The Session-Timers can be configured on a system-wide, per-user, or per-peer basis. The peruser/ per-peer settings override the global settings. The following new parameters have been added to the sip.conf file. session-timers=["accept", "originate", "refuse"] session-expires=[integer] session-minse=[integer] session-refresher=["uas", "uac"]
The session-timers parameter in sip.conf defines the mode of operation of SIP session-timers feature in Asterisk. The Asterisk can be configured in one of the following three modes:
1. Accept :: In the "accept" mode, the Asterisk server honors session-timers requests made by remote end-points. A remote end-point can request Asterisk to engage session-timers by either sending it an INVITE request with a "Supported: timer" header in it or by responding to Asterisk's INVITE with a 200 OK that contains Session-Expires: header in it. In this mode, the Asterisk server does not request session-timers from remote end-points. This is the default mode. 2. Originate :: In the "originate" mode, the Asterisk server requests the remote end-points to activate session-timers in addition to honoring such requests made by the remote end-pints. In order to get as much protection as possible against hanging SIP channels due to network or end-point failures, Asterisk resends periodic re-INVITEs even if a remote end-point does not support the session-timers feature. 3. Refuse :: In the "refuse" mode, Asterisk acts as if it does not support session- timers for inbound or outbound requests. If a remote end-point requests session-timers in a dialog, then Asterisk ignores that request unless it's noted as a requirement (Require: header), in which case the INVITE is rejected with a 420 Bad Extension response.