Datacenter TCP (DCTCP): TCP Congestion Control for Datacenters
draft-ietf-tcpm-dctcp-10

Document Type Active Internet-Draft (tcpm WG)
Last updated 2017-09-15 (latest revision 2017-08-28)
Replaces draft-bensley-tcpm-dctcp
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Intended RFC status Informational
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Network Working Group                                         S. Bensley
Internet-Draft                                                 D. Thaler
Intended status: Informational                        P. Balasubramanian
Expires: March 2, 2018                                         Microsoft
                                                               L. Eggert
                                                                  NetApp
                                                                 G. Judd
                                                          Morgan Stanley
                                                         August 29, 2017

     Datacenter TCP (DCTCP): TCP Congestion Control for Datacenters
                        draft-ietf-tcpm-dctcp-10

Abstract

   This informational memo describes Datacenter TCP (DCTCP), a TCP
   congestion control scheme for datacenter 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, 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 draft is applicable to deployments in controlled environments
   like datacenters but it must not be deployed over the public Internet
   without additional measures.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
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   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on March 2, 2018.

Bensley, et al.           Expires March 2, 2018                 [Page 1]
Internet-Draft                    DCTCP                      August 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
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
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   include Simplified BSD License text as described in Section 4.e of
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  DCTCP Algorithm . . . . . . . . . . . . . . . . . . . . . . .   4
     3.1.  Marking Congestion on the L3 Switches and Routers . . . .   4
     3.2.  Echoing Congestion Information on the Receiver  . . . . .   5
     3.3.  Processing Echoed Congestion Indications on the Sender  .   6
     3.4.  Handling of Congestion Window Growth  . . . . . . . . . .   8
     3.5.  Handling of Packet Loss . . . . . . . . . . . . . . . . .   8
     3.6.  Handling of SYN, SYN-ACK, RST Packets . . . . . . . . . .   8
   4.  Implementation Issues . . . . . . . . . . . . . . . . . . . .   8
     4.1.  Configuration of DCTCP  . . . . . . . . . . . . . . . . .   8
     4.2.  Computation of DCTCP.Alpha  . . . . . . . . . . . . . . .   9
   5.  Deployment Issues . . . . . . . . . . . . . . . . . . . . . .  10
   6.  Known Issues  . . . . . . . . . . . . . . . . . . . . . . . .  11
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  12
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  12
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  12
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  13
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  13
     10.2.  Informative References . . . . . . . . . . . . . . . . .  13
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