of registered UEs per network slice.
- Support of monitoring and controlling the number of UEs with at least one PDU Session/PDN Connection per network slice in case of EPC interworking.
- Support of monitoring and controlling the number of established PDU Sessions per network slice.
- Support of event based Network Slice status notification and reports to a consumer NF.
- Acting as a Centralized NSACF in PLMNs deploying a centralized architecture as described in clause 5.15.11.0.
- Support of different type of NSAC modes for roaming UEs for the number of UEs per network slice.
- Support of different type of NSAC modes for roaming UEs for the number of PDU Sessions per network slice.
- Acting as a Primary NSACF in PLMNs deploying a hierarchal architecture as described in clause 5.15.11.0.
The details of the NSACF functionality are defined in clause 5.15.11. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.2.29 TSCTSF | The Time Sensitive Communication and Time Synchronization Function (TSCTSF) supports the following functionality:
- Associating the time synchronization service request (see clause 5.27.1.8) from the NF consumer to the AF sessions with the PCF (the session between the PCF and TSCTSF).
- Controlling time synchronization service request from the NF consumer, (g)PTP-based time distribution and ASTI-based time distribution based on subscription data. The TSCTSF may be pre-configured with one or several PTP instance configurations. For each PTP instance configuration, it may contain:
- a reference to the PTP instance configuration.
- PTP profile.
- PTP domain.
- Detecting and reporting time synchronization service status based on NG-RAN and UPF/NW-TT timing synchronization status information and reporting status updates.
- Managing the DS-TT and NW-TT via exchange of PMIC and UMIC as described in Annex K.
- Detecting availability of 5GS Bridge/Router information (including user plane node ID that applies also for IP type PDU Sessions) as reported by PCF for both Ethernet and IP type PDU Sessions (including the need to (un)subscribe 5GS Bridge/Router information Notification from PCF).
- Creating the TSC Assistance Container based on individual traffic pattern parameters from the NEF/AF or DetNet controller and providing it to the PCF.
- Determining the Requested PDB by subtracting the UE-DS-TT Residence Time from the Requested 5GS Delay provided by the NEF/AF or DetNet controller and providing the determined Requested PDB to the PCF.
- Discovering the AMFs serving the list of TA(s) that comprise the spatial validity condition from the NRF or AMFs serving the UE(s) from the UDM and subscribing to the discovered AMF(s) to receive notifications about presence of the UE in an Area of Interest.
- Discovering the AMF(s) serving a UE or a list of TA(s) and subscribing to gNB's node-level timing synchronization status.
- Obtaining gNB's and UPF's node-level timing synchronization status information as defined in clause 5.27.1.12.
- Determining the spatial validity condition from the requested coverage area by the NEF/AF and enforcing time synchronization service for the requested coverage area.
- Support for RAN feedback for BAT offset and adjusted periodicity as defined in clause 5.27.2.5.
- In the case of support of integration with IETF Deterministic Networking (as depicted in clauses 4.4.8.4 and 5.28.5), acting as a stateful translator function between a DetNet controller and 5G System Network Functions and Procedures, including the NW-TT. This includes exposing the information about the 5GS router to the DetNet controller and mapping 5GS router configuration parameters provided by the DetNet controller to 5G System parameters. The details are defined in clause 5.28.5. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.2.30 5G DDNMF | The functionality of 5G DDNMF is defined in TS 23.304 [128]. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.2.31 EASDF | The functionality of EASDF is defined in TS 23.548 [130]. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.2.32 TSN AF | The TSN AF supports control plane translator functionality for the integration of the 5GS with a TSN network, this involves e.g.:
- 5GS Bridge management.
- Port and bridge management information exchange with DS-TT or NW-TT.
- Interactions with the CNC for 5GS Bridge configuration and reporting.
- determining the TSC Assistance Container and TSN QoS information by mapping TSN Stream(s) based on IEEE standards. The traffic pattern parameter determination may be based on PSFP (IEEE Std 802.1Q [98]) as specified in Annex I, clause I.1. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.2.33 NSWOF | The NSWOF interfaces the WLAN access network using the SWa interface as defined in TS 23.402 [43] and interfaces the AUSF using the Nausf SBI performing protocol translation and AUSF discovery (see clause 6.3.4). |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.2.34 EIF | The Energy Information Function (EIF) includes support for the following functionalities:
- Collect data from OAM and 5GC NF(s) to assist the calculation of energy related information.
- Calculate the energy related information (including energy consumption information and renewable energy information) of user plane communication.
- Expose the calculated energy related information to authorized consumers. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.3 Principles for Network Function and Network Function Service discovery and selection | |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.3.1 General | The NF discovery and NF service discovery enable Core Network entities (NFs or Service Communication Proxy (SCP)) to discover a set of NF instance(s) and NF service instance(s) for a specific NF service or an NF type. NF service discovery is enabled via the NF discovery procedure, as specified in clauses 4.17.4, 4.17.5, 4.17.9 and 4.17.10 of TS 23.502 [3].
Unless the expected NF and NF service information is locally configured on the requester NF, e.g. when the expected NF service or NF is in the same PLMN as the requester NF, the NF and NF service discovery is implemented via the Network Repository Function (NRF). NRF is the logical function that is used to support the functionality of NF and NF service discovery and status notification as specified in clause 6.2.6.
NOTE 1: NRF can be colocated together with SCP e.g. for communication option D, depicted in Annex E.
In order for the requested NF type or NF service to be discovered via the NRF, the NF instance need to be registered in the NRF. This is done by sending a Nnrf_NFManagement_NFRegister containing the NF profile. The NF profile contains information related to the NF instance, such as NF instance ID, supported NF service instances (see clause 6.2.6 for more details regarding the NF profile). The registration may take place e.g. when the producer NF instance and its NF service instance(s) become operative for the first time. The NF service registration procedure is specified in clause 4.17.1 of TS 23.502 [3].
In order for the requester NF or SCP to obtain information about the NF and/or NF service(s) registered or configured in a PLMN/slice, based on local configuration the requester NF or SCP may initiate a discovery procedure with the NRF by providing the type of the NF and optionally a list of the specific service(s) it is attempting to discover. The requester NF or SCP may also provide other service parameters e.g. slicing related information. For the detailed service parameter(s) used for specific NF and NF service discovery refer to clause 5.2.7.3.2 of TS 23.502 [3]. The requester NF may also provide NF Set related information to enable reselection of NF instances within the NF set. The requester NF may also provide the required supported features of the NF.
For some Network Functions which have access to the subscription data (e.g. HSS, UDM) the NRF may need to resolve the NF Group ID corresponding to a subscriber identifier. If the NRF has no stored configuration mapping identity sets/ranges to NF Group ID locally, the NRF may retrieve the NF Group ID corresponding to a specific subscriber identifier from the UDR using the Nudr_GroupIDmap_Query service operation.
In the case of Indirect Communication, a NF Service Consumer employs an SCP which routes the request to the intended target of the request.
If the requester NF is configured to delegate discovery, the requester NF may omit the discovery procedure with the NRF and instead delegate the discovery to the SCP; the SCP will then act on behalf of the requester NF. In this case, the requester NF adds any necessary discovery and selection parameters to the request in order for the SCP to be able to do discovery and associated selection. The SCP may interact with the NRF to perform discovery and obtain discovery result and it may interact with the NRF or UDR to obtain NF Group ID corresponding to subscriber identifier.
NOTE 2: For delegated discovery of the HSS or the UDM, the SCP can rely on the NRF to discover the group of HSS/UDM instance(s) serving the provided user identity, or in some deployments the SCP can first query the UDR for the HSS/UDM Group ID for the provided user identity. It is expected that the stage 3 defines a single encoding for the user identity provided by the service consumer that can be used for both variants of delegated discovery to avoid that the service consumer needs to be aware of the SCP behaviour.
The NRF provides a list of NF instances and NF service instances relevant for the discovery criteria. The NRF may provide the IP address or the FQDN of NF instance(s) and/or the Endpoint Address(es) of relevant NF service instance(s) to the NF Consumer or SCP. The NRF may also provide NF Set ID and/or NF Service Set ID to the NF Consumer or SCP. The response contains a validity period during which the discovery result is considered valid and can be cached. The result of the NF and NF service discovery procedure is applicable to any subscriber that fulfils the same discovery criteria. The entity that does the discovery may cache the NF profile(s) received from the NF/NF service discovery procedure. During the validity period, the cached NF profile(s) may be used for NF selection for any subscriber matching the discovery criteria.
NOTE 3: Refer to TS 29.510 [58] for details on using the validity period.
In the case of Direct Communication, the requester NF uses the discovery result to select NF instance and a NF service instance that is able to provide a requested NF Service (e.g. a service instance of the PCF that can provide Policy Authorization).
In the case of Indirect Communication without Delegated Discovery, the requester NF uses the discovery result to select a NF instance while the associated NF service instance selection may be done by the requester NF and/or an SCP on behalf of the requester NF.
In both the cases above, the requester NF may use the information from a valid cached discovery result for subsequent selections (i.e. the requester NF does not need to trigger a new NF discovery procedure to perform the selection).
In the case of Indirect Communication with Delegated Discovery, the SCP will discover and select a suitable NF instance and NF service instance based on discovery and selection parameters provided by the requester NF and optional interaction with the NRF. The NRF to be used may be provided by the NF consumer as part of the discovery parameters, e.g. as a result of a NSSF query. The SCP may use the information from a valid cached discovery result for subsequent selections (i.e. the SCP does not need to trigger a new NF discovery procedure to perform the selection).
NOTE 4: In a given PLMN, Direct Communication, Indirect Communication, or both may apply.
The requester NF or SCP may subscribe to receive notifications from the NRF of a newly updated NF profile of an NF (e.g. NF service instances taken in or out of service), or newly registered de-registered NF instances. The NF/NF service status subscribe/notify procedure is defined in clauses 4.17.7 and 4.17.8 of TS 23.502 [3].
For NF and NF service discovery across PLMNs, the NRF in the local PLMN interacts with the NRF in the remote PLMN to retrieve the NF profile(s) of the NF instance(s) in the remote PLMN that matches the discovery criteria. If the NRF in the local PLMN indicated support, for the local PLMN, of indirect communication with delegated discovery with NF (re)selection at target PLMN (Model D in Annex E with SCP in target PLMN doing NF (re)selection) and/or of indirect communication without delegated discovery with NF (re)selection at target PLMN (Model C in Annex E with SCP in target PLMN doing NF (re)selection), based on operator's policy and the capabilities of the local PLMN, the NRF in the remote PLMN may also return an indication that indirect communication with delegated discovery with NF (re)selection at target PLMN is requested or that indirect communication without delegated discovery with NF (re)selection at target PLMN is requested and, for delegated discovery in target PLMN, omit NF profiles. The NRF in the local PLMN reaches the NRF in the remote PLMN by forming a remote PLMN specific query using the PLMN ID provided by the requester NF. The remote PLMN NRF may further interact with a target PLMN NRF as specified in clause 6.2.6.1. Based on operator's policy and configuration, the NRF in the local PLMN may also determine without interaction with the NRF in the remote PLMN that indirect communication with delegated discovery with NF (re)selection at target PLMN is requested for communication for that remote PLMN. The NF/NF service discovery procedure across PLMNs is specified in clauses 4.17.5, 4.17.10 and 4.17.10a of TS 23.502 [3].
NOTE 5: See TS 29.510 [58] for details on using the target PLMN ID specific query to reach the NRF in the remote PLMN.
NOTE 6: The NRF in the local PLMN can interact with NRFs in target PLMNs already before receiving related discovery requests to inquire the support of indirect communication by those target PLMNs, cache the received information and use it for subsequent discovery requests.
For topology hiding, see clause 6.2.17.
The NRF may take appropriate action, upon detection of certain local events, e.g. NF load that NF resource usage is abnormal, or from notification of subscription to signalling storm analytics to predict signalling storm from NWDAF. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.3.1.0 Principles for Binding, Selection and Reselection | Binding can be used to indicate suitable target NF producer instance(s) for NF service instance selection, reselection and routing of subsequent requests associated with a specific NF producer resource (context) and NF service. This allows the NF producer to indicate that the NF consumer, for a particular context, should be bound to an NF service instance, NF instance, NF service set or NF set depending on local policies and other criteria (e.g. at what point it is in the middle of a certain procedure, considering performance aspects etc).
Binding can also be used by the NF consumer to indicate suitable NF consumer instance(s) for notification target instance reselection and routing of subsequent notification requests associated with a specific notification subscription and for providing Binding Indication for service(s) that the NF consumer produces for the same data context and the NF service producer is subsequently likely to invoke.
The Binding Indication contains the information in Table 6.3.1.0-1.
The Routing Binding Indication may be included in Request, Subscribe or Notification messages (see clause 7.1.2). It may be used in the case of indirect communication by the SCP to route the message. The Routing Binding Indication is a copy of the information in the Binding Indication and also contains the information in Table 6.3.1.0-1.
NOTE 1: Subscription request messages can contain both a Binding Indication and a Routing Binding Indication.
The NF service producer may provide a Binding Indication to the NF service consumer as part of the Direct or Indirect Communication procedures, to be used in subsequent related service requests. The level of Binding Indication provided by the NF service producer to the NF consumer indicates if the resource in the NF service producer is either bound to NF service instance, NF instance, NF Service Set or NF set as specified in Table 6.3.1.0-1. The Binding Indication may include NF Service Set ID, NF Set ID, NF instance ID, or NF service instance ID, for use by the NF consumer or SCP for NF Service Producer (re-)selection. If the resource is created in the NF Service Producer, the NF Service Producer provides resource information which includes the endpoint address of the NF service producer. For indirect communication, the NF service consumer copies the Binding Indication into the Routing Binding Indication in Request or Subscribe message, unless the NF service consumer performs a reselection for indirect communication without delegated discovery.
During explicit or implicit notification subscription, a Binding Indication may be provided by the NF service consumer to NF service producer; the NF service consumer will also provide a Notification Endpoint. The NF service consumer may also provide a Binding Indication in response to notification requests. The level of Binding Indication provided by the NF service consumer to the NF service provider indicates if the Notification Endpoint is either bound to NF service instance, NF instance, NF Service Set or NF set as specified in Table 6.3.1.0-1. The Binding Indication shall include at least one of NF Set ID, NF instance ID, NF Service Set ID and/or NF service instance ID and may also include the service name. The NF Service Set ID, NF service instance ID and service name relate to the service of the NF service consumer that will handle the notification.
NOTE 2: The NF service can either be a standardised service as per this specification or a custom service. The custom service can be used for the sole purpose of registering endpoint address(es) to receive notifications at the NRF.
The Binding Indication is used by the NF service producer as notification sender to reselect an endpoint address and construct the Notification Endpoint, i.e. the URI where the notification is to be sent, e.g. if the provided Notification Endpoint of the NF service consumer included in the subscription cannot be reached, according to the following:
- If the service name in the Binding Indication is omitted and the binding for notification is on NF Set or NF Instance level, the endpoint address registered in the NRF at NF Profile level of the NF(s) selected according to the Binding Indication shall be used to construct a new Notification Endpoint.
- If the service name is included in the Binding Indication, an endpoint address registered in the NRF for that service in the NF profile(s) selected according to the Binding Indication shall be used to construct a new Notification Endpoint.
For indirect communication, the NF service producer copies the Binding Indication into the Routing Binding Indication that is included in the Notification request, to be used by the SCP to discover an alternative endpoint address and construct a Notification Endpoint e.g. if the Notification Endpoint that the request targets cannot be reached, according to the following:
- If the service name in the Routing Binding Indication is omitted and the binding for notification is on NF Set or NF Instance level, the endpoint address registered in the NRF at NF Profile level of the NF(s) selected according to the Binding Indication shall be used to construct a new Notification Endpoint.
- If the service name is included in the Routing Binding Indication, an endpoint address registered in the NRF for that service in the NF profile(s) selected according to the Binding Indication shall be used to construct a new Notification Endpoint.
For subscription to notifications via another network function, a separate Binding Indication for subscription related events may be provided by the NF service consumer (see clause 4.17.12.4 of TS 23.502 [3]) and if provided shall be associated with an applicability indicating notification for subscription related events.
If the NF as an NF consumer provides a Binding Indication for services that the NF produces in service requests, the Binding Indication shall be associated with an applicability indicating other service and may contain the related service name(s), in addition to the other parameters listed in Table 6.3.1.0-1. If no service name(s) are provided, the Binding Indication relates to all services that the NF produces.
For NF Set or NF Instance level of binding, a Binding Indication for notifications and other services may be combined if it relates to the same service and that combined Binding Indication shall then be associated with an applicability indicating all scenarios that the Binding Indication relates to (For this purpose, the applicability can indicate a combination of values).
If no applicability is indicated in a request or subscribe messages, a Binding Indication in that messages is applicable for notification to all events except for the subscription related event (see clause 4.17.12.4 of TS 23.502 [3]).
NOTE 3: Such a request message can be used for implicit subscription.
NOTE 4: Request messages can contain both the Binding Indications for services and for notifications and in addition, the Routing Binding Indication in the case of indirect communication.
A Binding Indication may be shared by a group of resources (e.g. contexts) identified by a group identifier. This enables a NF Service consumer or producer to update the binding indication for this group of resources in a single request or notification towards a given peer NF service instance, e.g. when a group of resources need to be taken over by a different NF within an NF set. See clause 6.12.1 of TS 29.500 [49].
Table 6.3.1.0-1 defines the selection and reselection behaviour of NF services consumers and SCPs depending on the Binding Indication provided by an NF service producer. The detailed procedures refer to clause 4.17.11 and 4.17.12 of TS 23.502 [3].
Table 6.3.1.0-1: Binding, selection and reselection
Level of Binding Indication
The NF Consumer / Notification sender / SCP selects
The NF Consumer / Notification sender / SCP can reselect e.g. when selected producer is not available
Binding information for selection and re-selection
NF Service Instance
The indicated NF Service Instance
An equivalent NF Service instance:
- within the NF Service Set (if applicable)
- within the NF instance
- within the NF Set (if applicable)
NF Service Instance ID, NF Service Set ID, NF Instance ID, NF Set ID, Service name (NOTE 4)
NF Service Set
Any NF Service instance within the indicated NF Service Set
Any NF Service instance within an equivalent NF Service Set within the NF Set (if applicable)
(Note 2)
NF Service Set ID, NF Instance ID, NF Set ID, Service name (NOTE 4)
NF Instance
Any equivalent NF Service instance within the NF instance.
Any equivalent NF Service instance within a different NF instance within the NF Set (if applicable)
NF Instance ID, NF Set ID, Service name (NOTE 4)
NF Set
Any equivalent NF Service instance within the indicated NF Set
Any equivalent NF Service instance within the NF Set
NF Set ID, Service name (NOTE 4)
NOTE 1: if the Binding Indication is not available, the NF Consumer routes the service request to the target based on routing information available.
NOTE 2: NF Service Sets in different NFs are considered equivalent if they include same type and variant (e.g. identical NF Service Set ID) of NF Services.
NOTE 3: If a Routing Binding Indication is not available, the SCP routes the service request to the target based on available routing information.
NOTE 4: The service name is only applicable if the Binding Indication relates to a notification target or If the NF as a NF consumer provides a Binding Indication for services that the NF produces. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.3.1.1 NF Discovery and Selection aspects relevant with indirect communication | For indirect communication shown in Annex E, the SCP performs the following functionalities regarding Network Function and Network Function Service discovery and selection:
- If the request includes a Routing Binding Indication, the SCP shall route the service request to the requested target as specified in Table 6.3.1.0-1. If the Routing Binding Indication does not exist, the SCP may get the NF Set ID from the NRF or local configuration (if available).
- If the request recipient had previously provided a Binding Indication, then the request sender shall include a Routing Binding Indication with the same contents in subsequent related requests. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.3.1.2 Location information | The location information describes the network location of the NF instance. It can consist of one or more levels. Each level describes one location aspect, such as geographic location, data centre, cluster, etc. An NF instance has only one location.
The location information may be used to select the NF service instance or NF instance from a particular network location based on local configuration.
NOTE: The location information in TS 29.510 [58] specifies the granularity of location information. It is up to each deployment to determine the granularity of location information to be used. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.3.2 SMF discovery and selection | The SMF selection functionality is supported by the AMF and SCP and is used to allocate an SMF that shall manage the PDU Session. The SMF selection procedures are described in clause 4.3.2.2.3 of TS 23.502 [3].
The SMF discovery and selection functionality follows the principles stated in clause 6.3.1.
If the AMF does discovery, the AMF shall utilize the NRF to discover SMF instance(s) unless SMF information is available by other means, e.g. locally configured on AMF. The AMF provides UE location information to the NRF when trying to discover SMF instance(s). The NRF provides NF profile(s) of SMF instance(s) to the AMF. In addition, the NRF also provides the SMF service area of SMF instance(s) to the AMF. The SMF selection functionality in the AMF selects an SMF instance and an SMF service instance based on the available SMF instances obtained from NRF or on the configured SMF information in the AMF.
NOTE 1: Protocol aspects of the access to NRF are specified in TS 29.510 [58].
The SMF selection functionality is applicable to both 3GPP access and non-3GPP access.
The SMF selection for Emergency services is described in clause 5.16.4.5.
The following factors may be considered during the SMF selection:
a) Selected Data Network Name (DNN). The formulation of the DNN considers the information provided in f) below. In the case of the home routed roaming, the DNN is not applied for the V-SMF selection.
b) S-NSSAI of the HPLMN (for non-roaming and home-routed roaming scenarios) and S-NSSAI of the VPLMN (for roaming with local breakout and home-routed roaming scenarios).
c) NSI-ID.
