Digital audio networks are becoming the preferred solution for the interconnection of professional audio devices. Prominent amongst their advantages are: reduced noise interference, signal multiplexing, and a reduction in the number of cables connecting networked devices. In the context of professional audio, digital networks have been used to connect devices including: mixers, effects units, preamplifiers, breakout boxes, computers, monitoring controllers, and synthesizers. Such networks are governed by protocols that define the connection management rocedures, and device synchronization processes of devices that conform to the protocols. A wide range of digital audio network control protocols exist, each defining specific hardware requirements of devices that conform to them. Device parameter control is achieved by sending a protocol message that indicates the target parameter, and the action that should be performed on the parameter. Typically, a device will conform to only one protocol. By implication, only devices that conform to a specific protocol can communicate with each other, and only a controller that conforms to the protocol can control such devices. This results in the isolation of devices that conform to disparate protocols, since devices of different protocols cannot communicate with each other. This is currently a challenge in the professional music industry, particularly where digital networks are used for audio device control. This investigation seeks to resolve the issue of interoperability between professional audio devices that conform to different digital audio network protocols. This thesis proposes the use of a proxy that allows for the translation of protocol messages, as a solution to the interoperability problem. The proxy abstracts devices of one protocol in terms of another, hence allowing all the networked devices to appear as conforming to the same protocol. The proxy receives messages on behalf of the abstracted device, and then fulfills them in accordance with the protocol that the abstracted device conforms to. Any number of protocol devices can be abstracted within such a proxy. This has the added advantage of allowing a common controller to control devices that conform to the different protocols.

Com o intuito de utilizar uma rede com protocolo IP para a implementação de malhas fechadas de controle, este trabalho propõe-se a realizar um estudo da operação de um sistema de controle dinâmico distribuído, comparando-o com a operação de um sistema de controle local convencional. Em geral, a decisão de projetar uma arquitetura de controle distribuído é feita baseada na simplicidade, na redução dos custos e confiabilidade; portanto, um diferencial bastante importante é a utilização da rede IP. O objetivo de uma rede de controle não é transmitir dados digitais, mas dados analógicos amostrados. Assim, métricas usuais em redes de computadores, como quantidade de dados e taxa de transferências, tornam-se secundárias em uma rede de controle. São propostas técnicas para tratar os pacotes que sofrem atrasos e recuperar o desempenho do sistema de controle através da rede IP. A chave para este método é realizar a estimação do conteúdo dos pacotes que sofrem atrasos com base no modelo dinâmico do sistema, mantendo o sistema com um nível adequado de desempenho. O sistema considerado é o controle de um manipulador antropomórfico com dois braços e uma cabeça de visão estéreo totalizando 18 juntas. Os resultados obtidos mostram que se pode recuperar boa parte do desempenho do sistema. / ln order to enable the use of IP networks to implement closed-Ioop control systems, this work compares a distributed control system to its conventional counterpart, which is based on local controI. Usually the option for a distributed control architecture is motivated by simplicity, cost reduction and reliability, hence the use of an IP network. The goal of a control network is not to transmit pure digital data, but to transmit digitized control and sensor signals. Therefore, metrics common in computer networks, such as amount of transfered data and transfer rates, become of little importance. This work proposes a method to compensate for the delays imposed to network packets and to recover the control system performance. The key for this method is to estimate the contents of delayed network packets based on the system dymanic modeI. The example system is an antropormorphic robot with two arms and a stereo vision head. Results show that the system performance can be recovered.

