A scheduling algorithm has the primary role in implementing the quality of service guaranteed to each flow by managing buffer space and selecting which packet to send next with a fair share of network. In this thesis, some scheduling algorithms for packet switching networks are studied. For evaluating their delay, jitter and throughput performances, a discrete event simulator has been developed. It has been seen that fair scheduling provides, fair allocation of bandwidth, lower delay for sources using less than their full share of bandwidth and protection from ill-behaved resources.

In this thesis, an extensive simulation study is done to gauge the performance of parallel access to multiple mirror sites on the Internet. The study is based on the Digital Fountain approach designed by J. Byers et al. in which Tornado codes are used to minimize decoding time at the expense of injecting extra packets into the system. In this study, both Reed-Solomon and Tornado codes are considered. The results indicate that randomly permuting the packets at every mirror site is not the optimal solution. A new technique, which staggers the packets, is shown to be superior. This study employs OPNET Modeler, which is a powerful event driven simulation tool. Simulations results show that using Reed-Solomon codes with staggered packet transmission provides dramatically improved system performance.

Os backbones IP utilizam protocolos de roteamento do tipo estado do enlace para definir as rotas corretamente. Em situações de mudança na topologia, como uma falha, esses protocolos necessitam de um tempo para reagir e encontrar novas rotas. Durante esse tempo, as rotas ficam instáveis com alta taxa de pacotes perdidos e queda na confiabilidade do backbone. Esse trabalho propõe uma abordagem pró-ativa denominada Esquema de Caminhos Emergenciais Rápidos para auxiliar o protocolo de roteamento OSPF a reduzir a taxa de pacotes perdidos durante esse período. Essa abordagem realiza cálculos reutilizando a base de informações de roteamento do OSPF para gerar esses caminhos emergenciais, que são representados na tabela de encaminhamento através de marcas. Essas marcas são utilizadas então para guiar corretamente os pacotes no contorno de uma falha. Essa abordagem é avaliada em representações de topologias artificiais e reais, e também em simulação para analisar qual o ganho obtido na redução de pacotes perdidos em relação ao OSPF original. A abordagem desenvolvida demonstra resultados bastante satisfatórios em termos de extensão dos caminhos de recuperação utilizados e quantidade de informações extras adicionadas na tabela de encaminhamento em relação à abordagem concorrente. / IP network backbones use link state routing protocols to find correct routes. In face of a topology change, e.g. a failure, these protocols need some time to react to it in order to find new routes. During this time, the routes become unstable, causing high packet loss rate and depreciation of backbone reliability. This work presents a proactive approach named Fast Emergency Paths Schema to help the OSPF routing protocol during the convergence period in order to reduce packet loss rate. The approach conducts calculations reusing the routing information base of the OSPF in order to generate these emergency paths, which are represented in the forwarding table as marks. These are then used to guide the packets to correctly bypass a failure. The approach is evaluated by using various artificial and real topologies, and a simulation is also implemented in order to analyze the packet loss rate reduction in relation to the original OSPF. The analysis yielded satisfactory results in terms of the extension of the recovery paths used and of the amount of extra information added to the forwarding table in relation to the concurrent approach.

