Problem Statement and Requirements for Increased Accuracy in Explicit Congestion Notification (ECN) Feedback
RFC 7560
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RFC - Informational
(August 2015; No errata)
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Last updated |
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2015-10-14
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Replaces |
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draft-kuehlewind-tcpm-accecn-reqs
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IETF
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plain text
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Submitted to IESG for Publication
(wg milestone:
Nov 2013 - Submit document on a...
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Document shepherd |
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Pasi Sarolahti
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Show
(last changed 2014-08-21)
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RFC 7560 (Informational)
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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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No IC
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Internet Engineering Task Force (IETF) M. Kuehlewind, Ed.
Request for Comments: 7560 ETH Zurich
Category: Informational R. Scheffenegger
ISSN: 2070-1721 NetApp, Inc.
B. Briscoe
BT
August 2015
Problem Statement and Requirements for Increased Accuracy
in Explicit Congestion Notification (ECN) Feedback
Abstract
Explicit Congestion Notification (ECN) is a mechanism where network
nodes can mark IP packets, instead of dropping them, to indicate
congestion to the endpoints. An ECN-capable receiver will feed this
information back to the sender. ECN is specified for TCP in such a
way that it can only feed back one congestion signal per Round-Trip
Time (RTT). In contrast, ECN for other transport protocols, such as
RTP/UDP and SCTP, is specified with more accurate ECN feedback.
Recent new TCP mechanisms (like Congestion Exposure (ConEx) or Data
Center TCP (DCTCP)) need more accurate ECN feedback in the case where
more than one marking is received in one RTT. This document
specifies requirements for an update to the TCP protocol to provide
more accurate ECN feedback.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
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/rfc7560.
Kuehlewind, et al. Informational [Page 1]
RFC 7560 Requirements for More Accurate ECN Feedback August 2015
Copyright Notice
Copyright (c) 2015 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. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
2. Recap of Classic ECN and ECN Nonce in IP/TCP . . . . . . . . 5
3. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 6
4. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 8
5. Design Approaches . . . . . . . . . . . . . . . . . . . . . . 11
5.1. Redefinition of ECN/NS Header Bits . . . . . . . . . . . 11
5.2. Using Other Header Bits . . . . . . . . . . . . . . . . . 13
5.3. Using a TCP Option . . . . . . . . . . . . . . . . . . . 13
6. Security Considerations . . . . . . . . . . . . . . . . . . . 14
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
7.1. Normative References . . . . . . . . . . . . . . . . . . 14
7.2. Informative References . . . . . . . . . . . . . . . . . 14
Appendix A. Ambiguity of the More Accurate ECN Feedback in DCTCP 16
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17
Kuehlewind, et al. Informational [Page 2]
RFC 7560 Requirements for More Accurate ECN Feedback August 2015
1. Introduction
Explicit Congestion Notification (ECN) [RFC3168] is a mechanism where
network nodes can mark IP packets instead of dropping them to
indicate congestion to the endpoints. An ECN-capable receiver will
feed this information back to the sender. ECN is specified for TCP
in such a way that only one feedback signal can be transmitted per
Round-Trip Time (RTT). This is sufficient for preexisting TCP
congestion control mechanisms that perform only one reduction in
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