TCP modifications for Congestion Exposure
draft-ietf-conex-tcp-modifications-00

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Last updated 2011-12-21
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Congestion Exposure (ConEx)                           M. Kuehlewind, Ed.
Internet-Draft                                   University of Stuttgart
Intended status: Experimental                           R. Scheffenegger
Expires: June 23, 2012                                      NetApp, Inc.
                                                       December 21, 2011

               TCP modifications for Congestion Exposure
                 draft-ietf-conex-tcp-modifications-00

Abstract

   Congestion Exposure (ConEx) is a mechanism by which senders inform
   the network about the congestion encountered by previous packets on
   the same flow.  This document describes the necessary modifications
   to use ConEx with the Transmission Control Protocol (TCP).

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/.

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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on June 23, 2012.

Copyright Notice

   Copyright (c) 2011 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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   (http://trustee.ietf.org/license-info) in effect on the date of
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   described in the Simplified BSD License.

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Internet-Draft  TCP modifications for Congestion Exposure  December 2011

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Requirements Language  . . . . . . . . . . . . . . . . . .  3
   2.  Sender-side Modifications  . . . . . . . . . . . . . . . . . .  3
   3.  Accounting congestion  . . . . . . . . . . . . . . . . . . . .  4
     3.1.  ECN  . . . . . . . . . . . . . . . . . . . . . . . . . . .  5
       3.1.1.  Accurate ECN feedback  . . . . . . . . . . . . . . . .  5
       3.1.2.  Classic ECN support  . . . . . . . . . . . . . . . . .  5
     3.2.  Loss Detection with/without SACK . . . . . . . . . . . . .  7
   4.  Setting the ConEx IPv6 Bits  . . . . . . . . . . . . . . . . .  7
     4.1.  Setting the E and the L Bit  . . . . . . . . . . . . . . .  8
     4.2.  Credit Bits  . . . . . . . . . . . . . . . . . . . . . . .  8
   5.  Timeliness of the ConEx Signals  . . . . . . . . . . . . . . .  9
   6.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 10
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 10
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 10
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 11
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11

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Internet-Draft  TCP modifications for Congestion Exposure  December 2011

1.  Introduction

   Congestion Exposure (ConEx) is a mechanism by which senders inform
   the network about the congestion encountered by previous packets on
   the same flow.  This document describes the necessary modifications
   to use ConEx with the Transmission Control Protocol (TCP).  The ConEx
   signal is based on loss or ECN marks [RFC3168] as a congestion
   indication.

   With standard TCP without Selective Acknowledgments (SACK) [RFC2018]
   the actual number of losses is hard to detect, thus we recommend to
   enable SACK when using ConEx.  However, we discuss both cases, with
   and without SACK support, later on.

   Explicit Congestion Notification (ECN) is defined in such a way that
   only a single congestion signal is guaranteed to be delivered per
   Round-trip Time (RTT).  For ConEx a more accurate feedback signal
   would be beneficial.  Such an extension to ECN is defined in a
   seperate document [draft-kuehlewind-conex-accurate-ecn], as it can
   also be useful for other mechanisms, as e.g.  [DCTCP] or whenever the
   congestion control reaction should be proportional to the expirienced
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