Re: draft-ietf-impp-pres-01

For better or worse, the use of relative times is now pretty much 
universal in SIP. That is what is used in for sip registration 
expiration, in session timers, and in sip event subscription expiration.

I realize that the IMPP definition of presence is distinct from the 
sip/simple implementation of it, but it would be helpful if this weren't 
changed in impp now that it is enshrined in the sip definition of events.

	Paul

Dave Crocker wrote:
> John,
> 
> Wednesday, January 8, 2003, 8:46:06 AM, you wrote:
> John> Let me make several unrelated and uncontroversial comments on
> John> draft-ietf-impp-pres-01.txt.
> 
> John> ***
> 
> John> The use of durations instead of absolute times in subscription
> John> requests makes the most sense to me.
> 
> So, I want to monitor you availability for the next 5 minutes and it
> takes 2 minutes for my request to arrive at the server.  That's ok?
> 
> In any event, can you elaborate on the reasoning behind your
> preference?
> 
> I should offer my own, since Jon's point that both approaches have
> have ambiguity associated is certainly correct.
> 
> Duration has no anchor at all.  There is no way to have any real idea
> when the correct termination time is.
> 
> Absolute time is, well, absolute.  (Jon apparently missed the benefit
> of using universal time zone reference, so that all that must be sent
> is the ending time relative to UT. )
> 
> Internet time syncrhonization is an extremely mature and well-adopted
> technology.  It's readily available and provides pretty amazing
> precision.  So, with absolute time, we can achieve very high
> syncrhonization if we want.




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