Section: 4.3.6.3 Notification of User Plane Management Events
Content: The SMF may send a notification to the AF if the AF had subscribed to user plane management event notifications as described in clause 4.3.6.2 and in clause 5.6.7 of TS 23.501[ System architecture for the 5G System (5GS) ]  [2]. The following are the examples of such events: - A PDU Session Anchor identified in the AF subscription request has been established or released. - A DNAI has changed. - The SMF has received a request for AF notification and the on-going PDU Session meets the conditions to notify the AF. - Ethernet PDU Session Anchor Relocation as defined in clause 4.3.5.8. - Candidate DNAI(s) has changed. - A common EAS has changed. The SMF uses notification reporting information received from PCF to issue the notification either via an NEF (2a, 2b and 4a, 4b) or directly to the AF (2c and 4c). In the case of the AF interacting with VPLMN in the HR-SBO case, the NF(s) in the procedure are located in VPLMN. NOTE 1: 1a: In HR-SBO case, no PCF in VPLMN is involved. The following flow depicts the sequence of events: Figure 4.3.6.3-1: Notification of user plane management event 1. 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[ System architecture for the 5G System (5GS) ]  [2], SMF sends notification, as shown in steps 2a or 2c. 2a. 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[ 5G System Enhancements for Edge Computing; Stage 2 ]  [74]. 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. NOTE 2: For the reporting of candidate DNAIs from SMF/NEF to AF, only early notification is used. 2b. 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[ System architecture for the 5G System (5GS) ]  [2] and triggers the appropriate Nnef_TrafficInfluence_Notify message. In this case, step 2c is not applicable. 2c. 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. 2d. 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. NOTE 3: The maximum time the new PSA is to buffer UL data relates to the maximum delay between steps 4a-4c and step 4f/4g of Figure 4.3.6.3-1. SMF local policies can control this maximum time. NOTE 4: The traffic being buffered is the traffic associated with the PCC rule that has requested the notification. 2d-a. If information sent via Nnef_TrafficInfluence_Create is to be changed e.g. N6 traffic routing details corresponding to the target DNAI, the AF invokes Nnef_TrafficInfluence_update service operation in order for PCF to be able to include this information in PCC rules sent to SMF. If the AF includes information such as N6 traffic routing details corresponding to the target DNAI in Nnef_TrafficInfluence_AppRelocationInfo it shall include the same information in Nnef_TrafficInfluence_update. If common DNAI or common EAS is required for set of UEs and AF is used to select common DNAI or common EAS according to operator's configuration, the AF determines the common DNAI/EAS according to the candidate DNAI(s) of each UE of the set reported by SMF(s) serving the set of UEs, then informs SMF(s) of each UE of the selected common DNAI as clause 6.2.3.2.6 of TS 23.548[ 5G System Enhancements for Edge Computing; Stage 2 ]  [74] or the selected common EAS as clause 6.2.3.2.5 of TS 23.548[ 5G System Enhancements for Edge Computing; Stage 2 ]  [74]. 2e. When the NEF receives Nnef_TrafficInfluence_AppRelocationInfo, the NEF triggers the appropriate Nsmf_EventExposure_AppRelocationInfo message. 2e-a. When the NEF receives Nnef_TrafficInfluence_update, the NEF triggers step 3a as in Figure 4.3.6.2-1 or step 2 of Figure 4.3.6.4-1 if targeting an individual UE by a UE address. 2f. 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. 2f-a. If information sent via Npcf_PolicyAuthorization_Create is to be changed e.g. N6 traffic routing details corresponding to the target DNAI, the AF invokes Npcf_PolicyAuthorization_Update service operation in order for PCF to be able to include this information in PCC rules sent to SMF. If the AF includes information such as N6 traffic routing details corresponding to the target DNAI in Nsmf_EventExposure_AppRelocationInfo it shall include the same information in Npcf_PolicyAuthorization_Update. 3. 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[ System architecture for the 5G System (5GS) ]  [2]. 4a. 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 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[ System architecture for the 5G System (5GS) ]  [2]. 4b. 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[ System architecture for the 5G System (5GS) ]  [2] and triggers the appropriate Nnef_TrafficInfluence_Notify message. In this case, step 4c is not applicable. 4c. 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 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. 4d. 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. NOTE 5: If the source AF is already locally configured with information associated with the target DNAI, the source AF is assumed to use the locally configured information, even if it has received from the SMF target AF ID in a previous step above. NOTE 6: The determination of the target AF for the target DNAI and the AF migration to the target AF are out of the scope of this release. 4e. 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. 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[ 5G System Enhancements for Edge Computing; Stage 2 ]  [74], 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. NOTE 7: The action taken by the AF when receiving such an indication that an EAS re-discovery request has been sent to the UE is out of scope of 3GPP specifications. 4e-a. If information sent via Nnef_TrafficInfluence_Create/Update is to be changed e.g. N6 traffic routing details corresponding to the target DNAI, the AF invokes Nnef_TrafficInfluence_Create or Nnef_TrafficInfluence_Update service operation in order for PCF to be able to include this information in PCC rules sent to SMF. The Nnef_TrafficInfluence_Create shall be used if the AF is notified (e.g. in step 4b) that the UE IP address is changed and the initial Nnef_TrafficInfluence_Create was targeted to an individual UE address, otherwise the Nnef_TrafficInfluence_Update may be used. If the AF includes information such as N6 traffic routing details corresponding to the target DNAI in Nnef_TrafficInfluence_AppRelocationInfo it shall include the same information in Nnef_TrafficInfluence_Create or Nnef_TrafficInfluence_Update, whichever is appropriate. 4f. When the NEF receives Nnef_TrafficInfluence_AppRelocationInfo, the NEF triggers the appropriate Nsmf_EventExposure_AppRelocationInfo message. 4f-a. When the NEF receives Nnef_TrafficInfluence_Create/update, the NEF triggers step 3a as in Figure 4.3.6.2-1 or step 2 of Figure 4.3.6.4-1 if targeting an individual UE by a UE address. 4g. 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. 4g-a. If information sent via Npcf_PolicyAuthorization_Create/Update is to be changed e.g. N6 traffic routing details corresponding to the target DNAI, the AF invokes Npcf_PolicyAuthorization_Create or Npcf_PolicyAuthorization_Update service operation in order for PCF to be able to include this information in PCC rules sent to SMF. The Npcf_PolicyAuthorization_Create shall be used if the AF is notified (e.g. in step 4c) that the UE IP address is changed, otherwise the Npcf_PolicyAuthorization_Update may be used. If the AF includes information such as N6 traffic routing details corresponding to the target DNAI in Nsmf_EventExposure_AppRelocationInfo it shall include the same information in Npcf_PolicyAuthorization_Create or Npcf_PolicyAuthorization_Update, whichever is appropriate.