Bibliography: leaves 128-135. Investigates the behaviour of TCP bulk file transfer application sessions in a broadband access environment. Introduces some concepts for evaluating network behaviour: a path instability parameter for analyzing different TCP connections; a minimum RTT delay and a minimum typical path for estimating path characteristics between a client and application servers.

Orientadores: Edson Moschim, Felipe Rudge Barbosa / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-09T16:46:35Z (GMT). No. of bitstreams: 1 Martins_IndayaraBertoldi_M.pdf: 1239150 bytes, checksum: 785fa753532d04d698ee47a542591430 (MD5) Previous issue date: 2007 / Resumo: Neste trabalho investigamos o desempenho de redes ópticas avançadas, em particular redes de chaveamento de pacotes ópticos (Optical Packet Switching Network-OPSN), constituídos por arquiteturas com topologias em malha e nós ópticos sem armazenador. Utilizou-se distribuição de tráfego uniforme, na qual todos os nós geram a mesma quantidade de tráfego para todos os outros nós. Foram avaliados vários parâmetros de redes OPSN, principalmente número médio de saltos e capacidade efetiva da rede, bem como comparações entre topologias anel e malha, considerando como parâmetros principais vazão e desempenho, e os impactos causados por falhas de enlaces. Demonstrouse também que o aumento do número de nós em OPSNs, não necessariamente aumenta o desempenho ou capacidade / Abstract: In this work we have investigated the performance of advanced optical networks, more specifically optical packet switched networks (OPSN), with architectures comprising fully connected mesh topologies and optical bufferless nodes. We have adopted uniform traffic distribution, in which all nodes generate the same traffic to every other node. Several parameters of the OPSNs have been evaluated, mainly average number of hops and effective network capacity, as well as comparisons between the ring and mesh network topologies, considering as main parameters the network throughput and performance, and the impacts caused by failures of links. We demonstrate that increasing the number of nodes in OSPNs does not necessarily increase performance or capacity / Mestrado / Telecomunicações e Telemática / Mestre em Engenharia Elétrica

Orientadores: Edson Moschim, Felipe Rudge Barbosa / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-19T06:49:01Z (GMT). No. of bitstreams: 1 Martins_IndayaraBertoldi_D.pdf: 4857444 bytes, checksum: dd92f8f5d511ebe8130c0e4a7ee7e722 (MD5) Previous issue date: 2011 / Resumo: Neste trabalho investiga-se através de simulação computacional, o desempenho de Redes Ópticas Avançadas, usando tecnologia de Chaveamento de Pacotes Ópticos (Optical Packet Switching - OPS), com topologias em anel e malha, e nós ópticos com roteamento sem conversão eletro-óptica dos pacotes, e sem armazenadores na camada óptica de transporte. São analisados parâmetros como capacidade da rede, vazão efetiva, número médio de saltos, e fração de perda de pacotes; introduz-se também um novo fator de desempenho da rede. São propostas novas configurações para as topologias analisadas, as quais se revelaram com melhor desempenho que as tradicionais. Constatou-se que a aplicação de armazenadores eletrônicos (buffers) na interface de entrada/saída do cliente (ingresso/egresso à rede) praticamente eliminou a perda de pacotes ópticos. A fim de subsidiar planejamento para proteção da rede, analisa-se o impacto de falha de enlaces e de nós no desempenho das varias arquiteturas analisadas. A rede em malha é a que sempre apresenta os melhores resultados. Foi também feita uma avaliação dos modelos de redes adotados para tráfego IP, visando aplicação na convergência de redes de fibras e redes sem-fio (wireless-fiber). Uma conclusão importante deste trabalho é que o grau de conexões dos nós das redes é mais relevante para capacidade e desempenho do que apenas o número de nós da rede. Este trabalho não analisa limitações físicas de transmissão porque focaliza redes metropolitanas de acesso, com os pacotes ópticos nunca percorrendo distâncias superiores a 60 ou 70 km / Abstract: In this work the performance of advanced optical networks was investigated through computational simulations using optical packet switching (OPS) technology, with mesh and ring topologies. Routing in the optical nodes is carried out without electro-optical conversion of the optical packets and buffering is not used on the optical layer. The analyses are based on the network parameters capacity, throughput, average number of hops, packet loss fraction; an additional performance factor is introduced in this work. New network and node configurations are proposed and analyzed, and it was verified that they perform better than traditional topologies. It was verified that the application of electronic buffer on end-client input and output interfaces (ingress/egress of the optical network) practically eliminate optical packet loss, which mostly occur at input to the optical layer. In order to subsidize the network protection planning, analyses of the impact of link and node failure in the various architectures was studied. The mesh network obtained the best results in all situations. A network model adopted for IP traffic was also evaluated in order to consider the adequacy of our models to this traffic and the convergence of fiber networks and wireless networks (wireless-fiber). Important conclusions are that the models are simple and perform very well under various conditions, and that the degree of interconnection of the nodes is more relevant for capacity and performance than just the number of network nodes. Actually in some cases it is better to increase connectivity than number of nodes. Finally, this work does not analyze the physical limitations of transmission because it focuses on metropolitan access networks, with optical packets having a limited number of hops and never exceeding distances greater than 60 or 70 km / Doutorado / Telecomunicações e Telemática / Doutor em Engenharia Elétrica

