Overview

As operators began their migration to an Internet Protocol (IP) backbone, the need to transport the ISDN User Part (ISUP) and the Transaction Capabilities Application Part (TCAP) using the Transmission Control Protocol/Internet Protocol (TCP/IP) became paramount. Operators began deploying IP into their signaling networks as early as 1999 for the purpose of signaling transport. The Internet Engineering Task Force (IETF) began work on a replacement for the Message Transfer Part (MTP), which works well in a time-division multiplexing (TDM) environment but is not suited for TCP/IP networking.

The main difference between the Message Transfer Part (MTP) and SIGTRAN (which is an acronym for Signaling Transport) lies in the procedures and connection management. In addition, the SIGTRAN protocols provide an additional level of security not found in existing IP transport.

As IP networks continue to evolve within the telecommunications space, SIGTRAN is becoming more and more prevalent. In a Voice-over-IP (VoIP) network, it is SIGTRAN that interfaces between the Public Switched Telephone Network (PSTN) via a signaling gateway and Media Gateway Controllers (MGCs) in the VoIP network. The signaling gateway provides the function of converting ISUP over MTP to ISUP over SIGTRAN. The MGC then receives the ISUP messaging, and creates the equivalent Session Initiation Protocol (SIP) messaging for use in the VoIP network (or other protocol depending on the specific implementation).

In the IP Multimedia Subsystem (IMS), SIGTRAN plays a role as the interface to the PSTN...