18/05/2005

Skype Supernodes

Imagine a normal broadband user, they've installed Skype on their PC and are happily chatting away. It's likely they're behind a NATted connection. They're probably talking to another user behind a NATted connection. In the IP world this makes life particularly difficult, so how do Skype get around it?

The answer is to use a man-in-the-middle who isn't NATted (I think what Skype call a Supernode).

So if 1st NATted user (a) calls 2nd NATted user (b) all their traffic goes through non-NATted user (c) who has twice the traffic going through their connection. Skype will actually try to put lots of connections through (c).

So if you're on a high bandwidth connection not using NAT and running Skype - you'll probably find it's not just your Skype calls you're handling. The traffic is encrypted, so the you cant actually intercept the voice traffic, but your bandwidth might diminish radipdly.
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