Home > Technical Articles > NGAP- Next-Generation Application Protocol over N2 Interface
NGAP is a Next-Generation Application Protocol that is found on the N2 reference point between the gNB and the AMF (Access and Mobility management function). It is to support both UE and non-UE associated services. This includes operations such as configuration updates, UE context transfer, PDU session resource management, and also support for mobility procedures. It is also used to convey uplink and downlink NAS (Non-Access Stratum) messages as a payload, as well as support CM (Connected Mode) idle and CM connected operations such as paging and UE context release.
NGAP consists of Elementary Procedures (EPs). An elementary procedure is a unit of interaction between the NG-RAN node and the AMF. these Elementary procedures are defined separately and are intended to be used to build up complete sequences in a flexible manner. The services provided by the NGAP are divided into UE associated and non-UE associated. The UE associated services are related to one UE and the non-UE associated services are related to the NG interface.
The NGAP is transferred over SCTP (Stream Control Transmission Protocol). NGAP protocol provides transport function between UE and AMF by offering NAS signaling transport. The NAS protocol provides mobility management and session management between the UE and the AMF.