As redes de telecomunicações se dividem em redes de longa distância, redes metropolitanas e redes de acesso. As redes de longa distância e metropolitana usufruem a alta capacidade de largura de banda da fibra óptica, enquanto nas redes de acesso há um gargalo de largura de banda por causa do uso de pares de fios e cabo coaxial. Para solucionar este problema e oferecer aos usuários acesso banda larga de baixo custo foram propostas as redes ópticas passivas (passive optical network - PON). A PON é formada por dois elementos básicos, a unidade de rede óptica (optical network unit - ONU), localizada perto dos assinantes, e o terminal de linha óptica (optical line terminal - OLT), localizado próximo ao provedor de serviços. Dentre os padrões disponíveis para redes PON, o Ethernet (EPON), padronizado pelo grupo IEEE 802.3ah, é opção atraente porque ele é bastante difundido nas redes locais. O protocolo de controle multiponto (multipoint control protocol - MPCP), já especificado, é responsável pelo controle de acesso ao meio, fornecendo infra-estrutura de sinalização para transmissão entre OLT e ONUs. Entretanto, o algoritmo de alocação de largura de banda, que realiza o controle de acesso ao meio com base no MPCP, foi considerado fora do escopo de trabalho do grupo de trabalho, permitindo que seja desenvolvido pelos fornecedores de equipamentos. Neste trabalho, arquiteturas de rede EPON e o protocolo MPCP são descritos e algoritmos de alocação de largura de banda são avaliados mediante simulação computacional. São abordados os algoritmos de alocação de largura de banda que integram multiplexação estatística e técnicas para o suporte a classes de serviços diferenciados, com base no esquema de multiplexação por divisão no tempo (time division multiplexing - TDM). Algoritmos que integram a multiplexação por divisão em comprimento de onda (wavelength division multiplexing - WDM) à arquitetura EPON TDM são também investigados. Os algoritmos WDM-TDM permitem a atualização progressiva da EPON que emprega o esquema TDM para WDM. / Telecommunication networks are divided into core, metropolitan and access networks. The core and metropolitan networks use high capacity bandwidth optical fibers, while the access networks have bandwidth bottlenecks because of the use of twisted-pair wires and coaxial cable. To solve this problem and to offers the users broadband access at low cost the use of passive optical networks (PON) is proposed. A PON is formed by two basic elements, the optical network unit (ONU), positioned close to the customers and the optical line terminal (OLT), located close to the service provider. Within the available standards for PON networks, the Ethernet (EPON), standardised by the IEEE group 802.3ah, is an attractive option because it is already widely used in local networks. The multipoint control protocol (MPCP), already specified, is responsible for the media access control, providing signaling infrastructure for transmission between OLT and ONUs. However, the bandwidth allocation algorithm, that controls access based on MPCP, was considered outside the scope of the work group, permitting that this be developed by equipment providers. In this work, EPON architectures and the MPCP protocol are described and bandwidth allocation algorithms are evaluated with computational simulation. Bandwidth allocation algorithms which integrate statistical multiplexing and techniques to support for differentiated classes of service, based on time division multiplexing (TDM) scheme are investigated. Algorithms that integrate wavelength division multiplexing (WDM) to the EPON TDM architecture are also investigated. The WDM-TDM algorithms permit the progressive upgrade of EPON based TDM to WDM schemes.