NOTE 2: The use of NSI -ID in the network is optional and depends on the deployment choices of the operator. If used, the NSI ID is associated with S-NSSAI.
d) Access technology being used by the UE.
e) Support for Control Plane CIoT 5GS Optimisation.
f) Subscription information from UDM, e.g.
- per DNN: whether LBO roaming is allowed.
- per DNN: whether HR-SBO roaming is allowed.
- per S-NSSAI: the subscribed DNN(s).
- per (S-NSSAI, subscribed DNN): whether LBO roaming is allowed.
- per (S-NSSAI, subscribed DNN): whether HR-SBO roaming is allowed.
- per (S-NSSAI, subscribed DNN): whether EPC interworking is supported.
- per (S-NSSAI, subscribed DNN): whether selecting the same SMF for all PDU sessions to the same S-NSSAI and DNN is required.
- per (S-NSSAI, DNN) associated with 5G VN group: Service Area (LADN service area) for the 5G VN group. In the case of SMF selection for a PDU Session targeting 5G VN group, the AMF may prefer candidate SMF(s) that have an intersection with the LADN service area of the 5G VN group.
- per (S-NSSAI, subscribed DNN): Additional Parameters for SMF selection in target PLMN as defined in TS 23.502 [3] and may include the target network identifier (i.e. PLMN ID preferred by the operator).
NOTE 3: When AMF formulates the NRF query for SMF selection, the target network identifier (i.e. PLMN ID) in subscription data can be used as the Operator Identifier of the DNN parameter and as part of the Target PLMN List parameter.
g) Void.
h) Local operator policies.
NOTE 3: These policies can take into account whether the SMF to be selected is an I-SMF or a V-SMF or a SMF.
i) Load conditions of the candidate SMFs.
j) Analytics (i.e. statistics or predictions) for candidate SMFs' load as received from NWDAF (see TS 23.288 [86]), if NWDAF is deployed.
k) UE location (i.e. TA).
l) Service Area of the candidate SMFs or serving scope/preferred locality (which may be formulated by AMF, as specified in TS 29.510 [58], based on UE location) of the candidate SMFs.
m) Capability of the SMF to support a MA PDU Session.
n) If interworking with EPS is required.
o) Preference of V-SMF support. This is applicable only for V-SMF selection in the case of home routed roaming.
p) Target DNAI.
q) Capability of the SMF to support User Plane Remote Provisioning (see clause 5.30.2.10.4.3).
r) Supported DNAI list.
s) HR-SBO support (according to clause 6.7 of TS 23.548 [130]).
t) Capability of the SMF (V-SMF and H-SMF) to support non-3GPP access path switching.
u) Capability of the SMF (I-SMF) to support Local Offloading management (according to clause 6.10 of TS 23.548 [130]).
v) Supported Local Offloading Management service area (see clause 6.10 of TS 23.548 [130]).
To support the allocation of a static IPv4 address and/or a static IPv6 prefix as specified in clause 5.8.2.2.1, a dedicated SMF may be deployed for the indicated combination of DNN and S-NSSAI and registered to the NRF, or provided by the UDM as part of the subscription data.
In the case of delegated discovery, the AMF, shall send all the available factors a)-d), k) and n) to the SCP.
In addition, the AMF may indicate to the SCP which NRF to use (in the case of NRF dedicated to the target slice).
If there is an existing PDU Session and the UE requests to establish another PDU Session to the same DNN and S-NSSAI of the HPLMN and the UE subscription data indicates the support for interworking with EPS for this DNN and S-NSSAI of the HPLMN or UE subscription data indicates the same SMF shall be selected for all PDU sessions to the same S-NSSAI, DNN, the same SMF in non roaming and LBO case or the same H-SMF in home routed roaming case, shall be selected. In addition, if the UE Context in the AMF provides a SMF ID for an existing PDU session to the same DNN, S-NSSAI, the AMF uses the stored SMF ID for the additional PDU Session. In any such a case where the AMF can determine which SMF should be selected, if delegated discovery is used, the AMF shall indicate a desired NF Instance ID so that the SCP is able to route the message to the relevant SMF. Otherwise, if UE subscription data does not indicate the support for interworking with EPS for this DNN and S-NSSAI, a different SMF in non roaming and LBO case or a different H-SMF in home routed roaming case, may be selected. For example, to support a SMF load balancing or to support a graceful SMF shutdown (e.g. a SMF starts to no more take new PDU Sessions).
In the home-routed roaming case, the SMF selection functionality selects an SMF in VPLMN based on the S-NSSAI of the VPLMN, as well as an SMF in HPLMN based on the S-NSSAI of the HPLMN. This is specified in clause 4.3.2.2.3.3 of TS 23.502 [3].
In the case of Indirect Network Sharing, the SMF selection of the anchor SMF in the participating operator's network reuses the procedure of H-SMF selection for home-routed roaming but may furthermore take into account the location information based on current UE location.
If the HR-SBO roaming is allowed for the PDU Session, the DNN is also considered for V-SMF selection.
If Local Offloading Management is allowed for the non-roaming PDU Session, the capability of supporting Local Offloading Management is considered for SMF and I-SMF selection and the Supported Local Offloading Management service area is further considered for I-SMF selection.
When the UE requests to establish a PDU Session to a DNN and an S-NSSAI of the HPLMN, if the UE MM Core Network Capability indicates the UE supports EPC NAS and optionally, if the UE subscription indicates the support for interworking with EPS for this DNN and S-NSSAI of the HPLMN, the selection functionality (in AMF or SCP) selects a combined SMF+PGW-C. Otherwise, a standalone SMF may be selected.
If the UDM provides a subscription context that allows for handling the PDU Session in the VPLMN (i.e. using LBO) for this DNN and S-NSSAI of the HPLMN and, optionally, the AMF is configured to know that the VPLMN has a suitable roaming agreement with the HPLMN of the UE, the following applies:
- If the AMF does discovery, the SMF selection functionality in AMF selects an SMF from the VPLMN.
- If delegated discovery is used, the SCP selects an SMF from the VPLMN.
If an SMF in the VPLMN cannot be derived for the DNN and S-NSSAI of the VPLMN, or if the subscription does not allow for handling the PDU Session in the VPLMN using LBO, then the following applies:
- If the AMF does discovery, both an SMF in VPLMN and an SMF in HPLMN are selected and the DNN and S-NSSAI of the HPLMN is used to derive an SMF identifier from the HPLMN.
- If delegated discovery is used:
- The AMF performs discovery and selection of H-SMF from NRF. The AMF may indicate the maximum number of H-SMF instances to be returned from NRF, i.e. SMF selection at NRF.
- The AMF sends Nsmf_PDUSession_CreateSMContext Request to SCP, which includes the endpoint (e.g. URI) of the selected H-SMF and the discovery and selection parameters as defined in this clause, i.e. parameter for V-SMF selection. The SCP performs discovery and selection of the V-SMF and forwards the request to the selected V-SMF.
- The V-SMF sends the Nsmf_PDUSession_Create Request towards the H-SMF via the SCP; the V-SMF uses the received endpoint (e.g. URI) of the selected H-SMF to construct the target destination to be addressed. The SCP forwards the request to the H-SMF.
- Upon reception of a response from V-SMF, based on the received V-SMF ID the AMF obtains the Service Area of the V-SMF from NRF. The AMF uses the Service Area of the V-SMF to determine the need for V-SMF relocation upon subsequent UE mobility.
If the initially selected SMF in VPLMN (for roaming with LBO) detects it does not understand information in the UE request, it may reject the N11 message (related with a PDU Session Establishment Request message) with a proper N11 cause triggering the AMF to select both a new SMF in the VPLMN and a SMF in the HPLMN (for home routed roaming).
The AMF selects SMF(s) considering support for CIoT 5GS optimisations (e.g. Control Plane CIoT 5GS Optimisation).
In the case of onboarding of UEs for SNPNs, when the UE is registered for SNPN onboarding the AMF selects SMF(s) of Onboarding Network considering the Capability of SMF to support User Plane Remote Provisioning.
Additional details of AMF selection of an I-SMF are described in clause 5.34 and in clause 6.10 of TS 23.548 [130] for Local Offloading Management.
In the case of home routed scenario, the AMF selects a new V-SMF if it determines that the current V-SMF cannot serve the UE location. The selection/relocation is same as an I-SMF selection/relocation as described in clause 5.34.
In the case of SMF event exposure service for any UE and in deployments with I-SMF, the DNAI and/or AoI are not used in the SMF discovery request by the UPF event consumer. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.3.3 User Plane Function Selection | |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.3.3.1 Overview | The selection and reselection of the UPF for PDU session establishment, UE mobility or UE traffic offloading are performed by the SMF by considering UPF deployment scenarios such as centrally located UPF and distributed UPF located close to or at the Access Network site. The selection of the UPF shall also enable deployment of UPF with different capabilities, e.g. UPFs supporting no or a subset of optional functionalities.
The SMF may be made aware of UPF capabilities (e.g. operator configurable UPF capabilities, NAT information exposure functionality, IP or MAC filter-based packet detection functionality) during N4 association setup procedure or N4 association update procedure as described in clause 4.4.3 of TS 23.502 [3], or the SMF may utilize the NRF to discover UPF(s) that supports those capabilities as described in clause 4.17 of TS 23.502 [3].
When the UPF selection for PDU session establishment takes place in home routed roaming case, the UPF(s) in home PLMN is selected by SMF(s) in HPLMN and the UPF(s) in the VPLMN is selected by SMF(s) in VPLMN. The exact set of parameters used for the selection mechanism is deployment specific and controlled by the operator configuration.
The UPF selection for PDU session establishment, UE mobility or UE traffic offloading involves:
- A step of SMF Provisioning of available UPF(s) (details are described in clause 6.3.3.2). This step may take place while there is no PDU Session to establish and is followed by N4 Node Level procedures defined in clause 4.4.3 of TS 23.502 [3] where the UPF and the SMF may exchange information such as the support of optional functionalities and capabilities.
- A step of selection of an UPF for a particular PDU Session (details are described in clause 6.3.3.3) which is followed by N4 session management procedures defined in clause 4.4.1 of TS 23.502 [3].
The selection and reselection of the UPF is also performed by an NF (other than the SMF) in order to collect the data from the UPF as defined in clause 5.8.2.17. In this case, the related dedicated UPF is discovered and selected as follows:
- When the NF consumer or SCP directly subscribes to the UPF (if allowed by the conditions defined in clause 5.8.2.17), the NF consumer or SCP queries the NRF including the related discovery parameters. The NRF returns the UPF(s) which meet(s) the discovery request.
- When the NF consumer or SCP shall subscribe via the SMF, the NF consumer gets the serving SMF information from the UDM per SUPI, DNN and S-NSSAI. After that, the NF consumer sends a subscription to the indicated SMF and the SMF identifies the related UPF(s) using the parameters of the subscription (e.g. target flow description, AoI, etc.) and transfers the related event subscription information to the identified UPF(s). If the NF consumer does not know the SUPI but only the UE IP address, it may need to invoke the BSF to get the SUPI corresponding to the triplet (UE IP address, DNN and S-NSSAI). |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.3.3.2 SMF Provisioning of available UPF(s) | SMF may be locally configured with the information about the available UPFs, e.g. by OAM system when a UPF is instantiated or removed, or the SMF may become aware of a UPF via a UPF initiated N4 Association establishment (as described in clause 4.4.3 of TS 23.502 [3]).
NOTE 1: UPF information can be updated e.g. by OAM system any time after the initial provisioning, or UPF itself updates its information to the SMF via N4 node level procedures anytime after N4 Association establishment.
The UPF selection functionality in the SMF may optionally utilize the NRF to discover UPF(s). In this case, the SMF issues a request to the NRF that may include following parameters: DNN, S-NSSAI, SMF Area Identity, the requested functionalities and capabilities (e.g. ATSSS steering capabilities, functionality associated with high data rate low latency service, NAT information exposure functionality, IP or MAC filter-based packet detection functionality, operator configurable UPF capabilities, etc.). In its answer, the NRF provides the NF profile(s) that include(s) the IP address(es) or the FQDN of the N4 interface of corresponding UPF(s) to the SMF. If required and/or preferred UPF functionalities are received from UDM (see clause 5.2.3.3.1 of TS 23.502 [3]), the SMF considers this information for discovering UPF(s).
UPFs may be associated with an SMF Area Identity in the NRF. This allows limiting the SMF provisioning of UPF(s) using NRF to those UPF(s) associated with a certain SMF Area Identity. This can e.g. be used in the case that an SMF is only allowed to control UPF(s) configured in NRF as belonging to a certain SMF Area Identity.
The NRF may be configured by OAM with information on the available UPF(s) or the UPF(s) may register its/their NF profile(s) in the NRF. This is further defined in clause 4.17 of TS 23.502 [3]. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.3.3.3 Selection of an UPF for a particular PDU Session | The following parameter(s) and information may be considered by the SMF for UPF selection and re-selection:
- UPF's dynamic load.
- Analytics (i.e. statistics or predictions) for UPF load, Service Experience analytics and/or DN Performance analytics per UP path (including UPF and/or DNAI and/or AS instance) and UE related analytics (UE mobility, UE communication and expected UE behavioural parameters) as received from NWDAF (see TS 23.288 [86]), if NWDAF is deployed.
- UPF's relative static capacity among UPFs supporting the same DNN.
- UPF location available at the SMF.
- UE location information.
- Capability of the UPF and the functionality required for the particular UE session: An appropriate UPF can be selected by matching the functionality and features required for an UE.
- Data Network Name (DNN).
- PDU Session Type (i.e. IPv4, IPv6, IPv4v6, Ethernet Type or Unstructured Type) and if applicable, the static IP address/prefix.
- SSC mode selected for the PDU Session.
- UE subscription profile in UDM.
- DNAI as included in the PCC Rules and described in clause 5.6.7.
- Local operator policies.
- S-NSSAI.
- Access technology being used by the UE.
- Information related to user plane topology and user plane terminations, that may be deduced from:
- 5G-AN-provided identities (e.g. CellID, TAI), available UPF(s) and DNAI(s);
- Identifiers (i.e. a FQDN and/or IP address(es)) of N3 terminations provided by a W-AGF or a TNGF or a TWIF;
NOTE 1: A W-AGF or a TNGF may provide Identifiers of its N3 terminations when forwarding over N2 uplink NAS signalling to the 5GC. The AMF may relay this information to the SMF, as part of session management signalling for a new PDU Session.
- Information regarding the user plane interfaces of UPF(s). This information may be acquired by the SMF using N4;
- Information regarding the N3 User Plane termination(s) of the AN serving the UE. This may be deduced from 5G-AN-provided identities (e.g. CellID, TAI);
- Information regarding the N9 User Plane termination(s) of UPF(s) if needed;
- Information regarding the User plane termination(s) corresponding to DNAI(s).
- RSN, support for redundant GTP-U path or support for redundant transport path in the transport layer (as in clause 5.33.2) when redundant UP handling is applicable.
- Information regarding the ATSSS Steering Capability of the UE session (e.g. any combination of ATSSS-LL capability, MPTCP capability, MPQUIC-UDP capability, MPQUIC-IP capability and MPQUIC-E capability) and information on the UPF support of RTT measurements without PMF.
- Support for UPF allocation of IP address/prefix.
- Support of the IPUPS functionality, specified in clause 5.8.2.14.
- Support for High latency communication (see clause 5.31.8).
- Support for functionality associated with high data rate low latency services, eXtended Reality (XR) and interactive media services, specified in clause 5.37 (for example, ECN marking for L4S, specified in clause 5.37.3, PDU Set Marking, specified in clause 5.37.5, UE power saving management, specified in clause 5.37.8, Data Burst Size Marking, specified in clause 5.37.10.1, Time To Next Data Burst Marking, specified in clause 5.37.10.2, PDU Set Importance based transport level packet marking, specified in clause 5.8.2.7).
- Support for the On-path N6 signalling methods, e.g. MoQ relay functionality and/or CONNECT-UDP HTTP client functionality and/or UDP option functionality (as described in clause 5.37.9)
- User Plane Latency Requirements within AF request (see clause 5.6.7.1 and clause 6.3.6 of TS 23.548 [130]).
- List of supported Event ID(s) for exposure of UPF-related information via service based interface (see clause 7.2.29 and clause 5.2.26.2 of TS 23.502 [3]).
- Information regarding required and/or preferred UPF functionalities (see clause 5.2.3.3.1 of TS 23.502 [3]). If received from UDM, the SMF selects a PSA UPF supporting the required UPF functionalities and the best set of preferred functionalities based on their priorities if received.
- Support of NAT information exposure functionality.
- Support of IP or MAC filter-based packet detection functionality.
- Supported operator configurable UPF capabilities as described in clause 5.8.2.21.
- N6 delay between the candidate UPF(s) and measurement endpoint in the DN as specified in clause 5.8.2.23.
- Delay between the 5G AN and candidate UPF(s) as part of user plane latency (see clause 5.33.3.1).
NOTE 2: Latencies between 5GC AN and UPF(s) can be configured. If QoS monitoring has previously been performed, the delays of such measurements can also be used.
NOTE 3: How the SMF determines information about the user plane network topology from information listed above and what information is considered by the SMF, is based on operator configuration.
NOTE 4: In this release the SMF uses no additional parameters for UPF selection for a PDU Session serving TSC or Deterministic Networking. If a PDU Session needs to connect to a specific UPF hosting a specific TSN 5GS bridge or 5GS router, this can be achieved e.g. by using a dedicated DNN/S-NSSAI combination.
If there is an existing PDU Session and the SMF receives another PDU Session request to the same DNN and S-NSSAI and if the SMF determines that interworking with EPC is supported for this PDU Session (as specified in clause 4.11.5 of TS 23.502 [3]), the SMF should select the same UPF if it supports all capabilities required for the new PDU Session. Otherwise, if the SMF determines that interworking with EPC is not supported for the new PDU Session or the UPF of the existing PDU Session does not support all capabilities required for the new PDU Session, a different UPF may be selected according to operator policy.
For the same DNN and S-NSSAI if different UPFs are selected at 5GC, when the UE is moved to EPC network, there is no requirement to enforce APN-AMBR. Whether and how to apply APN-AMBR for the PDN Connection associated with this DNN/APN is implementation dependent, e.g. possibly only AMBR enforcement per PDU Session applies. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.3.4 AUSF discovery and selection | In the case of NF consumer based discovery and selection, the following applies:
- The AMF and the NSWOF perform AUSF selection to allocate an AUSF Instance that performs authentication between the UE and 5G CN in the HPLMN. The AMF and the NSWOF shall utilize the NRF to discover the AUSF instance(s) unless AUSF information is available by other means, e.g. locally configured on AMF and on NSWOF. The AUSF selection function in the AMF and in the NSWOF selects an AUSF instance based on the available AUSF instances (obtained from the NRF or locally configured in the AMF).
- The UDM shall utilize the NRF to discover the AUSF instance(s) unless AUSF information is available by other means, e.g. locally configured on UDM. The UDM selects an AUSF instance based on the available AUSF instance(s) obtained from the NRF or based on locally configured information and information stored (by the UDM) from a previously successful authentication.
AUSF selection is applicable to both 3GPP access and non-3GPP access.
The AUSF selection function in AUSF NF consumers or in SCP should consider one of the following factors when available:
1. Home Network Identifier (e.g. MNC and MCC, realm) of SUCI/SUPI (by an NF consumer in the Serving network) along with the selected NID (provided by the NG-RAN) in the case of SNPN, Routing Indicator and optionally Home Network Public Key identifier (e.g. in the case that Routing Indicator is not enough to provide SUPI range granularity).
NOTE 1: The UE provides the SUCI, which contains the Routing Indicator and Home Network Public Key identifier as defined in TS 23.003 [19], to the AMF during initial registration and to the NSWOF during NSWO authentication. The AMF can provide the UE's Routing Indicator and optionally Home Network Public Key identifier to other AMFs as described in TS 23.502 [3].
NOTE 2: The usage of Home Network Public Key identifier for AUSF discovery is limited to the scenario where the AUSF NF consumers belong to the same PLMN as AUSF.
NOTE 3: In the case of SNPN and if the UE provides an IMSI type SUCI to the AMF and the SUCI provided by UE or the SUPI derived from the SUCI is for an SNPN served by the AMF, the AMF uses the selected NID provided by the NG-RAN together with the selected PLMN ID (from IMSI) or the Routing Indicator provided by the UE within the SUCI for selection of AUSF. In the case of SNPN and the UE provides an NSI type SUCI to the AMF, the AMF uses the Home Network Identifier and Routing Indicator of SUCI/SUPI for selection of AUSF.
When the UE's Routing Indicator is set to its default value as defined in TS 23.003 [19], the AUSF NF consumer can select any AUSF instance within the home network for the UE.
2. AUSF Group ID the UE's SUPI belongs to.
NOTE 4: The AMF can infer the AUSF Group ID the UE's SUPI belongs to, based on the results of AUSF discovery procedures with NRF. The AMF provides the AUSF Group ID the SUPI belongs to other AMFs as described in TS 23.502 [3].
3. SUPI; e.g. the AMF selects an AUSF instance based on the SUPI range the UE's SUPI belongs to or based on the results of a discovery procedure with NRF using the UE's SUPI as input for AUSF discovery.
