Section: 4.22.3.3 Home-routed, the UE registered to the same VPLMN over both access
Content: In the case of home-routed roaming, when the UE is registered to the same VPLMN over 3GPP access and non-3GPP access, the procedure for establishing a MA PDU Session when the VPLMN is ATSSS capable and the UE requests a single-access PDU Session but no policy in the UE and no local restrictions mandate a single access, is the same with the procedure specified in clause 4.22.2.2.1, with the following clarifications and modifications: - In step 1, the UE sets Request Type to initial request and it may include an "MA PDU Network-Upgrade Allowed" indication in UL NAS Transport message and its ATSSS Capabilities as defined in clause 5.32.2 of TS 23.501[ System architecture for the 5G System (5GS) ]  [2] in PDU Session Establishment Request message. - In step 2, if the AMF receives the "MA PDU Network-Upgrade Allowed" indication, the AMF may select a V-SMF and a H-SMF that support MA PDU sessions. If the AMF determines that the requested S-NSSAI is not allowed on both accesses, the AMF shall not forward "MA PDU Network-Upgrade Allowed" indication to the V-SMF. - In step 3, the AMF sends the "MA PDU Network-Upgrade Allowed" indication, if received from the UE. If the AMF sends the "MA PDU Network-Upgrade Allowed" indication to V-SMF, it shall also indicate to V-SMF whether the UE is registered over both accesses. - In step 5, two DL N9 tunnel CN info and two UL N3 tunnel CN info are allocated by the V-SMF or by the V-UPF. Additionally, the V-SMF indicates to H-SMF the relationship between the DL N9 tunnel CN info and the access type. If the single CN Tunnel is established by the H-SMF, the DL N9 tunnel CN info binding to the access over which the NAS message is received is to be used. - In step 6, the V-SMF provides the "MA PDU Network-Upgrade Allowed" indication, if received from AMF, together with an indication whether the UE is registered over both accesses. - After step 6, if the H-SMF receives the "MA PDU Network-Upgrade Allowed" indication, the H-SMF may decide to convert the single-access PDU Session requested by the UE into a MA PDU Session, if dynamic PCC is not to be used. The H-SMF may take this decision based on local operator policy, subscription data indicating whether the MA PDU session is allowed or not and/or other conditions, which are not specified in the present document. If the H-SMF receives ATSSS Capabilities from the UE but does not receive "MA PDU Network-Upgrade Allowed" indication from the AMF, the H-SMF shall not convert the single-access PDU Session requested by the UE into a MA PDU Session. - In step 9, if dynamic PCC is to be used for the MA PDU Session, the H-SMF sends an "MA PDU Network-Upgrade Allowed" indication instead of "MA PDU Request" indication to H-PCF in the SM Policy Control Create message if the MA PDU session is allowed based on the subscription data. The H-SMF also provides the ATSSS Capabilities of the MA PDU session. The H-PCF decides whether the single-access PDU Session can be converted into an MA PDU session or not based on operator policy and subscription data. - In step 13, the H-SMF sends "MA PDU session Accepted" indication to V-SMF in the Nsmf_PDUSession_Create Response message. - In step 14, the V-SMF includes the "MA PDU session Accepted" indication in the Namf_Communication_N1N2MessageTransfer message to the AMF. The AMF mark this PDU session as MA PDU session based on the received "MA PDU session Accepted" indication. - In step 16, the UE receives a PDU Session Establishment Accept message, which includes ATSSS rules and indicates to UE that the requested single-access PDU session was established as a MA PDU Session. - After step 18, two N9 tunnels between the H-UPF and the V-UPF as well as two N3 tunnels between the V-UPF and 5G-AN are established, or, if the H-UPF is connected to two different V-UPFs, the H-UPF has one N9 tunnel with each V-UPF.