Byte and Packet Congestion Notification
RFC 7141
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| Document |
Type |
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RFC - Best Current Practice
(February 2014; No errata)
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Last updated |
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2015-10-14
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Replaces |
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draft-briscoe-tsvwg-byte-pkt-mark
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Stream |
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IETF
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Formats |
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plain text
pdf
html
bibtex
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| Stream |
WG state
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WG Document
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Document shepherd |
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Gorry Fairhurst
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Shepherd write-up |
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Show
(last changed 2013-08-28)
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| IESG |
IESG state |
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RFC 7141 (Best Current Practice)
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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 IC
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Internet Engineering Task Force (IETF) B. Briscoe
Request for Comments: 7141 BT
BCP: 41 J. Manner
Updates: 2309, 2914 Aalto University
Category: Best Current Practice February 2014
ISSN: 2070-1721
Byte and Packet Congestion Notification
Abstract
This document provides recommendations of best current practice for
dropping or marking packets using any active queue management (AQM)
algorithm, including Random Early Detection (RED), BLUE, Pre-
Congestion Notification (PCN), and newer schemes such as CoDel
(Controlled Delay) and PIE (Proportional Integral controller
Enhanced). We give three strong recommendations: (1) packet size
should be taken into account when transports detect and respond to
congestion indications, (2) packet size should not be taken into
account when network equipment creates congestion signals (marking,
dropping), and therefore (3) in the specific case of RED, the byte-
mode packet drop variant that drops fewer small packets should not be
used. This memo updates RFC 2309 to deprecate deliberate
preferential treatment of small packets in AQM algorithms.
Status of This Memo
This memo documents an Internet Best Current Practice.
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). Further information on
BCPs is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7141.
Briscoe & Manner Best Current Practice [Page 1]
RFC 7141 Byte and Packet Congestion Notification February 2014
Copyright Notice
Copyright (c) 2014 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
(http://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.
Briscoe & Manner Best Current Practice [Page 2]
RFC 7141 Byte and Packet Congestion Notification February 2014
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Terminology and Scoping . . . . . . . . . . . . . . . . . 6
1.2. Example Comparing Packet-Mode Drop and Byte-Mode Drop . . 7
2. Recommendations . . . . . . . . . . . . . . . . . . . . . . . 9
2.1. Recommendation on Queue Measurement . . . . . . . . . . . 9
2.2. Recommendation on Encoding Congestion Notification . . . 10
2.3. Recommendation on Responding to Congestion . . . . . . . 11
2.4. Recommendation on Handling Congestion Indications When
Splitting or Merging Packets . . . . . . . . . . . . . . 12
3. Motivating Arguments . . . . . . . . . . . . . . . . . . . . 13
3.1. Avoiding Perverse Incentives to (Ab)use Smaller Packets . 13
3.2. Small != Control . . . . . . . . . . . . . . . . . . . . 14
3.3. Transport-Independent Network . . . . . . . . . . . . . . 14
3.4. Partial Deployment of AQM . . . . . . . . . . . . . . . . 16
3.5. Implementation Efficiency . . . . . . . . . . . . . . . . 17
4. A Survey and Critique of Past Advice . . . . . . . . . . . . 17
4.1. Congestion Measurement Advice . . . . . . . . . . . . . . 18
4.1.1. Fixed-Size Packet Buffers . . . . . . . . . . . . . . 18
4.1.2. Congestion Measurement without a Queue . . . . . . . 19
4.2. Congestion Notification Advice . . . . . . . . . . . . . 20
4.2.1. Network Bias When Encoding . . . . . . . . . . . . . 20
4.2.2. Transport Bias When Decoding . . . . . . . . . . . . 22
4.2.3. Making Transports Robust against Control Packet
Losses . . . . . . . . . . . . . . . . . . . . . . . 23
4.2.4. Congestion Notification: Summary of Conflicting
Advice . . . . . . . . . . . . . . . . . . . . . . . 24
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