Transport Area Working Group B. Briscoe
Internet-Draft BT
Updates: 2309 (if approved) J. Manner
Intended status: BCP Aalto University
Expires: May 11, 2013 November 7, 2012
Byte and Packet Congestion Notification
draft-ietf-tsvwg-byte-pkt-congest-09
Abstract
This document provides recommendations of best current practice for
dropping or marking packets using active queue management (AQM) such
as random early detection (RED) or pre-congestion notification (PCN).
We give three strong recommendations: (1) packet size should be taken
into account when transports read 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) the byte-mode packet drop variant of the RED AQM
algorithm 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 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
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on May 11, 2013.
Copyright Notice
Copyright (c) 2012 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
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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 . . . . . . . . . . . . . . . . . . . . . . . 8
2.1. Recommendation on Queue Measurement . . . . . . . . . . . 9
2.2. Recommendation on Encoding Congestion Notification . . . . 9
2.3. Recommendation on Responding to Congestion . . . . . . . . 10
2.4. Recommendation on Handling Congestion Indications when
Splitting or Merging Packets . . . . . . . . . . . . . . . 11
3. Motivating Arguments . . . . . . . . . . . . . . . . . . . . . 12
3.1. Avoiding Perverse Incentives to (Ab)use Smaller Packets . 12
3.2. Small != Control . . . . . . . . . . . . . . . . . . . . . 13
3.3. Transport-Independent Network . . . . . . . . . . . . . . 13
3.4. Partial Deployment of AQM . . . . . . . . . . . . . . . . 15
3.5. Implementation Efficiency . . . . . . . . . . . . . . . . 16
4. A Survey and Critique of Past Advice . . . . . . . . . . . . . 16
4.1. Congestion Measurement Advice . . . . . . . . . . . . . . 17
4.1.1. Fixed Size Packet Buffers . . . . . . . . . . . . . . 17
4.1.2. Congestion Measurement without a Queue . . . . . . . . 18
4.2. Congestion Notification Advice . . . . . . . . . . . . . . 19
4.2.1. Network Bias when Encoding . . . . . . . . . . . . . . 19
4.2.2. Transport Bias when Decoding . . . . . . . . . . . . . 21
4.2.3. Making Transports Robust against Control Packet
Losses . . . . . . . . . . . . . . . . . . . . . . . . 22
4.2.4. Congestion Notification: Summary of Conflicting
Advice . . . . . . . . . . . . . . . . . . . . . . . . 23
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