Re: draft-ietf-impp-pres-01

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.


John> In Section 3.4, as Dave pointed out for IM, the paragraph 

John>    Note that the transaction-identifier parameter used by the service
John>    is potentially long-lived.  Accordingly, the values generated for
John>    this parameter should be unique across a significant duration of
John>    time.

John> is wrong because a transaction-identifier for a subscription request can be
John> reused as soon as its matching response is received.

1.  I missed that in the spec.  Can you point out where this is said
in the specification.

2.  Re-use of unique identifiers is a little more complicated that
this model suggests.  For example, I send a request and you take a
long time to respond.  I send it again, after you do respond but
before I get the response.  Do you interpret this as a new request or
an old one?  How do you know?

Or, I send a request and you take forever to respond. Do I ever get to
re-use that unique identifier?  How can I know when?

d/
-- 
 Dave <mailto:[email protected]>
 Brandenburg InternetWorking <http://www.brandenburg.com>
 t +1.408.246.8253; f +1.408.850.1850




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