Devido à evolução e à crescente complexidade dos sistemas computacionais, grandes mudanças ocorreram na área de gerenciamento de redes. Os modelos tradicionais centralizados se mostraram limitados, e novos modelos de gerenciamento de redes estão sendo propostos e investigados. Neste cenário, modelos de comunicação P2P permitem a construção de ambientes dinâmicos e versáteis capazes de resolver problemas de diferentes áreas da computação, entre elas o gerenciamento de redes. O modelo P2P torna-se atrativo porque se encaixa perfeitamente no gerenciamento de redes distribuído atualmente solicitado. A partir da proposta de gerenciamento de redes usando P2P e da apresentação de um novo modelo conceitual usando essa nova perspectiva, foi desenvolvido um projeto de arquiteturas para gerenciamento baseadas em P2P, focando-se em entidades tais como peers de gerenciamento Top-Level (TLM) e Mid-Level (MLM). A fim de efetivamente concretizar o gerenciamento baseado em P2P, foram introduzidas definições de blocos básicos para sistemas de gerenciamento baseados em P2P. A integração desses blocos básicos com soluções tradicionais de gerenciamento, tal como a estrutura SNMP, também foi apresentada. Um dos conceitos centrais da arquitetura apresentada são os Serviços de Gerenciamento, que definem as tarefas básicas de gerenciamento do sistema, e foram inspirados nos conceitos de Web Services e na concepção de serviços das Arquiteturas Orientadas a Serviço (SOA). Para a avaliação desse novo modelo de gerenciamento de redes e da arquitetura associada, surgiu a necessidade do desenvolvimento de um protótipo do sistema, com o intuito de servir como uma plataforma para desenvolvimento e implantação de Serviços de Gerenciamento. Esse protótipo é usado para avaliação e análise de testes e resultados associados. Para preservar as características de disponibilidade e escalabilidade que são inerentes dos sistemas P2P, definiu-se que os Serviços de Gerenciamento devem ser disponibilizados por Grupos de MLMs, organizados de forma a fazer a distribuição de tarefas de gerenciamento entre si. Diversos modelos de distribuição de carga foram investigados, foram realizadas avaliações e gráficos comparativos, e foram estabelecidas diretrizes sobre quando e como deve ser aplicado cada modelo, de modo a alcançar sempre o melhor rendimento e a maximização do aproveitamento dos recursos disponíveis ao sistema. A avaliação realizada consistiu na execução de diversas requisições com diferentes números de MLMs usando diferentes algoritmos de distribuição de carga, e na comparação entre a vazão, os tempos de resposta e o tráfego de rede gerados pelos diferentes casos de uso. A implementação desenvolvida neste trabalho demonstrou ser promissora, apresentando resultados bastante satisfatórios com relação aos parâmetros avaliados. / Due to the increasing complexity of computer systems, deep changes have occurred in network management in the past few years. Traditional centralized models have been proved limited, and new network management models are being proposed and investigated. In this scenery, P2P communication models allow for the creation of dynamic and versatile environments, able to solve problems in various computational areas, one of them being network management. The P2P model fits perfectly in the current demands of distributed network management. Starting from the proposed P2P-based network management model, a new P2P-based network management architecture has been developed, focusing on entities like Top-Level (TLM) and Mid-Level (MLM) management peers. With the purpose of making the P2P-based network management real, new building blocks for P2P-based network management systems have been defined. In the present work, an integration of these new building blocks with traditional network management solutions - like SNMP - is presented. One of the main concepts of the proposed architecture is on Management Services, inspired by Web Services and in the service definition of Service Oriented Architectures (SOA). To evaluate this new network management model and its associated architecture, it was necessary to develop a prototype system to be used as platform for development and deployment of Management Services. This prototype was used for evaluation, testing and result analysis. To hold the characteristics of availability and scalability that are inherent to the P2P systems, the Management Services had to be served by MLM groups, organized in a way to distribute the management tasks between them. Several load distribution models were investigated, with evaluation and comparative graphics fulfilled, and some guidelines were established as to when and how each model should be applied to reach the best performance and the maximization of the computational resources available to the system. The evaluation consisted in the execution of several requests in groups with distinct MLM numbers and using distinct load distribution algorithms. Then, the response time and network traffic generated by use cases were compared. We then showed that the developed implementation of our proposal is promising, and presents good results in relation with the evaluated parameters.

