<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=utf-8">
</head>
<body bgcolor="#FFFFFF" text="#000000">
Hi,<br>
<br>
This is a question for the sake of comprehension, as I actually
solved the problem with a workaround.<br>
<br>
I am trying to get Kamailio working with a third party SIP provider.
The SIP server of this provider pings my Kamailio with OPTIONS
messages. Being located in a sub-network, the SIP messages are
relayed to a router (not a SIP router, just a gateway to the
Internet) which is not listening/sending on port 5060 but on 13377.
When Kamailio answer to OPTIONS, it send back the message to the
router on the port 5060 which is wrong. Here is the topology:<br>
<br>
<font face="Courier New, Courier, monospace"><b>Kamailio</b>
<b>Router</b> <b>SIP Server</b><br>
<i>my.sip.domain 174.37.217.1
197.17.144.4</i><br>
| | ? <--------------------
5060 |<br>
| 5060 <---------------- 13377
| |<br>
| 5060 ----------------−> 5060
| |<br>
| | X |<br>
<br>
<font face="sans-serif">You can see that, Kamailio answers to the
wrong port, but I think this is somewhat coherent since the SIP
message says that the port 5060 is in use. But still, I would
have liked that the correct port was used: </font><br>
<br>
<b>Kamailio</b> <b>Router</b>
<b>SIP Server</b></font><font face="Courier
New, Courier, monospace"><font face="Courier New, Courier,
monospace"><br>
<i>my.sip.domain 174.37.217.1
197.17.144.4<br>
</i></font> | | ?
<-------------------- 5060 |<br>
| 5060 <---------------- 13377
| |<br>
| 5060 ---------------−> 13377
| |<br>
| | ? -------------------->
5060 |</font><br>
<br>
But I do not understand where Kamailio is supposed to find the
correct port. Below are the transport frames, and SIP frames.<br>
<br>
Kamailio receives:<br>
<br>
<font face="Courier New, Courier, monospace">Internet Protocol
Version 4, Src: 174.37.217.1 (174.37.217.1), Dst: 172.16.8.61
(172.16.8.61)<br>
Source: 174.37.217.1 (174.37.217.1)<br>
Destination: 172.16.8.61 (172.16.8.61)<br>
User Datagram Protocol, Src Port: 13377 (13377), Dst Port: sip
(5060)<br>
Source port: 13377 (13377)<br>
Destination port: sip (5060)<br>
<br>
OPTIONS sip:my.sip.domain:5060 SIP/2.0<br>
Via: SIP/2.0/UDP 197.17.144.4:5060;branch=z9hG4bKb9340cb29ba<br>
From: <sip:197.17.144.4>;tag=1797904074<br>
To: <sip:my.sip.domain><br>
Date: Mon, 10 Aug 2015 10:01:51 GMT<br>
Call-ID: <a class="moz-txt-link-abbreviated" href="mailto:c7f38580-5c817680-b94-38512c6@197.17.144.4">c7f38580-5c817680-b94-38512c6@197.17.144.4</a><br>
User-Agent: Cisco-CUCM10.5<br>
CSeq: 101 OPTIONS<br>
Contact: <sip:197.17.144.4:5060><br>
Max-Forwards: 0<br>
Content-Length: 0</font><br>
<br>
...and then sends:<br>
<br>
<font face="Courier New, Courier, monospace">Internet Protocol
Version 4, Src: 172.16.8.61 (172.16.8.61), Dst: 174.37.217.1
(174.37.217.1)<br>
Source: 172.16.8.61 (172.16.8.61)<br>
Destination: 174.37.217.1 (174.37.217.1)<br>
User Datagram Protocol, Src Port: sip (5060), Dst Port: sip (5060)<br>
Source port: sip (5060)<br>
Destination port: sip (5060)<br>
<br>
SIP/2.0 200 OK<br>
Via: SIP/2.0/UDP
197.17.144.4:5060;branch=z9hG4bKb9340cb29ba;received=174.37.217.1<br>
From: <sip:197.17.144.4>;tag=1797904074<br>
To:
<sip:my.sip.domain>;tag=b27e1a1d33761e85846fc98f5f3a7e58.de7a<br>
Call-ID: <a class="moz-txt-link-abbreviated" href="mailto:c7f38580-5c817680-b94-38512c6@197.17.144.4">c7f38580-5c817680-b94-38512c6@197.17.144.4</a><br>
CSeq: 101 OPTIONS<br>
Allow: INVITE,ACK,BYE,CANCEL,INFO,OPTIONS,REFER,SUBSCRIBE,NOTIFY<br>
Accept: */*<br>
Accept-Encoding: <br>
Accept-Language: en<br>
Supported: <br>
Server: kamailio (4.3.1 (x86_64/linux))<br>
Content-Length: 0</font><br>
<br>
We see clearly that the port is wrong here. But in the received SIP
frame, everything suggests that the correct port is 5060, and I do
not think Kamailio will look at the transport frame to send the
response back to the correct port. Am I correct stating this ? Maybe
the Via header should contain a port along with the IP address ?<br>
<br>
I solved the problem by using TCP instead of UDP, as I know that
since the TCP connection is maintained, the port would be correct
(because imposed by the gateway).<br>
<br>
I am sorry if the question does not directly relates to Kamailio,
but any explanation here would be appreciated, as I am a student
trying to learn how all this is working :)<br>
<br>
Cheers,<br>
Jean-Marie.<br>
</body>
</html>