Content for  TS 23.502  Word version:  18.5.0

The PCF(s) subscribe to modifications of AF requests (Data Set = Application Data; Data Subset = AF traffic influence request information, Data Key = S-NSSAI and/or DNN and/or Internal Group Identifier or SUPI) from the UDR.

To create a new request, the AF invokes a Nnef_TrafficInfluence_Create service operation. The content of this service operation (AF request) is defined in clause 5.2.6.7. The request contains also an AF Transaction Id. If it subscribes to events related with PDU Sessions the AF indicates also where it desires to receive the corresponding notifications (AF notification reporting information). To update or remove an existing request, the AF invokes a Nnef_TrafficInfluence_Update or Nnef_TrafficInfluence_Delete service operation providing the corresponding AF Transaction Id. The Nnef_TrafficInfluence_Create (initiated by target AF) or Nnef_TrafficInfluence_Update (initiated by source AF or target AF) service operation may be used for the case of AF instance change. If Nnef_TrafficInfluence_Update service operation is invoked, the NEF is required to update the subscription resource. The Nnef_TrafficInfluence_Update service operation may include an updated notification target address. The updated subscription resource is used by the target AF.

The AF sends its request to the NEF. If the request is sent directly from the AF to the PCF, the AF reaches the PCF selected for the existing PDU Session by configuration or by invoking Nbsf_management_Discovery service. The NEF ensures the necessary authorization control, including throttling of AF requests and as described in clause 4.3.6.1, mapping from the information provided by the AF into information needed by the 5GC.

(in the case of Nnef_TrafficInfluence_Create or Update): The NEF stores the AF request information in the UDR (Data Set = Application Data; Data Subset, Data Key = AF Transaction Internal ID, S-NSSAI and DNN and/or Internal Group Identifier(s) and/or Subscriber Category(s) or SUPI). The Data Subset identifies whether the information relates to AF traffic influence request information for traffic routing or AF traffic influence request information for service function chaining, as described in Table 5.2.12.2.1-1. (in the case of Nnef_TrafficInfluence_delete): The NEF deletes the AF requirements in the UDR (Data Set = Application Data; Data Subset, Data Key = AF Transaction Internal ID). The Data Subset identifies whether the information relates to AF traffic influence request information for traffic routing or AF traffic influence request information for service function chaining. The NEF responds to the AF.

The PCF(s) that have subscribed to modifications of AF requests receive(s) a Nudr_DM_Notify notification of data change from the UDR. The Data Subset identifies whether the information relates to AF traffic influence request information for traffic routing or AF traffic influence request information for service function chaining.

The PCF determines if existing PDU Sessions are potentially impacted by the AF request. For each of these PDU Sessions, the PCF updates the SMF with corresponding new policy information about the PDU Session by invoking Npcf_SMPolicyControl_UpdateNotify service operation as described in steps 5 and 6 in clause 4.16.5. The PCF validates whether the SFC identifier (if available) corresponds to an authorized SFC for the AF based on local configuration. If the validation has succeeded the PCF maps the SFC identifier to the corresponding Traffic Steering Policy identifier (i.e. TSP ID). The PCF includes the Traffic Steering Policy ID(s) in the AF influence on traffic routing Enforcement Control information and/or N6-LAN Traffic Steering Enforcement Control information of the relevant PCC rule as defined in clause 6.3.1 of TS 23.503. The PCF also includes the Metadata in the N6-LAN Traffic Steering Enforcement Control information of the PCC rule when Metadata was provided by the AF. If the AF request includes a notification reporting request for UP path change, the PCF includes in the PCC rule(s) the information required for reporting the event, including the Notification Target Address pointing to the NEF or AF and the Notification Correlation ID containing the AF Transaction Internal ID. If the AF request includes an EAS Correlation indication or indication of traffic correlation, PCF includes in the PCC rule(s) an EAS Correlation indication or indication of traffic correlation and a Traffic Correlation ID corresponding to a set of UEs that AF request aims at, also if AF request includes a common EAS IP address or common DNAI for a set of UEs, PCC rule includes the common EAS IP address or common DNAI. In the case of AF influence on traffic routing, the PCF may, optionally, use service experience analytics per UP path, as defined in clause 6.4.3 of TS 23.288, to provide an updated list of DNAI(s) to the SMF. The PCF may use the "Subscriber categories" as defined in "PDU Session policy control subscription information" in Table 6.2-2 of TS 23.503 to determine whether the PDU Session is impacted by the AF request.

