Windows Update And Skype Network Flaw To Blame For Outage

Skype is finally back online after a massive two-day outage which began on Thursday, August 16th and rendered the VoIP service useless for an estimated 220 million users. As we reported on Friday, Skype has denied charges that the outage was the result of an attack, but the company delayed an official explanation until today.

According to Skype the outage was caused by a massive number of users restarting their machines, which flooded the Skype network with login requests. Skype blames the restarts on Windows Update, presumably large numbers of users rebooting after installing this month's “Patch Tuesday” Windows patches.

However, while the restarts may have triggered the problem, they were not in fact the problem. The issue that caused to outage was Skype's own software. According to a statement on the Skype blog:

The high number of restarts affected Skype???s network resources. This caused a flood of log-in requests, which, combined with the lack of peer-to-peer network resources, prompted a chain reaction that had a critical impact.

Normally Skype???s peer-to-peer network has an inbuilt ability to self-heal, however, this event revealed a previously unseen software bug within the network resource allocation algorithm which prevented the self-healing function from working quickly. Regrettably, as a result of this disruption, Skype was unavailable to the majority of its users for approximately two days.

Skype has apologized for the outage, but it remains to be seen how the disruption will effect users' faith in the service.