Previous research on ECN and RED usually considered only a limited traffic domain, focusing on networks with a small number of homogeneous flows. The behavior of RED and ECN congestion control mechanisms in TCP network with many competing heterogeneous flows in the bottleneck link, hasn't been sufficiently explored. This thesis first investigates the behavior and performance of RED with ECN congestion control mechanisms with many heterogeneous TCP Reno flows using the network simulation tool, ns-2. By comparing the simulated performance of RED and ECN routers, this study finds that ECN does provide better goodput and fairness than RED for heterogeneous flows. However, when the demand is held constant, the number of flows generating the demand has a negative effect on performance. Meanwhile, the simulations with many flows demonstrate that the bottleneck router's marking probability must be aggressively increased to provide good ECN performance. Based on these simulation results, an Adaptive ECN algorithm (AECN) was studied to further improve the goodput and fairness of ECN. AECN divides all flows competing for a bottleneck into three flow groups, and deploys a different max for each flow group. Meanwhile, AECN also adjusts min for the robust flow group and max to get higher performance when the number of flows grows large. Furthermore, AECN uses mark-front strategy, instead of mark-tail strategy in standard ECN. A series of AECN simulations were run in ns-2. The simulations show clearly that AECN treats each flow fairer than ECN with the two fairness measurements: Jain's fairness index and visual max-min fairness. AECN has fewer packet drops and alleviates the lockout phenomenon and yields higher goodput than ECN.

The growth of high speed Internet connections has fueled an increase in the demand for high quality streaming video. In order to satisfy timing constraints, streaming video typically uses UDP as the default network transport protocol. Unfortunately, UDP does not have any end-to-end congestion control mechanisms, and so in the absence of higher layer congestion control can lead to unfairness and possibly congestion collapse. While there has been research done in video measurement and characterization using custom tools, to the best of our knowledge, there have been no measurement studies where the researchers had control over a commercial streaming media server and client, and control of the network conditions and content. A goal of this research is to characterize the bitrate response of Windows Streaming Media in response to network-level metrics such as capacity, loss rate, and round-trip time. We build a streaming media test bed that allows us to systematically vary network and content encoding characteristics. We analyze responsiveness by comparing streaming media flows to TCP-friendly flows under various streaming configurations and network conditions. We find Windows Streaming Media has a prominent buffering phase in which it sends data at a bitrate significantly higher than the steady-state rate. Overall, Windows Streaming Media is responsive to available capacity, but is often unfair to TCP. Knowledge of streaming media's response to congestion encountered in the network is important in building networks that better accommodate their turbulence. The additional characteristics we measure can be combined to guide emulation or simulation configurations and network traffic generators for use in further research.

An increasing number of network applications use reliable transport protocols. Applications with constant data transmission recover from loss without major performance disruption, however, applications that send data sporadically, in small packets, also called thin-streams, experience frequently high latencies due to 'Bufferbloat', that reduce the application performance. Active Queue Management mechanisms were proposed to dynamically manage the queues in routers by dropping packets early and reduce these, hence reducing latency. While their deployment to the internet remains an open issue, the proper investigation into how their functioning mechanism impacts latency is the main focus of this work and research questions have been devised to investigate the AQM impact on latency. A range of AQM mechanisms has been evaluated by the research, exploring performance of the methods for latency sensitive network applications. This has explored new single queue AQM mechanisms such as Controlled Delay (CODEL) and Proportional Integral Enhanced (PIE) and Adaptive RED (ARED). The evaluation has shown great improvements in queuing latency when AQM are used over a range of network scenarios. Scheduling AQM algorithms such as FlowQueue CODEL (FQ-CODEL) isolates traffic and minimises the impact of Bufferbloat on flows. The core components of FQ-CODEL, still widely misunderstood at the time of its inception, have been explained in depth by this study and their contribution to reducing latency have been evaluated. The results show significant reductions in queuing latency for thin streams using FQ-CODEL. When TCP is used for thin streams, high application latencies can arise when there are retransmissions, for example after dropping packets by an AQM mechanism. This delay is a result of TCP's loss-based congestion control mechanism that controls sender transmission rate following packet loss. ECN, a marking sender-side improvement to TCP reduces applicationlayer latency without disrupting the overall network performance. The thesis evaluated the benefit of using ECN using a wide range of experiments. The findings show that FQ-CODEL with ECN provides a substantial reduction of application latency compared to a drop-based AQM. Moreover, this study recommends the combination of FQ-CODEL with other mechanisms, to reduce application latency. Mechanisms such as ABE, have been shown to increase aggregate throughput and reduce application latency for thin-stream applications.

