Skype suffered a serious server outage Dec. 22 that left swaths of its 560 million or so worldwide users without PC-calling capabilities for most of the day.
Skype-the VOIP service that many use to make free or low-cost long-distance calls from their PCs and phones-began going down for users around 11 a.m. EST, according to ReadWriteWeb.
Twitter was lit up with complaints from users unable to access the service. Skype, itself, addressed the problem around 2 p.m. EST in its blog and on its official Twitter account.
Skype's Head Blogger, Peter Parkes, said that after it noticed that the number of users online fell, it found that its "supernodes" had failed.
Supernodes are end users' computer linked by Skype's P2P software, acting like virtual phone directories. Skype employs millions of connections between supernodes and phones.
When a user clicks to place a call on Skype and the app can't locate a user's computer or phone, it will attempt to ping a supernode to connect the call. With supernodes failing, millions of people were unable to make calls.
"Under normal circumstances, there are a large number of supernodes available," Parkes said. "Unfortunately, today, many of them were taken offline by a problem affecting some versions of Skype."
As of 3:30 p.m. EST Wednesday, Parkes tweeted on Twitter: "Skype is now gradually returning to normal-we expect it may take several hours for everyone to be able to sign in again, however."
U.S. users who are still left without Skype service may consider Google's own free Gmail calling capabilities, powered by Google Voice.
The outage made cranky those tech pundits who rely on Skype to communicate with colleagues. GigaOm's Om Malik wrote in a blog post: "The outage comes at a time when Skype is starting to ask larger corporations for their business. If I am a big business, I would be extremely cautious about adopting Skype for business, especially in the light of this current outage."
There's yet another reason this outage comes at an inopportune time: Skype is reportedly trying to raise $1 billion for an initial public offering in 2011.
Assuming Skype gets everyone back online making calls today, this will hardly be the Skype' biggest failure.
That dubious honor came in August 2007, when Skype went dark for its then 220 million users for two whole days. Skype engineers discovered a software bug within the network resource allocation algorithm that prevented the service from righting itself when things went haywire following a massive restart of its users' computers as they rebooted after receiving a routine set of patches through Windows Update.