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

[Khoa Pham]

@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 at 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 at aol.com
>
>
> -----Original Message-----
> From: Alex Balashov <abalashov at evaristesys.com>
> To: sr-users <sr-users at 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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>


-- 
Khoa Pham
HCMC University of Science
Faculty of Information Technology
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