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

["Brett Tate" <brett@broadsoft.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!!!

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.)


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