High-bandwidth Flows Research Articles

Computational modelling and application of mechanical waves to detect arterial network anomalies: Diagnosis of common carotid stenosis

Background and Objective: This paper proposes a novel strategy to localize anomalies in the arterial network based on its response to controlled transient waves. The idea is borrowed from system identification theories in which wave reflections can render significant information about a target system. Cardiovascular system studies often focus on the waves originating from the heart pulsations, which are of low bandwidth and, hence, can hardly carry information about the arteries with the desired resolution. Methods: Our strategy uses a relatively higher bandwidth transient signal to characterize healthy and unhealthy arterial networks through a frequency response function (FRF). We tested our novel approach on data simulated using a one-dimensional cardiovascular model that produced pulse waves in the larger arteries of the arterial network. Specifically, we excited the blood flow from the brachial artery with a relatively high bandwidth flow disturbance and collected the subsequent pressure waveform at peripheral positions. To better differentiate FRFs of healthy and unhealthy networks, we used a FRF that removes the effects of heart pulsations. Results: Results demonstrate the ability of the proposed FRF to detect and follow-up on the development of a common carotid artery (CCA) stenosis. We tested distinct geometrical variations of the stenosis (size, length and position) and observed differences between the FRFs of healthy and unhealthy networks in all cases; such differences were mainly due to geometrical variations determined by the stenosis. Conclusions: We have provided a theoretical proof of concept that demonstrates the ability of our novel strategy to detect and track the development of CCA stenosis by using peripheral pressure waves that can be measured non-invasively in clinical practice.

The bandwidth problem in telecoupled systems governance: Certifying sustainable winemaking in Australia and Chile

Telecoupled systems connect consumption and other choices in one part of the world with land-use and land-cover change in another. While such connections are increasingly well documented, research on governing telecoupled systems is in its infancy. Drawing on recent discussions in sociology, we argue that models for governing telecoupled systems must consider two types of information flows. Low-bandwidth flows allow for limited information transfer but can take place over greater distances. High-bandwidth flows, by contrast, allow for more complex knowledge transfer but tend to be geographically localized due to the costs of maintaining robust connections. Using a mixed-methods case study of national sustainability certification in the wine sector in Australia and Chile, we argue that Chile's counterintuitive success in diffusing its national sustainability certification relates to its geography, which facilitated high-bandwidth connections. We conclude that telecoupling governance measures, such as jurisdictional commodity certification, need to consider the unique requirements and costs of high-bandwidth connections in allocating institutional investments.

Adaptive bandwidth binning for bandwidth management

In this paper, we present a novel bandwidth management scheme that we call adaptive bandwidth binning (ABB). ABB is presented in the context of a DOCSIS cable network, but it has obvious applicability to downstream service on any shared medium access network in which all downstream traffic is scheduled by a single headend device such as a CMTS or wireless base station or access point.ABB is capable of providing approximate weighted max-min fair sharing of downstream bandwidth via a low-overhead scheduler that requires only a small number of permanently allocated queues. A modern delay-based active queue management (AQM) technique is employed to control delays.The performance of ABB is evaluated via ns-2 simulations in which workloads include FTP, HTTP-based adaptive streaming (HAS), and web traffic targeted for different tiered service quality levels. Our results show that ABB is able to provide approximate weighted max-min fair bandwidth allocation among responsive high bandwidth flows while isolating them from low bandwidth and latency sensitive flows. The use of CoDel in each ABB queue is effective in managing latency as required. The use of flow weights in ABB supports service tiering in which subscribers pay more for higher service rates.

ElasticQ: an active queue management algorithm with flow trust

Active queue management (AQM) can improve the network transmission performance and reduce the delay of packets. However, most of previous algorithms cannot achieve the efficiency and fairness simultaneously when high-bandwidth flows exist. In this paper, a novel scheme, named the ElasticQ (elastically fair AQM), is proposed to suppress the high-bandwidth non-responsive flows and enhance the fairness of different flows. Different from previous works, the concept of flow trust is introduced into the design of AQM algorithms to measure the flow's reliability and security effectively. The trust degree of different flows is estimated to decide whether the packets are discarded or not in the proposed scheme with the sample-match mechanism and the packet dropping interval. Simulation experiments results show that ElasticQ could ensure the fairness of various flows, maintain the stability of the queues and decrease the completion time of responsive flows, especially when the responsive flows and non-responsive flows coexist.

