Data Center TCP (DCTCP): TCP Congestion Control for Data Centers
RFC 8257

Document Type RFC - Informational (October 2017; No errata)
Last updated 2017-10-17
Replaces draft-bensley-tcpm-dctcp
Stream IETF
Formats plain text pdf html bibtex
Reviews
Stream WG state Submitted to IESG for Publication (wg milestone: Dec 2015 - Submit document on D... )
Document shepherd Michael Scharf
Shepherd write-up Show (last changed 2017-04-20)
IESG IESG state RFC 8257 (Informational)
Consensus Boilerplate Yes
Telechat date
Responsible AD Mirja K├╝hlewind
Send notices to "Michael Scharf" <michael.scharf@nokia.com>
IANA IANA review state Version Changed - Review Needed
IANA action state No IC
Internet Engineering Task Force (IETF)                        S. Bensley
Request for Comments: 8257                                     D. Thaler
Category: Informational                               P. Balasubramanian
ISSN: 2070-1721                                                Microsoft
                                                               L. Eggert
                                                                  NetApp
                                                                 G. Judd
                                                          Morgan Stanley
                                                            October 2017

    Data Center TCP (DCTCP): TCP Congestion Control for Data Centers

Abstract

   This Informational RFC describes Data Center TCP (DCTCP): a TCP
   congestion control scheme for data-center traffic.  DCTCP extends the
   Explicit Congestion Notification (ECN) processing to estimate the
   fraction of bytes that encounter congestion rather than simply
   detecting that some congestion has occurred.  DCTCP then scales the
   TCP congestion window based on this estimate.  This method achieves
   high-burst tolerance, low latency, and high throughput with shallow-
   buffered switches.  This memo also discusses deployment issues
   related to the coexistence of DCTCP and conventional TCP, discusses
   the lack of a negotiating mechanism between sender and receiver, and
   presents some possible mitigations.  This memo documents DCTCP as
   currently implemented by several major operating systems.  DCTCP, as
   described in this specification, is applicable to deployments in
   controlled environments like data centers, but it must not be
   deployed over the public Internet without additional measures.

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 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc8257.

Bensley, et al.               Informational                     [Page 1]
RFC 8257                          DCTCP                     October 2017

Copyright Notice

   Copyright (c) 2017 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
   (https://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
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  DCTCP Algorithm . . . . . . . . . . . . . . . . . . . . . . .   5
     3.1.  Marking Congestion on the L3 Switches and Routers . . . .   5
     3.2.  Echoing Congestion Information on the Receiver  . . . . .   5
     3.3.  Processing Echoed Congestion Indications on the Sender  .   7
     3.4.  Handling of Congestion Window Growth  . . . . . . . . . .   8
     3.5.  Handling of Packet Loss . . . . . . . . . . . . . . . . .   8
     3.6.  Handling of SYN, SYN-ACK, and RST Packets . . . . . . . .   9
   4.  Implementation Issues . . . . . . . . . . . . . . . . . . . .   9
     4.1.  Configuration of DCTCP  . . . . . . . . . . . . . . . . .   9
     4.2.  Computation of DCTCP.Alpha  . . . . . . . . . . . . . . .  10
   5.  Deployment Issues . . . . . . . . . . . . . . . . . . . . . .  11
   6.  Known Issues  . . . . . . . . . . . . . . . . . . . . . . . .  12
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  12
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  13
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  13
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  13
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  14
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  16
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  16
Show full document text