DualQ Coupled AQMs for Low Latency, Low Loss and Scalable Throughput (L4S)
draft-ietf-tsvwg-aqm-dualq-coupled-13
Transport Area working group (tsvwg) K. De Schepper
Internet-Draft Nokia Bell Labs
Intended status: Experimental B. Briscoe, Ed.
Expires: May 19, 2021 Independent
G. White
CableLabs
November 15, 2020
DualQ Coupled AQMs for Low Latency, Low Loss and Scalable Throughput
(L4S)
draft-ietf-tsvwg-aqm-dualq-coupled-13
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 May 19, 2021 [Page 1]
Internet-Draft DualQ Coupled AQMs November 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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