Fundação Araucária / O gerenciamento do tráfego na Internet tornou-se essencial devido à grande utilização de serviços em rede nos últimos anos. Assim, para executar alguns serviços que demandam um certo grau de qualidade é necessário otimizar o uso de recursos existentes. Organizações mantenedoras de backbones são responsáveis por rotear o tráfego, utilizando protocolos que encaminham dados da origem ao destino. Um dos protocolos de roteamento mais utilizados mundialmente é o Open Shortest Path First (OSPF). A qualidade das rotas oferecidas pelo protocolo OSPF depende dos pesos atribuídos pelo operador de rede às ligações (enlaces). A determinação destes pesos depende dos critérios técnicos ou econômicos considerados necessários por parte da empresa provedora de serviços telemáticos. Nesta dissertação aborda-se o problema de rotear a demanda de tráfego na rede com o objetivo de oferecer uma qualidade de serviço satisfatória por meio de uma atribuição inteligente de pesos aos enlaces. O problema de atribuição de pesos (WSP), consiste em encontrar um conjunto de pesos OSPF que otimiza o desempenho da rede. Para solução deste problema, a literatura científica apresenta algoritmos que, na sua maioria, buscam equilibrar o tráfego na rede pelo ajuste correto da carga de cada enlace. Essa dissertação visa solucionar o WSP propondo uma nova abordagem que leva em consideração a perda de pacotes em caminhos origem-destino e a sobrecarga gerada em cada enlace. Também uma formulação estendida é proposta, permitindo a obtenção de um conjunto de pesos operacionais em ambientes normais e em ambientes onde ocorrem falhas de nós. A aplicação de duas heurísticas conhecidas, Simulated Annealing e Harmony Search, a este problema permite encontrar soluções satisfatórias para os critérios de desempenho especificados. / Internet traffic management becomes essential due the large use of the Internet the past decades. Balancing the use of existing IP resources improves the performance of services. Backbone manteiners are responsible for routing data that are sent along the network links from a source to a destination host. A routing protocol is used to perform this task. One of the most commonly used internal routing protocol is OSPF (Open Shortest Path First). The quality of the routes offered by the OSPF protocol mainly depends on weights that are assigned by the network operator to the links. The determination of these weights depends on technical or economic criteria deemed necessary by the ISPs. This master dissertation addresses the routing problem aiming at providing network quality of service by optimizing the weights assigned to links. The weight setting problem (WSP) corresponds to find a set of OSPF weights that optimize network performance. To solve this problem, the literature shows algorithms that mostly seek to balance the network traffic by correctly setting link loads. This work aims at solving WSP proposing a new approach that takes into account packet losses over origin-destination paths and link overhead. Also an extended formulation is proposed, to obtain a set of operating weights in normal environments and in environments where node failures can occur. The application of two well known heuristics, Simulated Annealing and Harmony Search, to this problem allows to find satisfactory solutions to the performance criteria specified.

Investiga-se uma forma de energy harvesting que consiste em recuperar a energia do sinal eletromagnético de rádio frequência (RF), processo que também é conhecido como transferência de energia sem fio. Aplica-se o protocolo time switching (TS) para coordenar o processo de energy harvesting, o qual divide o período de envio de um pacote em dois blocos, o primeiro é dedicado à transferência de energia e o segundo ao envio de informação. A fração do tempo dedicada a cada tarefa, dada pelo parâmetro TS, tem grande impacto no desempenho do sistema. Esta dissertação mostra a investigação do uso do protocolo TS em conjunto com esquemas de retransmissão (HARQ) para o envio da informação. Os resultados mostram que os esquemas HARQ melhoram o desempenho do sistema para a alta relação sinal-ruído (SNR). Essa melhoria é ainda maior quando o destino aplica combinação de Chase entre as diversas cópias do quadro recebido. / We investigate a form of energy harvesting consisting of gathering energy from the radio frequency (RF) electromagnetic waves, also known as wireless power transfer. We employ a time switching (TS) protocol to coordinate the harvesting process, which separates a time slot into two parts, one devoted to wireless energy transfer and the other to wireless information transmission. The fraction of time devoted to each task, the TS parameter, has great impact on the overall performance. This thesis presents an investigation on the usage of the TS protocol, including the numerical optimization of the TS parameter, when hybrid automatic repeat request (HARQ) schemes are used for information transmission. Our results demonstrate that HARQ schemes can improve the system performance for high SNR. This improvement is even better if the destination applies Chase combining among the previously received copies of a frame.

