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From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of David Barrett Sent: Saturday, September 01, 2007 12:24 PM To: 'theory and practice of decentralized computer networks' Subject: Re: [p2p-hackers] Effective TCP and UDP NAT Traversal (no relaying) There was recently (July '07) a big discussion on this topic on the BEHAVE mailing list. I posted some of my results here: http://www1.ietf.org/mail-archive/web/behave/current/msg02496.html Basically, I can get about direct 90% peer connectivity using UDP. Rumor is Alex can get something like 99% (Alex - care to share any detailed numbers?). I do care, but, sorry, can't share. It is not 99% though, I can tell you this much. At some point I made a comment on this list, that 97-98% should be achievable. Since then we added TCP NAT traversal and a handful of UDP traversal tricks. On other hand Hamachi's userbase profile has changed. Specifically, the percentage of home users (behind dumb routers) declined in favor of people behind proxies and other funny devices (e.g. load balancers). We got more people connecting from far places (hop count and latency-wise) as well. So the number works out to be about the same as it was before. With just the home users I suspect we would've been in 95-97% range, though I might be off. The IETF is pushing a protocol named ICE, but nobody knows how well it works (Adam - have you come up with any numbers yet?). Overall, it's much harder than it looks, even in the "simple" cases. The basic algorithm is: 1) Figure out the IP address of each node's NAT 2) Share each node's pair of (LAN,NAT) IPs with the other node via some central server 3) Try to connect over both the LAN and NAT addresses. 4) Apply a lot of voodoo tricks 5) Oftentimes it works Everybody seems to use a variation on this algorithm, though Alex recently made some suspicious comments suggesting otherwise. The way you described it, my comment still stands. I cannot elaborate more, but it is possible to deduce what Hamachi does differently. Alex
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