Internet telephony giant Skype blamed its peer-to-peer interconnection system for a problem that some reports said resulted in millions of users being unable to make calls using the service on Wednesday.
According to an official blog post the Skype network uses what it calls "supernodes" which act as directories for finding users online. On Wednesday many of these supernodes were taken offline by a problem affecting some versions of Skype, the company said.
"Our engineers are creating new 'mega-supernodes' as fast as they can, which should gradually return things to normal," the company blog post said, adding that it may be several hours before the service returns to normal. Services such as group video calling may be offline longer.
In a status update, the company noted that "Enterprise products including Skype Connect and Skype Manager continue to function normally."
Reliably serving paying corporate customers is considered key to the success of the company, which is preparing for an initial public offering. The majority of Skype users pay nothing to use the service.
Other popular Web services that saw major outages this year include Paypal, which went down after a networking hardware failure in November, Yahoo suffered an outage that brought down its home page and search service in October, Facebook fell twice in a 24-hour period in September, and Comcast's entire Internet service along the US east coast went down in late November.