Section: 4.11.0a.2a.5 UE Policy Association establishment
Content: To support the delivery of URSP rule in EPS as described in clause 6.1.2.2.3 of TS 23.503[ Policy and charging control framework for the 5G System (5GS); Stage 2 ]  [20], the PCF for the PDU Session may establish a UE Policy Association towards the PCF for the UE. This procedure may be triggered by the following procedures: 1. UE requested bearer resource modification. 2. 5GS to EPS handover or 5GS to EPS Idle Mode mobility. Figure 4.11.0a.2a.5-1: UE Policy Association establishment procedure In the non-roaming case, the V-PCF for the UE is not involved, and the PCF for the PDU Session interacts with the PCF for the UE. For the Home Routed roaming scenario, the V-PCF for the UE is not involved and the H-PCF for the PDU Session interacts with the H-PCF for the UE. For the LBO roaming scenario, the V-PCF for the PDU Session interacts with the V-PCF for the UE and the V-PCF for the UE interacts with the H-PCF for the UE. The procedure is based on clause 4.16.11.1 for a UE in 5GC with the following differences: 1. The PCF for the PDU Session determines the need of establishment of a UE Policy Association when: - A UE Policy Container is received from the UE during SM Policy Association Update at UE requested bearer resource modification as described in clause 4.11.0a.2a.2.1; or - During 5GS to EPS mobility as described in clause 4.11.0a.2a.2.2. 2. Same as step 2 in clause 4.16.11, with the following exceptions: The PCF for the PDU Session includes the UE Policy Container in case of SM Policy Association update at UE requested bearer resource modification or 5GS to EPS Mobility indication in case of SM Policy Association update at 5GS to EPS mobility. For LBO roaming the V-PCF for the PDU Session discovers and selects an instance of the V-PCF for the UE based on the available PCF instances obtained from the NRF or locally configured information in the V-PCF, depending on operator's policies, as described in clause 6.3.7.1 of TS 23.501[ System architecture for the 5G System (5GS) ]  [2]. The V-PCF for the PDU Session contacts the V-PCF for the UE and steps 3 and 4 are executed. For non-roaming or Home Routed roaming the (H-)PCF for the PDU Session contacts the (H-)PCF for the UE and step5 follows. 3. Same as step 3 in clause 4.16.11.1, with the following exceptions: The UE Policy Container is received at SM Policy Association instead of initial registration. When the UE Policy Association is being established due to 5GS to EPS mobility as described in clause 4.11.0a.2a.2.2, the V-PCF for a UE in the VPLMN needs to discover and select the same H-PCF for a UE that is serving the UE in the H-PLMN for 5GS by querying the BSF in the HPLMN. This is to be able to recover the information about the list of PSIs in the UE and the subscribed PCRTs from former UE Policy Association for the UE in 5GS as described in step 6. Therefore, the V-PCF for a UE in the VPLMN needs first to discover the BSF in the HPLMN. NOTE 1: For Home Routed roaming, the V-PCF for a UE is not involved, therefore in this roaming scenario it is not possible to retrieve the Application guidance on URSP Rule for inbound roamers of the PLMN and provide it to the H-PCF for the UE to be used as input for the generation of the URSP rules for the UE as described in clause 6.6.2.2.3 of TS 23.503[ Policy and charging control framework for the 5G System (5GS); Stage 2 ]  [20]. 4. Same as in clause 4.16.11.1. 5. Same as in clause 4.16.11.1 step 5, with the following exceptions: The subscription to notification of N1 message delivery of policy information to the UE using Namf_Communication_N1N2MessageSubscribe service is not applicable. 6. The Same as step 6 in clause 4.16.11.1, with the following difference: If "5GS to EPS Mobility" indication was received in Npcf_UEPolicyControl_Create in step 2 instead, the (H-)PCF recovers the information about the list of PSIs for the UE, the subscribed PCRTs in 5GS from former UE Policy Association for the UE and the indication about the support of provisioning of URSP rules in EPS. If the UE does not support the provisioning of URSPs in EPS, the H-PCF rejects the establishment of the UE Policy Association. NOTE 2: In LBO roaming the V-PCF for a UE may trigger the establishment of the UE Policy Association for a UE that does not support the provisioning of URSP in EPS, as described in step 4a in clause 4.11.0a.2a.2.2. The (H-)PCF provides the UE Policy Container in the Npcf_UEPolicyControl_UpdateNotify Request. 7. Same as in clause 4.16.11. NOTE 3: Steps 8 and 9 are executed only in LBO roaming scenario. 8. The V-PCF for the UE forwards the UE Policy Container to the V-PCF for the PDU Session by invoking Npcf_UEPolicyControl UpdateNotify Request. The V-PCF for the UE checks the size limit as described in clause 6.1.2.2.2 of TS 23.503[ Policy and charging control framework for the 5G System (5GS); Stage 2 ]  [20]. 9. The V-PCF for the PDU Session sends a response to the V-PCF for the UE. 10. If the UE provides a UE Policy Container with the result of the URSP update to the PCF for the PDU Session as described in clause 4.11.0a.2a.2.3 the PCF for the PDU Session forwards the UE Policy Container to the (V-) PCF for the UE invoking Npcf_UEPolicyControl_Update Request. 11. The (V-) PCF for the UE sends a response to the (V-) PCF for the PDU Session. NOTE 4: Steps 12 and 13 are executed only in LBO roaming. 12. The V-PCF for the UE forwards the notification response to the H-PCF by invoking Npcf_UEPolicyControl_Update Request. 13. The H-PCF sends a response to the V-PCF for the UE.