VOiCOM VoIP Standards_Signalling Transport

Note:

The links and documents found on this page refer to standards, proposals and draft standards. Whilst we endeavor to post the most recent versions, please refer to the IETF RFC's ITU SG16 and W3C for latest status

Media Gateway: Terminates voice calls on inter-switch trunks from the PSTN, compresses and packetizes the voice data, and delivers compressed voice packets to the IP network. For voice calls originating in an IP network, the media gateway performs these functions in reverse order.
Media Gateway Controller: A media gateway controller handles the registration and management of resources at the media gateway(s). A media gateway controller exchanges ISUP messages with central-office switches via a signaling gateway (described below). Because vendors of media gateway controllers often use off-the-shelf computer platforms, a media gateway controller is sometimes called a softswitch.
Signalling Gateway: A signalling gateway provides transparent interworking of signalling between switched-circuit and IP networks. The signalling gateway may terminate PSTN/SS7 signalling or relay messages over an IP network to a media gateway controller or another signalling gateway. Because of its critical role in integrated voice networks, signalling gateways are often deployed in groups of two or more to ensure high availability.

The IETFs Signalling Transport Working Group (SIGTRAN) was formed to addresses PSTN signalling such as SS7 over IP Networks. This is hugely important, as it allows continuation of services offered directly via comparable TDM solutions and PBXs. SIP–T (SIP for telephones) is an IETF standard (within SIGTRAN) that allows SIP to be used for Q.931 & ISUP call setup between ISDN/SS7–based PSTN and SIP–based IP telephony networks (used also for transport of signalling types such as DPNSS and DASS).