Byte and Packet Congestion Notification
draft-ietf-tsvwg-byte-pkt-congest-07

The information below is for an old version of the document
Document Type Active Internet-Draft (tsvwg WG)
Last updated 2011-10-31 (latest revision 2011-03-14)
Replaces draft-briscoe-tsvwg-byte-pkt-mark
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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: August 23, 2012                               February 20, 2012

                Byte and Packet Congestion Notification
                  draft-ietf-tsvwg-byte-pkt-congest-07

Abstract

   This memo concerns 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.

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
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   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
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   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 August 23, 2012.

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
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents

Briscoe & Manner         Expires August 23, 2012                [Page 1]
Internet-Draft   Byte and Packet Congestion Notification   February 2012

   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.

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
   5.  Outstanding Issues and Next Steps  . . . . . . . . . . . . . . 24
     5.1.  Bit-congestible Network  . . . . . . . . . . . . . . . . . 24
     5.2.  Bit- & Packet-congestible Network  . . . . . . . . . . . . 24
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 24
   7.  Conclusions  . . . . . . . . . . . . . . . . . . . . . . . . . 25
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