A Lightweight Fairness-Driven AQM for Regulating Bandwidth Utilization in Best-Effort Routers

The end-to-end congestion control mechanism of transmission control protocol (TCP) is critical to the robustness and fairness of the best-effort Internet. Since it is no longer practical to rely on end-systems to cooperatively deploy congestion control mechanisms, the network itself must now participate in regulating its own resource utilization. To that end, fairness-driven active queue management (AQM) is promising in sharing the scarce bandwidth among competing flows in a fair manner. However, most of the existing fairness-driven AQM schemes cannot provide efficient and fair bandwidth allocation while being scalable. This paper presents a novel fairness-driven AQM scheme, called CHORD (CHOKe with recent drop history) that seeks to maximize fair bandwidth sharing among aggregate flows while retaining the scalability in terms of the minimum possible state space and per-packet processing costs. Fairness is enforced by identifying and restricting high-bandwidth unresponsive flows at the time of congestion with a lightweight control function. The identification mechanism consists of a fixed-size cache to capture the history of recent drops with a state space equal to the size of the cache. The restriction mechanism is stateless with two matching trial phases and an adaptive drawing factor to take a strong punitive measure against the identified high-bandwidth unresponsive flows in proportion to the average buffer occupancy. Comprehensive performance evaluation indicates that among other well-known AQM schemes of comparable complexities, CHORD provides enhanced TCP goodput and intra-protocol fairness and is well-suited for fair bandwidth allocation to aggregate traffic across a wide range of packet and buffer sizes at a bottleneck router.

High-Bandwidth and Sensitive Air Flow Sensing Based on Resonance Properties of CNT-on-Fiber Hairs

Artificial hair flow sensors were fabricated using piezoresistive, radially grown carbon nanotube arrays on glass fibers and investigated for their dynamic aerodynamic response as measured within an instrumented plane-wave tube. The sensors were experimentally observed to provide both a large bandwidth of operation below first resonance and a strong resonance response at selected frequencies above first resonance. The frequency of first resonance was easily tunable by adjusting the length of the exposed hair and could be made to vary from a few hundred hertz to over 13 kHz. Higher frequency bands were accessible for a given hair length using higher-order resonance modes, up to five of which were observed. All of the responses were understood and modeled using a vibrating Euler-Bernoulli beam analysis.

CFD: an efficient active queue management algorithm with CFD

The existence of the bufferbloat and high-bandwidth non-adaptive flows results in the high queuing delay, which affects the performance of interactive applications, and the inter-flow unfairness, respectively. To solve above-mentioned issues, an efficient active queue management algorithm with Controlling Fairness and Delay (CFD) is proposed. Different from most other schemes, CFD can achieve the low queuing delay and inter-flow fairness simultaneously without the queue isolation. Extensive simulation results also prove the effectiveness and feasibility of CFD.

QoS-Aware Parallel Sensing/Probing Architecture and Adaptive Cross-Layer Protocol Design for Opportunistic Networks

The opening of the ultrahigh frequency (UHF) TV band by the Federal Communications Commission for opportunistic operation promises to relieve the demand on the industrial, scientific, and medical (ISM) bands. However, supporting bandwidth-intensive applications over TV white spaces can be quite challenging, due to the unpredictable nature of spectrum availability and the fluctuations in channel quality. The realization of this Herculean feat through unlicensed usage, while providing protection to licensed primary users, requires intelligent and adaptive protocol design. In this paper, we propose a quality-of-service-aware parallel sensing/probing architecture (QASPA), which exploits inherent channel and user diversity exhibited by the wireless system. Aiming at maximizing the sensing efficiency while achieving high detection accuracy, QASPA incorporates an optimal adaptive double-threshold-based sensing mechanism. It also embodies a cross-layer protocol, which uses an adaptive framing structure to minimize the control overhead, as well as a novel spectrum assignment strategy targeted at improving the spatial reuse of the network. The proposed spectrum assignment strategy supports both channel bonding and aggregation. Our simulations validate the ability of QASPA in guaranteeing the demands of high-bandwidth opportunistic flows while supporting low-bandwidth flows. They also show the superior performance of QASPA compared with the scheme used in the ECMA-392 standard for opportunistic indoor streaming.

