SIGTRAN

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SIGTRAN is the name given to an Internet Engineering Task Force (IETF) working group that produced specifications for a family of protocols that provide reliable datagram service and user layer adaptations for SS7 and ISDN communications protocols. SIGTRAN is logically an extension of the SS7 protocol family. It supports the same application and call management paradigms as SS7 but uses an IP transport called Stream Control Transmission Protocol (SCTP) as its underlying transport vehicle. Indeed, the most significant protocol defined by the SIGTRAN group was SCTP, which is used to carry PSTN signaling over IP.

The SIGTRAN group was significantly influenced by telecommunications engineers intent on using the new protocols for adapting VoIP networks to the PSTN with special regard to signaling applications. Recently, SCTP is finding applications beyond its original purpose wherever reliable datagram service is desired.

The SIGTRAN family of protocols includes:

ISDN User Adaptation (IUA)
MTP2 User Peer-to-Peer Adaptation Layer (M2PA)
MTP2 User Adaptation Layer (M2UA)
MTP3 User Adaptation Layer (M3UA)
Stream Control Transmission Protocol (SCTP)
SCCP User Adaptation (SUA)
V5 User Adaptation (V5UA)

For more information on SIGTRAN, refer to RFC 2719: Architectural Framework for Signaling Transport.

RFC 2719 also defines the concept of a Signaling Gateway (SG), which converts CCS messages from SS7 to SIGTRAN. Implemented in a variety of network elements including softswitches and Edge STPs, the SG function can provide significant value to existing common channel signaling networks, leveraging investments associated with SS7 and delivering the cost/performance values associated with IP transport.