[Serusers] interesting 2 way SIP signalling problem

[İlker Aktuna (Koç.net)]

Hi,
 
do you have any comments on this ?
 
Thanks,
ilker


________________________________

From: serusers-bounces at lists.iptel.org [mailto:serusers-bounces at lists.iptel.org] On Behalf Of İlker Aktuna (Koç.net)
Sent: Monday, April 09, 2007 11:50 AM
To: Greger Viken Teigre
Cc: serusers at iptel.org
Subject: RE: [Serusers] interesting 2 way SIP signalling problem


The client does not have STUN support. (I am not sure; because there is no field to enter stun server address. However it may have an internal STUN)
Actually the client is the "internet calling" feature of new Windows Mobile 6.0.
 
I am also nearly sure that there is no ALG in front of the UA. Plus, I am using 5061 on the SIP server as UDP port. So most of the ALG mechanisms do not mess with my sip messages.
 
I believe this is a misconfiguration issue. But I don't know how to troubleshoot it.
 
Any help on the nat configuration would be wonderful.
 
Thanks,
ilker


________________________________

From: Greger Viken Teigre [mailto:greger at teigre.com] 
Sent: Monday, April 09, 2007 11:25 AM
To: İlker Aktuna (Koç.net)
Cc: serusers at iptel.org
Subject: Re: [Serusers] interesting 2 way SIP signalling problem


Most likely the invite is not detected as NATed by your config and force_rport and fix_nated_contact (which will solve your problem) are not called.
If you use stun, it behaves badly. If not, you have an ALG in front of the UA.
g-)

------- Original message -------
From: İlker Aktuna (Koç.net) <ilkera at koc.net>
Sent: 9.4.'07,  9:32

> Hi,
> 
> I have a working configuration on my SER server. Most of the users can make calls (both way incoming and outgoing) with no problem.
> However, I have some clients that can't make calls. 
> When I analyze these by ngrep and/or tcpdump, I see that the SER server does not reply the packet on the correct port.
> 
> For example, I have a testing client which is behind NAT.
> The client sends INVITE message from UDP port 3023 to port 5061 of my SER.
> (cseq number is 1)
> SER exchanges the message with the uplink sip gateway and when it receives a "OK" response it forwards this message to the client's NAT IP address BUT on a different port (14640) with correct cseq number (1)
> 
> Of course, this new port is not open on the NAT router and it does not reach the client.
> 
> I see that the first INVITE message has Contact field with internal IP address of the client and the port number as 14640.
> So the SER server sends the returning message to the external IP address with internal port number.
> 
> How can I fix this issue ?
> 
> I can send the configuration of my SER server if that would help to find the problem.

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