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List: sr-users
Subject: Re: [SR-Users] Need help understanding/separating signaling from media
From: Grant Bagdasarian <GB () cm ! nl>
Date: 2013-02-26 15:24:00
Message-ID: FB7D97A214987F458242ACBDF876140738C07870B6 () clubvirtual40 ! ClubMessage ! local
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Alex wrote:
The Kamailio 'rtpproxy' module goes out to the rtpproxy service[1] and asks=
it to engage the call, saying: "Can you please allocate and provide me wit=
h a pair of ports for each end of this call?" The rtpproxy process answers=
, and Kamailio then writes the IP and ports provided by rtpproxy into the S=
DP of both the requests and replies involved in setting up the call.
What if both endpoints are on different networks?
Endpoint 1 -------------- Kamailio -------------- Endpoint 2
| | =
|
| | =
|
| | =
|
+-------------------- RTPProxy -----------------+
Please correct me if I'm wrong:
1) Endpoint 1 (10.0.0.1) sends an INVITE containing the offer to Kamai=
lio (10.0.0.2).
2) Kamailio asks RTPProxy to engage the call and allocate two ports.
3) Kamailio writes the IP and port of the RTPProxy (10.0.0.3:1000) in =
the SDP of the 100 Trying and replies back to Endpoint 1.
4) Kamailio (20.0.0.2) now sends the INVITE with offer to Endpoint 2 (=
20.0.0.1), but with modified SDP (20.0.0.3:1001).
5) .....
6) Endpoint 1 sends its media to 10.0.0.3:1000 and Endpoint 2 sends it=
s media to 20.0.0.3:1001.
7) RTPProxy bridges both ends.
What makes it so difficult for me to understand is that both Kamailio and R=
TPProxy are connected to two different networks. A call between endpoint 1 =
and 2 must be bridged by Kamailio and RTPProxy.
How does Kamailio know it has to tell RTPProxy to engage a call on network =
10.0.0.0 and 20.0.0.0 and allocate two ports, 1 for each network?
Regards,
Grant
-----Original Message-----
From: sr-users-bounces@lists.sip-router.org [mailto:sr-users-bounces@lists.=
sip-router.org] On Behalf Of Alex Balashov
Sent: Monday, January 28, 2013 5:11 PM
To: sr-users@lists.sip-router.org
Subject: Re: [SR-Users] Need help understanding/separating signaling from m=
edia
Hi Grant,
On 01/28/2013 11:03 AM, Grant Bagdasarian wrote:
> I think that the RTP Proxy module does precisely this, but what I
> still don't understand is how the rtp stream is passed between these
> two agents for each call.
The Kamailio 'rtpproxy' module goes out to the rtpproxy service[1] and asks=
it to engage the call, saying: "Can you please allocate and provide me wit=
h a pair of ports for each end of this call?" The rtpproxy process answers=
, and Kamailio then writes the IP and ports provided by rtpproxy into the S=
DP of both the requests and replies involved in setting up the call.
The result is that as far as both UAs are concerned, rtpproxy is their endp=
oint, and they will send media to it. Kamailio instructs rtpproxy to bridg=
e both streams.
When the call is torn down, Kamailio tells rtpproxy to disengage and deallo=
cate the bridge mapping for those streams.
-- Alex
[1] Which may be running on the same host, or may be running on another hos=
t, in a distributed fashion. Kamailio talks to rtpproxy through rtpproxy's=
UDP control socket, and more than one rtpproxy may be used, both for failo=
ver and round-robin load distribution. This is readily baked into the rtpp=
roxy module.
