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