Frame relay SVCs vs. extranets

Now that someone finally is introducing frame relay switched virtual circuits, you have to ask, is it too late?

For three years, frame relay carriers have thrown fakes and jabs in the direction of SVCs, which are temporary paths that can be activated within minutes via E.164 addressing, a format similar to telephone numbers. SVCs differ from permanent virtual circuits (PVC), which have to be preprovisioned and maintained by you and the carrier and paid for each month whether you use them or not.

The main excitement behind SVCs in 1995 and 1996 was the idea of interenterprise networking. That notion envisioned a constellation of suppliers, distributors and customers who could be added to your frame net on a usage-only basis.

But when MCI announced frame relay SVCs at the NetWorld+Interop 97 show, it was something of a letdown. Sure, MCI may have beaten its competitors to the punch. But by now, if you're thinking of extending key corporate applications to outsiders, I'll bet it's because you know they all have browsers, not frame relay access equipment.

So is there a place for frame relay SVCs at a time when users are building giant intranets accessible to outsiders? Leaving aside the delays by ISPs in delivering these so-called extranet services, there may be some justification for MCI testing SVC.

"There are still a lot of things that you can do better over frame relay than an intranet or extranet," says Steve Taylor, president of Distributed Networking Associates, of Greensboro, N.C.

If you should want to extend legacy SNA applications beyond the corporate boundaries, for ex-ample, a frame re-lay SVC can encapsulate the traffic a lot better than a straight IP connection, Taylor says. Same with voice and video applications, he contends. And MCI officials say they're introducing SVCs up to 6M bit/sec specifically to carry large file transfers and delay-sensitive video applications.

In theory, SVCs could even replace PVCs. After all, another justification for SVCs was supposed to have been eliminating the need to manage PVCs, where addressing the data link connection indicators is a special, arcane skill.

Yet all-PVC frame relay nets are exactly what the market has generated over the past 18 months - frequently in exactly the interenterprise topology touted for SVCs and extranets. AT&T successfully has installed a 7,000-node frame net linking travel agents with the WorldSpan reservation network run by Delta, TWA and Northwest Airlines.

And Sprint and EDS have performed an 8,000-node installation for the System One travel network. MCI takes the cake for winning the contract for a 34,000-node frame net for the U.S. Postal Service, even if its only now beginning to install the net. Besides, there's already another fast-packet service that uses temporary circuits and E.164 addressing: the much-ignored Switched Multimegabit Data Service. "You could say frame relay SVCs are a politically correct version of SMDS," Taylor chuckles.

That's not much of an endorsement, to be sure. But frame SVCs should be a bit more marketable if MCI prices them right - and if there's a compelling reason not to simply use my browser and a phone line to access your network.