5.17.8 URSP Provisioning in EPS

When the UE registers in 5GS, the UE includes the Indication of URSP Provisioning Support in EPS in the UE Policy Container carried in Registration Request. On receiving this indication in the UE Policy Container, the PCF will enable the provisioning of the URSP to UE in EPS.

The UE may include the indication of URSP Provisioning Support in EPS in PCO or ePCO to the SMF+PGW-C during:

• Initial Attach with default PDN connection establishment (according to clause 5.3.2.1 of TS 23.401 [26]).
• Any UE requested PDN connectivity request to an additional PDN (according to clause 5.10.2 of TS 23.401 [26].
• Any UE requested bearer resource modification procedure (according to clause 5.4.5 of TS 23.401 [26]).

If the SMF+PGW-C receives the indication of URSP Rule provisioning in EPS from the UE, and it supports URSP provisioning in EPS, it provides the Indication of URSP Provisioning Support in EPS in ePCO in the Create Session Response message to the UE. Then the UE and the SMF+PGW-C considers that the PDN connection is associated with the URSP provisioning in EPS.

The UE may also include the indication of URSP Provisioning Support in EPS in ePCO in the UE Requested PDU Session Establishment procedure (according to clause 4.3.2.2 of TS 23.502 [3] and clause 6.4.1.2 of TS 24.501 [47]). If the SMF+PGW-C receives the indication of URSP Rule provisioning in EPS from the UE and the network supports URSP provisioning in EPS, it provides the Indication of URSP Provisioning Support in EPS in ePCO in the PDU Session Establishment Accept message to the UE, see clause 6.4.1.3 of TS 24.501 [47].

Then the UE and the SMF+PGW-C considers that the PDU Session is associated with the URSP provisioning in EPS. The SMF+PGW-C provides the Indication of URSP Provisioning Support in EPS to the PCF during the SM Policy Association Establishment procedure.

When the UE receives an indication of URSP provisioning support in EPS in the PDN Connectivity Accept message or in PDU Session Establishment Accept and this PDN connection or the corresponding transferred PDN connection is not released, then for any subsequent PDN connectivity requests the UE does not include an indication of URSP Provisioning Support in EPS.

When the UE receives the Indication of URSP Provisioning Support in EPS included in ePCO in the PDN Connectivity Accept message, then the UE initiates the UE requested bearer resource modification with or without QoS update procedure and includes the UE Policy Container ePCO in the Request Bearer Resource Modification message, the UE Policy Container in ePCO will be further forwarded by MME to SMF+PGW-C. When the UE Policy Container ePCO is received by SMF+PGW-C, it forwards transparently the UE Policy Container to PCF for the PDU Session, then the PCF for the PDU Session establishes the UE Policy Association with PCF for the UE. The PCF for the UE generates the corresponding URSP rules in a similar way as it is done in 5GS and sends the URSP rules to UE in the UE Policy Container as described in clause 4.11.0a.5 of TS 23.502 [3]. If the PDN connection which is used for the exchange of UE Policy Container for URSP provisioning is released, the PCF for the PDU Session terminates the SM Policy Association, which then triggers the release of the UE Policy Association with PCF for the UE, see clause 4.11.0a.2a.8 of TS 23.502 [3]. The UE may use the Request Bearer Resource Modification message, over another PDN connection to include the Indication of URSP Provisioning Support in EPS. If the UE receives Indication of URSP Provisioning Support in EPS included in ePCO, then the UE sends a UE requested bearer resource modification with or without QoS update procedure and includes the UE Policy Container ePCO in the Request Bearer Resource Modification message. This triggers the establishment of the UE Policy Association; the UE may receive URSP rules in this PDN connection.

NOTE 1: The UE includes the Indication of URSP Provisioning Support in EPS in PCO or ePCO in the PDN connectivity request according to clause 6.6.1.1 of TS 24.301 [13].

NOTE 2: The MME and Serving-GW can be configured to prioritize the selection of a SMF+PGW-C that support URSP Rule provisioning in EPS.

NOTE 3: When URSP provisioning in EPS is required, the network deployment ensures that the MME supports ePCO.

If the UE does not receive the Indication of URSP Provisioning Support in EPS in ePCO in the PDN Connectivity Accept message, then the UE does not initiate the UE requested bearer resource modification procedure to send the UE Policy Container. The UE may include an indication of URSP Provisioning Support in EPS in a subsequent PDN connectivity request.

