Datacenter TCP (DCTCP): TCP Congestion Control for Datacenters
draft-ietf-tcpm-dctcp-05

Document Type Active Internet-Draft (tcpm WG)
Last updated 2017-04-24 (latest revision 2017-03-27)
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: September 28, 2017                                    Microsoft
                                                               L. Eggert
                                                                  NetApp
                                                                 G. Judd
                                                          Morgan Stanley
                                                          March 27, 2017

     Datacenter TCP (DCTCP): TCP Congestion Control for Datacenters
                        draft-ietf-tcpm-dctcp-05

Abstract

   This informational memo describes Datacenter TCP (DCTCP), an
   improvement to TCP congestion control for datacenter traffic.  DCTCP
   uses improved 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.  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, as detailed in Section 5.

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
   working documents as Internet-Drafts.  The list of current Internet-
   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 September 28, 2017.

Bensley, et al.        Expires September 28, 2017               [Page 1]
Internet-Draft                    DCTCP                       March 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
   carefully, as they describe your rights and restrictions with respect
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   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  . . . . . . . . . . . . . . . . . . . . . . . .   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  . . . . .   4
     3.3.  Processing Echoed Congestion Indications on the Sender  .   6
     3.4.  Handling of packet loss . . . . . . . . . . . . . . . . .   8
     3.5.  Handling of SYN, SYN-ACK, RST Packets . . . . . . . . . .   8
   4.  Implementation Issues . . . . . . . . . . . . . . . . . . . .   8
   5.  Deployment Issues . . . . . . . . . . . . . . . . . . . . . .  10
   6.  Known Issues  . . . . . . . . . . . . . . . . . . . . . . . .  11
   7.  Implementation Status . . . . . . . . . . . . . . . . . . . .  11
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  12
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  12
   10. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  12
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  12
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  13
     11.2.  Informative References . . . . . . . . . . . . . . . . .  13
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  14

1.  Introduction

   Large datacenters necessarily need many network switches to
   interconnect their many servers.  Therefore, a datacenter can greatly
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