Orientador: Lee Luan Ling / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-04T02:56:17Z (GMT). No. of bitstreams: 1 Pereira_TatianaBrito_M.pdf: 2502862 bytes, checksum: 4f913e9451b6cbf542c6f1335b1619d8 (MD5) Previous issue date: 2004 / Resumo: O crescimento explosivo e a natureza heterogênea da Internet demandam ferramentas ¿inteligentes¿ que permitam aos protocolos de roteamento adaptarem-se à situação corrente da rede (topologia e situação de congestionamento). Ferramentas inteligentes, porém, significam, na maioria das vezes, grande sobrecarga de processamento e comunicação. O presente trabalho apresenta, além de uma nova estratégia de roteamento OSPF adaptativo baseado em estimação de banda, uma plataforma de simulação capaz de expor o desempenho de uma rede de interconexão submetida (ou não) a esta nova estratégia. A avaliação de desempenho é realizada graças a um modelo, desenvolvido no simulador OPNET, que adiciona ao modelo de um roteador os módulos para estimação de banda e atualização de custos. Os módulos (de estimação de banda e de atualização de custo) adicionados permitem que o protocolo OSPF tome suas decisões de roteamento baseando-se nas condições de congestionamento da rede e nos índices de qualidade desejados para os enlaces. Neste ambiente de simulação, a topologia da rede é representada por um grafo e o tráfego, a que estará sujeita a rede, durante o período de simulação, é especificado por funções de distribuição que atuam durante um intervalo determinado em um roteador específico da rede. A possibilidade de se estabelecer diversas funções de geração de tráfego, atuando a partir de diversos pontos da rede em intervalos independentes, garante certa representação do dinamismo do tráfego encontrado nas redes atuais. Como resultado das simulações, temos uma análise do impacto desta estratégia adaptativa em parâmetros de desempenho de rede, em comparação com o impacto do roteamento OSPF tradicional / Abstract: Internet increase and diversity demand ¿smart¿ tools that could make possible to routing protocols self-adapt to network current state (its topology and congestion situation). Smart tools, although, can result in great processing and communication overload. This work presents, besides a new adaptive OSPF routing strategy based on bandwidth estimations, a simulation platform able to expose results of network performance while experimenting (or not) the proposed adaptive routing strategy. The performance analysis is accomplished due to a model, developed in OPNET network simulator, that adds to a router model modules to bandwidth estimation and link cost updating. These additional modules allow OSPF protocol to take its routing decisions based on network link conditions and on desired link qualities. Network topology is represented by a graph and the traffic presented during simulation is specified by distribution functions acting in specific routers during established intervals. The possibility of configuring various traffic generation functions, acting from various network points in independent intervals, ensures certain network traffic dynamic representation. The simulation results offer an analysis of the proposed OSPF adaptive routing strategy, in comparison to the conventional OSPF routing, in terms of network performance parameters / Mestrado / Telecomunicações e Telemática / Mestre em Engenharia Elétrica

The purpose of this project is to design and create a system that can be used by a wide variety of groups who do projects. The system created has been specifically tailored for a medium-level company that has employees in different locations and levels, and also has customers for whom they do projects.

Braess' paradox is a counter-intuitive phenomenon which can occur in congesting networks. It refers to those cases where the introduction of a new link in the network results in the total travel time on the network increasing. The dissertation starts by introducing the traffic assignment problem and the concept of equilibrium in traffic assignment. The concept of equilibrium is based on Wardrop's first principle that all travellers will attempt to minimize their own travel time regardless of the effect on others. A literature review includes details of a number of papers that have been published investigating theoretical aspects of the paradox. There is also a brief description of Game Theory and the Nash Equilibrium. It has been shown that the equilibrium assignment is an example of Nash Equilibrium. The majority of work that has been published deals with networks where the delay functions that are used to compute the travel times on the links of the network do not include explicit representation of the capacity of the links. In this dissertation a network that is similar in form to the one first presented by Braess was constructed with the difference being that the well-known BPR function was used in the delay functions. This network was used to show that a number of findings that had been presented previously using simpler functions also applied to this network. It was shown that when it occurs, Braess' paradox only occurs over a range of values at relatively low levels of congestion. Real-world networks were then investigated and it was found that similar results occurred to those found in the simpler test networks that are often used in discussions of the paradox. Two methodologies of eliminating the paradox were investigated and the results are presented. / Decision Sciences / M.Sc.

