TCP modifications for Congestion Exposure
draft-ietf-conex-tcp-modifications-08

Document Type Active Internet-Draft (conex WG)
Last updated 2015-07-22 (latest revision 2015-04-22)
Stream IETF
Intended RFC status Experimental
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Congestion Exposure (ConEx)                           M. Kuehlewind, Ed.
Internet-Draft                                                ETH Zurich
Intended status: Experimental                           R. Scheffenegger
Expires: October 24, 2015                                   NetApp, Inc.
                                                          April 22, 2015

               TCP modifications for Congestion Exposure
                 draft-ietf-conex-tcp-modifications-08

Abstract

   Congestion Exposure (ConEx) is a mechanism by which senders inform
   the network about expected congestion based on congestion feedback
   from previous packets in 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.

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   This Internet-Draft will expire on October 24, 2015.

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   Copyright (c) 2015 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Kuehlewind & ScheffeneggExpires October 24, 2015                [Page 1]
Internet-Draft         TCP Modifications for ConEx            April 2015

   the Trust Legal Provisions and are provided without warranty as
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Sender-side Modifications . . . . . . . . . . . . . . . . . .   3
   3.  Counting congestion . . . . . . . . . . . . . . . . . . . . .   4
     3.1.  Loss Detection  . . . . . . . . . . . . . . . . . . . . .   5
       3.1.1.  Without SACK Support  . . . . . . . . . . . . . . . .   6
     3.2.  ECN . . . . . . . . . . . . . . . . . . . . . . . . . . .   7
       3.2.1.  Accurate ECN feedback . . . . . . . . . . . . . . . .   9
       3.2.2.  Classic ECN support . . . . . . . . . . . . . . . . .   9
   4.  Setting the ConEx Flags . . . . . . . . . . . . . . . . . . .  10
     4.1.  Setting the E or the L Flag . . . . . . . . . . . . . . .  11
     4.2.  Setting the Credit Flag . . . . . . . . . . . . . . . . .  11
   5.  Loss of ConEx information . . . . . . . . . . . . . . . . . .  14
   6.  Timeliness of the ConEx Signals . . . . . . . . . . . . . . .  14
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  15
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  15
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  15
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  16
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  16
     10.2.  Informative References . . . . . . . . . . . . . . . . .  16
   Appendix A.  Revision history . . . . . . . . . . . . . . . . . .  17
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  18

1.  Introduction

   Congestion Exposure (ConEx) is a mechanism by which senders inform
   the network about expected congestion based on congestion feedback
   from previous packets in the same flow.  ConEx concepts and use cases
   are further explained in [RFC6789].  The abstract ConEx mechanism is
   explained in [draft-ietf-conex-abstract-mech].  This document
   describes the necessary modifications to use ConEx with the
   Transmission Control Protocol (TCP).

   The markings for ConEx signaling are defined in the ConEx Destination
   Option (CDO) for IPv6 [draft-ietf-conex-destopt].  Specifically, the
   use of four flags is defined: X (ConEx-capable), L (loss
   experienced), E (ECN experienced) and C (credit).

   ConEx signaling is based on loss or Explicit Congestion Notification
   (ECN) marks [RFC3168] as congestion indications.  The sender collects
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