Hello Klaus,

We are using Kamailio V1.4 with TCP/TLS.

The Kamailio is configured the TCP lifetime to the expire value of the REGISTER by using the tcp_persistent_flag parameter of Kamailio's registrar module. Note: The SIP proxy should not close the TCP connection as it is not capable of opening a new one.

Kamailio tries to open a TLS connection to the client. The Kamailio should use the existing TCP/TLS connection that was established by the client during registration.

We are applying NAT traversal techniques to instruct Kamailio to reuse the established TCP/TLS connection. Example: for each register call fix_nated_register(). For every other request and response call fix_nated_contact().

I have got one SIP phone registered via TLS to kamailio-1.4.X version with Expires = 3600.

SIP Phone1: connected via ip1:port1 and Expires = 3600.

Example: After 15 minutes the TLS connection is closed.

The SIP Phone opens a new TLS connection and registers via TLS to Kamailio. Thus, we have the following records on the Registrar Server (Kamailio):

SIP Phone1: connected via ip1:port1 and Expires = 2700 [3600 – (15 min * 60 s) = 2700].

SIP Phone1: connected via ip1:port2 and Expires = 3600.

Is this the desirable behavior? Shouldn’t the Kamailio (Registrar Server) delete the below registry after closing the TLS connectio?  

SIP Phone1: connected via ip1:port1 and Expires = 2700 [3600 – (15 min * 60 s) = 2700].

Best regards!

Edson G. Leme