Laminar TCP and the case for refactoring TCP congestion control
draft-mathis-tcpm-tcp-laminar-00

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TCP Maintenance Working Group                                  M. Mathis
Internet-Draft                                               Google, Inc
Intended status: Experimental                          February 21, 2012
Expires: August 24, 2012

    Laminar TCP and the case for refactoring TCP congestion control
                  draft-mathis-tcpm-tcp-laminar-00.txt

Abstract

   The primary state variables used by all TCP congestion control
   algorithms, cwnd and ssthresh are heavily overloaded, carrying
   different semantics in different states.  This leads to excess
   implementation complexity and poorly defined behaviors under some
   combinations of events, such as loss recovery during cwnd validation.
   We propose a new framework for TCP congestion control, and to recast
   current standard algorithms to use new state variables.  This new
   framework will not generally change the behavior of any of the
   primary congestion control algorithms when invoked in isolation but
   will to permit new algorithms with better behaviors in many corner
   cases, such as when two distinct primary algorithms are invoked
   concurrently.  It will also foster the creation of new algorithms to
   address some events that are poorly treated by today's standards.
   For the vast majority of traditional algorithms the transformation to
   the new state variables is completely straightforward.  However, the
   resulting implementation will technically be in violation of all
   existing TCP standards, even if it is fully compliant with their
   principles and intent.

Status of this Memo

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   This Internet-Draft will expire on August 24, 2012.

Copyright Notice

Mathis                   Expires August 24, 2012                [Page 1]
Internet-Draft                 Laminar TCP                 February 2012

   Copyright (c) 2012 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
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Overview of the new algorithm  . . . . . . . . . . . . . .  3
     1.2.  Standards Impact . . . . . . . . . . . . . . . . . . . . .  4
     1.3.  Meta Language  . . . . . . . . . . . . . . . . . . . . . .  5
   2.  State variables and definitions  . . . . . . . . . . . . . . .  5
   3.  Updated Algorithms . . . . . . . . . . . . . . . . . . . . . .  6
     3.1.  Congestion avoidance . . . . . . . . . . . . . . . . . . .  6
     3.2.  Proportional Rate Reduction  . . . . . . . . . . . . . . .  7
     3.3.  Restart after idle, Congestion Window Validation and
           Pacing . . . . . . . . . . . . . . . . . . . . . . . . . .  8
     3.4.  RTO and F-RTO  . . . . . . . . . . . . . . . . . . . . . .  9
     3.5.  Undo . . . . . . . . . . . . . . . . . . . . . . . . . . .  9
     3.6.  Control Block Interdependence  . . . . . . . . . . . . . .  9
     3.7.  New Reno . . . . . . . . . . . . . . . . . . . . . . . . .  9
   4.  Example Pseudocode . . . . . . . . . . . . . . . . . . . . . . 10
   5.  Compatibility with existing implementations  . . . . . . . . . 11
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 12
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 13
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 14

Mathis                   Expires August 24, 2012                [Page 2]
Internet-Draft                 Laminar TCP                 February 2012

1.  Introduction

   The primary state variables used by all TCP congestion control
   algorithms, cwnd and ssthresh, are heavily overloaded, carrying
   different semantics in different states.  This leads to excess
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