There are a number of known architectural patterns for TCP/IP server design. I present a survey of design choices based on some of the most common of these patterns. I have demonstrated, with working code samples, that most of these architectural patterns are readily portable between UNIX and Windows NT platforms without necessarily incurring significant performance penalties. / Computing / M. Sc. (Computer Science)

Bandwidth management is a topic which is often discussed, but on which relatively little work has been done with regard to compiling a comprehensive set of techniques and methods for managing traffic on a network. What work has been done has concentrated on higher end networks, rather than the low bandwidth links which are commonly available in South Africa and other areas outside the United States. With more organisations increasingly making use of the Internet on a daily basis, the demand for bandwidth is outstripping the ability of providers to upgrade their infrastructure. This resource is therefore in need of management. In addition, for Internet access to become economically viable for widespread use by schools, NGOs and other academic institutions, the associated costs need to be controlled. Bandwidth management not only impacts on direct cost control, but encompasses the process of engineering a network and network resources in order to ensure the provision of as optimal a service as possible. Included in this is the provision of user education. Software has been developed for the implementation of traffic quotas, dynamic firewalling and visualisation. The research investigates various methods for monitoring and management of IP traffic with particular applicability to low bandwidth links. Several forms of visualisation for the analysis of historical and near-realtime traffic data are also discussed, including the use of three-dimensional landscapes. A number of bandwidth management practices are proposed, and the advantages of their combination, and complementary use are highlighted. By implementing these suggested policies, a holistic approach can be taken to the issue of bandwidth management on Internet links.

This study examined how online social networking (OSN) leads to increased communication and collaboration across inter-firm boundaries. This online social networking behaviour represents significant opportunities to firms in the form of improved problem-solving, increased collaborative innovation and enhanced engagement with stakeholders. There are also risks inherent in the widespread use of OSNs, such as the loss of control over information flows to individuals outside the organization, potential damage to the reputation of brands and organizations, and loss of productivity due to excessive usage of OSNs during work hours. In particular, this study sought to test four research propositions, specifically, that usage of one particular OSN, LinkedIn (LI), results in: 1) an increased number of inter-firm connections; 2) an improved ability to communicate across inter-firm boundaries; 3) greater access to problem solving or innovation collaborators; 4) increased organizational problem solving or innovation ability. The study methodology involved both quantitative and qualitative research. The quantitative portion of the study involved survey research among over 500 LinkedIn (LI) users to determine changes they reported in various dimensions related to inter-firm relationship-forming, information-sharing and collaborative problem solving since using LI. The sampling approach was purposive and the sample frame consisted of the researcher’s own extended LI network, and an effort was also made to make the survey link available to all LI members through public posting in the site’s Q&A section. Though no individual or group was systematically excluded from the opportunity to take the survey, some limitations are inherent in the approach taken. The survey respondents were self-selecting, which makes it difficult to confirm that the sample is reflective of all LI users. Also, the use of the researcher’s own LI network as a key source of survey respondents may have biased the study toward more open networkers, since the researcher’s network was built up over time by practicing open networking behaviours. As a result, the sample may tend to under-represent more closed or restrictive networkers. Notwithstanding these limitations, no one particular group of respondents was excluded from the opportunity to take the survey, and the resulting data suggests that there were significant numbers of respondents who considered themselves closed networkers. Also, the spread of respondents by geographic area, occupation and age was found to resemble published statistics from LI on its user base, so it appears that the data is reasonably reflective of the LI user base, though this would be difficult to verify or measure. Qualitative research was also undertaken among senior managers at companies that have embraced the use of OSNs by staff to determine their experiences along similar dimensions. The findings from the quantitative survey showed that users of LI have experienced an increased number of social connections with individuals as a result of using LI, and that these connections are often with people in other organizations, including competitors and customers. Survey respondents also reported that they have been able to draw upon their LI networks in order to solve problems and be more innovative in their work. Analysis of the qualitative research yielded a list of suggested best practices that could be adopted by firms wishing to harness the collaborative power of OSNs. These suggested best practices have been grouped under the areas of strategy, listening, communication, guidelines, training, diffusion and measurement. Some suggested areas for future research included: the role of performance measurement and reward systems in managing OSN usage behaviour; the organizational risks of centralized versus decentralized control of messaging via OSNs; the role of training in the effective deployment of OSNs in an organizational context; and the organizational risk of increased connectedness with competitors resulting from OSN relationships. / Business Management / D.B.L.

