OPS' Getting Hip To SIP Could Be Key To VOIP


When cable's technical intelligentsia start to talk heatedly about a particular technology, and when big companies like AT&T, Verizon and Microsoft get behind that technology, a translation seems in order.

Welcome to SIP, which is barreling down on this industry like a runaway train. Like bandwidth-gulping peer-to-peer (P2P) applications (think KaZaa here), SIP is one of those realities that is already happening. And it will continue to happen, whether you like it or not.

SIP stands for "session initiation protocol." True to its name, it's a behind-the-scenes way for computers, handheld gadgets, and telephones to establish paths (sessions) to talk with each other, over the Internet. Telecommunications people call it a form of "distributed
call signaling," as opposed to "centralized
call signaling."

Unlike PacketCable 1.0, the cable industry's method for building a voice over IP (VoIP) service, which uses a form of centralized call signaling called "NCS," for "network-based call signaling," SIP doesn't require anything from the network.

Instead, SIP anchors the intelligence in the "end points" — phones, PCs, personal digital assistants (PDAs), or whatever else spawns from the world of consumer electronics gadgets. SIP assumes a "dumb" broadband network.

SIP matters for several reasons. Probably most important is what AT&T will likely do with it — in about a month, if it remains true to previously announced schedules. That's because SIP is what's under the hood of AT&T's move to offer residential VoIP service.

It'll go something like this: You (and your broadband Internet customers) see their offer for inexpensive phone service. (AT&T plans to "be competitive" with similar services, like Vonage, which goes for about $34.95 per month for unlimited dialing in North America.)

You (or your broadband customers) order. AT&T sends you a little plastic box. You plug your phone into the box. You plug the box into the Ethernet jack on your cable or DSL modem.

Within 10 provisioning minutes, you get voice service. AT&T finally gets its residential last mile, without spending another dime to ride it. The cable or DSL provider gets nothing, except more traffic.

In other words, it works much like Vonage — but it's AT&T's, with AT&T's brand and marketing resources. Ditto for Verizon.

Those little plastic box "SIP adapters," by the way, reached the commodity-almighty $50 price point in Asia last year.

Microsoft's angle is to slip SIP into its Windows XP operating system, making it a sort of communications Trojan horse. There's a fairly simple reason, SIP aficionados say: One of the design goals of SIP was to make it super easy to upgrade for other services, like video phone.

Or this other relatively new thing: "presence."

If you're like me, when you first heard someone say
"presence," you had an eye out for a gift-wrapped box. Be careful there. When someone says they want to get into presence, it doesn't necessarily mean they want to get into presents. Such is the nature of the spoken word.

"Presence" is a noble attempt to define a very amorphous category having to do with where people are, and which of their gadgets they're currently using. It means several things, but usually it starts with putting instant messaging (IM) on more devices than the PC.

Or it means keeping track of where you are (your "presence") so that voice, text or video communications can move with you. People sometimes call this "find me/follow me."

The point is, SIP lends itself to the kinds of timely innovation that brought us e-mail and Web browsing. That was the intent when it was devised, four years ago next month. Like PacketCable, it starts with voice, but morphs into other things — likely much more quickly.

SIP isn't necessarily bad news for cable operators. With a few tweaks, cable could offer SIP-based services. The PacketCable Multimedia specification (so named to move the spec beyond its voice origins) will accommodate SIP, and SIP extensions, CableLabs people say.

What cable people find scary about SIP, at first glance, is this: A technician installs a combination cable-modem/multimedia terminal adapter (known in PacketCable lingo as an "MTA") in somebody's house, ostensibly to hook them up to broadband Internet. Let's say the MTA is also configured for SIP services.

The new broadband customer zips off and connects herself to AT&T's voice service.

Could happen, but, cable's growing base of SIP proponents caution that it's incorrect to connote SIP capabilities with potential VoIP churn. The box that AT&T, Verizon and others send out, for example, will be "trained" to point customers at their servers, to set up the service.

Therefore, a cable-based SIP offering could be outfitted similarly — to point customers to cable's VoIP or multimedia offerings.

A couple of hundred years ago, people thought tomatoes were poisonous. Then Thomas Jefferson ate one, and didn't die.

With SIP, the most poisonous outcome is probably the one that comes with not (ahem) sipping — but only if you believe that you can either let things happen, or make things happen.

Either way — with full credit to CableLabs' Glenn Russell for the quip —SIP happens.

That's why SIP matters. Next time, more on how it works.