29.2443GPPInterface between the Control Plane and the User Plane nodesRelease 17TS
Stage 2 requirements for the support of 5G VN communication are specified in clauses 4.4.6 and 220.127.116.11 of 3GPP TS 23.501 .
The 5G VN group communication includes one to one communication and one to many communication.
One to one communication supports forwarding of unicast traffic between two UEs within a 5G VN, or between a UE and a device on the DN.
One to many communication supports forwarding of multicast traffic and broadcast traffic from one UE (or device on the DN) to many/all UEs within a 5G VN and devices on the DN.
5G VN Group Communication is optional to support. The SMF may instruct the UPF to forward unicast and/or broadcast traffic as described below if the UPF has indicated support of 5G VN Group Communication (see feature GCOM in clause 8.2.25).
There are 3 different traffic forwarding methods, i.e. UPF local switching, N6-based forwarding and N19-based forwarding, to forward traffic within the 5G VN group.
For all methods, traffic forwarding within the 5G VN group is realized by using a UPF internal interface ("5G VN Internal") and a two-step detection and forwarding process. In the first step, the packets received from any 5G VN group member (via it’s PDU Session, via N6 or via N19) are forwarded to the UPF internal interface (i.e. Destination Interface set to "5G VN Internal"). In the second step, PDRs installed at the UPF internal interface (i.e. Source Interface set to "5G VN Internal") detect the packet and forward it to the respective 5G VN group member (via it’s PDU Session, via N6 or via N19). If more than one 5G VN group has to be supported, the Network Instance set to a value representing the 5G VN group is used in addition to the UPF internal interface to enable isolation of the 5G VN group communication during the packet detection and forwarding process.
When N19-based forwarding is used, the SMF may correlate all the PDU sessions for the 5G VN Group members to generate the PDR and FAR corresponding to the group level N4-session for UPF as specified in clause 5.29.3 of 3GPP TS 23.501 .
For Ethernet unicast traffic on 5G VN Group Communication, the SMF may either explicitly configure DL PDR with the MAC addresses detected by the UPF on PDU Sessions supporting a 5G VN group, or rely on MAC address learning in UPF related with a 5G VN group by setting the Ethernet PDU Session Information indication in the DL PDR of the "5G VN internal" interface as specified in clause 18.104.22.168.0 of 3GPP TS 23.501 .
To enable IP or Ethernet type broadcast traffic forwarding of a 5G VN Group, the SMF may provide the PDRs related to the group level N4-session and each 5G VN group member’ N4 Session to the UPF as specified in clause 22.214.171.124.3 of 3GPP TS 23.501 .
The details of the PDR and FAR setting over N4 for unicast traffic forwarding within a 5G VN are specified in clauses 126.96.36.199.1 and 188.8.131.52.2 of 3GPP TS 23.501 .
The details of the PDR and FAR setting over N4 for broadcast traffic forwarding within a 5G VN are specified in clause 184.108.40.206.3 of 3GPP TS 23.501 .