TCP modifications for Congestion Exposure
draft-ietf-conex-tcp-modifications-01

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Last updated 2012-03-12
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Congestion Exposure (ConEx)                           M. Kuehlewind, Ed.
Internet-Draft                                   University of Stuttgart
Intended status: Experimental                           R. Scheffenegger
Expires: September 13, 2012                                 NetApp, Inc.
                                                          March 12, 2012

               TCP modifications for Congestion Exposure
                 draft-ietf-conex-tcp-modifications-01

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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   This Internet-Draft will expire on September 13, 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
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   described in the Simplified BSD License.

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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  . . . . . . . . . . . . . . . . .  6
     3.2.  Loss Detection with/without SACK . . . . . . . . . . . . .  7
   4.  Setting the ConEx IPv6 Bits  . . . . . . . . . . . . . . . . .  8
     4.1.  Setting the E and the L Bit  . . . . . . . . . . . . . . .  8
     4.2.  Credit Bits  . . . . . . . . . . . . . . . . . . . . . . .  9
   5.  Timeliness of the ConEx Signals  . . . . . . . . . . . . . . . 10
   6.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 11
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 11
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 11
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 11
   Appendix A.  Revision history  . . . . . . . . . . . . . . . . . . 12
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13

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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.  This congestion information is retrived by the sender
   based on existing feedback mechanisms from the receiver to the sender
   in TCP.

   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) from the receiver to the sender.  For ConEx a
   more accurate feedback signal would be beneficial.  Such an extension
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