Re: [GnomeMeeting-list] Outgoing calls from behind the NAT

[Damien Sandras <dsandras seconix com>]

Le mercredi 22 février 2006 à 00:34 +0100, Jan Kasprzak a écrit :
> 	Hi all,
> 
> I have a problem with Ekiga: the host A has a public IP address, the host B
> is a Linux 1:N NAT (masquerade), the host C is hidden behind the host B with
> a private IP address. Users at hosts A and C run ekiga, and both have
> accounts on ekiga.net. The ekiga at the host C is set up with
> "NAT traversal method: STUN" and "STUN server: stun.ekiga.net".
> 
> Case 0: when user at host A calls user at host C, everything works
> 	correctly, both users can hear each other in a reasonable quality.
> 
> Case 1: When user at host C dials 500 ekiga net, it also works as expected
> 	- I can hear the remote voice, and a delayed echo of my own voice.
> 
> Case 2: When the call is established in the opposite direction - host C dials
> 	user at host A, the user at host C does not hear anything, and the
> 	user at host A receives very low quality audio signal only.
> 
> 	I have tried to look at this problem with ethereal running at
> the public interface of host B, and it seems that the problem is that
> in Case 2 the ekiga at host A is sending the RTP traffic to the incorrect
> port number.
> 
> Case 1:            src IP        src port     dst IP        dst port
> from host C        B's public IP 5022         ekiga.net     14280
> to host C          ekiga.net     14280        B's public IP 5022
> 
> Case 2:            src IP        src port     dst IP        dst port
> from host C        B's public IP 1024         A's IP        5010
> to host C          A's IP        5010         B's public IP 5014
> 
> Note the "1024" versus "5014" in the Case 2. It is clear that the NAT host B
> cannot relay the RTP traffic to host C, because it has different ports
> than the outgoing traffic. The dump of Case 2 has been verified also on host A,
> so I think it is correct.
> 
> 	Is it a bug in ekiga? It works against the 500 ekiga net bot,
> and does not work agaist another ekiga client.
> 

It is due to the way the Linux NAT is working, I don't want to enter
into complex explanations, so I will go straight to the fact: have you
increased the UDP binding timeout as described in the FAQ?


> 	I can of course forward the UDP ports 5000-5100 from the host B
> to the host C, but this is not feasible for me because I want to have
> multiple SIP clients behind host B. Can siproxd or a local stund running
> on host B be used to make this setup working?
> 
> 	Thanks,
> 
> -Yenya
> 
-- 
 _      Damien Sandras
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