--
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/
_______________________________________________
SIP Express Router (SER) and Kamailio (OpenSER) - sr-users mailing list
sr-users@lists.sip-router.org<mailto:sr-users@lists.sip-router.org>
http://lists.sip-router.org/cgi-bin/mailman/listinfo/sr-users
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class=WordSection1><p class=MsoPlainText><i>Alex wrote: <o:p></o:p></i></p><p \
class=MsoPlainText><i>The Kamailio 'rtpproxy' module goes out to the rtpproxy \
service[1] and asks it to engage the call, saying: "Can you please allocate and \
provide me with a pair of ports for each end of this call?" The rtpproxy \
process answers, and Kamailio then writes the IP and ports provided by rtpproxy into \
the SDP of both the requests and replies involved in setting up the \
call.<o:p></o:p></i></p><p class=MsoPlainText><o:p> </o:p></p><p \
class=MsoPlainText>What if both endpoints are on different networks?<o:p></o:p></p><p \
class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>Endpoint 1 \
-------------- Kamailio -------------- Endpoint 2<o:p></o:p></p><p \
class=MsoPlainText> \
| & \
nbsp; \
| & \
nbsp; \
|<o:p></o:p></p><p class=MsoPlainText> \
| & \
nbsp; \
| \
|<o:p></o:p></p><p \
class=MsoPlainText> \
| & \
nbsp; \
| & \
nbsp; \
|<o:p></o:p></p><p class=MsoPlainText> \
+-------------------- RTPProxy -----------------+<o:p></o:p></p><p \
class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>Please correct me if \
I’m wrong:<o:p></o:p></p><p class=MsoPlainText \
style='margin-left:.5in;text-indent:-.25in;mso-list:l0 level1 lfo1'><![if \
!supportLists]><span style='mso-list:Ignore'>1)<span style='font:7.0pt "Times New \
Roman"'> </span></span><![endif]>Endpoint 1 (10.0.0.1) \
sends an INVITE containing the offer to Kamailio (10.0.0.2).<o:p></o:p></p><p \
class=MsoPlainText style='margin-left:.5in;text-indent:-.25in;mso-list:l0 level1 \
lfo1'><![if !supportLists]><span style='mso-list:Ignore'>2)<span style='font:7.0pt \
"Times New Roman"'> </span></span><![endif]>Kamailio \
asks RTPProxy to engage the call and allocate two ports.<o:p></o:p></p><p \
class=MsoPlainText style='margin-left:.5in;text-indent:-.25in;mso-list:l0 level1 \
lfo1'><![if !supportLists]><span style='mso-list:Ignore'>3)<span style='font:7.0pt \
"Times New Roman"'> </span></span><![endif]>Kamailio \
writes the IP and port of the RTPProxy (10.0.0.3:1000) in the SDP of the 100 Trying \
and replies back to Endpoint 1.<o:p></o:p></p><p class=MsoPlainText \
style='margin-left:.5in;text-indent:-.25in;mso-list:l0 level1 lfo1'><![if \
!supportLists]><span style='mso-list:Ignore'>4)<span style='font:7.0pt "Times New \
Roman"'> </span></span><![endif]>Kamailio (20.0.0.2) \
now sends the INVITE with offer to Endpoint 2 (20.0.0.1), but with modified SDP \
(20.0.0.3:1001).<o:p></o:p></p><p class=MsoPlainText \
style='margin-left:.5in;text-indent:-.25in;mso-list:l0 level1 lfo1'><![if \
!supportLists]><span style='mso-list:Ignore'>5)<span style='font:7.0pt "Times New \
Roman"'> \
</span></span><![endif]>…..<o:p></o:p></p><p class=MsoPlainText \
style='margin-left:.5in;text-indent:-.25in;mso-list:l0 level1 lfo1'><![if \
!supportLists]><span style='mso-list:Ignore'>6)<span style='font:7.0pt "Times New \
Roman"'> </span></span><![endif]>Endpoint 1 sends its \
media to 10.0.0.3:1000 and Endpoint 2 sends its media to \
20.0.0.3:1001.<o:p></o:p></p><p class=MsoPlainText \
style='margin-left:.5in;text-indent:-.25in;mso-list:l0 level1 lfo1'><![if \
!supportLists]><span style='mso-list:Ignore'>7)<span style='font:7.0pt "Times New \
Roman"'> </span></span><![endif]>RTPProxy bridges both \
ends.<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p \
class=MsoPlainText>What makes it so difficult for me to understand is that both \
Kamailio and RTPProxy are connected to two different networks. A call between \
endpoint 1 and 2 must be bridged by Kamailio and RTPProxy.<o:p></o:p></p><p \
class=MsoPlainText>How does Kamailio know it has to tell RTPProxy to engage a call on \
