Download or read book Active Queue Management Methods in Computer Communication Networks Based on Pole Placement and H infinity Optimal Control written by Qiang Chen and published by . This book was released on 2006 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis studies the control of TCP traffic in the Internet nowadays. Both classical and modern control theory are used to design the controllers for the TCP/AQM system. For the classical control theoretical approaches, we revisit the simple pole placement technique, and exploit this technique to propose four kinds of controllers for active queue management (AQM) in IP routers: the Proportional controller based on Pole Placement (the P_PP controller), the Proportional-plus-integral controller based on Pole Placement (the PI_PP controller), the Self Tuning Proportional controller based on Pole Placement (the ST_P_PP controller), and the Self-Tuning Proportional-plus-Integral controller based on Pole Placement (the ST_PI_PP controller). The transient performance indices--the damping ratio xi and the undamped natural frequency on, are appropriately chosen such that: (a) the transient response of the system is satisfied; (b) all the poles lie in the left-half of the s-plane to guarantee the stability of the system. The self-tuning controllers (the ST_P_PP and the ST_PI_PP) can maintain on-line tuning of the controller parameters so that good system performance can be ensured even under significant load changes. This thesis also investigates the application of a robust modern control technique-- Hinfinity optimal control to the AQM controller. Two Hinfinity loop-shaping techniques, the S/U Mixed Sensitivity Problem (MSP) and the S/T/U MSP are applied to the controller design. Different weight functions and their impacts on the system performance are discussed and evaluated. Finally, by modeling the uncertainties in the TCP/AQM system in terms of the uncertainty weight, this thesis also designs a robust AQM controller based on a modern control technique--robust mu analysis. The controller is synthesized by approximating the mu-optimal control problem with the Hinfinity S/T/U MSP. The NP (Nominal Performance), the RS (Robust Stability) and the RP (Robust Performance) of the system under the synthesized controller are analyzed using the mu analysis technique.

Download or read book Dissertation Abstracts International written by and published by . This book was released on 2007 with total page 902 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Performance Modelling and Evaluation of Active Queue Management Techniques in Communication Networks written by Hussein F. Abdel-Jaber and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Since the field of computer networks has rapidly grown in the last two decades, congestion control of traffic loads within networks has become a high priority. Congestion occurs in network routers when the number of incoming packets exceeds the available network resources, such as buffer space and bandwidth allocation. This may result in a poor network performance with reference to average packet queueing delay, packet loss rate and throughput. To enhance the performance when the network becomes congested, several different active queue management (AQM) methods have been proposed and some of these are discussed in this thesis. Specifically, these AQM methods are surveyed in detail and their strengths and limitations are highlighted. A comparison is conducted between five known AQM methods, Random Early Detection (RED), Gentle Random Early Detection (GRED), Adaptive Random Early Detection (ARED), Dynamic Random Early Drop (DRED) and BLUE, based on several performance measures, including mean queue length, throughput, average queueing delay, overflow packet loss probability, packet dropping probability and the total of overflow loss and dropping probabilities for packets, with the aim of identifying which AQM method gives the most satisfactory results of the performance measures. This thesis presents a new AQM approach based on the RED algorithm that determines and controls the congested router buffers in an early stage. This approach is called Dynamic RED (REDD), which stabilises the average queue length between minimum and maximum threshold positions at a certain level called the target level to prevent building up the queues in the router buffers. A comparison is made between the proposed REDD, RED and ARED approaches regarding the above performance measures. Moreover, three methods based on RED and fuzzy logic are proposed to control the congested router buffers incipiently. These methods are named REDD1, REDD2, and REDD3 and their performances are also compared with RED using the above performance measures to identify which method achieves the most satisfactory results. Furthermore, a set of discrete-time queue analytical models are developed based on the following approaches: RED, GRED, DRED and BLUE, to detect the congestion at router buffers in an early stage. The proposed analytical models use the instantaneous queue length as a congestion measure to capture short term changes in the input and prevent packet loss due to overflow. The proposed analytical models are experimentally compared with their corresponding AQM simulations with reference to the above performance measures to identify which approach gives the most satisfactory results. The simulations for RED, GRED, ARED, DRED, BLUE, REDD, REDD1, REDD2 and REDD3 are run ten times, each time with a change of seed and the results of each run are used to obtain mean values, variance, standard deviation and 95% confidence intervals. The performance measures are calculated based on data collected only after the system has reached a steady state. After extensive experimentation, the results show that the proposed REDD, REDD1, REDD2 and REDD3 algorithms and some of the proposed analytical models such as DRED-Alpha, RED and GRED models offer somewhat better results of mean queue length and average queueing delay than these achieved by RED and its variants when the values of packet arrival probability are greater than the value of packet departure probability, i.e. in a congestion situation. This suggests that when traffic is largely of a non bursty nature, instantaneous queue length might be a better congestion measure to use rather than the average queue length as in the more traditional models.