Os backbones IP utilizam protocolos de roteamento do tipo estado do enlace para definir as rotas corretamente. Em situações de mudança na topologia, como uma falha, esses protocolos necessitam de um tempo para reagir e encontrar novas rotas. Durante esse tempo, as rotas ficam instáveis com alta taxa de pacotes perdidos e queda na confiabilidade do backbone. Esse trabalho propõe uma abordagem pró-ativa denominada Esquema de Caminhos Emergenciais Rápidos para auxiliar o protocolo de roteamento OSPF a reduzir a taxa de pacotes perdidos durante esse período. Essa abordagem realiza cálculos reutilizando a base de informações de roteamento do OSPF para gerar esses caminhos emergenciais, que são representados na tabela de encaminhamento através de marcas. Essas marcas são utilizadas então para guiar corretamente os pacotes no contorno de uma falha. Essa abordagem é avaliada em representações de topologias artificiais e reais, e também em simulação para analisar qual o ganho obtido na redução de pacotes perdidos em relação ao OSPF original. A abordagem desenvolvida demonstra resultados bastante satisfatórios em termos de extensão dos caminhos de recuperação utilizados e quantidade de informações extras adicionadas na tabela de encaminhamento em relação à abordagem concorrente. / IP network backbones use link state routing protocols to find correct routes. In face of a topology change, e.g. a failure, these protocols need some time to react to it in order to find new routes. During this time, the routes become unstable, causing high packet loss rate and depreciation of backbone reliability. This work presents a proactive approach named Fast Emergency Paths Schema to help the OSPF routing protocol during the convergence period in order to reduce packet loss rate. The approach conducts calculations reusing the routing information base of the OSPF in order to generate these emergency paths, which are represented in the forwarding table as marks. These are then used to guide the packets to correctly bypass a failure. The approach is evaluated by using various artificial and real topologies, and a simulation is also implemented in order to analyze the packet loss rate reduction in relation to the original OSPF. The analysis yielded satisfactory results in terms of the extension of the recovery paths used and of the amount of extra information added to the forwarding table in relation to the concurrent approach.

Orientadores: Edson Moschim, Felipe Rudge / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-05T07:30:34Z (GMT). No. of bitstreams: 1 MaiaJunior_Decio_M.pdf: 1427591 bytes, checksum: 104d0be2f7926f963a037d44ed4df46a (MD5) Previous issue date: 2005 / Resumo: Um novo sistema para geração, chaveamento e roteamento de pacotes ópticos é descrito, visando aplicação em nós de redes ópticas de próxima geração (NGON). Os pacotes ópticos são compostos por um campo de cabeçalho em freqüência e um campo de carga útil digital de alta capacidade (~Gb/s). Os nós de chaveamento óptico incluem as funcionalidades de bloqueio, roteamento e retirada de pacotes, e são controlados por circuitos eletrônicos lógicos que rapidamente processam a informação contida no cabeçalho dos pacotes ópticos, permitindo baixa latência. O chaveamento é realizado pacote-a-pacote, e o tempo de reconhecimento do cabeçalho e chaveamento dos pacotes ópticos é de alguns micro-segundos (~ms) . Este sistema apresenta arquitetura simples, operação eficiente, e pode ser visto como uma solução atrativa nos aspectos técnicos e econômicos, aplicável a redes metropolitanas de acesso e, demonstra-se totalmente compatível com redes ópticas WDM / Abstract: A new system for the generation, switching and routing of optical packets is described, aimed for use in nodes of next-generation optical networks (NGON). The optical packets are composed of an in-band frequency tone header, and a high-capacity transparent digital payload (~Gb/s), occupying separate fields. The optical node switching action includes blocking, routing and drop functions, controlled by electronic logic circuits, performed on a packet-by-packet basis, with only the header information being processed. Total header processing and optical packet switching time is few micro seconds (~ms). This system is designed as a techno-economical solution for metro-access transport, having low latency and low packet loss, being fully compatible with WDM optical networks / Mestrado / Eletrônica, Microeletrônica e Optoeletrônica / Mestre em Engenharia Elétrica

Orientador: Helio Waldman / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-04T02:43:44Z (GMT). No. of bitstreams: 1 Pelegrini_JeffersonUmebara_M.pdf: 9774514 bytes, checksum: 601fa158903b12a1dc6e0d70b70ae8d2 (MD5) Previous issue date: 2005 / Mestrado / Telecomunicações e Telemática / Mestre em Engenharia Elétrica

Cílem bylo navrhnout dva simulační scénáře v prostředí NS-3. První scénář obsahuje ARQ (Automatic Repeat Request) metody v TCP (Transmission Control Protocol). Je v něm porovnání Stop-and-Wait, Go-Back-N a Selective-Repeat metod. Teoretická část obsahuje TCP a ARQ. Druhý scénář je o způsobech přenosu zpráv. Vytvořený scénář převážně s komutací paketů a buněk a teoretické základy jsou obsaženy v práci. Je v něm porovnání metod komutací s různou velikostí paketu/buňky, počtem uzlů a důsledek zpoždění v každé metodě. Scénáře jsou ve formě laboratorní úlohy s instrukcemi k vypracování.