AC plasma anemometer—characteristics and design

The characteristics and design of a high-bandwidth flow sensor that uses an AC glow discharge (plasma) as the sensing element is presented. The plasma forms in the air gap between two protruding low profile electrodes attached to a probe body. The output from the anemometer is an amplitude modulated version of the AC voltage input that contains information about the mean and fluctuating velocity components. The anemometer circuitry includes resistance and capacitance elements that simulate a dielectric-barrier to maintain a diffuse plasma, and a constant-current feedback control that maintains operation within the desired glow discharge regime over an extended range of air velocities. Mean velocity calibrations are demonstrated over a range from 0 to 140 m s−1. Over this velocity range, the mean output voltage varied linearly with air velocity, providing a constant static sensitivity. The effect of the electrode gap and input AC carrier frequency on the anemometer static sensitivity and dynamic response are investigated. Experiments are performed to compare measurements obtained with a plasma sensor operating at two AC carrier frequencies against that of a constant-temperature hot-wire. All three sensors were calibrated against the same known velocity reference. An uncertainty based on the standard deviation of the velocity calibration fit was applied to the mean and fluctuating velocity measurements of the three sensors. The motivation is not to replace hot-wires as a general measurement tool, but rather as an alternative to hot-wires in harsh environments or at high Mach numbers where they either have difficulty in surviving or lack the necessary frequency response.

LRURC: A Low Complexity and Approximate Fair Active Queue Management Algorithm for Choking Non-Adaptive Flows

Active Queue Management is an effective way to improve the TCP's performance. However, due to the existence of non-adaptive flows, most previous schemes cannot achieve efficiency, fairness, and easy-to-deploy simultaneously. In this paper, a novel scheme, named LRURC, is proposed to improve the fairness among different flows and reduce the flow completion time when the high-bandwidth non-adaptive flows arise. Motivated by the CHOKe algorithm, the LRURC adopts the sample-match mechanism to identify high-bandwidth flows. Furthermore, the least-recently-used mechanism is introduced to manage the high-bandwidth flows. Different from most other schemes, the LRURC calculates the packet dropping probability according to the flows' rate, which is estimated by the sample-match mechanism. This can achieve fairness effectively and reduce the influence of high-bandwidth non-adaptive flows. When the flow is not hit by the sample-match mechanism, the packet dropping probability remains constant. Simulation results show that LRURC can improve the fairness among different flows, reduce the completion time of adaptive flows, and hold the queue length around an expected value when high-bandwidth non-adaptive flows arise.

Performance Evaluation of Controlling High Bandwidth Flows by RED-PD

This paper proposed to investigate and evaluate the performance of one of the algorithm used to provide fair bandwidth allocation to the flows. First In First Out (FIFO) queuing is simple but does not protect responsive flows from unresponsive one, flows that are sending more than their fair share. One of FIFO queuing is Random Early Detection which it can effectively avoid congestion at routers, but it also cannot provide fair bandwidth for the flows. On the other hand, per-flow scheduling mechanisms provide max-min fairness but are more complex, it requires keeping state for all flows going through the router; it’s proved that high bandwidth flows at the time of congestion consume most of the bandwidth of the link, so this algorithm (RED-PD) is most candidates to provide fairness to the flows. Simulations with networks demonstrate that there are chances for RED-PD to enhance its work, by means of incorporating the test of unresponsive flows actively in response to changes in the packet drop rate.

Active Queue Management for Flow Fairness and Stable Queue Length

Two major goals of queue management are flow fairness and queue-length stability However, most prior works dealt with these goals independently. In this paper, we show that both goals can be effectively achieved at the same time. We propose a novel scheme that realizes flow fairness and queue-length stability. In the proposed scheme, high-bandwidth flows are identified via a multilevel caching technique. Then, we calculate the base drop probability for resolving congestion with a stable queue, and apply it to individual flows differently depending on their sending rates. Via extensive simulations, we show that the proposed scheme effectively realizes flow fairness between unresponsive and TCP flows, and among heterogeneous TCP flows, while maintaining a stable queue.

Long-term flow fairness with fixed memory space

We provide a minimal overhead FIFO queue management scheme which controls link congestion and realizes long-term flow fairness. The proposed scheme is very simple but effective to regulate long term high bandwidth flows. The proposed scheme uses light resources including additional small fixed size memory. The evaluation result verifies the max-min convergence of the proposed mechanism and shows that the proposed scheme outperforms the compared related schemes.

