Section: 5.43.3 Local switch for UE-to-UE communications via UPF deployed on GEO satellite 5.43.3.1 General
Content: The UE to UE traffic may be locally routed by UPF(s) deployed on satellite (i.e. through local switch) to the target UE without traversing back to the satellite gateway on the ground. Local switching via UPF(s) deployed on satellite in this clause only applies on GEO satellite backhaul case and considers only DNNs and slices for 5G VN. N19 tunnel may be established between two UPFs deployed on different satellites for traffic between UEs. Also, N6 may be used for carrying traffic between UPFs deployed on different satellites. Only a single SMF is supported for local switching and N19 forwarding, i.e. both UEs are served by the same SMF. NOTE: The latency optimisation that can be gained by inter-satellite link between UPFs on different GEO satellites depends on the distance between the satellites that can be substantial, depending on the number of deployed satellites. Clause 5.43.3.2 describes the case of PSA UPF deployed on satellite, clause 5.43.3.3 describes the case of UL CL/BP and local PSA deployed on satellite (PSA UPF is on the ground). Selection of PSA UPF or UL CL/BP/local PSA on satellite is described in clause 6.3.3 and determination of DNAI to select the UPF deployed on the corresponding GEO satellite reuses the mechanism described in clause 5.43.2. A combination of DNN/S-NSSAI is assigned by the operator for the communications between UEs where backhaul with UPF is deployed on GEO satellite, the URSP is described in TS 23.503[ Policy and charging control framework for the 5G System (5GS); Stage 2 ]  [45] and its configuration to enable the selection PSA UPF on the GEO satellite reuses the mechanism described in clause 5.43.2.