Download or read book Active Queue Management Control in Communication Networks written by Manfredi Sabato and published by . This book was released on 2004 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Heavy Traffic Analysis of Controlled Queueing and Communication Networks written by Harold Kushner and published by Springer. This book was released on 2013-11-17 with total page 515 pages. Available in PDF, EPUB and Kindle. Book excerpt: One of the first books in the timely and important area of heavy traffic analysis of controlled and uncontrolled stochastics networks, by one of the leading authors in the field. The general theory is developed, with possibly state dependent parameters, and specialized to many different cases of practical interest.

Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1992 with total page 1572 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Introduction to Queueing Networks written by Erol Gelenbe and published by John Wiley & Sons. This book was released on 1987 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mathematics of Computing -- Miscellaneous.

Download or read book Computer Networks written by Larry L. Peterson and published by Elsevier. This book was released on 2011-03-02 with total page 921 pages. Available in PDF, EPUB and Kindle. Book excerpt: Computer Networks: A Systems Approach, Fifth Edition, explores the key principles of computer networking, with examples drawn from the real world of network and protocol design. Using the Internet as the primary example, this best-selling and classic textbook explains various protocols and networking technologies. The systems-oriented approach encourages students to think about how individual network components fit into a larger, complex system of interactions. This book has a completely updated content with expanded coverage of the topics of utmost importance to networking professionals and students, including P2P, wireless, network security, and network applications such as e-mail and the Web, IP telephony and video streaming, and peer-to-peer file sharing. There is now increased focus on application layer issues where innovative and exciting research and design is currently the center of attention. Other topics include network design and architecture; the ways users can connect to a network; the concepts of switching, routing, and internetworking; end-to-end protocols; congestion control and resource allocation; and end-to-end data. Each chapter includes a problem statement, which introduces issues to be examined; shaded sidebars that elaborate on a topic or introduce a related advanced topic; What's Next? discussions that deal with emerging issues in research, the commercial world, or society; and exercises. This book is written for graduate or upper-division undergraduate classes in computer networking. It will also be useful for industry professionals retraining for network-related assignments, as well as for network practitioners seeking to understand the workings of network protocols and the big picture of networking. - Completely updated content with expanded coverage of the topics of utmost importance to networking professionals and students, including P2P, wireless, security, and applications - Increased focus on application layer issues where innovative and exciting research and design is currently the center of attention - Free downloadable network simulation software and lab experiments manual available

Download or read book Some Active Queue Management Methods for Controlling Packet Queueing Delay written by Mahmud H. Etbega Mohamed and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Traditionally the Internet is used for the following applications: FTP, e-mail and Web traffic. However in the recent years the Internet is increasingly supporting emerging applications such as IP telephony, video conferencing and online games. These new applications have different requirements in terms of throughput and delay than traditional applications. For example, interactive multimedia applications, unlike traditional applications, have more strict delay constraints and less strict loss constraints. Unfortunately, the current Internet offers only a best-effort service to all applications without any consideration to the applications specific requirements. In this thesis three existing Active Queue Management (AQM) mechanisms are modified by incorporating into these a control function to condition routers for better Quality of Service (QoS). Specifically, delay is considered as the key QoS metric as it is the most important metric for real-time multimedia applications. The first modified mechanism is Drop Tail (DT), which is a simple mechanism in comparison with most AQM schemes. A dynamic threshold has been added to DT in order to maintain packet queueing delay at a specified value. The modified mechanism is referred to as Adaptive Drop Tail (ADT). The second mechanism considered is Early Random Drop (ERD) and, iii in a similar way to ADT, a dynamic threshold has been used to keep the delay at a required value, the main difference being that packets are now dropped probabilistically before the queue reaches full capacity. This mechanism is referred to as Adaptive Early Random Drop (AERD). The final mechanism considered is motivated by the well known Random Early Detection AQM mechanism and is effectively a multi-threshold version of AERD in which packets are dropped with a linear function between the two thresholds and the second threshold is moveable in order to change the slope of the dropping function. This mechanism is called Multi Threshold Adaptive Early Random Drop (MTAERD) and is used in a similar way to the other mechanisms to maintain delay around a specified level. The main focus with all the mechanisms is on queueing delay, which is a significant component of end-to-end delay, and also on reducing the jitter (delay variation) A control algorithm is developed using an analytical model that specifies the delay as a function of the queue threshold position and this function has been used in a simulation to adjust the threshold to an effective value to maintain the delay around a specified value as the packet arrival rate changes over time. iv A two state Markov Modulated Poisson Process is used as the arrival process to each of the three systems to introduce burstiness and correlation of the packet inter-arrival times and to present sudden changes in the arrival process as might be encountered when TCP is used as the transport protocol and step changes the size of its congestion window. In the investigations it is assumed the traffic source is a mixture of TCP and UDP traffic and that the mechanisms conserved apply to the TCP based data. It is also assumed that this consists of the majority proportion of the total traffic so that the control mechanisms have a significant effect on controlling the overall delay. The three mechanisms are evaluated using a Java framework and results are presented showing the amount of improvement in QoS that can be achieved by the mechanisms over their non-adaptive counterparts. The mechanisms are also compared with each other and conclusions drawn.