NOTE 5: In the case of Onboarding via ON-SNPN, AUSF instances supporting UE onboarding can be registered in NRF or locally configured in the AMF. The AMF in ON-SNPN can discover and select AUSF instance(s) supporting UE onboarding based on the MCC and MNC or realm part in Home Network Identifier of the SUCI/SUPI provided by the onboarding UE.
In the case of delegated discovery and selection in SCP, the AUSF NF consumer shall send all available factors to the SCP. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.3.5 AMF discovery and selection | The AMF discovery and selection functionality is applicable to both 3GPP access and non-3GPP access.
The AMF selection functionality can be supported by the 5G-AN (e.g. RAN, N3IWF) and is used to select an AMF instance for a given UE. An AMF supports the AMF selection functionality to select an AMF for relocation or because the initially selected AMF was not an appropriate AMF to serve the UE (e.g. due to change of Allowed NSSAI). Other CP NF(s), e.g. SMF, supports the AMF selection functionality to select an AMF from the AMF set when the original AMF serving a UE is unavailable.
The TSCTSF shall use the AMF discovery functionality to determine the AMFs serving the TAs in the spatial validity condition provided by the AF.
5G-AN selects an AMF Set and an AMF from the AMF Set under the following circumstances:
1) When the UE provides no 5G-S-TMSI nor the GUAMI to the 5G-AN.
2) When the UE provides 5G-S-TMSI or GUAMI but the routing information (i.e. AMF identified based on AMF Set ID, AMF pointer) present in the 5G-S-TMSI or GUAMI is not sufficient and/or not usable (e.g. UE provides GUAMI with an AMF region ID from a different region).
NOTE 1: When the UE accesses NG-RAN onboard satellite (i.e. regenerative based satellite access), the NG-RAN can be configured to select an AMF set supporting NG Removal procedure defined in TS 38.413 [34].
3) AMF has instructed AN that the AMF (identified by GUAMI(s)) is unavailable and no target AMF is identified and/or AN has detected that the AMF has failed.
4) When the UE attempts to establish a signalling connection and the following conditions are met:
- the 5G-AN knows in what country the UE is located; and
- the 5G-AN is connected to AMFs serving different PLMNs of different countries; and
- the UE provides a 5G-S-TMSI or GUAMI, which indicates an AMF serving a different country to where the UE is currently located; and
- the 5G-AN is configured to enforce selection of the AMF based on the country the UE is currently located.
Then the 5G-AN shall select an AMF serving a PLMN corresponding to the UE's current location. How 5G-AN selects the AMF in this case is defined in TS 38.410 [125].
NOTE 2: AMF selection case 4) does not apply if 5G-AN nodes serves one country only.
In the case of NF Service Consumer based discovery and selection, the CP NF selects an AMF from the AMF Set under the following circumstances:
- When the AMF has instructed CP NF that a certain AMF identified by GUAMI(s) is unavailable and the CP NF was not notified of target AMF; and/or
- CP NF has detected that the AMF has failed; and/or
- When the selected AMF does not support the UE's Preferred Network Behaviour; and/or
- When the selected AMF does not support the High Latency communication for NR RedCap UE.
In the case of delegated discovery and associated selection, the SCP selects an AMF from the corresponding AMF Set under the following circumstances:
- The SCP gets an indication "select new AMF within SET" from the CP NF; and/or
- SCP has detected that the AMF has failed.
The AMF selection functionality in the 5G-AN may consider the following factors for selecting the AMF Set:
- AMF Region ID and AMF Set ID derived from GUAMI;
- Requested NSSAI;
- Local operator policies;
- 5G CIoT features indicated in RRC signalling by the UE;
- IAB-indication;
- NB-IoT RAT Type;
- Category M Indication;
- NR RedCap Indication;
- SNPN Onboarding indication as indicated in 5G-AN signalling by the UE;
- Mobile IAB-indication.
AMF selection functionality in the 5G-AN or CP NFs or SCP considers the following factors for selecting an AMF from AMF Set:
- Availability of candidate AMF(s).
- Load balancing across candidate AMF(s) (e.g. considering weight factors of candidate AMFs in the AMF Set).
- In 5G-AN, 5G CIoT features indicated in RRC signalling by the UE.
- In 5G-AN, SNPN Onboarding indication as indicated in 5G-AN signalling by the UE.
When the UE accesses the 5G-AN with a 5G-S-TMSI or GUAMI that identifies more than one AMF (as configured during N2 setup procedure), the 5G-AN selects the AMF considering the weight factors.
When 5G-S-TMSI or GUAMI provided by the UE to the 5G-AN contains an AMF Set ID that is usable and the AMF identified by AMF pointer that is not usable (e.g. AN detects that the AMF has failed) or the corresponding AMF indicates it is unavailable (e.g. out of operation) then the 5G-AN uses the AMF Set ID for selecting another AMF from the AMF set considering the factors above.
The discovery and selection of AMF in the CP NFs or SCP follows the principle in clause 6.3.1
In the case of NF Service Consumer based discovery and selection, the AMF or other CP NFs shall utilize the NRF to discover the AMF instance(s) unless AMF information is available by other means, e.g. locally configured on AMF or other CP NFs. The NRF provides the NF profile(s) of AMF instance(s) to the AMF or other CP NFs. The AMF selection function in the AMF or other CP NFs selects an AMF instance as described below:
When NF Service Consumer performs discovery and selection the following applies:
- In the case of AMF discovery and selection functionality in AMF or other CP NFs use GUAMI (in the SNPN case, along with NID of the SNPN that owns the AMF instances to be discovered and selected) or TAI to discover the AMF instance(s), the NRF provides the NF profile of the associated AMF instance(s). If an associated AMF is unavailable due to AMF planned removal, the NF profile of the backup AMF used for planned removal is provided by the NRF. If an associated AMF is unavailable due to AMF failure, the NF profile of the backup AMF used for failure is provided by the NRF. If AMF pointer value in the GUAMI is associated with more than one AMF, the NRF provides all the AMFs associated with this AMF pointer value. If no AMF instances related to the indicated GUAMI can be found, the NRF may provide a list of NF profiles of candidate AMF instances in the same AMF Set. The other CP NF or AMF may select any AMF instance from the list of candidate AMF instances. If no NF profiles of AMF is returned in the discovery result, the other CP NF or AMF may discover an AMF using the AMF Set as below.
- In the case of AMF discovery and selection functionality in AMF use AMF Set to discover AMF instance(s), the NRF provides a list of NF profiles of AMF instances in the same AMF Set.
- At intra-PLMN mobility, the AMF discovery and selection functionality in AMF may use AMF Set ID, AMF Region ID, the target location information, S-NSSAI(s) of Allowed NSSAI to discover target AMF instance(s). The NRF provides the target NF profiles matching the discovery.
- At intra-SNPN mobility, the AMF discovery and selection functionality in AMF may use AMF Set ID, AMF Region ID (along with NID of the SNPN that owns the AMF instances to be discovered and selected), the target location information, S-NSSAI(s) of Allowed NSSAI, AMF support of SNPN Onboarding (if the UE is registered for SNPN Onboarding) to discover target AMF instance(s). The NRF provides the target NF profiles matching the discovery.
- At inter PLMN mobility, the source AMF selects an AMF instance(s) in the target PLMN by querying target PLMN level NRF via the source PLMN level NRF with target PLMN ID. The target PLMN level NRF returns an AMF instance address based on the target operator configuration. After the Handover procedure the AMF may select a different AMF instance as specified in clause 4.2.2.2.3 of TS 23.502 [3].
In the context of Network Slicing, the AMF selection is described in clause 5.15.5.2.1.
When delegated discovery and associated selection is used, the following applies:
- If the CP NF includes GUAMI or TAI in the request, the SCP selects an AMF instance associated with the GUAMI or TAI and sends the request to a selected AMF service instance if it is available. The following also applies:
- If none of the associated AMF service instances are available due to AMF planned removal, an AMF service instance from the backup AMF used for planned removal is selected by the SCP;
- If none of the associated AMF service instances are available due to AMF failure, an AMF service instance from the backup AMF used for failure is selected by the SCP;
- If no AMF service instances related to the indicated GUAMI (in the SNPN case, along with NID of the SNPN that owns the AMF instances to be discovered and selected) can be found the SCP selects an AMF instance from the AMF Set; or
- AMF Pointer value used by more than one AMF, SCP selects one of the AMF instances associated with the AMF Pointer.
- If the CP NF includes AMF Set ID in the request, the SCP selects AMF/AMF service instances in the provided AMF Set.
- At intra-PLMN mobility, if a target AMF instance needs to be selected, the AMF may provide AMF Set ID, AMF Region ID and the target location information, S-NSSAI(s) of Allowed NSSAI in the request, optionally NRF to use. The SCP will select a target AMF instance matching the discovery.
- At intra-SNPN mobility, if a target AMF instance needs to be selected, the AMF may provide AMF Set ID, AMF Region ID along with NID of the SNPN that owns the AMF instances to be discovered and selected and the target location information, S-NSSAI(s) of Allowed NSSAI, AMF support of SNPN Onboarding in the request (if the UE is registered for SNPN Onboarding), optionally NRF to use. The SCP will select a target AMF instance matching the discovery.
- At inter PLMN mobility, the source AMF selects indicates "roaming" to the SCP. The SCP interacts with the NRF in source PLMN so that the NRF in source PLMN can discover an AMF in the target PLMN via target PLMN NRF. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.3.6 N3IWF selection | |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.3.6.1 General | When the UE supports connectivity with N3IWF but does not support connectivity with ePDG, as specified in TS 23.402 [43], the UE shall perform the procedure in clause 6.3.6.2 for selecting an N3IWF.
When the UE supports connectivity with N3IWF, as well as with ePDG, as specified in TS 23.402 [43], the UE shall perform the procedure in clause 6.3.6.3 for selecting either an N3IWF or an ePDG, i.e. for selecting a non-3GPP access node.
In both cases above the UE can be configured by the HPLMN with the same information that includes:
1) ePDG identifier configuration: It contains the FQDN or IP address of the ePDG in the HPLMN, as specified in clause 4.5.4.3 of TS 23.402 [43]. This is used only when the UE supports connectivity with ePDG and attempts to select an ePDG. It is ignored in all other cases.
2) N3IWF identifier configuration: It contains the FQDN or IP address of the N3IWF in the HPLMN.
3) Extended Home N3IWF identifier configuration: It contains one or multiple tuples of FQDN/IP address of the N3IWF in the HPLMN and the S-NSSAIs supported by this N3IWF.
4) Non-3GPP access node selection information: It contains a prioritized list of PLMNs and for each PLMN it includes (i) a "Preference" parameter which indicates if ePDG or N3IWF is preferred in this PLMN and (ii) an FQDN parameter which indicates if the Tracking/Location Area Identity FQDN or the Operator Identifier FQDN (as specified in clause 4.5.4.4 of TS 23.402 [43]) should be used when discovering the address of an ePDG or N3IWF in this PLMN. The list of PLMNs shall include the HPLMN and shall include an "any PLMN" entry, which matches any PLMN the UE is connected to except the HPLMN.
5) Slice-specific N3IWF prefix configuration: It contains one or multiple tuples consisting of:
- List of supported S-NSSAIs;
- Prefix for the Prefixed N3IWF OI or TA FQDNs.
NOTE 1: Extended Home N3IWF identifier configuration and Slice-specific N3IWF prefix configuration are assumed to be provided to the UE as part of ANDSP.
The ePDG identifier configuration, the N3IWF identifier configuration, the Extended Home N3IWF identifier configuration and the Slice-specific N3IWF Prefix Configuration are optional parameters, while the Non-3GPP access node selection information is required and shall include at least the HPLMN and the "any PLMN" entry.
If the ePDG identifier configuration is configured in the UE, then, when the UE decides to select an ePDG in the HPLMN (according to the procedure in clause 6.3.6.3), the UE shall use the ePDG identifier configuration to find the IP address of the ePDG in the HPLMN and shall ignore the FQDN parameter of the HPLMN in the Non-3GPP access node selection information.
If the N3IWF identifier configuration or the Extended Home N3IWF identifier configuration is configured in the UE, then, when the UE decides to select an N3IWF in the HPLMN (according to the procedure in clause 6.3.6.3 for combined N3IWF/ePDG selection and the procedure in clause 6.3.6.2 for Stand-alone N3IWF selection), the UE shall use the Extended Home N3IWF identifier configuration, if available and otherwise the N3IWF identifier configuration to find the IP address of the N3IWF in the HPLMN and shall ignore the FQDN parameter of the HPLMN in the Non-3GPP access node selection information.
The HPLMN's PCF takes the UE's subscribed S-NSSAIs into account when providing Extended Home N3IWF identifier configuration and/or Slice-specific N3IWF Prefix Configuration to the UE.
If a UE does not support the Extended Home N3IWF identifier configuration and the Slice-specific N3IWF Prefix Configuration, then the HPLMN provides to the UE the Non-3GPP access node selection information and the N3IWF identifier configuration by taking into account the UE's subscribed S-NSSAIs.
NOTE 2: If the HPLMN deploys multiple N3IWFs with different TAs which support different S-NSSAIs, then the HPLMN can configure a UE with N3IWF identifier configuration so that the UE selects an N3IWF that supports the UE's subscribed S-NSSAIs.
The UE can be configured by the VPLMN with the following information applicable for the V-PLMN:
Slice-specific N3IWF prefix configuration: It contains one or multiple tuples consisting of:
- List of supported S-NSSAIs;
- Prefix for the Prefixed N3IWF OI or TA FQDNs.
To enable the V-PCF to provide the UE with Slice-specific N3IWF prefix configuration, the AMF provides the V-PCF with the Configured NSSAI for the serving PLMN during the UE Policy Association Establishment/Modification procedure.
NOTE 3: In non-roaming cases, the UE PCF already receives the subscribed NSSAI from the UDR. Therefore, there is no need for the AMF to provide the Configured NSSAI to the PCF in the non-roaming case.
NOTE 4: PCF (V-PCF in the roaming case) is assumed to be locally configured with information about the slices supported by the different N3IWFs in the serving PLMN.
During the registration procedure the AMF may determine if the N3IWF selected by the UE is suitable for the S-NSSAI(s) requested by the UE considering the UE subscription. If the AMF determines that a different N3IWF should be selected as described in clause 4.12.2.2 of TS 23.502 [3], the AMF:
- may, if the UE supports slice-based N3IWF selection, triggers the UE Policy Association Establishment or UE Policy Association Update procedure to provide the UE with updated N3IWF selection information; when the AMF is informed by the PCF that the update of UE policy information on the UE is completed as described in clause 4.12.2.2.2 of TS 23.502 [3], the AMF releases UE Policy Association if the UE is not registered over 3GPP access before proceeding to the Registration Reject over untrusted non-3GPP access;
- shall send a Registration Reject message to the UE. The AMF may include target N3IWF information (FQDN and/or IP address) in the Registration Reject so that the UE can, if supported by the UE, use the target N3IWF information to select the N3IWF to register to 5GC if the UE wishes to send the same Requested NSSAI as during the previous Registration Request. The target N3IWF information only applies to the one N3IWF selection performed by the UE just after receiving the Registration Reject.
The AMF may determine the N3IWF based on the list of supported TAs and the corresponding list of supported slices for each TA obtained as defined in clause 5.15.8.
NOTE 5: The operator is assumed to ensure that UEs that do not support slice-based N3IWF selection always select an N3IWF that supports at least one slice requested by the UE. This is to avoid unnecessary and potentially repetitive rejections of those UEs. To ensure this, the operator is assumed to provide identifiers of N3IWFs that only support a subset of the slices configured in the network only to UEs that support slice-based N3IWF selection. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.3.6.2 Stand-alone N3IWF selection | The UE performs N3IWF selection based on the ePDG selection procedure as specified in clause 4.5.4 of TS 23.402 [43] except for the following differences:
- The Tracking/Location Area Identifier FQDN shall be constructed by the UE based only on the Tracking Area wherein the UE is located. The N3IWF Tracking/Location Area Identifier FQDN may use the 5GS TAI when the UE is registered to the 5GS, or the EPS TAI when the UE is registered to EPS. The Location Area is not applicable on the 3GPP access.
- The ePDG Operator Identifier (OI) FQDN format is substituted by with N3IWF OI FQDN format as specified in TS 23.003 [19].
- If the UE is configured with Slice-specific N3IWF prefix configuration, then the UE shall construct the Prefixed N3IWF OI FQDN or the Prefixed N3IWF TA FQDN as specified in clauses 28.3.2.2.8 and 28.3.2.2.9 of TS 23.003 [19] instead of the N3IWF OI FQDN and the N3IWF TA FQDN, respectively. To determine the prefix, the UE selects the Slice-specific N3IWF prefix configuration for the selected PLMN that contains S-NSSAIs that match all (or most, in case there is no full match) of the S-NSSAIs that the UE is going to include in the Requested NSSAI in the subsequent Registration procedure.
- The ePDG identifier configuration is substituted by the N3IWF identifier configuration and the Extended Home N3IWF identifier configuration. The Extended Home N3IWF identifier configuration takes precedence over the N3IWF identifier configuration. If the UE is located in the home country and the UE is configured with Extended Home N3IWF identifier configuration, then the UE uses the Extended Home N3IWF identifier configuration to select an N3IWF:
- The UE uses the FQDN or IP address from the Extended Home N3IWF identifier configuration that matches all (or most, if there is no full match) of the S-NSSAIs that the UE is going to request in the subsequent Registration.
- The ePDG selection information is substituted by the Non-3GPP access node selection information and slice-specific N3IWF prefix information. The UE shall give preference to the N3IWF in all PLMNs in the Non-3GPP access node selection information independent of the "Preference" parameter.
- If the UE determines to be located in a country other than its home country (called the visited country), then instead of clause 4.5.4.4, bullet 3 of TS 23.402 [43], the following applies:
a) If the UE is registered via 3GPP access to a PLMN and this PLMN is included in the Non-3GPP access node selection information, then the UE shall select an N3IWF in this PLMN. If the UE fails to connect to an N3IWF in this PLMN, the UE shall select an N3IWF by performing the DNS procedure specified in clause 4.5.4.5 of TS 23.402 [43].
b) In all other cases, (e.g. when the UE is not configured with the Non-3GPP access node selection information, or the UE is registered via 3GPP access to a PLMN but this PLMN is not included in the Non-3GPP access node selection information, or the UE is not registered via 3GPP access to any PLMN), the UE shall select an N3IWF by performing the DNS procedure specified in clause 4.5.4.5 of TS 23.402 [43] with the difference that the UE shall construct the Prefixed N3IWF OI FQDN if the UE is configured with Slice-specific N3IWF prefix configuration for the selected PLMN.
If the UE is accessing PLMN services via SNPN, the UE uses the procedure defined in this clause to select an N3IWF deployed in the PLMN. If the UE is accessing standalone non-public network service via a PLMN (see supported cases in clause 5.30.2.0), the UE uses the procedure defined in clause 6.3.6.2a.
6.3.6.2a SNPN N3IWF selection
This procedure applies when the UE is accessing the SNPN N3IWF in its subscribed SNPN via a PLMN or directly via untrusted non-3GPP access.
The UE shall first determine the country in which it is located. If the UE cannot determine the country in which the UE is located, the UE shall stop N3IWF selection and abort the attempt to access the SNPN via PLMN.
NOTE 1: It is up to UE implementation how to determine the country in which the UE is located.
The UE is configured with one N3IWF address and the MCC of the country where the configured N3IWF is located as defined in TS 24.502 [48].
If the UE determines that it is located in the country where the configured N3IWF is located, then the UE uses the configured N3IWF FQDN to select an N3IWF deployed in the SNPN.
If the UE determines that it is located in a country (called the visited country) different from the country where the configured N3IWF is located, then:
- The UE shall construct an FQDN consisting of the SNPN ID of the subscribed SNPN and the Visited Country FQDN and indicating the query is for SNPN, as specified in TS 23.003 [19] and perform a DNS query for the resulting FQDN.
- If the DNS response contains no records, then the UE determines that the visited country does not mandate the selection of an N3IWF in this country for the SNPN identified by the SNPN ID provided by the UE. In this case the UE uses the configured N3IWF FQDN to select an N3IWF deployed in the SNPN.
- If no DNS response is received, the UE shall stop the N3IWF selection.
NOTE 2: The DNS can be configured to return no records for the visited country regardless of the SNPN ID provided by the UE. This addresses the scenario that the visited country in general does not mandate selection of a local N3IWF.
- If the DNS response contains one or more records, then the UE determines that the visited country mandates the selection of an N3IWF in this country. Each record in the DNS response shall contain the identity of an N3IWF of the UE's subscribed SNPN in the visited country which may be used for N3IWF selection. In this case:
- The UE shall select an N3IWF included in the DNS response based on its own implementation means.
- If the UE cannot select any N3IWF included in the DNS response, then the UE shall stop the N3IWF selection.
NOTE 3: Visited countries which mandate the selection of an N3IWF in the country are assumed to configure the DNS as follows:
(i) For SNPNs that do not have any dedicated N3IWFs in the country and which are not exempt from the requirement to select an N3IWF in the visited country, the DNS response contains a record that cannot be resolved to an IP address;
(ii) for SNPNs that have dedicated N3IWFs in the country, the DNS response contains the identities of the SNPN's N3IWFs in the visited country;
(iii) for SNPNs that are exempt from the requirement to select an N3IWF in the visited country, the DNS response contains no records.
