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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