There was a major skype outage last week and though there is an " official explaination " and other discussions about it floating around, I found this comment from one of the GigaOm readers more interesting to think about. Now this particular description may not accurately describe the problem (which might be speculation as well) but it does describe , in a few words, how skype's p2p network scales out. You should also take a look at the detailed discussion of the skype protocol here . Number of Skype Authentication servers: Count == 50; // Clustered Number of potential Skype clients: Count = 220,000,000 // Mostly decentralized Number of SuperNode clients to maintain network connectivity: Count = N / 300 at any one time. â€Â¢ If there are 3.0 million users online then the ratio is 3,000,000 / 300 = 10,000 == Supernodes available â€Â¢ Supernodes are bootstraps into the network for normal first run clients ("and handle routing of children calls"). â€Â¢