NOTE 4: Self-assigned NIDs are not supported, since a DNS cannot be properly configured for multiple SNPNs using the same self-assigned NID (i.e. in collision scenarios). If the visited country mandates the selection of an N3IWF in the same country, the NAPTR record(s) associated to the Visited Country FQDN of SNPNs that use a self-assigned NID can be provisioned with the replacement field containing an FQDN that cannot be resolved to an IP address.
NOTE 5: The identity of an SNPN's N3IWF in the visited country can be any FQDN, i.e. is not required to include the SNPN ID.
NOTE 6: It is assumed that the AMF, SMF, UPF are located in the same country as the N3IWF and belong to the subscribed SNPN of the UE. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.3.6.3 Combined N3IWF/ePDG Selection | When the UE wants to select a non-3GPP access node (either an N3IWF or an ePDG), the UE shall perform the following procedure:
1) The UE shall attempt to determine the country it is located in. This is determined by implementation-specific methods not defined in this specification. If the UE cannot determine the country it is located in, the UE shall stop the non-3GPP access node selection.
2) If the UE determines to be located in its home country, then:
a) The UE shall select the HPLMN. If the UE fails to connect to an ePDG/N3IWF in the HPLMN, then the UE shall stop the non-3GPP access node selection.
3) If the UE determines to be located in a country other than its home country (called the visited country), then:
a) If the UE is registered via 3GPP access to a PLMN and this PLMN is included in the Non-3GPP access node selection information, then the UE shall select this PLMN. If the UE fails to connect to an ePDG/N3IWF in this PLMN, the UE shall select another PLMN by performing the DNS procedure specified in bullet 3c) below.
b) In all other cases, (e.g. when the UE is not configured with the Non-3GPP access node selection information, or the UE is registered via 3GPP access to a PLMN but this PLMN is not included in the Non-3GPP access node selection information, or the UE is not registered via 3GPP access to any PLMN), the UE shall select a PLMN by performing the DNS procedure specified in bullet 3c) below.
c) The UE shall select a PLMN as follows:
i) The UE shall determine if the non-3GPP access node selection is required for an IMS service or for a non-IMS service. The means of that determination are implementation specific.
ii) If the UE determines that the non-3GPP access node selection is required for a non-IMS service, the UE shall select a PLMN as specified in clause 6.3.6.2. As defined below, if the UE fails to connect to an N3IWF in any PLMN, the UE may attempt to select an ePDG according to the procedure specified in clause 4.5.4.5 of TS 23.402 [43].
iii) If the UE determines that the non-3GPP access node selection is required for an IMS service, the UE shall select a PLMN as follows:
- First, the UE shall perform a DNS query using the Visited Country FQDN for N3IWF, as specified in TS 23.003 [19] to determine if the visited country mandates the selection of N3IWF in this country. The DNS response received by the UE may be empty or may contain the identities of one or more PLMNs in the visited country, which may be used for N3IWF selection, if the UE decides to select an N3IWF, as specified below. For example, the DNS response may contain the identity of PLMN-1 and the identity of PLMN-2.
- Then, the UE shall perform a DNS query using the Visited Country FQDN for ePDG, as specified in TS 23.003 [19] to determine if the visited country mandates the selection of ePDG in this country. The DNS response received by the UE may be empty or may contain the identities of one or more PLMNs in the visited country, which may be used for ePDG selection, if the UE decides to select an ePDG, as specified below. For example, the DNS response may contain the identity of PLMN-1 and the identity of PLMN-3.
- If the UE does not receive a DNS response in none of the above two DNS queries, then the UE shall stop the non-3GPP access node selection. Otherwise, the next steps are executed.
- The UE shall consolidate the PLMN identities received in the above two DNS responses and shall construct a candidate list of PLMNs. For example, the candidate list of PLMNs may contain the identities of PLMN-1, PLMN-2, PLMN-3.
- If the candidate list of PLMNs is empty, then:
- If the Non-3GPP access node selection information contains one or more PLMNs in the visited country, the UE shall select one of these PLMNs based on their priorities in the Non-3GPP access node selection information. If the UE fails to connect to a non-3GPP access node in any of these PLMNs, the UE shall select the HPLMN.
- Otherwise, the UE shall select the HPLMN.
- If the candidate list of PLMNs is not empty, then:
- If the UE is registered via 3GPP access to a PLMN which is included in the candidate list of PLMNs, then the UE shall select this PLMN. If the UE fails to connect to a non-3GPP access node in this PLMN, then the UE shall select a different PLMN included in the candidate list of PLMNs as specified in the next bullet.
- If the UE is registered via 3GPP access to a PLMN which is not included in the candidate list of PLMNs, or the UE is not registered via 3GPP access to any PLMN, or the UE fails to connect to a non-3GPP access node according to the previous bullet, then the UE shall select one of the PLMNs included in the candidate list of PLMNs based on the prioritized list of PLMNs in the Non-3GPP access node selection information (i.e. the UE shall select first the highest priority PLMN in the Non-3GPP access node selection information that is contained in the candidate list of PLMNs). If the Non-3GPP access node selection information does not contain any of the PLMNs in the candidate list of PLMNs, or the UE is not configured with the Non-3GPP access node selection information, or the UE was not able to connect to a non-3GPP access node in any of the PLMNs included in the Non-3GPP access node selection information and in the candidate list of PLMN, then the UE shall select a PLMN included in the candidate list of PLMNs based on its own implementation means.
- If the UE cannot select a non-3GPP access node in any of the PLMNs included in the candidate list of PLMNs, then the UE shall stop the non-3GPP access node selection.
In the selected PLMN the UE shall attempt to select a non-3GPP access node as follows:
1. The UE shall determine if the non-3GPP access node selection is required for an IMS service or for a non-IMS service. The means of that determination are implementation-specific.
2. When the selection is required for an IMS service, the UE shall choose a non-3GPP access node type (i.e. ePDG or N3IWF) based on the "Preference" parameter specified in clause 6.3.6.1, unless the UE has its 5GS capability disabled in which case it shall choose an ePDG independent of the "Preference" parameter setting.
If the "Preference" parameter for the selected PLMN indicates that ePDG is preferred, the UE shall attempt to select an ePDG. If the "Preference" parameter for the selected PLMN indicates that N3IWF is preferred, the UE shall attempt to select an N3IWF.
If the selection fails, including the case when, during the registration performed over either 3GPP or non-3GPP access, the UE receives the IMS Voice over PS session Not Supported over Non-3GPP Access indication (specified in clause 5.16.3.2a), the UE shall attempt selecting the other non-3GPP access node type in the selected PLMN, if any. If that selection fails too, or it is not possible, then the UE shall select another PLMN, according to the procedure specified bullet 3c) above.
3. When the selection is required for a non-IMS service, the UE shall perform the selection by giving preference to the N3IWF independent of the "Preference" parameter setting. If the N3IWF selection fails, or it is not possible, the UE should select another PLMN based on the procedure specified in clause 4.5.4.4 of TS 23.402 [43] and shall attempt to select an N3IWF in this PLMN. If the UE fails to select an N3IWF in any PLMN, the UE may attempt to select an ePDG according to the procedure specified in clause 4.5.4.5 of TS 23.402 [43].
In the above procedure, when the UE attempts to construct a Tracking/Location Area Identifier FQDN either for ePDG selection or for N3IWF selection, the UE shall use the Tracking Area wherein the UE is located and shall construct either:
- an ePDG or N3IWF TAI FQDN based on the 5GS TAI, when the UE is registered to the 5GS; or
- an ePDG or N3IWF TAI FQDN based on the EPS TAI, when the UE is registered to EPS.
NOTE: A UE performing both a selection for an IMS service and a selection for a non-IMS service could get simultaneously attached to a N3IWF and to an ePDG in the same PLMN or in different PLMNs.
If the UE is configured with Slice-specific N3IWF prefix configuration, then the UE shall construct the Prefixed N3IWF OI FQDN or the Prefixed N3IWF TA FQDN as specified in TS 23.003 [19] instead of the N3IWF OI FQDN and the N3IWF TA FQDN, respectively. Further details on constructing the Prefixed N3IWF OI and TA FQDN are described in clause 6.3.6.2. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.3.6.4 PLMN and non-3GPP access node Selection for emergency services | |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.3.6.4.1 General | UE initiates PLMN and non-3GPP access node selection for emergency services when it detects a user request for emergency session and determines that untrusted non-3GPP access shall be used for the emergency access.
When the UE supports connectivity with N3IWF but does not support connectivity with ePDG, as specified in TS 23.402 [43], the UE shall perform the procedure in clause 6.3.6.4.2 for selecting an N3IWF.
When the UE supports connectivity with N3IWF, as well as with ePDG, as specified in TS 23.402 [43], the UE shall perform the procedure in clause 6.3.6.4.3 for selecting either an N3IWF or an ePDG, i.e. for selecting a non-3GPP access node. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.3.6.4.2 Stand-alone N3IWF selection | If the UE is attached to 5GC via an N3IWF that is located in the same country as the country in which the UE is currently located and the AMF has previously indicated support for emergency services over non-3GPP access as defined in clause 5.16.4.1, the UE reuses the existing N3IWF connection for emergency services. Otherwise, the UE terminates any existing N3IWF connection and continues as follows:
If the UE is equipped with a UICC:
- The UE determines whether it is located in the home country or a visited country;
- If the UE is located in the home country, then the UE selects the Home PLMN for emergency services and selects an N3IWF based on the procedure defined in clause 6.3.6.2.
- If the UE is located in a visited country, the UE performs a DNS query using the Visited Country Emergency N3IWF FQDN, as specified in TS 23.003 [19] to determine which PLMNs in the visited country support emergency services in non-3GPP access via N3IWF; and:
- If the DNS response contains one or more records, the UE selects a PLMN that supports emergency services in non-3GPP access via N3IWF. Each record in the DNS response shall contain the identity of a PLMN in the visited country supporting emergency services in non-3GPP access via N3IWF.
- The UE shall consider these PLMNs based on their priorities in the Non-3GPP Access Node Selection Information (if available). If the UE cannot select a PLMN in the Non-3GPP Access Node Selection Information or if non-3GPP Access Node Selection Information is not available, the UE shall attempt to select any PLMN in the list of PLMNs returned in the DNS response.
- Once the UE has selected a PLMN the UE shall select an N3IWF for the selected PLMN as follows:
- If non-3GPP Access Node Selection Information is available for the selected PLMN the UE constructs the Tracking Area Identity based N3IWF FQDN or the Operator Identifier based N3IWF FQDN as indicated in the non-3GPP Access Node Selection Information for the selected PLMN.
- If non-3GPP Access Node Selection Information is not available for the selected PLMN the UE constructs the Operator Identifier based N3IWF FQDN for the selected PLMN.
- If the DNS response does not contain any record, or if the DNS response contains one or more records but the UE fails to select a PLMN that supports emergency services in non-3GPP access, or if the Emergency Registration procedure has failed for all PLMNs supporting emergency services in non-3GPP access, the UE notifies the user that an emergency session cannot be established.
If the UE is not equipped with a UICC, the UE shall perform the emergency N3IWF selection procedure above as if always in a visited country and without using the Non-3GPP Access Node Selection Information, i.e. the UE may construct the Operator Identifier based N3IWF FQDN format based on a PLMN ID obtained via implementation specific means.
When an N3IWF has been selected, the UE initiates an Emergency Registration. If the Emergency Registration fails, the UE shall select another PLMN supporting emergency services in non-3GPP access. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.3.6.3.3 Combined N3IWF/ePDG Selection | If the UE is attached to 5GC via an N3IWF that is located in the same country as the country in which the UE is currently located and the AMF has previously indicated support for emergency services over non-3GPP access as defined in clause 5.16.4.1, the UE reuses the existing N3IWF connection for emergency services. Otherwise, the UE terminates any existing N3IWF connection and performs PLMN and N3IWF or ePDG selection for emergency services.
If the UE is attached to EPC via an ePDG that has indicated support for the emergency services and is located in the same country as the country in which the UE is currently located, the UE reuses the existing ePDG connection for emergency services. Otherwise, the UE terminates the existing ePDG connection, if any and performs PLMN and N3IWF or ePDG selection for emergency services.
PLMN and N3IWF or ePDG selection for emergency services is performed as follows:
If the UE is equipped with a UICC:
- The UE determines whether it is located in the home country or a visited country;
- If the UE is located in the home country the UE selects the Home PLMN for emergency services and selects an N3IWF or ePDG as follows:
- If the Non-3GPP Access Node Selection Information for the HPLMN is available the UE selects first an N3IWF or ePDG based on the Non-3GPP Access Node type preference in the Non-3GPP Access Node Selection Information for the HPLMN. To select an N3IWF the UE uses the N3IWF identifier configuration (if available). If the N3IWF identifier configuration is not available, the UE constructs the FQDN format as indicated by the FQDN format in the Non-3GPP Access Node Selection Information for the HPLMN. To select an ePDG the UE selects the ePDG identified by the configured Emergency ePDG FQDN (if available). If the configured Emergency ePDG FQDN is not available, the UE constructs either the Tracking/Location Area Identity based Emergency ePDG FQDN or the Operator Identifier based Emergency ePDG FQDN as indicated by the FQDN format in the Non-3GPP Access Node Selection Information for the HPLMN.
- If the Non-3GPP Access Node Selection Information is not available, the UE shall first attempt to select an N3IWF following the procedure defined in clause 6.3.6.2 before attempting to select an ePDG. To select an ePDG the UE selects the ePDG identified by the configured Emergency ePDG FQDN (if available). If the configured Emergency ePDG FQDN is not available, the UE constructs the Operator Identifier based Emergency ePDG FQDN.
- If the UE is located in a visited country, the UE performs a DNS query using the Visited Country Emergency FQDN for N3IWF and using the Visited Country Emergency FQDN for ePDG, as specified in TS 23.003 [19] to determine which PLMNs in the visited country support emergency services in non-3GPP access.
- If the DNS responses contain one or more records, the UE selects a PLMN that supports emergency services in non-3GPP access for the UE. Each record in the DNS responses shall contain the identity of a PLMN in the visited country supporting emergency services in non-3GPP access via ePDG or N3IWF.
- The UE shall consider these PLMNs based on their priorities in the Non-3GPP Access Node Selection Information. If the UE cannot select a PLMN in the Non-3GPP Access Node Selection Information or if non-3GPP Access Node Selection Information is not available, the UE shall attempt to select any PLMN in the list of PLMNs returned in the DNS response.
- Once the UE has selected a PLMN the UE shall select an N3IWF or ePDG for the selected PLMN as follows:
- If the Non-3GPP Access Node Selection Information for the PLMN is available the UE selects first an N3IWF or ePDG based on the Non-3GPP Access Node type preference in the Non-3GPP Access Node Selection Information for the PLMN. To select an N3IWF the UE constructs the FQDN format as indicated by the FQDN format in the Non-3GPP Access Node Selection Information for the PLMN. To select an ePDG the UE constructs either the Tracking/Location Area Identity based Emergency ePDG FQDN or the Operator Identifier based Emergency ePDG FQDN as indicated by the FQDN format in the Non-3GPP Access Node Selection Information for the PLMN.
- If the Non-3GPP Access Node Selection Information is not available, the UE shall first attempt to select an N3IWF following the procedure defined in clause 6.3.6.2 before attempting to select an ePDG. To select an ePDG the UE constructs the Operator Identifier based Emergency ePDG FQDN.
- If the DNS response does not contain any record, or if the DNS response contains one or more records but the UE fails to select a PLMN that supports emergency services in non-3GPP access, or if the Emergency Registration procedure has failed for all PLMNs supporting emergency services in non-3GPP access, the UE notifies the user that emergency session cannot be established.
If the UE is not equipped with a UICC, the UE shall perform the emergency ePDG/N3IWF selection procedure above as if always in a visited country and without using the Non-3GPP Access Node Selection Information, i.e. the UE may construct the Operator Identifier FQDN for N3IWF or ePDG based on a PLMN ID obtained via implementation specific means.
When a N3IWF has been selected, the UE initiates an Emergency Registration. If the Emergency Registration fails, the UE shall attempt to select an ePDG before selecting another PLMN supporting emergency services in non-3GPP access. When an ePDG has been selected, the UE initiates an Emergency Registration. If the Emergency Registration fails, the UE shall attempt to select a N3IWF before selecting another PLMN supporting emergency services in non-3GPP access. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.3.7 PCF discovery and selection | |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.3.7.0 General principles | Clause 6.3.7.0 describes the underlying principles for PCF selection and discovery:
- There may be multiple and separately addressable PCFs in a PLMN.
- The PCF must be able to correlate the AF service session established over N5 or Rx with the associated PDU Session (Session binding) handled over N7.
- It shall be possible to deploy a network so that the PCF may serve only specific DN(s). For example, Policy Control may be enabled on a per DNN basis.
- Unique identification of a PDU Session in the PCF shall be possible based on the (UE ID, DNN)-tuple, the (UE (IP or MAC) Address(es), DNN)-tuple and the (UE ID, UE (IP or MAC) Address(es), DNN). |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.3.7.1 PCF discovery and selection for a UE or a PDU Session | PCF discovery and selection functionality is implemented in AMF, SMF, SCP and PCF for the PDU Session and follows the principles in clause 6.3.1.
When the NF service consumer performs PCF discovery and selection for a UE, the following applies:
- The AMF may utilize the NRF to discover the candidate PCF instance(s) for a UE. In addition, PCF information may also be locally configured in the AMF. The AMF selects a PCF instance based on the available PCF instances obtained from the NRF or locally configured information in the AMF, depending on operator's policies.
In the non roaming case, the AMF selects a PCF instance for AM Policy Association and selects the same PCF instance for UE Policy Association. In the roaming case, the AMF selects a V-PCF instance for AM Policy Association and selects the same V-PCF instance for UE Policy Association.
The PCF for the PDU Session selects a (V-)PCF instance for UE Policy Association.
The following factors may be considered at PCF discovery and selection for Access and Mobility policies and UE policies:
- SUPI; the AMF selects a PCF instance based on the SUPI range the UE's SUPI belongs to or based on the results of a discovery procedure with NRF using the UE's SUPI as input for PCF discovery.
- S-NSSAI(s). In the roaming case, the AMF selects the V-PCF instance based on the S-NSSAI(s) of the VPLMN and selects the H-PCF instance based on the S-NSSAI(s) of the HPLMN.
- PCF Set ID.
- PCF Group ID of the UE's SUPI.
NOTE 1: The AMF can infer the PCF Group ID the UE's SUPI belongs to, based on the results of PCF discovery procedures with NRF. The AMF provides the PCF Group ID the SUPI belongs to to other PCF NF consumers as described in TS 23.502 [3].
- DNN replacement capability of the PCF.
- Slice replacement capability of the PCF.
- PCF Selection Assistance Info and PCF ID(s) serving the established PDU Sessions/PDN Connections received from UDM. In case PCF Selection Assistance Info and PCF ID(s) are received from the UDM, the AMF selects the same PCF instance serving the combination of DNN and S-NSSAI as indicated by the PCF Selection Assistance Info, if multiple DNN, S-NSSAI combinations are provided, the AMF selects the DNN,S-NSSAI using local configuration. In case PCF ID(s) are not received, e.g. EPS interworking is not supported, the AMF selects the PCF instance by considering other above factors.
- URSP delivery in EPS capability of the PCF.
When the NF service consumer performs PCF discovery and selection for a PDU Session, the following applies:
- The SMF may utilize the NRF to discover the candidate PCF instance(s) for a PDU Session. In addition, PCF information may also be locally configured in the SMF. The SMF selects a PCF instance based on the available PCF instances obtained from the NRF or locally configured information in the SMF, depending on operator's policies.
The following factors may be considered at PCF discovery and selection for a PDU Session:
a) Local operator policies.
b) Selected Data Network Name (DNN).
c) S-NSSAI of the PDU Session. In the LBO roaming case, the SMF selects the PCF instance based on the S-NSSAI of the VPLMN. In the home routed roaming case, the H-SMF selects the H-PCF instance based on the S-NSSAI of the HPLMN.
d) SUPI; the SMF selects a PCF instance based on the SUPI range the UE's SUPI belongs to or based on the results of a discovery procedure with NRF using the UE's SUPI as input for PCF discovery.
e) PCF selected by the AMF for the UE.
f) MA PDU Session capability of the PCF, for an MA PDU Session.
g) The PCF Group ID provided by the AMF to the SMF.
h) PCF Set ID.
i) Same PCF Selection Indication.
j) URSP delivery in EPS capability of the PCF.
In the case of delegated discovery and selection in SCP, the SMF includes the factors b) - h), j), if available, in the first request.
The selected PCF instance for serving the UE and the selected PCF instance for serving a PDU Session of this UE may be the same or may be different.
In the following scenarios, information about the PCF instance that has been selected (i.e. the PCF ID, PCF Set Id and, if PCF Set Id is not available, the PCF Group ID (if available)) may be forwarded to another NF. If the NF service consumer performs discovery and selection, this NF may use this PCF instance. If the NF service consumer performs delegated discovery and selection, this NF may include PCF ID, PCF Set Id and, if PCF Set Id is not available, the PCF Group ID (if available) in the request and the SCP may use this information to select the PCF instance (discovery may still be needed depending on what level of information is sent by the AMF, e.g. the endpoint address of the PCF instance may not be present):
When NF service consumer performs PCF discovery and selection, the following applies:
- During AMF relocation, the target AMF may receive a PCF ID, PCF Set Id and, if PCF Set Id is not available, the PCF Group ID (if available) from the source AMF to enable the usage of the same PCF by the target AMF and the target AMF may decide based on operator policy either to use the same PCF or select a new PCF.
