Section: 4.3.6.2 Processing AF requests to influence traffic routing and/or Service Function Chaining for Sessions not identified by an UE address
Content: Figure 4.3.6.2-1: Processing AF requests to influence traffic routing and/or Service Function Chaining for Sessions not identified by an UE address NOTE 1: The 5GC functions used in this scenario are assumed to all belong to the same PLMN (HPLMN in non-roaming case or VPLMN in the case of a PDU Session in LBO mode). 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. 1. 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. NOTE 2: If the source AF transfers the application context to the target AF, then target AF may create new subscription via Nnef_TrafficInfluence_Create operation or update existing subscription via Nnef_TrafficInfluence_Update. However, whether and how the application context transfer is done is out of this specification. 2. 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. 3. (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. NOTE 3: Both the AF Transaction Internal ID and S-NSSAI and DNN and/or Internal Group Identifier(s) and/or Subscriber Category(s) or SUPI are regarded as Data Key when the AF request information are stored into the UDR, see Table 5.2.12.2.1-1. The Subscriber Category(s) is determined by NEF as described in clause 4.3.6.1. (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. 4. 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. 5. 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[ Policy and charging control framework for the 5G System (5GS); Stage 2 ]  [20]. 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[ Architecture enhancements for 5G System (5GS) to support network data analytics services ]  [50], 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[ Policy and charging control framework for the 5G System (5GS); Stage 2 ]  [20] to determine whether the PDU Session is impacted by the AF request. 6. 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[ Architecture enhancements for 5G System (5GS) to support network data analytics services ]  [50] 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[ System architecture for the 5G System (5GS) ]  [2]. - 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[ 5G System Enhancements for Edge Computing; Stage 2 ]  [74]). 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[ 5G System Enhancements for Edge Computing; Stage 2 ]  [74]. - 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[ 5G System Enhancements for Edge Computing; Stage 2 ]  [74]. 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[ System architecture for the 5G System (5GS) ]  [2]. 7. 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.