When the updated policy information about the PDU Session is received from the PCF, the SMF may take appropriate actions to reconfigure the User plane of the PDU Session. In the case of AF influence on traffic routing, examples of actions are:

• The SMF may consider service experience analytics and/or DN Performance analytics per UP path (i.e. including UPF and/or DNAI and/or AS instance) as defined in clauses 6.4.3 and 6.14.3, respectively, of TS 23.288 before taking any actions.
• Determining a target DNAI.
• Determining if a common DNAI needs to be used as a target DNAI.
• Adding, replacing or removing a UPF in the data path to e.g. act as an UL CL or a Branching Point e.g. as described in clause 4.3.5.
• Allocate a new Prefix to the UE (when IPv6 multi-Homing applies).
• Updating the UPF in the target DNAI with AF influence on traffic routing control parameters as described in clause 5.6.7.1 of TS 23.501.
• Subscribe to notifications from the AMF for an Area of Interest via Namf_EventExposure_Subscribe service operation.
• Determining whether to relocate PSA UPF considering the user plane latency requirements provided by the AF (see clause 6.3.6 of TS 23.548).

When the updated policy information about the PDU Session is received from the PCF, the SMF may take appropriate actions to assist the EAS discovery and re-discovery for PDU Session with Session Breakout connectivity model such as:

• Retrieve the EAS deployment information as defined in clause 6.2.3.4.1 of TS 23.548.
• Providing DNS message handling rule to forward DNS messages of the UE and/or report when detecting DNS messages as defined in clause 6.2.3.2.2 of TS 23.548.

In the case of AF influence on Service Function Chaining, the SMF may take appropriate actions to enforce the N6-LAN traffic steering control:

• Provide N6-LAN traffic steering control parameters to UPF as described in clause 5.6.16 of TS 23.501.

The SMF may decide whether it is required to send the target DNAI to the AMF for triggering SMF/I-SMF (re)selection and then inform the target DNAI information for the current PDU session or for the next PDU session to AMF via Nsmf_PDUSession_SMContextStatusNotify service operation.

A condition for an AF notification has been met as described above. The SMF sends notification to the NF that is subscribed for SMF notifications. Further processing of the SMF notification depends on the receiving NF, as shown in steps 2a and 2c. If immediate reporting flag is included in AF subscription for user plane management event as described in clause 5.6.7 of TS 23.501, SMF sends notification, as shown in steps 2a or 2c.

If early notification via NEF is requested by the AF, the SMF notifies the NEF of the target DNAI or candidate DNAI(s) of the PDU Session or indication of EAS rediscovery and may indicate capability of supporting EAS IP replacement in 5GC by invoking Nsmf_EventExposure_Notify service operation. The SMF may provide the target AF ID if it determines that the target DNAI is not supported by the source AF as specified in TS 23.548. The SMF may consider the UE location and available DNAI list provided by AF to select the closest available DNAI(s) as candidate DNAI(s). The SMF may also provide the candidate DNAI(s) in a prioritized order.

When the NEF receives Nsmf_EventExposure_Notify, the NEF performs information mapping (e.g. AF Transaction Internal ID provided in Notification Correlation ID to AF Transaction ID, SUPI to GPSI, etc.) as applicable according to clause 5.6.7 of TS 23.501 and triggers the appropriate Nnef_TrafficInfluence_Notify message. In this case, step 2c is not applicable.

If early direct notification is requested by the AF, the SMF notifies the AF of the target DNAI or candidate DNAI(s) of the PDU Session or indication of EAS rediscovery and may indicate capability of supporting EAS IP replacement in 5GC by invoking Nsmf_EventExposure_Notify service operation. The SMF may provide the target AF ID if it determines that the target DNAI is not supported by the source AF.

