5.8.2.13.2 Support for unicast traffic forwarding update due to UE mobility

To enable the service continuity when the PSA UPF serving the UE changed, the following applies:

• Keep the UE address unchanged if N6-based forwarding is not used.
• Configure the UE's N4 Session with N4 rules (PDR, FAR) to detect and forward the traffic to this UE via its PDU Session tunnel(i.e. N3 tunnel) on the target PSA UPF.
• If N19-based forwarding is applied: To switch the traffic towards this UE from the source PSA UPF to the target PSA UPF for N19-based forwarding, the SMF deletes the N4 rule (PDR) that detects the traffic towards this UE in the group-level N4 Session at UPFs involved in the 5G VN group (except the source PSA UPF), then adds or updates the PDR that detects the traffic towards this UE with the FAR containing the N19 tunnel information of the target PSA UPF in the group-level N4 Session at UPFs involved in the 5G VN group (except the target PSA UPF).