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

[Jonathan Rosenberg <jdrosen@dynamicsoft.com>]

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
jdrosen@dynamicsoft.com                     FAX:   (973) 952-5050
http://www.jdrosen.net                      PHONE: (973) 952-5000
http://www.dynamicsoft.com
 

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