New subject: [OpenSER-Users] NAT question

8 Aug 2007

Hi Bogdan,

I understand that 200 OK should not be fixed by proxyA. Maybe what I
don't understand is what nat_uac_test("2") does and when to use it. 

Following is an example where 
clientA = demo1(a)altecnet.gr
clientB = sip_test_1(a)i-call.gr
proxyA = 213.5.43.4
proxyB = 213.5.43.134

When proxyA goes in the onreply_route for the 200 OK, nat_uac_test("23")
returns true (I guess because of the "2" flag) and proxyA fixes the
contact again which is wrong. So, would it be safe to use
nat_uac_test("23") for the requests and nat_uac_test("21") for the
replies? I am afraid this would break the simple case with 2 NATed
clients and only one proxy:
clientA ------> proxyA ------> clientC

thank you for your help

George

#
U 2007/08/08 10:11:34.233164 213.5.43.134:5060 -> 213.5.43.4:5060
SIP/2.0 200 Ok.
Via: SIP/2.0/UDP 213.5.43.4;rport=5060;branch=z9hG4bK322.eea78413.0.
Via: SIP/2.0/UDP
192.168.1.39;received=213.5.17.226;rport=5060;branch=z9hG4bKc0a801270000
002c46b96cbb000000a000000087.
Record-Route: <sip:213.5.43.134;lr=on;ftag=109517115931019>.
Record-Route: <sip:213.5.43.4;lr=on;ftag=109517115931019>.
From: "222" <sip:demo1@altecnet.gr>;tag=109517115931019.
To: <sip:sip_test_1@i-call.gr>;tag=0r8u9ziv3g.
Call-ID: 000029DD-5407-0000-3452-00006A3B0000(a)192.168.1.39.
CSeq: 2 INVITE.
Contact: <sip:sip_test_1@213.5.17.236:5060;transport=udp;line=9yt55o5b>.
User-Agent: snom190-3.56w.
Allow: INVITE, ACK, CANCEL, BYE, REFER, OPTIONS, NOTIFY, SUBSCRIBE,
PRACK, MESSAGE, INFO.
Allow-Events: talk, hold, refer.
Supported: timer, 100rel, replaces.
Content-Type: application/sdp.
Content-Length: 208.
.
v=0.
o=root 1592588598 1592588598 IN IP4 213.5.17.236.
s=call.
c=IN IP4 213.5.17.236.
t=0 0.
m=audio 10116 RTP/AVP 8 101.
a=rtpmap:8 pcma/8000.
a=rtpmap:101 telephone-event/8000.
a=fmtp:101 0-15.
a=sendrecv.

#
U 2007/08/08 10:11:34.234013 213.5.43.4:5060 -> 213.5.17.226:5060
SIP/2.0 200 Ok.
Via: SIP/2.0/UDP
192.168.1.39;received=213.5.17.226;rport=5060;branch=z9hG4bKc0a801270000
002c46b96cbb000000a000000087.
Record-Route: <sip:213.5.43.134;lr=on;ftag=109517115931019>.
Record-Route: <sip:213.5.43.4;lr=on;ftag=109517115931019>.
From: "222" <sip:demo1@altecnet.gr>;tag=109517115931019.
To: <sip:sip_test_1@i-call.gr>;tag=0r8u9ziv3g.
Call-ID: 000029DD-5407-0000-3452-00006A3B0000(a)192.168.1.39.
CSeq: 2 INVITE.
Contact: <sip:sip_test_1@213.5.43.134:5060;transport=udp;line=9yt55o5b>.
User-Agent: snom190-3.56w.
Allow: INVITE, ACK, CANCEL, BYE, REFER, OPTIONS, NOTIFY, SUBSCRIBE,
PRACK, MESSAGE, INFO.
Allow-Events: talk, hold, refer.
Supported: timer, 100rel, replaces.
Content-Type: application/sdp.
Content-Length: 208.
P-hint: NATed reply.
.
v=0.
o=root 1592588598 1592588598 IN IP4 213.5.17.236.
s=call.
c=IN IP4 213.5.17.236.
t=0 0.
m=audio 10116 RTP/AVP 8 101.
a=rtpmap:8 pcma/8000.
a=rtpmap:101 telephone-event/8000.
a=fmtp:101 0-15.
a=sendrecv.

...
  -----Original Message-----
 From: Bogdan-Andrei Iancu [mailto:bogdan@voice-system.ro] 
 Sent: Wednesday, August 08, 2007 9:50 AM
 To: Papadopoulos Georgios
 Cc: users(a)openser.org
 Subject: Re: [OpenSER-Users] NAT question

 Hi George,

 each proxy should fix what it detects. ProxyA will take care 
 of the traffic related to A (since it detects A as NATed) and 
 ProxyB should take care of traffic for B (as it sees B as 
 nated). So, the 200 OK must be fixed only by proxyB.

 Regards,
 bogdan

 Papadopoulos Georgios wrote:
  Hello all,

 I need some advice from all you NAT experts. Assume that we   have two 
  OpenSER proxies serving two different domains and
they both use 
 nathelper. Also assume that their configuration is   identical and looks 
  roughly like:

 route {
 ...
         record_route();

         if (nat_uac_test("23")) {
                 if (method!="REGISTER" &&
 !is_present_hf("Record-Route")) {
                     fix_nated_contact();
                 }
         }

         t_on_reply("1");
 }

 onreply_route[1] {
         if (nat_uac_test("23")) {
                 fix_nated_contact();
         };
 }
 clientA and clientB are both behind NAT. clientA@domainA 
 <mailto:clientA@domainA> sends an INVITE to clientB@domainB 
 <mailto:clientB@domainB> through proxyA:

 clientA@domainA <mailto:clientA@domainA>  -----> ProxyA   ----->
ProxyB
  ------> clientB@domainB
<mailto:clientB@domainB>

 ProxyA detects that clientA is behind NAT and fixes the contact. 
 ProxyB finds the Record-Route header, so it does not fix   the contact. 
  My question is about how to handle the 200 OK.
With this   configuration 
  both proxies detect that clientB is behind NAT
and the contact gets 
 fixed twice. Is there a way to avoid this?

 thank you

 George

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RE: [OpenSER-Users] NAT question