As redes de telecomunicações se dividem em redes de longa distância, redes metropolitanas e redes de acesso. As redes de longa distância e metropolitana usufruem a alta capacidade de largura de banda da fibra óptica, enquanto nas redes de acesso há um gargalo de largura de banda por causa do uso de pares de fios e cabo coaxial. Para solucionar este problema e oferecer aos usuários acesso banda larga de baixo custo foram propostas as redes ópticas passivas (passive optical network - PON). A PON é formada por dois elementos básicos, a unidade de rede óptica (optical network unit - ONU), localizada perto dos assinantes, e o terminal de linha óptica (optical line terminal - OLT), localizado próximo ao provedor de serviços. Dentre os padrões disponíveis para redes PON, o Ethernet (EPON), padronizado pelo grupo IEEE 802.3ah, é opção atraente porque ele é bastante difundido nas redes locais. O protocolo de controle multiponto (multipoint control protocol - MPCP), já especificado, é responsável pelo controle de acesso ao meio, fornecendo infra-estrutura de sinalização para transmissão entre OLT e ONUs. Entretanto, o algoritmo de alocação de largura de banda, que realiza o controle de acesso ao meio com base no MPCP, foi considerado fora do escopo de trabalho do grupo de trabalho, permitindo que seja desenvolvido pelos fornecedores de equipamentos. Neste trabalho, arquiteturas de rede EPON e o protocolo MPCP são descritos e algoritmos de alocação de largura de banda são avaliados mediante simulação computacional. São abordados os algoritmos de alocação de largura de banda que integram multiplexação estatística e técnicas para o suporte a classes de serviços diferenciados, com base no esquema de multiplexação por divisão no tempo (time division multiplexing - TDM). Algoritmos que integram a multiplexação por divisão em comprimento de onda (wavelength division multiplexing - WDM) à arquitetura EPON TDM são também investigados. Os algoritmos WDM-TDM permitem a atualização progressiva da EPON que emprega o esquema TDM para WDM. / Telecommunication networks are divided into core, metropolitan and access networks. The core and metropolitan networks use high capacity bandwidth optical fibers, while the access networks have bandwidth bottlenecks because of the use of twisted-pair wires and coaxial cable. To solve this problem and to offers the users broadband access at low cost the use of passive optical networks (PON) is proposed. A PON is formed by two basic elements, the optical network unit (ONU), positioned close to the customers and the optical line terminal (OLT), located close to the service provider. Within the available standards for PON networks, the Ethernet (EPON), standardised by the IEEE group 802.3ah, is an attractive option because it is already widely used in local networks. The multipoint control protocol (MPCP), already specified, is responsible for the media access control, providing signaling infrastructure for transmission between OLT and ONUs. However, the bandwidth allocation algorithm, that controls access based on MPCP, was considered outside the scope of the work group, permitting that this be developed by equipment providers. In this work, EPON architectures and the MPCP protocol are described and bandwidth allocation algorithms are evaluated with computational simulation. Bandwidth allocation algorithms which integrate statistical multiplexing and techniques to support for differentiated classes of service, based on time division multiplexing (TDM) scheme are investigated. Algorithms that integrate wavelength division multiplexing (WDM) to the EPON TDM architecture are also investigated. The WDM-TDM algorithms permit the progressive upgrade of EPON based TDM to WDM schemes.

An important goal of modern data networks is to support multiple applications over a single network infrastructure. The combination of data, voice, video and conference traffic, each requiring a unique Quality of Service (QoS), makes resource dimensioning a very challenging task. To guarantee QoS by mere over-provisioning of bandwidth is not viable in the long run, as network resources are expensive. The aim of proper resource dimensioning is to provide the required QoS while making optimal use of the allocated bandwidth. Dimensioning parameters used by service providers today are based on best practice recommendations, and are not necessarily optimal. This dissertation focuses on resource dimensioning for the DiffServ network architecture. Four predefined traffic classes, i.e. Real Time (RT), Interactive Business (IB), Bulk Business (BB) and General Data (GD), needed to be dimensioned in terms of bandwidth allocation and traffic regulation. To perform this task, a study was made of the DiffServ mechanism and the QoS requirements of each class. Traffic generators were required for each class to perform simulations. Our investigations show that the dominating Transport Layer protocol for the RT class is UDP, while TCP is mostly used by the other classes. This led to a separate analysis and requirement for traffic models for UDP and TCP traffic. Analysis of