Control plane interfaces: N1, N2, N4, N7–N15, N22

5GC Control Plane Interfaces

The 5G core control plane uses a combination of traditional reference point interfaces and modern service-based interfaces. The reference point interfaces connect nodes that are not on the SBA service bus. N1 carries NAS signaling between the UE and AMF, N2 carries the NG Application Protocol between the gNB and AMF, and N4 carries PFCP between the SMF and UPF. All other control plane interfaces between core NFs are service-based and use HTTP/2 over TLS. This distinction exists because the UE, gNB, and UPF are not SBA participants and therefore need traditional protocol stacks.