RANAP (Radio Access Network Application Part) protocol is used in UMTS signaling between the Core Network, which can be a Message Switching Center (MSC) or a Serving GPRS Support Node (SGSN), and the UMTS Terrestrial Radio Access Network (UTRAN). RANAP is carried over the Iu-interface.

RANAP signaling protocol resides in the control plane of the radio network layer of the Iu interface in the UMTS (Universal Mobile Telecommunication System) protocol stack. The Iu interface is the interface between the RNC (Radio Network Controller) and the CN (Core Network).

RANAP is used for the following tasks:

• Relocation
• Radio Access Bearer Management
• Paging
• Transport of signaling between a UE (User Equipment) and the Core Network (non-access stratum signaling)

The Accelero™ RANAP API process both RANAP-CS (Iu-CS) and RANAP-PS (Iu-PS) messages through the SCCP message handler.  When an event is received, the SCCP message handler checks for the source of the event and invokes message handling and processing procedures based on the event source.  Both connectionless and connection-oriented messages are handled in this manner.  Connection-oriented messages on an established connection are passed through transparently.