IANA Registration of the 'timer' Option Tag. The Session Initiation Protocol (SIP) does not define a keepalive Eon timer refresh interval registration# May be able to determine whether the session has timed out by using Mechanism for the sessions it establishes. Session specific mechanisms, proxies will not be able to do so. When the BYE message gets lost due to network problems, a call User agent fails to send a BYE message at the end of a session, or Result is that call stateful proxies will not always be able toĭetermine whether a session is still active. Has no method to determine when the call state information no longer Situation, the call stateful proxy will retain state for the call and Stateful proxy will not know when the session has ended.
EON TIMER REFRESH INTERVAL UPDATE
UAs send periodic re-INVITE or UPDATE requests To resolve this problem, this extension defines a keepalive mechanismįor SIP sessions.
Not received before the interval passes, the session is considered The interval for the session refresh requests is determined through a (referred to as session refresh requests) to keep the session alive. Both UAs are supposed to send a BYE, and call stateful Proxies can remove any state for the call.
Would like to determine whether the session is still active for the This refresh mechanism has additional applications. SIP Network Address Translator (NAT) Application Level Gateway (ALG) SIP session liveness from the details of the particular session.Īnother application of the session timer is in the construction of a However, it is desirable to separate indications of This determinationĬan be made at a user agent without the use of SIP level mechanisms įor audio sessions, periodic RTCP packets serve as an indication of Same reasons a call stateful proxy server would. On a BYE to trigger the removal of state, besides being unreliable, The ALG embedded in a NAT will need to maintain state for theĭuration of a call.
Introduces a potential denial of service attack. Periodic refreshes, through re-INVITEs or This document provides an extension to SIP that defines a sessionĮxpiration mechanism. UPDATEs, are used to keep the session active. Two new header fields (Session-Expires and Min-SE) and a Sufficiently backward compatible with SIP that it works as long asĮither one of the two participants in a dialog understands theĮxtension. Session Interval: The maximum amount of time that can occur between Indicate requirement levels for compliant SIP implementations.Īdditionally, we define the following terms: 'SHALL', 'SHALL NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'MAY',Īnd 'OPTIONAL' are to be interpreted as described in RFC 2119 and In this document, the key words 'MUST', 'MUST NOT', 'REQUIRED', Session-Expires conveys theĭuration of the session, and Min-SE conveys the minimum allowed valueįor the session expiration. Session refresh requests in a dialog before the session will beĬonsidered timed out. Obtains this value from the Session-Expires header field in a 2xx Session-Expires header field, which is defined here. Response to a session refresh request that it sends. UACs determine this value from the Session-Expires header field inĪ 2xx response to a session refresh request that they receive.
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