@Mitan,
"most of the time" is not really correct. It depends on our decisions. Here I want to support peer 2 peer call when both UA does not in symmetric NAT, to reduce task for the rtpproxy :)
On Mon, Mar 4, 2013 at 5:43 PM, Mitan Lopez mitan23@aol.com wrote:
So RTP proxy servers are used most of the time in Internet to communicate between 2 UA's? (in this case why bother to check all those lines in kamailio cfg?)
Mitan Lopez mitan23@aol.com
-----Original Message----- From: Alex Balashov abalashov@evaristesys.com To: sr-users sr-users@lists.sip-router.org Sent: Mon, Mar 4, 2013 11:30 am Subject: Re: [SR-Users] Cannot hear voice with symmetric NAT and STUN
On 03/04/2013 02:55 AM, Khoa Pham wrote:
@Alex: thanks for reply
In this IPv4 world, most devices are in NAT, and it only matters if they are symmetric NAT or not.
So if 1 client is behind symmetric NAT, I want to use rtpproxy, otherwise, I do not. According to what I read from kamailio cfg, Kamailio only knows if client is NATed or not, it doesnot know the NAT type
That's correct.
The only way you can infer whether a client is symmetric is through its insertion of the 'rport' parameter into the Via header. However, symmetric clients are not required to insert it; it is only so that a client can request symmetric behaviour from a server. AS RFC 3581 says:
A client, compliant to this specification (clients include UACs and proxies), MAY include an "rport" parameter in the top Via header field value of requests it generates.Certainly, there's nothing saying it must do so.
However, almost all UAs out there are symmetric these days. It's got to be over 95%+. Have you run into one that isn't?
-- Alex
-- Alex Balashov - Principal Evariste Systems LLC 235 E Ponce de Leon Ave Suite 106 Decatur, GA 30030 United States Tel: +1-678-954-0670 Web: http://www.evaristesys.com/, http://www.alexbalashov.com/
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