A Simple Mechanism for Throttling High-Bandwidth Flows

This letter presents BREATHe, a simple packet dropping scheme for identifying and throttling unresponsive or misbehaving high-bandwidth flows during times of congestion. BREATHe is different from the existing active queue management techniques in that it uses heavy-hitter set analysis to identify highbandwidth flows rather than sampling or rate estimation. Specifically, BREATHe uses heavy-hitter set analysis to detect highbandwidth flows that exceed some target rate and preferentially drop packets from these flows. We show that the proposed mechanism is effective at throttling high-bandwidth flows using a small amount of state and low-complexity operation.

A rate-based drop policy for punishing unresponsive flows

This paper proposes a drop policy for punishing unresponsive flows. The proposed drop policy uses the difference in traffic arrival patterns of responsive and unresponsive flows, and discards more packets from unresponsive flows. The drop probability of an arriving packet at a router is determined only by the temporal arrival rate of the router at that time, and the router does not need to identify the flow to which the packet belongs. The main advantage of this policy is that it performs well even in the presence of a large number of unresponsive flows since it does not attempt to distinguish high-bandwidth flows. Extensive simulations are presented to show that the proposed policy effectively punishes unresponsive flows by dropping more packets from them in various network situations.

Improvement of LRU cache for the detection and control of long-lived high bandwidth flows

The issue of long-lived high bandwidth flow detection and control with partial flow state is addressed in this paper. The starting point of this work is the least recently used cache proposal, which is generally effective in detecting long-term fast (LTF) flows. However, its performance can be impaired by the following two factors. The first one is the existence of a large amount of short-lived or slow (SLS) flows. Because randomly sampled SLS flows take up quite a lot cache spaces, long-lived high bandwidth flows are often expelled from the cache mistakenly, which leads to degraded performance. The second is the attack from malicious high-bandwidth on/off flows, which can avoid detection by injecting packets on and off alternatively. This paper proposes a novel cache update scheme, Landmark LRU scheme, to improve the performance of the LRU cache in the detection and control of long-lived high bandwidth flows. Firstly, the superiority of the Landmark LRU scheme over the original LRU cache is demonstrated by Markovian analysis. Then simulations driven by real Internet traces prove that the Landmark LRU scheme achieves higher accuracy in long-lived high bandwidth flow detection than the original LRU scheme. Finally, the Landmark LRU cache is incorporated into a well-known active queue management scheme, Random Early Detection, to show its effectiveness in the control of malicious on/off LTF applications. NS-2 simulation shows that the L-LRU-RED scheme outperforms the LRU-RED stably in regulating on/off flows.

End-to-end quality of service for high-end applications

High-end networked applications such as distance visualization, distributed data analysis, and advanced collaborative environments have demanding quality of service (QoS) requirements. Particular challenges include concurrent flows with different QoS specifications, high-bandwidth flows, application-level monitoring and control, and end-to-end QoS across networks and other devices. We describe a QoS architecture and implementation that together help to address these challenges. The General-purpose Architecture for Reservation and Allocation (GARA) supports flow-specific QoS specification, immediate and advance reservation, and online monitoring and control of both individual resources and heterogeneous resource ensembles. Mechanisms provided by the Globus Toolkit are used to address resource discovery and security issues when resources span multiple administrative domains. Our prototype GARA implementation builds on differentiated services mechanisms to enable the coordinated management of two distinct flow types—foreground media flows and background bulk transfers—as well as the co-reservation of networks, CPUs, and storage systems. We present results obtained on a wide area differentiated services testbed that demonstrate our ability to deliver QoS for realistic flows.

Promoting the use of end-to-end congestion control in the Internet

This paper considers the potentially negative impacts of an increasing deployment of non-congestion-controlled best-effort traffic on the Internet. These negative impacts range from extreme unfairness against competing TCP traffic to the potential for congestion collapse. To promote the inclusion of end-to-end congestion control in the design of future protocols using best-effort traffic, we argue that router mechanisms are needed to identify and restrict the bandwidth of selected high-bandwidth best-effort flows in times of congestion. The paper discusses several general approaches for identifying those flows suitable for bandwidth regulation. These approaches are to identify a high-bandwidth flow in times of congestion as unresponsive, TCP-friendly, or simply using disproportionate bandwidth. A flow that is not TCP-friendly is one whose long-term arrival rate exceeds that of any conformant TCP in the same circumstances. An unresponsive flow is one failing to reduce its offered load at a router in response to an increased packet drop rate, and a disproportionate-bandwidth flow is one that uses considerably more bandwidth than other flows in a time of congestion.