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