SIP session timers are used to make sure that a session (dialog) is still alive, even though there may have been a long time since the last in-dialog message. If the other end is not responding, the dialog will be hung up automatically. SIP session timers need to be supported by all end points for it to work. It's a SIP extension, standardized by the IETF. The sst module provides a way to update the dialog expiry timer based on the SIP INVITE/200 OK Session-Expires header value. You can use the sst module in a Kamailio proxy to allow freeing of local resources of dead calls. You can also use the sst module to validate the MIN_SE header value and reply to any request with a "422 - Session Timer Too Small" if the value is too small for your Kamailio configuration.
Copyright © 2006 SOMA Networks, Inc.
