Controlled Delay Active Queue Management
draft-ietf-aqm-codel-03
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2016-03-15
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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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