Download or read book A Model based Approach to Clock Synchronization in Distributed Systems written by Joydeep Ganguly and published by . This book was released on 2000 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Wireless Networks Model and Optimization Based Approaches to Clock Synchronization Random Access MAC and Video Streaming written by Nikolaos M. Freris and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We, via a model and optimization-based approach, address three issues related to wireless networks: clock synchronization, medium access control (MAC) and scalable video streaming. In Chapter 2 we develop, study and simulate a new model-based distributed network clock synchronization protocol. In a network of clocks, a given node is taken as reference and is associated with the time evolution t. We introduce and analyze a stochastic model for clocks, in which the relative speedup of a clock with respect to the reference node, called the skew, is characterized by an exponential transformation of an Orstein-Uhlenbeck process. We study the properties of our model, namely moment and sample path properties of the stochastic processes, and calculate its Allan variance. We show how our model can be used to translate the time of a clock to another clock's units. We study the problem of synchronizing clocks in a network, which amounts to estimating the instantaneous relative skews and relative offsets, i.e., the differences in the clock readouts, by exchange of time-stamped packets between pairs of nodes in the network. Based on a stochastic model for delays, we derive a scheme for obtaining relative skew measurements in a communication link by sending two time-stamped packets from node i to node j in order to obtain a noisy measurement of their relative skew. We develop an algorithm for filtering relative skew measurements across a link (i,j) in order to estimate the logarithm of the relative skew. We study the properties of the algorithms and provide theoretical guarantees on their performance. We also develop an online, centralized, model-based, asynchronous skew estimation algorithm for optimal filtering of the time-stamps in the entire network, as well as an efficient distributed suboptimal scheme which demonstrates near-optimal performance in simulations. Furthermore, we study some implementation issues, and present a scheme for pairwise relative offset estimation given skew estimates. We use the distributed asynchronous algorithm to obtain nodal offset estimates from relative offset estimates. We combine our findings into developing a new protocol for clock synchronization, namely the Model-Based Clock Synchronization Protocol (MBCSP). We present a comparative simulation study of its performance versus the leading scheme by Solis et al. (2006); the results show that MBCSP performs better in terms of skew, offset and delay estimation. Finally, we have performed trace-driven simulation based on time-stamps obtained from Berkeley motes. Our scheme outperforms that of Solis et al. by 45%, where we used the accuracy in predicting the receipt time-stamp at the sender as the clock synchronization metric. In Chapter 3, we study random access based MAC in the framework of network utility maximization (NUM). There has been much recent interest in protocol design for wireless networks based on maximizing a network utility function. A significant advance is the observation that a decomposition of the Lagrangian suggests an approach where transmissions are scheduled to minimize back-pressure. However, a satisfactory MAC protocol that can realize such a scheduling algorithm is notably missing, and we develop one potential scheme. We present a candidate random access MAC protocol that extends an existing algorithm by Gupta and Stolyar (2006) in calculating the access probabilities. We also consider the online adaptation of access probabilities using local information about queue lengths and active links. We provide OPNET simulation results to compare the performance of our scheme with the leading schemes. We estimate the capacity region of our scheme by simulation for various topologies and multiple flows. Our simulation studies indicate that our extension in conjunction with an implementation of back-pressure significantly outperforms the slotted-time algorithm of Gupta and Stolyar (2006). In Chapter 4, we present performance bounds for random access based MAC using carrier-sense multiple access (CSMA). In recent work, it was shown that a distributed CSMA-based MAC protocol is throughput-optimal which, in turn, implies that the class of controlled distributed random access MAC protocols can support the entire capacity region. It is challenging to study the performance of such schemes in terms of mean delays and compare it with some known results on the performance of centralized scheduling. We modify the model of Jiang and Walrand (2008) to obtain Markov chain models that incorporate the queue lengths as well as the information about the independent set, for single-hop networks. We show that the delay of the new models yields an upper bound on the delay of the original models. We