Sigtran

Sigtran refers to a protocol for the transport of switched circuit network signalling protocols over an IP network. It is the evolution of SS7 which defines adapters and core transport capabilities that mix SS7 and packet protocols to provide users both the technologies

Internet dial-up remote access, IP telephony inter working with PSTN are some of the most used applications of sigtran.

Key components in sigtran achitecture are as follows:

• MGC–Media Gateway Controller, responsible for mediating call control (between the SG and MG) and controlling access from the IP world to/from the PSTN.
• SG–Signaling Gateway, responsible for interfacing to the SS7 network and passing signaling messages to the IP nodes.
• MG–Media Gateway, responsible for packetization of voice traffic and transmitting the traffic towards the destination.
• IP SCP – an IP-enabled Service Control Point (SCP). This exists wholly within the IP network, but is addressable from the SS7 network.
• IP Phone–generically referred to as a “terminal.”

The interfaces relevant to signaling transport include SG to MGC, SG to SG. Signaling transport may potentially be applied to the MGC to MGC or MG to MGC interfaces as well, depending on requirements for transport of the associated signaling protocol.

For interworking with SS7-controlled SCN networks, the SG terminates the SS7 link and transfers the signaling information to the MGC using signaling transport. The MG terminates the interswitch trunk and controls the trunk based on the control signaling it receives from the MGC. For interworking with PSTN (Public Switched Telephone Network), IP networks will need to transport signaling such ISUP messages between IP nodes such as a Signaling Gateway and Media Gateway Controller or Media Gateway.

Stream Control Transmission Protocol (SCTP), a core protocol in the SIGTRAN protocol stack, provides transport layer services over IP. Examples of such transport include: transport of signaling between a Signaling Gateway and Media Gateway or Media Gateway Controller; transport of signaling ("backhaul") from a Media Gateway to a Media Gateway Controller; transport of TCAP between a Signaling Gateway and other IP nodes. SCTP is used by one of the following User Adaption layer protocols.

• SUA: Signalling Connection Control Part User Adaptation Layer
• IUA: ISDN Q.921-User Adaptation Layer
• M3UA: SS7 Message Transfer Part 3 (MTP3) User Adaptation layer
• M2UA: SS7 Message Transfer Part 2 (MTP2) User Adaptation layer
• M2PA: MTP2 Peer-to-peer user Adaptation layer
• V5UA: V5.2-User Adaptation Layer