Subject: RE: [Ieprep] Re: draft-talauliker-ieprep-diffserv-00.txt

From: "Beard, Cory" <[email-masked]>
Date: Fri, 12 Jul 2002 11:55:42 -0500

Fred and Alistair.

To be clear, our idea is to use AF classes for some emergency traffic,
some of which would use AFn1.

We go beyond that to say, however, that AF should be implemented in a
more limited way than RFC 2597 specifies.  Simply giving highest drop
precedence to emergency traffic is not enough.  We need to use a scheme
that effectively protects emergency traffic in AF queues.

Therefore, we propose the use of mechanisms that treat precedence in a
multi-level fashion where high loads from lower drop precedences do not
substantially affect higher drop precedence traffic.  Many RED variants
use a single queue fill metric to apply dropping to all precedence
levels.  A multi-level approach uses multiple queue fill metrics, one
per drop precedence level.

Variants of this approach have been called RIO (RED with In and Out),
MRED (Multi-level RED), etc.

As for this being a BCP, we follow Scott's comment in Minneapolis that a
BCP is not so much "best current practice" as it is "best current
thinking" or "best current recommendations".  The goal of this document,
therefore, is to say "This is the ieprep WG's recommendation on how to
support emergency services using Diffserv."  

The draft is decidedly lacking in simulation results, since they are not
complete yet.  We could have waited until later to submit the draft, but
wanted to be timely with the activity and goals of the WG.  Besides, we
do not believe the conclusions would change, just the specifics of a
preferred MRED algorithm and drop threshold levels/shaping functions.

Cory

-----
Dr. Cory Beard 
Assistant Professor
Division of Computer Science/Eletrical Engineering
School of Interdisciplinary Computing and Engineering
University of Missouri-Kansas City 
(816) 235-1550, Fax: (816) 235-1260 
http://unofficial.umkc.edu/beardc/

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