Orientador: Celso de Almeida / Tese (doutorado) - Umiversidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-17T06:29:22Z (GMT). No. of bitstreams: 1 Hoefel_RogerPierreFabris_D.pdf: 16131215 bytes, checksum: 8d67fff6992c05fd8d2eac683e4a1f9e (MD5) Previous issue date: 2000 / Resumo: O objetivo deste trabalho é o de analisar, caracterizar e apresentar soluções para o excitante desafio de projetar protocolos de acesso para o transporte de pacotes multimídia no enlace reverso de sistemas celulares terrestres que empregam interface do ar do tipo TD/DS-CDMA (Time Division/Direct Sequence Code Division Multiple Access). Os estudos relativos aos aspectos inerentes à transmissão de pacotes em sistemas TD/DS-CDMA são particularizados na análise dos protocolos CDMA/PRMA (Code Division Multiple Access/ Packet Reservation Multiple Access) e Slotted CDMA/ALOHA. CDMA/PRMA é um protocolo de múltiplo acesso híbrido, no qual se aplicam os conceitos de multiplexação no tempo~por código e de alocação de recursos por meio de reserva. O acesso controlado ao canal do protocolo CDMA/PRMA permite a redução da variação da carga instantânea do canal e, conseqüentemente, redução da interferência de múltiplo acesso em relação ao protocolo Slotted CDMA/ ALOHA, onde os terminais acessam no próximo slot de tempo tão logo tenham pacotes a transmitir. Utiliza-se simulação computacional de maneira intensiva para à obtenção de resultados concernentes ao desempenho dos protocolos CDMA/PRMA e Slotted CDMA/ ALOHA em distintas condições operacionais. Estes resultados são validados por análises numéricas. Entre outros aspectos deste trabalho, destaca-se: (i) o modelo do ponto de equilíbrio proposto para os protocolos CDMA/PRMA e Slotted CDMA/ ALOHA; (ii) as expressões numéricas propostas para uma análise de desempenho do protocolo CDMA/PRMA; (iii) o desenvolvimento de um simulador de rede de pacotes para a investigação dos efeitos da interferência externa nas redes de pacotes CDMA/PRMA e Slotted CDMA/ ALOHA; (iv) efeitos dos parâmetros de projeto no desempenho dos protocolos CDMA/PRMA e Slotted CDMA/ ALORA; (v) estudo do desempenho dos protocolos CDMA/PRMA e Slotted CDMA/ ALORA com tráfego de vídeo com taxa variável e tráfego de dados WWW; (vi) a investigação dos efeitos do controle de potência, do desvanecimento rápido e do desvanecimento lento no desempenho dos protocolos CDMA/PRMA e Slotted CDMA/ ALORA com tráfego multimídia; (vii) o projeto integrado do protocolo CDMA/PRMA com receptor de detecção conjunta descorrelacionadora / Abstract: This thesis has the objective of to analyze, to characterize and to propose solutions to the challenge of design medium access control protocols for transmission of multimedia packets over the reverse channel of land mobile cellular systems based on TD/DS-CDMA (Time Division/Direct Sequence Code Division Multiple Access) air interface. Some inherent aspects of packet transmission over the reverse link of TD/DS-CDMA systems are particularized in the analysis of the CDMA/PRMA (Code Division Multiple Access/Packet Reservation Multiple Access) and Slotted CDMA/ ALOHA protocols. The joint CDMA/PRMA protocol is a hybrid multiple-access technique that combines time-division, code-division and Reservation ALOHA concepts. The CDMA/PRMA medium access control brings to reduction of the users variance on the channel, so a larger capacity is obtained in relation to the Slotted CDMA/ ALOHA protocol, where a mobile station accesses a time slot as soon as it has packets to transmit. It is used intensely computational simulation techniques to obtain some performance results concerning to CDMA/PRMA Slotted and CDMA/ ALOHA behavior over distinct operational conditions. It is utilized numerical techniques to validate some of obtained results. It is emphasized the following aspects of this Thesis: (i) a equilibrium point analysis model for the CDMA/PRMA and Slotted CDMA/ ALOHA protocols; (ii) some numerical expressions that permits to analyze the CDMA/PRMA behavior on voice-only traffic; (iii) a system level network simulator developed to assess and to compare the intercell interference effects on the CDMA/PRMA and Slotted CDMA/ ALOHA protocols performance; (iv) the design parameters effects on the performance of CDMA/PRMA and Slotted CDMA/ALOHA systems; (v) some studies of CDMA/PRMA and Slotted CDMA/ALOHA behavior on mixed voice/variable bit rate video and voice/WWW browsing traffic; (vi) some analysis of the imperfect power control effects, slow and fast fading effects on the capacity of CDMA/PRMA and Slotted CDMA/ ALOHA protocols; (vii) a integrated design of CDMA/PRMA protocol and a multiuser decorrelator detector / Doutorado / Telecomunicações e Telemática / Doutor em Engenharia Elétrica

