What is SIP - Session Initiation Protocol?

17/07/2008

Is it worth taking a SIP?

With so much jargon flying around its often hard to work out which technology offers which benefits to whom these days. In telephony the buzz is around something which actually first surfaced in the 1990s; Session Initiation Protocol, or SIP. But what is SIP? What can it do? And should your business be taking a SIP?

SIP telephony, messaging, conferencing ..

Assuming you’re more interested in what technology does than how it does it, let’s try and keep this simple. The simple explanation is that SIP trunking is a bit like a normal phone line except that calls are routed not via a phone network but over the Internet.

But SIP is a clever beast in that unlike the traditional IP telephony standard - set by International Telephony Union or ITU - it is not dependent upon the network transport protocol which sits between an application and the Internet. Instead, as with the HTTP Web and SMTP email protocols from which it has evolved, it operates at the application level, the level which ensures communication is possible. It’s not tied to one medium but can operate multi-sessions with voice, date, video or Web content. Confused? That’s understandable! Bear with us.

What it does is the nifty part. Because it works with a range of other protocols which determine issues such as voice quality and location it can redirect and maintain the integrity of content so users can communicate from any location. Not being media dependent and capable of interacting with a range of applications it can host a variety of services including telephony, Instant Messaging - Microsoft’s Messenger service exploits SIP - internal phone networks (Private Branch Networks) and conferencing. 

Why Buy SIP?

The benefits of internet telephony are well documented (see our feature on phone bills can be sliced by as much as half, and international call rates by even more. SIP brings more to the table. SIP compatible phones offer the service you expect of a normal phone, plus work with other SIP phones, PABXs or servers and support the features you have come to expect. So that means programmable function keys, soft keys, hands-free operation, programmable ringer volume and so on, although to enjoy full functionality ‘phones may need to be linked to a server such as Ericsson’s Enterprise Multimedia Server.

But products like Avaya’s SIP enabled IP Office server can support not just telephony, but conferencing, voice messaging and provide an extensive customer service suite. It can offer multi-site hot desking, operate with PABX, analogue and digital phones and is scalable from two to 360 users, making it ideal for the SME business user. Polycom, which is one of the leaders in the conferencing market, has also harnessed SIP for its audio and video conferencing. Another option is the range of SIP telephones from the Ericsson 1400 Range.

SIP SIP Hurray

SIP telephony comes into its own by marrying the known low cost benefits of VoIP telephony with the flexibility to integrate with a wide range of applications and work with an array of media. It may not quite be communication with no barriers, but it is communication with far fewer.