Skype on Friday said its services were returning to normal after the internet communications group experienced its biggest global outage in three years.
Tony Bates, Skype’s chief executive, told customers via a blog and accompanying video that the engineers had identified the problem and stabilised the core instant messenger, audio and video services, which were running at about “90-plus per cent of what we’d typically see from a user load on a day like today”.
Mr Bates said the outage, which hit during a peak period for the online calls service on Wednesday, was caused by a “software issue” and not by a malicious attack.
Millions of people rely on Skype for calls to friends and family overseas over Christmas because it is cheaper than using landline and mobile networks. Skype provides free calls between users of its service, charging for outbound and inbound calls between landlines or mobile phones.
Mr Bates apologised for the problems and promised Skype users calling credit vouchers as compensation. Pay as you go and pre-pay users are being offered a Skype voucher for 30 minutes of free calling to landlines anywhere in the world. Active subscribers are being offered a week’s extra subscription service.
“It’s been a tough 24 hours for many of you – and I’d like to thank you for your patience as we bring Skype back to normal,” Mr Bates said.
The service failure comes ahead of Skype’s planned stock market offering next year, which it postponed as it seeks to push harder into the competitive business telephony market. Skype, which is partly owned by Ebay, was completely offline for more than three hours on Wednesday evening, UK time.
At peak times, more than 25m people use Skype simultaneously. Skype’s 800 employees rely on their own service for internal communications too, forcing them back on to e-mail and traditional phones during the downtime.
Skype explained that the outage was caused by problems with the “supernodes” upon which it relies to route much of its traffic.
As a peer-to-peer service, Skype does not have a central exchange like a regular telephone network, instead it passes call information along a chain of users across the regular internet.
Although Skype has some of its own dedicated servers, supernode functions can often be performed by regular users. Skype’s engineers repurposed some of their servers that were running non-core functions, such as group video chat, to try and fix the problem.
The distributed nature of Skype’s network removes a “single point of failure” which can affect traditional telephone exchanges, but also means that errors can be more widespread and difficult to fix.
Skype’s last major outage, in August 2007, was caused by a different problem relating to a software update.