Subject: [Sip] Open Issue #178: Deprecate absolute times absolutely: SPEAK UP IF YOU USE THEM IN YOUR PRODUCT!!!!!!!!!!

From: Jonathan Rosenberg <[email-masked]>
Date: Thu, 6 Dec 2001 01:09:37 -0500

Issue:

The Expires header and expires param in the Contact header allow for
absolute times expressed in GMT. The problem with using absolute times in
the messages is that they require clock synchronization between the two
elements. This may or may not exist, and will be an interop issue if the
timing is significantly off (say, by an hour, which happens frequently). A
solution is to include the Date in a request whenever you include an
absolute time. This means the recipient computes the difference between the
expiration and the Date header, and uses that as a relative time. Why
bother? Why not simply use ONLY relative times?

Discussion points:

We made the decision to remove absolute time from the session timer
extension. This issue was raised when we did that. Its a no-brainer except
for interop. If there are people sending absolute times, we cannot simply
remove it. Therefore, the proposal depends on whether someone confesses to
sending requests with absolute times:

PROPOSAL A:
  * Remove absolute times entirely from the specification

PROPOSAL B:
  * Elements MUST NOT send messages with absolute times in Expires or
;expires, but they MUST be prepared to receive requests with absolute times
in those headers, for backwards compatibility

If we can do A, we should. So, speak up NOW if you use absolute times!!!

-Jonathan R.

---
Jonathan D. Rosenberg, Ph.D.                72 Eagle Rock Ave.
Chief Scientist                             First Floor
dynamicsoft                                 East Hanover, NJ 07936
[email-masked]                     FAX:   (973) 952-5050
http://www.jdrosen.net                      PHONE: (973) 952-5000
http://www.dynamicsoft.com

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---

From: "Brett Tate" <[email-masked]>
Date: Fri, 7 Dec 2001 02:39:06 -0500

> If we can do A, we should. So, speak up NOW if you use 

Sorry.  Some of our registrar deployments 
pass absolute times in the ";expires" 
of the REGISTER 200 response's Contact.

However PROPOSAL A still sounds good 
since we'd also like to completely remove 
the support of absolute times within SIP.
(Upgrades or patches for our registrar 
could be supplied when appropriate.)

---

From: Shail Bhatnagar <[email-masked]>
Date: Fri, 07 Dec 2001 12:55:18 -0500

Our registrar also uses GMT format in 200 response
to REGISTER.

---

From: Vijay Gurbani <[email-masked]>
Date: Mon, 10 Dec 2001 12:44:53 -0600

Jonathan Rosenberg wrote:
> elements.
[...]
> ;expires, but they MUST be prepared to receive requests with absolute 
> times in those headers, for backwards compatibility
> 

Proposal A is fine.  Our registrar sends out delta time in responses to
Register requests, for instance.

Thanks,

- vijay
-- 
Vijay K. Gurbani  vkg@{lucent.com,research.bell-labs.com,acm.org}
Internet Software and eServices Group 
Lucent Technologies/Bell Labs Innovations, 2000 Lucent Lane, Rm 6G-440
Naperville, Illinois 60566     Voice: +1 630 224 0216   Fax: +1 630 713 0184