Thesis (Ph. D.)--Computing, Georgia Institute of Technology, 2008. / Committee Chair: Fujimoto, Richard; Committee Member: Ammar, Mostafa; Committee Member: Bader, David; Committee Member: Goldsman, David; Committee Member: Park, Haesun; Committee Member: Riley, George.

ABSTRACT During recent years, the trends in computer resource organization have seen the replacement of the traditional mainframe computers and their timesharing terminals with individual desktop workstations. These workstations can offer more computational power than the mainframes of less than a decade ago. With this distribution of processing from the more traditional mainframe computer comes the need to share peripheral resources among these desktop workstations. These include items such as file systems, tape drives, printers, plotters, and graphics display devices. A common way to share these among the multi-computer environment is to provide a transparent gateway that allows each workstation to function as if it had a dedicated set of peripherals. As educational institutions and industry continue the trend of connecting their computer systems in networks, a serious hole has developed - the ability to estimate the throughput of their network. This paper describes the development, use, and verification of the Local Area Network Simulation Package (LANSIM). LANSIM provides a means to determine the performance characteristics of any network adhering to the ANSI/IEEE Std 802.3-1985 for local area networks. This will allow anyone to simulate a proposed network and gain insight into such crucial topics as percent utilization, aggregate data rates on the network, and response times - all prior to the purchase and installation of the network.

One of the local area network medium access control standards created by the Institute of Electrical and Electronic Engineers in IEEE Project 802 is the carrier sense multiple access with collision detection (CSMA/CD) medium access control. Numerous studies have been reported in the literature on the performance of CSMA/CD. These studies show that CSMA/CD performs well under light network load but not well at heavy load. To improve the performance of CSMA/CD under heavy load, a new concept called network partitioning is presented. Network partitioning allows the network to be partitioned into segments when under heavy load. Partition stations then act as bridges between the segments. The impact of network partitioning on network performance was tested using a simulation model of an Ethernet local area network (an implementation of the CSMA/CD medium access control). The simulation results show that network partitioning can improve the performance of CSMA/CD under heavy load.

Thesis (Ph. D.)--University of California, Riverside, 2009. / Includes abstract. Available via ProQuest Digital Dissertations. Title from first page of PDF file (viewed March 12, 2010). Includes bibliographical references (p. 100-106). Also issued in print.

Literature on the modeling and simulation of complex adaptive systems (cas) has primarily advanced vertically in different scientific domains with scientists developing a variety of domain-specific approaches and applications. However, while cas researchers are inherently interested in an interdisciplinary comparison of models, to the best of our knowledge, there is currently no single unified framework for facilitating the development, comparison, communication and validation of models across different scientific domains. In this thesis, we propose first steps towards such a unified framework using a combination of agent-based and complex network-based modeling approaches and guidelines formulated in the form of a set of four levels of usage, which allow multidisciplinary researchers to adopt a suitable framework level on the basis of available data types, their research study objectives and expected outcomes, thus allowing them to better plan and conduct their respective research case studies. Firstly, the complex network modeling level of the proposed framework entails the development of appropriate complex network models for the case where interaction data of cas components is available, with the aim of detecting emergent patterns in the cas under study. The exploratory agent-based modeling level of the proposed framework allows for the development of proof-of-concept models for the cas system, primarily for purposes of exploring feasibility of further research. Descriptive agent-based modeling level of the proposed framework allows for the use of a formal step-by-step approach for developing agent-based models coupled with a quantitative complex network and pseudocode-based specification of the model, which will, in turn, facilitate interdisciplinary cas model comparison and knowledge transfer. Finally, the validated agent-based modeling level of the proposed framework is concerned with the building of in-simulation verification and validation of agent-based models using a proposed Virtual Overlay Multiagent System approach for use in a systematic team-oriented approach to developing models. The proposed framework is evaluated and validated using seven detailed case study examples selected from various scientific domains including ecology, social sciences and a range of complex adaptive communication networks. The successful case studies demonstrate the potential of the framework in appealing to multidisciplinary researchers as a methodological approach to the modeling and simulation of cas by facilitating effective communication and knowledge transfer across scientific disciplines without the requirement of extensive learning curves.

Orientadores: Paulo Sérgio Martins Pedro, Edson Luiz Ursini / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Tecnologia / Made available in DSpace on 2018-08-23T16:11:28Z (GMT). No. of bitstreams: 1 Nunes_SergioEduardo_M.pdf: 1364072 bytes, checksum: cf8027cf1f7cd7aacf19ed01abd8db41 (MD5) Previous issue date: 2013 / Resumo: Neste trabalho, efetuou-se a avaliação de desempenho em uma rede de pequeno escritório, SOHO (Small Office Home Office), a fim de se conhecer o impacto nas redes de computadores, devido à utilização dos protocolos IPv4, IPv6 ou técnica de transição. As medições realizadas observaram o comportamento da vazão, latência, jitter e perda de pacotes, em três diferentes cenários experimentais: Rede IPv4, Rede IPv6 e Rede Pilha dupla. Os valores numéricos obtidos na análise das redes foram utilizados de forma incremental no programa de simulação ARENA, sendo modelada uma rede multisserviços com condições especiais para teste do impacto. O objetivo desta simulação é conhecer o impacto no comportamento dos serviços stream e elástico devido à variação de desempenho dos protocolos. Tais estudos objetivam ajudar aos administradores de redes no planejamento do período de transição e coexistência, possibilitando com que essa mudança nas redes de computadores possa ocorrer de forma mais suave / Abstract: This work evaluated a SOHO network (Small Office Home Office) in order to assess the impact of the IPv4, IPv6, and their transition protocols, on these networks. The experiments performed measured throughput, latency, jitter and packet loss in three experimental settings: IPv4, IPv6 and Dual Stack. The numeric values obtained in this experimental analysis were further applied, in an incremental fashion, to a multi-services network model built using the ARENA simulation software. The goal of this simulation was to obtain a better understanding of the behavior of both the stream and the elastic services as a function of the variation in protocol performance. This knowledge aims at supporting network managers in their task of planning the transitional period from IPv4 to IPv6, thus allowing for a smoother transition between these protocols / Mestrado / Tecnologia e Inovação / Mestre em Tecnologia

