5G interfaces and service relationships

The control and user-plane paths connecting devices, radio access, Core functions and data networks.

UE ↔ AMF

NAS signalling for registration, mobility and session-related control.

RAN ↔ AMF

Control-plane signalling between the gNodeB and 5G Core.

RAN ↔ UPF

User-plane tunnel carrying subscriber packets.

SMF ↔ UPF

Control relationship used to install and manage packet-forwarding behaviour.

UPF ↔ Data Network

Connection from the user plane to the internet, enterprise network or edge application.

UPF ↔ UPF

User-plane connection between UPFs in multi-anchor or distributed paths.

N11

AMF ↔ SMF

Service relationship supporting PDU-session control.

Service-based APIs

NF ↔ NF

HTTP-based service interactions within the 5G Core service-based architecture.

Reference points and service-based interfaces

The 5G architecture can be represented using named reference points such as N1, N2, N3 and N4. Inside the service-based Core, network functions also expose named services through a common API framework. Both views describe the same wider system from different architectural perspectives.

Control plane versus user plane

Control-plane signalling registers devices, authenticates subscribers, selects services and establishes sessions. User-plane paths carry the actual application packets. Keeping these concepts separate makes the architecture much easier to understand.