Error in Skype's Software Shuts Down

Source: NYTimes

SAN FRANCISCO, Aug. 16 — The online telephone service Skype was not working for much of the day on Thursday, leaving its 220 million users, some of them small businesses that had given up their landlines, without a way to call colleagues, customers and friends.

Executives at Skype, a division of eBay that is based in Luxembourg, said its engineers worked throughout the day to bring the service back online. But they said that while they had pinpointed the source of the problem, they still did not know why it had resulted in a network failure, and they could not ensure that the service would be running smoothly again by Friday.

“There is a chance this could go on beyond tomorrow, but it’s our hope that it’s going to be resolved,” Kurt Sauer, Skype’s chief security officer, said. “What happened today was caused by a unique set of events, the genesis of which is not entirely understood.”

Skype allows its users to make calls over their computers. Calls to other Skype members are free. To make and receive calls to and from traditional telephones, users are charged below-market rates.

The Skype network uses a so-called peer-to-peer infrastructure, meaning that calls are routed through other users’ computers instead of a central hub. But it does have servers around the world, known as supernodes, that manage access to the network. A flaw in a crucial piece of software that connects users to these servers appears to have been the source of the problem.

Skype engineers said the flaw existed in every copy of the Skype software that had been downloaded since the service’s start in 2003.

Skype executives said they still did not know why the error, sitting dormant for four years, suddenly crashed the network. They cited problems with the Internet backbone in some parts of the world as a possible contributing factor.

In the community of devoted Skype users, the shutdown was met with a few conspiracy theories and a little frustration that a communication tool they had come to rely on was not available.

Phil Wolff, editor of the Skype Journal blog in Oakland, Calif., said he uses Skype to communicate with contributors in a half-dozen countries. “It’s just really awkward,” he said. “All of a sudden these channels of communication aren’t available anymore.”

Mr. Wolff and Mr. Sauer of Skype noted that the service had never had a major breakdown like this.

“We have a good track record about uptime,” Mr. Sauer said. “That doesn’t help people who were down today, but we are working every moment to recover from this issue and not to let it occur again. We want to get it fixed quickly and ensure that we are what we always said we were — a highly reliable, resistant network.”