User plane interfaces: N3, N6, N9

5GC User Plane Interfaces

The 5G core user plane is intentionally simple with only three interfaces carrying subscriber data traffic. N3 connects the gNB to the UPF and carries user data encapsulated in GTP-U tunnels. N6 connects the UPF to the external data network and carries plain IP packets without any tunneling. N9 connects UPFs to each other in chaining scenarios and uses GTP-U tunneling just like N3. This simplicity is a deliberate design choice because the user plane must handle massive throughput with minimal processing overhead, and adding complexity to the data path would degrade performance.