real-world data shows that modern network traffic is characterized by long-range dependency, self-similarity and a very bursty nature. Our evaluation of various traffic models indicates that the Multi-fractal Wavelet Model (MWM) is best for TCP due to its ability to capture long-range dependency and self-similarity. The Markov Modulated Poisson Process (MMPP) is able to model occasional long OFF-periods and burstiness present in UDP traffic. Hence, these two models were used in simulations. A test bed was implemented to evaluate performance of the four traffic classes defined in DiffServ. Traffic was sent through the test bed, while delay and loss was measured. For single class simulations, dimensioning values were obtained while conforming to the QoS specifications. Multi-class simulations investigated the effects of statistical multiplexing on the obtained values. Simulation results for various numerical provisioning factors (PF) were obtained. These factors are used to determine the link data rate as a function of the required average bandwidth and QoS. The use of class-based differentiation for QoS showed that strict delay and loss bounds can be guaranteed, even in the presence of very high (up to 90%) bandwidth utilization. Simulation results showed small deviations from best practice recommendation PF values: A value of 4 is currently used for both RT and IB classes, while 2 is used for the BB class. This dissertation indicates that 3.89 for RT, 3.81 for IB and 2.48 for BB achieve the prescribed QoS more accurately. It was concluded that either the bandwidth distribution among classes, or quality guarantees for the BB class should be adjusted since the RT and IB classes over-performed while BB under-performed. The results contribute to the process of resource dimensioning by adding value to dimensioning parameters through simulation rather than mere intuition or educated guessing. / Dissertation (MEng (Electronic Engineering))--University of Pretoria, 2007. / Electrical, Electronic and Computer Engineering / unrestricted

A garantia de qualidade de serviço (QoS) tem-se demonstrado muito importante em aplicações em tempo real. Este trabalho apresenta um estudo sobre Mecanismos de Policiamento na tecnologia A TM, mais especificamente, sobre o funcionamento do Mecanismo Dual Leaky Bucket, utilizado pela classe de serviço VBR em rede ATM. Para este estudo foi implementado um simulador por software do mecanismo Dual Leaky Bucket. Foram analisados dois tipos de tráfegos de vídeo com compressão MPEG-2, com pouca e muita movimentação. A partir da simulação pôde-se analisar como o erro na definição de parâmetros do contrato de QoS definidos pelo usuário no estabelecimento da conexão pode levar ao aumento na taxa de perda de informações e, conseqüentemente, a degradação da qualidade necessária pela aplicação / The guarantee of quality of service (QoS) has been demonstrating very important in real time applications. This work presents a study on Policing Mechanisms in the ATM technology, more specifically, on the operation of the Dual Leaky Bucket Mechanism, used by the class of service VBR in ATM networks. For this study a Dual Leaky Bucket mechanism simulator by software was implemented. Two kinds of MPEG-2 video traffics were analyzed with a little and a lot of movement. The simulation shows how a mistake in the definition of parameters in the QoS contract, defined by user, during of the connection establishment can leads to increase of information loss rate and, consequently, the degradation of the necessary quality for the application

A garantia de qualidade de serviço (QoS) tem-se demonstrado muito importante em aplicações em tempo real. Este trabalho apresenta um estudo sobre Mecanismos de Policiamento na tecnologia A TM, mais especificamente, sobre o funcionamento do Mecanismo Dual Leaky Bucket, utilizado pela classe de serviço VBR em rede ATM. Para este estudo foi implementado um simulador por software do mecanismo Dual Leaky Bucket. Foram analisados dois tipos de tráfegos de vídeo com compressão MPEG-2, com pouca e muita movimentação. A partir da simulação pôde-se analisar como o erro na definição de parâmetros do contrato de QoS definidos pelo usuário no estabelecimento da conexão pode levar ao aumento na taxa de perda de informações e, conseqüentemente, a degradação da qualidade necessária pela aplicação / The guarantee of quality of service (QoS) has been demonstrating very important in real time applications. This work presents a study on Policing Mechanisms in the ATM technology, more specifically, on the operation of the Dual Leaky Bucket Mechanism, used by the class of service VBR in ATM networks. For this study a Dual Leaky Bucket mechanism simulator by software was implemented. Two kinds of MPEG-2 video traffics were analyzed with a little and a lot of movement. The simulation shows how a mistake in the definition of parameters in the QoS contract, defined by user, during of the connection establishment can leads to increase of information loss rate and, consequently, the degradation of the necessary quality for the application