derive upper and lower bounds on the mean total delay at the steady-state, and show that these bounds coincide with those for max-weight scheduling. Finally, we develop a method of deriving upper and lower bounds for random-access schemes by using linear programs (LPs). We present an optimization program for minimizing the upper bounds. In Chapter 5, we consider multihomed scalable video streaming systems where each video is concurrently transmitted over several access networks to a client. The problem is to determine which video packets of a video stream to transmit, and associate each video packet with an access network, so that the video quality at the client is maximized under measured network conditions. We present a network model and a video distortion model to capture the network conditions and video distortion characteristics, respectively. We develop a mathematical formulation to find the streaming strategy for maximizing the average video quality at the client. While the formulation can be optimally solved using exhaustive search or dynamic programming, doing so takes a prohibitively long time, and is not practical for real-time video streaming servers. In order to efficiently solve the problem in real time, we propose several suboptimal convex problems along with two heuristic algorithms. We conduct extensive trace-driven simulations to evaluate the algorithms using real network conditions and actual scalable video streams. We compare our algorithms against the rate control algorithms defined in the Datagram Congestion Control Protocol (DCCP) standard. The simulation results show that our algorithms significantly outperform current systems while being TCP-friendly. For example, compared to DCCP, our algorithms achieve at least 10 dB quality improvement and result in up to 83% packet delivery delay reduction. Finally, we study the trade-off between efficiency and optimality: One of the heuristic algorithms runs faster and is suitable for large-scale streaming systems, while the other one achieves better video quality and is more appropriate for smaller streaming servers. The convex programming approach demonstrates a good trade-off between running time and performance.
Download or read book Clock synchronization in distributed systems a comparison written by Harald Bachner and published by GRIN Verlag. This book was released on 2007-03-01 with total page 35 pages. Available in PDF, EPUB and Kindle. Book excerpt: Bachelor Thesis from the year 2007 in the subject Computer Science - Technical Computer Science, grade: 1,0, University of Applied Sciences Technikum Vienna (Informations- und Kommunikationssysteme), language: English, abstract: Clock synchronization is a necessary and critical part in most distributed systems. For many years NTP was the state-of-the-art way of synchronizing computer clocks distributed in space. However, as recent advances in miniaturization lead to the construction of smaller, more powerful and less power consuming computers, embedded devices, sensors and actuators, the need for more precise time synchronization grew. This work thus sets out to compare selected approaches to clock synchronization in distributed systems. The well known Global Positioning System is disseminating accurate time and frequency information from the International Institutes that keep the time, NTP can still do the same, but at different levels of accuracy as well as cost. Clock synchronization protocols like IEEE1588 or TTP and bus architectures like FlexRay evolved from the need to further propagate the timing information within small networks and therefore staying within the specified limits of preciseness.
Download or read book Clock Synchronization in Distributed Systems a Comparison written by Harald Bachner and published by GRIN Verlag. This book was released on 2007-07-26 with total page 73 pages. Available in PDF, EPUB and Kindle. Book excerpt: Bachelor Thesis from the year 2007 in the subject Computer Science - Technical Computer Science, grade: 1,0, University of Applied Sciences Technikum Vienna (Informations- und Kommunikationssysteme), 29 entries in the bibliography, language: English, abstract: Clock synchronization is a necessary and critical part in most distributed systems. For many years NTP was the state-of-the-art way of synchronizing computer clocks distributed in space. However, as recent advances in miniaturization lead to the construction of smaller, more powerful and less power consuming computers, embedded devices, sensors and actuators, the need for more precise time synchronization grew. This work thus sets out to compare selected approaches to clock synchronization in distributed systems. The well known Global Positioning System is disseminating accurate time and frequency information from the International Institutes that keep the time, NTP can still do the same, but at different levels of accuracy as well as cost. Clock synchronization protocols like IEEE1588 or TTP and bus architectures like FlexRay evolved from the need to further propagate the timing information within small networks and therefore staying within the specified limits of preciseness.
