[OpenSIPS-Users] https://datatracker.ietf.org/doc/html/rfc3261#section-13.3.1.1

[Bogdan-Andrei Iancu]

Hi Johan,

In OpenSIPS, the fr_inv_timer kicks in (for INVITEs) when a first reply 
(typically a 100) is received from UAS. And it will wait for the final 
reply. So, it is how long to wait from the first reply up to the final one.

Regards,

Bogdan-Andrei Iancu

OpenSIPS Founder and Developer
   https://www.opensips-solutions.com
   https://www.siphub.com

On 28.03.2024 10:29, Johan De Clercq wrote:
> Question,
>
> I always believed that fr_inv_timer should trigger when an invite is 
> not finished in due time.
> This seems however to contradict the link in the title
>
>   If the UAS is not able to answer the invitation immediately, it can
>     choose to indicate some kind of progress to the UAC (for example, an
>     indication that a phone is ringing).  This is accomplished with a
>     provisional response between 101 and 199.  These provisional
>     responses establish early dialogs and therefore follow the procedures
>     ofSection 12.1.1  <https://datatracker.ietf.org/doc/html/rfc3261#section-12.1.1>  in addition to those ofSection 8.2.6  <https://datatracker.ietf.org/doc/html/rfc3261#section-8.2.6>.  A UAS MAY
>     send as many provisional responses as it likes.  Each of these MUST
>     indicate the same dialog ID.  However, these will not be delivered
>     reliably.
>
>     If the UAS desires an extended period of time to answer the INVITE,
>     it will need to ask for an "extension" in order to prevent proxies
>     from canceling the transaction.  A proxy has the option of canceling
>     a transaction when there is a gap of 3 minutes between responses in a
>     transaction.  To prevent cancellation, the UAS MUST send a non-100
>     provisional response at every minute, to handle the possibility of
>     lost provisional responses.
>
>        An INVITE transaction can go on for extended durations when the
>        user is placed on hold, or when interworking with PSTN systems
>        which allow communications to take place without answering the
>        call.  The latter is common in Interactive Voice Response (IVR)
>        systems.
>
> Can somebody please comment on this ?
>
> BR, Johan.
>
>
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