Information Technology (IT) Project Management methodologies are numerous, often varying from organization to organization, and sometimes from project to project within the same organization. Although project type and scope can be a powerful indicator of what methodologies may work best for a given project, choosing which methodology to use can be daunting for project teams. At times, even after due diligence has been practiced to identify the management options available for a given project, there may not be a perfect fit. At such times, or when a formal methodology does not exist in an organization or project management office, the best approach for a project may be to utilize a collective of “best practices,” instead of a concrete methodology. When tasked with the IT Project Management of the new Gary Ransdell Hall on WKU’s main campus, the IT Project Manager (PM) did not have a tried-and-true methodology to use for managing the project. As a result, the IT PM and project team chose to research best practices, as reflected in the Project Management Body of Knowledge (PMBOK), to formulate a project plan that would maximize efficiency while protecting the triple constraints. Early in this paper, the author outlines assumptions, constraints, and risks that faced the IT team throughout the project cycle. Afterwards, the resulting methods and procedures used to manage the IT scope for the project are discussed, with figures included for reference. Next, a brief project summary is included to summarize the results of the project, with performance and scope metrics and limited end-user feedback. Finally, the lessons learned section outlines changes that have been implemented since project completion, as part of a continuous improvement effort by the WKU IT Division.

This work presents the development of the Context-Aware Hybrid Data Dissemination protocol for vehicular networks. The importance of developing vehicular networking data dissemination protocols is exemplified by the recent announcement by the U.S. Department of Transportation (DOT) National Highway Traffic Safety Administration (NHTSA) to enable vehicle-to-vehicle (V2V) communication technology. With emphasis on safety, other useful applications of V2V communication include but are not limited to traffic and routing, weather, construction and road hazard alerts, as well as advertisement and entertainment. The core of V2V communication relies on the efficient dispersion of relevant data through wireless broadcast protocols for these varied applications. The challenges of vehicular networks demand an adaptive broadcast protocol capable of handling diverse applications. This research work illustrates the design of a wireless broadcast protocol that is context-aware and adaptive to vehicular environments taking into consideration vehicle density, road topology, and type of data to be disseminated. The context-aware hybrid data dissemination scheme combines store-and-forward and multi-hop broadcasts, capitalizing on the strengths of both these categories and mitigates the weaknesses to deliver data with maximum efficiency to a widest possible reach. This protocol is designed to work in both urban and highway mobility models. The behavior and performance of the hybrid data dissemination scheme is studied by varying the broadcast zone radius, aggregation ratio, data message size and frequency of the broadcast messages. Optimal parameters are determined and the protocol is then formulated to become adaptive to node density by keeping the field size constant and increasing the number of nodes. Adding message priority levels to propagate safety messages faster and farther than non-safety related messages is the next context we add to our adaptive protocol. We dynamically set the broadcast region to use multi-hop which has lower latency to propagate safety-related messages. Extensive simulation results have been obtained using realistic vehicular network scenarios. Results show that Context-Aware Hybrid Data Dissemination Protocol benefits from the low latency characteristics of multi-hop broadcast and low bandwidth consumption of store-and-forward. The protocol is adaptive to both urban and highway mobility models. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2014. / FAU Electronic Theses and Dissertations Collection

