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Controlled Delay Active Queue Management

Document type: Active Internet-Draft (individual in tsv area)
Document stream: IETF
Last updated: 2014-03-03
Intended RFC status: Informational
Other versions: plain text, pdf, html

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IESG State: I-D Exists (IESG: Dead)
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TSVWG                                                         K. Nichols
Internet-Draft                                             Pollere, Inc.
Intended status: Informational                               V. Jacobson
Expires: September 4, 2014                                        Google
                                                           March 3, 2014

                Controlled Delay Active Queue Management


   The "persistently full buffer" problem has been discussed in the IETF
   community since the early 80's [RFC896].  The IRTF's End-to-End
   Working Group called for the deployment of active queue management
   (AQM) to solve the problem in 1998 [RFC2309].  Despite the awareness,
   the problem gotten worse as by Moore's Law growth in memory density
   fueled an exponential increase in buffer pool size.  Efforts to
   deploy AQM have been frustrated by difficult configuration and
   negative impact on network utilization.  The full buffer problem,
   recently christened "bufferbloat"[TSVBB2011, BB2011] has become
   increasingly important throughout the Internet but particularly at
   the consumer edge.

   To address bufferbloat, this document describes a general framework
   for controlling excessived delay in networks called Controlled Delay
   (CoDel) designed to work in modern networking environments as a part
   of the solution to bufferbloat [CODEL2012].  CoDel consists of an
   estimator, a setpoint, and a control loop and can be deployed in the
   Internet without configuration.  CoDel comprises some major technical
   innovations and has been made available as open source so that the
   framework can be applied by the community to a range of problems.  It
   has been implemented in Linux (and available in the Linux
   distribution) and deployed in some networks at the consumer edge.  In
   addition, the framework has been successfully applied in other ways.

   Note: Code Components extracted from this document must include the
   license as included with the code in Section 5.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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Nichols & Jacobson      Expires September 4, 2014               [Page 1]
Internet-Draft                    CoDel                       March 2014

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on September 4, 2014.

Copyright Notice

   Copyright (c) 2014 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   ( in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

1.  Introduction

   The need for queue management has been evident for decades.  Recently
   the need has become more critical due to the increased consumer use
   of the Internet mixing large video transactions with time-critical
   VoIP and gaming.  Gettys [TSV2011, BB2011] has been instrumental in
   publicizing the problem and the measurement work [CHARB2007,
   NATAL2010] and coining the term bufferbloat.  Large content
   distributors such as Google have observed that bufferbloat is
   ubiquitous and adversely effects performance for many users.  The
   solution is an effective AQM that remediates bufferbloat at a
   bottleneck while "doing no harm" at hops where buffers are not

   The development and deployment of effective active queue management
   has been hampered by persistent misconceptions about the cause and
   meaning of queues.  Network buffers exist to absorb the packet bursts
   that occur naturally in statistically multiplexed networks.  Short-
   term mismatches in traffic arrival and departure rates that arise
   from upstream resource contention, transport conversation startup

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