Submitted by Maria Medeiros (maria.dilva1@ufcg.edu.br) on 2018-11-09T12:48:37Z No. of bitstreams: 1 FLÁVIO GONÇALVES DA ROCHA - DISSERTAÇÃO (PPGCC) 2002.doc: 1342464 bytes, checksum: ad7017974895aef1540dd8f4ad2b142c (MD5) / Made available in DSpace on 2018-11-09T12:48:37Z (GMT). No. of bitstreams: 1 FLÁVIO GONÇALVES DA ROCHA - DISSERTAÇÃO (PPGCC) 2002.doc: 1342464 bytes, checksum: ad7017974895aef1540dd8f4ad2b142c (MD5) Previous issue date: 2002-08-28 / Estudos e análises de sistemas de computação e de comunicação de dados podem ser complexos devidos, em geral, a grande quantidade de recursos a serem considerados e ao relacionamento dinâmico que esses recursos apresentam. Adicionalmente, novas tecnologias se apresentam exigindo estudos e análises mais detalhados quanto as suas utilizações e desempenhos. A dinâmica desses sistemas depende da ocorrência de eventos, que representam, por exemplo, em um sistema de comunicação de dados, o término de transmissão de uma mensagem em um canal de comunicação. Como conseqüência, ambientes de simulação orientados a eventos muitas vezes se apresentam como a melhor alternativa para estudos e análises desses sistemas. O processo de construção de tais ambientes pode ser feito com o uso de componentes de software que possibilitam uma maior reutilização de código aumentando a eficácia desse processo. Nessa Dissertação, dois tipos de componentes são especificados e implementados: os que permitem a construção facilitada de ambientes de simulação orientados a eventos (relógio simulado, lista de eventos, geradores de valores aleatórios e controle da simulação, entre outros), e os que representam elementos essenciais de uma rede de computadores TCP/IP (fontes de pacotes, hosts, enlaces e roteadores). Como estudo de caso, um ambiente de simulação de redes TCP/IP foi construído e validado. Na especificação dos componentes foi utilizada a Linguagem de Modelagem Unificada (UML). A tecnologia para a implementação escolhida foi Java (JavaBeans) e o Ambiente de Desenvolvimento utilizado Jbuilder. Finalmente, os componentes podem ser reutilizados na construção de qualquer ambiente de simulação orientado a eventos que se aplique a modelos que apresentam contenção de recursos. / Studies and analysis of computation and data communication systems could be complex due to the great amount of resources to be considered and their relationship. As new technologies appear more detailed studies and analysis are required. The dynamic of these systems depends on event occurrence. Simulation event-driven tools are frequently chosen for aiding studies and analysis of those systems. In the software development process of those tools software components can facilitate the software reuse increasing the efficiency of this process. This work, specifies and implements two types of components for building simulation tools: components for constructing event-driven simulation tools (such as simulated clock, randon value generators, event list, simulation flow control) and another components for simulating TCP/IP computer networks basic elements (such as packet sources, hosts, routers and links). As a case of study, a simulation tool was constructed. The work adopts JavaBeans technology, Unified Modeling Language (UML) for specification the components and Jbuilder as development tool. Finally, the components construted in this work can be reused to build any event-driven simulation tool.

Made available in DSpace on 2016-02-05T18:29:44Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-09-29. Added 1 bitstream(s) on 2016-02-05T18:33:45Z : No. of bitstreams: 1 000857576.pdf: 7557798 bytes, checksum: 6e8a765ad9093e0c9fec6caab04c39b3 (MD5) / Nos últimos anos têm-se percebido que o atual sistema de geração, transmissão e distribuição de energia elétrica tradicional tornou-se insuficiente e ultrapassado para suprir toda a demanda. Com isso houve um forte crescimento nas pesquisas sobre um conceito com novas tecnologias para modernizar ou construir a rede de energia elétrica em seus aspectos de infraestrutura, disponibilidade, sustentabilidade e confiabilidade. Este novo conceito trata-se do smart grid que propõe uma tecnologia baseada na automação, comunicação, monitoração e controle da rede elétrica, a qual permite implantação de estratégias de controle e otimização da rede de forma eficiente perante as atualmente utilizadas. As tecnologias aplicadas no smart grid englobam muitos sistemas. Entre esses sistemas estão topologia de comunicação, circuitos e interfaces eletrônicas, na qual dificulta a construção de um cenário real para realizar estudos e pesquisas de qual sistema de comunicação é o mais adequado para as aplicações no smart grid. Os equipamentos são muito onerosos e dependendo da extensão e quantidade de dispositivos que serão implantados, tornam impossíveis as realizações em cenário de campo. Para sanar esses problemas são utilizados os softwares de simulação que são ferramentas convenientes nesses casos e comumente empregadas na área