The Flow Queue CoDel Packet Scheduler and Active Queue Management Algorithm
RFC 8290
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Type |
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RFC - Experimental
(January 2018; No errata)
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Last updated |
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2018-12-19
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Replaces |
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draft-hoeiland-joergensen-aqm-fq-codel
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IETF
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plain text
pdf
html
bibtex
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Reviews |
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WG state
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Submitted to IESG for Publication
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Document shepherd |
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Wesley Eddy
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Shepherd write-up |
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Show
(last changed 2016-02-14)
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| IESG |
IESG state |
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RFC 8290 (Experimental)
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Consensus Boilerplate |
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Yes
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Telechat date |
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Responsible AD |
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Martin Stiemerling
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Send notices to |
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(None)
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| IANA |
IANA review state |
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Version Changed - Review Needed
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IANA action state |
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No IANA Actions
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Internet Engineering Task Force (IETF) T. Hoeiland-Joergensen
Request for Comments: 8290 Karlstad University
Category: Experimental P. McKenney
ISSN: 2070-1721 IBM Linux Technology Center
D. Taht
Teklibre
J. Gettys
E. Dumazet
Google, Inc.
January 2018
The Flow Queue CoDel Packet Scheduler and
Active Queue Management Algorithm
Abstract
This memo presents the FQ-CoDel hybrid packet scheduler and Active
Queue Management (AQM) algorithm, a powerful tool for fighting
bufferbloat and reducing latency.
FQ-CoDel mixes packets from multiple flows and reduces the impact of
head-of-line blocking from bursty traffic. It provides isolation for
low-rate traffic such as DNS, web, and videoconferencing traffic. It
improves utilisation across the networking fabric, especially for
bidirectional traffic, by keeping queue lengths short, and it can be
implemented in a memory- and CPU-efficient fashion across a wide
range of hardware.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for examination, experimental implementation, and
evaluation.
This document defines an Experimental Protocol for the Internet
community. This document is a product of the Internet Engineering
Task Force (IETF). It represents the consensus of the IETF
community. It has received public review and has been approved for
publication by the Internet Engineering Steering Group (IESG). Not
all documents approved by the IESG are a candidate for any level of
Internet Standard; see Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8290.
Hoeiland-Joergensen, et al. Experimental [Page 1]
RFC 8290 FQ-CoDel January 2018
Copyright Notice
Copyright (c) 2018 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
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.
Hoeiland-Joergensen, et al. Experimental [Page 2]
RFC 8290 FQ-CoDel January 2018
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Conventions Used in This Document . . . . . . . . . . . . 4
1.2. Terminology and Concepts . . . . . . . . . . . . . . . . 5
1.3. Informal Summary of FQ-CoDel . . . . . . . . . . . . . . 5
2. CoDel . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3. Flow Queueing . . . . . . . . . . . . . . . . . . . . . . . . 7
4. The FQ-CoDel Scheduler . . . . . . . . . . . . . . . . . . . 8
4.1. Enqueue . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.1.1. Alternative Classification Schemes . . . . . . . . . 9
4.2. Dequeue . . . . . . . . . . . . . . . . . . . . . . . . . 10
5. Implementation Considerations . . . . . . . . . . . . . . . . 11
5.1. Data Structures . . . . . . . . . . . . . . . . . . . . . 11
5.2. Parameters . . . . . . . . . . . . . . . . . . . . . . . 12
5.2.1. Interval . . . . . . . . . . . . . . . . . . . . . . 12
5.2.2. Target . . . . . . . . . . . . . . . . . . . . . . . 12
5.2.3. Packet Limit . . . . . . . . . . . . . . . . . . . . 13
5.2.4. Quantum . . . . . . . . . . . . . . . . . . . . . . . 13
5.2.5. Flows . . . . . . . . . . . . . . . . . . . . . . . . 13
5.2.6. Explicit Congestion Notification (ECN) . . . . . . . 14
5.2.7. CE Threshold . . . . . . . . . . . . . . . . . . . . 14
5.3. Probability of Hash Collisions . . . . . . . . . . . . . 14
5.4. Memory Overhead . . . . . . . . . . . . . . . . . . . . . 15
5.5. Per-Packet Timestamping . . . . . . . . . . . . . . . . . 16
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