[SR-Users] Cannot hear voice with symmetric NAT and STUN

[David]

Hello,

Look on Wikipedia and read the articles for SIP, RTP, NAT and STUN.

The answer to your question can be found in the above articles.

David

On 13-02-27 10:26 PM, Khoa Pham wrote:
> Hi, I have Kamailio as SIP server and RTP server. Client is PJSIP.
>
> I read that STUN is for non-symmetric NAT, and RTP server is for 
> symmetric NAT.
>
> Supposed A calls B.
>
> If A, B both use symmetric NAT and STUN, they cannot hear each other
> If A or B use non-symmetric NAT and NOT using STUN, they cannot hear 
> each other.
>
> Why is that?
>
> I read 
> http://tools.ietf.org/id/draft-takeda-symmetric-nat-traversal-00.txt for 
> Prediction Failure, is that related to this problem ?
>
> -- 
> Khoa Pham
> HCMC University of Science
> Faculty of Information Technology
>
>
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