The PDN Connection used by UE and SMF+PGW-C to convey UE Policy Container PCO shall be kept when the UE is in the CONNECTED mode. When the UE is attached to EPS, the PCF for the PDU Session retrieves the PCRTs for UE Policy from PCF for the UE and subscribes to the applicable PCRTs to SMF+PGW-C. The PCF for the PDU Session may send the UE Policy Container in the same PDN connection in which the UE Policy Container was received or in any additional PDN connection established with a SMF+PGW-C supporting URSP delivery in EPS.

During EPS to 5GS mobility with N26, the UE Policy Association is terminated by PCF for PDU Session towards the PCF for the UE when it receives the indication of RAT type change from the SMF+PGW-C. The PCF for the PDU Session maintains Indication of URSP Provisioning Support in EPS while the SM Policy Association is established.

During 5GS to EPS mobility with N26, the PCF for the PDU Session determines whether the UE supports URSP delivery in EPS by checking Indication of URSP Provisioning Support in EPS that is locally stored. If the UE and at least one of the SMF+PGW-C for which the UE maintains a PDU session support URSP delivery in EPS the PCF for the PDU session establishes a UE Policy Association with the PCF for the UE. The PCF for the PDU Session discovers the address of PCF for the UE serving the UE by querying BSF. The PCF for the UE recovers the information about the PSI list in the UE and the subscribed PCRTs in 5GS from former UE Policy Association for the UE after receiving the UE Policy Association Establishment request including a UE Policy Container only including an indication about the trigger for the UE Policy Association Establishment ("5GS to EPS mobility").

After the 5GS to EPS mobility, if PCF for the UE needs to provision the URSP to UE, the PCF for the UE sends the UE Policy Container in Npcf_UEPolicyControl_UpdateNotify Request to the PCF for the PDU Session as described in clause 4.11.0a.2a.10 of TS 23.502 [3]. In case there are more than one PDN connections for the UE, then the PCF for the PDU Session selects any of the ongoing PDN Connections via a SMF+PGW-C supporting URSP delivery in EPS for the UE. Then via the selected PDN Connection, the SMF+PGW-C sends the UE Policy Container via ePCO to UE by initiating the PDN GW initiated bearer modification without QoS update procedure as defined in clause 5.4.3 of TS 23.401 [26].

When the UE moves from 5GS to EPS, the PDN connection corresponding to a PDU Session supporting URSP provisioning in EPS is considered as supporting URSP provisioning in EPS. When the UE moves from EPC to 5GS, the PDU Session corresponding to a PDN connection supporting URSP provisioning in EPS is considered as supporting URSP provisioning in EPS.

NOTE 4: At 5GS to EPS mobility with N26, the guard timer in the AMF (as specified in clauses 4.11.1.2.1 and 4.11.1.3.2 of TS 23.502 [3]) ensures that the UE Policy Association remains until the PCF for the UE detects that a UE Policy Association establishment is received from a PCF for the PDU Session indicating 5GS to EPS mobility.

NOTE 5: In the case that the UE is still registered and reachable over non-3GPP access, the PCF for UE can have two UE policy associations for one UE and based on local configuration the PCF can decide to use one of the UE policy associations to update URSP rule to the UE. The UE can receive URSP Rules over any of these two accesses.

NOTE 6: In the case that during the 5GS to EPS mobility there are more than one PCF for the PDU session maintaining PDN connections for the UE every involved PCF for the PDU session can establish a UE Policy Association towards the PCF for the UE. In such case when the PCF for the UE needs to provision the URSP to UE, the PCF for the UE first selects one of those UE Policy Associations for the delivery of URSP rules to the UE in EPS.

The UE can receive ePCO with UE Policy Container over any of the established PDN connections and then response over the same PDN connection.

When the PCF for the UE decides to update the URSPs in the UE via EPS, the PCF for the UE sends the updated URSP rules in UE Policy Container to the PCF for the PDU Session, then the PCF for the PDU Session forwards it to the SMF+PGW-C. The SMF+PGW-C transfers the received UE Policy Container via ePCO to the UE by triggering PDN-GW initiated Bearer without QoS Modification procedure as described in clause 5.4.3 of TS 23.401 [26]. After update the UE policy provided by the PCF, the UE response about the delivery result via ePCO to the network. The SMF+PGW-C transparently forwards the UE response to the PCF for the PDU Session via Update Bearer Response message and then the PCF for the PDU Session forwards it to the PCF for the UE via Npcf_UEPolicyControl_Update Request. If the SMF+PGW-C receives a rejection for Update Bearer Request message (e.g. due to paging failure), the delivery failure result is sent to PCF for the PDU Session and the PCF for the UE. To request to forward the result of delivery of UE policies, "Result of UE Policy Container delivery via EPS" PCRT is applied to the PCF for the PDU Session and the SMF+PGW-C as described in clause 4.11.0a.2a.10 of TS 23.502 [3].