Controlled Delay Active Queue Management

The information below is for an old version of the document
Document Type Active Internet-Draft (aqm WG)
Authors Kathleen Nichols  , Van Jacobson  , Andrew McGregor  , Jana Iyengar 
Last updated 2016-02-14 (latest revision 2015-12-01)
Replaces draft-nichols-tsvwg-codel, draft-aqm-codel
Stream IETF
Intended RFC status Experimental
Formats pdf htmlized (tools) htmlized bibtex
Stream WG state In WG Last Call
Document shepherd Wesley Eddy
IESG IESG state I-D Exists
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AQM                                                           K. Nichols
Internet-Draft                                             Pollere, Inc.
Intended status: Informational                               V. Jacobson
Expires: June 3, 2016                                   A. McGregor, ed.
                                                         J. Iyengar, ed.
                                                        December 1, 2015

                Controlled Delay Active Queue Management


   This document describes a general framework called CoDel (Controlled
   Delay) [CODEL2012] that controls bufferbloat-generated excess delay
   in modern networking environments.  CoDel consists of an estimator, a
   setpoint, and a control loop.  It requires no configuration in normal
   Internet deployments.  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
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at

   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 June 3, 2016.

Nichols, et al.           Expires June 3, 2016                  [Page 1]
Internet-Draft                    CoDel                    December 2015

Copyright Notice

   Copyright (c) 2015 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.  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 this
   awareness, the problem has only gotten worse as 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.  This problem, recently
   christened "bufferbloat", [TSV2011] [BB2011] has become increasingly
   important throughout the Internet but particularly at the consumer
   edge.  Recently, queue management has become more critical due to
   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 affects 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 bloated.

   The development and deployment of effective active queue management
   has been hampered by persistent misconceptions about the cause and
   meaning of packet queues in network buffers.  Network buffers exist
   to absorb the packet bursts that occur naturally in statistically
   multiplexed networks.  Buffers helpfully absorb the queues created by
   such reasonable packet network behavior as short-term mismatches in
   traffic arrival and departure rates that arise from upstream resource
   contention, transport conversation startup transients and/or changes
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