LEDBAT++: Congestion Control for Background Traffic
draft-balasubramanian-iccrg-ledbatplusplus-01
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Network Working Group P. Balasubramanian
Internet-Draft O. Ertugay
Intended status: Informational D. Havey
Expires: May 7, 2020 Microsoft
November 4, 2019
LEDBAT++: Congestion Control for Background Traffic
draft-balasubramanian-iccrg-ledbatplusplus-01
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
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://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 May 7, 2020.
Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved.
Balasubramanian, et al. Expires May 7, 2020 [Page 1]
Internet-Draft LEDBAT++ November 2019
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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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. Modified slow start . . . . . . . . . . . . . . . . . . . 5
4.2. Slower than Reno increase . . . . . . . . . . . . . . . . 5
4.3. Multiplicative decrease . . . . . . . . . . . . . . . . . 6
4.4. Initial and periodic slowdown . . . . . . . . . . . . . . 7
4.5. Use of Round Trip Time instead of one way delay . . . . . 7
5. Deployment Issues . . . . . . . . . . . . . . . . . . . . . . 8
6. Security Considerations . . . . . . . . . . . . . . . . . . . 8
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
9.1. Normative References . . . . . . . . . . . . . . . . . . 9
9.2. Informative References . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
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
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