Increasing TCP's Initial Window
draft-ietf-tcpm-initcwnd-07

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Internet Draft                                                    J. Chu
draft-ietf-tcpm-initcwnd-07.txt                             N. Dukkipati
Intended status: Experimental                                   Y. Cheng
                                                               M. Mathis
Expiration date: July 2013                                  Google, Inc.
                                                        January 28, 2013

                    Increasing TCP's Initial Window

Status of this Memo

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Chu, et. al.               Expires July 2013                    [Page 1]
Internet Draft      Increasing TCP's Initial Window         January 2013

Abstract

   This document proposes an experiment to increase the permitted TCP
   initial window (IW) from between 2 and 4 segments, as specified in
   RFC 3390, to 10 segments, with a fallback to the existing
   recommendation when performance issues are detected. It discusses the
   motivation behind the increase, the advantages and disadvantages of
   the higher initial window, and presents results from several large
   scale experiments showing that the higher initial window improves the
   overall performance of many web services without resulting in a
   congestion collapse. The document closes with a discussion of usage
   and deployment for further experimental purpose recommended by the
   IETF TCP Maintenance and Minor Extensions (TCPM) working group.

Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  TCP Modification . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Implementation Issues  . . . . . . . . . . . . . . . . . . . .  5
   4.  Background . . . . . . . . . . . . . . . . . . . . . . . . . .  6
   5.  Advantages of Larger Initial Windows . . . . . . . . . . . . .  7
     5.1 Reducing Latency . . . . . . . . . . . . . . . . . . . . . .  7
     5.2 Keeping up with the growth of web object size  . . . . . . .  8
     5.3 Recovering faster from loss on under-utilized or wireless 
         links  . . . . . . . . . . . . . . . . . . . . . . . . . . .  8
   7.  Disadvantages of Larger Initial Windows for the Network  . . .  9
   8.  Mitigation of Negative Impact  . . . . . . . . . . . . . . . . 10
   9.  Interactions with the Retransmission Timer . . . . . . . . . . 10
   10. Experimental Results From Large Scale Cluster Tests  . . . . . 10
     10.1 The benefits  . . . . . . . . . . . . . . . . . . . . . . . 11
     10.2 The cost  . . . . . . . . . . . . . . . . . . . . . . . . . 11
   11. Other Studies  . . . . . . . . . . . . . . . . . . . . . . . . 12
   12. Usage and Deployment Recommendations . . . . . . . . . . . . . 13
   13. Related Proposals  . . . . . . . . . . . . . . . . . . . . . . 14
   14. Security Considerations  . . . . . . . . . . . . . . . . . . . 14
   15. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . 15
   16. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 15
   17. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 15
   Normative References . . . . . . . . . . . . . . . . . . . . . . . 16