I don't know what tricks Hamachi and Skype have up their sleeves regarding NAT traversal, but I believe they're based on the same general techniques as STUN (eg, find your external NAT mapping, attempt simultaneous connection on both NAT and LAN addresses, maybe toss in some port scanning for symmetric NATs, and then spend years tweaking the result).
As for ICMP I've heard you can do some crazy things like setting the TTL really low of an outbound UDP packet and thus keeping your external NAT mapping alive without actually sending to a real remote port. You might even get a sense of how congested a gateway is (and thus try to infer total bandwidth utilization by multiple endpoints behind a gateway) using a similar low-TTL trick. However, I'm not sure of any ICMP tricks that directly relate to NAT traversal. -david _____ From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of arvind singh Sent: Sunday, August 19, 2007 1:08 AM To: [email protected] Subject: [p2p-hackers] Best NAT traversal options I have heard of three approaches for NAT traversal 1. Stun 2. Skype 3. Hamachi Does anyone know if Skype & Hamachi just use protocol based on STUN logic or are they doing anything smarter. Has anyone tried to decipher network traffic of Skype or Hamachi and found any interesting patterns/logic ? I tried to use network sniffer today on Skype traffic and found UDP packets to open large number of ports on my home router. Can anything be done using ICMP packets for NAT traversal? Look forward to good discussion on this topic Arvind _____ Choose the right car based on your needs. Check out Yahoo! <http://us.rd.yahoo.com/evt=48518/*http:/autos.yahoo.com/carfinder/;_ylc=X3o DMTE3NWsyMDd2BF9TAzk3MTA3MDc2BHNlYwNtYWlsdGFncwRzbGsDY2FyLWZpbmRlcg--%20> Autos new Car Finder tool.
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