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SIP promises sweet taste of interoperability

While some are disappointed that Session Initiation Protocol hasn't spawned more interoperable voice products, experts explain how SIP-based gear will soon unite voice, video and presence on the network.

Session Initiation Protocol, an emerging standard for Internet telephony, is being incorporated into a growing number of voice systems from vendors nationwide. And while the standard does not enable complete interoperability among today's products, experts said that in the coming years, SIP could be the protocol that unifies a vast array of enterprise applications.

Alcatel, Siemens and Nortel Networks Corp. have all been basing more of their VoIP systems on SIP, which is best known as the Internet Engineering Task Force's standard protocol for initiating interactive user sessions involving multimedia. But oddly enough, enterprise networking giant Cisco Systems Inc., an increasingly large player in VoIP, is not as far along as other vendors in regard to adding SIP to its products.

"Cisco has SIP elements," said Elizabeth Herrell, vice president with Cambridge, Mass.-based Forrester Research Inc. "It is in progress."

The industry has been down on SIP in the last six months because it hasn't delivered the kind of interoperability that was promised.

Zeus Kerravala,

Yankee Group

So far, it's been smaller vendors such as Sunnyvale, Calif.-based Zultys Technologies have been most aggressive.

Zultys began integrating SIP into its systems three years ago and launched its first SIP-based products a year and a half ago. Now its products offer interoperability with a range of handsets. One customer, Coldwell Banker Elite, a Stafford, Va.-based real estate firm, for example, uses a Zultys IP PBX with phones from Pleasanton, Calif.-based Polycom Inc.

"If someone has an IP phone, they should be able to just plug it into the network and expect it to work," said Zultys president Iain Milnes.

The protocol is also being used with video- and presence-based applications, such as instant messaging. For that reason, SIP could serve as the common threat that unites voice and presence with video technologies, and Herrell said that's a very appealing vision for both vendors and businesses.

Coldwell Banker Elite installed a VoIP system in its three offices. Though the offices are no more than 15 miles apart and because of the way that local phone companies have divided the territory, calls between the offices are billed as long distance calls.

Kevin Breen, president of Coldwell Banker, said the VoIP system has allowed him to save significantly on long-distance costs. Additionally, he was able to cut the telecommunications costs of opening a new office from about $35,000 to $18,000.

Though Breen is no technician, he said flexibility was important because SIP should be able to function with any number of products the company installs down the road. He worked with Dumfries, Va.-based EtherSpeak Communications to find a voice system that would fill his needs.

"Kevin wanted choice moving forward," said Neil Darling, a partner with EtherSpeak. "As long as we stuck to the standards, we would have our options open now and into the future."

But SIP is still a work in progress. While it works well for necessary functions such as basic calling, standards officials are still working out the details for more complex features, said Zeus Kerravala, a vice president with Boston-based Yankee Group.

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"The industry has been down on SIP in the last six months because it hasn't delivered the kind of interoperability that was promised," Kerravala said. "But it is unrealistic for anyone to expect a standard to change the way that companies do telephony overnight."

When vendors want to add in complex features, they must work ahead of the standards body, which often can create problems with interoperability. Patrick Ferriter, vice president of product marketing for Zultys, said when vendors such as Zultys do create new features, they work with a standards body to try to get them incorporated in the standard.

Herrell said like most standards, SIP is moving ahead in fits and starts, but it is trudging forward. And because of the integration with presence based applications, the potential for SIP is great.

Kerravala expects it to take two years before SIP allows broad, full-featured interoperability. In the meantime, he said businesses should ensure that their vendors have a solid road map for adding SIP to their products. Plus, he said it is important to be sure that that when a product's features deviate from the standard, those features are upgraded when they become available.

"This is the progression that all standards go through," Kerravala said.

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