Hi All,
I am facing one issue regarding session timer refreshing mechanism.
a) As per draft-ietf-sip-session-timer-15.txt, the refresher should send
the session refresh re-Invite/Update at half of the session expiration
time.
The excerpt from draft-ietf-sip-session-timer-15.txt, pg 12 is as
follows:
" If the UAC must perform the refreshes, it computes the session
expiration for that session. The session expiration is the time of
reception of the last 2xx response to a session refresh request on
that dialog plus the session interval for that session. If UA wishes
to continue with the session beyond the session expiration, it MUST
generate a refresh before the session expiration. It is RECOMMENDED
that this refresh be sent once half the session interval has elapsed.
Additional procedures for this refresh are described in Section 10."
b) Also regarding refreshee, draft-ietf-sip-session-timer-15.txt, pg 21
is as follows:
" Similarly, if the side not performing refreshes does not receive a
session refresh request before the session expiration, they SHOULD
send a BYE to terminate the session, slightly before the session
expiration. The minimum of 32 seconds and one third the session
interval is RECOMMENDED."
- Lets analyze the above two conditions with the session-timer
as 90 secs:
t0: session is UP and session-timer starts
t1: t0 + 45: Refresher sends the re-Invite to refresh the session.
t2: t1 + 15: Lets also assume that due to some reason, refreshee does
not receive re-Invite request.
But according to condition b), the refreshee should send
a BYE to the refresher.
In the above scenario, refreshee sends BYE to terminate the session
before re-Invite transaction timeout.
I assume that after time t1, we should wait for ( 45 + 32 ) = 77 secs
before refreshee would receive a BYE request. At the same time,
refreshee is unaware since it haven't received a re-Invite request.
Pl. let me know your views.
Thanks,
Poojan.
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