TCP modifications for Congestion Exposure
draft-ietf-conex-tcp-modifications-03

The information below is for an old version of the document
Document Type Active Internet-Draft (conex WG)
Last updated 2013-05-30
Stream IETF
Intended RFC status (None)
Formats plain text pdf html bibtex
Stream WG state WG Document
Document shepherd None
IESG IESG state I-D Exists
Consensus Boilerplate Unknown
Telechat date
Responsible AD (None)
Send notices to (None)
Congestion Exposure (ConEx)                           M. Kuehlewind, Ed.
Internet-Draft                                   University of Stuttgart
Intended status: Experimental                           R. Scheffenegger
Expires: December 01, 2013                                  NetApp, Inc.
                                                            May 30, 2013

               TCP modifications for Congestion Exposure
                 draft-ietf-conex-tcp-modifications-03

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
   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 December 01, 2013.

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
   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
   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.

Kuehlewind & ScheffenegExpires December 01, 2013                [Page 1]
Internet-Draft TCP modifications for Congestion Exposure        May 2013

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Sender-side Modifications . . . . . . . . . . . . . . . . . .   3
   3.  Accounting congestion . . . . . . . . . . . . . . . . . . . .   4
     3.1.  ECN . . . . . . . . . . . . . . . . . . . . . . . . . . .   4
       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 Bits  . . . . . . . . . . . . . . . . . . .   8
     4.1.  Setting the E and the L Bit . . . . . . . . . . . . . . .   8
     4.2.  Credit Bits . . . . . . . . . . . . . . . . . . . . . . .   8
     4.3.  Loss of ConEx information . . . . . . . . . . . . . . . .   9
   5.  Timeliness of the ConEx Signals . . . . . . . . . . . . . . .  10
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  10
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  11
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  11
   Appendix A.  Revision history . . . . . . . . . . . . . . . . . .  12
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  13

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 retrieved 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
   to ECN is defined in a seperate document
   [draft-kuehlewind-conex-accurate-ecn], as it can also be useful for
Show full document text