- The AMF may, based on operator policies, forward the selected PCF to SMF instance(s) during the PDU Session Establishment procedure(s) to enable the usage of the same PCF for the AMF and the SMF instance(s). The SMF may decide based on operator policy either to use the same PCF or select a new PCF. If combination of the DNN and S-NSSAI of the PDU Session matches one of the combination of the DNN and S-NSSAI included in the PCF Selection Assistance info received from UDM, the AMF shall forward Same PCF Selection Indication together with the selected PCF to SMF instance during the PDU Session Establishment procedure. In case that the Same PCF Selection Indication is received together with the PCF ID, the SMF shall select the same PCF instance for SM Policy Control.
- In the roaming case, the AMF may, based on operator policies, e.g. roaming agreement, select the H-PCF in addition to the V-PCF for a UE by performing the PCF discovery and selection as described above. The AMF may send the ID and/or endpoint address (e.g. URI) of the selected H-PCF instance to the V-PCF during the UE Policy Association establishment procedure.
When the SMF receives a redirection indication with PCF ID from the PCF for the PDU Session, the SMF shall terminate the current SM Policy Association and reselects a PCF based on the received PCF ID. The SMF shall then establish an SM Policy Association with the reselected PCF.
In the case of delegated discovery and selection in the SCP, the following applies:
- The selected PCF instance may include the PCF Id, PCF Set Id and, if PCF Set Id is not available, the PCF Group ID (if available) in the response to the AMF.
NOTE 2: The selected (V-)PCF instance can include the binding indication, including the (V-)PCF ID and possibly PCF Set ID in the response to the AMF as described in clause 6.3.1.0.
- The AMF first establishes an AM Policy Association; when forwarding the related request message the SCP discovers and selects a PCF instance. Unless binding information is provided in the response to that request the SCP adds the NF function producer ID it selected, i.e. PCF ID, into the response and the AMF uses the received PCF ID and available binding information as discovery and selection parameters for the request to establish the UE Policy Association towards the SCP. The SCP selects the (V-)PCF instance for UE Policy Association based on the received discovery and selection parameters.
- During AMF relocation, the AMF may receive a PCF ID, PCF Set Id and, if PCF Set Id is not available, the PCF Group ID (if available) from the source AMF to enable the usage of the same PCF instance by the AMF. The AMF may decide based on operator policy either to use the old PCF instance or select another PCF instance. If the AMF decides to use the old PCF, the AMF includes the PCF ID PCF Set Id and if PCF Set Id is not available, the PCF Group ID (if available) as received from the source AMF in the AM Policy Association update request to the SCP.
- The AMF may, based on operator policies, forward the selected PCF ID, PCF Set Id and, if PCF Set Id is not available, the PCF Group ID (if available) to the SMF during the PDU Session Establishment procedure to enable the usage of the same PCF for the AMF and the SMF. The SMF may include that information in the request in discovery and selection parameters to the SCP. The SCP may decide based on operator policy either to use the indicated PCF instance or select another PCF instance.
- In the roaming case, the AMF performs discovery and selection of the H-PCF from NRF as described in this clause. The AMF may indicate the maximum number of H-PCF instances to be returned from NRF, i.e. H-PCF selection at NRF. The AMF uses the received V-PCF ID and endpoint address (e.g. URI) and available binding information received during the AM Policy Association procedure to send the UE Policy Association establishment request, which may also include the H-PCF ID and/or endpoint address (e.g. URI), to the SCP. The SCP discovers and selects the V-PCF. The V-PCF sends an UE Policy Association establishment request towards the HPLMN, which may include the H-PCF ID and/or endpoint address (e.g. URI) as a discovery and selection parameter to SCP. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.3.7.2 Providing policy requirements that apply to multiple UE and hence to multiple PCF | An authorized Application Function may, via the NEF, provide policy requirements that apply to multiple UE(s) (which, for example, belong to group of UE(s) defined by subscription or to any UE). Such policy requirements shall apply to any existing or future PDU Sessions that match the parameters in the AF request and they may apply to multiple PCF instance(s).
NOTE: Application Function influence on traffic routing described in clause 5.6.7 is an example of such requirement.
After relevant validation of the AF request (and possible parameter mapping), the NEF stores this request received from the AF into the selected UDR instance as the Data Subset of the Application data. The possible parameter mapping includes mapping UE (group) identifiers provided by the AF to identifiers used within the 5GC, e.g. from GPSI to SUPI and/or from External Group Identifier to Internal-Group Identifier. Parameter mapping may also include mapping from the identifier of the Application Function towards internal identifiers such as the DNN and/or the S-NSSAI.
PCF(s) that need to receive AF requests that targets a DNN (and slice) and/or a group of UEs subscribe to receive notifications from the UDR about such AF request information. The PCF(s) can be configured (e.g. by OAM) to subscribe to receive notification of such AF request information from the UDR(s). The PCF(s) take(s) the received AF request information into account when making policy decisions for existing and future relevant PDU Sessions. In the case of existing PDU Sessions, the policy decision of the PCF instance(s) may trigger a PCC rule(s) change from the PCF to the SMF.
The PCF subscription to notifications of AF requests described above may take place during PDU Session Establishment or PDU Session Modification, when the PCF(s) receive request(s) from the SMF for policy information related to the DNN (and slice) and/or the Internal-Group Identifier of UEs. For the PCF(s) that have subscribed to such notifications, the UDR(s) notify the PCF(s) of any AF request update.
The NEF associates the AF request with information allowing to later modify or delete the AF request in the UDR; it associates the AF request with:
- When the AF request targets PDU Sessions established by "any UE": the DNN, the slicing information target of the AF request,
- When the request targets PDU Sessions established by UE(s) belonging to an Internal-Group: the DNN, the slicing information and the Internal-Group Identifier target of the application request.
- The AF transaction identifier in the AF request. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.3.7.3 Binding an AF request targeting a UE address to the relevant PCF | Binding an AF request targeting a UE address to the relevant PCF instance is described in clause 6.1.1.2 of TS 23.503 [45]. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.3.7.4 Binding an AF request targeting a UE to the relevant PCF | Binding an AF request targeting a UE to the relevant PCF is described in clause 6.1.1.2a of TS 23.503 [45]. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.3.8 UDM discovery and selection | The NF consumer or the SCP performs UDM discovery to discover a UDM instance that manages the user subscriptions.
If the NF consumer performs discovery and selection, the NF consumers shall utilize the NRF to discover the UDM instance(s) unless UDM information is available by other means, e.g. locally configured on NF consumers. The UDM selection function in NF consumers selects a UDM instance based on the available UDM instances (obtained from the NRF or locally configured).
The UDM selection functionality is applicable to both 3GPP access and non-3GPP access.
The UDM selection functionality in NF consumer or in SCP should consider one of the following factors:
1. Home Network Identifier (e.g. MNC and MCC, realm) of SUCI/SUPI, along with the selected NID (provided by the NG-RAN) in the case of SNPN, UE's Routing Indicator and optionally Home Network Public Key identifier (e.g. in the case that Routing Indicator is not enough to provide SUPI range granularity).
NOTE 1: The UE provides the SUCI to the AMF, which contains the Routing Indicator and Home Network Public Key identifier as defined in TS 23.003 [19] during initial registration. The AMF provides the UE's Routing Indicator and optionally Home Network Public Key identifier to other NF consumers (of UDM) as described in TS 23.502 [3].
NOTE 2: The usage of Home Network Public Key identifier for UDM discovery is limited to the scenario where the NF consumers belong to the same PLMN as AUSF.
NOTE 3: In the case of SNPN and the UE provides an IMSI type SUCI to the AMF and the SUCI provided by UE or the SUPI derived from the SUCI is for an SNPN served by the AMF, the AMF uses the selected NID provided by the NG-RAN together with the selected PLMN ID (from IMSI) or the Routing Indicator provided by the UE within the SUCI for UDM selection. In the case of SNPN and the UE provides an NSI type SUCI to the AMF, the AMF uses the Home Network Identifier and Routing Indicator of SUCI/SUPI for selection of UDM.
When the UE's Routing Indicator is set to its default value as defined in TS 23.003 [19], the UDM NF consumer can select any UDM instance within the home network of the SUCI/SUPI.
2. UDM Group ID of the UE's SUPI.
NOTE 4: The AMF can infer the UDM Group ID the UE's SUPI belongs to, based on the results of UDM discovery procedures with NRF. The AMF provides the UDM Group ID the SUPI belongs to other UDM NF consumers as described in TS 23.502 [3].
3. SUPI or Internal Group ID; the UDM NF consumer selects a UDM instance based on the SUPI range the UE's SUPI belongs to or based on the results of a discovery procedure with NRF using the UE's SUPI or Internal Group ID as input for UDM discovery.
4. GPSI or External Group ID; UDM NF consumers which manage network signalling not based on SUPI/SUCI (e.g. the NEF) select a UDM instance based on the GPSI or External Group ID range the UE's GPSI or External Group ID belongs to or based on the results of a discovery procedure with NRF using the UE's GPSI or External Group ID as input for UDM discovery.
In the case of delegated discovery and selection in SCP, NF consumer shall include one of these factors in the request towards SCP. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.3.9 UDR discovery and selection | Multiple instances of UDR may be deployed, each one storing specific data or providing service to a specific set of NF consumers as described in clause 4.2.5. In segmented UDR deployment, different instances of UDR store the data for different Data Sets and Data Subsets or for different users. A UDR instance can also store application data that applies on any UE, i.e. all subscribers of the PLMN.
If the NF service consumer performs discovery and selection, the NF consumer shall utilize the NRF to discover the appropriate UDR instance(s) unless UDR instance information is available by other means, e.g. locally configured on NF consumer. The UDR selection function in NF consumers is applicable to both 3GPP access and non-3GPP access. The NF consumer or the SCP shall select a UDR instance that contains relevant information for the NF consumer, e.g. UDM/SCP selects a UDR instance that contains subscription data, while NEF/SCP (when used to access data for exposure) selects a UDR that contains data for exposure; or PCF/SCP selects a UDR that contains Policy Data and/or Application Data.
For the resolution of the NF Group ID corresponding to a subscriber identifier, the UDR NF consumer (e.g. NRF, SCP) shall select a UDR instance that supports the Nudr_GroupIDMap service.
For data management procedures, the UDR selection function in UDR NF consumers considers the Data Set Identifier of the data to be managed in UDR (see UDR service definition in clause 5.2.12 of TS 23.502 [3]). Additionally, the UDR selection function in UDR NF consumers should consider one of the following factors when available to the UDR NF consumer when selecting a UDR that stores the required Data Set(s) and Data Subset(s):
1. UDR Group ID the UE's SUPI belongs to.
2. SUPI; e.g. the UDR NF consumer selects a UDR instance based on the SUPI range the UE's SUPI belongs to or based on the results of a discovery procedure with NRF using the UE's SUPI as input for UDR discovery.
3. GPSI or External Group ID; e.g. UDR NF consumers select a UDR instance based on the GPSI or External Group ID range the UE's GPSI or External Group ID belongs to or based on the results of a discovery procedure with NRF using the UE's GPSI or External Group ID as input for UDR discovery.
4. UDR capability to store application data that is applicable on any UE (i.e. all subscribers of the PLMN).
In the case of delegated discovery and selection, the NF consumer shall include the available factors in the request towards SCP. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.3.10 SMSF discovery and selection | The SMSF selection function is supported by the AMF and is used to allocate an SMSF instance that shall manage the SMS.
If the "SMS supported" indication is included in the Registration Request by the UE, the AMF checks SMS subscription from the UDM for the UE on whether the SMS is allowed for the UE.
If the SMS is allowed and the UE Context stored in AMF includes an SMSF address, the AMF uses the SMSF address included in UE Context (according to Table 5.2.2.2.2-1 of TS 23.502 [3]).
If the SMS is allowed and the UE Context stored in AMF does not include an SMSF address, the AMF discovers and selects an SMSF to serve the UE.
The SMSF selection may be based on the following methods:
- SMSF instance(s) address(es) preconfigured in the AMF (i.e. SMSF FQDN or IP addresses); or
- SMSF information available in the serving PLMN if received from an old AMF or the UDM; or
- The AMF invokes Nnrf_NFDiscovery service operation from NRF to discover SMSF instance as described in clause 5.2.7.3.2 of TS 23.502 [3].
For roaming scenario, the AMF discovers and selects an SMSF in VPLMN.
If the NF consumer performs discovery and selection via NRF, the SMSF selection function in the NF consumer selects a SMSF instance based on the available SMSF instances obtained from the NRF.
In the case of delegated discovery and selection in SCP, the NF consumer shall include all available factors in the request towards SCP. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.3.11 CHF discovery and selection | The CHF discovery and selection function is supported by the SMF, the AMF, the SMSF and the PCF. It is used by the SMF to select a CHF that manages the online charging or offline charging for a PDU Session of a subscriber. It is used by the AMF to select a CHF that manages the online charging or offline charging for 5G connection and mobility of a subscriber. It is used by the SMSF to select a CHF that manages the online charging or offline charging for the SMS over NAS transactions of a subscriber. It is used by the PCF to select a CHF that manages the spending limits for a subscriber and/or a PDU Session of a subscriber.
For the PCF to select the CHF, the address(es) of the CHF, including the Primary CHF address and the Secondary CHF address, may be:
- stored in the UDR as part of the PDU Session policy control subscription information as defined in clause 6.2.1.3 of TS 23.503 [45].
- stored in the UDR as part of the UE context policy control subscription information as defined in clause 6.2.1.3 of TS 23.503 [45].
- stored in the UDR as part of the Access and Mobility policy control subscription information as defined in clause 6.2.1.3 of TS 23.503 [45].
- locally configured in the PCF based on operator policies.
- discovered using NRF as described in in clause 6.1 of TS 32.290 [67].
NOTE 1: The operator can perform the above UDR provisioning or local configuration in a consistent manner such that the same CHF address is used for SM policy, AM policy and UE policy. If NRF discovery is used, it is up to the PCF logic (or SCP logic when working in Delegated Discovery mode) and operator configuration to guarantee the CHF address consistency.
The address(es) of the CHF shall be applicable for all services provided by the CHF.
The CHF address(es) that a stored in the UDR or configured in the PCF may be complemented by the associated CHF instance ID(s) and CHF set ID(s) (see clause 6.3.1.0) stored or configured in the same location.
The CHF address(es) retrieved from the UDR and possible associated CHF instance ID(s) and CHF set ID(s) take precendence over the locally configured CHF address(es) and possible associated CHF instance ID(s) and CHF set ID(s) and over the CHF address(es) discoverred by the NRF. If no CHF address(es) is received from the UDR, the PCF selects, based on operator policies, either the CHF addresse(es) provided by NRF, or the locally configured CHF address(es) and possible associated CHF instance ID(s) and CHF set ID(s).
If the PCF has a CHF set ID but no CHF instance ID associated to the CHF address(es) in the same location, the CHF instance within the CHF set may change. If the PCF is not able to reach the CHF address(es), it should query the NRF for other CHF instances within the CHF set.
If the PCF received a CHF set ID and a CHF instance ID associated to the CHF address(es) in the same location, the CHF service instance within the CHF may change. If an PCF is not able to reach the CHF address(es), it should query the NRF for other CHF service instances within the CHF.
In the non-roaming case it is possible to either:
a) Have the SMF select the same CHF that is selected by the PCF for the PDU Session. In this case, operator policies in the PCF indicate it to provide the selected CHF address(es) and, if available, the associated CHF instance ID(s) and/or CHF set ID(s) in the PDU Session related policy information to the SMF as described in Table 6.4-1 of TS 23.503 [45] and the SMF applies the CHF address and if available, the associated CHF instance ID(s) and/or CHF set ID(s) passed from the PCF as defined in clause 5.1.8 of TS 32.255 [68] or
b) Have the SMF select a CHF based on other criteria as defined in clause 5.1.8 of TS 32.255 [68].
In the Home Routed roaming case, the above text shall apply with the change that SMF is replaced by H-SMF, PCF is replaced by H-PCF, CHF is replaced by H-CHF and for b) the other criteria is defined in clause 5.1.9.2 of TS 32.255 [68].
In the non-roaming case, it is possible to either:
a) Have the AMF select the same CHF that is selected by the PCF for the UE. In this case operator policies in the PCF indicate it to provide the selected CHF address(es) and, if available, the associated CHF instance ID(s) and/or CHF set ID(s) in the Access and mobility related policy information and/or in the UE Policy Association supplementary information to the AMF as described in Table 6.5-1 and Table 6.6.7-1 of TS 23.503 [45] respectively and the AMF applies the CHF address and if available, the associated CHF instance ID(s) and/or CHF set ID(s) passed from the PCF as defined in clause 5.1.3 of TS 32.256 [114] or
b) Have the AMF select a CHF based on other criteria as defined in clause 5.1.3 of TS 32.256 [114].
In the roaming case, the above text shall apply with the change that PCF is replaced by H-PCF, CHF is replaced by H-CHF, Access and mobility related policy information is not relevant, UE Policy Association supplementary information is between the AMF and the V-PCF and between the V-PCF and the H-PCF and for b) the other criteria is defined in clause 5.1.5.2 of TS 32.256 [114].
NOTE 2: Clause 5.1.2 of TS 32.256 [114] describes the charging reporting requirements on the AMF in the roaming scenario.
How the CHF is selected by the SMSF is defined in clause 5.4 of TS 32.274 [118].
If the NF consumer performs discovery and selection via NRF, the CHF selection function in NF consumers selects a CHF instance based on the available CHF instances obtained from the NRF.
The CHF selection functionality in NF consumer or in SCP should consider one of the following factors:
1. CHF Group ID of the UE's SUPI.
NOTE 3: The NF Consumer can infer the CHF Group ID the UE's SUPI belongs to, based on the results of CHF discovery procedures with NRF.
2. SUPI; the NF consumer selects a CHF instance based on the SUPI range the UE's SUPI belongs to or based on the results of a discovery procedure with NRF using the UE's SUPI as input for CHF discovery.
In the case of delegated discovery and selection in SCP, the NF consumer shall include all available factors in the request towards SCP. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.3.12 Trusted Non-3GPP Access Network selection | |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.3.12.1 General | Clause 6.3.12 specifies how a UE, which wants to establish connectivity via trusted non-3GPP access and is not operating in SNPN access mode, selects a PLMN and a trusted non-3GPP access network (TNAN) to connect to.
NOTE: For UE operating in SNPN access mode refer to clause 5.30.2.13.
How the UE decides to use trusted non-3GPP access is not specified in this document. As an example, a UE may decide to use trusted non-3GPP access for connecting to 5GC in a specific PLMN based on:
- the UE implementation-specific criteria; or
- the UE configuration, e.g. the UE may be configured to try first the trusted non-3GPP access procedures; or
- the UE capabilities, e.g. the UE may support only the trusted non-3GPP access procedures; or
- the advertised capabilities of the discovered non-3GPP access networks, e.g. one or more available non-3GPP access networks advertise support of trusted connectivity to 5GC in a specific PLMN.
An example deployment scenario is schematically illustrated in Figure 6.3.12.1-1 below. In this scenario, the UE has discovered five non-3GPP access networks, which are WLAN access networks. These WLANs advertise information about the PLMNs they interwork with, e.g. by using the ANQP protocol, as defined in the HS2.0 specification [85]. Each WLAN may support "S2a connectivity" and/or "5G connectivity" to one or more PLMNs. Before establishing connectivity via trusted non-3GPP access, the UE needs to select (a) a PLMN, (b) a non-3GPP access network that provide trusted connectivity this this PLMN and (c) a connectivity type, i.e. either "5G connectivity" or "S2a connectivity".
Each non-3GPP access network may advertise one or more of the following PLMN lists:
1) A PLMN List-1, which includes PLMNs with which "AAA connectivity" is supported. A non-3GPP access network supports "AAA connectivity" with a PLMN when it deploys an AAA function that can connect with a 3GPP AAA Server/Proxy in this PLMN, via an STa interface (trusted WLAN to EPC), or via an SWa interface (untrusted WLAN to EPC); see TS 23.402 [43].
2) A PLMN List-2, which includes PLMNs with which "S2a connectivity" is supported. A non-3GPP access network supports "S2a connectivity" with a PLMN when it deploys a TWAG function that can connect with a PGW in this PLMN, via an S2a interface; see clause 16 of TS 23.402 [43].
3) A PLMN List-3, which includes PLMNs with which "5G connectivity" is supported. A non-3GPP access network supports "5G connectivity" with a PLMN when it deploys a TNGF function that can connect with an AMF function and an UPF function in this PLMN via N2 and N3 interfaces, respectively; see clause 4.2.8.
When the UE wants to discover the PLMN List(s) supported by a non-3GPP access network and the non-3GPP access network supports ANQP, the UE shall send an ANQP query to the non-3GPP access network requesting "3GPP Cellular Network" information. If the non-3GPP access network supports interworking with one or more PLMNs, the response received by the UE includes a "3GPP Cellular Network" information element containing one or more of the above three PLMN Lists. The PLMN List-1 and the PLMN List-2 are specified in TS 23.402 [43] and indicate support of interworking with EPC in one or more PLMNs. The PLMN List-3 is a list used to indicate support of interworking with 5GC in one or more PLMNs. When the non-3GPP access network does not support ANQP, how the UE discovers the PLMN List(s) supported by the non-3GPP access network is not defined in the present specification.
