Controlled Delay Active Queue Management
draft-ietf-aqm-codel-05

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AQM                                                           K. Nichols
Internet-Draft                                             Pollere, Inc.
Intended status: Experimental                                V. Jacobson
Expires: May 4, 2017                                    A. McGregor, ed.
                                                         J. Iyengar, ed.
                                                                  Google
                                                        October 31, 2016

                Controlled Delay Active Queue Management
                        draft-ietf-aqm-codel-05

Abstract

   This document describes a general framework called CoDel (Controlled
   Delay) 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 May 4, 2017.

Nichols, et al.            Expires May 4, 2017                  [Page 1]
Internet-Draft                    CoDel                     October 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
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  25