Controlled Delay Active Queue Management
draft-ietf-aqm-codel-03

The information below is for an old version of the document
Document Type Active Internet-Draft (aqm WG)
Last updated 2016-03-15
Replaces draft-nichols-tsvwg-codel, draft-aqm-codel
Stream IETF
Intended RFC status Experimental
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AQM                                                           K. Nichols
Internet-Draft                                             Pollere, Inc.
Intended status: Informational                               V. Jacobson
Expires: September 16, 2016                             A. McGregor, ed.
                                                         J. Iyengar, ed.
                                                                  Google
                                                          March 15, 2016

                Controlled Delay Active Queue Management
                        draft-ietf-aqm-codel-03

Abstract

   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 http://datatracker.ietf.org/drafts/current/.

   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 16, 2016.

Nichols, et al.        Expires September 16, 2016               [Page 1]
Internet-Draft                    CoDel                       March 2016

Copyright Notice

   Copyright (c) 2016 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
   (http://trustee.ietf.org/license-info) 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.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Conventions used in this document . . . . . . . . . . . . . .   5
   3.  Building Blocks of Queue Management . . . . . . . . . . . . .   5
     3.1.  Estimator . . . . . . . . . . . . . . . . . . . . . . . .   6
     3.2.  Setpoint  . . . . . . . . . . . . . . . . . . . . . . . .   8
     3.3.  Control Loop  . . . . . . . . . . . . . . . . . . . . . .   9
   4.  Putting it together: queue management for the network edge  .  12
     4.1.  Overview of CoDel AQM . . . . . . . . . . . . . . . . . .  12
     4.2.  Non-starvation  . . . . . . . . . . . . . . . . . . . . .  13
     4.3.  Using the interval  . . . . . . . . . . . . . . . . . . .  13
     4.4.  The target setpoint . . . . . . . . . . . . . . . . . . .  14
     4.5.  Use with multiple queues  . . . . . . . . . . . . . . . .  15
     4.6.  Use of stochastic bins or sub-queues to improve
           performance . . . . . . . . . . . . . . . . . . . . . . .  15
     4.7.  Setting up CoDel AQM  . . . . . . . . . . . . . . . . . .  16
   5.  Annotated Pseudo-code for CoDel AQM . . . . . . . . . . . . .  17
     5.1.  Data Types  . . . . . . . . . . . . . . . . . . . . . . .  18
     5.2.  Per-queue state (codel_queue_t instance variables)  . . .  19
     5.3.  Constants . . . . . . . . . . . . . . . . . . . . . . . .  19
     5.4.  Enqueue routine . . . . . . . . . . . . . . . . . . . . .  19
     5.5.  Dequeue routine . . . . . . . . . . . . . . . . . . . . .  19
     5.6.  Helper routines . . . . . . . . . . . . . . . . . . . . .  21
     5.7.  Implementation considerations . . . . . . . . . . . . . .  22
   6.  Adapting and applying CoDel's building blocks . . . . . . . .  23
     6.1.  Validations and available code  . . . . . . . . . . . . .  23
     6.2.  CoDel in the datacenter . . . . . . . . . . . . . . . . .  24
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  25
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