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SIP gives VoIP technology a boost

There is change afoot in Voice over Internet Protocol technology that may make it more attractive for real use.

Enterprises are looking closely at Voice over IP (VoIP) technology for their telephony, conferencing and other communications needs.

And if they've been looking for a while, they may be starting to notice a change at the very heart of that technology.

Session Initiation Protocol (SIP) -- which initiates interactive user sessions that involve multimedia elements like video, voice and chat -- brings a new dimension to VoIP, cohesion with the Internet. 

SIP handles requests from clients and retrieves responses from servers. Participants are identified by SIP URLs. SIP determines the end system to be used for the session, the communication media and media parameters and the called party's desire to engage in the communication. SIP then sets call parameters at either end of the communication, handles call transfer and termination.

Another element of SIP's charm is that it makes it possible for users to initiate and receive communications and services from any location, and for networks to identify the users wherever they are.

SIP is an alternative to H.323 -- the IP videoconference transmissions protocol that's been in use since its approval in 1996. H.323 is the current industry standard, but for how long is a question worth pondering.

"Both H.323 and SIP do the same kind of thing, but the SIP protocol is very conducive to the new Internet," said Tom Lancaster, a consultant and author who contributes VoIP tips to SearchNetworking.

It may be that closeness to the Net that's generating so much buzz these days -- particularly at major industry trade shows.

Attendees were certainly interested in SIP at the recent Spring 2002 Voice on the Net (VON) conference in Seattle. At VON, several vendors announced new VoIP products targeting businesses ready to move to the SIP standard.

Polycom, Milpitas, Calif., debuted SIP-supported products at VON. Polycom announced it would support SIP in its desktop and conference phones.

A number of companies are planning to show SIP-based products at the upcoming spring Networld+Interop Conference and Expo in Las Vegas, as well.

SIP is also gaining traction from the inclusion of the standard in newer offerings from industry heavyweights like Cisco Systems and Microsoft.

But other vendors are high on the standard as well. Shoreline Communications, a Sunnyvale, Calif., IP voice communications company, uses SIP-based technology to provide enterprises with what it calls presence-based management.

By making the same protocols available for signaling between public devices and an enterprise's telecommunications system, Shoreline's concept is to enable the same level of connectivity inside and outside the organization.

"Our approach is to build a single device that has both gateway and gatekeeper intelligence in the device, with each component on the system able to provide dial tone," said Barry Castle, vice president of marketing for Shoreline.

That ability to provide dial tone from any point in the system makes it a virtually failsafe solution, according to Castle.

SIP still has some hurdles to clear before it can truly move toward becoming an industry standard. Not surprisingly, among those hurdles is the issue of security.

Castle says that for any system that gives so much access to an outside user, security is critical.

"Security and reliability are put in question when you have so much freedom at the endpoint," said Castle, who cites the E-911 system as an example of how crucial reliability is in this sort of technology.

"Whatever you do, you need to be able to guarantee a customer that that if he picks up a phone, and rings 9-1-1, for example, that the call gets forwarded to public safety personnel," he said.

And SIP standards for some advanced telephony features -- like call forwarding and certain conferencing features -- have yet to be settled.

Still, one of the most telling signs that SIP is indeed the wave of the future in VoIP is the adoption already of SIP standards in new products from the industry's leaders.

"Microsoft has invested heavily in SIP, so has Cisco, so it is definitely the way everything is going in this industry," said Lancaster.

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