A utilização das redes sem fio nos mais diversos segmentos vem crescendo vertiginosamente nos últimos anos. Aliado ao crescimento da utilização das redes, está a diversificação de aplicações utilizadas por todos os usuários, sejam eles corporativos ou domésticos. Isto tem contribuído significativamente para o desenvolvimento de tecnologias que ofereçam mecanismos de qualidade de serviço, de forma a permitir o uso satisfatório de aplicações como voz e vídeo em tempo real. Este trabalho estuda os efeitos que a existência de tráfego de voz e dados em redes sem fio padrão IEEE 802.11 causa no desempenho da rede e por consequência no desempenho das aplicações. Para realizar este estudo foram executadas simulações baseadas em uma rede sem fio com topologia ad hoc, com variações no número de estações e quantidade de tráfego gerado. Foram simulados os padrões 802.11g e 802.11e com o objetivo de analisar o desempenho dos mecanismos de qualidade de serviço e os benefícios que estes mecanismos geram para a transmissão de tráfego em tempo real em redes sem fio padrão IEEE 802.11. Verificou-se que o padrão IEEE 802.11e apresenta um ganho de desempenho para aplicações de tempo real, porém ele apresenta limitações que devem ser consideradas nos projetos de redes sem fio. / The use of wirelles networks in most various sectors has been growing drastically in past years Allied to the wireless networks use, the diversification of applications and services provided can be directly verified whether by home or corporate users. This alliance contributes significantly to the needs of technology development which offer the quality of service mechanisms, allowing satisfactory use of real-time applications like voice and video This paper studies the effects that coexistent voice and data traffic on a IEEE 802.11 standard wireless network cause in the network performance and, consequently, in the applications performance. To make this study a reality, it was necessary to run simulations of a wireless ad hoc topology network, with variations in the number of workstations and the quantity of generated traffic. The 802.11g and 802.11e standards were used in the simulations with the purpose of analyzing the performance of quality of service mechanisms and the benefits they create for the real-time transmissions in IEEE 802.11 standard wireless networks. It was verified that the IEEE 802.11e standard presents a perfomance gain for the real-time applications, but it has limitations that should be considered in wireless networks design.

Orientador: Nunzio Marco Torrisi / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Engenharia da Informação, 2012

A utilização das redes sem fio nos mais diversos segmentos vem crescendo vertiginosamente nos últimos anos. Aliado ao crescimento da utilização das redes, está a diversificação de aplicações utilizadas por todos os usuários, sejam eles corporativos ou domésticos. Isto tem contribuído significativamente para o desenvolvimento de tecnologias que ofereçam mecanismos de qualidade de serviço, de forma a permitir o uso satisfatório de aplicações como voz e vídeo em tempo real. Este trabalho estuda os efeitos que a existência de tráfego de voz e dados em redes sem fio padrão IEEE 802.11 causa no desempenho da rede e por consequência no desempenho das aplicações. Para realizar este estudo foram executadas simulações baseadas em uma rede sem fio com topologia ad hoc, com variações no número de estações e quantidade de tráfego gerado. Foram simulados os padrões 802.11g e 802.11e com o objetivo de analisar o desempenho dos mecanismos de qualidade de serviço e os benefícios que estes mecanismos geram para a transmissão de tráfego em tempo real em redes sem fio padrão IEEE 802.11. Verificou-se que o padrão IEEE 802.11e apresenta um ganho de desempenho para aplicações de tempo real, porém ele apresenta limitações que devem ser consideradas nos projetos de redes sem fio. / The use of wirelles networks in most various sectors has been growing drastically in past years Allied to the wireless networks use, the diversification of applications and services provided can be directly verified whether by home or corporate users. This alliance contributes significantly to the needs of technology development which offer the quality of service mechanisms, allowing satisfactory use of real-time applications like voice and video This paper studies the effects that coexistent voice and data traffic on a IEEE 802.11 standard wireless network cause in the network performance and, consequently, in the applications performance. To make this study a reality, it was necessary to run simulations of a wireless ad hoc topology network, with variations in the number of workstations and the quantity of generated traffic. The 802.11g and 802.11e standards were used in the simulations with the purpose of analyzing the performance of quality of service mechanisms and the benefits they create for the real-time transmissions in IEEE 802.11 standard wireless networks. It was verified that the IEEE 802.11e standard presents a perfomance gain for the real-time applications, but it has limitations that should be considered in wireless networks design.

