[Serusers] nat + multiple RTP proxy

[Klaus Darilion]

The problem was already discussed in 
http://lists.iptel.org/pipermail/serusers/2003-November/003461.html
and the suggested solution was the same as your solution.

Klaus

> -----Original Message-----
> From: dhiraj.2.bhuyan at bt.com [mailto:dhiraj.2.bhuyan at bt.com] 
> Sent: Friday, December 12, 2003 6:39 PM
> To: jiri at iptel.org; sobomax at portaone.com
> Cc: serusers at lists.iptel.org
> Subject: [Serusers] nat + multiple RTP proxy
> 
> 
> Greetings list,
> I spent some time looking into the rtpproxy and nathelper 
> code. Currently, nathelper + rtpproxy will work ONLY if there 
> is "one" RTP proxy on the path. In a scenario like -
> 
> UA1 ---- NAT ---- SER/RTP1 ----- SER/RTP2 ---- NAT --- UA2
> 
> where UA1 and UA2 are subscribed to two different SERs and 
> are also behind NAT, RTP proxy 1 never forwards the RTP 
> traffic from UA1 to RTP proxy 2 (because of the way it is 
> designed) since RTP1 is waiting for at least one RTP packet 
> from RTP proxy 2 and vice versa - hence the deadlock.
> 
> This can be fixed if the RTP proxy waits for one UDP packet 
> from the device behind NAT, but does not wait for any packets 
> from the device it thinks is not behind NAT before forwarding 
> it the RTP traffic (coming from the other end). Thus in the 
> above scenario, RTP 1 waits for at least one packet from UA1 
> - but does not wait for any packet from RTP2.
> 
> I am writing a patch for nathelper and rtpproxy to add this 
> functionality (should be available by next week). Anyone - 
> any thoughts on this?
> 
> Dhiraj Bhuyan
> Network Security Specialist,
> BT Exact Business Assurance Solutions
> 
> Tel:   +44 1473 643932
> Mob:   +44 7962 012145
> Email: dhiraj.2.bhuyan at bt.com 
> 
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