Circuit-Switched Networks

By eweek  |  Posted 2001-09-24

Most enterprises are poorly prepared to deal with natural disasters or terrorist attacks, often because they wrongly assume their circuit-switched networks have end-to-end backup resiliency.

The typical enterprise relies on an amalgam of circuit-switched, Ethernet, IP and wireless networks that far too often share the same central office and dont have the redundant routing to survive a direct hit to that office.

Circuit-switched networks have been rapped for not having the resiliency and redundancy to reroute traffic that runs into a fiber or wire cut, because they dont have as many dispersed points of presence as IP networks have.

But the big problem for enterprises running circuit-switched networks is that first stretch that connects them to the public network - a vulnerable mile, or two or three, that links them to a solitary central office shared by several carriers and service providers.

And thats a vulnerability that circuit-switched networks share with Ethernet, IP, data-only and sometimes even cable networks. If a tornado, earthquake, ice storm or terrorist attack disables that shared central office or the lines leading to it, all data and voice communications for miles around could stop dead in their routes.

Small and midsize enterprises rarely have backup lines connecting them to the public network - and when they do, they too often find that both lines go to the same central office.

Businesses wrongly think theyre protecting themselves by getting one line from, say, Verizon to connect to the public network, then turning to a second carrier for backup, Gartners Neil said. "What they dont know is both those companies are sharing or storing their equipment at the same premises."

Jack Norris, head of customer service and equipment of global carrier Equant, said the ideal safeguard is diverse local loops. "Theyre not always available," he said. But office buildings that are served by >> more than one central office can install separate routes to the outside, and so offer the peace of mind that comes from redundancy.

Still, information managers have to be careful. A building may be served by both an incumbent carrier, such as BellSouth, and a competitive carrier, but that doesnt mean the two carriers are taking separate routes to the Internet.

"Its going to be quite expensive, but you have to look at this as an insurance policy - balance it against what it would cost to be knocked out of business for eight hours or a day or a week," Neil said.

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