N2/NGAP Interface

The N2 interface is the reference point between the RAN and the AMF. This interface connects the gNodeB to the AMF and is required due to Control and User Plane Separation (CUPS).

The N2 interface is needed because before accessing a service, the UE must be connected to the network. SMF handles the session control and the AMF handles the UE context. So, before initiating traffic or session, information, such as UE context, is required.

The N2 interface handles control-plane signalling. So, SMF uses N2 to generate and validate user traffic.