Section: 4.23.7.2.3 Execution phase
Content: Compared to the procedure for execution phase in 4.9.1.3.3, the SMF interacting with the S-UPF, T-UPF, S-AMF and T-AMF is the I-SMF. The difference is as following: - Step 10a: If I-SMF is available for a PDU Session and the existing intermediate S-UPF is re-allocated, i.e. a new T-UPF is selected, the I-SMF invokes an Nsmf_PDUSession_Update Request (DL CN Tunnel Info of the T-UPF) service operation toward the SMF. The SMF sends N4 Session Modification Request message to PDU Session Anchor UPF, providing DL CN Tunnel Info to the PDU Session Anchor UPF. The PDU Session Anchor sends one or more "end marker" packets for each N3/N9 tunnel on the old path immediately after switching the path, the source NG-RAN shall forward the "end marker" packets to the target NG-RAN. - Step 10b: The SMF responds with the Nsmf_PDUSession_Update Response service operation to I-SMF once the PDU Session Anchor UPF is updated with the DL Tunnel Info of the T-UPF.