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Timer B is relevent only in the calling state,
ie., no provisional
response. Once a provisional response is
received, it is ignored.
After that, only the proxy layer can figure out
if the transaction
timed out through timer C, which keeps running
until a final response
comes.
----- Original Message -----
Sent: Wednesday, August 21, 2002 1:00
AM
Subject: [Sip-implementors] Timer C in
SIP
Hi All,
I meet a problem about Timer C mention in
section "16.6 Request Forwarding"(RFC3261)
It says:
" 11. Set timer
C
In order to handle
the case where an INVITE request
never
generates a final
response, the TU uses a timer which is
called
timer C.
Timer C MUST be set for each client transaction
when
an INVITE request is
proxied. The timer MUST be larger than
3
minutes. Section
16.7 bullet 2 discusses how this timer
is
updated with
provisional responses, and Section 16.8
discusses
processing when
it fires."
I want to ask:
In a stateful proxy, when a proxy
receives an INVITE, proxy creates
an INVITE client transaction, and then
puts it to transport layer to send,
and set Timer B(64*T1), for the INVITE
client transaction, if Timer B fires,
the client transaction is destroyed
then. But the Timer C set to 3 minutes at least
according to RFC3261. 3
minutes >> 64*T1, when Timer C fires, what can the
proxy do then for
the INVITE client transaction is "dead" already?
Thanks to give
an
answer!
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