Standards come and standards go, but what makes a standard stick? While there’s widespread support for Session Initiation Protocol (SIP) as a signalling standard for telephony, conferencing and instant messaging, proprietary extensions could prevent it from becoming an interoperability standard.

“”If you look at SIP as a signalling standard for voice over IP, there’s no doubt in anyone’s mind that SIP will eventually replace H.323 as the de facto signalling standard,”” says Ronald Gruia, enterprise communications program leader with Frost & Sullivan Canada. “”SIP is a lot easier to implement than H.323.””

Several carriers, like Qwest and MCI, have embraced SIP; Microsoft has also entered the foray by making Windows XP SIP-compliant.

Proprietary Extensions

But, Gruia points out, some are looking at SIP as a standard for interoperability across multiple vendor platforms and this will depend on the level of SIP functionality built in by the vendors. Proprietary extensions mean that some phones could support greater levels of SIP functionality than others, and this is an advantage for the manufacturers.

“”They spent a lot of time developing those 500-plus functions and there’s no economic advantage to actually make everything open because they need to differentiate themselves,”” he says.

In the future, enterprises will likely use SIP, he says, but with proprietary extensions that are exclusive to each vendor.

Compared to Q.Sig, an older interoperability standard, SIP equipment will have more common functions, Gruia adds.

One of the main advantages of SIP is how broadly it’s being endorsed across the industry, says Jim Davies, chief technology officer of Mitel Networks. Microsoft has teamed up with Mitel to develop a signalling and media gateway for Microsoft Office Live Communications Server and the yet-to-be-released communication client, code-named Istanbul. The gateway is based on SIP, XML and CSTA standards and will allow Microsoft’s applications to access Mitel’s IP-based call control, devices and applications.

“”What you’re going to see is voice and instant messaging integrated across all the Microsoft applications, whether that be Outlook or Exchange,”” says Davies.

While there are still technical hurdles to overcome, he says that’s the least of the industry’s worries.

“”What we have to be realistic about is what limits standards is not usually technology,”” he says. “”What limits it is competitive business pressures.””

On the positive side, he says, big players like Microsoft are getting involved, which tends to drive adoption — whether people like it or not. “”At the end of the day, who’s not going to start opening up?”” he says. “”I’m hoping that large players like Microsoft will over time be able to deter that kind of [proprietary] behaviour because it will undermine what [SIP] could be.””

SIP was developed around the idea of building additional services on top of the protocol, rather than just using it as a communications protocol, says Mark Roberts, vice-president of product marketing with Polycom Inc., a Sunnyvale, Calif.-based video conferencing equipment manufacturer. H.323 is focused on the quality of the call, while SIP provides a basis for building applications, such as software that figures out whether users are present, he says.

The company rolled out Polycom MGC in October, which supports any mix of ISDN, H.323 or SIP-based applications in the same conference. This means users can bridge old conferencing environments with new ones.

“”As end users, you really don’t want to have a conversation about which kind of end points you’re using and which kind of algorithms,”” he says.

“”We envision a world where you’ll be able to connect regardless of the kind of network you’re using or indeed the protocol you’re using to connect through, where you’ve got multi-protocol support not only on the end points but also on the multi-point solutions, whether it’s audio or video.””

The challenge right now, he says, is getting that kind of thinking prevalent throughout the industry. Many vendors are still taking a parochial approach.

“”What that will do is create silos of communication where my fax doesn’t talk to your fax, and history is riddled with examples of where that’s happened and the marketplace becomes mired in discussions about standards.””

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