network 10.0.0.0 and 20.0.0.0 and allocate two ports, 1 for each \
network?<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p \
class=MsoPlainText>Regards,<o:p></o:p></p><p \
class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>Grant<o:p></o:p></p><p \
class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>-----Original \
Message-----<br>From: sr-users-bounces@lists.sip-router.org \
[mailto:sr-users-bounces@lists.sip-router.org] On Behalf Of Alex Balashov<br>Sent: \
Monday, January 28, 2013 5:11 PM<br>To: sr-users@lists.sip-router.org<br>Subject: Re: \
[SR-Users] Need help understanding/separating signaling from media</p><p \
class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>Hi \
Grant,<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p \
class=MsoPlainText>On 01/28/2013 11:03 AM, Grant Bagdasarian wrote:<o:p></o:p></p><p \
class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>> I think that the \
RTP Proxy module does precisely this, but what I <o:p></o:p></p><p \
class=MsoPlainText>> still don’t understand is how the rtp stream is passed \
between these <o:p></o:p></p><p class=MsoPlainText>> two agents for each \
call.<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p \
class=MsoPlainText>The Kamailio 'rtpproxy' module goes out to the rtpproxy service[1] \
and asks it to engage the call, saying: "Can you please allocate and provide me \
with a pair of ports for each end of this call?" The rtpproxy process \
answers, and Kamailio then writes the IP and ports provided by rtpproxy into the SDP \
of both the requests and replies involved in setting up the call.<o:p></o:p></p><p \
class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>The result is that as \
far as both UAs are concerned, rtpproxy is their endpoint, and they will send media \
to it. Kamailio instructs rtpproxy to bridge both streams.<o:p></o:p></p><p \
class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>When the call is torn \
down, Kamailio tells rtpproxy to disengage and deallocate the bridge mapping for \
those streams.<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p \
class=MsoPlainText>-- Alex<o:p></o:p></p><p \
class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>[1] Which may be \
running on the same host, or may be running on another host, in a distributed \
fashion. Kamailio talks to rtpproxy through rtpproxy's UDP control socket, and \
more than one rtpproxy may be used, both for failover and round-robin load \
distribution. This is readily baked into the rtpproxy module.<o:p></o:p></p><p \
class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>-- <o:p></o:p></p><p \
class=MsoPlainText>Alex Balashov - Principal<o:p></o:p></p><p \
class=MsoPlainText>Evariste Systems LLC<o:p></o:p></p><p class=MsoPlainText>235 E \
Ponce de Leon Ave<o:p></o:p></p><p class=MsoPlainText>Suite 106<o:p></o:p></p><p \
class=MsoPlainText>Decatur, GA 30030<o:p></o:p></p><p class=MsoPlainText>United \
States<o:p></o:p></p><p class=MsoPlainText>Tel: +1-678-954-0670<o:p></o:p></p><p \
class=MsoPlainText>Web: <a href="http://www.evaristesys.com/"><span \
style='color:windowtext;text-decoration:none'>http://www.evaristesys.com/</span></a>, \
<a href="http://www.alexbalashov.com/"><span \
style='color:windowtext;text-decoration:none'>http://www.alexbalashov.com/</span></a><o:p></o:p></p><p \
class=MsoPlainText><o:p> </o:p></p><p \
class=MsoPlainText>_______________________________________________<o:p></o:p></p><p \
class=MsoPlainText>SIP Express Router (SER) and Kamailio (OpenSER) - sr-users mailing \
list<o:p></o:p></p><p class=MsoPlainText><a \
href="mailto:sr-users@lists.sip-router.org"><span \
style='color:windowtext;text-decoration:none'>sr-users@lists.sip-router.org</span></a><o:p></o:p></p><p \
class=MsoPlainText><a \
href="http://lists.sip-router.org/cgi-bin/mailman/listinfo/sr-users"><span \
style='color:windowtext;text-decoration:none'>http://lists.sip-router.org/cgi-bin/mailman/listinfo/sr-users</span></a><o:p></o:p></p></div></body></html>
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