de pesquisa, para realizar a análise e o desempenho de um sistema. Uma rede de comunicação envolvendo aplicações críticas, como é o caso da transmissão e distribuição de energia elétrica, deve ser altamente confiável, extremamente segura e resiliente a falhas. Para realizar análises de desempenho de uma rede de comunicação wireless a ser utilizado em aplicações smart grid com resultados desejáveis, é preciso realizar simulações para poder prever qualquer eventualidade de possíveis falhas. De todos os simuladores existentes o mais indicado foi o NS-2, um simulador à evento... / In recent years have realized that the current system of generation, transmission and distribution of electric power has become traditional and outdated to meet the entire demand. With that there was a strong growth in research on a concept with new technologies to modernize or build the electric power grid in its aspects of infrastructure, availability, sustainability and reliability. This new concept that is the smart grid that proposes a technology based on automation, communication, monitoring and control of the power grid, which allows implementation of control strategies and grid optimization efficiently before the currently used. The technology applied in smart grid includes many systems. Among these are communication topology systems, circuits and electronic interfaces, which makes it difficult to build a real scenario to carry out studies and researches of which system is best suited for applications in the smart grid. The equipment is very expensive and depending on the extent and amount of devices that will be deployed, make impossible the achievements in the field setting. To remedy these problems are used simulation software that are convenient tools in these cases and commonly employed in the area of research, to conduct the analysis and performance of a system. A communication network involving critical applications, such as electric power transmission and distribution must be highly reliable, extremely safe and resilient. To perform analyses of performance of a wireless communication network to be used in smart grid applications with desirable results, you need to perform simulations in order to anticipate any eventuality of possible failures. Of all existing simulators as indicated was the NS-2, a discrete event simulator for open source networks that facilitates the creation of communication networks scenarios, taking into account the protocols involved in wired or wireless technologies. This software supports the ...

Devido à evolução e à crescente complexidade dos sistemas computacionais, grandes mudanças ocorreram na área de gerenciamento de redes. Os modelos tradicionais centralizados se mostraram limitados, e novos modelos de gerenciamento de redes estão sendo propostos e investigados. Neste cenário, modelos de comunicação P2P permitem a construção de ambientes dinâmicos e versáteis capazes de resolver problemas de diferentes áreas da computação, entre elas o gerenciamento de redes. O modelo P2P torna-se atrativo porque se encaixa perfeitamente no gerenciamento de redes distribuído atualmente solicitado. A partir da proposta de gerenciamento de redes usando P2P e da apresentação de um novo modelo conceitual usando essa nova perspectiva, foi desenvolvido um projeto de arquiteturas para gerenciamento baseadas em P2P, focando-se em entidades tais como peers de gerenciamento Top-Level (TLM) e Mid-Level (MLM). A fim de efetivamente concretizar o gerenciamento baseado em P2P, foram introduzidas definições de blocos básicos para sistemas de gerenciamento baseados em P2P. A integração desses blocos básicos com soluções tradicionais de gerenciamento, tal como a estrutura SNMP, também foi apresentada. Um dos conceitos centrais da arquitetura apresentada são os Serviços de Gerenciamento, que definem as tarefas básicas de gerenciamento do sistema, e foram inspirados nos conceitos de Web Services e na concepção de serviços das Arquiteturas Orientadas a Serviço (SOA). Para a avaliação desse novo modelo de gerenciamento de redes e da arquitetura associada, surgiu a necessidade do desenvolvimento de um protótipo do sistema, com o intuito de servir como uma plataforma para desenvolvimento e implantação de Serviços de Gerenciamento. Esse protótipo é usado para avaliação e análise de testes e resultados associados. Para preservar as características de disponibilidade e escalabilidade que são inerentes dos sistemas P2P, definiu-se que os Serviços de Gerenciamento devem ser disponibilizados por Grupos de MLMs, organizados de forma a fazer a distribuição de tarefas de gerenciamento entre si. Diversos modelos de distribuição de carga foram investigados, foram realizadas avaliações e gráficos comparativos, e foram estabelecidas diretrizes sobre quando e como deve ser aplicado cada modelo, de modo a alcançar sempre o melhor rendimento e a maximização do aproveitamento dos recursos disponíveis ao sistema. A avaliação realizada consistiu na execução de diversas