Download or read book Times estimates and clock synchronization in distributed systems written by Cheeha Kim and published by . This book was released on 1989 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: "This paper presents a simple and efficient solution to the problem of estimating the correct time in distributed systems. Based on a clock model consisting of an offset and a rate, the estimating process is constructed. Various simulation results show that the method enables to achieve clock synchronization precision superior to those obtained by previously published clock synchronization algorithms."
Download or read book System Design Modeling and Simulation written by Claudius Ptolemaeus and published by Lee & Seshia. This book was released on 2013-09-27 with total page 687 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is a definitive introduction to models of computation for the design of complex, heterogeneous systems. It has a particular focus on cyber-physical systems, which integrate computing, networking, and physical dynamics. The book captures more than twenty years of experience in the Ptolemy Project at UC Berkeley, which pioneered many design, modeling, and simulation techniques that are now in widespread use. All of the methods covered in the book are realized in the open source Ptolemy II modeling framework and are available for experimentation through links provided in the book. The book is suitable for engineers, scientists, researchers, and managers who wish to understand the rich possibilities offered by modern modeling techniques. The goal of the book is to equip the reader with a breadth of experience that will help in understanding the role that such techniques can play in design.
Download or read book Large Scale Distributed Computing and Applications Models and Trends written by Cristea, Valentin and published by IGI Global. This book was released on 2010-05-31 with total page 276 pages. Available in PDF, EPUB and Kindle. Book excerpt: Many applications follow the distributed computing paradigm, in which parts of the application are executed on different network-interconnected computers. The extension of these applications in terms of number of users or size has led to an unprecedented increase in the scale of the infrastructure that supports them. Large-Scale Distributed Computing and Applications: Models and Trends offers a coherent and realistic image of today's research results in large scale distributed systems, explains state-of-the-art technological solutions for the main issues regarding large scale distributed systems, and presents the benefits of using large scale distributed systems and the development process of scientific and commercial distributed applications.
Download or read book DISTRIBUTED OPERATING SYSTEMS written by PRADEEP K. SINHA and published by PHI Learning Pvt. Ltd.. This book was released on 1998-01-01 with total page 761 pages. Available in PDF, EPUB and Kindle. Book excerpt: The highly praised book in communications networking from IEEE Press, now available in the Eastern Economy Edition.This is a non-mathematical introduction to Distributed Operating Systems explaining the fundamental concepts and design principles of this emerging technology. As a textbook for students and as a self-study text for systems managers and software engineers, this book provides a concise and an informal introduction to the subject.
Download or read book Design and Simulation of Clock Synchronization in Distributed Systems written by Anton V. Schedl and published by . This book was released on 1996 with total page 230 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Distributed Computing written by Hagit Attiya and published by John Wiley & Sons. This book was released on 2004-03-25 with total page 440 pages. Available in PDF, EPUB and Kindle. Book excerpt: * Comprehensive introduction to the fundamental results in the mathematical foundations of distributed computing * Accompanied by supporting material, such as lecture notes and solutions for selected exercises * Each chapter ends with bibliographical notes and a set of exercises * Covers the fundamental models, issues and techniques, and features some of the more advanced topics
Download or read book Clock Synchronization in Distributed Systems written by Martin Horauer and published by Sudwestdeutscher Verlag Fur. This book was released on 2009 with total page 132 pages. Available in PDF, EPUB and Kindle. Book excerpt: A system-wide global time base with known precision is frequently of pivotal importance for the design and operation of distributed systems and services. The requirements and the large scale often demand a high-precision below the microsecond-range. The IEEE-1588 standard addresses these issues and proposes ways for a suitable implementation. Complementing these solutions, an alternative architecture for network interfaces and networked devices is proposed that renders a worst-case precision in the 100 ns-range possible. Furthermore, an analysis and an experimental evaluation reveals actual values for the worst-case precision that might be achieved.
