LEDBAT++: Congestion Control for Background Traffic
draft-balasubramanian-iccrg-ledbatplusplus-00

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Network Working Group                                 P. Balasubramanian
Internet-Draft                                                O. Ertugay
Intended status: Informational                                  D. Havey
Expires: January 23, 2020                                      Microsoft
                                                           July 22, 2019

          LEDBAT++: Congestion Control for Background Traffic
             draft-balasubramanian-iccrg-ledbatplusplus-00

Abstract

   This experimental memo describes LEDBAT++, a set of enhancements to
   the LEDBAT (Low Extra Delay Background Transport) congestion control
   algorithm for background traffic.  The LEDBAT congestion control
   algorithm has several shortcomings that prevent it from working
   effectively in practice.  LEDBAT++ extends LEDBAT by adding a set of
   improvements, including reduced congestion window gain, modified
   slow-start, multiplicative decrease and periodic slowdowns.  This set
   of improvement mitigates the known issues with the LEDBAT algorithm,
   such as latency drift, latecomer advantage and inter-LEDBAT fairness.
   LEDBAT++ has been implemented as a TCP congestion control algorithm
   in the Windows operating system.  LEDBAT++ has been deployed in
   production at scale on a variety of networks and been experimentally
   verified to achieve the original stated goals of LEDBAT.

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
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on January 23, 2020.

Copyright Notice

   Copyright (c) 2019 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

Balasubramanian, et al. Expires January 23, 2020                [Page 1]
Internet-Draft                  LEDBAT++                       July 2019

   This document is subject to BCP 78 and the IETF Trust's Legal
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   (https://trustee.ietf.org/license-info) in effect on the date of
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  LEDBAT Issues . . . . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  Latecomer advantage . . . . . . . . . . . . . . . . . . .   3
     3.2.  Inter-LEDBAT fairness . . . . . . . . . . . . . . . . . .   4
     3.3.  Latency drift . . . . . . . . . . . . . . . . . . . . . .   4
     3.4.  Low latency competition . . . . . . . . . . . . . . . . .   4
     3.5.  Dependency on one-way delay measurements  . . . . . . . .   5
   4.  LEDBAT++ Mechanisms . . . . . . . . . . . . . . . . . . . . .   5
     4.1.  Slower than Reno  . . . . . . . . . . . . . . . . . . . .   5
     4.2.  Multiplicative decrease . . . . . . . . . . . . . . . . .   6
     4.3.  Modified slow start . . . . . . . . . . . . . . . . . . .   6
     4.4.  Initial and periodic slowdown . . . . . . . . . . . . . .   7
     4.5.  Use of Round Trip Time instead of one way delay . . . . .   8
   5.  Deployment Issues . . . . . . . . . . . . . . . . . . . . . .   8
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   9
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   9
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction

   Operating systems and applications use background connections for a
   variety of tasks, such as software updates, large media downloads,
   telemetry, or error reporting.  These connections should operate
   without affecting the general usability of the system.  Usability is
   measured in terms of available network bandwidth and network latency.
   LEDBAT [RFC6817] is designed to minimize the impact of lower than