SIGTRAN is the name given to an 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. The most significant protocol defined by the SIGTRAN group was the Stream Control Transmission Protocol (SCTP), which is used to carry PSTN signalling 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)
A layer between SCTP user (e.g. M2UA, M3UA) and a connectionless packet network service such as IP.
SCTP is a reliable transport protocol operating over IP. SCTP is more akin to TCP than UDP, however it yields additional features to TCP while still supporting much of the same functionality.
SCTP is connection oriented and implements the same congestion/flow control. Detection of data corruption, loss of data and duplication of data is achieved by using checksums and sequence numbers. A selective retransmission mechanism is applied to correct loss or corruption of data.
M3UA supports for the transfer of all SS7 MTP3-User Part messages (e.g., ISUP, SCCP, TUP, etc.)
M3UA supports the seamless operation of MTP3-User protocol peers;
M3UA supports the management of SCTP transport associations and traffic between an SG and one or more MGCs or IP-resident Databases;
M3UA supports MGC or IP-resident Database process fail over and load sharing;