Made available in DSpace on 2016-04-28T14:56:19Z (GMT). No. of bitstreams: 1 2006 - Luciano Keller.pdf: 334126 bytes, checksum: 61f193dcc02e3911711ef2d11e41f545 (MD5) Previous issue date: 2006-04-27 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The objective was to evaluate the viability use of the system of blocks pressed for the production of seedlings of Inga marginata, Jacaranda puberula and Zeyheria tuberculosa. It was used as containers pressed block (440 cm3/ seedlings), plastic sacks (11x15 cm) and the tubetes of circular section (280 cm3). They were made evaluations of the seedlings, planting simulation in the nursery and definitive planting in the field in ciliary area to river Guand? s margins. It was used as substratum organic composition, ground coal and loamy soil, in the proportion volumetric, 6:2:2. For the making of the blocks, the substratum was moistened, put in metallic form with dimensions of: 60 x 40 x 20 cm (length, width and height) on a wood box with screen bottom (0,5 mm) and pressed by 15 minutes with a hydraulic monkey. After the presage, the blocks presented height of 12 cm. The seeds were sowed in sand and transplanted for the containers, selecting themselves plantules more homogeneous. The comparison was made by the characteristics of the produced seedlings and for his/her acting powder-planting in bags of 20 liters and in the field. At that time of expedition of the seedlings for the field (150 days after the sowing), the seedlings of the three studied species presented satisfactory growth, when produced in the system of blocks pressed unlike the seedlings produced in the tubetes, 150 days after the repicage. Seedlings of Jacaranda puberula produced in tubetes presented estiolation. That was not observed in seedlings of Inga marginata and Zeyheria tuberculosa. In condition of planting controlled seedlings of Inga marginata produced in tubetes presented smaller values of lap diameter and dry weight of the radicular system and seedlings of Jacaranda puberula produced in the pressed blocks presented smaller height values, lap diameter and dry weight of the radicular system, however that no repeating in the field. After the planting in the field mute of Jacaranda puberula produced in tubetes presented smaller survival taxes. There was not difference among the systems of production of the seedlings, when appraised the height and the diameter of lap of the plants 10 months after the planting. The system of pressed blocks was shown technically viable for the production of seedlings of native forest essences. / O objetivo do estudo foi avaliar a viabilidade uso do sistema de blocos prensados para a produ??o de mudas de Inga marginata, Jacaranda puberula e Zeyheria tuberculosa. Utilizou-se como recipientes bloco prensado (440 cm?/muda), sacos pl?sticos (330 cm3) e tubetes de se??o circular (280 cm3). Foram feitas avalia??es das mudas, simula??o de plantio no viveiro e plantio definitivo no campo em ?rea ciliar ?s margens do Rio Guandu, Serop?dica/RJ. Utilizou-se como substrato composto org?nico, moinha de carv?o e solo argiloso, na propor??o volum?trica, 6:2:2. Para a confec??o dos blocos, o substrato foi umedecido, colocado em forma met?lica com dimens?es de: 60 x 40 x 20 cm (comprimento, largura e altura) sobre uma caixa de madeira com fundo de tela (0,5 mm) e prensado por 15 minutos com um macaco hidr?ulico. Ap?s a prensagem, os blocos apresentaram altura de 12 cm. As sementes foram semeadas em areia e transplantadas para os recipientes, selecionando-se as pl?ntulas mais homog?neas. A compara??o foi feita pelas caracter?sticas das mudas produzidas e por seu desempenho p?s-plantio em sacolas de 20 litros e no campo. Na ?poca de expedi??o das mudas para o campo (150 dias ap?s a semeadura), as mudas das tr?s esp?cies apresentaram crescimento satisfat?rio, quando produzidas no sistema de blocos prensados ao contr?rio das mudas produzidas nos tubetes. Mudas de Jacaranda puberula produzidas em tubetes apresentaram estiolamento. Isso n?o foi observado em mudas de Inga marginata e Zeyheria tuberculosa. Em condi??es de plantio controlado mudas de Inga marginata produzidas em tubetes apresentaram menores valores de di?metro de colo e peso seco do sistema radicular e mudas de Jacaranda puberula produzidas nos blocos prensados apresentaram menores valores de altura, di?metro de colo e peso seco do sistema radicular, por?m isso n?o se repetiu no campo. Ap?s o plantio no campo as plantas de Jacaranda puberula produzidas em tubetes apresentaram menores taxas de sobreviv?ncia. N?o houve diferen?a entre os sistemas de produ??o das mudas, quando avaliada a altura e o di?metro de colo das plantas 10 meses ap?s o plantio. O sistema de blocos prensados mostrou-se tecnicamente vi?vel para a produ??o de mudas de ess?ncias florestais nativas.

The Internet Engineering Task Force (IETF) has recently released network mobility standards that allow deployment of TCP/IP networks onboard a vehicle and maintain permanent network connectivity to the Internet via a vehicular mobile router. This recent development opens up new opportunities for providing efficient mobile computing for users on the move, especially for commuters traveling on public transports. Moreover, central and coordinated management of mobility in a single router, rather than by each user device individually, has numerous advantages. In this architecture, however, it becomes challenging to guarantee network performance due to the mobility of the network and inherently vulnerable nature of wireless links. In this thesis, a detailed performance study of onboard networks is conducted. It has been shown that disruptions in the mobile router connectivity can significantly degrade network throughput. Moreover, factors such as the limited wireless bandwidth of the access link, variations in the bandwidth due to technology switching, and the communication diversity of onboard users all contribute to the problem of unfair sharing of wireless bandwidth. By leveraging the fact that all onboard communications go through the mobile router, performance enhancing solutions are proposed that can be deployed in the mobile router to transparently address the throughput and fairness problems. In this architecture, when the route is known in advance and repetitive (e.g. for public transport or a regularly commuting private vehicle), a certain degree of prediction of impending link disruptions is possible. An anticipatory state freezing mechanism is proposed that relies on the prediction of link disruptions to freeze and unfreeze the state machine of TCP, the widely used transport protocol in the Internet. Simulation study shows that TCP throughput has a non-linear relationship with the prediction accuracy. As prediction accuracy increases, throughput problem diminishes quickly. An adaptive mobile router based fairness control mechanism is proposed to address the unfair sharing of wireless bandwidth in highly dynamic scenarios. The fairness is controlled by dynamically estimating the round-trip-times of all onboard TCP connections and transparently adjusting the protocol control parameters at the router. The thesis also discusses implementation issues for the proposed solutions.

Ce mémoire de thèse propose une approche pour l'obtention des bornes des performances temporelles d'une Architecture d'Automatisation en Réseau par preuves itératives de propriétés d'atteignabilité sur un modèle formel de l'architecture. Ces propriétés d'atteignabilité sont définies grâce à un automate observateur temporisé et paramétré, dont les gardes de certaines transitions sont fonction d'un paramètre temporel. A chaque itération, les résultats de preuves permettent de déterminer la valeur de ce paramètre pour la prochaine itération ; un algorithme de recherche par dichotomie assure la convergence des itérations. La mise en œuvre de cette approche sur des architectures de taille non triviale a nécessité le développement d'une méthode d'abstraction qui comporte deux étapes : simplification de la structure et modification des modèles formels des composants figurant dans la structure simplifiée, ceci afin de prendre en compte les phénomènes de concurrence entre requêtes émises par différents composants. Ces contributions formelles et méthodologiques ont été validées expérimentalement par le traitement de plusieurs cas de taille et complexité croissantes, basés sur le protocole Modbus TCP/IP.

Les inhibiteurs de la protéase (PI) du virus de l'immunodéficience humain (VIH) doivent, pour être actifs, pénétrer à l'intérieur des cellules cibles du VIH, comme les lymphocytes et être présents à des concentrations suffisantes au niveau de la protéase virale.<br /> <br />Certaines protéines d'efflux pourraient diminuer les concentrations intracellulaires d'IP. Ce travail étudie la pharmacocinétique intracellulaire des IP et leurs mécanismes de transfert à travers la membrane cellulaire à l'aide de modèles cellulaires.<br /> <br />Les IP pénètrent dans la cellule par diffusion passive et s'accumulent par fixation aux protéines cytosoliques.<br />Nous avons également étudié l'expression de la P-glycoprotéine à l'aide de cellules mononucléées du sang périphérique de patients infectés par le VIH et traités par des multithérapies antivirales à base d'IP.