This dissertation focuses on the material transport system design problem (MTSDP), integrating decisions of technology selection and flow network design. This research is motivated by the design of material transport systems (MTS) in manufacturing plants. The objective is to design a MTS with minimum lifetime costs, subject to service requirements, flow network restrictions, and limited resources. We characterize the MTSDP from the perspectives of task requirements, transport technology, and space utilization. A classification is proposed for transport technologies such that instances in the same class share the same properties, and a decision framework is proposed to emphasize the inter-relationships of three major decisions: task clustering, network connecting, and technology selection. We consider fixed and variable costs, arc capacities, and empty travel in our formulations. We propose two solution approaches for the MTSDP. The first is the compact formulation (CF) approach where the three major decisions are handled by a mixed integer non-linear programming (MINLP) formulation. Relaxation techniques are applied to linearize the model. The solution of the resulting linear formulation (MILP) provides a lower bound to that of MINLP. A tightened formulation reduces the computational time by a factor of 3.85. The experiment also shows that when control system costs are significant, designs with multiple-task clusters are more economical than those restricted to single-task clusters. The other approach is clustering/set partition (CSP), where the three decisions are decomposed and solved sequentially. In an example MTS design problem, three methods are compared: CSP, a GREEDY approach from the literature, and enumeration. CSP finds the optimal solution, while GREEDY results in 31% greater costs. A similar comparison with another example is made for the CF and CSP approaches. We apply the CSP approach in a case problem, using data from an auto parts manufacturer. We include flow path crossing constraints and perform experiments to determine solution quality over a range of small problem sizes. The largest difference from optimality is 3.34%, and the average is 0.98%. More importantly, based on these experiments, it seems there is no evidence that the difference percentage grows with an increase in the number of tasks.

Braess' paradox is a counter-intuitive phenomenon which can occur in congesting networks. It refers to those cases where the introduction of a new link in the network results in the total travel time on the network increasing. The dissertation starts by introducing the traffic assignment problem and the concept of equilibrium in traffic assignment. The concept of equilibrium is based on Wardrop's first principle that all travellers will attempt to minimize their own travel time regardless of the effect on others. A literature review includes details of a number of papers that have been published investigating theoretical aspects of the paradox. There is also a brief description of Game Theory and the Nash Equilibrium. It has been shown that the equilibrium assignment is an example of Nash Equilibrium. The majority of work that has been published deals with networks where the delay functions that are used to compute the travel times on the links of the network do not include explicit representation of the capacity of the links. In this dissertation a network that is similar in form to the one first presented by Braess was constructed with the difference being that the well-known BPR function was used in the delay functions. This network was used to show that a number of findings that had been presented previously using simpler functions also applied to this network. It was shown that when it occurs, Braess' paradox only occurs over a range of values at relatively low levels of congestion. Real-world networks were then investigated and it was found that similar results occurred to those found in the simpler test networks that are often used in discussions of the paradox. Two methodologies of eliminating the paradox were investigated and the results are presented. / Decision Sciences / M.Sc.

In this paper we study packet delay and loss rate at the University of Fort Hare network. The focus of this paper is to evaluate the information derived from a multipoint measurement of, University of Fort Hare network which will be collected for a duration of three Months during June 2011 to August 2011 at the TSC uplink and Ethernet hubs outside and inside relative to the Internet firewall host. The specific value of this data set lies in the end to end instrumentation of all devices operating at the packet level, combined with the duration of observation. We will provide measures for the normal day−to−day operation of the University of fort hare network both at off-peak and during peak hours. We expect to show the impact of delay and loss rate at the University of Fort Hare network. The data set will include a number of areas, where service quality (delay and packet loss) is extreme, moderate, good and we will examine the causes and impacts on network users.

As Redes Ad Hoc Veiculares (Veicular Ad Hoc Networks (VANETs)) são redes móveis que possuem como propósito a comunicação entre veículos para fornecer segurança e entretenimento a seus ocupantes. A comunicação pode ocorrer de três modos: Vehicle-to-Vehicle (V2V), Vehicle-to-Infrastructure (V2I) e híbrida (V2V e V2I ao mesmo tempo). As redes V2I e híbridas apresentam elevados custos de construção e manutenção, pois necessitam ser estabelecidas em locais que possuam infraestrutura fixa, o que as tornam impraticáveis na maioria das vezes. As redes V2V, por sua vez, apresentam baixos custos de construção, pois podem ser estabeleci- ˜ das em qualquer ambiente urbano, entretanto dependem do fluxo de veículos nestes ambientes para manter a conectividade e o bom desempenho. Em ambientes urbanos existem basicamente veículos particulares, veículos de transporte pesado, e veículos de transporte coletivo (ônibus). Entre estes, os veículos de transporte coletivo apresentam um comportamento de trafego diferenciado em relação aos demais veículos. Em particular, na cidade de Curitiba, os ônibus pertencentes as linhas expressas trafegam por canaletas exclusivas, segundo um escalonamento ` relativamente regular, em um trajeto linear praticamente sem obstáculos. Estas características sugerem que um sistema que faz uso destes ônibus para a criação de uma infraestrutura de comunicação apresentará um desempenho superior quando comparado a um sistema que não faz distinção entre veículos. Assim sendo, este trabalho propõe a utilização dos ônibus do transporte coletivo urbano para formar uma rede de transporte de dados (backbone) ad hoc móvel (BMVA), a qual irá prover conectividade e aumentar o desempenho da rede sem utilizar infraestrutura fixa. Novos protocolos de roteamento capazes de explorar a conectividade intrínseca fornecida pelo BMVA também são propostos. Estes protocolos foram desenvolvidos tomando-se por base os protocolos AODV, AOMDV e DSDV. Análises estatísticas com dados reais, bem como experimentos de simulação, comprovam que o BMVA e os novos protocolos podem criar uma infraestrutura de comunicação móvel e promover o aumento de métricas de desempenho, como a taxa de entrega e a vazão dos pacotes de dados. / Vehicular Ad Hoc Networks (VANETs) are mobile networks which have as a purpose the communication between vehicles in order to provide safety and entertainment to their users. The communication may occur in three ways: Vehicle-to-Vehicle (V2V), Vehicle-to-Infrastructure (V2I) and hybrid (V2V and V2I at the same time). V2I and hybrid networks have, usually, high costs of implementation and maintenance, for they need to be implemented in places with a fixed infrastructure, which will be impracticable most of the times. V2V networks, on the other hand, have low cost of implementation, for they may be implemented in any urban nvironment. However, V2V networks would depend on the vehicles flow in order to keep connectivity and a good performance. In urban environments there are basically private vehicles, cargo vehicles and public transport vehicles (buses). Of these, the public transport vehicles present a distinct behavior in regard to other vehicles. Specifically, in the city of Curitiba, the buses from express lines travel in exclusive lanes, following a relatively regular schedule, in a linear route with practically no obstacles. These characteristics suggest that a system using those buses for the deployment of a communication infrastructure would present a superior performance if compared to a system which makes no distinction between vehicles. Thus, this work proposes the utilization of public transport urban buses for the implementation of an mobile backbone (BMVA), which will provide connectivity and improve the network performance without using a fixed infrastructure. New routing protocols, capable of exploring the intrinsic connectivity provided by BMVA are also proposed. These protocols were developed from AODV, AOMDV and DSDV protocols. Statistical analyses with real data and simulation experiments, confirm that BMVA and the new protocols can create a mobile communication infrastructure and increase the performance metrics such as delivery rate and throughput.