The UE determines if a non-3GPP access network supports "trusted connectivity" to a specific PLMN by receiving the PLMN List-2 and the PLMN List-3 advertised by this access network. If this PLMN is not included in any of these lists, then the non-3GPP access network can only support connectivity to an ePDG or N3IWF in the PLMN (i.e. "untrusted connectivity").
Figure 6.3.12.1-1: Example deployment scenario for trusted Non-3GPP access network selection |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.3.12.2 Access Network Selection Procedure | The steps below specify the steps executed by the UE when the UE wants to select and connect to a PLMN over trusted non-3GPP access. Note that the UE executes these steps before connecting to a trusted non-3GPP access network. This is different from the untrusted non-3GPP access (see clause 6.3.6, "N3IWF selection"), where the UE first connects to a non-3GPP access network, it obtains IP configuration and then proceeds to PLMN selection and ePDG/N3IWF selection. In the case of trusted non-3GPP access, the UE uses 3GPP-based authentication for connecting to a non-3GPP access, so it must first select a PLMN and then attempt to connect to a non-3GPP access.
Step 1: The UE constructs a list of available PLMNs, with which trusted connectivity is supported. This list contains the PLMNs included in the PLMN List-2 and PLMN List-3, advertised by all discovered non-3GPP access networks. For each PLMN the supported type(s) of trusted connectivity is also included.
a. In the example shown in Figure 6.3.12.1-1, the list of available PLMNs includes:
- PLMN-a: "S2a connectivity", "5G connectivity"
- PLMN-b: "5G connectivity"
- PLMN-c: "S2a connectivity", "5G connectivity"
- PLMN-d: "S2a connectivity"
Step 2: The UE selects a PLMN that is included in the list of available PLMNs, as follows:
a. If the UE is connected to a PLMN via 3GPP access and this PLMN is included in the list of available PLMNs, the UE selects this PLMN. If this PLMN is not included in the list of available PLMNs, but it is included in the "Non-3GPP access node selection information" in the UE (see clause 6.3.6.1), the UE selects this PLMN and executes the combined ePDG/N3IWF selection procedure specified in clause 6.3.6.3.
b. Otherwise (the UE is not connected to a PLMN via 3GPP access, or the UE is connected to a PLMN via 3GPP access but this PLMN is neither in the list of available PLMNs nor in the "Non-3GPP access node selection information"), the UE determines the country it is located in by using implementation specific means.
i) If the UE determines to be located in its home country, then:
- The UE selects the HPLMN, if included in the list of available PLMNs. Otherwise, the UE selects an E-HPLMN (Equivalent HPLMN), if an E-HPLMN is included in the list of available PLMNs. If the list of available PLMNs does not include the HPLMN and does not include an E-HPLMN, the UE stops the procedure and may attempt to connect via untrusted non-3GPP access (i.e. it may execute the N3IWF selection procedure specified in clause 6.3.6).
ii) If the UE determines to be located in a visited country, then:
- The UE determines if it is mandatory to select a PLMN in the visited country, as follows:
- If the UE has IP connectivity (e.g. the UE is connected via 3GPP access), the UE sends a DNS query and receives a DNS response that indicates if a PLMN must be selected in the visited country. The DNS response includes also a lifetime that denotes how long the DNS response can be cached for. The FQDN in the DNS query shall be different from the Visited Country FQDN (see TS 23.003 [19]) that is used for ePDG/N3IWF selection. The DNS response shall not include a list of PLMNs that support trusted connectivity in the visited country, but shall only include an indication of whether a PLMN must be selected in the visited country or not.
- If the UE has no IP connectivity (e.g. the UE is not connected via 3GPP access), then the UE may use a cached DNS response that was received in the past, or may use local configuration that indicates which visited countries mandate a PLMN selection in the visited country.
- If the UE determines that it is not mandatory to select a PLMN in the visited country and the HPLMN or an E-HPLMN is included in the list of available PLMNs, then the UE selects the HPLMN or an E-HPLMN, whichever is included in the list of available PLMNs.
- Otherwise, the UE selects a PLMN in the visited country by considering, in priority order, the PLMNs, first, in the User Controlled PLMN Selector list and, next, in the Operator Controlled PLMN Selector list (see TS 23.122 [17]). The UE selects the highest priority PLMN in a PLMN Selector list that is also included in the list of available PLMNs;
- If the list of available PLMNs does not include a PLMN that is also included in a PLMN Selector list, the UE stops the procedure and may attempt to connect via untrusted non-3GPP access.
c. In the example shown in Figure 6.3.12.1-1, the UE may select PLMN-c, for which "S2a connectivity" and "5G connectivity" is supported.
Step 3: The UE selects the type of trusted connectivity ("S2a connectivity" or "5G connectivity") for connecting to the selected PLMN, as follows:
a. If the list of available PLMNs indicates that both "S2a connectivity" and "5G connectivity" is supported for the selected PLMN, then the UE shall select "5G connectivity" because it is the preferred type of trusted access.
b. Otherwise, if the list of available PLMNs indicates that only one type of trusted connectivity (either "S2a connectivity" or "5G connectivity") is supported for the selected PLMN, the UE selects this type of trusted connectivity.
c. In the example shown in Figure 6.3.12.1-1, the UE may select PLMN-c and "5G connectivity". There are two non-3GPP access networks that support "5G connectivity" to PLMN-c: the WLAN access network 2 and the WLAN access network 4.
Step 4: Finally, the UE selects a non-3GPP access network to connect to, as follows:
a. The UE puts the available non-3GPP access networks in priority order. For WLAN access, the UE constructs a prioritized list of WLAN access networks by using the WLANSP rules (if provided) and the procedure specified in clause 6.6.1.3 of TS 23.503 [45]. When the UE supports the selection of Trusted access supporting the network slices it desires to use and has received extended WLANSP rule as specified in clause 6.6.1.1 of TS 23.503 [45], the UE selects the non-3GPP access network with the SSID(s) which can access to the TNGF supporting the S-NSSAI needed by the UE. If the UE is not provided with WLANSP rules, the UE constructs the prioritized list of WLAN access networks by using an implementation specific procedure. For other types of non-3GPP access, the UE may use access specific information to construct this prioritized list.
b. From the prioritized list of non-3GPP access networks, the UE selects the highest priority non-3GPP access network that supports the selected type of trusted connectivity to the selected PLMN.
c. In the example shown in Figure 6.3.12.1-1, the UE selects either the WLAN access network 2 or the WLAN access network 4, whichever has the highest priority in the prioritized list of non-3GPP access networks.
d. Over the selected non-3GPP access network, the UE starts the 5GC registration procedure specified in clause 4.12a.2.2 of TS 23.502 [3].
e. If the AMF detects the UE is using a wrong TNGF, the AMF may trigger a UE policy update and reject the UE registration
During the registration procedure the AMF may determine if the TNGF selected by the UE is suitable for the S-NSSAI(s) requested by the UE considering the UE subscription. If the AMF determines that a different TNGF should be selected as described in clause 4.12a.2.2 of TS 23.502 [3], the AMF:
- may, if the UE supports slice-based TNGF selection, triggers the UE Policy Association Establishment or UE Policy Association Update procedure to provide the UE with updated TNGF selection information; when the AMF is informed by the PCF that the update of UE policy information on the UE is completed as described in clause 4.12a.2.2 of TS 23.502 [3], the AMF releases UE Policy Association if the UE is not registered over 3GPP access before proceeding to the Registration Reject over trusted non-3GPP access;
NOTE 1: To enable the V-PCF to provide the UE with Slice-specific TNGF selection information in the roaming case, the AMF provides the V-PCF with the Configured NSSAI for the serving PLMN during the UE Policy Association Establishment/Update procedure.
- shall send a Registration Reject message to the UE. The AMF may include target TNAN information (SSID, TNGF ID) in the Registration Reject so that the UE can, if supported by the UE, use the target TNAN information to try again to register to 5GC if the UE wishes to send the same Requested NSSAI as during the previous Registration Request. The target TNAN information only applies to the one TNAN selection performed by the UE just after receiving the Registration Reject.
NOTE 2: A TNGF ID sent within a Registration Reject message to a UE trying to register over Trusted Non-3GPP access corresponds to a UE side interface of a TNGF while a TNGF Identifier of N3 terminations provided by a TNGF over N2 and defined in clause 6.3.3.3 corresponds to an internal 5GC identifier related with a TNGF.
The AMF may determine the target TNAN based on the list of supported TAs and the corresponding list of supported slices for each TA obtained as defined in clause 5.15.8 and considering UE location.
NOTE 3: The operator is assumed to ensure that UEs that do not support slice-based TNGF selection always select a TNGF that supports at least one slice requested by the UE. This is to avoid unnecessary and potentially repetitive rejections of those UEs. To ensure this, the operator is assumed to provide identifiers of TNGFs that only support a subset of the slices configured in the network only to UEs that support slice-based TNGF selection.
6.3.12a Access Network selection for devices that do not support 5GC NAS over WLAN
6.3.12a.1 General
As specified in clause 4.2.8.5, devices that do not support 5GC NAS signalling over WLAN access (referred to as "Non-5G-Capable over WLAN" devices, or N5CW devices for short), may access 5GC in a PLMN or an SNPN via a trusted WLAN access network that supports a TWIF function. The following clause specifies (a) how a N5CW device selects a PLMN and (b) how it selects a trusted WLAN access network that can provide "5G connectivity-without-NAS" to the selected PLMN. This selection procedure is called access network selection.
NOTE: For N5CW device accessing an SNPN refer to clause 5.30.2.15.
Each WLAN access network that provides "5G connectivity-without-NAS" advertises with ANQP a list of PLMNs with which "5G connectivity-without-NAS" is supported. This list is called PLMN List-4 and is different from the PLMN List-1, PLMN List-2 and PLMN List-3 defined in clause 6.3.12. A WLAN advertises the PLMN List-4, when the WLAN supports a TWIF function.
6.3.12a.2 Access Network Selection Procedure
The steps executed by a N5CW device for access network selection are specified below and are very similar with the corresponding steps executed by a UE that supports NAS; see clause 6.3.12.2.
Step 1: The N5CW device constructs a list of available PLMNs. This list contains the PLMNs included in the PLMN List-4 advertised by all discovered WLAN access networks.
a. The N5CW device discovers the PLMN List-4 advertised by all discovered WLAN access networks by sending an ANQP query to each discovered WLAN access network. The ANQP query shall request "3GPP Cellular Network" information. If a WLAN access network supports interworking with one or more PLMNs, the ANQP response received by the N5CW device includes a "3GPP Cellular Network" information element containing one or more of the following lists: PLMN List-1, PLMN List-2, PLMN List-3 and PLMN List-4. The PLMN List-1, PLMN List-2 and PLMN List-3 are defined in clause 6.3.12. The PLMN List-4 includes the PLMNs with which "5G connectivity-without-NAS" is supported.
Step 2: The N5CW device selects a PLMN that is included in the list of available PLMNs as follows.
a. If the N5CW device is connected to a PLMN via 3GPP access and this PLMN is included in the list of available PLMNs, then the N5CW device selects this PLMN.
b. Otherwise (the N5CW device is not connected to a PLMN via 3GPP access, or the N5CW device is connected to a PLMN via 3GPP access but this PLMN is not in the list of available PLMNs):
i) If the N5CW device determines to be located in its home country, then:
- The N5CW device selects the HPLMN if the N5CW device has a USIM or is pre-configured with an HPLMN, if the HPLMN is included in the list of available PLMNs. Otherwise, the N5CW device selects an E-HPLMN (Equivalent HPLMN), if an E-HPLMN is included in the list of available PLMNs. If the list of available PLMNs does not include the HPLMN and does not include an E-HPLMN, the N5CW device stops the access network selection procedure.
ii) If the N5CW device determines to be located in its visited country, then:
- The N5CW device determines if it is mandatory to select a PLMN in the visited country, as follows:
- If the N5CW device has IP connectivity (e.g. it is connected via 3GPP access), the N5CW device sends a DNS query and receives a DNS response that indicates if a PLMN must be selected in the visited country. The DNS response includes a lifetime that denotes how long the DNS response can be cached.
- If the N5CW device has no IP connectivity (e.g. it is not connected via 3GPP access), then the N5CW device may use a cached DNS response that was received in the past, or may use local configuration that indicates which visited countries mandate a PLMN selection in the visited country.
- If the N5CW device determines that it is not mandatory to select a PLMN in the visited country and the HPLMN or an E-HPLMN is included in the list of available PLMNs, then the N5CW device selects the HPLMN or an E-HPLMN, whichever is included in the list of available PLMNs.
- Otherwise, the N5CW device selects a PLMN in the visited country as follows:
- If the N5CW device has a USIM, the UE selects a PLMN in the visited country by considering, in priority order, the PLMNs, first, in the User Controlled PLMN Selector list and, next, in the Operator Controlled PLMN Selector list (see TS 23.122 [17]).
- If the N5CW device does not have a USIM, the N5CW device selects the highest priority PLMN in a pre-configured list, which is also included in the list of available PLMNs.
- If the list of available PLMNs does not include a PLMN that is also included in the pre-configured list(s), the N5CW device either stops the access network selection procedure, or may select a PLMN based on its own implementation.
Step 3: Finally, the N5CW device selects a WLAN access network (e.g. an SSID) to connect to, following the procedure specified in clause 6.6.1.3 of TS 23.503 [45], "UE procedure for selecting a WLAN access based on WLANSP rules", or any other implementation specific means.
After the N5CW device completes the above access network selection procedure, the N5CW device initiates the "Initial Registration and PDU Session Establishment" procedure specified in clause 4.12b.2 of TS 23.502 [3].
6.3.12b Access Network selection for 5G NSWO
In addition to the PLMN lists specified in clause 6.3.12 and in clause 6.3.12a, a WLAN access network may also advertise the following PLMN list:
- A PLMN List-5, which includes candidate PLMNs with which "AAA connectivity to 5GC" is supported. A WLAN access network supports "AAA connectivity to 5GC" in a candidate PLMN when it deploys an AAA function that can connect with a NSWOF in this PLMN or can connect with a NSWOF in another PLMN (i.e. HPLMN in roaming case) via AAA proxy. The NSWOF supports "WLAN connection using 5G credentials without 5GS registration", as defined in clause 4.2.15.
If the UE selects a PLMN that is neither UE's HPLMN nor EHPLMN through which the NSWO request should be sent towards the HPLMN, the UE shall use the decorated NAI format as specified in clause 4.2.15 and in TS 23.003 [19].
For access to SNPN or CH , a WLAN access network may also advertise the following SNPN list:
- A SNPN List-5, which includes SNPNs with which "AAA connectivity to 5GC" is supported. The SNPNs are the candidate serving SNPNs that the WLAN access network can connect with. A WLAN access network supports "AAA connectivity to 5GC" in a SNPN when it deploys an AAA function that can connect with a NSWOF in this SNPN or can connect with a NSWOF or AAA server in a CH via AAA Proxy. The SNPN or CH supports "WLAN connection using 5G credentials without 5GS registration", as defined in clause 4.2.15.
NOTE: The selected SNPN within the SNPN List-5 is interpreted as serving SNPN when the SNPN does not correspond to UE's subscribed SNPN.
When the UE wants to connect to a WLAN access network using the 5G NSWO procedure defined in TS 33.501 [29], Annex S, the UE may retrieve the PLMN List-5 or SNPN List-5 advertised by each discovered WLAN access network and may consider this list for selecting the WLAN access network to connect to. For example, if the UE identifies that the HPLMN or CH is included in the PLMN List-5 or SNPN List-5 advertised by a WLAN access network, the UE may select this WLAN access network to connect to using the 5G NSWO procedure.
When the UE is configured by HPLMN or CH to use 5G NSWO for connecting to WLAN access networks using its 5G credentials (as defined in TS 33.501 [29]), the UE shall attempt to select a WLAN that supports 5G NSWO and shall only use the 5G NSWO procedure for connecting to the selected WLAN.
A WLAN access network may also advertise a list of SNPNs which includes SNPNs with which "AAA connectivity to 5GC" is supported. A WLAN access network supports "AAA connectivity to 5GC" in an SNPN when it deploys an AAA function that can connect with a SNPN or CH using any of the architectures defined in clause 4.2.15. When the UE operating in SNPN access mode wants to connect to a WLAN access network using the 5G NSWO procedure defined in Annex S of TS 33.501 [29], the UE may retrieve the SNPNs with which "AAA connectivity to 5GC" is supported that are advertised by each discovered WLAN access network and may consider this information for selecting the WLAN access network to which it attempts to connect. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.3.13 NWDAF discovery and selection | Multiple instances of NWDAF may be deployed in a network.
The NF consumers shall utilize the NRF to discover NWDAF instance(s) unless NWDAF information is available by other means, e.g. locally configured on NF consumers. NF consumers may make an additional query to UDM, when supported, as detailed below. The NWDAF selection function in NF consumers selects an NWDAF instance based on the available NWDAF instances.
The NRF may return one or more candidate NWDAF instance(s) and each candidate NWDAF instance (based on its registered profile) supports the Analytics ID with a time that is less than or equal to the Supported Analytics Delay.
The following factors may be considered by the NF consumer for NWDAF selection:
- S-NSSAI.
- Analytics ID(s).
- Supported service(s), possibly with their associated Analytics IDs.
- NWDAF Serving Area information, i.e. list of TAIs, for which the NWDAF can provide services and collect data; for each item of this list, a weight may be defined in the NWDAF NF profile to indicate the priority of the NWDAF to cover the TA. If there exists AoI, then the NWDAF whose serving area covers the AoI may be selected.
NOTE 1: If all services provided by one NWDAF do not support the same Analytics ID, the NWDAF registers the Analytics IDs of the services at the service level.
NOTE 2: Analytics ID(s) at service level take precedence over Analytics ID(s) at NF level.
NOTE 3: For discovery of NWDAF supporting Nnwdaf_AnalyticsSubscription or Nnwdaf_AnalyticsInfo services, the Analytics IDs at the NWDAF NF profile are used.
- (only when DCCF is hosted by NWDAF):
- NF type of the data source.
- NF Set ID of the data source.
NOTE 4: Can be used when the NWDAF determines that it needs to discover another NWDAF which is responsible for co-ordinating the collection of required data. The NWDAF does a new discovery for a target NWDAF via NRF using NF Set ID or NF type of the data source, or using Area of Interest.
NOTE 5: For discovery of NWDAF supporting Nnwdaf_DataManagement service, at least the NWDAF Serving Area information from the NWDAF profile are used.
NOTE 6: The presence of NF type of data source or NF set ID of the data source denotes that the NWDAF can collect data from such NF Sets or NF Types.
- Supported Analytics Delay of the requested Analytics ID(s) (see clause 6.2.6.2).
- Vendor ID(s) of potential target AnLF(s), e.g. used in transfer procedure.
In the case of multiple instances of NWDAFs deployment, following factors may also be considered:
- NWDAF Capabilities:
- Analytics aggregation capability.
- Analytics metadata provisioning capability.
- Accuracy checking capability (i.e. analytics accuracy checking capability for the AnLF and/or ML Model accuracy checking capability for the MTLF as defined in clause 5C.1 of TS 23.288 [86]).
Applicable when NF consumer cannot determine a suitable NWDAF instance based on NRF discovery response and when NWDAF registration in UDM is supported, as defined in clause 5.2 of TS 23.288 [86]: NF consumers may query UDM (Nudm_UECM_Get service operation) for determining the ID of the NWDAF serving the UE. The following factors may be considered by NF consumers to select an NWDAF instance already serving a UE for an Analytics ID:
- SUPI.
- Analytics ID(s).
When selecting an NWDAF for ML model provisioning, the following additional factors may be considered by the NWDAF:
- LMF-based AI/ML positioning indication (indicating that the NWDAF containing MTLF supports ML model training for LMF-based AI/ML positioning).
- The ML model Filter information parameters S-NSSAI(s) and Area(s) of Interest (see clause 5.2, TS 23.288 [86]) for the trained ML model(s) per Analytics ID(s) and ML Model Interoperability indicator per Analytics ID, if available.
When selecting an NWDAF that supports Horizontal Federated Learning (HFL), the following additional factors may be considered by the NWDAF:
- Time Period of Interest: time interval [start…end], during which the Federated Learning will be performed.
- when selecting HFL client NWDAF:
- FL capability type as HFL client NWDAF per Analytics ID.
- NF type(s) of the data source(s) where data can be collected as input for local model training.
- NF Set ID(s) of the data source(s) where data can be collected as input for local model training.
- ML Model Interoperability indicator.
- when selecting HFL server NWDAF:
- FL capability type as HFL server NWDAF per Analytics ID.
- The ML model Filter information parameters S-NSSAI(s) and Area(s) of Interest (see clause 5.2 of TS 23.288 [86]) for the trained ML model(s) per Analytics ID(s), if available.
When selecting an NWDAF that supports Vertical Federated Learning (VFL), the following additional factors may be considered by the NWDAF:
- Time Period of Interest: time interval [start…end], during which the Vertical Federated Learning will be performed.
- When selecting VFL client NWDAF:
- VFL capability type as VFL client NWDAF per Analytics ID.
- VFL Interoperability Indicator per Analytics ID.
- Optionally, supported Feature IDs per Analytics ID.
- Optionally NF set ID(s) of the data source(s).
- Optionally the Serving Area information.
