Section: 4.15.6.9.3 Processing AF requests to influence access and mobility management policies
Content: With this procedure, the AF can provide its request to influence access and mobility management policies (for one or multiple UEs) at any time. Figure 4.15.6.9.3-1: Handling an AF request to influence access and mobility management policies Policy This procedure concerns non-roaming scenarios, i.e. to cases where the involved entities serving the UE (i.e. AF, NEF, PCF, BSF, UDR, AMF) belong to the home PLMN, or the AF belongs to a third party with which the home PLMN has an agreement. This procedure concerns also the local breakout roaming case where the involved entities (i.e. AF, NEF, PCF, BSF, UDR, AMF) serving the UE belong to the VPLMN or the AF belongs to a third party with which the VPLMN has an agreement. The PCF for the UE and the PCF for the PDU Session can be the same entity, then step 5 is not performed and the PCF itself determines the start/stop of application traffic or SM policy establishment/termination for a DNN, S-NSSAI and proceeds with step 6. 1. AM Policy Association establishment as described in clause 4.16.1. 2. The PCF for the UE may subscribe to policy data related to AM influence (Data Set = Application Data; Data Subset = AM influence information, Data Key = S-NSSAI and DNN and/or (Internal Group Identifier or SUPI or PLMN ID of inbound roamers)). 3a. To create a new request, the AF provides "AM influence information" data to the NEF using the Nnef_AMInfluence_Create service operation (together with the AF identifier and potentially further inputs as specified in clause 5.2.6.23.2), including a target (one UE identified by GPSI, a group of UEs identified by an External Group Identifier, or any UE (for non roaming case), or any inbound roaming UEs identified by their PLMN ID(s)), a list of (DNN, S-NSSAI)(s) and optionally a list of External Application Identifier(s) and requirements related to access and mobility management policies (e.g. service coverage requirements, throughput requirements). The AF request contains also an AF Transaction Id and may contain a timer on how long this policy shall last, in which case the system behaviour upon expiration of this timer is as specified in TS 23.503[ Policy and charging control framework for the 5G System (5GS); Stage 2 ]  [20]. If with this request the AF subscribes to access and mobility management related events, the AF indicates also where it desires to receive the corresponding notifications. The target "any UE" is applicable if an External Application Identifier or list of (DNN, S-NSSAI) is also provided. The target "any inbound roaming UEs identified by their PLMN ID(s)" is applicable if an External Application Identifier or list of (DNN, S-NSSAI) is also provided. To update or remove an existing request, the AF invokes an Nnef_AMInfluence_Update or Nnef_AMInfluence_Delete service operation providing the corresponding AF Transaction Id. 3b. The NEF stores, updates, or removes the policy data of step 3a in the UDR, having translated any External Group Identifier to an Internal Group Identifier and any GPSI to a SUPI. 3c. The UDR informs the NEF about the result of the operation of step 3b. 3d. The NEF informs the AF about the result of the Nnef_AMInfluence operation performed in step 3a. NOTE 1: Steps 1, 2 and 3 can occur in any order. 4. The UDR notifies the PCF(s) that have a matching subscription (from step 2) about the data stored, updated, or removed in step 3. If matching entries already existed in the UDR when step 2 is performed, this shall be immediately reported to the PCF. The PCF may check that an SM Policy Association is established for the SUPI, DNN, S-NSSAI then subscribe to the SMF to Policy Control Request Trigger to detect the application traffic that triggers the allocation of a service area coverage or an allocation of RFSP index value, then step 6 follows. 5. Steps 2 to 10 in Figure 4.16.14.2.1-1 applies if access and mobility management policies depend on application in use, or steps 2 to 5 in Figure 4.16.14.2.2-1 applies if access and mobility management policies depend on SM Policy Association establishment and termination for a DNN, S-NSSAI combination 6. The PCF for the UE takes a policy decision and then it may initiate an AM Policy Association Modification procedure as described in clause 4.16.2.2. If the AF has subscribed to access and mobility management related events, i.e. request for service area coverage outcome in step 3, then the PCF reports the event (i.e. outcome of the request for service area coverage) to the AF as described in clause 4.16.2.2. NOTE 2: The PCF for the UE can subscribe to the "start/stop of application traffic detection" events for multiple applications with different application identifiers in the same Npcf_PolicyAuthorization_Subscribe request. When PCF receives the notifications for multiple applications, the PCF for the UE can determine which access and mobility management policy to apply based on local configuration and operator policy.