Session Initiation Protocol (SIP)

SIP is spilt in to three different yet over lapping technologies; Voice, Text and Video. The G3 mobile network is built on SIP protocols. You may have heard of presence, as in best method of contacting some one, either by voice, text or e-mail, this is also based on SIP, this is an enterprise application which will rapidly move into the SME market. Companies such as Microsoft have been actively using SIP as a protocol for a range of applications such as unified communications server.

The Voice World

SIP provides a signalling and call setup protocol for IP-based communications that can support a superset of the call processing functions and features present in the public switched telephone network (PSTN). SIP by itself does not define these features; rather, its focus is call-setup and signalling. However, it has been designed to enable the building of such features in network elements known as Proxy Servers and User Agents. These are features that permit familiar telephone-like operations: dialling a number, causing a phone to ring, hearing ring back tones or a busy signal. Implementation and terminology are different in the SIP world but to the end-user, the behaviour is similar.

SIP is the next logical step in the evolution of voice communications; routing voice calls over the internet provides additional features over and above ISDN and analogue lines. They are more cost effective.

A SIP Trunk is the equivalent of an ISDN channel, depending on your telephony equipment you can mix and match the amount of SIP Trunks and telephone numbers/DDI ranges.