The AF replies to Nnef_TrafficInfluence_Notify by invoking Nnef_TrafficInfluence_AppRelocationInfo service operation either immediately or after any required application relocation in the target DNAI is completed. The AF may include N6 traffic routing details corresponding to the target DNAI and /or the 'uplink buffering' indication to indicate that buffering of uplink traffic to the target DNAI is needed. The AF may include Information for EAS IP Replacement in 5GC. AF may reply in negative e.g. if the AF determines that the application relocation cannot be completed successfully and/or on time. Step 2d-a.

When the NEF receives Nnef_TrafficInfluence_AppRelocationInfo, the NEF triggers the appropriate Nsmf_EventExposure_AppRelocationInfo message. Step 2e-a.

The AF replies to Nsmf_EventExposure_Notify by invoking Nsmf_EventExposure_AppRelocationInfo service operation either immediately or after any required application relocation in the target DNAI is completed. The AF may include N6 traffic routing details corresponding to the target DNAI and /or the 'uplink buffering' indication to indicate that buffering of uplink traffic to the target DNAI is needed. The AF may include Information for EAS IP Replacement in 5GC. AF may reply in negative e.g. if the AF determines that the application relocation cannot be completed successfully on time. Step 2f-a.

The SMF enforces the change of DNAI or addition, change, or removal of a UPF. This may correspond to the mechanisms described in Figure 4.3.5.6-1 or in Figure 4.3.5.7-1. If the runtime coordination between 5GC and AF is enabled based on local configuration, according to the indication of "AF acknowledgment to be expected" included in AF subscription to SMF events, the SMF may wait for a response from the AF to the early notification before this step. The SMF does not perform this step until it receives a positive response from the AF, as described in clause 5.6.7 of TS 23.501.

If late notification via NEF is requested by the AF, the SMF notifies the NEF of the target DNAI of the PDU Session or indication of EAS rediscovery or new serving PLMN ID, HPLMN DNN and S-NSSAI of the PDU session if serving PLMN is changed and local traffic offload is allowed and may indicate capability of supporting EAS IP replacement in 5GC by invoking Nsmf_EventExposure_Notify service operation. The SMF may provide the target AF ID if it determines that the target DNAI is not supported by the source AF. If the runtime coordination between 5GC and AF is enabled based on local configuration, according to the indication of "AF acknowledgment to be expected" included in AF subscription to SMF events, the SMF may send late notification and wait for a positive response from the AF before activating the new UP path, as described in clause 5.6.7 of TS 23.501.

When the NEF receives Nsmf_EventExposure_Notify, the NEF performs information mapping (e.g. AF Transaction Internal ID provided in Notification Correlation ID to AF Transaction ID, SUPI to GPSI, etc.) as applicable according to clause 5.6.7 of TS 23.501 and triggers the appropriate Nnef_TrafficInfluence_Notify message. In this case, step 4c is not applicable.

If late direct notification is requested by the AF, the SMF notifies the AF of the target DNAI of the PDU Session or indication of EAS rediscovery or new serving PLMN ID, HPLMN DNN and S-NSSAI of the PDU session if serving PLMN is changed and local traffic offload is allowed and may indicate capability of supporting EAS IP replacement in 5GC by invoking Nsmf_EventExposure_Notify service operation. The SMF may provide the target AF ID if it determines that the target DNAI is not supported by the source AF.

When the AF receives either the Nnef_TrafficInfluence_Notify message or the Nsmf_EventExposure_Notify message, the AF checks whether it can serve the target DNAI. If the AF instance change is needed, the AF determines the proper target AF for the target DNAI (e.g. based on locally configured information or the AF ID provided by the SMF in step 4a or 4c) and performs the AF migration.

The AF replies to Nnef_TrafficInfluence_Notify by invoking Nnef_TrafficInfluence_AppRelocationInfo service operation either immediately or after any required application relocation in the target DNAI is completed. AF includes N6 traffic routing details corresponding to the target DNAI or new serving PLMN ID for traffic offload if serving PLMN is changed and local traffic offload is allowed. AF may reply in negative e.g. if the AF determines that the application relocation cannot be completed successfully on time. Nnef_TrafficInfluence_AppRelocationInfo with positive response may indicate that buffering of uplink traffic to the target DNAI is no more needed. If SMF has sent an EAS re-discovery request to the UE as defined in TS 23.548, e.g. due to change of common EAS, the SMF sends an indication to the AF that an EAS re-discovery request has been sent to the UE. Step 4e-a.

