Byte and Packet Congestion Notification
draft-ietf-tsvwg-byte-pkt-congest-11

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Transport Area Working Group                                  B. Briscoe
Internet-Draft                                                        BT
Updates: 2309 (if approved)                                    J. Manner
Intended status: BCP                                    Aalto University
Expires: February 2, 2014                                 August 1, 2013

                Byte and Packet Congestion Notification
                  draft-ietf-tsvwg-byte-pkt-congest-11

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 and
   PIE.  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 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 2, 2014.

Copyright Notice

   Copyright (c) 2013 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

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   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  . . . . . . . . . . . . . . . . . . . . . . .  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 . . . . . . . . . . . . . . . . . . . . . 12
     3.1.  Avoiding Perverse Incentives to (Ab)use Smaller Packets  . 12
     3.2.  Small != Control . . . . . . . . . . . . . . . . . . . . . 14
     3.3.  Transport-Independent Network  . . . . . . . . . . . . . . 14
     3.4.  Partial Deployment of AQM  . . . . . . . . . . . . . . . . 15
     3.5.  Implementation Efficiency  . . . . . . . . . . . . . . . . 17
   4.  A Survey and Critique of Past Advice . . . . . . . . . . . . . 17
     4.1.  Congestion Measurement Advice  . . . . . . . . . . . . . . 17
       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 . . . . . . . . . . . . . 21
       4.2.3.  Making Transports Robust against Control Packet
               Losses . . . . . . . . . . . . . . . . . . . . . . . . 23
       4.2.4.  Congestion Notification: Summary of Conflicting