Skype Service Outage Affects Millions

December 22, 2010

Skype suffered a major service outage that left millions of users without VoIP calling services. What is the reason for the failure? Apparently, it is due to the fundamental way in which the Skype network is designed. Can you say “fragile”?

As Skype looks forward to its IPO, the last thing the company really needs is a major service outage. Unfortunately, that is exactly what happened today. Millions of Skype users are without service today, because they cannot get logged into the Skype network.

Skype acknowledged on its blog that the reason is apparently due to the fundamental way in which the somewhat fragile Skype network is designed. Skype wrote:

Skype isn’t a network like a conventional phone or IM network – instead, it relies on millions of individual connections between computers and phones to keep things up and running. Some of these computers are what we call ‘supernodes’ – they act a bit like phone directories for Skype. If you want to talk to someone, and your Skype app can’t find them immediately (for example, because they’re connecting from a different location or from a different device) your computer or phone will first try to find a supernode to figure out how to reach them.

Under normal circumstances, there are a large number of supernodes available. Unfortunately, today, many of them were taken offline by a problem affecting some versions of Skype. As Skype relies on being able to maintain contact with supernodes, it may appear offline for some of you.

This is not very reassuring. In fact, it highlights just how fragile peer-to-peer (P2P) networks really can be. What is not explained above is that a “supernode” is actually a machine that Skype taps to serve that role. It might be your machine or mine. In the past, there have been many complaints over the fact that Skype consumes bandwidth on college campuses around the world for the benefit of people who have no association with the universities. Now, it seems that these nodes are also a fragile element of the Skype network.

Of course, some might argue that a P2P network is more resilient than a traditional network that looks more like a “hub and spoke”. However, when 25 million users are depending on any single network architecture, it needs to be more resilient and should not be susceptible to these kinds of failures.