[Serusers] NAT traversal of the BYE transaction

[Andrea Bondavalli]

Hi all,

I am experiencing a problem related to the NAT traversal of the BYE transaction.
Some of my UAs are natted and I am using a mediaproxy (SER + mediaproxy module)
between such UAs and my SIP proxy (registar/location) in order to overcome the NAT problem.
Everything is working fine, but the Via field of the BYE transaction
seems to forget about the port number of the interface from which
the BYE was received.

As you can see from the following traces the Via field 
(Via: SIP/2.0/UDP 192.168.0.10:5060;received=213.92.1.143;branch=z9hG4bK-fdee73bb)
of the BYE sent by 213.92.1.178:5060 to 213.92.1.197:5060 doesn't report
the port number of the incoming interface (rport=1029).

The final result is that the answer (200 OK) is sent back to
the wrong port number (5060 instead of 1029).


U 213.92.1.143:1029 -> 213.92.1.178:5060
BYE sip:bonda at 213.92.1.230 SIP/2.0
Via: SIP/2.0/UDP 192.168.0.10:5060;branch=z9hG4bK-fdee73bb
From: <sip:8001 at inet.it>;tag=5d62d7eb80acc3c7
To: "Andrea Bondavalli" <sip:bonda at inet.it>;tag=5fae3692dc76fd5a
Call-ID: bcd4cb1e47de41e1 at 213.92.1.230
CSeq: 101 BYE
Max-Forwards: 70
Route: <sip:213.92.1.178;ftag=5fae3692dc76fd5a;lr>, <sip:213.92.1.197;ftag=5fae3692dc76fd5a;lr=on>
User-Agent: Sipura/SPA2000-2.0.9(d)
Content-Length: 0
#
U 213.92.1.178:5060 -> 213.92.1.197:5060
BYE sip:bonda at 213.92.1.230 SIP/2.0
Record-Route: <sip:213.92.1.178;ftag=5d62d7eb80acc3c7;lr>
Via: SIP/2.0/UDP 213.92.1.178;branch=z9hG4bK51f1.91462923.0
Via: SIP/2.0/UDP 192.168.0.10:5060;received=213.92.1.143;branch=z9hG4bK-fdee73bb
From: <sip:8001 at inet.it>;tag=5d62d7eb80acc3c7
To: "Andrea Bondavalli" <sip:bonda at inet.it>;tag=5fae3692dc76fd5a
Call-ID: bcd4cb1e47de41e1 at 213.92.1.230
CSeq: 101 BYE
Max-Forwards: 69
Route: <sip:213.92.1.197;ftag=5fae3692dc76fd5a;lr=on>
User-Agent: Sipura/SPA2000-2.0.9(d)
Content-Length: 0
P-hint: mediaproxy
#
U 213.92.1.197:5060 -> 213.92.1.178:5060
SIP/2.0 200 OK
Via: SIP/2.0/UDP 213.92.1.178;branch=z9hG4bK51f1.91462923.0
Via: SIP/2.0/UDP 192.168.0.10:5060;received=213.92.1.143;branch=z9hG4bK-fdee73bb
Record-Route: <sip:213.92.1.197;ftag=5d62d7eb80acc3c7;lr=on>
Record-Route: <sip:213.92.1.178;ftag=5d62d7eb80acc3c7;lr>
From: <sip:8001 at inet.it>;tag=5d62d7eb80acc3c7
To: "Andrea Bondavalli" <sip:bonda at inet.it>;tag=5fae3692dc76fd5a
Call-ID: bcd4cb1e47de41e1 at 213.92.1.230
CSeq: 101 BYE
User-Agent: Grandstream BT100 1.0.5.6
Contact: <sip:bonda at 213.92.1.230>
Allow:  INVITE,ACK,CANCEL,BYE,NOTIFY,REFER,OPTIONS,INFO,SUBSCRIBE
Content-Length: 0
#
U 213.92.1.178:5060 -> 213.92.1.143:5060
SIP/2.0 200 OK
Via: SIP/2.0/UDP 192.168.0.10:5060;received=213.92.1.143;branch=z9hG4bK-fdee73bb
Record-Route: <sip:213.92.1.197;ftag=5d62d7eb80acc3c7;lr=on>
Record-Route: <sip:213.92.1.178;ftag=5d62d7eb80acc3c7;lr>
From:<sip:8001 at inet.it>;tag=5d62d7eb80acc3c7
To: "Andrea Bondavalli" <sip:bonda at inet.it>;tag=5fae3692dc76fd5a
Call-ID: bcd4cb1e47de41e1 at 213.92.1.230..CSeq: 101 BYE
User-Agent: Grandstream BT100 1.0.5.6
Contact: <sip:bonda at 213.92.1.230>
Allow: INVITE,ACK,CANCEL,BYE,NOTIFY,REFER,OPTIONS,INFO,SUBSCRIBE
Content-Length: 0

Can you help me on this issue ?

Please consider that I am using the latest SER code from CVS 
(for all the proxy server on the network).

Thank you a lot in advance,

Andrea Bondavalli 
I.NET S.p.A. - Research & Development 
mailto:a.bondavalli at inet.it