5.43.3.3 Local switching with UL CL/BP and local PSA UPF deployed on satellite

If the UEs using GEO satellite backhaul are served by the same SMF and the GEO satellite(s) serving the UEs has UPF deployed, the SMF may determine to activate local switching and N19 forwarding for the UEs, based on:

• AF request including of UE identifiers which require communication between UEs as described in clause 5.29.2; and/or
• Destination IP address(es) reported by on-ground PSA UPF as current reporting mechanism in clause 5.8.5.7. To enable the destination IP address(es) reporting, SMF configures the on-ground PSA UPF to detect UL packets with destination IP addresses which belong to the current UPF address pool.

If the SMF determines that the UEs (i.e. corresponding to AF request in bullet 1) and/or the Destination IP address(es) reported in bullet 2)) are under the same GEO satellite (or multiple connectable GEO satellites) based on GEO Satellite ID(s) reported by AMF and the UEs are allowed to access the DNAIs corresponding to the GEO satellite IDs, for each UE communicating with target UE(s) in the communication group, the SMF may select and insert the UPF deployed on GEO satellite according to the DNAI as UL CL/BP and L-PSA and configures UL CL/BP with the following rule:

• Route the data traffic received from the UE and destined to IP address(es) of the target UE(s) to the L-PSA.
• Route other data traffic received from the UE to the PSA UPF of the UE's PDU Session.

NOTE 1: The SMF determines the GEO satellites are connectable based on configuration.

The SMF configures the Local PSA with local forwarding rules to forward the data traffic to the target UEs directly. If the selected L-PSAs are different for the UEs in the communication group, N19 tunnel is established between the L-PSAs. For establishing N19 tunnel between the UPFs onboard the satellite, the UPFs are controlled by the same SMF. If UEs are members of the same 5G VN group, the SMF may configure the local data forwarding rules on L-PSA(s) using 5GVN user plane handing mechanism in clause 5.8.2.13.1 (Support for unicast traffic forwarding of a 5G VN).

NOTE 2: The selected UPF deployed on satellite can be inserted as UL CL/BP/L-PSA reusing existing UL CL/BP insertion procedures defined in TS 23.502 [3] or TS 23.548 [130].

N6 may be used for carrying traffic between L-PSA UPFs deployed on different satellites. If N6 is used, SMF configures corresponding N4 rules for processing traffic to/from N6.