I seem to recall that Skype had the concept of "super nodes" which could facilitate NAT traversal for of users which didn't have a direct internet connection. M

I seem to recall that Skype had the concept of "super nodes" which could facilitate NAT traversal for of users which didn't have a direct internet connection. Microsoft got rid of that pretty fast and replaced it with Microsoft managed servers (which to be fair seems less sketchy that using random users machines as something akin to a STUN server).