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VoIP experts savor SIP's potential

Panelists at the Next Generation Networks conference were bullish on SIP's capabilities and its future, while one of Cisco's top strategists explained why it has delayed end-to-end SIP support in CallManager.

BOSTON -- Luminaries speaking Tuesday at the Next Generation Networks conference were enthusiastic about Session Initiation Protocol (SIP) and its potential for enabling unified enterprise communications, but at the same time Cisco defended why it has been taking its time with the standard.

During a panel discussion, experts explained how SIP, the protocol that has become the foundation for IP-enabled voice, video and instant messaging applications, owes its success to its flexibility.

Jack Jachner, a senior director with networking vendor Alcatel, said the Internet Engineering Task Force (IETF) deliberately designed SIP so that it could be easily extended. That helped ensure its success by creating a common foundation that vendors could use to ensure interoperability, but leave enough leeway so they can customize the standard to meet their needs.

That flexibility has led to a family of related protocols, such as SIMPLE, which extends SIP for IM and presence; Reliable Provisional Responses, which indicates call progress; and others that assist quality of service, privacy and location transport.

David Oran, a fellow and top VoIP systems architect with Cisco Systems Inc., said SIP has evolved to the point where SIP-based products are more than capable of being full-featured replacements for traditional telephony systems.

However, Oran acknowledged that while Cisco's widely used VoIP platform, CallManager, utilizes SIP on the back end, it uses a proprietary protocol to communicate with IP phones. He said Cisco ships more SIP-enabled products than any other vendor and is committed to including end-to-end SIP support with CallManager 5.0 when it ships next year, but for now Cisco is taking its time.

"Our programmers can't work 87 hours a day," Oran said, noting that it takes time and effort to develop a high-quality SIP-enabled system. "We're not a startup. Our stuff has to work when we ship it."

In reality, Oran said the delay proves that Cisco is committed to SIP by ensuring the next version of CallManager will be fully tested and capable of performing well with any number of SIP-based phones in large enterprise implementations.

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Cisco's strategy has also been influenced by market demand. Oran said that right now, customers are more interested in buying VoIP products that lower telephony costs and provide PBX-level quality than gear that promises a myriad of unified communications possibilities via a broader range of end-point devices.

Meanwhile, Microsoft is using SIP in Live Communications Server 2005, its new enterprise IM and multimedia convergence offering. David Sokolic, Microsoft's lead program manager for Microsoft's live communications group, said SIP is key to unifying and simplifying enterprise communications.

"SIP is an area that Microsoft has made a big bet on in order to fulfill our vision of unified communications," Sokolic said. He added that future SIP extensions must be standardized, but the industry must come together quickly to finalize extensions in order to keep innovation moving forward at a brisk pace.

Attendee Tapio Aaltio, chief network architect with TeliaSonera in the U.K., said SIP is headed in the right direction, and that vendors' ability to extend the standard has created several compelling ways to unify enterprise communications.

Regarding Cisco's SIP strategy, he said it would be ideal if Cisco could have already incorporated SIP on both ends of CallManager, but that the company's decision to take its time is more than reasonable.

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