External PDU Session Point of Interconnect to Data Network
The UPF acts as an external PDU session point of interconnect to Data Network and supports N3, N4, and N6 interfaces. The PDU layer corresponds to the PDU that is transported between the UE and the PDN during a PDU session. The PDU session can be of type IPv4 or IPv6 for transporting IP packets. The GPRS tunneling protocol for the user plane (GTP-U) supports multiplexing of the traffic from different PDU sessions by tunneling user data over the N3 interface (between a 5G access node and the UPF) in the core network. The GTP encapsulates all end-user PDUs and provides encapsulation per-PDU session. This layer also transports the marking associated with the QoS flow. The 5G encapsulation layer supports multiplexing the traffic from different PDU sessions over the N9 interface (an interface between different UPFs). It provides encapsulation per PDU session and carries the marking associated with the QoS flows.
The following features are related to this use case: