Nonlinear dynamics in Internet congestion control model with TCP Westwood under RED

of the congestion control system with TCPW connections and RED gateway.     

Analysis of gateway congestion in interconnected high-speed localnetworks

The effects of congestion on performance in interconnected high-speed local networks are investigated. The system studied uses network adapters as gateways to connect distributed local networks through a high-performance network link. Throughput measurements were determined by simulations of various combinations of link speeds, gateway buffering capacities, and local network traffic loads. The performance effects of several high-speed, local-network, bus-access protocols are investigated. Simulation model parameters are based on measurements of HYPERchannel networks     

TCH排队功能研究

TCH信道资源不足将导致TCH拥塞,影响终端用户的接入性能和用户感知。引入开通TCH排队功能,改善TCH拥塞程度,试验前后的统计数据表明这种方法在特定网络情况下,对于改善TCH拥塞有非常好的效果。     

Asymptotic behavior of heterogeneous TCP flows and RED gateway

We introduce a stochastic model of a bottleneck ECN/RED gateway under a large number of heterogeneous TCP flows, i.e., flows with diverse round-trip delays and session dynamics. We investigate the asymptotic behavior of the system and show that as the number of flows becomes large, the buffer dynamics and aggregate traffic simplify and can be accurately described by simple stochastic recursions independent of the number of flows, resulting in a scalable model. Based on the Central Limit analysis in the paper, we identify the sources of fluctuations in queue size and describe the relationship between the system parameters such as the marking function and variance of queue size. A closed-form approximation for the mean queue size as a function of system parameters is provided from a simple steady-state analysis. Numerical examples are provided to validate our results.     

基于专家控制的无线网络拥塞控制机制的研究

由于无线网络中存在高误码、信号衰落、切换等原因，使得传统TCP的应用受到了挑战。本文提出了将专家控制用于无线网络的拥塞控制方案，它通过推理判断，确定当前的TCP连接状况，进而区分网络拥塞和无线链路差错，然后再针对不同的原因，选取正确的控制策略实施拥塞控制。仿真结果表明，该方法增强了网络对拥塞以及随机差错的实时处理能力，提高了网络的吞吐量，算法本身具有较强的顽健性。     

ATM traffic management and congestion control using fuzzy logic

The paper focuses on the use of fuzzy logic in network management, ATM congestion control, and ATM switching. The ATM network management ensures traffic agreement at the source level in order to prevent congestion situations from occurring. The paper reviews work in the area of traffic policing and introduces a scheme for improving the performance of a fuzzy policer. The ATM fuzzy switch introduced, enhances the capabilities of the ATM switch, one of the most critical elements in the ATM network     

Sink-to-sensors congestion control

The problem of congestion in sensor networks is significantly different from that of conventional ad-hoc networks and has not been studied to any great extent thus far. In this paper, we focus on providing congestion control from the sink to the sensors in a sensor field. We identify the different reasons for congestion from the sink to the sensors and show the uniqueness of the problem in sensor network environments. We propose a generic framework that addresses congestion from the sink to the sensors in a sensor network. Through ns2 based simulations, we evaluate the proposed approach and compare its performance with three baseline approaches.     

Accumulation-based congestion control

This paper generalizes the TCP Vegas congestion avoidance mechanism and uses accumulation , buffered packets of a flow inside network routers, as a congestion measure based on which a family of congestion control schemes can be derived. We call this model Accumulation-based Congestion Control (ACC), which fits into the nonlinear optimization framework proposed by Kelly. The ACC model serves as a reference for packet-switching network implementations. We show that TCP Vegas is one possible scheme under this model. It is well known that Vegas suffers from round trip propagation delay estimation error and reverse path congestion. We therefore design a new Monaco scheme that solves these problems by employing an out-of-band, receiver-based accumulation estimator, with the support of two FIFO priority queues from the (congested) routers. Comparisons between these two schemes demonstrate that Monaco does not suffer from the problems mentioned above and achieves better performance than Vegas. We use ns-2 simulations and Linux implementation experiments to show that the static and dynamic performance of Monaco matches the theoretic results. One key issue regarding the ACC model in general, i.e., the scalability of bottleneck buffer requirement, and a solution using a virtual queueing algorithm are discussed and evaluated.     

基于平均队列长度和滞留时间的RED算法

在无线通信网络环境下，提出了一种改进的基于平均队列长度和滞留时间的RED算法。这种算法根据平均队列长度和滞留时间计算数据包的丢弃概率，比传统的单纯基于平均队列长度的RED算法相比较，能更有效地实现无线网络中的拥塞控制。     

Distributed collision control with the integration of packet size for congestion control in wireless sensor networks

Several great features offered by wireless sensor networks (WSN) result in its wide deployment in various remote and continuous monitoring applications. As such, managing huge collected readings in this domain posted many challenges due to its design limitations. In order to provide seamless data transmission, which is of utmost importance in those delay‐sensitive applications, minimum delay and packet loss occurrence should be considered. Specifically, this paper addresses the common issue of congested networks in WSN with the combination technique of variance‐based distributed contention control (DCC‐V) and packet size optimization. The proposed integration technique, which operates on medium access control layer, takes into consideration the packet size advantages as it plays a key role in determining successful data delivery, given the error‐prone nature of WSN. While ensuring fewer corrupted packets, the proposed contention window (CW) in DCC‐V minimizes the chances of packet collisions and so alleviates congestion. In this technique, CW is determined based on slot utilization and average collision values, which also involve standard deviation measurements. Simulation analysis using network simulator‐2 shows outstanding performance of the proposed solution compared with the existing IEEE 802.15.4 protocol. Copyright © 2014 John Wiley & Sons, Ltd.     

PAQM: an adaptive and proactive queue management for end‐to‐end TCP congestion control

Two functions, the congestion indicator (i.e. how to detect congestion) and the congestion control function (i.e. how to avoid and control congestion), are used at a router to support end‐to‐end congestion control in the Internet. Random early detection (RED) (IEEE/ACM Trans. Networking 1993; 1 (4):397–413) enhanced the two functions by introducing queue length averaging and probabilistic early packet dropping. In particular, RED uses an exponentially weighted moving average (EWMA) queue length not only to detect incipient congestion but also to smooth the bursty incoming traffic and its resulting transient congestion. Following RED, many active queue management (AQM)‐based extensions have been proposed. However, many AQM proposals have shown severe problems with detection and control of the incipient congestion adaptively to the dynamically changing network situations. In this paper, we introduce and analyse a feedback control model of TCP/AQM dynamics. Then, we propose the Pro‐active Queue Management (PAQM) mechanism, which is able to provide proactive congestion avoidance and control using an adaptive congestion indicator and a control function under a wide range of traffic environments. The PAQM stabilizes the queue length around the desired level while giving smooth and low packet loss rates and high network resource utilization. Copyright © 2004 John Wiley & Sons, Ltd.     

Compact photonic gateway for dynamic path control using acousto-optic tunable filter

A compact photonic gateway for wavelength-path control with a simple configuration at low cost was developed. The gateway achieves wavelength-path control by using acousto-optic tunable filters (AOTF). The fabricated four-channel integrated AOTF device exhibits a high performance with regard to polarization-independent characteristics, side-lobe suppression, higher extinction ratio, and narrower bandwidth for 100 GHz spacing. An AOTF subsystem was fabricated by combining an AOTF with the control circuit to exploit the AOTF’s high-speed switching to the full and operate it stably for practical use and achieve stable operation of the AOTF. We manufactured the photonic gateway node by assembling the AOTF subsystem with the provisioning control and redundant system.     

PNNI routing congestion control

There is evidence based on previous failures that link state protocols such as PNNI may not be able to recover from a widespread loss of topology database information or an overload of topology state updates. To prevent this, PNNI extensions have been adopted in the ATM forum to avoid going into congestion and to recover when congestion occurs. This article presents the adopted mechanisms to enable the PNNI routing protocol to avoid congestion states wherever possible, to respond gracefully to network overloads and failures, and to recover from massive loss of topology database information. The mechanisms include detecting congestion and notifying peers, reducing the rate of topology update control messages, maintaining link adjacencies with prioritized treatment of critical control messages, database backup, graceful recovery of lost topology database information, and database resynchronization. Simulation analysis demonstrates the effectiveness of these routing congestion control mechanisms.     

Distributed congestion control strategy using network utility maximization theory in VANET

Cooperative vehicle safety system (CVSS) rely on periodical beacons to track neighboring vehicles.High traffic density often causes channel congestion,seriously damaging the performance of CVSS.Existing congestion control strategies aim to ensure the performance in network layer,without considering the service requirements of vehicles in different driving contexts.To solve the problem,a distributed congestion control strategy using network utility maximization (NUM) theory was proposed.First of all,the NUM model for channel resource allocation was introduced.A utility function reflecting vehicle’s safety requirements was proposed in the model.Then under the condition of fixed transmit powers,a optimization problem of channel resource allocation was proposed.Lastly,to solve the optimization problem,a distributed congestion control algorithm named utility-based rate congestion control (UBRCC) algorithm was designed,the algorithm worked out the optimal beaconing rate by updating vehicle’s congestion price,realizing the resource allocation according to vehicle’s safety requirements.Simulation results validate that UBRCC algorithm can efficiently control channel congestion,reduce transmission delay,ensure reliable data transmission and satisfies the requirements of safety applications.     