This research is motivated by the recent developments in the Internet Engineering Task Force (IETF) to support seamless integration of moving networks deployed in vehicles to the global Internet. The effort, known as Network Mobility (NEMO), paves the way to support high-speed Internet access in mass transit systems, e.g. trains; buses; ferries; and planes; through the use of on-board mobile routers embedded in the vehicle. One of the critical research challenges of this vision is to achieve high-speed and reliable back-haul connectivity between the mobile router and the rest of the Internet. The problem is particularly challenging due to the fact that a mobile router must rely on wireless links with limited bandwidth and unpredictable quality variations as the vehicle moves around. In this thesis, the multi-homing concept is applied to approach the problem. With multi-homing, mobile router has more than one connection to the Internet. This is achieved by connecting the mobile router to a diverse array of wireless access technologies (e.g., GPRS, CDMA, 802.11, and 802.16) and/or a multiplicity of wireless service providers. While the aggregation helps addressing the bandwidth problem, quality variation problem can be mitigated by employing advanced traffic engineering techniques that dynamically control inbound and outbound traffic over multiple connections. More specifically, the thesis investigates traffic engineering solutions for mobile networks that can effectively address the performance objectives, e.g. maximizing profit for mobile network operator; guaranteeing quality of service for the users; and maintaining fair access to the back-haul bandwidth. Traffic engineering solutions with three different levels of control have been investigated. First, it is shown, using detailed computer simulation of popular applications and networking protocols(e.g., File Transfer Protocol and Transmission Control Protocol), that packet-level traffic engineering which makes decisions of which Internet connection to use for each and every packet, leads to poor system throughput. The main problem with packet-based traffic engineering stems from the fact that in mobile environment where link bandwidths and delay can vary significantly, packets using different connections may experience different delays causing unexpected arrivals at destinations. Second, a maximum utility flow-level traffic engineering has been proposed that aims to maximize a utility function that accounts for bandwidth utilization on the one hand, and fairness on the other. The proposed solution is compared against previously proposed flow-level traffic engineering schemes and shown to have better performance in terms of throughput and fairness. The third traffic engineering proposal addresses the issue of maximizing operator?s profit when different Internet connections have different charging rates, and guaranteeing per user bandwidth through admission control. Finally, a new signaling protocol is designed to allow the mobile router to control its inbound traffic.

The future Internet will need to cater for an increasing number of powerful devices and entire groups of networks to roam in heterogeneous access networks. The current approach towards meeting such requirements, which is to retrofit mobility solutions to different layers of the protocol stack, has given rise to an increasingly fragmented network control layer. Furthermore, retrofitting solutions in an ad-hoc manner to the protocol stack does not provide consistent support from the network to different applications. This lack of a common control layer for facilitating roaming in heterogeneous networking environments represents a crucial challenge both technically and from a user perspective. To this end, a novel mobility architecture forms the basis and the first part of this dissertation. The work on investigating current network mobility solutions and improving these solutions if deemed necessary, in order to reuse within the novel mobility architecture constitutes the second part of this dissertation. The IETF standard protocol for network mobility was implemented and its performance was analysed on a real networking environment. This enabled to identify problems in the standard which affect the handover and routing performance. To address the identified routing and protocol header overheads of the standard network mobility protocol a novel optimal routing framework, OptiNets was proposed. To address the handover latency issues, optimizations to IPv6 network attachment were incorporated and also an access technology independent multiple interface Make-Before-Break handover mechanism was proposed. The viability of the OptiNets framework and the handover optimizations were demonstrated by analysis and by implementation. A more general external factor that affects the performance of mobile networks which is bandwidth scarcity of Wireless Wide Area Networks was addressed, by proposing a bandwidth fuelling architecture for on-board mobile networks. The feasibility of the bandwidth fuelling architecture was analysed by implementing a prototype and evaluating its performance.

