Subject: [Sip] Open issue #185

From: Badri Srinivasan S <[email-masked]>
Date: Wed, 07 Nov 2001 10:53:41 +0530

Hi all..

When an INVITE req with Expires hdr arrives @ a proxy is it not more 
appropriate for the proxy to consider it as the time limit for the location 
service to come back with a rsp rather than for the downstream servers to 
return back with the rsp. In the case of a req going thru a chain of proxies
each & every proxy in the signalling path will try to start a timer with 
the same value in the Expires Hdr & expect the server downstream to respond 
within that time which may not be correct if the network delay is fairly high.
The crux is does'nt the Expires hdr determine the time limit for an 
application to respond to the stack rather than the time limit for 
responses between the stacks..?
If it is the former case then CANCEL @ the proxy can be deprecated..

Thanks,
Badri
Badri Srinivasan S

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---

From: Jonathan Rosenberg <[email-masked]>
Date: Wed, 7 Nov 2001 15:37:07 -0500

> -----Original Message-----
> From: Badri Srinivasan S [mailto:[email-masked]]
> Sent: Wednesday, November 07, 2001 12:24 AM
> To: [email-masked]
> Subject: [Sip] Open issue #185
> 
> 
> Hi all..
> 
> return back with the rsp. 

No, that is not the definition.

> In the case of a req going thru a 
> chain of proxies

Network synchronization isn't required for the Expires to work. 

When the time expires, all of the following should happen:

1. the UAC sends a CANCEL
2. each proxy sends a CANCEL
3. the uas generates a 408 (or 487)

It turns out that this will cause the same amount of network traffic to
occur as if the UAC alone sent a CANCEL. THus, there is no real extra
overhead to having the proxies all send expirations, and the benefit is a
very robust mechanism that will guarnatee you to end the transaction even if
a few elements have gone away.

The only real issue in my mind is the strength of the above three actions
(SHOULD, MAY, MUST). I am inclined towards SHOULD for all three.

-Jonathan R.

---
Jonathan D. Rosenberg, Ph.D.                72 Eagle Rock Ave.
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