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SIP Session Timers are an extension of SIP RFC 2543 which allows a periodic refreshing of SIP sessions using the RE-INVITE message. The refreshing allows both user agents and proxies to determine if the SIP session is still active.
In addition, the SIP software supports response code 422.
Responses in the SIP Support and Compliance Appendix.
Use the following TLVs in the VoIP Protocol Configure (0x00EE) message to implement this feature:
0x027C Min-SE Interval
0x027B Session Interval