Download or read book Delay oriented Active Queue Management in TCP IP Networks written by Bo Yu and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Internet-based applications and services are pervading everyday life. Moreover, the growing popularity of real-time, time-critical and mission-critical applications set new challenges to the Internet community. The requirement for reducing response time, and therefore latency control is increasingly emphasized. This thesis seeks to reduce queueing delay through active queue management. While mathematical studies and research simulations reveal that complex trade-off relationships exist among performance indices such as throughput, packet loss ratio and delay, etc., this thesis intends to find an improved active queue management algorithm which emphasizes delay control without trading much on other performance indices such as throughput and packet loss ratio. The thesis observes that in TCP/IP network, packet loss ratio is a major reflection of congestion severity or load. With a properly functioning active queue management algorithm, traffic load will in general push the feedback system to an equilibrium point in terms of packet loss ratio and throughput. On the other hand, queue length is a determinant factor on system delay performance while has only a slight influence on the equilibrium. This observation suggests the possibility of reducing delay while maintaining throughput and packet loss ratio relatively unchanged. The thesis also observes that queue length fluctuation is a reflection of both load changes and natural fluctuation in arriving bit rate. Monitoring queue length fluctuation alone cannot distinguish the difference and identify congestion status; and yet identifying this difference is crucial in finding out situations where average queue size and hence queueing delay can be properly controlled and reasonably reduced. However, many existing active queue management algorithms only monitor queue length, and their control policies are solely based on this measurement. In our studies, our novel finding is that the arriving bit rate distribution of all sources contains information which can be a better indication of congestion status and has a correlation with traffic burstiness. And this thesis develops a simple and scalable way to measure its two most important characteristics, namely the mean ii and the variance of the arriving rate distribution. The measuring mechanism is based on a Zombie List mechanism originally proposed and deployed in Stabilized RED to estimate the number of flows and identify misbehaving flows. This thesis modifies the original zombie list measuring mechanism, makes it capable of measuring additional variables. Based on these additional measurements, this thesis proposes a novel modification to the RED algorithm. It utilizes a robust adaptive mechanism to ensure that the system reaches proper equilibrium operating points in terms of packet loss ratio and queueing delay under various loads. Furthermore, it identifies different congestion status where traffic is less bursty and adapts RED parameters in order to reduce average queue size and hence queueing delay accordingly. Using ns-2 simulation platform, this thesis runs simulations of a single bottleneck link scenario which represents an important and popular application scenario such as home access network or SoHo. Simulation results indicate that there are complex trade-off relationships among throughput, packet loss ratio and delay; and in these relationships delay can be substantially reduced whereas trade-offs on throughput and packet loss ratio are negligible. Simulation results show that our proposed active queue management algorithm can identify circumstances where traffic is less bursty and actively reduce queueing delay with hardly noticeable sacrifice on throughput and packet loss ratio performances. In conclusion, our novel approach enables the application of adaptive techniques to more RED parameters including those affecting queue occupancy and hence queueing delay. The new modification to RED algorithm is a scalable approach and does not introduce additional protocol overhead. In general it brings the benefit of substantially reduced delay at the cost of limited processing overhead and negligible degradation in throughput and packet loss ratio. However, our new algorithm is only tested on responsive flows and a single bottleneck scenario. Its effectiveness on a combination of responsive and non-responsive flows as well as in more complicated network topology scenarios is left for future work.

Download or read book Active Queue Management and Scheduling Methods for Packet switched Networks written by Ozdemir Akin and published by . This book was released on 2004 with total page 101 pages. Available in PDF, EPUB and Kindle. Book excerpt: Keywords: quality of service, TCP/IP, scheduling, active queue management.

Download or read book Active Queue Management and Scheduling Methods for Packet Switched Networks written by and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: To support the myriad of envisioned communication products of the future, there is a need to develop a network infrastructure that can provide larger bandwidth, with better control of quality of service (QoS). However, with increasing demand for applications running over packet networks, congestion at the intermediate nodes (e.g., routers and switches) can be a serious problem. Consequences include long delays, large delay variation and high packet loss rates. Different solutions requiring varying levels of modification to the currently used algorithms have been proposed both for responsive (e.g., TCP) and unresponsive (e.g., UDP) protocols. However, most of the solutions are either too complicated to implement in real life or not general enough to be applicable to an arbitrary network topology. In this thesis, we investigate two mechanisms - active queue management (AQM), and scheduling - that can improve QoS in the packet networks. AQM techniques attempt to prevent congestion and regulate the queue length by sending congestion signals (i.e., dropping and/or marking packets) in a proactive manner, which would eventually cause the senders to decrease their sending rates. We use an analytic model derived for TCP in the literature to develop an AQM scheme that not only controls the queue length at the intermediate nodes but also distributes the resources fairly between the users. We present two different schemes that have different levels of complexity and performance. We also propose a distributed networking scheme that improves the performance of our new AQM algorithms. Although AQM schemes work well with responsive protocols such as TCP, the performance degrades for unresponsive protocols since unresponsive protocols do not change their packet sending rate in response to the congestion notifications sent by the network. Scheduling algorithms can regulate both responsive and unresponsive flows and can also provide guarantees on some QoS parameters, such as latency a.

