In a statement on the Skype "Hearbeat" blog, Skype reveals that last week's outage in the internet telephony service was caused by a bug in Skype's network resource allocation algorithm, a bug that was triggered by the nearly simultaneous restart of a huge number of Skype customers' machines after a routine Windows Update download.
Last Tuesday was one of Microsoft's so-called "Patch Tuesdays," and the Windows Update mechanism downloaded a series of patches that required restarts. This massive number of Skype users dropping off the network, and then immediately attempting to log back in to the network simply overwhelmed the Skype network's self-healing function. Many Skype users were unable to log in for all of last Wednesday, and much of Thursday as well.
Skype does not point the finger of blame at Microsoft, however, and instead acknowledges that the problem lay in the Skype network code, and that the bug was merely waiting for a large stress on the network to trigger it.
