Operational Guidance for Deployment of L4S in the Internet
draft-white-tsvwg-l4sops-01
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Greg White
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2020-11-02
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Transport Area Working Group G. White, Ed.
Internet-Draft CableLabs
Intended status: Informational November 2, 2020
Expires: May 6, 2021
Operational Guidance for Deployment of L4S in the Internet
draft-white-tsvwg-l4sops-01
Abstract
This draft is intended to provide guidance to operators of end-
systems, operators of networks, and researchers in order to ensure
successful deployment of L4S in the Internet. It includes mechanisms
that are intended to promote reasonable fairness between L4S and
Classic flows sharing a single-queue [RFC3168] bottleneck link. This
draft identifies opportunites to prevent and/or detect and resolve
fairness problems in such networks.
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 6, 2021.
Copyright Notice
Copyright (c) 2020 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
(https://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
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
White Expires May 6, 2021 [Page 1]
Internet-Draft L4S Operational Guidance November 2020
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Per-Flow Fairness . . . . . . . . . . . . . . . . . . . . . . 3
3. Operator of an L4S host . . . . . . . . . . . . . . . . . . . 3
3.1. CDN Servers . . . . . . . . . . . . . . . . . . . . . . . 4
3.2. Other hosts . . . . . . . . . . . . . . . . . . . . . . . 5
4. Operator of a Network . . . . . . . . . . . . . . . . . . . . 6
4.1. Configure AQM to treat ECT1 as NotECT . . . . . . . . . . 6
4.2. Configure Non-Coupled Dual Queue . . . . . . . . . . . . 6
4.3. WRED with ECT1 Differentation . . . . . . . . . . . . . . 7
4.4. ECT1 Tunnel Bypass . . . . . . . . . . . . . . . . . . . 7
4.5. Disable RFC3168 ECN Marking . . . . . . . . . . . . . . . 8
4.6. Re-mark ECT1 to NotECT Prior to AQM . . . . . . . . . . . 8
5. Researchers . . . . . . . . . . . . . . . . . . . . . . . . . 8
5.1. Detection of Classic ECN FIFO Bottlenecks . . . . . . . . 8
5.2. End-to-end measurement of L4S vs. Classic performance . . 8
6. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 8
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
8. Security Considerations . . . . . . . . . . . . . . . . . . . 8
9. Informative References . . . . . . . . . . . . . . . . . . . 8
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
In the majority of network paths, including paths where the
bottleneck link utilizes packet drops (either due to buffer overrun
or active queue management) in response to congestion, as well as
paths that implement a 'flow-queuing' scheduler such as fq_codel
[RFC8290] or CAKE, and those that implement dual-Q-coupled AQM, L4S
traffic generally coexists well with classic congestion controlled
traffic.
On network paths where the bottleneck link instead implements a
shared-queue (FIFO) with an Active Queue Management algorithm that
provides Explicit Congestion Notification signaling according to
[RFC3168], it has been demonstrated that when a set of long-running
flows comprising both "Classic" congestion controlled flows and L4S-
compliant congestion controlled flows compete for bandwidth, the
classic congestion controlled flows may achieve lower throughput when
compared to the L4S congestion controlled flows. This 'unfairness'
between the two classes appears to be more pronounced on longer RTT
paths (e.g. 50ms and above) and/or at higher link rates (e.g. 50 Mbps
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