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

Data interoperability between computer-aided design (CAD) systems remains a major obstacle in the information integration and exchange in a collaborative engineering environment. The standards for CAD data exchange have remained largely restricted to geometric representations, causing the design intent portrayed through construction history, features, parameters, and constraints to be discarded in the exchange process. In this thesis, an ontology-based framework is proposed to allow for the full exchange of semantic feature data. A hybrid ontology approach is proposed, where a shared base ontology is used to convey the concepts that are common amongst different CAD systems, while local ontologies are used to represent the feature libraries of individual CAD systems as combinations of these shared concepts. A three-branch CAD feature model is constructed to reduce ambiguity in the construction of local ontology feature data. Boundary representation (B-Rep) data corresponding to the output of the feature operation is incorporated into the feature data to enhance data exchange. The Ontology Web Language (OWL) is used to construct a shared base ontology and a small feature library, which allows the use of existing ontology reasoning tools to infer new relationships and information between heterogeneous data. A combination of OWL and SWRL (Semantic Web Rule Language) rules are developed to allow a feature from an arbitrary source system expressed via the shared base ontology to be automatically classified and translated into the target system. These rules relate input parameters and reference types to expected B-Rep objects, allowing classification even when feature definitions vary or when little is known about the source system. In cases when the source system is well known, this approach also permits direct translation rules to be implemented. With such a flexible framework, a neutral feature exchange format could be developed.

This research is motivated by the recent developments in the Internet Engineering Task Force (IETF) to support seamless integration of moving networks deployed in vehicles to the global Internet. The effort, known as Network Mobility (NEMO), paves the way to support high-speed Internet access in mass transit systems, e.g. trains; buses; ferries; and planes; through the use of on-board mobile routers embedded in the vehicle. One of the critical research challenges of this vision is to achieve high-speed and reliable back-haul connectivity between the mobile router and the rest of the Internet. The problem is particularly challenging due to the fact that a mobile router must rely on wireless links with limited bandwidth and unpredictable quality variations as the vehicle moves around. In this thesis, the multi-homing concept is applied to approach the problem. With multi-homing, mobile router has more than one connection to the Internet. This is achieved by connecting the mobile router to a diverse array of wireless access technologies (e.g., GPRS, CDMA, 802.11, and 802.16) and/or a multiplicity of wireless service providers. While the aggregation helps addressing the bandwidth problem, quality variation problem can be mitigated by employing advanced traffic engineering techniques that dynamically control inbound and outbound traffic over multiple connections. More specifically, the thesis investigates traffic engineering solutions for mobile networks that can effectively address the performance objectives, e.g. maximizing profit for mobile network operator; guaranteeing quality of service for the users; and maintaining fair access to the back-haul bandwidth. Traffic engineering solutions with three different levels of control have been investigated. First, it is shown, using detailed computer simulation of popular applications and networking protocols(e.g., File Transfer Protocol and Transmission Control Protocol), that packet-level traffic engineering which makes decisions of which Internet connection to use for each and every packet, leads to poor system throughput. The main problem with packet-based traffic engineering stems from the fact that in mobile environment where link bandwidths and delay can vary significantly, packets using different connections may experience different delays causing unexpected arrivals at destinations. Second, a maximum utility flow-level traffic engineering has been proposed that aims to maximize a utility function that accounts for bandwidth utilization on the one hand, and fairness on the other. The proposed solution is compared against previously proposed flow-level traffic engineering schemes and shown to have better performance in terms of throughput and fairness. The third traffic engineering proposal addresses the issue of maximizing operator?s profit when different Internet connections have different charging rates, and guaranteeing per user bandwidth through admission control. Finally, a new signaling protocol is designed to allow the mobile router to control its inbound traffic.