When the NEF receives Nnef_TrafficInfluence_AppRelocationInfo, the NEF triggers the appropriate Nsmf_EventExposure_AppRelocationInfo message. Step 4f-a.

The AF replies to Nsmf_EventExposure_Notify by invoking Nsmf_EventExposure_AppRelocationInfo service operation either immediately or after any required application relocation in the target DNAI is completed. AF includes N6 traffic routing details corresponding to the target DNAI. AF may reply in negative e.g. if the AF determines that the application relocation cannot be completed successfully on time. Nsmf_EventExposure_AppRelocationInfo with positive response may indicate that buffering of uplink traffic to the target DNAI is no more needed. Step 4g-a.

[Conditional] If the AF sends the AF request via NEF, the AF sends Nnef_TrafficInfluenceCreate/Update/Delete Request targeting an individual UE address to the NEF. This request corresponds to an AF request to influence traffic routing to a local network and/or to a service function chain that targets an individual UE address. When NEF receives an AF request from AF, the NEF ensures the necessary authorization control and as described in clause 4.3.6.1, mapping from the information provided by the AF into information needed by the 5GC. The NEF responds to the AF.

[Conditional] AF/NEF consumes Nbsf_Management_Discovery service operation (providing at least the UE address) to find out the address of the relevant PCF if the PCF address is not available on the NEF based on local configuration, otherwise step 1 is skipped.

BSF provides the PCF address in the Nbsf_Management_Discovery response to AF/NEF.

If step 1 was performed, NEF invokes the Npcf_PolicyAuthorization service to the PCF to transfer the AF request. If an AF sends the AF request directly to the PCF, AF invokes Npcf_PolicyAuthorization service and the PCF responds to the AF. To support the AF instance change, the Npcf_PolicyAuthorization_Create (initiated by target AF) or Npcf_PolicyAuthorization_Update (initiated by source AF or target AF) service operation may be used.

The PCF authorizes the AF request. If the PCF determines that the requirements can't be authorized, it rejects the AF request. Once the PCF authorizes the AF request, the PCF updates the SMF with corresponding new PCC rule(s) with PCF initiated SM Policy Association Modification procedure as described in clause 4.16.5.2. The PCF includes the Traffic Steering Policy ID(s) for AF influence on traffic routing Enforcement Control information and/or N6-LAN Traffic Steering Enforcement Control information in the relevant PCC rule as defined in clause 6.3.1 of TS 23.503. The PCF may, optionally, use service experience analytics per UP path, as defined in clause 6.4.3 of TS 23.288, to provide a an updated list of DNAI(s) to the SMF. If Npcf_PolicyAuthorization_Update service operation is invoked, the PCF is required to update the subscription resource. The Npcf_PolicyAuthorization_Update service operation may include an updated notification target address. The updated subscription resource is used by the target AF. When a PCC rule is received from the PCF, the SMF may take appropriate actions, when applicable, to reconfigure the User plane of the PDU Session. In the case of AF influence on traffic routing, examples of actions are:

• The SMF may consider service experience analytics and/or DN Performance analytics per UP path (i.e. including UPF and/or DNAI and/or AS instance) as defined in clauses 6.4.3 and 6.14.3, respectively, of TS 23.288 before taking any actions.
• Determining a target DNAI and adding, replacing or removing UPF(s) in the data path, e.g. to act as UL CL, Branching Point and/or PDU Session Anchor e.g. as described in clause 4.3.5.
• Allocate a new Prefix to the UE (when IPv6 multi-Homing applies).
• Updating the UPF regarding the target DNAI with AF influence on traffic routing control parameters as described in clause 5.6.7.1 of TS 23.501.
• Subscribe to notifications from the AMF for an Area of Interest via Namf_EventExposure_Subscribe service operation.
• Determining whether to relocate PSA UPF considering the user plane latency requirements provided by the AF (see clause 6.3.6 of TS 23.548).

In the case of AF influence on Service Function Chaining, the SMF may take appropriate actions to enforce the N6-LAN traffic steering control:

• Provide N6-LAN traffic steering control parameters to UPF as described in clause 5.6.16 of TS 23.501.