[SR-Users] Client Registration and Call over Kamailio

serkan celik srkancelik at gmail.com
Fri Nov 9 14:30:00 CET 2018


Hi all,

I am using Kamailio as a proxy in front of a 3rd part Open IMS (Not IMS
modules in kamailio).
I have defined Kamailio as an outbound proxy in Soft clients(I have
configured IMS users info in Soft Clients). When I send register from
client to IMS, Register message is sent to IMS over Kamailio. Kamailio
forwards this received Register to the 3rd party IMS. Finally the client is
registered into IMS over Kamailio. However when I try to make a call from
registered users (both registered over Kamailio), IMS sends 403 Forbidden -
"Not Registered! You must register first with a S-CSCF" to Kamailio.
When I debugged the issue I found the reason why IMS sends 403. When IMS
receives an Invite message from Kamailio it checks whether source IP which
Invite is sent registered or not. As I make registration over Kamailio
without changing contact header, IMS registers the user with the contact IP
(which is the client IP).
So to make a call from Soft client (IMS users) over Kamailio I also need to
register Kamailio source IP as well.To deal with the issue I have changed
the contact address of Register message coming from Soft client with
Kamailio IP  on Kamailio. Then IMS registered Kamailio IP as a contact when
registering IMS user. But this time when I make a call from Soft client
over Kamailio, IMS sends Termination Invite to Kamailio. So to finalize the
call Kamailio has to route this termination Invite to the terminating IMS
user .
Is there any better approach to overcome this issue. Which is the better
approach to use Kamailio in front of IMS. I want to both register and make
a call from Soft clients over Kamailio to the IMS.

Regards,
Serkan CELIK
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