Controlled Delay Active Queue Management
draft-ietf-aqm-codel-08
AQM K. Nichols
Internet-Draft Pollere, Inc.
Intended status: Experimental V. Jacobson
Expires: March 15, 2018 A. McGregor, ed.
J. Iyengar, ed.
Google
September 11, 2017
Controlled Delay Active Queue Management
draft-ietf-aqm-codel-08
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.
Status of This Memo
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This Internet-Draft will expire on March 15, 2018.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions used in this document . . . . . . . . . . . . . . 4
3. Understanding the Building Blocks of Queue Management . . . . 4
3.1. Estimator . . . . . . . . . . . . . . . . . . . . . . . . 6
3.2. Target Setpoint . . . . . . . . . . . . . . . . . . . . . 8
3.3. Control Loop . . . . . . . . . . . . . . . . . . . . . . 9
4. Overview of the Codel AQM . . . . . . . . . . . . . . . . . . 12
4.1. Non-starvation . . . . . . . . . . . . . . . . . . . . . 13
4.2. Setting INTERVAL . . . . . . . . . . . . . . . . . . . . 13
4.3. Setting TARGET . . . . . . . . . . . . . . . . . . . . . 14
4.4. Use with multiple queues . . . . . . . . . . . . . . . . 15
4.5. Setting up CoDel . . . . . . . . . . . . . . . . . . . . 15
5. Annotated Pseudo-code for CoDel AQM . . . . . . . . . . . . . 16
5.1. Data Types . . . . . . . . . . . . . . . . . . . . . . . 16
5.2. Per-queue state (codel_queue_t instance variables) . . . 16
5.3. Constants . . . . . . . . . . . . . . . . . . . . . . . . 17
5.4. Enqueue routine . . . . . . . . . . . . . . . . . . . . . 17
5.5. Dequeue routine . . . . . . . . . . . . . . . . . . . . . 17
5.6. Helper routines . . . . . . . . . . . . . . . . . . . . . 18
5.7. Implementation considerations . . . . . . . . . . . . . . 20
6. Further Experimentation . . . . . . . . . . . . . . . . . . . 21
7. Security Considerations . . . . . . . . . . . . . . . . . . . 21
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 21
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 21
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 22
10.1. Normative References . . . . . . . . . . . . . . . . . . 22
10.2. Informative References . . . . . . . . . . . . . . . . . 22
10.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Appendix A. Applying CoDel in the datacenter . . . . . . . . . . 24
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 25
1. Introduction
The "persistently full buffer" problem has been discussed in the IETF
community since the early 80's [RFC896]. The IRTF's End-to-End
Working Group called for the deployment of active queue management
(AQM) to solve the problem in 1998 [RFC2309]. Despite this
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