The security of the U.S. communications network, II

See the first installment of this article in yesterday’s, 15 April 2009, issue of HSDW

The fiber-optic cables that were cut in San Carlos, California, last Thursday were owned by Sprint Nextel, and appear to have worked in this way [the other cables cut were owned by AT&T, and AT&T’s predecessor, SBC Communications, typically built their regional fiber networks in rings]. The traffic was quickly rerouted to another path, and service to Sprint’s business customers was not interrupted.

CNet News’s Marguerite Reardon writes that unlike regional networks, which have multiple fiber rings running through and between cities, undersea cables that connect continents do not have this type of redundant architecture because it is too expensive to build it that way. This means that undersea cables are particularly vulnerable to fiber cuts, even if, because they are deployed beneath the ocean floor, they are more difficult to tamper with. Cables have been severed, though, and massive outages do occur from time to time.

Reardon notes that, by contrast, some networks in highly trafficked regions or networks that service critical customers have even more redundancy built into them. Michael Howard, a principal analyst at telecommunications research firm Infonetics Research, said that carriers such as Deutsche Telekom have begun building meshed networks so that there is a third path for traffic if fibers are cut or there is some other disruption on the network.

“The more traffic there is on the route, the more redundancy the carrier provides,” he said. “There are usually two aspects to a backup plan for networks. One is providing a diversity of virtual routes for the traffic, but the other is providing physically separate routes on separate fibers. I’d have to say the outage that occurred in Silicon Valley seems odd, given the traditional network architecture.”

AT&T’s network failure seems to suggest that at least one other path that would have rerouted the traffic was also damaged or cut. Given that the police indicated that the incidents occurred in only two locations, San Jose and San Carlos, Reardon says that it seems likely that there was already some damage or issue happening on AT&T’s network at the time the fiber was cut or the vandals managed to cut the ring in two places.

There is no way to know this for sure, but fibers are cut all the time in regional networks, and rarely do they cause massive outages that shut down entire regions for hours. Most