Orientadores: Maurício Ferreira Magalhães, Christian Rodolfo Esteve Rothenberg / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-21T12:26:00Z (GMT). No. of bitstreams: 1 Nascimento_MarceloRibeiro_M.pdf: 7752631 bytes, checksum: a40f02ea9677aa4dd611e87beec05ab4 (MD5) Previous issue date: 2012 / Resumo: Os roteadores atuais implementam uma arquitetura verticalmente integrada composta de uma camada de software e um hardware proprietários. Este modelo resulta em soluções de alto custo e inviabiliza a experimentação de novas idéias. Em contrapartida, existem alternativas de alta flexibilidade baseadas em software e, consequentemente, de baixo custo. Entretanto, essas soluções apresentam baixo desempenho. Motivado pela disponibilidade de uma API aberta para programação do plano de encaminhamento (ex. OpenFlow), esta dissertação apresenta uma proposta de arquitetura de roteamento IP com separação de planos. Trata-se de uma abordagem que procura combinar o alto desempenho de hardwares de prateleira (commodities) com a flexibilidade de uma pilha de roteamento executada remotamente em computadores de uso geral. O grande desafio é garantir confiabilidade, escalabilidade e desempenho à rede, a partir de um controle remoto e centralizado sobre uma arquitetura que permita maior flexibilidade no mapeamento entre os elementos de controle e encaminhamento. O resultado corresponde a uma nova proposta de roteamento IP com perspectivas promissoras do ponto de vista do custo e da flexibilidade. Com o objetivo de avaliar a arquitetura proposta foi desenvolvido um protótipo com base em uma versão simplificada do modelo. Os resultados da avaliação apresentados nesta dissertação comprovam a viabilidade da arquitetura / Abstract: Today's networking gear follows the model of computer mainframes, where closed source software runs on proprietary hardware. This approach results in expensive solutions and prevents equipment owners to put new ideas into practice. In contrast, recent alternatives of highly flexible softwarebased routers promise low cost and programmability at the expense of low performance. Motivated by the availability of an open API to control packet forwarding engines (i.e., OpenFlow), we propose a commodity IP routing architecture that combines the line-rate performance of commercial hardware with the flexibility of open source routing stacks (remotely) running on general-purpose computers. The challenge is to ensure reliability, scalability and performance to a network running a remote and centralized control plane architecture that allows a flexible mapping between the control and forwarding elements. The outcome is a novel point in the design space of cost-effective IP routing solutions with far-reaching implications. The initial experimental evaluation of our prototype implementation validates the feasibility of the design / Mestrado / Engenharia de Computação / Mestre em Engenharia Elétrica

Orientador: Mauricio Ferreira Magalhães / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-04T17:32:51Z (GMT). No. of bitstreams: 1 Sazima_Ricardo_M.pdf: 1107563 bytes, checksum: a1179beaec699c0dcd87b45284e4a99c (MD5) Previous issue date: 2004 / Resumo: Dados a banda de transmissão atualmente disponível, o protocolo (IP) utilizado para transmitir a maior parte de tráfego e a quantidade de tráfego e seus requisitos de aos, a Engenharia de Tráfego (TE, de Traffic Engineering) tomou-se um componente cada vez mais importante nas redes de comunicações. O padrão do IETF para enncaminhamento roteamento entitulado Multi-Protocol Label Switching (MPLS) preenche lacunas importantes neste cenário e é peça chave das metodologias de TE mais sofisticadas. Nesta dissertação é apresentado um modelo genérico de TE e uma proposta para uma Plataforma para Experimentos com MPLS (PLEX MPLS) que permite que o usuário defina, execute, e analise configurações de Engenharia de Tráfego com MPLS em uma rede IP. Os principais objetivos da PLEX MPLS são: . Estudo da tecnologia MPLS e suporte a outros trabalhos em andamento no contexto do grupo de estudos em MPLS do DCA . Experimentos com engenharia de tráfego com MPLS: validação das tecnologias e conceitos relacionados . Experimentos didáticos em disciplinas de laboratório de redes. Os principais conceitos de TE e MPLS são apresentados como referência, bem como uma descrição do NIST Switch, a plataforma MPLS escolhida para este trabalho. A análise, projeto e implementação da PLEX MPLS são apresentados, pois formam parte significativa do trabalho desenvolvido. A PLEX não só utiliza, como também estende as funcionalidades oferecidas pelo NIST Switch a fim de oferecer um esquema de TE mais completo e eficiente. Na fase de análise, vemos quais os principais requisitos para a implementação desta plataforma, seguindo uma metodologia de Engenharia de Software. Na fase de projeto, vemos as soluções propostas para os problemas identificados na fase de análise e temos uma especificação dos componentes a serem implementados. Na fase seguinte, discutimos a implementação das principais características dos componentes da PLEX, justificando as decisões tomadas. Para validar a implementação da PLEX de acordo com sua proposta, foram realizados alguns experimentos em uma rede de testes com tráfego real. A execução destes experimentos é descrita e seus resultados analisados. Os resultados obtidos assinalam claramente a importância e utilidade de esquemas de TE baseada em MPLS. Uma interessante metodologia para TE, compilada a partir de várias propostas, é apresentada. Finalmente, apontam-se caminhos a seguir em um trabalho futuro de refinamento da PLEX / Abstract: Given the bandwidth currently available, the protocol (IP) used to transmit most Internet traffic, the quantity of traffic produced and its QoS requirements, Traffic Engineering (TE) has become an increasingly important component of communications networks. IETF's standard for forwarding/routing, which is entitled Multi-Protocol Label Switching (MPLS), presents important solutions in this scenario playing a major role in more sophisticated TE methodologies. This work presents a generic methodology for TE and a proposal for a Platform for Experiments with MPLS (PLEX MPLS) which allows the user to define, execute and analyze Traffic Engineering configurations with MPLS in an IP network. The main goals of PLEX MPLS are: . Study of the M PLS technology and support of other ongoing works with M PLS in the DCA . Traffic Engineering experiments with MPLS: validation of the related concepts and technologies . Support of didactic experiments in academic disciplines. The main concepts of MPLS and TE are presented as reference, as well as a brief description of NIST Switch, the MPLS software chosen for the PLEX MPLS implementation. The analysis, project and implementation of PLEX MPLS are presented, since are significant part of the developed work. PLEX not only uses, but also extends NIST Switch functionalities to offer a more complete and efficient TE scheme. In the analysis phase the main requirements for the PLEX implementation are specified, following a well-known Software Engineering methodology. The solutions found for the problems identified in the analysis phase are presented in the project phase alongside with a specification of the components that will be implemented. In the next phase, the implementation of PLEX is discussed focusing on the most important characteristics of PLEX components and justifying the implementation ecisions. In order to validate PLEX implementation and its proposal, some experiments were made in a test network with reallive traffic. These experiments are described and its results analyzed. The results obtained clearly indicate the importance and utility of TE schemes based on MPLS. Also an interesting TE methodology compiled from several proposals is presented. Finally, possible improvements and future work on PLEX MPLS are indicated. / Mestrado / Engenharia de Computação / Mestre em Engenharia Elétrica

The objective of the research is to design an electro-optic control for the Active Vertical Coupler-based Optical Cross-point Switch (OXS). The electronic control should be implemented on Printed Circuit Board (PCB) and therefore the design will include the PCB design as well. The aim of the electronic control board is to process the headers of the packets prior to entering the OXS to be switched and from the information in the headers, determine the state that the OXS should be configured in. It should then configure the optical cross-point accordingly. The electronic control board should show flexibility in the sense that it can handle different types of traffic and resolve possible contention that may occur. The research seeks to understand the problems associated with Photonic Packet Switching (PPS) networks. Two of the main problems identified in a PPS network are contention resolution and the lack of variable delays for storing optical packets. The OXS was analyzed and found to meet the requirements for future ultra-high speed PPS network technology with its high extinction ratio, wide optical bandwidth, ultra-fast switching speed and low crosstalk levels. Photonic packets were generated with 4-bit, 8-bit or 16-bit headers at a bit rate of 155 Mbit/s followed by a PRBS (Pseudo Random Bit Sequence) payload at 10 Gbit/s. Different scenarios were created with these types of packets and the electro-optic control and OXS were subjected to these scenarios with the aim of testing the flexibility of the electro-optic control to control the OXS. These scenarios include: <ul><li>Fixed length packets arriving synchronously at one input of the OXS. Some packets are destined for output 1, some are destined for output 2 and some are destined for output 3, therefore realizing a 1-to-3 optical switch.</li> <li>Eight variable length packets arriving synchronously at the OXS at one input, all of them destined for one output. The electro-optic control should open the switch cell for the correct amount of time.</li> <li>Three variable length packets arriving synchronously and asynchronously at one input of the OXS. Some packets are destined for output 1 while other packets are destined for output 2. The electro-optic control should open the correct switch cell for the correct amount of time.