Skype had attributed the two-day crash of its service to a large number of Windows users logging on after rebooting their systems to install Microsoft's monthly updates.
The flood of log-on requests effectively launched a denial-of-service attack against Skype's log-on service.
Owing to a lack of additional information, the justification seemed to blame Microsoft. On Tuesday, however, Skype posted a full admission that sought to clear the software giant.
"We do not blame anyone but ourselves," wrote Skype spokesman Villu Arak in a blog posting.
"The Microsoft Update patches were merely a trigger for a series of events that led to the disruption of Skype, not the root cause of it. And Microsoft has been very helpful and supportive throughout."
Microsoft responded to repeated inquiries on Monday into its role in the outage, stressing that it had nothing to do with it.
"In a nutshell, there was nothing different or unusual about this month's patch release," said Christopher Budd, a security programme manager at Microsoft.
"The issue was a bug in the Skype software and not related to Tuesday's [Microsoft] updates."
Skype uses a peer-to-peer infrastructure that connects users without the interference of a central server, meaning that some users are attributed the role of a 'supernode' that allows the network to function.
Although Skype suffers from a high volume of sign-ons every month, August was struck by what Arak said was a "perfect storm".
"Our software's peer-to-peer network management algorithm was not tuned to take into account a combination of high load and supernode rebooting," he explained.
After fixing the way that Skype deals with a large number of system reboots, the company retuned its peer-to-peer structure.
Users have fumed at last week's collapse, while competitors rejoiced as Skype demonstrated that its service are unreliable. In an attempt to dispel these perceptions, Arak assured users that last week was an isolated incident.
"We would like to reassure our users across the globe that we have done everything we need to do to make sure this does not happen again," he wrote.
"We have already introduced a number of improvements to our software to ensure our users will not be similarly affected in the unlikely possibility of this combination of events recurring."
Skype absolves Microsoft from outage blame
By Tom Sanders on Aug 23, 2007 7:21AM