Skype swats "massive" outage bug

Skype has fixed a software bug that made the internet telephony service almost unusable for two days last week.

According to a statement released by Skype, the outage - which affected the majority of Skype's user base - came about on Thursday with "a massive restart of our users' computers across the globe within a very short timeframe".

The restart came about as the result of a routine Windows update. Skype's statement said: "This caused a flood of login requests which, combined with the lack of peer-to-peer network resources, prompted a chain reaction that had a critical impact."

The VoIP company, which is owned by eBay, admitted that the majority of its users had been unable to access the service between last Thursday and Saturday.

A spokesperson for the company confirmed a fix is now in place for a bug in Skype's network resource allocation algorithm. The bug, revealed for the first time on Thursday, had stopped Skype's in-built "self-healing function" from working properly, causing the most severe outage in the history of the popular VoIP client.

Skype was keen to say the outage was not the work of hackers or any other malicious activity, and it claimed its users' security "was not, at any point, at risk".

The statement said: "This disruption was unprecedented in terms of its impact and scope. We would like to point out that very few technologies or communications networks today are guaranteed to operate without interruptions. We are very proud that over the four years of its operation, Skype has provided a technically resilient communications tool to millions of people worldwide."

Writing on his blog after the disruption, Mark Main, a broadband analyst at Ovum, said it is "quite an achievement" for Skype, now almost four years old, to have gone so long without an outage of this severity. However, he also suggested Skype's quality of service has been deteriorating recently, and he said resilience remains a common issue for commercial VoIP services.

Main said: "Perhaps we should still consider some VoIP services as being like a shortcut over rocky ground instead of the smoother but longer and well-trodden path... You still broadly get what you pay for in telecoms and there is a compromise users must accept in these relatively early days of VoIP-based voice services, especially with the free on-net services."

Thirty per cent of Skype's 220 million customers are business users, according to the company's own figures, with the vast majority of those choosing internet telephony to save costs.

David Meyer writes for ZDNet UK