requisições com diferentes números de MLMs usando diferentes algoritmos de distribuição de carga, e na comparação entre a vazão, os tempos de resposta e o tráfego de rede gerados pelos diferentes casos de uso. A implementação desenvolvida neste trabalho demonstrou ser promissora, apresentando resultados bastante satisfatórios com relação aos parâmetros avaliados. / Due to the increasing complexity of computer systems, deep changes have occurred in network management in the past few years. Traditional centralized models have been proved limited, and new network management models are being proposed and investigated. In this scenery, P2P communication models allow for the creation of dynamic and versatile environments, able to solve problems in various computational areas, one of them being network management. The P2P model fits perfectly in the current demands of distributed network management. Starting from the proposed P2P-based network management model, a new P2P-based network management architecture has been developed, focusing on entities like Top-Level (TLM) and Mid-Level (MLM) management peers. With the purpose of making the P2P-based network management real, new building blocks for P2P-based network management systems have been defined. In the present work, an integration of these new building blocks with traditional network management solutions - like SNMP - is presented. One of the main concepts of the proposed architecture is on Management Services, inspired by Web Services and in the service definition of Service Oriented Architectures (SOA). To evaluate this new network management model and its associated architecture, it was necessary to develop a prototype system to be used as platform for development and deployment of Management Services. This prototype was used for evaluation, testing and result analysis. To hold the characteristics of availability and scalability that are inherent to the P2P systems, the Management Services had to be served by MLM groups, organized in a way to distribute the management tasks between them. Several load distribution models were investigated, with evaluation and comparative graphics fulfilled, and some guidelines were established as to when and how each model should be applied to reach the best performance and the maximization of the computational resources available to the system. The evaluation consisted in the execution of several requests in groups with distinct MLM numbers and using distinct load distribution algorithms. Then, the response time and network traffic generated by use cases were compared. We then showed that the developed implementation of our proposal is promising, and presents good results in relation with the evaluated parameters.

Com o intuito de utilizar uma rede com protocolo IP para a implementação de malhas fechadas de controle, este trabalho propõe-se a realizar um estudo da operação de um sistema de controle dinâmico distribuído, comparando-o com a operação de um sistema de controle local convencional. Em geral, a decisão de projetar uma arquitetura de controle distribuído é feita baseada na simplicidade, na redução dos custos e confiabilidade; portanto, um diferencial bastante importante é a utilização da rede IP. O objetivo de uma rede de controle não é transmitir dados digitais, mas dados analógicos amostrados. Assim, métricas usuais em redes de computadores, como quantidade de dados e taxa de transferências, tornam-se secundárias em uma rede de controle. São propostas técnicas para tratar os pacotes que sofrem atrasos e recuperar o desempenho do sistema de controle através da rede IP. A chave para este método é realizar a estimação do conteúdo dos pacotes que sofrem atrasos com base no modelo dinâmico do sistema, mantendo o sistema com um nível adequado de desempenho. O sistema considerado é o controle de um manipulador antropomórfico com dois braços e uma cabeça de visão estéreo totalizando 18 juntas. Os resultados obtidos mostram que se pode recuperar boa parte do desempenho do sistema. / ln order to enable the use of IP networks to implement closed-Ioop control systems, this work compares a distributed control system to its conventional counterpart, which is based on local controI. Usually the option for a distributed control architecture is motivated by simplicity, cost reduction and reliability, hence the use of an IP network. The goal of a control network is not to transmit pure digital data, but to transmit digitized control and sensor signals. Therefore, metrics common in computer networks, such as amount of transfered data and transfer rates, become of little importance. This work proposes a method to compensate for the delays imposed to network packets and to recover the control system performance. The key for this method is to estimate the contents of delayed network packets based on the system dymanic modeI. The example system is an antropormorphic robot with two arms and a stereo vision head. Results show that the system performance can be recovered.