The goal of this thesis was to design two complex scenarios with focus on different kinds of transmission in packet-switched networks. First scenario is about ARQ (Automatic Repeat Request) protocols. It consists of introduction to Stop-and-Wait, Go Back N and Selective Repeat protocols and their comparison. Second scenario compares unicast, multicast, broadcast and anycast transmission methods. Both scenarios use applications which can simulate particular methods or protocols. These applications along with virtual environments are used for demonstration of characteristics of these methods/protocols.

The diploma thesis aimed at the study of the topic of communication protocols and several transmission modes, as well as ARQ (Automatic Repeat Request) mechanisms. Subsequently, the task was to design and describe individual scenarios for their simulation. As a part of solving the mentioned task, it was necessary to create an application that allows the emulation of the behaviour of communication protocols without the need for a transmission in the real network a nd the requirements for the edition of the source code. The application was created in the Microsoft Visual Studio 2017 development environment using the C# programming language and .NET framework and it consists of a library and a graphical interface. The output of the solution is the application of a mode simulator of the data transmission in the network with two scenarios with the prepared input situations in the frame of graphical environment together with instructions, additional tasks and sample solutions. The program allows the simulation of the behaviour of communication protocols between the client and the server without the need for a transmission in a real network. In conclusion, the simulator of data transfer was created in the form of the desktop application which contains two scenarios. The first scenario is used to simulate ARQ mechanisms and the second one is active in the simulation of commutation of messages, circuits, packets or cells.

La fibre optique demeure le support de transmission le plus utilisé, portant le trafic à une énergie par bit relativement faible. Cependant, à cause de l’absence de mémoire toutoptique pratique, la commutation de paquets est toujours exécutée électriquement. Les conversions Optiques Électriques Optiques (O-E-O) nécessaires font de la commutation l’un des domaines les plus consommateurs d’énergie. Ce problème est de plus en plus important spécialement avec la croissance exponentielle du trafic dans les réseaux optiques. Un défi majeur à prendre en considération dans la conception de futurs réseaux optiques est la restriction de leur consommation énergétique. De ce fait, dans le cadre de cette thèse, nous étudions un commutateur hybride opto-électronique qui consiste en une matrice de commutation optique complétée par une mémoire électronique partagée. L’analyse de performance prenant en compte différentes classes de service, distributions de paquets et méthodes de connectivité du commutateur (canaux WDMet/ou SDM), montre que, grâce aux stratégies de commutation établies, le commutateur hybride répond aux besoins de toutes les classes de service en termes de taux de perte de paquets, la charge durable du système et la latence. De plus, il réduit significativement les conversions O-E-O par rapport aux commutateurs électriques commercialisés, puisqu’ils n’auront lieu que pour les paquets mis en mémoire d’attente. Nous défendons que le commutateur de paquets hybride opto-électronique satisfait les exigences en qualité de service et pourrait être une solution prometteuse pour réduire la consommation d’énergie des réseaux optiques. / Most transmission systems are based on optical fibers, carrying the traffic at a relatively low energy per bit. However, due to the lack of mature optical buffers, packet switching is still performed electrically. The required Optical-Electrical-Optical (O-E-O) conversions make the switching one of the areas with the fastest-growing energy consumption. A major challenge that must be met in designing future optical networks is curbing their energy consumption. Therefore, within this thesis, we investigate a hybrid optoelectronic switch which consists of an optical switching matrix supplemented with a shared electronic buffer. Performance analysis taking into account different classes of service, packet classifications and switch connectivity methods (WDM and/or SDM channels), shows that, thanks to the established switching strategies, the hybrid switch satisfies the requirements of all the different classes of service in terms of Packet Loss Rate, sustainable system load and latency. Moreover, it significantly reduces the O-E-O conversions compared to commercial off-the-shelf electrical switches, since they occur only for buffered packets. We defend that the hybrid opto-electronic packet switch meets the requirements on quality of service and could be a promising solution to reduce the energy consumption of optical networks.