Section: 4.22.8.3 UE or network requested MA PDU Session Modification (home-routed roaming)
Content: The signalling flow for a MA PDU Session Modification when the UE is registered to the same VPLMN over 3GPP access and non-3GPP access and the PDU Session Anchor (PSA) is located in the HPLMN, is based on the signalling flow in Figure 4.3.3.3-1 with the following differences and clarifications: - In step 1b, the H-SMF may decide to update ATSSS rules and/or N4 rules based on updated PCC rules. - In step 1d, if the H-UPF determines that it cannot send GBR traffic over the current ongoing access e.g. based on the N4 rules and access availability and unavailability report from the UE, the H-UPF shall send Access Availability report to the H-SMF. When the H-SMF receives the Access Availability report, the H-SMF may decide to move the GBR QoS Flow to the other access as described in clause 5.32.4 of TS 23.501[ System architecture for the 5G System (5GS) ]  [2]. If the H-SMF decides to move GBR QoS Flow, the H-SMF triggers this procedure and afterwards moves the GBR QoS flow to the target access. - In step 3, if the H-SMF decides to move the GBR QoS Flow to the other access, the H-SMF sends updated GBR QoS Flow information contains associated access type and ATSSS rule to the V-SMF. Based on the information the V-SMF establishes AN resources for the GBR QoS Flow to the target access. - In step 3, when the H-SMF provides GBR QoS Flow information, the H-SMF includes associated access type in Nsmf_PDUSession_Update. When the H-SMF provides non-GBR QoS Flow information, H-SMF provides the information for both accesses in Nsmf_PDUSession_Update. - In step 3, if the H-SMF wants to update ATSSS rules, the H-SMF triggers Nsmf_PDUSession_Update and includes an updated ATSSS rules. - In step 4, if the H-SMF decides to move the GBR QoS Flow to the other access, the PDU Session Modification Command message is sent to the UE to update ATSSS rule of the UE so that the UE sends uplink GBR traffic over the target access. The V-SMF releases AN resources of the GBR QoS Flow in the source access. - In step 4, when the V-SMF establishes user plane resources for a QoS flows, the V-SMF provides QoS profile to the AN as follows: - for Non-GBR QoS Flow, steps 4 to 9 are performed over each access for which the MA PDU Session is established. - for GBR QoS Flow allowed in a single access, steps 4 to 9 are performed in the allowed access. - for GBR QoS Flow allowed in both accesses, steps 4 to 9 are performed in the access according to the decision by the SMF (as described in clause 5.32.4 of TS 23.501[ System architecture for the 5G System (5GS) ]  [2]). - In step 4, if the H-SMF provides updated ATSSS rules, the V-SMF includes the updated ATSSS rules in the N1 SM container (PDU Session Modification Command). When the V-SMF provides N1 SM container and/or N2 SM information, the V-SMF includes access type in the Namf_Communication_N1N2MessageTransfer to provide routing information to the AMF. The description of signalling flow for a MA PDU Session Modification when the UE is registered to different PLMNs over 3GPP access and non-3GPP access and the PDU Session Anchor (PSA) is located in the HPLMN, is based on above procedure with the following differences and clarifications: - The description of (V-)SMF providing QoS profile to the AN is not applicable and instead the regular procedures for QoS profile provisioning from (V-)SMF to (R)AN applies.