Windows XP: A SIP VoIP implementation that works

By Robert Smithers
Network World, 03/04/02

Many conversations among the voice-over-IP cognoscenti who have cycled through our labs recently turned to the new Windows XP operating system and its embedded Session Initiation Protocol stack.

A cursory tire kicking during our recent SIP-H.323 interoperability testing left us with the distinct impression that Microsoft has a SIP-based voice-over-IP implementation that actually works.

While most of the network industry is busy shaking its collective head at XP's well-chronicled security debacles, voice-over-IP professionals are positioning their products for the real opportunities Microsoft's SIP move will soon present.

Our take on what this all means follows:

Microsoft sees an all-IP-based communications world, and wants to own it. Microsoft has owned the PC and the e-mail world for a while now. But one click on the Actions drop-down menu of Windows Messenger outlines a brazen manifesto that Microsoft wants the rest of the IP services world, too. Options like "send an instant message" sit there among other, more standard data-only options. It's no surprise that Microsoft's protracted legal battles have done nothing to dim its initiative. Now it has a communications platform that can get it where it wants to go.

Because Windows is well established as a third-party call control platform (for example, Cisco CallManager runs on a Windows 2000 platform), we wouldn't be surprised to start seeing embedded Windows versions on IP phones in the near future.

The trajectory of the voice-over-IP market's maturation will change considerably. It's a forgone conclusion that voice over IP will be a ubiquitous reality. But after three years of hype, voice-over-IP systems are only now beginning to show viability as an alternative to PBX. Voice over IP has overpromised and underperformed. As XP users get the hang of Windows Messenger, the commensurate demand for real-time communications will jerk voice over IP out of its prolonged adolescence, particularly in the carrier and service provider markets, where demand for public switched telephone network origination and termination services will increase.

SIP will be the call control protocol. During a recent e-mail exchange with the engineers in our lab, Imad Yanni, an XP product manager, said: "The H.323 support is important because we recognize that many developers and customers have made investments in H.323-based solutions. Still, SIP has potential to better enable new, innovative forms of communications. As a result, Microsoft is focusing its development energies toward these SIP standards. Going forward, we do not expect to do any further H.323-based development."

Cisco, Alcatel and Siemens have hedged their bets by allocating development resources for H.323 and SIP. Microsoft's endorsement will do much to move more development resources to SIP. A victory for SIP means moving intelligence out of the core and into the endpoints. Right up Microsoft's alley.

In our travels, we used to laugh when SIP enthusiasts called H.323 "legacy voice over IP." We're not laughing any more.