[SIPForum-discussion] UAC - INVITE Transaction Timeout Timer

Tomasz Zieleniewski tzieleniewski at gmail.com
Fri Jun 19 12:50:50 UTC 2009


Timer B is only relevant while transaction is in the initial "calling"
It is used both for reliable and unreliable transports.
When transaction moves to "proceeding" state as it receives
a provisional response, it is completely up to UAC what to do then.
You can compare it to the situation when You call someone
and You hear never ending ringing in the phone.
Probably You will eventually give up and hang up.
The same thing happens here, UAC hang up by sending
a CANCEL which cancels the transaction.

Kind regards,
- Tomasz Zieleniewski

2009/6/18 sreekant nair <sreekant_nair at yahoo.com>

> 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.
> Regards
> Sreekant Nair
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