Controlled Delay Active Queue Management
draft-ietf-aqm-codel-08
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Active Internet-Draft (aqm WG)
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2017-09-11
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draft-aqm-codel, draft-nichols-tsvwg-codel
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IETF
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Experimental
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Submitted to IESG for Publication
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Wesley Eddy
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(last changed 2016-11-02)
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Approved-announcement to be sent::AD Followup
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Mirja Kühlewind
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Version Changed - Review Needed
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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
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 https://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 March 15, 2018.
Copyright Notice
Copyright (c) 2017 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
(https://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
Nichols, et al. Expires March 15, 2018 [Page 1]
Internet-Draft CoDel September 2017
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 . . . . . . . . . . . . . . . . . . . . . . . . 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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