- When selecting VFL server NWDAF:
- VFL capability type as VFL server NWDAF per Analytics ID.
Editor's note: Whether to register and discover VFL server is FFS.
When selecting a NWDAF for roaming case, the detailed mechanism is defined in clause 5.2 of TS 23.288 [86]. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.3.14 NEF Discovery | The NF consumers may utilize the NRF to discover NEF instance(s) unless NEF information is available by other means, e.g. locally configured in NF consumers. The NRF provides NF profile(s) of NEF instance(s) to the NF consumers.
The IP address(es)/port(s) of the NEF or L-NEF may be locally configured in the AF, or the AF may discover the FQDN or IP address(es)/port(s) of the NEF/L-NEF by performing a DNS query using the External Identifier of an individual UE or using the External Group Identifier of a group of UEs or using EDNS Client Subnet, or, if the AF is trusted by the operator, the AF may utilize the NRF to discover the FQDN or IP address(es)/port(s) of the NEF or L-NEF.
NOTE 1: When the AF discovers the FQDN or IP address(es)/port(s) of the NEF/L-NEF by performing a DNS query, the AF can add in its DNS request an EDNS Client Subnet option in order to help the DNS determine a local NEF directly. The use of a DNS query for the selection of a L-NEF is only supported for AF and not internal network functions.
NOTE 2: The EDNS Client Subnet may be derived by the AF based on factors that are considered for NEF selection. Whether and which factors are considered for NEF/L-NEF selection may depend on whether the AF performs an initial NEF discovery or a NEF discovery due to L-PSA relocation.
NOTE 3: The NEF discovery and selection procedures described in this clause are intended to be applied by NF consumers deployed within the operator's domain.
NOTE 4: The NEF supporting the capabilities can be configured in the AF or discovered by AF with the assistance of NRF.
The following factors may be considered for NEF selection:
- S-NSSAI(s);
- S-NSSAI and DNN corresponding to an untrusted AF;
- Event ID(s) supported by an AF (see clause 6.2.6, clause 6.2.2.3 of TS 23.288 [86] and clause 5.2.19 of TS 23.502 [3]);
- AF Instance ID, Application Identifier;
- External Identifier, External Group Identifier, or domain name;
- A request for local NEF selection;
- Location (see locality in clause 6.1.6.2.2 of TS 29.510 [58]);
- (for local NEF selection) List of supported TAI;
- (for local NEF selection) List of supported DNAI;
- Capability of NEF to support UAS NF functionality for UUAA procedures;
- Capability of NEF to support Multi-member AF session with required QoS for a set of UEs identified by a list of UE addresses;
- Capability of NEF to support member UE selection assistance functionality.
Local NEF instance(s) can be deployed close to UE access. For local NEF selection, the location of the local NEF instance (e.g. geographical location, data centre) may be used in conjunction with the location of L-PSA UPF or AF. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.3.15 UCMF Discovery and Selection | The AMF, MME, NEF, AF, SCEF, SCS/AS may utilize the NRF to discover UCMF instance(s) unless UCMF information is available by other means, e.g. locally configured in UCMF services consumers.
In the case of delegated discovery and selection in SCP, the NF consumer shall forward the request towards SCP. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.3.16 SCP discovery and selection | An NF is configured with its serving SCP(s).
In a deployment where several SCPs are deployed, a message may traverse several SCP instances until reaching its final destination. A SCP may discover and select a next hop SCP by querying the Nnrf_NFDiscovery Service of the NRF or it may be configured with next SCP in the message path.
An SCP may use the SCP profile parameters in clause 6.2.6.3 as discovery parameters in Nnrf_NFDiscovery. The parameter(s) to be used depend(s) on network deployment. The NRF returns a list SCP Profiles as per the provided discovery parameters.
An SCP may consider analytics such as signalling storm analytics from the NWDAF to discover or/and select the next hop SCP.
If an SCP receives a Routing Binding Indication within a service or notification request and decides to forward that request to a next-hop SCP, it shall include the Routing Binding Indication in the forwarded request.
NOTE: It is up to SCP implementation, deployment specific configuration and operator policies as to how the SCP will use information retrieved from the NRF to resolve the optimal route to a producer.
Based on SCP configuration, an SCP deciding to address a next-hop SCP for a service request may then delegate the NF (instance) and/or service (instance) selection to subsequent SCPs and provide discovery and selection parameters to the next-hop SCP.
For the discovery of an SCP acting as NF service producer for the services listed in clause 7.2.30, the procedures in clause 6.3.1 apply. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.3.17 NSSAAF discovery and selection | In the case of NF consumer based discovery and selection, the following applies:
- The NF consumer (e.g. AMF, AUSF) performs NSSAAF selection to select an NSSAAF Instance that supports authentication between the UE and the AAA-S associated with the HPLMN or in the Credentials Holder in the case of SNPN or in the DCS domain in the case of ON-SNPN. The NF consumer shall utilize the NRF to discover the NSSAAF instance(s) unless NSSAAF information is available by other means, e.g. locally configured on the NF consumer. The NSSAAF selection function in the NF consumer selects an NSSAAF instance based on the available NSSAAF instances (obtained from the NRF or locally configured in the NF consumer).
NSSAAF selection is applicable to both 3GPP access and non-3GPP access.
The NSSAAF selection function in NSSAAF NF consumers or in SCP should consider the following factor when it is available:
1. Home Network Identifier (e.g. MNC and MCC, realm) of SUPI (by an NF consumer in the Serving network).
2. S-NSSAI of the HPLMN.
3. SUPI or Internal Group ID; the NSSAAF NF consumer selects a NSSAAF instance based on the SUPI range the UE's SUPI belongs to or based on the results of a discovery procedure with NRF using the UE's SUPI or Internal Group ID as input for NSSAAF discovery.
An HPLMN deploying NSSAAF instances supporting specific S-NSSAIs and/or sets of SUPIs (according to factors 2-3) shall also deploy NSSAAF instance(s) that can be selected using factor 1 if they need to interoperate with VPLMNs using only factor 1 for NSSAAF selection.
In the case of delegated discovery and selection in SCP, the NSSAAF NF consumer shall send all available factors to the SCP. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.3.18 5G-EIR discovery and selection | A consumer NF of the 5G-EIR performs discovery of 5G-EIR using either configuration or NRF as specified in clause 6.3.1. The network is configured with the 5G-EIR to serve the PLMN of the NF consumer requesting the 5G-EIR service, i.e. no roaming interface is defined.
The 5G-EIR selection function in NF consumers is independent of Access Type. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.3.19 DCCF discovery and selection | Multiple instances of DCCF may be deployed in a network.
The NF consumers shall utilize the NRF to discover DCCF instance(s) unless DCCF information is available by other means, e.g. locally configured on NF consumers. The DCCF selection function in NF consumers selects a DCCF instance based on the available DCCF instances.
The following factors may be considered by the NF consumer for DCCF selection:
- DCCF Serving Area information, i.e. list of TAIs for which the DCCF coordinates Data Sources.
- S-NSSAI.
- NF type of the data source.
- NF Set ID of the data source.
NOTE: NF Set ID can be used when the NF consumer is a DCCF when the DCCF determines that it needs to discover another DCCF which is responsible for co-ordinating the collection of required data. The DCCF discovers a target DCCF via NRF using NF Set ID of the data source.
- DCCF relocation capability: Support for relocating the data collection subscription among DCCFs. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.3.20 ADRF discovery and selection | Multiple instances of ADRF may be deployed in a network.
The NF consumers shall utilize the NRF to discover ADRF instance(s) unless ADRF information is available by other means, e.g. locally configured on NF consumers. The ADRF selection function in NF consumers selects an ADRF instance based on the available ADRF instances.
NOTE: When NF consumer is DCCF, the DCCF can have information available already from previous registrations of ADRFs. In this case, NRF discovery is not needed.
The following factors may be considered by the NF consumer for ADRF selection:
- S-NSSAI.
- ML model storage capability. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.3.21 MFAF discovery and selection | Multiple instances of MFAF may be deployed in a network.
The MFAF selection function is supported by the DCCF. The DCCF shall utilize the NRF to discover MFAF instance(s) unless MFAF information is available by other means, e.g. locally configured on the DCCF. The MFAF selection function in the DCCF selects a MFAF instance based on the available MFAF instances.
The following factors may be considered by the DCCF for MFAF selection:
- S-NSSAI;
- NF Types of the Data Sources handled by the MFAF;
- NF Set IDs of the Data Sources handled by the MFAF;
- MFAF Serving Area information, i.e. list of TAIs for which the MFAF may receive data and/or analytics from Data Sources. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.3.22 NSACF discovery and selection | The NF consumers shall utilise the NRF to discover NSACF instance(s), including the NSACF acting as Primary NSACF role, unless NSACF information is available by other means, e.g. locally configured in NF consumers.
The NSACF selection function in the NSACF NF consumer selects an NSACF instance based on the available NSACF instances, which are obtained from the NRF or locally configured in the NSACF NF consumer.
The following factors may be considered by the NF consumer for NSACF discovery and selection:
- S-NSSAI(s).
- NSAC Service Area Identifier, or a reserved value "Entire PLMN" for discovering the NSACF acting as Primary NSACF or centralized NSAC role. The NSAC Service Area Identifier is configured at the consumer NF and NSACF (see clause 5.15.11.0). Each Service Area Identifier is a unique and unambiguous identifier and a NSACF registers with the NRF the NSAC Service Area Identifier(s) of the NSAC Service Area(s) it serves. "Entire PLMN" is indicated in roaming case to the NRF of HPLMN by the VPLMN NF consumer when the VPLMN NF consumer needs to discover the HPLMN NSACF, or in non roaming case to select a Primary NSACF.
- NSACF service capabilities:
- Support monitoring and controlling the number of registered UEs per network slice for the network slice that is subject to NSAC.
- Support, for network slices that are subject to NSAC and configured to support EPS counting, monitoring and controlling the number of registered UEs with at least one PDU session per network slice, as defined in clause 5.15.11.5a.
- Support monitoring and controlling the number of established PDU Sessions per network slice for the network slice that is subject to NSAC.
- PLMN ID information in the case of roaming to contact the HPLMN NSACF for inbound roamers.
In the case of delegated discovery and selection in SCP, the NSACF NF consumer shall send all available and applicable factors to the SCP. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.3.23 EASDF discovery and selection | Multiple instances of EASDF may be deployed in a network. NF consumers mentioned in this clause are SMF(s) or I-SMF in the case that I-SMF based Local Offloading Management applies..
In the case that I-SMF based Local Offloading Management applies, EASDF discovery and selection is only performed by the selected I-SMF.
The NF consumers shall utilize the NRF to discover EASDF instance(s) unless EASDF information is available by other means, e.g. locally configured on the NF consumer. The EASDF selection function in NF consumers or SCP selects an EASDF instance based on the available EASDF instances.
The following factors may be considered by the NF consumer or SCP for EASDF selection:
- S-NSSAI.
- DNN.
- the N6 IP address of the EASDF.
NOTE: The IP address of the EASDF is not used for EASDF discovery. It can be used is to select an EASDF that is "IP near" to the PSA of the PDU Session.
- The N6 IP address of the PSA UPF.
- Location as per NF profile.
- DNAI (if exist).
- Supported DNS security protocols (if existing). |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.3.24 TSCTSF Discovery | The NFs (e.g. NEF, AF and PCF) may utilize the NRF to discover TSCTSF instance(s) unless TSCTSF information is available by other means, e.g. locally configured in the requested NF.
The following factors may be considered for TSCTSF discovery and selection:
- DNN and S-NSSAI. When the NF discovers the TSCTSF for a DNN/S-NSSAI, the NRF provides the NF with NF profile(s) of TSCTSF instance(s) belonging to single TSCTSF Set for a given DNN/S-NSSAI. For example, the same TSCTSF Set shall be selected by the PCF serving PDU Sessions for this DNN and S-NSSAI to notify the TSCTSF for a PDU Session that is potentially impacted by the (g)PTP time synchronization service.
- GPSI or External Group Identifier. TSCTSF NF consumers (which manage network signalling not based on SUPI/SUCI (e.g. the NEF)) select a TSCTSF instance based on the GPSI or External Group ID range the UE's GPSI or External Group ID belongs to or based on the results of a discovery procedure with NRF using the UE's GPSI or External Group ID as input for TSCTSF discovery.
- SUPI or Internal Group ID. TSCTSF NF consumers select a TSCTSF instance based on the SUPI range the UE's SUPI belongs to or based on the results of a discovery procedure with NRF using the UE's SUPI or Internal Group ID as input for TSCTSF discovery.
If the TSCTSF is locally configured in NFs, it shall be ensured that the same TSCTSF Set is configured in all NFs (e.g. NEF, AF and PCF) for the given DNN and S-NSSAI.
NOTE: Thus, it is assumed that there is only one TSCTSF Set for a given DNN/S-NSSAI in this Release of the specification. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.3.25 AF Discovery and Selection | The NF consumers (e.g. NWDAF) may utilize the NRF to discover AF instance(s) in the MNO domain, i.e. trusted AF(s), unless AF information is available by other means, e.g. locally configured in NF consumers. The NRF provides NF profile(s) of AF instance(s) to the NF consumers.
The following factors may be considered for AF discovery and selection:
- One or multiple combination(s) of the S-NSSAI and DNN corresponding to an AF.
- Supported Application Id(s).
- Event ID(s) Supported by an AF.
- Internal-Group Identifier.
The NF consumer (e.g. NWDAF) may select an AF instance, in the MNO domain, considering one or multiple combination(s) of the S-NSSAI and DNN corresponding to an AF and the EventID(s) supported by an AF to provide the input data required for generation of analytics. The NF consumer (e.g. NWDAF) may consider the supported Application Id(s), if the input data is required only for those applications. The NF consumer (e.g. NWDAF) may consider the Internal-Group Identifier supported by the AF if the input data is required for a particular group of UEs. In the case of Vertical Federated Learning (VFL), the NF consumer (e.g. NWDAF) may also consider other factors that are described in clause 5.5 of TS 23.288 [86]. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.3.26 NRF discovery and selection | The following mechanisms may be used for discovery of NRF service instances and their endpoint addresses:
- NF consumers or SCP may have all the NRF services instances and their endpoint addresses locally configured.
- NF consumers or SCP may have the endpoint address of a NRF discovery service locally configured and utilize it to discover the NRF(s) and get the NF profile(s) of the NRF(s).
- NF consumers (e.g. v-NRF) or SCP may have endpoint addresses of the NRF bootstrapping service and utilize it to discover the NRF service instances and their endpoint addresses. The NRF bootstrapping service is a version independent API, which may be especially useful over roaming interfaces.
- The NF consumer, e.g. AMF, may use the Nnssf_NSSelection service to get the endpoint address of a NRF discovery service for a certain slice. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.3.27 EIF discovery and selection | The NF consumers may utilise the NRF services to discover EIF instance(s) or the EIF selection information may be locally configured in NF consumers.
The following factors may be considered by the NF consumer for EIF selection:
- Location (see locality in clause 6.1.6.2.2 of TS 29.510 [58]). |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 6.3.28 NSSF discovery and selection | The following mechanisms may be used for discovery of NSSF service instances and their endpoint addresses in the serving network:
- NF consumer (i.e. AMF) or SCP may have all the NSSF services instances and their endpoint addresses locally configured.
- NF consumer (i.e. AMF) or SCP may utilise the NRF discovery service to discover the NSSF(s) and get the NF profile(s) of the NSSF(s). In this case, NSSF discovery and selection uses a PLMN-level NRF (i.e. not a slice-specific).
NOTE: Location information as defined in clause 6.3.1.2 can be used by the NF consumer for selecting an NSSF.
For an NSSF in visited network to discover and select an NSSF in home network, NSSF services instances and their endpoint addresses of the home NSSF is either locally configured in the visited NSSF or are discovered based on the self-constructed FQDN as specified in TS 23.003 [19]. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 7 Network Function Services and descriptions | |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 7.1 Network Function Service Framework | |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 7.1.1 General | Service Framework functionalities include e.g. service registration/de-registration, consumer authorization, service discovery and inter service communication, which include selection and message passing. Four communication options are listed in Annex E and can all co-exist within one and the same network.
An NF service is one type of capability exposed by an NF (NF Service Producer) to other authorized NF (NF Service Consumer) through a service-based interface. A Network Function may expose one or more NF services. Following are criteria for specifying NF services:
- NF services are derived from the system procedures that describe end-to-end functionality, where applicable (see TS 23.502 [3], Annex B drafting rules). Services may also be defined based on information flows from other 3GPP specifications.
- System procedures can be described by a sequence of NF service invocations.
NF services may communicate directly between NF Service consumers and NF Service Producers, or indirectly via an SCP. Direct and Indirect Communication are illustrated in Figure 7.1.1-1. For more information, see Annex E and clauses 6.3.1 and 7.1.2. Whether a NF Service Consumer (e.g. in the case of requests or subscriptions) or NF Service Producer (e.g. in the case of notifications) uses Direct Communication or Indirect Communication by using an SCP is based on the local configuration of the NF Service Consumer/NF Service Producer. An NF may not use SCP for all its communication based on the local configuration.
NOTE: The SCP can be deployed in a distributed manner.
In Direct Communication, the NF Service consumer performs discovery of the target NF Service producer by local configuration or via NRF. The NF Service consumer communicates with the target NF Service producer directly.
In Indirect Communication, the NF Service consumer communicates with the target NF Service producer via a SCP. The NF Service consumer may be configured to perform discovery of the target NF Service producer directly, or delegate the discovery of the target NF Service Producer to the SCP used for Indirect Communication. In the latter case, the SCP uses the parameters provided by NF Service consumer to perform discovery and/or selection of the target NF Service producer. The SCP address may be locally configured in NF Service consumer.
Figure 7.1.1-1: NF/NF service inter communication |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 7.1.2 NF Service Consumer - NF Service Producer interactions | The end-to-end interaction between two Network Functions (Consumer and Producer) within this NF service framework follows two mechanisms, irrespective of whether Direct Communication or Indirect Communication is used:
- "Request-response": A NF_B (NF Service Producer) is requested by another NF_A (NF Service Consumer) to provide a certain NF service, which either performs an action or provides information or both. NF_B provides an NF service based on the request by NF_A. In order to fulfil the request, NF_B may in turn consume NF services from other NFs. In Request-response mechanism, communication is one to one between two NFs (consumer and producer) and a one-time response from the producer to a request from the consumer is expected within a certain timeframe. The NF Service Producer may also add a Binding Indication (see clause 6.3.1.0) in the Response, which may be used by the NF Service Consumer to select suitable NF service producer instance(s) for subsequent requests. For indirect communication, the NF Service Consumer copies the Binding Indication into the Routing Binding indication, that is included in subsequent requests, to be used by the SCP to discover a suitable NF service producer instance(s).
Figure 7.1.2-1: "Request-response" NF Service illustration
- "Subscribe-Notify": A NF_A (NF Service Consumer) subscribes to NF Service offered by another NF_B (NF Service Producer). Multiple NFs may subscribe to the same NF Service. NF_B notifies the results of this NF service to the interested NF(s) that subscribed to this NF service. The subscription request shall include the notification endpoint, i.e. a Notification Target Address and a Notification Correlation ID (e.g. the callback URL) of the NF Service Consumer to which the event notification from the NF Service Producer should be sent to.
NOTE 1: The notification endpoint can be a URL and contains both the Notification Target Address and the Notification Correlation ID.
The NF Service Consumer may add a Binding Indication (see clause 6.3.1.0) in the subscribe request, which may be used by the NF Service Producer to discover a suitable notification endpoint. For indirect communication, the NF Service Producer copies the Binding Indication into the Routing Binding Indication, that is included in the response, to be used by the SCP to discover a suitable notification target. The NF Service Producer may also add a Binding Indication (see clause 6.3.1.0) in the subscribe response, which may be used by the NF Service Consumer (or SCP) to select suitable NF service producer instance(s) or NF producer service instance. In addition, the subscription request may include notification request for periodic updates or notification triggered through certain events (e.g. the information requested gets changed, reaches certain threshold etc.). The subscription for notification can be done through one of the following ways:
- Explicit subscription: A separate request/response exchange between the NF Service Consumer and the NF Service Producer; or
- Implicit subscription: The subscription for notification is included as part of another NF service operation of the same NF Service; or
- Default notification endpoint: Registration of a notification endpoint for each type of notification the NF consumer is interested to receive, as a NF service parameter with the NRF during the NF and NF service Registration procedure as specified in clause 4.17.1 of TS 23.502 [3].
The NF Service Consumer may also add a Binding Indication (see clause 6.3.1.0) in the response to the notification request, which may be used by the NF Service Producer to discover a suitable notification endpoint. For indirect communication, the NF Service Producer copies the Binding Indication into the Routing Binding indication that is included in subsequent notification requests. The binding indication is then used by the SCP to discover a suitable notification target.
Figure 7.1.2-2: "Subscribe-Notify" NF Service illustration 1
A NF_A may also subscribe to NF Service offered by NF_B on behalf of NF_C, i.e. it requests the NF Service Producer to send the event notification to another consumer(s). In this case, NF_A includes the notification endpoint, i.e. Notification Target Address) and a Notification Correlation ID, of the NF_C in the subscription request. NF_A may also additionally include the notification endpoint and a Notification Correlation ID of NF A associated with subscription change related Event ID(s), e.g. Subscription Correlation ID Change, in the subscription request, so that NF_A can receive the notification of the subscription change related event. The NF_A may add Binding Indication (see clause 6.3.1.0) in the subscribe request.
