TCP Modifications for Congestion Exposure (ConEx)
RFC 7786

Document Type RFC - Experimental (May 2016; No errata)
Last updated 2016-05-13
Stream IETF
Formats plain text pdf html bibtex
Stream WG state Submitted to IESG for Publication
Document shepherd Suresh Krishnan
Shepherd write-up Show (last changed 2015-05-06)
IESG IESG state RFC 7786 (Experimental)
Consensus Boilerplate Yes
Telechat date
Responsible AD Martin Stiemerling
Send notices to (None)
IANA IANA review state Version Changed - Review Needed
IANA action state No IC
Internet Engineering Task Force (IETF)                M. Kuehlewind, Ed.
Request for Comments: 7786                                    ETH Zurich
Category: Experimental                                  R. Scheffenegger
ISSN: 2070-1721                                             NetApp, Inc.
                                                                May 2016

           TCP Modifications for Congestion Exposure (ConEx)

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 document is not an Internet Standards Track specification; it is
   published for examination, experimental implementation, and
   evaluation.

   This document defines an Experimental Protocol for the Internet
   community.  This document is a product of the Internet Engineering
   Task Force (IETF).  It represents the consensus of the IETF
   community.  It has received public review and has been approved for
   publication by the Internet Engineering Steering Group (IESG).  Not
   all documents approved by the IESG are a candidate for any level of
   Internet Standard; see Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc7786.

Kuehlewind & Scheffenegger    Experimental                      [Page 1]
RFC 7786               TCP Modifications for ConEx              May 2016

Copyright Notice

   Copyright (c) 2016 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.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   4
   2.  Sender-Side Modifications . . . . . . . . . . . . . . . . . .   4
   3.  Counting Congestion . . . . . . . . . . . . . . . . . . . . .   5
     3.1.  Loss Detection  . . . . . . . . . . . . . . . . . . . . .   6
       3.1.1.  Without SACK Support  . . . . . . . . . . . . . . . .   7
     3.2.  Explicit Congestion Notification (ECN)  . . . . . . . . .   8
       3.2.1.  Accurate ECN Feedback . . . . . . . . . . . . . . . .  10
       3.2.2.  Classic ECN Support . . . . . . . . . . . . . . . . .  10
   4.  Setting the ConEx Flags . . . . . . . . . . . . . . . . . . .  11
     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.  Open Areas for Experimentation  . . . . . . . . . . . . . . .  15
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  17
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  18
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  18
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  19
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  20
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  20

Kuehlewind & Scheffenegger    Experimental                      [Page 2]
RFC 7786               TCP Modifications for ConEx              May 2016

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 [RFC7713].  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 [RFC7837].  Specifically, the use of four flags
   is defined: X (ConEx-capable), L (loss experienced), E (ECN
   experienced), and C (credit).
Show full document text