Subject: [SIP] Forking proxy and Expires timer

From: Shail Bhatnagar <[email-masked]>
Date: Fri, 02 Jun 2000 17:22:30 -0400

I have a question about the behavior of a forking proxy in a specific
scenario. Here is the scenario :

Proxy receives an INVITE with an Expires header (say 60 seconds) and
forwards
the INVITE to 2 locations. One location immediately returns 302 and the
other
returns 180 ringing (phone keeps ringing). After 60 seconds have
elapsed,
should the proxy return 408 Request Timedout or 302 Moved temporarily (
assuming that proxy is not recursive forking). 
Also, I am assuming that user agent will start the "Expires" timer on
receipt
of the first provisional and the proxy will start the "Expires" timer 
immediately after receiving the INVITE ( or the client's timer will
expire
before the proxy's). 

-- 
Best regards,
Shail

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---

From: Jonathan Rosenberg <[email-masked]>
Date: Sat, 03 Jun 2000 00:08:09 -0400

> assuming that proxy is not recursive forking).

302, as the best response received. Consider timeout is the same as if
408 was actually received.

> before the proxy's)

If Expires contains an exact date, then everyone has the same time. Even
with delta-seconds, I would say its the time of sending the INVITE. If a
UA places an Expires in the INVITE, it really doesn't need to *also*
CANCEL the request itself when the timer expires. It could just as well
do that without having the Expires in the INVITE. You can consider
Expires as sort of asking the proxies to do the CANCEL for you. We
should probably clarify that. 

-Jonathan R.
-- 
Jonathan D. Rosenberg                       72 Eagle Rock Ave.
Chief Scientist                             First Floor
dynamicsoft                                 East Hanover, NJ 07936
[email-masked]                     FAX:   (973) 952-5050
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