SIP (Session Initiation Protocol)

The Session Initiation Protocol (SIP) is a signalling protocol used for establishing sessions in an IP network. A session could be a simple two-way telephone call or it could be a collaborative multi-media conference session. The ability to establish these sessions means that a host of innovative services become possible, such as voice-enriched e-commerce, web page click-to-dial, Instant Messaging with buddy lists and IP Voice Server services.

Over the last couple of years, the Voice over IP community has adopted SIP as its protocol of choice for signalling. SIP is an RFC standard from the Internet Engineering Task Force (IETF), the body responsible for administering and developing the mechanisms that comprise the Internet. SIP is still evolving and being extended as technology matures and SIP products are socialised in the marketplace.

The meteoric ascent of the Internet as a rival to the circuit-switched telephone network has given rise to strong economic and technological reasons for converged services and architectures. In order to assimilate telephony services with the ubiquitous technology of IP, a signalling protocol is required to set up and tear down connections.

A number of different communities put forward solutions, each coloured by their own priorities and interests. The Internet community wanted to introduce innovative services based on enhanced web-authoring tools like XML and more open, peer-to-peer protocols and call models. The IETF offered SIP.

SIP was originally intended to create a mechanism for inviting people to large-scale multipoint conferences on the Internet Multicast Backbone (Mbone). At this stage, IP telephony didn't really exist. It was soon realised that SIP could be used to set up point-to-point conferences - phone calls.

The SIP approach exemplifies classic Internet-style innovation: build only what you need, to address only what is lacking in existing mechanisms. Because the SIP approach is modular and free from underlying protocol or architectural constraints, and because the protocols themselves are simple, SIP has caught on as an alternative to H.323 and to vendor-proprietary mechanisms for transporting SS7 protocols over IP.

At Siptel we can offer many solutions covering SIP based protocols for all sizes of Enterprises.