Section: 4.22.3.2 Non-roaming or roaming with local breakout
Content: In the case of non-roaming or roaming with local breakout, the procedure for establishing a MA PDU Session when the UE requests a single-access PDU Session is the same with the procedure specified in clause 4.22.2.1.1, with the following clarifications and modifications: - In step 1, the UE sets Request Type to initial request and it may include the "MA PDU Network-Upgrade Allowed" indication in UL NAS Transport message and its ATSSS Capabilities in PDU Session Establishment Request message, if the 5GC is ATSSS capable and no policy in the UE (e.g. no URSP rule) and no local restrictions mandate a single access for the requested PDU Session. The "MA PDU Network-Upgrade Allowed" indication indicates that the requested single-access PDU Session may be converted to a MA PDU Session, if the 5GC network wants to. - In step 2, if the AMF receives the "MA PDU Network-Upgrade Allowed" indication, the AMF may select a SMF that supports MA PDU sessions. The AMF does not send the "MA PDU Request" indication to SMF, but it sends the "MA PDU Network-Upgrade Allowed" indication, if received from the UE. 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 SMF. If the AMF sends the "MA PDU Network-Upgrade Allowed" indication to SMF, it shall also indicate to SMF whether the UE is registered over both accesses. If the PDU Session Establishment request is for a LADN, the AMF shall not forward "MA PDU Network-Upgrade Allowed" indication to the SMF. - After step 6, if SMF receives the "MA PDU Network-Upgrade Allowed" indication, the SMF may decide, if dynamic PCC is not to be used, to convert the single-access PDU Session requested by the UE into a MA PDU Session. The 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 SMF receives ATSSS Capabilities from the UE but does not receive "MA PDU Network-Upgrade Allowed" indication from the AMF, the SMF shall not convert the single-access PDU Session requested by the UE into a MA PDU Session. If the SMF receives a UP Security Policy for the PDU Session with Integrity Protection set to "Required" and the MA PDU session is being established over non-3GPP access, the SMF does not verify whether the access can satisfy the UP Security Policy. - In step 7, if dynamic PCC is to be used for the PDU Session, the SMF indicates to PCF that the SM policy control information is requested for a MA PDU Session via "MA PDU Network-Upgrade Allowed" indication if the MA PDU session is allowed based on the subscription data. The SMF provides the currently used Access Type(s) and RAT Type(s) for the MA-PDU session to the H-PCF. The SMF also provides the ATSSS Capabilities of the MA PDU session. - In step 10, the N4 rules derived by SMF for the MA-PDU session are sent to UPF and two N3 UL CN tunnels info are allocated by the UPF. - In step 11, for the MA PDU Session, the SMF sends an "MA PDU session Accepted" indication in the Namf_Communication_N1N2MessageTransfer message to the AMF. The AMF marks this PDU session as MA PDU session based on the received "MA PDU session Accepted" indication. - The PDU Session Establishment Accept message includes ATSSS rules which indicate to UE that the requested PDU Session was converted by the network to a MA PDU Session. - The SMF triggers the establishment of user-plane resources in both accesses, if it was informed in step 2 that the UE is registered over both accesses.