Operational Guidance for Deployment of L4S in the Internet
draft-white-tsvwg-l4sops-01

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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.

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   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
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   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