DualQ Coupled AQMs for Low Latency, Low Loss and Scalable Throughput (L4S)
draft-ietf-tsvwg-aqm-dualq-coupled-12

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Last updated 2020-07-27
Replaces draft-briscoe-tsvwg-aqm-dualq-coupled
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Transport Area working group (tsvwg)                      K. De Schepper
Internet-Draft                                           Nokia Bell Labs
Intended status: Experimental                            B. Briscoe, Ed.
Expires: January 28, 2021                                    Independent
                                                                G. White
                                                               CableLabs
                                                           July 27, 2020

  DualQ Coupled AQMs for Low Latency, Low Loss and Scalable Throughput
                                 (L4S)
                 draft-ietf-tsvwg-aqm-dualq-coupled-12

Abstract

   The Low Latency Low Loss Scalable Throughput (L4S) architecture
   allows data flows over the public Internet to achieve consistent low
   queuing latency, generally zero congestion loss and scaling of per-
   flow throughput without the scaling problems of standard TCP Reno-
   friendly congestion controls.  To achieve this, L4S data flows have
   to use one of the family of 'Scalable' congestion controls (TCP
   Prague and Data Center TCP are examples) and a form of Explicit
   Congestion Notification (ECN) with modified behaviour.  However,
   until now, Scalable congestion controls did not co-exist with
   existing Reno/Cubic traffic --- Scalable controls are so aggressive
   that 'Classic' (e.g.  Reno-friendly) algorithms sharing an ECN-
   capable queue would drive themselves to a small capacity share.
   Therefore, until now, L4S controls could only be deployed where a
   clean-slate environment could be arranged, such as in private data
   centres (hence the name DCTCP).  This specification defines `DualQ
   Coupled Active Queue Management (AQM)', which enables Scalable
   congestion controls that comply with the Prague L4S requirements to
   co-exist safely with Classic Internet traffic.

   Analytical study and implementation testing of the Coupled AQM have
   shown that Scalable and Classic flows competing under similar
   conditions run at roughly the same rate.  It achieves this
   indirectly, without having to inspect transport layer flow
   identifiers.  When tested in a residential broadband setting, DCTCP
   also achieves sub-millisecond average queuing delay and zero
   congestion loss under a wide range of mixes of DCTCP and `Classic'
   broadband Internet traffic, without compromising the performance of
   the Classic traffic.  The solution has low complexity and requires no
   configuration for the public Internet.

De Schepper, et al.     Expires January 28, 2021                [Page 1]
Internet-Draft             DualQ Coupled AQMs                  July 2020

Status of This Memo

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Outline of the Problem  . . . . . . . . . . . . . . . . .   3
     1.2.  Scope . . . . . . . . . . . . . . . . . . . . . . . . . .   6
     1.3.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   7
     1.4.  Features  . . . . . . . . . . . . . . . . . . . . . . . .   9
   2.  DualQ Coupled AQM . . . . . . . . . . . . . . . . . . . . . .  10
     2.1.  Coupled AQM . . . . . . . . . . . . . . . . . . . . . . .  10
     2.2.  Dual Queue  . . . . . . . . . . . . . . . . . . . . . . .  12
     2.3.  Traffic Classification  . . . . . . . . . . . . . . . . .  12
     2.4.  Overall DualQ Coupled AQM Structure . . . . . . . . . . .  13
     2.5.  Normative Requirements for a DualQ Coupled AQM  . . . . .  16
       2.5.1.  Functional Requirements . . . . . . . . . . . . . . .  16
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