No quick answer to a complex question

For those of us who have watched the VoIP (voice over IP) standards wars over the years, the current battles raging behind closed doors should come as no surprise. Nevertheless, if you sit on a VoIP evaluation committee, it might be worth your while to consider the challenges still to be met.

"Today, a Cisco (IP) phone won't talk to an Avaya IP PABX and vice versa," Lawrence Byrd, convergence strategist at Avaya, tells me. "We feel a lot of Cisco's protocols tend to be proprietary."

On the other hand, Michael Frendo, vice president of voice systems engineering at Cisco, tells me, "Standards lag behind the reality of the marketplace and what you can do." See what I mean?

Both Frendo and Byrd agree that RTP (Real-Time Transport Protocol) is pretty much established as the standard for the bearer channel, the one that actually carries the voice.

Things start to get dicey with the signalling channel, which manages traditional call-control features, such as call transfer, hold, and the conference button, as well as more interesting features yet to come. Those might include video, IM, presence, unified communications with speech commands, and a shared-line feature, in which a single extension rings simultaneously at your desk, at home, and on your PC while you travel.

But at present, if you have VoIP solutions from multiple vendors, I'm afraid neither call sharing nor many of the other features listed above will work. That would require VoIP interconnectivity standards that so far do not exist.

"The challenge for the industry is to lock down the standards at the higher levels," says Avaya's Byrd. Even if you don't have to worry about connecting using disparate VoIP systems today, suppose your company buys company X tomorrow. If they have an Avaya system and yours is Cisco, what do you do then? Rip and replace?

Oy vey, as my grandmother used to say.

Most industry players seem to be rallying around SIP (Session Initiation Protocol), a specification developed by the IETF. But SIP has a way to go before it can solve all the problems of VoIP.

"SIP is fairly young and still evolving," Cisco's Frendo says. "Certain features are continuing to be defined." Translation: plenty of bloody battles lie ahead before SIP truly becomes a standard. For example, there is no public standard for Cisco videoconferencing, nor does SIP address video yet.

One big interoperability challenge will be between VoIP vendors and major telecom carriers, which are slowly moving towards VoIP links themselves. A lot will depend on how the carriers decide to implement their own VoIP networks, Avaya's Byrd says.

And then, of course, there is the issue of security. Byrd says that the very nature of IP telephony protocols tends to open a lot of ports in your firewall. According to Cisco's Frendo, one solution called STUN (Simple Traversal of UDP (User Datagram Protocol) through NAT) opens up pinholes in the firewall to allow voice to pass through. "There is an active communication between voice and the firewall," Frendo says. Does that sound reassuring?

I decided to get sneaky and called Cisco customer support to get its take on interoperability. I told the support tech that I was in a rush but just wanted to know whether my Cisco system would interoperate with a business partner's Avaya system.

"There is no quick answer to a complex question," the tech said. Words to live by, I say.

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