Subject: Re: comments on rsvp spec

From: [email-masked] (John Krawczyk)
Date: Mon, 3 Apr 95 10:57:03 EDT

On Mon,  3 April, Francois Toutain ([email-masked]) wrote:
   	
   >	Also, the possibility of "existing reservation failure" isn't
   >	mentioned.  Policy guidelines might require the "bumping" of certain
   >	reservations when a "more important" request comes through.  An
   >	administrator may also decide that too many of their precious
   >	resources are being used for reserved traffic (best-effort users are
   >	complaining) and therefore reduce the amount of reservable resources,
   >	requiring the termination of one or more reservations.
   	
   How high do you think users are willing to be charged if their
   reservations may be subject to such abrupt termination ? Which criteria
   should be used to select the unlucky reservations ? How could request
   "importance" be characterized ? Why should a reservation be broken when
   the others are full quality streams (could be degradated, perhaps) ?
   
The Integrated Services RFC (or one of the documents it references)
talked about an "interruptable" service where a user pays less knowing
that they might get bumped to best-effort at some point.

Beyond that, I can think of a couple of examples in a private internet
where you'd want a new flow to take precedence over existing flows:

	Some big-wig needs to hold a conference call and can't get
	the reservation to succeed.

	It's time to do the overnight backups which must finish
	by 8:00am.

   Very interesting topic, indeed...
   
Agreed.

-jj

P.S.  Does everyone else get a mailbox full of bounces when they
send to this list or to int-serv?  Should I forward these somewhere?
([email-masked] maybe?).

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From: [email-masked]
Date: Mon, 03 Apr 95 12:55:57 -0400

> the others are full quality streams (could be degradated, perhaps) ?

All are good questions.  Yet we should try to plan for this.

I think the price difference should depend very much on the probability of
termination.  I think that in most places, telephone calls are interruptable
without compensation to the user.  This is tolerable because it is very
rarely done.  It is also the case in many places in the US that natural gas
service can be bought as "A-gas" or "I-gas" where the I-gas service is
interruptible for long periods of time (months) and is charged at a lower
rate (20-50% ?? I forget).  These are two points in a spectrum of possible
cases.  (It is interesting that A-gas customers do not guarantee either a
maximum or minimum usage level, but the supplier commits to try hard to meet
whatever demand those customers impose.  The supplier estimates demand and
tries to acquire supply based on historical data and predictive models.)

So, I think that an in-band preemption mechanism should be defined that can
be applied to any reservation whatsoever.  The same mechanism that preempts
totally can probably degrade partially, if that's a desirable thing to do.
In practice, though, these actions should not be applied equally to every
reservation, and tight access controls will probably be needed since we are
unlikely to solve quickly the problem of varying, perhaps incommensurable,
importance metrics in different portions of the Internet.  Arbitrating
between the Home Shopping Network, Carl Malamud, and Freddie Joe Acme is
"too hard" to solve globally, but it's not "too hard" within the scope of
the boxes and wires that belong to the Acme Widget Company.

/Bill

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