As Redes Ad Hoc Veiculares (Veicular Ad Hoc Networks (VANETs)) são redes móveis que possuem como propósito a comunicação entre veículos para fornecer segurança e entretenimento a seus ocupantes. A comunicação pode ocorrer de três modos: Vehicle-to-Vehicle (V2V), Vehicle-to-Infrastructure (V2I) e híbrida (V2V e V2I ao mesmo tempo). As redes V2I e híbridas apresentam elevados custos de construção e manutenção, pois necessitam ser estabelecidas em locais que possuam infraestrutura fixa, o que as tornam impraticáveis na maioria das vezes. As redes V2V, por sua vez, apresentam baixos custos de construção, pois podem ser estabeleci- ˜ das em qualquer ambiente urbano, entretanto dependem do fluxo de veículos nestes ambientes para manter a conectividade e o bom desempenho. Em ambientes urbanos existem basicamente veículos particulares, veículos de transporte pesado, e veículos de transporte coletivo (ônibus). Entre estes, os veículos de transporte coletivo apresentam um comportamento de trafego diferenciado em relação aos demais veículos. Em particular, na cidade de Curitiba, os ônibus pertencentes as linhas expressas trafegam por canaletas exclusivas, segundo um escalonamento ` relativamente regular, em um trajeto linear praticamente sem obstáculos. Estas características sugerem que um sistema que faz uso destes ônibus para a criação de uma infraestrutura de comunicação apresentará um desempenho superior quando comparado a um sistema que não faz distinção entre veículos. Assim sendo, este trabalho propõe a utilização dos ônibus do transporte coletivo urbano para formar uma rede de transporte de dados (backbone) ad hoc móvel (BMVA), a qual irá prover conectividade e aumentar o desempenho da rede sem utilizar infraestrutura fixa. Novos protocolos de roteamento capazes de explorar a conectividade intrínseca fornecida pelo BMVA também são propostos. Estes protocolos foram desenvolvidos tomando-se por base os protocolos AODV, AOMDV e DSDV. Análises estatísticas com dados reais, bem como experimentos de simulação, comprovam que o BMVA e os novos protocolos podem criar uma infraestrutura de comunicação móvel e promover o aumento de métricas de desempenho, como a taxa de entrega e a vazão dos pacotes de dados. / Vehicular Ad Hoc Networks (VANETs) are mobile networks which have as a purpose the communication between vehicles in order to provide safety and entertainment to their users. The communication may occur in three ways: Vehicle-to-Vehicle (V2V), Vehicle-to-Infrastructure (V2I) and hybrid (V2V and V2I at the same time). V2I and hybrid networks have, usually, high costs of implementation and maintenance, for they need to be implemented in places with a fixed infrastructure, which will be impracticable most of the times. V2V networks, on the other hand, have low cost of implementation, for they may be implemented in any urban nvironment. However, V2V networks would depend on the vehicles flow in order to keep connectivity and a good performance. In urban environments there are basically private vehicles, cargo vehicles and public transport vehicles (buses). Of these, the public transport vehicles present a distinct behavior in regard to other vehicles. Specifically, in the city of Curitiba, the buses from express lines travel in exclusive lanes, following a relatively regular schedule, in a linear route with practically no obstacles. These characteristics suggest that a system using those buses for the deployment of a communication infrastructure would present a superior performance if compared to a system which makes no distinction between vehicles. Thus, this work proposes the utilization of public transport urban buses for the implementation of an mobile backbone (BMVA), which will provide connectivity and improve the network performance without using a fixed infrastructure. New routing protocols, capable of exploring the intrinsic connectivity provided by BMVA are also proposed. These protocols were developed from AODV, AOMDV and DSDV protocols. Statistical analyses with real data and simulation experiments, confirm that BMVA and the new protocols can create a mobile communication infrastructure and increase the performance metrics such as delivery rate and throughput.