Re: Poll: Both ends behind NAT...

On Sat, Nov 22, 2003 at 11:47:38PM -0800, Ed Kapitein wrote:
> Hi All,
> 
> I am happy to see speakfreely working with the nat
> traversal code.
> There is one "flaw"" in this setup however.
> Asume two people in a internet cafe to start
> speakfreely.
> Now the NAT router *MUST* change the port of one of the
> inside hosts in order to deliver the return packets to
> the corect inside host.
> (now i come to think of it, if two people start SF
> simultaniously, one might end up with 2 incomming
> streams !)
> 
> Did anyone found a solution to this?
> (as much nitty gritty technical details as possible
> please... i love the technical details of SF)
> 

I don't think this is much of a problem if the router is smart enough.
In this case UDP is in our favour.  The router itself doesn't need to
bind sockets to ports, so the outgoing traffic from both of the
clients can share the same port number.  The reverse direction should
then still work correctly provided the router then uses the remote
address in order to determine the correct internal machine to route
to.  A router designed for large internal networks would do that. 

The problem then is only if A and B share a NAT, C and D share a NAT,
and A talks to C at the same time as B talks to D.   I think we'll
just have to live with that being a conflict....

Soren

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