Section: 4.13.8.2.2 group-level N4 session management procedures
Content: The SMF shall create an group-level N4 session on the UPF for a 5G VN group when N19-based forwarding is applied. The group-level N4 Session management procedures enable the SMF to create, update or delete the group-level N4 Session, e.g. add or delete N4 rules, allocate or release the N19 tunnel resources. In the case of N19-based forwarding is applied, the followings apply for the PDU Sessions targeting the (DNN, S-NSSAI) associated with a 5G VN group: - If the PDU Sessions targeting the same 5G VN group are anchored at different UPFs, the SMF shall create the group-level N4 Session in each involved UPF via N4 Session Establishment procedure (clause 4.4.1.2) in order to establish N19 tunnel(s) between the UPFs and install the N4 rules. - If the last PDU Session for this 5G VN group is released on a UPF, the SMF may delete the group-level N4 Session in the UPF via N4 Session Release procedure (clause 4.4.1.4) and release the N19 tunnel(s) between this UPF and other UPF(s) serving the 5G VN group via update of the corresponding N4 rules. - If an address of the UE within the 5G VN group is allocated or released, the SMF may update the N4 rules(e.g. PDRs and FARs) related to the UE address into the group-level N4 Session context via N4 Session Modification procedure (clause 4.4.1.3).