Distributed simulation is an enabling concept to support the networked interaction of models and real world elements that are geographically distributed. This technology has brought a new set of challenging problems to solve, such as Data Distribution Management (DDM). The aim of DDM is to limit and control the volume of the data exchanged during a distributed simulation, and reduce the processing requirements of the simulation hosts by relaying events and state information only to those applications that require them. In this thesis, we propose a new DDM scheme, which we refer to as dynamic grid-based DDM. A lightweight UNT-RTI has been developed and implemented to investigate the performance of our DDM scheme. Our results clearly indicate that our scheme is scalable and it significantly reduces both the number of multicast groups used, and the message overhead, when compared to previous grid-based allocation schemes using large-scale and real-world scenarios.

It is expected that the grid of the future differs from the current system by the increased integration of distributed generation, distributed storage, demand response, power electronics, and communications and sensing technologies. The consequence is that the physical structure of the system becomes significantly more distributed. The existing centralized control structure is not suitable any more to operate such a highly distributed system. This thesis is dedicated to providing a promising solution to a class of energy management problems in power systems with a high penetration of distributed resources. This class includes optimal dispatch problems such as optimal power flow, security constrained optimal dispatch, optimal power flow control and coordinated plug-in electric vehicles charging. Our fully distributed algorithm not only handles the computational complexity of the problem, but also provides a more practical solution for these problems in the emerging smart grid environment. This distributed framework is based on iteratively solving in a distributed fashion the first order optimality conditions associated with the optimization formulations. A multi-agent viewpoint of the power system is adopted, in which at each iteration, every network agent updates a few local variables through simple computations, and exchanges information with neighboring agents. Our proposed distributed solution is based on the consensus+innovations framework, in which the consensus term enforces agreement among agents while the innovations updates ensure that local constraints are satisfied.

This thesis provides an implementation of consensus of multi-agent networked systems. Consensus problem is an important issue of distributed computing and has various algorithms and applications in the field of electronical and computer science. The consensus requests all nodes of a network reach an agreement over a certain measurement. An algorithm of convergent consensus problem is implemented through a small network of Bluetooth communication in the thesis. The connections of the Bluetooth devices are wireless, and the device nodes of the network are driven by C++ software and Winsock API. The simulation results show that the implementation completes all the requirements of the distributed consensus algorithm.

University of Macau / Faculty of Science and Technology. / Department of Computer and Information Science

Publish/subscribe is a powerful paradigm for distributed applications based on decoupled clients of information. In pub/sub applications, there exist a large amount of publishers and subscribes ranging from hundreds to millions. Publish/subscribe systems need to disseminate numerous events through a network of brokers. Due to limited resources of brokers, there may be lots of events that cannot be handled in time which in turn causes overload problem. Here arises the need of admission control mechanism to provide guaranteed services in publish/subscribe systems. Our approach gives the solution to this overload problem in the network of brokers by limiting the incoming subscriptions by certain criteria. The criteria are the factors like resources which include bandwidth, CPU, memory (in broker network), resource requirements by the subscription. / by Akshay Kamdar. / Thesis (M.S.C.S.)--Florida Atlantic University, 2009. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2009. Mode of access: World Wide Web.

Cloud Computing is security. In complex systems such as Cloud Computing, parts of a system are secured by using specific products, but there is rarely a global security analysis of the complete system. We have described how to add security to cloud systems and evaluate its security levels using a reference architecture. A reference architecture provides a framework for relating threats to the structure of the system and makes their numeration more systematic and complete. In order to secure a cloud framework, we have enumerated cloud threats by combining several methods because it is not possible to prove that we have covered all the threats. We have done a systematic enumeration of cloud threats by first identifying them in the literature and then by analyzing the activities from each of their use cases in order to find possible threats. These threats are realized in the form of misuse cases in order to understand how an attack happens from the point of view of an attacker. The reference architecture is used as a framework to determine where to add security in order to stop or mitigate these threats. This approach also implies to develop some security patterns which will be added to the reference architecture to design a secure framework for clouds. We finally evaluate its security level by using misuse patterns and considering the threat coverage of the models. / by Keiko Hashizume. / Thesis (Ph.D.)--Florida Atlantic University, 2013. / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.

Esta tese visa demonstrar a aplicação do padrão ODP (Open Distributed System) no desenvolvimento de sistemas distribuídos e abertos aplicados em automação. Para atingir este objetivo define-se uma estratégia cujos elementos básicos são: a metodologia ODP e o experimento ODP. A metodologia suporta o padrão ODP, numa estrutura sistemática e o experimento, aplica-se num projeto, para observar o comportamento do processo de aplicabilidade. A metodologia ODP está composta dos conceitos, procedimentos e modelos, propostos pelo padrão ODP; das técnicas e conceitos da orientação a objetos e da estrutura de um modelo de sistema aberto de automação (SAA), constituindo uma estrutura coerente e gerenciável, de aplicação prática nos projetos de sistemas abertos em automação. No experimento ODP, a metodologia é aplicada no desenvolvimento de um sistema de automoção, cujo escopo são os projetos dos grandes empreendimentos, que utilizam em seu processo de desenvolvimento a engenharia simultânea. O resultado desta automação será caracterizada pela obtenção de um sistema distribuído, aberto e configurado como ambiente cooperativo (Groupware) de projeto. Finalmente, os resultados do experimento serão comparados com outros tipos de metodologias que não utilizam o ODP, para poder concluir sobre a utilização do padrão ODP nos projetos de sistemas de automação. / This thesis purposes to demonstrate the applicability of the open distributed processing standard, in the development of the open distributed system applied in the automation. To achieve this objective a strategy is defined, whose basic elements are the ODP methodology and the ODP experiment. The methodology supports the ODP standard in a systematic structure and the experiment applies it in one project, to observe the behavior of the applicability process. The ODP methodology is composed by concepts, procedures and models, proposed by the ODP standard; by techniques and concepts of the objects oriented, and the structure of an open automation system model (OAS), establishing an manageable and coherent structure. In the ODP experiment, this methodology is applied in the development of an automation system which scope is the large enterprise projects that use in his development process the concurrent engineering. The result of this automation will be characterized by the Open Distributed System and will be configured as a project cooperative environment (Groupware). Finally, the experiment results will be compared with other methodologies that don\'t use ODP, to obtain conclusions about the use of the ODP standard in the automation system projects.

