updated 09:45 am EST, Wed December 29, 2010
Skype identifies old Windows Skype as failure
Skype honored its promises today and gave a post-mortem on the reasons behind its worldwide outage. The company blamed the failure on a bug in a slightly outdated Windows version of Skype. After some servers handling offline text chat were overloaded, these older clients -- which were still 20 percent of all users --couldn't handle the delays and crashed, taking down some of the supernodes managing calls and putting too much strain on others.
The company had shut off the overloaded servers and tried to contain the problem, but it was too late to stop the cascade effect, according to Skype. Failures began occurring nearly at the 1PM Eastern peak usage period and put as much as 100 times the load on a given supernode. Each shuts down in the event of an extreme connection to shelter itself, but this only compounded the issue.
Teams eventually resorted to creating "mega-supernodes" out of some peer-to-peer connections to handle the extra load as well as devoting the group video chat servers to offsetting some of the burden. Most of the nodes were brought back to their regular statuses by Christmas, although some have been kept on for the holidays to prevent a repeat.
The issue was specific to Windows and didn't occur in any Mac version or on other platforms, including the mobile Android and iPhone apps or for TV users. It had already been patched in the Windows copy, but the company is now looking at making updates automatic to prevent a similar situation in the future. Beta testing and the failure response processes are under review and could be tightened at the same time. Skype's own capacity upgrades would likewise be monitored more closely.
Outdated software versions have been a regular problem for Windows and have been blamed for spreading malware and faults that otherwise wouldn't have affected modern code on any platform. Recent stats have shown nearly 18 percent of web traffic coming from old versions of Internet Explorer, for example, and nearly 58 percent still use Windows XP nine years after it was released.