Re: [Diffserv-interest] congestion in diffserv network

Brian E Carpenter <brc@zurich.ibm.com> Wed, 29 October 2003 11:10 UTC

Received: from optimus.ietf.org (ietf.org [132.151.1.19] (may be forged)) by ietf.org (8.9.1a/8.9.1a) with ESMTP id GAA03079 for <diffserv-interest-archive@odin.ietf.org>; Wed, 29 Oct 2003 06:10:22 -0500 (EST)
Received: from localhost.localdomain ([127.0.0.1] helo=www1.ietf.org) by optimus.ietf.org with esmtp (Exim 4.20) id 1AEoDE-0002O4-4J for diffserv-interest-archive@odin.ietf.org; Wed, 29 Oct 2003 06:10:04 -0500
Received: (from exim@localhost) by www1.ietf.org (8.12.8/8.12.8/Submit) id h9TBA49M009168 for diffserv-interest-archive@odin.ietf.org; Wed, 29 Oct 2003 06:10:04 -0500
Received: from localhost.localdomain ([127.0.0.1] helo=www1.ietf.org) by optimus.ietf.org with esmtp (Exim 4.20) id 1AEoDB-0002N5-KQ; Wed, 29 Oct 2003 06:10:01 -0500
Received: from odin.ietf.org ([132.151.1.176] helo=ietf.org) by optimus.ietf.org with esmtp (Exim 4.20) id 1AEoCv-0002M0-0K for diffserv-interest@optimus.ietf.org; Wed, 29 Oct 2003 06:09:45 -0500
Received: from ietf-mx (ietf-mx.ietf.org [132.151.6.1]) by ietf.org (8.9.1a/8.9.1a) with ESMTP id GAA03065 for <diffserv-interest@ietf.org>; Wed, 29 Oct 2003 06:09:32 -0500 (EST)
Received: from ietf-mx ([132.151.6.1]) by ietf-mx with esmtp (Exim 4.12) id 1AEoCr-0006C4-00 for diffserv-interest@ietf.org; Wed, 29 Oct 2003 06:09:41 -0500
Received: from d12lmsgate-5.de.ibm.com ([194.196.100.238] helo=d12lmsgate.de.ibm.com) by ietf-mx with esmtp (Exim 4.12) id 1AEoCq-0006Bp-00 for diffserv-interest@ietf.org; Wed, 29 Oct 2003 06:09:40 -0500
Received: from d12relay02.megacenter.de.ibm.com (d12relay02.megacenter.de.ibm.com [9.149.165.196]) by d12lmsgate.de.ibm.com (8.12.10/8.12.8) with ESMTP id h9TB8pNb119288; Wed, 29 Oct 2003 12:08:52 +0100
Received: from ochsehorn.zurich.ibm.com (ochsehorn.zurich.ibm.com [9.4.16.140]) by d12relay02.megacenter.de.ibm.com (8.12.9/NCO/VER6.6) with ESMTP id h9TB7ZZp206662; Wed, 29 Oct 2003 12:07:35 +0100
Received: from zurich.ibm.com (dyn-9-13-127-0.ge.ch.ibm.com [9.13.127.0]) by ochsehorn.zurich.ibm.com (AIX4.3/8.9.3p2/8.9.3) with ESMTP id MAA31906; Wed, 29 Oct 2003 12:07:34 +0100
Message-ID: <3F9F9F56.2917A11A@zurich.ibm.com>
Date: Wed, 29 Oct 2003 12:07:02 +0100
From: Brian E Carpenter <brc@zurich.ibm.com>
Organization: IBM
X-Mailer: Mozilla 4.79 [en] (Windows NT 5.0; U)
X-Accept-Language: en,fr,de
MIME-Version: 1.0
To: John Schnizlein <jschnizl@cisco.com>
CC: Feng Y <feng6@uwindsor.ca>, diffserv-interest@ietf.org
Subject: Re: [Diffserv-interest] congestion in diffserv network
References: <4.3.2.7.2.20031028122043.02283790@wells.cisco.com>
Content-Type: text/plain; charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable
Content-Transfer-Encoding: quoted-printable
Sender: diffserv-interest-admin@ietf.org
Errors-To: diffserv-interest-admin@ietf.org
X-BeenThere: diffserv-interest@ietf.org
X-Mailman-Version: 2.0.12
Precedence: bulk
List-Unsubscribe: <https://www1.ietf.org/mailman/listinfo/diffserv-interest>, <mailto:diffserv-interest-request@ietf.org?subject=unsubscribe>
List-Id: Differentiated services general discussion <diffserv-interest.ietf.org>
List-Post: <mailto:diffserv-interest@ietf.org>
List-Help: <mailto:diffserv-interest-request@ietf.org?subject=help>
List-Subscribe: <https://www1.ietf.org/mailman/listinfo/diffserv-interest>, <mailto:diffserv-interest-request@ietf.org?subject=subscribe>
Content-Transfer-Encoding: quoted-printable

Another way to look at it is that what diffserv does is split the network
into several separate networks, but each of them retains the statistical
properties of a single Internet.

   Brian

John Schnizlein wrote:
> 
> The simple reason that congestion can occur is that the TCA
> need not limit incoming traffic sufficiently to avoid it.
> The TCA for expedited forwarding is the only one, of many
> traffic classes, that seeks to eliminate potential congestion,
> in order to minimize delay and jitter.
> 
> The parameters of other class definitions, assured forwarding
> for example, are intended to mark traffic at different ingress
> rates for different treatment when congestion occurs. Note
> that this anticipates that congestion will occur.
> 
> Please recall that the high link utilization in an IP network
> is obtained in large measure because traffic loads are high
> enough to produce occasional congestion. Cooperative management
> of this congestion is the responsibility of transport-layer
> protocols.
> 
> John
> 
> At 10:43 AM 10/28/2003, Feng Y wrote:
> >... I wonder why the
> >overloading or even congestion occurs in diffserv network.
> >In diffserv architecture, the “DS ingress node is
> >responsible for ensuring that the traffic entering the DS
> >domain conforms to any traffic conditioning agreement (TCA)
> >between it and the other domain to which the ingress node
> >is connected” [RFC 2475]. Moreover,   “Traffic conditioning
> >performs metering, shaping, policing and/or re-marking to
> >ensure that the traffic entering the DS domain conforms to
> >the rules specified in the TCA, in accordance with the
> >domain's service provisioning policy”. So what causes the
> >overloading or congestion in diffserv? Does anyone explain
> >it for me or give me some references. Thanks in advance.
> 
> _______________________________________________
> Diffserv-interest mailing list
> Diffserv-interest@ietf.org
> https://www1.ietf.org/mailman/listinfo/diffserv-interest

-- 
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Brian E Carpenter 
Distinguished Engineer, Internet Standards & Technology, IBM 

NEW ADDRESS <brc@zurich.ibm.com> PLEASE UPDATE ADDRESS BOOK

_______________________________________________
Diffserv-interest mailing list
Diffserv-interest@ietf.org
https://www1.ietf.org/mailman/listinfo/diffserv-interest