Finally, for improving the security of P2P-based CDNs against peer misbehaviors, we present a stochastic analytical model for understanding the performance of the P2P rating systems, which are widely engaged for safeguarding P2P-based CDNs. We study two representative designs, namely the unstructured self-managing rating (UMR) system and the structured supervising rating (SSR) system with the model under various network environments and adversary attacks. We also propose a configurable loosely supervising rating (LSR) system, and show that the system works inexpensively, and could make tradeoffs between the features of the UMR and the SSR system, thus providing a better overall performance according to the application context. / Peer-to-Peer (P2P) networks, especially P2P-based content distribution networks (CDN), have enabled large-scale content distribution without major infrastructure support in recent years. However, P2P-based CDNs suffer from performance issues such as stability and scalability, as well as security threats due to their decentralized nature. In this thesis, we address the performance and security issues in P2P-based CDNs. / We first consider a BitTorrent-like file swarming system. A simple mathematical model is presented for understanding its performance. With the model we find that under the stable state the peer distribution follows an asymmetric U-shaped curve, which is determined and influenced by various factors. We also analyze the content availability in the system and study its dying process, in which the integrity of the content is endangered. An innovative "tit-for-tat" unchoking strategy enabling more peers to finish their download jobs and prolong the system's lifetime is proposed. We then consider an application-layer tree-like overlay for the synchronous live media multicasting system. In particular we address the instability issue of the multicast overlay caused by nodes' abrupt departures. A set of algorithms are proposed to improve the overlay's stability based on actively estimating the nodes' lifetime model. To support our solution, we have studied the lifetime model via real-world measurements, and have formally proved the effectiveness of the algorithms. The experimental performance evaluation indicates that our algorithms work inexpensively, and could improve the overlay's stability considerably. We also consider the asynchronous on-demand media (MoD) streaming using P2P networks. In particular, we aim to improve the scalability of the system by proposing a novel probabilistic caching mechanism. Theoretical analysis is presented to show that by engaging the proposed mechanism with a flexible system parameter, better scalability could be achieved by a MoD system with less workload imposed on the server. Moreover, we show by simulation that our proposed caching mechanism could improve the streaming service conceived by peers under various conditions of server capacities and network environments. / Tian, Ye. / "July 2007." / Adviser: Kam-Wing Ng. / Source: Dissertation Abstracts International, Volume: 69-02, Section: B, page: 1119. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (p. 180-193). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract in English and Chinese. / School code: 1307.

by Shum Kam Hong. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1992. / Includes bibliographical references (leaves 125-131). / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Background --- p.1 / Chapter 1.2 --- Outline of the thesis --- p.6 / Chapter 1.3 --- Current Art in Packet Switching --- p.9 / Chapter 2 --- Management of Control Information --- p.17 / Chapter 2.1 --- Inter-node Exchange of Link Congestion Status --- p.21 / Chapter 2.2 --- Consistency of Control Information --- p.24 / Chapter 2.3 --- Alternate Format of Control Information --- p.26 / Chapter 3 --- Traffic Flow Control --- p.29 / Chapter 3.1 --- Control of Traffic Influx into the Network --- p.29 / Chapter 3.2 --- Control of Traffic Loading from the Node --- p.30 / Chapter 3.3 --- Flow Control for Connection Oriented Traffic --- p.32 / Chapter 3.4 --- Judgement of Link Status --- p.38 / Chapter 3.5 --- Starvation-free and Deadlock-free --- p.42 / Chapter 4 --- Call Set-up Algorithm Traffic Modelling --- p.47 / Chapter 4.1 --- Basic Algorithm --- p.47 / Chapter 4.2 --- Minimization of Bandwidth Overhead --- p.48 / Chapter 4.3 --- Two-way Transmission --- p.51 / Chapter 4.4 --- Traffic Modelling --- p.52 / Chapter 4.4.1 --- Aggregate Traffic Models --- p.53 / Chapter 4.4.2 --- Traffic Burstiness --- p.57 / Chapter 5 --- Parameters Tuning and Analysis --- p.76 / Chapter 5.1 --- Scheme I : Scout Pumping --- p.76 / Chapter 5.2 --- Scheme II : Speed-up Scout Pumping --- p.85 / Chapter 5.3 --- Blocking Probability --- p.90 / Chapter 5.4 --- Scout Stream Collision --- p.92 / Chapter 6 --- Simulation Modelling & Performance Evaluation --- p.96 / Chapter 6.1 --- The Network Simulator --- p.96 / Chapter 6.1.1 --- Simulation Event Scheduling --- p.97 / Chapter 6.1.2 --- Input Traffic Regulation --- p.100 / Chapter 6.1.3 --- Actual Offered Load --- p.101 / Chapter 6.1.4 --- Static and Dynamic Parameters --- p.103 / Chapter 6.2 --- Simulation Results --- p.107 / Chapter 7 --- Conclusions --- p.123 / Chapter A --- List of Symbols --- p.132

by Lam Hing-Chau, Leon, Yan Yau-Kon, Charles. / Thesis (M.B.A.)--Chinese University of Hong Kong, 1989. / Bibliography: leaves 73-74.