[SIPForum-discussion] UAC - INVITE Transaction Timeout Timer

sreekant nair sreekant_nair at yahoo.com
Thu Jun 18 14:20:46 UTC 2009

Hi Everyone,

Have a query regarding Timers. 

If a client sends an INVITE and receives a provisional response but does NOT get a Final Response, is there a Timer that clears up the transaction?

RFC3261 specifies Timer B as the INVITE Transaction Timeout Timer. However in the state transition diagram, there is no mention of whether Timer B is stopped,restarted on moving from the "CALLING" state to the "PROCEEDING" state on receiving a 1xx message. These are my specific queries:

	1. If while in "PROCEEDING" state no final response is received, what happens?
	2. Is it implied that Timer B is only stopped/canceled on receiving a final response? 
	3. What happens when Timer B fires? Should the client send a CANCEL or just kill the transaction?Thanks for any inputs in this regard.

Sreekant Nair

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