Download or read book Delay oriented Active Queue Management in TCP written by Bo Yu and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Internet-based applications and services are pervading everyday life. Moreover, the growing popularity of real-time, time-critical and mission-critical applications set new challenges to the Internet community. The requirement for reducing response time, and therefore latency control is increasingly emphasized. This thesis seeks to reduce queueing delay through active queue management. While mathematical studies and research simulations reveal that complex trade-off relationships exist among performance indices such as throughput, packet loss ratio and delay, etc., this thesis intends to find an improved active queue management algorithm which emphasizes delay control without trading much on other performance indices such as throughput and packet loss ratio. The thesis observes that in TCP/IP network, packet loss ratio is a major reflection of congestion severity or load. With a properly functioning active queue management algorithm, traffic load will in general push the feedback system to an equilibrium point in terms of packet loss ratio and throughput. On the other hand, queue length is a determinant factor on system delay performance while has only a slight influence on the equilibrium. This observation suggests the possibility of reducing delay while maintaining throughput and packet loss ratio relatively unchanged. The thesis also observes that queue length fluctuation is a reflection of both load changes and natural fluctuation in arriving bit rate. Monitoring queue length fluctuation alone cannot distinguish the difference and identify congestion status; and yet identifying this difference is crucial in finding out situations where average queue size and hence queueing delay can be properly controlled and reasonably reduced. However, many existing active queue management algorithms only monitor queue length, and their control policies are solely based on this measurement. In our studies, our novel finding is that the arriving bit rate distribution of all sources contains information which can be a better indication of congestion status and has a correlation with traffic burstiness. And this thesis develops a simple and scalable way to measure its two most important characteristics, namely the mean ii and the variance of the arriving rate distribution. The measuring mechanism is based on a Zombie List mechanism originally proposed and deployed in Stabilized RED to estimate the number of flows and identify misbehaving flows. This thesis modifies the original zombie list measuring mechanism, makes it capable of measuring additional variables. Based on these additional measurements, this thesis proposes a novel modification to the RED algorithm. It utilizes a robust adaptive mechanism to ensure that the system reaches proper equilibrium operating points in terms of packet loss ratio and queueing delay under various loads. Furthermore, it identifies different congestion status where traffic is less bursty and adapts RED parameters in order to reduce average queue size and hence queueing delay accordingly. Using ns-2 simulation platform, this thesis runs simulations of a single bottleneck link scenario which represents an important and popular application scenario such as home access network or SoHo. Simulation results indicate that there are complex trade-off relationships among throughput, packet loss ratio and delay; and in these relationships delay can be substantially reduced whereas trade-offs on throughput and packet loss ratio are negligible. Simulation results show that our proposed active queue management algorithm can identify circumstances where traffic is less bursty and actively reduce queueing delay with hardly noticeable sacrifice on throughput and packet loss ratio performances. In conclusion, our novel approach enables the application of adaptive techniques to more RED parameters including those affecting queue occupancy and hence queueing delay. The new modification to RED algorithm is a scalable approach and does not introduce additional protocol overhead. In general it brings the benefit of substantially reduced delay at the cost of limited processing overhead and negligible degradation in throughput and packet loss ratio. However, our new algorithm is only tested on responsive flows and a single bottleneck scenario. Its effectiveness on a combination of responsive and non-responsive flows as well as in more complicated network topology scenarios is left for future work.

Download or read book Performance Modeling and Analysis of Communication Networks written by Phuoc Tran-Gia and published by BoD – Books on Demand. This book was released on 2021-10-12 with total page 370 pages. Available in PDF, EPUB and Kindle. Book excerpt: This textbook provides an introduction to common methods of performance modeling and analysis of communication systems. These methods form the basis of traffic engineering, teletraffic theory, and analytical system dimensioning. The fundamentals of probability theory, stochastic processes, Markov processes, and embedded Markov chains are presented. Basic queueing models are described with applications in communication networks. Advanced methods are presented that have been frequently used in recent practice, especially discrete-time analysis algorithms, or which go beyond classical performance measures such as Quality of Experience or energy efficiency. Recent examples of modern communication networks include Software Defined Networking and the Internet of Things. Throughout the book, illustrative examples are used to provide practical experience in performance modeling and analysis. Target group: The book is aimed at students and scientists in computer science and technical computer science, operations research, electrical engineering and economics.

