Byte and Packet Congestion Notification
RFC 7141
Document | Type | RFC - Best Current Practice (February 2014; No errata) | |
---|---|---|---|
Authors | Bob Briscoe , Jukka Manner | ||
Last updated | 2015-10-14 | ||
Replaces | draft-briscoe-tsvwg-byte-pkt-mark | ||
Stream | IETF | ||
Formats | plain text html pdf htmlized bibtex | ||
Reviews | |||
Stream | WG state | WG Document | |
Document shepherd | Gorry Fairhurst | ||
Shepherd write-up | Show (last changed 2013-08-28) | ||
IESG | IESG state | RFC 7141 (Best Current Practice) | |
Action Holders |
(None)
|
||
Consensus Boilerplate | Yes | ||
Telechat date | |||
Responsible AD | Martin Stiemerling | ||
Send notices to | (None) | ||
IANA | IANA review state | Version Changed - Review Needed | |
IANA action state | No IANA Actions |
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 5. Outstanding Issues and Next Steps . . . . . . . . . . . . . . 25 5.1. Bit-congestible Network . . . . . . . . . . . . . . . . . 25 5.2. Bit- and Packet-Congestible Network . . . . . . . . . . . 26Show full document text