Subject: RE: [Diffserv] Yesterday's EF discussion

From: Jon Bennett <[email-masked]>
Date: Sat, 16 Dec 2000 11:39:26 -0500

Alper,

> > We have argued in SD that the definition we propose 
> > describes two different *aspects* of the same behavior, 
> > rather than two different behaviors. Both 
> > aspects of the behavior are useful in evaluating the quality of EF 
> 
> Two different aspects of the same behavior is not the same 
> behavior. It is a new bahavior. 
> A = {x,y}, B={x}, C={y} B != A, C != A, A == A. I hope this helps.

I am afraid it does not help, two different aspects of the same behavior IS
the same behavior. Let me make this clear the BEHAVIOR that draft-chary
specifies is the same as RFC 2598, that is the device "shall provide a
service to the EF aggregate at a configured EF rate over as small a time
scale as possible", a device will attempt to do so and however it does will
define the BEHAVIOR of the device. The same device could declare the
EFRESOLVE tuple of R,B,S or the draft-charny E_a, these would just be
methods of MEASURING the behavior, they do not DEFINE the behavior. And our
view has been all along that the best way to measure (not define) the
behavior is through E_a. 

This misconception that the either E or S somehow are the definition of the
behavior is being repeatedly made and I believe that it is very damaging to
the process of understanding the issue. 

Let me make this point one last time that what we are proposing will define
the identical behavior as the current definition of the EF PHB, RFC 2598 by
asking you to compare the text of RFC 2598 and the compromise text that we
sent to the EFRESOLVE team before the meeting.
It is now apparent that we should have sent our entire new text to the list
and not just the new equation given the fixation that some people seem to
have with this issue. I will assume that from now on it will be clear that
we are proposing the identical behavior as RFC 2598.

jon

------------------------------------------------

RFC 2598

2. Description of EF per-hop behavior

   The EF PHB is defined as a forwarding treatment for a particular
   diffserv aggregate where the departure rate of the aggregate's
   packets from any diffserv node must equal or exceed a configurable
   rate. ............
   
   The EF traffic SHOULD receive this rate independent of the
   intensity of any other traffic attempting to transit the node.  It
   SHOULD average at least the configured rate when measured over any
   time interval equal to or longer than the time it takes to send an
   output link MTU sized packet at the configured rate.  (Behavior at
   time scales shorter than a packet time at the configured rate is
   deliberately not specified.) The configured minimum rate MUST be
   settable by a network administrator (using whatever mechanism the
   node supports for non-volatile configuration).

---------------------------------------------

OUR COMPROMISE TEXT (as sent to the EFRESOLVE TEAM)

2. The Formal Definition of EF PHB.

   The EF PHB is defined as a forwarding treatment for a particular 
   diffserv aggregate where the departure rate of the aggregate's 
   packets from any diffserv node must equal or exceed a configurable 
   rate. 

   An EF compliant device MUST specify two error terms that characterize 
   its maximum deviation from ideal behavior. E_a represents the maximum 
   deviation of its actual service rate for the EF aggregate from the ideal 
   service at the configured rate. E_p represents the maximum time a packet 
   can be delayed beyond its ideal departure time in an ideal FIFO server at

   the configured rate.

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---

From: demir <[email-masked]>
Date: Sat, 16 Dec 2000 09:14:17 -0800 (PST)

Jon,
To me, what I am stating on EF BEHAVIOR and what you are stating on EF 
BEHAVIOR is that how we "perceive" "EF PHB-RFC 2598" individually. I
assume, the authors of EF PHB-2598 are the "right" people who can make
"right" decision on our "perception" (please note that I am not saying
"only" and you might be among "right").

> view has been all along that the best way to measure (not define) the
I am agree with the last part. They are "parameters" for "measurements". I
have never intented to use them in my "set" example. It is wrong. Here is
how I see the problem (Note: elements are not parameters to define a
BEHAVIOR)
	EF={?}, ? is "unknown element(s)", let's assume for this example
	EFRESOLVE = {D, DV} U {R}, where {R} is not explicitly stated, and
                                   needs clarification, I might be wrong
	CHARNY = {D, R} U {dv}, again that's how I see, I might be wrong

Note 1: R is what you stated above about rate
Note 2: For short, "BEHAVIOR" word is omitted
Question 1: is DV == dv ? (a simple question)
Question 2: is EFRSOLVE == EF ?
Question 3: is CHARNY  == EF ?

These are the 3 questions that we are trying to address (the exam will
over in an hour :)

> the process of understanding the issue. 

100% agreed. I hope I am not one of them.

> sent to the EFRESOLVE team before the meeting.

Last time :)

> we are proposing the identical behavior as RFC 2598.

If you are refereing to me when I posted some "equations", They were not
intended for "BEHAVIOR" discussion. they were intended for particular
"compromise ... draft-charny".

The "identical" is a very "critical" term here :) some more
criticals: "same","equivalent",... Needs clarificifation.

Alper K. Demir