Controlled Delay Active Queue Management
draft-ietf-aqm-codel-05
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-
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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
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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
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25
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