468 research outputs found
ABC: A Simple Explicit Congestion Controller for Wireless Networks
We propose Accel-Brake Control (ABC), a simple and deployable explicit
congestion control protocol for network paths with time-varying wireless links.
ABC routers mark each packet with an "accelerate" or "brake", which causes
senders to slightly increase or decrease their congestion windows. Routers use
this feedback to quickly guide senders towards a desired target rate. ABC
requires no changes to header formats or user devices, but achieves better
performance than XCP. ABC is also incrementally deployable; it operates
correctly when the bottleneck is a non-ABC router, and can coexist with non-ABC
traffic sharing the same bottleneck link. We evaluate ABC using a Wi-Fi
implementation and trace-driven emulation of cellular links. ABC achieves
30-40% higher throughput than Cubic+Codel for similar delays, and 2.2X lower
delays than BBR on a Wi-Fi path. On cellular network paths, ABC achieves 50%
higher throughput than Cubic+Codel
ECN verbose mode: a statistical method for network path congestion estimation
This article introduces a simple and effective methodology to determine the
level of congestion in a network with an ECN-like marking scheme. The purpose
of the ECN bit is to notify TCP sources of an imminent congestion in order to
react before losses occur. However, ECN is a binary indicator which does not
reflect the congestion level (i.e. the percentage of queued packets) of the
bottleneck, thus preventing any adapted reaction. In this study, we use a
counter in place of the traditional ECN marking scheme to assess the number of
times a packet has crossed a congested router. Thanks to this simple counter,
we drive a statistical analysis to accurately estimate the congestion level of
each router on a network path. We detail in this paper an analytical method
validated by some preliminary simulations which demonstrate the feasibility and
the accuracy of the concept proposed. We conclude this paper with possible
applications and expected future work
An adaptive active queue management algorithm in Internet
Ce mémoire ne contient pas de résumé
Adaptive Explicit Congestion Notification (AECN) for Heterogeneous Flows
Previous research on ECN and RED usually considered only a limited traffic domain, focusing on networks with a small number of homogeneous flows. The behavior of RED and ECN congestion control mechanisms in TCP network with many competing heterogeneous flows in the bottleneck link, hasn\u27t been sufficiently explored. This thesis first investigates the behavior and performance of RED with ECN congestion control mechanisms with many heterogeneous TCP Reno flows using the network simulation tool, ns-2. By comparing the simulated performance of RED and ECN routers, this study finds that ECN does provide better goodput and fairness than RED for heterogeneous flows. However, when the demand is held constant, the number of flows generating the demand has a negative effect on performance. Meanwhile, the simulations with many flows demonstrate that the bottleneck router\u27s marking probability must be aggressively increased to provide good ECN performance. Based on these simulation results, an Adaptive ECN algorithm (AECN) was studied to further improve the goodput and fairness of ECN. AECN divides all flows competing for a bottleneck into three flow groups, and deploys a different max for each flow group. Meanwhile, AECN also adjusts min for the robust flow group and max to get higher performance when the number of flows grows large. Furthermore, AECN uses mark-front strategy, instead of mark-tail strategy in standard ECN. A series of AECN simulations were run in ns-2. The simulations show clearly that AECN treats each flow fairer than ECN with the two fairness measurements: Jain\u27s fairness index and visual max-min fairness. AECN has fewer packet drops and alleviates the lockout phenomenon and yields higher goodput than ECN
Dual Queue Coupled AQM: Deployable Very Low Queuing Delay for All
On the Internet, sub-millisecond queueing delay and capacity-seeking have
traditionally been considered mutually exclusive. We introduce a service that
offers both: Low Latency Low Loss Scalable throughput (L4S). When tested under
a wide range of conditions emulated on a testbed using real residential
broadband equipment, queue delay remained both low (median 100--300 s) and
consistent (99th percentile below 2 ms even under highly dynamic workloads),
without compromising other metrics (zero congestion loss and close to full
utilization). L4S exploits the properties of `Scalable' congestion controls
(e.g., DCTCP, TCP Prague). Flows using such congestion control are however very
aggressive, which causes a deployment challenge as L4S has to coexist with
so-called `Classic' flows (e.g., Reno, CUBIC). This paper introduces an
architectural solution: `Dual Queue Coupled Active Queue Management', which
enables balance between Scalable and Classic flows. It counterbalances the more
aggressive response of Scalable flows with more aggressive marking, without
having to inspect flow identifiers. The Dual Queue structure has been
implemented as a Linux queuing discipline. It acts like a semi-permeable
membrane, isolating the latency of Scalable and `Classic' traffic, but coupling
their capacity into a single bandwidth pool. This paper justifies the design
and implementation choices, and visualizes a representative selection of
hundreds of thousands of experiment runs to test our claims.Comment: Preprint. 17pp, 12 Figs, 60 refs. Submitted to IEEE/ACM Transactions
on Networkin
Re-feedback: freedom with accountability for causing congestion in a connectionless internetwork
This dissertation concerns adding resource accountability to a simplex internetwork such as the Internet,
with only necessary but sufficient constraint on freedom. That is, both freedom for applications to evolve
new innovative behaviours while still responding responsibly to congestion; and freedom for network
providers to structure their pricing in any way, including flat pricing.
The big idea on which the research is built is a novel feedback arrangement termed ‘re-feedback’.
A general form is defined, as well as a specific proposal (re-ECN) to alter the Internet protocol so that
self-contained datagrams carry a metric of expected downstream congestion.
Congestion is chosen because of its central economic role as the marginal cost of network usage.
The aim is to ensure Internet resource allocation can be controlled either by local policies or by market
selection (or indeed local lack of any control).
The current Internet architecture is designed to only reveal path congestion to end-points, not networks.
The collective actions of self-interested consumers and providers should drive Internet resource
allocations towards maximisation of total social welfare. But without visibility of a cost-metric, network
operators are violating the architecture to improve their customer’s experience. The resulting fight
against the architecture is destroying the Internet’s simplicity and ability to evolve.
Although accountability with freedom is the goal, the focus is the congestion metric, and whether
an incentive system is possible that assures its integrity as it is passed between parties around the system,
despite proposed attacks motivated by self-interest and malice.
This dissertation defines the protocol and canonical examples of accountability mechanisms. Designs
are all derived from carefully motivated principles. The resulting system is evaluated by analysis
and simulation against the constraints and principles originally set. The mechanisms are proven to be
agnostic to specific transport behaviours, but they could not be made flow-ID-oblivious
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