[SR-Users] Kamailio as SBC and far end nat

[Daniel-Constantin Mierla]

Hello,

for dialogs (like subscriptions or invites), you have to use record 
routing (see rr module) -- so for initial subscribe/invite you have to 
add record-route header in kamailio, then do loose routing for requests 
within the dialog (like notify) -- the default config file coming with 
kamailio has such logic there.

For registrations, I would suggest the usage of Path extensions, which 
is an ietf rfc, but the registrar server has to support that (avaya sip 
server in your case). Alternative will be to replace the contact in 
register (you can do it for subscribe as well) requests with ip of 
kamailio and a parameter that encodes the nat box ip/port.

A similar mechanism is used by add_contact_alias() function from 
nathelper module to help going through nat -- you can actually use it in 
conjunction with record routing for invites/subscriptions.

Cheers,
Daniel


On 7/19/12 1:12 PM, Martin Schiøtz wrote:
> Hi
>
> I'm trying to configure kamailio version 3.3.0 to be a Session Border
> Controller which only purpose is to handle far-end-nat.
>
> On the far end site I have a SIP client with IP '192.168.1.2' which is
> NAT'ed to IP 'zz.zz.85.230'. The SIP ALG is disabled on the NAT
> firewall. The SIP client is communicating with the kamailio server and
> the Kamailio server is forwarding every thing to an Avaya SIP server
> 'xx.xx.173.15' and vice versa. The kamilio is konfigured to do this
> stateless.
>
> The REGISTER and SUBSCRIBE part works fine. The kamailio is using the
> 'Via:' field and I also needed to do subst on the 'Contact:' field in
> order for our SIP server to communicate back to the kamailio. But when
> I get to the NOTIFY packet from the SIP server to the kamailio there
> is no 'Via:' field or any other information about the SIP clients
> IP/port and the Kamailio just sends back 'SIP/2.0 404 Not here.' to
> the SIP server.
>
> I guess that this can not be solved with a statless kamailio?
> I guess that I need some kind of state table in the kamailio - is that
> possible without doing REGISTER directly with the kamailio?
> Any other good ideas are welcome?
>
> Cheers,
> Martin
>
>
> Tell me if need more info the issue?
> -----
> #
> T xx.xx.173.15:38059 -> yy.yy.159.211:5060 [AP]
> NOTIFY sip:2001012 at yy.yy.159.211:5060;transport=TCP SIP/2.0.
> Call-ID: NjQ5ZDNlYzRjOWFjMzMzN2JlYzAwMTg4ODYwZTJlYWY..
> From: "2001012"
> <sip:2001012 at bsosip.domain.dk>;tag=-667195155*1*016asm-callprocessing.sar229435981~1342570131099~1170998434~1.
> To: "2001012" <sip:2001012 at bsosip.domain.dk>;tag=7ca0af7d.
> CSeq: 3 NOTIFY.
> Contact: <sip:xx.xx.173.14:15060>.
> Via: SIP/2.0/TCP
> xx.xx.173.15;branch=z9hG4bK4DEAAD0E478B838008189457-AP;ft=xx.xx.173.15~13c4.
> Via: SIP/2.0/UDP xx.xx.173.14:15070;branch=z9hG4bK4DEAAD0E478B838008189457.
> Via: SIP/2.0/TCP xx.xx.173.14:15070;branch=z9hG4bK4DEAAD0E478B838018189455.
> Event: message-summary.
> Content-Type: application/simple-message-summary.
> Content-Length: 69.
> Subscription-State: active;expires=299.
> Max-Forwards: 68.
> User-Agent:  AVAYA-SM-6.1.4.0.614005.
> .
> Messages-Waiting: no.
> Message-Account: sip:2001012 at bsosip.domain.dk.
>
> ##
> T yy.yy.159.211:5060 -> xx.xx.173.15:38059 [AP]
> SIP/2.0 404 Not here.
> Call-ID: NjQ5ZDNlYzRjOWFjMzMzN2JlYzAwMTg4ODYwZTJlYWY..
> From: "2001012"
> <sip:2001012 at bsosip.domain.dk>;tag=-667195155*1*016asm-callprocessing.sar229435981~1342570131099~1170998434~1.
> To: "2001012" <sip:2001012 at bsosip.domain.dk>;tag=7ca0af7d.
> CSeq: 3 NOTIFY.
> Via: SIP/2.0/TCP
> xx.xx.173.15;branch=z9hG4bK4DEAAD0E478B838008189457-AP;ft=xx.xx.173.15~13c4;rport=38059.
> Via: SIP/2.0/UDP xx.xx.173.14:15070;branch=z9hG4bK4DEAAD0E478B838008189457.
> Via: SIP/2.0/TCP xx.xx.173.14:15070;branch=z9hG4bK4DEAAD0E478B838018189455.
> Server: kamailio (3.3.0 (i386/linux)).
> Content-Length: 0.
> .
>
> #
> T xx.xx.173.15:38059 -> yy.yy.159.211:5060 [A]
> ......
> #
> T yy.yy.159.211:5060 -> xx.xx.173.15:38059 [AP]
> SIP/2.0 404 Not here.
> Call-ID: NjQ5ZDNlYzRjOWFjMzMzN2JlYzAwMTg4ODYwZTJlYWY..
> From: "2001012"
> <sip:2001012 at bsosip.domain.dk>;tag=-667195155*1*016asm-callprocessing.sar229435981~1342570131099~1170998434~1.
> To: "2001012" <sip:2001012 at bsosip.domain.dk>;tag=7ca0af7d.
> CSeq: 3 NOTIFY.
> Via: SIP/2.0/TCP
> xx.xx.173.15;rport=38059;branch=z9hG4bK4DEAAD0E478B838008189457-AP;ft=xx.xx.173.15~13c4.
> Via: SIP/2.0/UDP xx.xx.173.14:15070;branch=z9hG4bK4DEAAD0E478B838008189457.
> Via: SIP/2.0/TCP xx.xx.173.14:15070;branch=z9hG4bK4DEAAD0E478B838018189455.
> Server: kamailio (3.3.0 (i386/linux)).
> Content-Length: 0.
> -----
>
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-- 
Daniel-Constantin Mierla - http://www.asipto.com
http://twitter.com/#!/miconda - http://www.linkedin.com/in/miconda
Kamailio Advanced Training, Seattle, USA, Sep 23-26, 2012 - http://asipto.com/u/katu
Kamailio Practical Workshop, Netherlands, Sep 10-12, 2012 - http://asipto.com/u/kpw