new UPF (intermediate) to SMF: N4 Session Establishment Response
The new intermediate UPF sends an N4 Session Establishment Response message to the SMF. In case the UPF allocates CN Tunnel Info, it provides DL CN Tunnel Info for the UPF acting as PDU Session Anchor and UL CN Tunnel Info (i.e. CN N3 tunnel info) to the SMF. If the Data forwarding indication is received, the new (intermediate) UPF acting as N3 terminating point also sends DL CN Tunnel Info for the old (intermediate) UPF to the SMF. The SMF starts a timer, to be used in step 20a to release the resource in old intermediate UPF if there is one.