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Problem Statement and Requirements for Increased Accuracy in Explicit Congestion Notification (ECN) Feedback (RFC7560)

IP.com Disclosure Number: IPCOM000242886D
Original Publication Date: 2015-Aug-01
Included in the Prior Art Database: 2015-Aug-27
Document File: 34 page(s) / 41K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

M. Kuehlewind: AUTHOR [+4]

Abstract

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 sending rate per RTT, independent of the number of ECN congestion marks. But recently proposed or deployed mechanisms like Congestion Exposure (ConEx) [RFC6789] or Data Center TCP (DCTCP) [DCTCP] need more accurate ECN feedback than 'classic ECN' [RFC3168] to work correctly in the case where more than one marking is received in any one RTT.

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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

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