Understanding Today's Skype Outage: Explaining Supernodes

That Skype uses supernodes is interesting, but makes some sense since it was developed by the same people who developed Kazaa (a P2P filesharing service), which as I recall has a similar architecture.

My theory: Tons of supernodes (static ip with no NAT, broadband, constantly on) are in the 20s-30s age group and are on holiday. Plus office and university machines that are normally left on have been turned off. The people I know in universities across Europe normally have skype on at work constantly, or at least during the day, and most have static ips on their uni networks so I imagine they get selected as supernodes quite often. I know many uni network admins have complained about skype using bandwidth. All those people just went on holiday over the last week or so along with all the people in uni dormitories. I'd expect that would have lost Skype thousands upon thousands of supernodes. Add to that an increase in calls due to the approach of Christmas; calls that are personal and use video and audio rather than just audio (which is more common in business usage patterns during the rest of the year). Holiday gamers turning off skype to stop lag would factor as well (doesn't matter if it's true or not, gamers blame everything but themselves during losses and would no doubt turn off skype). So a 20% or more drop in supernodes, 20% or more increase in calls and bandwidth, plus holiday torrents/youtube/hulu on the remaining nodes slowing them down and you have the perfect situation for this.

So much so that they actually licenced the Joltid technology that they spun out of Kazaa. There was a lawsuit:

http://blogs.skype.com/en/2009/11/joltid_settlement.html

There were in fact several lawsuits related to licencing this stuff.

That could very well be the case, but if that were really the cause you'd expect to see this pattern every year. However, it apparently didn't happen for at least two years in a row[1]. Also, I would have expected Skype engineers to have wised up to the situation by now if it were really a seasonal thing.

[1] Since the last outage was 3 years ago. I can't find a source for that right now -- would be interesting to see if the outage was also around Christmas time.