TCP Modifications for Congestion Exposure (ConEx)
RFC 7786
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Type |
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RFC - Experimental
(May 2016; No errata)
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Last updated |
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2016-05-13
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IETF
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WG state
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Submitted to IESG for Publication
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Document shepherd |
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Suresh Krishnan
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Show
(last changed 2015-05-06)
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| IESG |
IESG state |
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RFC 7786 (Experimental)
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Consensus Boilerplate |
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Yes
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Responsible AD |
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Martin Stiemerling
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(None)
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| IANA |
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Version Changed - Review Needed
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No IANA Actions
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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).
ConEx signaling is based on the use of either loss or Explicit
Congestion Notification (ECN) marks [RFC3168] as congestion
indication. The sender collects this congestion information based on
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