Download or read book Feedback Systems written by Karl Johan Åström and published by Princeton University Press. This book was released on 2021-02-02 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The essential introduction to the principles and applications of feedback systems—now fully revised and expanded This textbook covers the mathematics needed to model, analyze, and design feedback systems. Now more user-friendly than ever, this revised and expanded edition of Feedback Systems is a one-volume resource for students and researchers in mathematics and engineering. It has applications across a range of disciplines that utilize feedback in physical, biological, information, and economic systems. Karl Åström and Richard Murray use techniques from physics, computer science, and operations research to introduce control-oriented modeling. They begin with state space tools for analysis and design, including stability of solutions, Lyapunov functions, reachability, state feedback observability, and estimators. The matrix exponential plays a central role in the analysis of linear control systems, allowing a concise development of many of the key concepts for this class of models. Åström and Murray then develop and explain tools in the frequency domain, including transfer functions, Nyquist analysis, PID control, frequency domain design, and robustness. Features a new chapter on design principles and tools, illustrating the types of problems that can be solved using feedback Includes a new chapter on fundamental limits and new material on the Routh-Hurwitz criterion and root locus plots Provides exercises at the end of every chapter Comes with an electronic solutions manual An ideal textbook for undergraduate and graduate students Indispensable for researchers seeking a self-contained resource on control theory

Download or read book Performance of Computer Communication Systems written by Boudewijn R. Haverkort and published by John Wiley & Sons. This book was released on 1998-12-04 with total page 528 pages. Available in PDF, EPUB and Kindle. Book excerpt: Performance of Computer Communication Systems A Model-Based Approach Boudewijn R. Haverkort Rheinisch-Westfälische Technische Hochschule Aachen, Germany Computer communication systems and distributed systems are now able to provide an increasing range of services. As the timing requirements in the operation of these services are becoming crucial for the global community. performance assessment and selection of communication and distributed systems are, therefore, becoming more important. In this book, the author illustrates the techniques and methods used to evaluate the performance of computer communication systems, thereby covering all aspects of model-based performance evaluation. Unlike other books on this topic, there is no restriction to a particular performance evaluation technique. Notable features in this book include: * coverage of all major techniques of performance evaluation * non-mathematical problem solving approach, explaining and illustrating performance evaluation techniques * assessment techniques for stochastic processes, single server queues, networks of queues and stochastic Petri nets * numerous application studies, including token ring systems, client-server systems, and wide-area networks * substantial number of practical exercises and examples. For computer or electrical engineers who design and implement computer communication systems, this book provides an excellent overview of the methods and techniques used to construct and solve performance models. It is also a valuable source of information for postgraduate students in computer science and related subjects. Visit Our Web Page! http://www.wiley.com/

Download or read book Software Defined Networks written by Larry Peterson and published by . This book was released on 2021-02 with total page 154 pages. Available in PDF, EPUB and Kindle. Book excerpt: Software-Defined Networks (SDN) are transforming the Internet by replacing bundled, proprietary hardware and control software. SDN is being embraced by cloud providers, telcos, and enterprises, as it enables a new era of innovation in networking. This book provides a comprehensive introduction to SDN from the perspective of those who are developing and leveraging the technology. Book Features: Describes a complete SDN stack, illustrated with example open source software. Emphasizes underlying concepts, abstractions, and design rationale. Describes both fixed-function and programmable switching chips. Describes the P4-based toolchain for programming and controlling switches. Describes a range of SDN use cases: enterprises, datacenters, access networks. Includes hands-on programming exercises, downloadable fro GitHub.