See responses inline...
Samuel.
Unclassified.
>>> "Pavan Kumar Reddy" <[EMAIL PROTECTED]> 02/11/05 07:17AM >>>
Hi All,
I have a question regarding supporting the session timer.
Is Session-Expires header mandatory in INVITE request for
call-establishment,if we support session-timers?
[SAM] I think it depends on the application , so , to me, it is not
mandatory.
Ex:-
A B
INVITE
------------------------------------------>
100 Trying
<-------------------------------------------
180 Ringing
<-------------------------------------------
200 OK
<-------------------------------------------
ACK
------------------------------------------->
<RTP/RTCP>
< ------------------------------------------->
re-INVITE(with Session-Expires header)
------------------------------------------->
200 OK
<-----------------------------------------
ACK
------------------------------------------>
Can i initiate Session-timer extension in re-INVITE? Is the
above scenario is valid ?
[SAM] Yes, you can start it in a re-INVITE
Whats the main advantage of using session-timers - is it for BILLING?
or is it to check whether remote end is active or not?
[SAM] The main goal is for the intermediate proxies to detect that
end-points have crashed and to release resources while in a stateful
behaviour. It is also used to detect that the remote end point has
crashed but it does not provide a fast reaction time if this is what you
were looking for. (see the added section of the draft:)
>From point 4 of the 15th version of the draft (the approved for
standard one):
4.
The absolute minimum for the Session-Expires header field is 90
seconds. This value represents a bit more than twice the duration
that a SIP transaction can take in the event of a timeout. This
allows sufficient time for a UA to attempt a refresh at the
halfpoint
of the session interval, and for that transaction to complete
normally before the session expires. However, 1800 seconds (30
minutes) is RECOMMENDED as the value for the Session-Expires header
field. In other words, SIP entities MUST be prepared to handle
Session-Expires header field values of any duration greater than 90
seconds, but entities that insert the Session-Expires header field
SHOULD NOT choose values less than 30 minutes.
Thanks in advance
Pavan
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