Byte and Packet Congestion Notification
draft-ietf-tsvwg-byte-pkt-congest-08

The information below is for an old version of the document
Document Type Active Internet-Draft (tsvwg WG)
Last updated 2012-08-13
Replaces draft-briscoe-tsvwg-byte-pkt-mark
Stream IETF
Intended RFC status (None)
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Responsible AD Wesley Eddy
Send notices to tsvwg-chairs@tools.ietf.org, draft-ietf-tsvwg-byte-pkt-congest@tools.ietf.org
Transport Area Working Group                                  B. Briscoe
Internet-Draft                                                        BT
Updates: 2309 (if approved)                                    J. Manner
Intended status: BCP                                    Aalto University
Expires: February 14, 2013                               August 13, 2012

                Byte and Packet Congestion Notification
                  draft-ietf-tsvwg-byte-pkt-congest-08

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
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://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 February 14, 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

Briscoe & Manner        Expires February 14, 2013               [Page 1]
Internet-Draft   Byte and Packet Congestion Notification     August 2012

   (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
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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

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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 . . . . . . . . . . . . . . . . . . . . . 11
     3.1.  Avoiding Perverse Incentives to (Ab)use Smaller Packets  . 12
     3.2.  Small != Control . . . . . . . . . . . . . . . . . . . . . 13
     3.3.  Transport-Independent Network  . . . . . . . . . . . . . . 13
     3.4.  Scaling Congestion Control with Packet Size  . . . . . . . 14
     3.5.  Implementation Efficiency  . . . . . . . . . . . . . . . . 16
   4.  A Survey and Critique of Past Advice . . . . . . . . . . . . . 16
     4.1.  Congestion Measurement Advice  . . . . . . . . . . . . . . 16
       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 . . . . . . . . . . . . . . . . . . . . . . . . 22
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