Figure 7.1.2-3: "Subscribe-Notify" NF Service illustration 2
Routing of the messages for the NF interaction mechanisms above may be direct, as shown in the figures 7.1.2-1 to 7.1.2-3, or indirect. In the case of Indirect Communication, an SCP is employed by the NF service consumer. The SCP routes messages between NF service consumers and NF service producers based on the Routing Binding Indication if available and may do discovery and associated selection of the NF service producer on behalf of a NF service consumer. Figure 7.1.2-4 shows the principle for a request-response interaction and figure 7.1.2-5 shows an example of a subscribe-notify interaction.
Figure 7.1.2-4: Request response using Indirect Communication
Figure 7.1.2-5: Subscribe-Notify using Indirect Communication
NOTE: The subscribe request and notify request can be routed by different SCPs. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 7.1.3 Network Function Service discovery | A Network function (NF) within the 5G Core network may expose its capabilities as services via its service based interface, which can be re-used by CN NFs.
The NF service discovery enables a CN NF or SCP to discover NF instance(s) that provide the expected NF service(s). The NF service discovery is implemented via the NF discovery functionality.
For more detail NF discovery refer to clause 6.3.1. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 7.1.4 Network Function Service Authorization | NF service authorization shall ensure the NF Service Consumer is authorized to access the NF service provided by the NF Service Provider, according to e.g. the policy of NF, the policy from the serving operator, the inter-operator agreement.
Service authorization information shall be configured as one of the components in NF profile of the NF Service Producer. It shall include the NF type (s) and NF realms/origins allowed to consume NF Service(s) of NF Service Producer.
Due to roaming agreements and operator policies, a NF Service Consumer shall be authorised based on UE/subscriber/roaming information and NF type, the Service authorization may entail two steps:
- Check whether the NF Service Consumer is permitted to discover the requested NF Service Producer instance during the NF service discovery procedure. This is performed on a per NF granularity by NRF.
NOTE 1: When NF discovery is performed based on local configuration, it is assumed that locally configured NFs are authorized.
- Check whether the NF Service Consumer is permitted to access the requested NF Service Producer for consuming the NF service, with a request type granularity. This is performed on a per UE, subscription or roaming agreements granularity. This type of NF Service authorization shall be embedded in the related NF service logic.
NOTE 2: The security of the connection between NF Service Consumer and NF Service Producer is specified in TS 33.501 [29].
NOTE 3: It is expected that an NF authorization framework exists in order to perform consumer NF authorization considering UE, subscription or roaming agreements granularity. This authorization is assumed to be performed without configuration of the NRF regarding UE, subscription or roaming information. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 7.1.5 Network Function and Network Function Service registration and de-registration | For the NRF to properly maintain the information of available NF instances and their supported services, each NF instance informs the NRF of the list of NF services that it supports.
NOTE: The NF informs the appropriate NRF based on configuration.
The NF instance may make this information available to NRF when the NF instance becomes operative for the first time (registration operation) or upon individual NF service instance activation/de-activation within the NF instance (update operation) e.g. triggered after a scaling operation. The NF instance while registering the list of NF services it supports, for each NF service, may provide a notification endpoint information for each type of notification service that the NF service is prepared to consume, to the NRF during the NF instance registration. The NF instance may also update or delete the NF service related parameters (e.g. to delete the notification endpoint information). Alternatively, another authorised entity (such as an OA&M function) may inform the NRF on behalf of an NF instance triggered by an NF service instance lifecycle event (register or de-registration operation depending on instance instantiation, termination, activation, or de-activation). Registration with the NRF includes capacity and configuration information at time of instantiation.
The NF instance may also de-registers from the NRF when it is about to gracefully shut down or disconnect from the network in a controlled way. If an NF instance become unavailable or unreachable due to unplanned errors (e.g. NF crashes or there are network issues), an authorised entity shall de-register the NF instance with the NRF. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 7.2 Network Function Services | |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 7.2.1 General | In the context of this specification, an NF service is offering a capability to authorised consumers.
Network Functions may offer different capabilities and thus, different NF services to distinct consumers. Each of the NF services offered by a Network Function shall be self-contained, reusable and use management schemes independently of other NF services offered by the same Network Function (e.g. for scaling, healing, etc).
The discovery of the NF instance and NF service instance is specified in clause 6.3.1.
NOTE 1: There can be dependencies between NF services within the same Network Function due to sharing some common resources, e.g. context data. This does not preclude that NF services offered by a single Network Function are managed independently of each other.
Figure 7.2.1-1: Network Function and NF Service
Each NF service shall be accessible by means of an interface. An interface may consist of one or several operations.
Figure 7.2.1-2: Network Function, NF Service and NF Service Operation
System procedures, as specified in TS 23.502 [3] can be built by invocation of a number of NF services. The following figure shows an illustrative example on how a procedure can be built; it is not expected that system procedures depict the details of the NF Services within each Network Function.
Figure 7.2.1-3: System Procedures and NF Services
NOTE 2: The SCP can be used for indirect communication between NF/NF service instances. For simplicity the SCP is not shown in the procedure.
The following clauses provide for each NF the NF services it exposes through its service based interfaces. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 7.2.2 AMF Services | The following NF services are specified for AMF:
Table 7.2.2-1: NF Services provided by AMF
Service Name
Description
Reference in TS 23.502 [3] or indicated other TS
Namf_Communication
Enables an NF consumer to communicate with the UE and/or the AN through the AMF.
This service enables SMF to request EBI allocation to support interworking with EPS. This service also supports PWS functionality as described in TS 23.041 [46].
5.2.2.2
Namf_EventExposure
Enables other NF consumers to subscribe or get notified of the mobility related events and statistics.
5.2.2.3
Namf_MT
Enables an NF consumer to make sure UE is reachable.
5.2.2.4
Namf_Location
Enables an NF consumer to request location information for a target UE.
5.2.2.5
Namf_MBSBroadcast
Enables the NF consumer to communicate with the NG-RAN for broadcast communication.
TS 23.247 [129]
Namf_MBSCommunication
Enables NF consumer to communicate with the NG-RAN for multicast communication.
TS 23.247 [129] |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 7.2.3 SMF Services | The following NF services are specified for SMF:
Table 7.2.3-1: NF Services provided by SMF
Service Name
Description
Reference in TS 23.502 [3]
Nsmf_PDUSession
This service manages the PDU Sessions and uses the policy and charging rules received from the PCF. The service operations exposed by this NF service allows the consumer NFs to handle the PDU Sessions.
5.2.8.2
Nsmf_EventExposure
This service exposes the events happening on the PDU Sessions to the consumer NFs.
5.2.8.3
Nsmf_NIDD
This service is used for NIDD transfer between SMF and another NF.
5.2.8.4
Nsmf_TrafficCorrelation
Used for SMF determined information related to the members of the set of UEs identified by traffic correlation ID as defined in clause 6.2.3.2.7 of TS 23.548 [130],
5.2.8.5 |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 7.2.4 PCF Services | The following NF services are specified for PCF:
Table 7.2.4-1: NF Services provided by PCF
Service Name
Description
Reference in TS 23.502 [3] or indicated other TS
Npcf_AMPolicyControl
This PCF service provides Access Control, network selection and Mobility Management related policies, UE Route Selection Policies to the NF consumers.
5.2.5.2
Npcf_SMPolicyControl
This PCF service provides session related policies to the NF consumers.
5.2.5.4
Npcf_PolicyAuthorization
This PCF service authorises an AF request and creates policies as requested by the authorised AF for the PDU Session to which the AF session is bound to. This service allows the NF consumer to subscribe/unsubscribe to the notification of Access Type and RAT type, PLMN identifier, access network information, usage report etc.
5.2.5.3
Npcf_BDTPolicyControl
This PCF service provides background data transfer policy negotiation and optionally notification for the renegotiation to the NF consumers.
5.2.5.5
Npcf_UEPolicyControl
This PCF service provides the management of UE Policy Association to the NF consumers.
5.2.5.6
Npcf_EventExposure
This PCF service provide the support for event exposure.
5.2.5.7
Npcf_AMPolicyAuthorization
The PCF authorises an AF request and uses it as input for deciding access and mobility management related policies for a UE.
5.2.5.8
Npcf_MBSPolicyControl
The PCF service provides MBS session related policies towards the MB-SMF.
TS 23.247 [129]
Npcf_MBSPolicyAuthorization
This service authorizes an AF / NEF / MBSF request for an MBS service and t creates policies as requested by the authorized AF for the MBS Service.
TS 23.247 [129]
Npcf_PDTQPolicyControl
This PCF service provides negotiation for Planned Data Transfer with QoS requirements policy and optionally notification for the renegotiation to the NF consumers.
5.2.5.9 |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 7.2.5 UDM Services | The following NF services are specified for UDM:
Table 7.2.5-1: NF Services provided by UDM
Service Name
Description
Reference in TS 23.502 [3] or indicated other TS
Nudm_UECM
1. Provide the NF consumer of the information related to UE's transaction information, e.g. UE's serving NF identifier, UE status, etc.
2. Allow the NF consumer to register and deregister its information for the serving UE in the UDM.
3. Allow the NF consumer to update some UE context information in the UDM.
5.2.3.2
Nudm_SDM
1. Allow NF consumer to retrieve user subscription data when necessary.
2. Provide updated user subscriber data to the subscribed NF consumer.
5.2.3.3
Nudm_UEAuthentication
1. Provide updated authentication related subscriber data to the subscribed NF consumer.
2. For AKA based authentication, this operation can be also used to recover from security context synchronization failure situations.
3. Used for being informed about the result of an authentication procedure with a UE.
5.2.3.4
Nudm_EventExposure
1. Allow NF consumer to subscribe to receive an event.
2. Provide monitoring indication of the event to the subscribed NF consumer.
5.2.3.5
Nudm_ParameterProvision
1. To provision information which can be used for the UE in 5GS.
5.2.3.6
Nudm_NIDDAuthorisation
1. To authorise an NIDD configuration request for the received External Group Identifier or GPSI.
5.2.3.7
Nudm_ ServiceSpecificAuthorisation
1. To authorise for a specific service configuration.
5.2.3.8
Nudm_ReportSMDeliveryStatus
1. To report the SM-Delivery Status to UDM.
5.2.3.9
Nudm_MT
1. UE state and domain selection info for terminating services.
TS 23.632 [102]
Nudm_UEIdentifier
1. De-conceal the SUCI of a (Remote) UE to its SUPI
Clause 7.4.3 of TS 33.503 [194] |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 7.2.6 NRF Services | The following NF services are specified for NRF:
Table 7.2.6-1: NF Services provided by NRF
Service Name
Description
Reference in TS 23.502 [3]
Nnrf_NFManagement
Provides support for register, deregister and update service to NF, NF services, SCP. Provide NF service consumers and SCP with notifications of newly registered/updated/deregistered NF along with its NF services. Also Provide SCP with notifications of newly registered/updated/deregistered SCP.
5.2.7.2
Nnrf_NFDiscovery
Enables one NF service consumer or SCP to discover a set of NF instances with specific NF service or a target NF type. Also enables one NF service consumer or SCP to discover a specific NF service. Also enables a SCP to discover a next hop SCP.
5.2.7.3
Nnrf_AccessToken
Provides OAuth2 2.0 Access Tokens for NF to NF authorization as defined in TS 33.501 [29].
5.2.7.4
Nnrf_Bootstrapping
Lets NF Service Consumers of the NRF know about the services endpoints it supports, the NRF Instance ID and NRF Set ID if the NRF is part of an NRF set.
5.2.7.5 |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 7.2.7 AUSF Services | The following NF services are specified for AUSF:
Table 7.2.7-1: NF Services provided by AUSF
Service Name
Description
Reference in TS 23.502 [3]
Nausf_UEauthentication
The AUSF provides UE authentication service to requester NF. For AKA based authentication, this operation can also be used to recover from security context synchronization failure situations.
5.2.10.2
Nausf_SoRProtection
The AUSF provides protection of Steering of Roaming information service to the requester NF.
5.2.10.3
Nausf_UPUProtection
The AUSF provides the UE Parameters Update protection service to the requester NF.
5.2.10.4 |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 7.2.8 NEF Services | The following NF services are specified for NEF:
Table 7.2.8-1: NF Services provided by NEF
Service Name
Description
Reference in TS 23.502 [3] or other TS
Nnef_EventExposure
Provides support for event exposure.
5.2.6.2
Nnef_PFDManagement
Provides support for PFDs management.
5.2.6.3
Nnef_ParameterProvision
Provides support to provision information which can be used for the UE in 5GS.
5.2.6.4
Nnef_Trigger
Provides support for device triggering.
5.2.6.5
Nnef_BDTPNegotiation
Provides support for background data transfer policy negotiation and optionally notification for the renegotiation.
5.2.6.6
Nnef_TrafficInfluence
Provide the ability to influence traffic routing.
5.2.6.7
Nnef_ChargeableParty
Requests to become the chargeable party for a data session for a UE.
5.2.6.8
Nnef_AFsessionWithQoS
Requests the network to provide a specific QoS for an AF session.
5.2.6.9
Nnef_MSISDN-less_MO_SMS
Used by the NEF to send MSISDN-less MO SM to the AF.
5.2.6.10
Nnef_ServiceParameter
Provides support to provision service specific information.
5.2.6.11
Nnef_APISupportCapability
Provides support for awareness on availability or expected level of a service API.
5.2.6.12
Nnef_NIDDConfiguration
Used for configuring necessary information for data delivery via the NIDD API.
5.2.6.13
Nnef_NIDD
Used for NEF anchored MO and MT unstructured data transport.
5.2.6.14
Nnef_SMContext
Provides the capability to create, update or release the SMF-NEF Connection.
5.2.6.15
Nnef_AnalyticsExposure
Provides support for exposure of network analytics.
5.2.6.16
Nnef_UCMFProvisioning
Provides the ability to configure the UCMF with dictionary entries consisting of UE manufacturer-assigned UE Radio Capability IDs, the corresponding UE radio capabilities, the corresponding UE Radio Capability for Paging and the (list of) associated IMEI/TAC value(s) via the NEF. The UE radio capabilities the NEF provides for a UE radio Capability ID can be in TS 36.331 [51] format, TS 38.331 [28] format or both formats. Also used for deletion (e.g. as no longer used) or update (e.g. to add or remove a (list of) IMEI/TAC value(s) associated to an entry) of dictionary entries in the UCMF.
5.2.6.17
Nnef_ECRestriction
Provides support for queuing status of enhanced coverage restriction, or enable/disable enhanced coverage restriction per individual UEs.
5.2.6.18
Nnef_ApplyPolicy
Provides the capability to apply a previously negotiated Background Data Transfer Policy to a UE or a group of UEs.
5.2.6.19
Nnef_Location
Provides the capability to deliver UE location to AF.
5.2.6.21
Nnef_AMInfluence
Provides the ability to influence access and mobility management related policies for one or multiple UEs.
5.2.6.22
Nnef_AMPolicyAuthorization
Provides the ability to provide inputs that can be used by the PCF for deciding access and mobility management related policies.
5.2.6.23
Nnef_AKMA
AKMA Application Key derivation service.
TS 33.535 [124]
Nnef_Authentication
This service enables the consumer to authenticate and authorize the Service Level Device Identity as described in TS 23.256 [136].
TS 23.256 [136]
Nnef_TimeSynchronization
Provides the ability to support for (g)PTP or 5G access stratum based time synchronization service.
5.2.6.25
Nnef_EASDeployment
EAS deployment service.
5.2.6.26
Nnef_UEId
UE Identifier service, which supports the retrieval of an AF specific UE Identifier or GPSI in the form of MSISDN based on the UE address. It also supports MSISDN verification of given UE.
5.2.6.27
Nnef_MBSTMGI
Allows AF to request allocation/deallocation of TMGI(s) for MBS Session.
TS 23.247 [129]
Nnef_MBSSession
Allows AF to create, update and delete MBS Session.
TS 23.247 [129]
Nnef_MBSGroupMsgDelivery
Allows AF to request to create, update and delete resource for group message delivery via MBS Session.
TS 23.247 [129]
Nnef_ASTI
Provides the ability to influence 5G access stratum based time distribution configuration.
5.2.6.28
Nnef_SMService
Used for SBI-based MO SM transmit through NEF for MSISDN-less MO SMS.
5.2.6.29
Nnef_PDTQPolicyNegotiation
Provides support for negotiation for Planned Data Transfer with QoS requirements policy and optionally notification for the renegotiation.
5.2.6.30
Nnef_MemberUESelectionAssistance
Provides one or more list(s) of candidate UE(s) (among the list of target member UE(s) provided by the AF) and additional information based on the parameters contained in the request from the AF.
5.2.6.31
Nnef_DNAIMapping
Allows AF to obtain DNAI.
5.2.6.34
Nnef_TrafficInfluenceData
Used in HR SBO as defined in TS 23.548 [130] to get AF Traffic Influence configuration from the V-NEF.
5.2.6.35
Nnef_UEAddress
Enables the service consumer to retrieve the public IPv4address or IPv6 prefix related to a PDU session and GPSI
5.2.6.36
Nnef_ECSAddress
This service is defined only for the support of HR-SBO. It allows AF to provide ECS Address Configuration Information for a group of UE or any UE to V-NEF. It allows V-SMF to subscribe and retrieve ECS Address Configuration Information.
5.2.6.37
7.2.8A Void |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 7.2.9 SMSF Services | The following NF services are specified for SMSF:
Table 7.2.9-1: NF Services provided by SMSF
Service Name
Description
Reference in TS 23.502 [3]
Nsmsf_SMService
This service allows AMF to authorize SMS and activate SMS for the served user on SMSF.
Additionally, this service allows downlink SMS message transmit from consumer NF to SMSF.
5.2.9.2 |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 7.2.10 UDR Services | The following NF services are specified for UDR:
Table 7.2.10-1: NF Services provided by UDR
Service Name
Description
Reference in TS 23.502 [3]
Nudr_DM
Allows NF consumers to retrieve, create, update, subscribe for change notifications, unsubscribe for change notifications and delete data stored in the UDR, based on the set of data applicable to the consumer.
This service may also be used to manage operator specific data.
5.2.12.2
Nudr_GroupIDmap
Allows NF consumers to retrieve a NF group ID corresponding to a subscriber identifier.
5.2.12.3 |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 7.2.11 5G-EIR Services | The following NF services are specified for 5G-EIR:
Table 7.2.11-1: NF Services provided by 5G-EIR
Service Name
Description
Reference in TS 23.502 [3]
N5g-eir_Equipment Identity Check
This service enables the 5G-EIR to check the PEI and check whether the PEI is in the prohibited list or not.
5.2.4.2 |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 7.2.12 NWDAF Services | The following NF services are specified for NWDAF:
Table 7.2.12-1: NF Services provided by NWDAF
Service Name
Description
Reference in TS 23.288 [86]
Nnwdaf_AnalyticsSubscription
This service enables the NF service consumers to subscribe/unsubscribe for different type of analytics from NWDAF.
7.2
Nnwdaf_AnalyticsInfo
This service enables the NF service consumers to request and get different type of analytics information from NWDAF or enables NWDAF to request transfer of analytics context from another NWDAF.
7.3
Nnwdaf_DataManagement
This service enables the NF service consumer to subscribe/unsubscribe and fetch data from NWDAF.
7.4
Nnwdaf_MLModelProvision
This service enables the consumer to receive a notification when an ML model matching the subscription parameters becomes available in NWDAF containing MTLF.
7.5
Nnwdaf_MLModelInfo
This service enables the consumer to request and get ML Model Information from NWDAF containing MTLF.
7.6
Nnwdaf_MLModelMonitor
This service enables the consumer to subscribe/unsubscribe for ML model accuracy information monitored by an NWDAF (i.e. NWDAF containing AnLF). The service also enables the NWDAF containing AnLF registers the use and monitoring capability for an ML model into the model provider NWDAF, i.e. NWDAF containing MTLF.
7.9
Nnwdaf_MLModelTraining
This service enables ML model training.
7.10
Nnwdaf_MLModelTrainingInfo
This service enables the consumer to request for the information about ML model training based on the ML Model input parameter provided by the consumer.
7.11
Nnwdaf_RoamingAnalytics
This service enables the consumer to request or to subscribe/unsubscribe for network data analytics related to roaming UE for NWDAF analytics.
7.7
Nnwdaf_RoamingData
This service enables the consumer to subscribe/unsubscribe for input data related to roaming UE for NWDAF analytics.
7.8 |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 7.2.13 UDSF Services | The following NF services are specified for UDSF:
Table 7.2.13-1: NF Services provided by UDSF
Service Name
Description
Reference in TS 23.502 [3]
Nudsf_UnstructuredDataManagement
Allows NF consumers to retrieve, create, update and delete data stored in the UDSF.
5.2.14.2
Nudsf_Timer
Allows NF consumers to start, stop, update and search timers in UDSF. NF consumers may be notified about timer expiry.
5.2.14.3 |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 7.2.14 NSSF Services | The following NF services are specified for NSSF:
Table 7.2.14-1: NF Services provided by NSSF
Service Name
Description
Reference in TS 23.502 [3]
Nnssf_NSSelection
Provides the requested Network Slice information to the Requester.
5.2.16.2
Nnssf_NSSAIAvailability
Provides NF consumer on the availability of S-NSSAIs on a per TA basis.
5.2.16.3 |
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