Operational Guidance for Deployment of L4S in the Internet
draft-white-tsvwg-l4sops-00

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Transport Area Working Group                               G. White, Ed.
Internet-Draft                                                 CableLabs
Intended status: Informational                             July 30, 2020
Expires: January 31, 2021

       Operational Guidance for Deployment of L4S in the Internet
                      draft-white-tsvwg-l4sops-00

Abstract

   This is an early, work-in-progress draft - a start at getting some of
   the ideas from the mailing list and email exchanges on paper.

   This draft is intended to provide guidance to operators of end-
   systems, operators of networks, and researchers in order to ensure
   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 January 31, 2021.

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   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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White                   Expires January 31, 2021                [Page 1]
Internet-Draft          L4S Operational Guidance               July 2020

   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Per-Flow Fairness . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Operator of an L4S host . . . . . . . . . . . . . . . . . . .   3
     3.1.  CDN Servers . . . . . . . . . . . . . . . . . . . . . . .   3
     3.2.  Other hosts . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Operator of a Network . . . . . . . . . . . . . . . . . . . .   4
     4.1.  Configure AQM to treat ECT1 as NotECT . . . . . . . . . .   4
     4.2.  Configure Non-Coupled Dual Queue  . . . . . . . . . . . .   5
     4.3.  WRED with ECT1 Differentation . . . . . . . . . . . . . .   5
     4.4.  ECT1 Tunnel Bypass  . . . . . . . . . . . . . . . . . . .   6
     4.5.  Disable RFC3168 ECN Marking . . . . . . . . . . . . . . .   6
     4.6.  Re-mark ECT1 to NotECT Prior to AQM . . . . . . . . . . .   6
   5.  Researchers . . . . . . . . . . . . . . . . . . . . . . . . .   6
     5.1.  Detection of Classic ECN FIFO Bottlenecks . . . . . . . .   6
     5.2.  End-to-end measurement of L4S vs. Classic performance . .   6
   6.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .   6
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   9.  Informative References  . . . . . . . . . . . . . . . . . . .   7
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   7

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 or
   Cobalt, and those that implement dual-Q-coupled AQM, L4S traffic
   coexists well with classic congestion controlled traffic.

   On network paths where the bottleneck link 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