4 Oct
2005
4 Oct
'05
4:50 p.m.
My Nated UA does work fine. I use X-lite. Now I am trying to
understand why it works. It has everything not to work.... I mean,
after the Nated client send an INVITE, the proxy replaces the unvalid
IP of the SDP field and puts its valid IP, so it can be in the middle
of the conversation. But through what I studied in SIP, after a client
send an INVITE, it expects audio to get audio(that is why it sends the
port and ip in the SDP body). Since it is expecting to get audio, how
does the media proxy talks to it, since there isn't any port opened in
the NAT device?
The problem with NAT is that the called part cannot open an audio
channel with the Nated callee because in the SDP body, there is an
invalid IP. In theory, it seems that a media proxy has the same
problem the called has to open an audio channel..... I just couldn't
figure out this...
Thanks,
Felipe
On 10/4/05, Greger V. Teigre <greger(a)teigre.com> wrote:
Mediaproxy cannot force the nated ua to send rtp
(unless it supports active
media, which most don't, AFAIK).
Some UAs (ex. Grandstream old firmware) has an issue where it takes a couple
of seconds before you get sound. However, not getting anything means that
the UA does not have anything to send and that silence suppression is
probably turned on. If you speak using the nated UA, does it start sending
rtp?
g-)
----- Original Message -----
From: "Felipe Louback" <louback(a)gmail.com>
To: "Greger V. Teigre" <greger(a)teigre.com>
Cc: <serusers(a)lists.iptel.org>
Sent: Tuesday, October 04, 2005 04:17 PM
Subject: Re: [Serusers] Theory behind a media proxy and NATed UA
--
Master Student - Electrical Engineering Department
Computer Engineering and Telecommunications Research Group
Universidade Federal de Minas Gerais - Brazil
"For God so loved the world that he gave his one and only Son, that
whoever believes in him shall not perish but have eternal life."
John 3:16
Andy told that after the first UDP packet is
received on the
mediaproxy socket it knows
where to send the packets to. That is the problem.... after the
invite, the NAT-ed UA will wait for traffic, and not send traffic.
Greger, I read Section 3.5 of the document you said, but they dont
explain my doubt. There you can find how the register process is done
and how the NAT problem can be solved. In the document it is said the
proxy put his address in the SDP payload, but how does the media proxy
force the NATed UA to send a UDP packet? By default, the UA is waiting
for audio after it sends an INVITE....
Felipe
On 10/4/05, Greger V. Teigre <greger(a)teigre.com> wrote:
Section 3.5 of the ONsip.org Getting Started
document provides an intro
from
a SIP/SER point of view. Tell me if you miss something :-)
g-)
----- Original Message -----
From: "Felipe Louback" <louback(a)gmail.com>
To: <serusers(a)lists.iptel.org>
Sent: Monday, October 03, 2005 07:27 PM
Subject: [Serusers] Theory behind a media proxy and NATed UA
--
Master Student - Electrical Engineering Department
Computer Engineering and Telecommunications Research Group
Universidade Federal de Minas Gerais - Brazil
"For God so loved the world that he gave his one and only Son, that
whoever believes in him shall not perish but have eternal life."
John 3:16
The problem with NAT is because the IP address of
the SDP body is a
non routeable IP. So how does a media proxy works?
I read that a media proxy put his address at the sdp body and both UA
talks with the media proxy instead of each other. At the time a NAT
user sends an INVITE, there is no corresponding port on the NAT. So
How does a media proxy contact the NATed UA?
Isn't this the same problem the called part will have to contact the
NATed party?
I read a couple of papers about it, but in all of them it is said that
both ends talk to the media proxy and that is all. No explanation
about how things work. I know it works because I am using mediaproxy.
If anyone could point me how this works or where I can find a document
explaining....
Thanks,
Felipe
--
Master Student - Electrical Engineering Department
Computer Engineering and Telecommunications Research Group
Universidade Federal de Minas Gerais - Brazil
"For God so loved the world that he gave his one and only Son, that
whoever believes in him shall not perish but have eternal life."
John 3:16
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