Section: 4.16.5.1 SMF initiated SM Policy Association Modification
Content: The SMF may initiate the SM Policy Association Modification procedure if a Policy Control Request Trigger is met. NOTE 1: When SMF instance is changed within the same SMF set the callback URI can be updated via this procedure. Figure 4.16.5.1-1: SMF initiated SM Policy Association Modification For local breakout roaming, the interaction with HPLMN (e.g. step 2) is not used. In local breakout roaming, the V-PCF interacts with the UDR of the VPLMN. 1. When a Policy Control Request Trigger condition is met the SMF requests to update (Npcf_SMPolicyControl_Update) the SM Policy Association and provides information on the conditions that have been met as specified in clause 5.2.5.4.5. If the SMF is notified by NRF that the stored PCF instance is not reachable, it should query the NRF for PCF instances within the PCF set and select another instance (see clause 6.3.1.0 of TS 23.501[ System architecture for the 5G System (5GS) ]  [2]). The QoS constraints from the VPLMN are provided by the H-SMF to the H-PCF in the home routed roaming scenario as defined in clause 4.3.2.2.2. 2. When an AF has subscribed to an event that is met due to the report from the SMF, the PCF reports the event to the AF or TSCTSF by invoking the Npcf_PolicyAuthorization_Notify service operation. If the SMF has reported that new 5GS Bridge/Router information has been detected and no AF session exists for this PDU session yet: - If integration with TSN applies (see clause 5.28 of TS 23.501[ System architecture for the 5G System (5GS) ]  [2]), then the PCF informs a pre-configured TSN AF using the Npcf_PolicyAuthorization_Notify (User-plane Node ID, the port number of the DS-TT port, MAC address of the DS-TT Ethernet port for the PDU Session and UE-DS-TT Residence Time (if available)) service operation for the event of "5GS Bridge/Router information Notification" as described in clause 6.1.3.18 of TS 23.503[ Policy and charging control framework for the 5G System (5GS); Stage 2 ]  [20]. - Otherwise, i.e. if the integration with TSN does not apply, the PCF may inform discovered and selected TSCTSF (as described in clause 6.3.24 of TS 23.501[ System architecture for the 5G System (5GS) ]  [2]) using the Npcf_PolicyAuthorization_Notify (User Plane Node ID, UE-DS-TT Residence Time (if available), the port number for the PDU session and MAC address of the DS-TT Ethernet port for Ethernet type PDU Session or IP address for IP type PDU Session, MTU size for IPv4 or IPv6 (if available)) service operation for the event of "5GS Bridge/Router information Notification" as described in clause 6.1.3.18 of TS 23.503[ Policy and charging control framework for the 5G System (5GS); Stage 2 ]  [20]. In the case of private IPv4 address being used for IP type PDU Session, the Npcf_PolicyAuthorization_Notify also contains DNN and S-NSSAI of the PDU Session. NOTE 2: For a given DNN and S-NSSAI, it is assumed that the network only needs to deploy one or TSCTSF Set in this Release of the specification. When the TSN AF or TSCTSF receives the Npcf_PolicyAuthorization_Notify message and no AF session exists for this PDU Session, the TSN AF shall use the Npcf_PolicyAuthorization service described in clause 5.2.5.3 to request creation of a new AF session specific to the received MAC address of the DS-TT Ethernet port of the PDU Session, while the TSCTSF shall use the Npcf_PolicyAuthorization service to request creation of a new AF session specific to the received MAC address of the DS-TT Ethernet port (if available, for Ethernet type PDU Session) or IP address (for IP type PDU Session) of the PDU Session. In the case of private IPv4 address being used for IP type PDU Session, the TSCTSF shall use the Npcf_PolicyAuthorization service to request creation of a new AF session specific to the received IP address, DNN and S-NSSAI of the IP type PDU Session. The TSN AF or TSCTSF shall then use the Npcf_PolicyAuthorization service to subscribe for notifications for 5GS Bridge/Router information Notification event over the newly established AF session. The TSN AF or TSCTSF may provide a Port or User-Plane Management Information Container for the PDU Session and related port number in the Npcf_PolicyAuthorization creation request. If the SMF has reported PMIC with port number or UMIC, then the PCF also provides these information elements to the TSN AF or TSCTSF. When integration with TSN applies (see clause 5.28 of TS 23.501[ System architecture for the 5G System (5GS) ]  [2]), the TSN AF calculates the bridge delay for each port pair, using the UE-DS-TT Residence Time of the DS-TT Ethernet port(s) for the 5GS bridge indicated by the 5GS user-plane Node ID. 3. If the PCF determines a change to policy counter status reporting is required, it may alter the subscribed list of policy counters using the Initial, Intermediate or Final Spending Limit Report Retrieval procedures as defined in clause 4.16.8. 4. The PCF makes a policy decision as described in TS 23.503[ Policy and charging control framework for the 5G System (5GS); Stage 2 ]  [20]. The PCF may determine that updated or new policy information needs to be sent to the SMF. If the SMF reported accumulated usage for the PDU session in step 1 the PCF deducts the value from the remaining allowed usage for the subscriber, DNN and S-NSSAI in the UDR by invoking Nudr_DM_Update (SUPI, DNN, S-NSSAI, Policy Data, Remaining allowed Usage data, updated data) service operation. If the SMF reported accumulated usage for a MK(s) in step 1 the PCF deducts the value from the remaining allowed usage for the MK in the UDR by invoking Nudr_DM_Update (SUPI, DNN, S-NSSAI, Policy Data, Remaining allowed Usage data, updated data (including MK(s))) service operation. When new PCF instance is selected in step 1, the new PCF should invoke Nbsf_Management_Update service operation to update the binding information in BSF. In the non-roaming case, the PCF may subscribe to Analytics from NWDAF as defined in clause 6.1.1.3 of TS 23.503[ Policy and charging control framework for the 5G System (5GS); Stage 2 ]  [20]. In the home-routed roaming scenario, the H-PCF ensures that the QoS constraints provided by the VPLMN are taken into account as described in TS 23.503[ Policy and charging control framework for the 5G System (5GS); Stage 2 ]  [20]. NOTE 3: For local breakout roaming, PDU Session policy control subscription information and Remaining allowed usage subscription information for monitoring control as defined in clause 6.2.1.3 of TS 23.503[ Policy and charging control framework for the 5G System (5GS); Stage 2 ]  [20] are not available in V-UDR and V-PCF uses locally configured information according to the roaming agreement with the HPLMN operator. 5. The PCF answers with a Npcf_SMPolicyControl_Update response with updated policy information about the PDU Session determined in step 4.