Download or read book ECAI 2008 written by European Coordinating Committee for Artificial Intelligence and published by IOS Press. This book was released on 2008 with total page 972 pages. Available in PDF, EPUB and Kindle. Book excerpt: Includes subconference "Prestigious Applications of Intelligent Systems (PAIS 2008)."
Download or read book Distributed System Design written by Jie Wu and published by CRC Press. This book was released on 2017-12-14 with total page 488 pages. Available in PDF, EPUB and Kindle. Book excerpt: Future requirements for computing speed, system reliability, and cost-effectiveness entail the development of alternative computers to replace the traditional von Neumann organization. As computing networks come into being, one of the latest dreams is now possible - distributed computing. Distributed computing brings transparent access to as much computer power and data as the user needs for accomplishing any given task - simultaneously achieving high performance and reliability. The subject of distributed computing is diverse, and many researchers are investigating various issues concerning the structure of hardware and the design of distributed software. Distributed System Design defines a distributed system as one that looks to its users like an ordinary system, but runs on a set of autonomous processing elements (PEs) where each PE has a separate physical memory space and the message transmission delay is not negligible. With close cooperation among these PEs, the system supports an arbitrary number of processes and dynamic extensions. Distributed System Design outlines the main motivations for building a distributed system, including: inherently distributed applications performance/cost resource sharing flexibility and extendibility availability and fault tolerance scalability Presenting basic concepts, problems, and possible solutions, this reference serves graduate students in distributed system design as well as computer professionals analyzing and designing distributed/open/parallel systems. Chapters discuss: the scope of distributed computing systems general distributed programming languages and a CSP-like distributed control description language (DCDL) expressing parallelism, interprocess communication and synchronization, and fault-tolerant design two approaches describing a distributed system: the time-space view and the interleaving view mutual exclusion and related issues, including election, bidding, and self-stabilization prevention and detection of deadlock reliability, safety, and security as well as various methods of handling node, communication, Byzantine, and software faults efficient interprocessor communication mechanisms as well as these mechanisms without specific constraints, such as adaptiveness, deadlock-freedom, and fault-tolerance virtual channels and virtual networks load distribution problems synchronization of access to shared data while supporting a high degree of concurrency
Download or read book Distributed Systems written by Sukumar Ghosh and published by CRC Press. This book was released on 2006-11-22 with total page 422 pages. Available in PDF, EPUB and Kindle. Book excerpt: Most applications in distributed computing center around a set of common subproblems. Distributed Systems: An Algorithmic Approach presents the algorithmic issues and necessary background theory that are needed to properly understand these challenges. Achieving a balance between theory and practice, this book bridges the gap betwee
Download or read book Concurrency Control in Distributed System Using Mutual Exclusion written by Sukhendu Kanrar and published by Springer. This book was released on 2017-08-04 with total page 104 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book presents various state-of-the-art approaches for process synchronization in a distributed environment. The range of algorithms discussed in the book starts from token based mutual exclusion algorithms that work on tree based topology. Then there are interesting solutions for more flexible logical topology like a directed graph, with or without cycle. In a completely different approach, one of the chapters presents two recent voting-based DME algorithms. All DME algorithms presented in the book aim to ensure fairness in terms of first come first serve (FCFS) order among equal priority processes. At the same time, the solutions consider the priority of the requesting processes and allocate resource for the earliest request when no such request from a higher priority process is pending.
Download or read book Design and Development of an Efficient Process Synchronization Algorithm for Distributed and Network Systems written by Girija S. Chavala and published by . This book was released on 1995 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Global States and Time in Distributed Systems written by T. Anthony Marsland and published by Institute of Electrical & Electronics Engineers(IEEE). This book was released on 1994 with total page 172 pages. Available in PDF, EPUB and Kindle. Book excerpt: Selected papers on global states and time in distributed systems. Among the topics: synchronizing clocks in the presence of faults, Internet time synchronization, and virtual time and global state in distributed systems. Includes an annotated bibliography of principal associated works. No index. Ann