In this thesis, the efficient simulation of large-scale system-level VHDL models is analyzed. The system-level models chosen for the investigation are multicomputer networks, which are scalable up to thousands of processing nodes. Initially, a classification of parallel processing architectures is presented along with performance criteria and design issues related to the various interconnection network topologies. Communication and synchronization issues of MIMD systems are explored. A major limitation of planar tree structures is discussed along with a solution to help alleviate the problem, which is to make use of the binary fat-tree. Practical aspects of efficiently simulating large behavioral and structural models (using the fat-tree model as a case study), on a uniprocessor system are analyzed. The system resources of the workstation used to perform the simulations are carefully monitored to see where resource utilization problems usually occur. The size of the model is increased and the run time of the simulation compared with that of smaller sized models. A memory threshold level is detected after which memory resource contention problems occur and the simulation efficiency declines. One of the problems observed in simulating complex models is the fact that simulation runs take a very long time to execute. A multicomputer using the fat-tree interconnection network is proposed as a suitable architecture for the distributed simulation of VHDL models. Various algorithms used for the parallel discrete event simulation (PDES) of VHDL models are evaluated. The feasibility of this approach is evaluated by analyzing the factors affecting the performance of the proposed architecture. The number of hops a message takes to travel from one processor to another in the fat-tree is used to estimate the time of an event message between two processors. The roll-back and communication costs amongst the processing nodes are taken into consideration when evaluating the speedup of the simulation time of a VHDL model, simulated over multiple processors. The speedup of the simulation obtained by using the fat-tree topology is compared with the results obtained with a linear array of processors. The future inclusion of the "shared variable" into the language and its impact on the implementation of parallel simulators on multicomputer networks is analyzed. / Master of Science

Thesis (M. App. Sc.)--Carleton University, 2005. / Includes bibliographical references (p. 71-76). Also available in electronic format on the Internet.

Simulation has become an important way to observe and understand various networking phenomena under various conditions. As the demand to simulate larger and more complex networks increases, the limited computing capacity of a single workstation and the limited simulation capability of a single network simulator have become apparent obstacles to the simulationists. In this research we develop techniques that can scale a simulation to address the limited capacity of a single workstation, as well as techniques that can compose a simulation from different simulator components to address the limited capability of a single network simulator. We scale a simulation with two different approaches: 1) We reduce the resource requirement of a simulation substantially, so that larger simulations can fit into one single workstation. In this thesis, we develop three technqiues (Negative Forwarding Table, Multicast Routing Object Aggregation and NIx-Vector Unicast Routing) to aggregate and compress the large amount of superfluous or redundant routing state in large multicast simulations. 2) The other approach to scale network simulations is to partition a simulation model in a way that makes the best use of the resources of the available computer cluster, and distribute the simulation onto the different processors of the computer cluster to obtain the best parallel simulation performance. We develop a novel empirical methodology called BencHMAP (Benchmark-Based Hardware and Model Aware Partitioning) that runs small sets of benchmark simulations to derive the right formulas of calculating the weights that are used to partition the simulation on a given computer cluster. On the other hand, to address the problem of the limited capability of a network simulator, we develop techniques for building complex network simulations by composing from independent components. With different existing simulators good at different protocol layers/scenarios, we can make each simulator execute the layers where it excels, using a simulation backplane to be the interface between different simulators. In this thesis we demonstrate that these techniques enable us to not only scale up simulations by orders of magnitude with a good performance, but also compose complex simulations with high fidelity.

Network emulation has been widely used to aid in the development and evaluation of real-time applications. Many of today s applications and protocols need to be tested and evaluated in large scale network environments such as the Internet, which requires emulation tools that meet the requirements of scale, accuracy, timeliness. Due to physical resource constraints in network emulators, existing emulation tools fail to meet these requirements as they are either limited to small and static networks, use simplified network models, or fail to deliver timely emulation results. If more physical resources are devoted to network emulation by utilizing high performance computing facilities, the accuracy and scalability of network emulation can be greatly improved. However, for many users, high performance computing facilities may not be readily available in a local laboratory environment, and co-locating application code with a remote high performance computing facility may be cumbersome and inconvenient. This thesis proposes a network emulation approach called ROSENET (RemOte SErver-based Network EmulaTion) that utilizes a distributed server-based architecture in which local low-fidelity emulators provide real-time QoS predictions to distributed applications, coupled with a remote large scale high-fidelity simulator that continuously updates and calibrates the local low-fidelity emulators. A library-based modeling approach based on online simulation data collection is proposed and a system identification modeling technique is presented. Experimental results examining emulation end-to-end delay and loss show that ROSENET provides a promising approach to network emulation supporting accuracy and scale while meeting real-time constraints. Challenges faced in applying ROSENET to real world applications are addressed through two case studies including applying synthetic workload on DARPA s NMS network topology for large scale network simulation and a contemporary real-time distributed VoIP application Skype.