Advances in internet congestion control

In this survey, we first review the concept of congestion control with a focus on the Transmission Control Protocol⁄Internet Protocol (TCP⁄IP). We describe many recently proposed algorithms to combat congestion and improve performance, particularly active queue management (AQM) algorithms such as random early detection (RED) and its variants. We then survey control-theoretic analysis and design of TCP congestion control with an AQM scheme. In addition, we discuss three problems associated with AQM proposals: parameter setting, the insensitivity to the input traffic load variation, and the mismatch between macroscopic and microscopic behavior of queue length dynamics. As alternatives to AQM algorithms, we also survey architectural approaches such as modification of source or network algorithms, and economic approaches including pricing or optimization of allocated resources. Finally, we list many open issues that persist in the design, operation, and control of the Internet.     

Fair end-to-end window-based congestion control

In this paper, we demonstrate the existence of fair end-to-end window-based congestion control protocols for packet-switched networks with first come-first served routers. Our definition of fairness generalizes proportional fairness and includes arbitrarily close approximations of max-min fairness. The protocols use only information that is available to end hosts and are designed to converge reasonably fast. Our study is based on a multiclass fluid model of the network. The convergence of the protocols is proved using a Lyapunov function. The technical challenge is in the practical implementation of the protocols     

多播拥塞控制研究进展

讨论了多播拥塞控制的关键问题及各种解决方法，分析和比较了目前一些有代表性的多播拥塞控制算法，指出了其中存在的问题，并提出了未来的工作方向。     

On hop-by-hop rate-based congestion control

The activity in building gigabit speed networks has led many researchers to re-examine the issue of congestion control. We describe a rate-based hop-by-hop congestion control mechanism in which the service rates of connections are dynamically adjusted at a switch, using feedback information provided by the neighboring switches. The desired service rate is computed based on a control equation that utilizes a model of the system with feedback information used to correct inaccuracies in the model. We use an analytical model to prove that the expected value of the queue occupancy and throughput of a controlled connection converge to the desired operating point. We also study the variation of the queue occupancy and throughput in steady-state as well as the transient response. The analytical results provide insights into how the parameter values chosen affect performance. We use simulations to compare the performance of the scheme with an equivalent end-to-end control scheme. Our analytical and simulation results show that the hop-by-hop scheme reacts faster to changes in the traffic intensity and, consequently, utilizes resources at the bottleneck better and loses fewer packets than the end-to-end scheme     

Adaptive mean queue size and its rate of change: queue management with random dropping

The random early detection active queue management (AQM) scheme uses the average queue size to calculate the dropping probability in terms of minimum and maximum thresholds. The effect of heavy load enhances the frequency of crossing the maximum threshold value resulting in frequent dropping of the packets. An adaptive queue management with random dropping algorithm is proposed which incorporates information not just about the average queue size but also the rate of change of the same. Introducing an adaptively changing threshold level that falls in between lower and upper thresholds, our algorithm demonstrates that these additional features significantly improve the system performance in terms of throughput, average queue size, utilization and queuing delay in relation to the existing AQM algorithms.     

Fieldbus based distributed servo control using LonWorks/IP gateway/web servers

Virtual device network (VDN) is an intelligent integrated form of a device (control) network and IP network. If a fieldbus based distributed control system (DCS) is implemented on a global VDN, efficiency and flexibility can be significantly improved. In this study DCS implemented on the LonWorks/IP VDN is investigated with an example of model reference adaptive control (MRAC) of a geared DC motor. In order to compensate for the network induced uncertain time delay inherently present on VDN, the modified Smith predictor based internal model controller was integrated to MRAC (MRAC–IMC). The effectiveness of the proposed control scheme was tested through experiment. The proposed control scheme exhibited the robustness to noise and external disturbances and the good tracking performance around zero velocity point occurring due to overshoot and stick friction. Result of this study suggests that sophisticated servo control of dynamic systems is possible from a remote client PC on VDN by properly compensating the network delay.