Chapter 18: Session Timer Service
The Session Timer for the Session Initiation Protocol (SIP) feature (RFC4028) allows the Avaya
1200 Series IP Deskphone to support a keep-alive mechanism for SIP sessions. SIP sessions are
periodically refreshed by UPDATE requests (or re-INVITES for the IP Deskphones that do not
support UPDATE). The UPDATE requests are sent during an active call to allow endpoints or
proxies to determine the status of a SIP session.
The Session Timer Service contains the following elements:
• Session-Expires header
• Min-SE header
• response message (422—Session interval too small)
• tag (timer) for existing headers
The SIP IP Deskphone generates, processes and handles the SIP messages that include the
preceding elements.
Session-Expires header
The SIP Session-Expires header delivers the Session-Expires interval and provides information
about the entity performing the refreshes. A value of "uac" indicates that the originating endpoint
performs the refresh; a value of "uas" indicates that the terminating endpoint performs the refresh.
The session interval is the maximum amount of time that occurs between session refresh requests
in a dialog box before the session times-out. The minimum for this field is 90 seconds; the
recommended value is 1800 seconds (30 minutes).
Min-SE header
The Min-SE header indicates the minimum value for the session expiration in units of delta-seconds.
When a call is made, the presence of the Min-SE header informs the terminating endpoint, and
proxies, of the minimum value that the originating endpoints accept for the session timer duration in
units of delta seconds. When present in a 422 response, the Min-SE header indicates the minimum
session value the terminating endpoint accepts.
When present in a request or response, the value of the Min-SE header is 90 seconds or more. If
the Min-SE header is not present, the default value is 90 seconds. It is a configurable parameter.
March 2015 SIP Software for Avaya 1200 Series IP Deskphones-Administration 215
Comments? infodev@avaya.com
To Next Page
Loading...
