[p2p-hackers] Re: TCP thru' double NAT?

[Zooko O'Whielacronx]

[responding on-list to off-list query]

> I know this p2p-hackers message is from loooong ago, but I had a quick 
> question -- does the TCP relay currently implemented in Mnet use the 
> technique described in Section 3.5 of that document? At the end it 
> says that "Unfortunately, this trick may be even more fragile and 
> timing-sensitive than the UDP port number prediction trick described 
> above... Applications that require efficient, direct peer-to-peer 
> communication over existing NATs should use UDP." It doesn't sound 
> like a technique to get good results with, although you report success 
> -- so I was just curious.

Hi Michael:

The Mnet hack is low-tech.  A node which is not behind NAT or firewall 
volunteers to be a relay server.  It receives msgs from node A via TCP 
and sends them to node B via TCP, all in user-land.  There are plenty 
of obvious drawbacks, but it works for Mnet's purposes.

I believe Skype does something similar, when Skype's more efficient 
alternatives fail.

Regards,

Zooko

---
Please excuse terse writing -- there is a baby in my arms.