[Serusers] STUN and Symmetric NAT

[Simon Barber]

possible way to get through symmetric NAT without permanent rtpproxy.

Initiate the connection using rtpproxy, as normal. Now, learn the udp 
port the NAT is sending RTP from. Now send a re-invite to both parties, 
and switch the stream to the udp port the NAT is using, instead of the 
rtpproxy. This will only work if the NAT uses the same external ip/port 
pair when the same internal ip/port pair is used (and I'm expecting that 
most sip phone will reuse the same internal ip/port pair when you 
re-invite). Apparently some NATs do this. (although I'm not a NAT expert 
- I have only read a few papers on the subject).

Simon


Klaus Darilion wrote:

> You can't overcome symmetric NAT with STUN. To traverse a symmetric 
> NAT you need:
> - A SIP proxy with NAT traversal (nathelper module)
> - An RTP proxy (or an generic TURN server and a SIP UA which supports 
> TURN)
> - A symmetric SIP UA (symmetric SIP & symmetric RTP)
>
> regards,
> Klaus
>
>> Hi,
>> Can someone please help me if my dialer does not support symmetric
>> signalling,  is there anyway to go through symmetric nat through the 
>> server
>> or configure from the server that asking the dialer to point to a STUN
>> server before reaching the UA. Please help........
>> regards, shirley
>>
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