</li> <li>Two fixed length packets arriving at the OXS synchronously on different input ports at the same time, both destined for the same output port. The electro-optic control should detect the contention and switch the packets in such a way as to resolve the contention.</li> The electro-optic control and OXS managed to switch all these types of data traffic (scenarios) successfully and resolve the contention with an optical delay buffer. The success of the results was measured in two ways. Firstly it was deemed successful if the expected output sequence was measured at the corresponding output ports. Secondly it was successful if the degradation in quality of the packet was not drastic, meaning the output packets should have an BER (Bit Error Rate) of less than 10-9. The quality of the packets was measured in the form of eye diagrams before and after the switching and then compared. The research resulted in the design and implementation of a flexible electro-optic control for the OXS. The problem of contention was resolved for fixed length synchronous packets and a proposal is discussed to store packets for variable lengths of time by using the OXS. This electro-optic control has the potential to control the OXS for traffic with higher complexities and make the OXS compatible with future developments. / Dissertation (MEng (Electronic Engineering))--University of Pretoria, 2008. / Electrical, Electronic and Computer Engineering / MEng / unrestricted

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.

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Innovations in optical communication are expected to transform the landscape of global communications, internet and datacenter networks. This dissertation investigates several important issues in optical communication such as fairness, throughput, blocking probability and differentiated quality of service (QoS). Novel algorithms and new approaches have been presented to improve the performance of optical circuit switching (OCS) and optical burst switching (OBS) for long haul, and datacenter networks. Extensive simulations tests have been conducted to evaluate the effectiveness of the proposed algorithms. These simulation tests were performed over a number of network topologies such as ring, mesh and U.S. Long-Haul, some high processing computing (HPC) topologies such as 2D and 6D mesh torus topologies and modern datacenter topologies such as FatTree and BCube. Two new schemes are proposed for long haul networks to improve throughput and hop count fairness in OBS networks. The idea is motivated by the observation that providing a slightly more priority to longer bursts over short bursts can significantly improve the throughput of the OBS networks without adversely affecting hop-count fairness. The results of extensive performance tests have shown that proposed schemes improve the throughput of optical OBS networks and enhance the hop-count fairness. Another contribution of this dissertation is the research work on developing routing and wavelength assignment schemes in multimode fiber networks. Two additional schemes for long haul networks are presented and evaluated over multimode fiber networks. First for alleviating the fairness problem in OBS networks using wavelength-division multiplexing as well as mode-division multiplexing while the second scheme for achieving higher throughput without sacrificing hop count fairness. We have also shown the significant benefits of using both mode division multiplexing and wavelength division multiplexing in real-life short-distance optical networks such as the optical circuit switching networks used in the hybrid electronic-optical switching architectures for datacenters. We evaluated four mode and wavelength assignment heuristics and compared their throughput performance. We also included preliminary results of impact of the cascaded mode conversion constraint on network throughput. Datacenter and high performance computing networks share a number of common performance goals. Another highly efficient adaptive mode wavelength- routing algorithm is presented over OBS networks to improve throughput of these networks. The effectiveness of the proposed model has been validated by extensive simulation results. In order to optimize bandwidth and maximize throughput of datacenters, an extension of TCP called multipath-TCP (MPTCP) has been evaluated over an OBS network using dense interconnect datacenter topologies. We have proposed a service differentiation scheme using MPTCP over OBS for datacenter traffic. The scheme is evaluated over mixed workload traffic model of datacenters and is shown to provide tangible service differentiation between flows of different priority levels. An adaptive QoS differentiation architecture is proposed for software defined optical datacenter networks using MPTCP over OBS. This scheme prioritizes flows based on current network state.