The Internet, traditionally FTP, e-mail and Web traffic, is increasingly supporting emerging applications such as IP telephony, video conferencing and online games. These new genres of applications have different requirements in terms of throughput and delay than traditional applications. For example, interactive multimedia applications, unlike traditional applications, have more stringent delay constraints and less stringent loss constraints. Unfortunately, the current Internet offers a monolithic best-effort service to all applications without considering their specific requirements. Adaptive RED (ARED) is an Active Queue Management (AQM) technique, which optimizes the router for throughput. Throughput optimization provides acceptable QoS for traditional throughput sensitive applications, but is unfair for these new delay sensitive applications. While previous work has used different classes of QoS at the router to accommodate applications with varying requirements, thus far all have provided just 2 or 3 classes of service for applications to choose from. We propose two AQM mechanisms to optimize router for better overall QoS. Our first mechanism, RED-Worcester, is a simple extension to ARED in order to tune ARED for better average QoS support. Our second mechanism, REDBoston, further extends RED-Worcester to improve the QoS for all flows. Unlike earlier approaches, we do not predefine classes of service, but instead provide a continuum from which applications can choose. We evaluate our approach using NS-2 and present results showing the amount of improvement in QoS achieved by our mechanisms over ARED.

Transportation problems such as traffic congestion and traffic emission draw growing attention along with rapid urbanization and growth of urban transportation sector in developing countries. This dissertation focuses on a series of transportation policies implemented by the government of Beijing and explores their potential effects in the aspect of reducing traffic congestion, improving air quality, and saving energy. This dissertation is composed by three essays. The first essay exploits an idiosyncratic feature of a driving restriction policy and examines the effects of having more vehicles on the road on traffic congestion, ambient air pollution, and contemporaneous health. The findings suggest that traffic congestion has substantial environmental and health externalities in Beijing but that they are also responsive to policy. The second essay explores the effects of opening new subway lines on traffic congestion and ambient air pollution in Beijing. Results show that the expansion of subway networks significantly decreases traffic congestion, and is associated with improvements in air quality in areas located close to the newly opened subway lines. The third essay estimates the price and income elasticities of vehicular gasoline demand to explore the potential effect of fuel tax on transportation gasoline consumption in Beijing.

To rule through choice is to create differentiated options for urban citizens who use public infrastructure and to produce information and price signals that guide decisions. It treats urban residents as rational consumers of public goods. Economists, planners and activists developed the rhetoric and tools of choice over the course of a half-century. This strategy moved from the fringes of planning and policy making to become widely accepted and adopted. How did this manifestation of choice become central to urban policy? What are the consequences of policies that emphasize individual choice? What can be done to make them conform to the ethical standards of planning? The dissertation that follows focuses on the origins and development of choice-based policy-making and the public dispute over it in New York City. Two cases elucidate the rule of choice. School choice and congestion pricing were signature policies for New York City Mayor Michael Bloomberg (2002- 2013). In the 1950s two economists, William Vickrey and Milton Friedman, translated fundamental principles in that discipline into policy proposals in education and transportation governance. When the Bloomberg administration sought to govern education and roadway infrastructure through choice, this strategy became the source of public debate and deliberation. The history and contemporary politics of the two cases provide material for reflecting on core theoretical issues in planning, including the changing nature of liberalism, the meanings and uses of data and rationality and the role of the material world in producing and recreating modes of engaging with urban problems.

Um dos obstáculos para o uso disseminado do multicast na Internet global é o desenvolvimento de protocolos de controle de congestionamento adequados. Um fator que contribui para este problema é a heterogeneidade de equipamentos, enlaces e condições de acesso dos receptores, a qual aumenta a complexidade de implementação e validação destes protocolos. Devido ao multicast poder envolver milhares de receptores simultaneamente, o desafio deste tipo de protocolo se torna ainda maior, pois além das questões relacionadas ao congestionamento da rede, é necessário considerar fatores como sincronismo, controle de feedbacks, equidade de tráfego, entre outros. Por esses motivos, os protocolos de controle de congestionamento multicast têm sido um tópico de intensa pesquisa nos últimos anos. Uma das alternativas para o controle de congestionamento multicast na Internet é o protocolo ALMTF (Adaptive Layered Multicast TCP-Friendly), o qual faz parte do projeto SAM (Sistema Adaptativo Multimídia). Uma vantagem desse algoritmo é inferir o nível de congestionamento da rede, determinando a taxa de recebimento mais apropriada para cada receptor. Além disso, ele realiza o controle da banda recebida, visando à justiça e a imparcialidade com os demais tráfegos concorrentes. O ALMTF foi desenvolvido originalmente em uma Tese de doutorado e teve a sua validação no simulador de redes NS-2 (Network Simulator). Este trabalho tem como objetivo estender o protocolo para uma rede real, implementando, validando os seus mecanismos e propondo novas alternativas que o adaptem para esse ambiente. Além disso, efetuar a comparação dos resultados reais com a simulação, identificando as diferenças e promovendo as pesquisas experimentais na área. / One of the obstacles for the widespread use of the multicast in the global Internet is the development of adequate protocols for congestion control. One factor that contributes for this problem is the heterogeneity of equipments, enlaces and conditions of access of the receivers, which increases the implementation and validation complexity of these protocols. Due to the number (thousands) of receivers simultaneously involved in multicast, the challenge of these protocols is even higher. Besides the issues related to the network congestion, it is necessary to consider factors such as synchronism, feedback control, fairness, among others. For these reasons, the multicast congestion control protocols have been a topic of intense research in recent years. The ALMTF protocol (Adaptive Layered Multicast TCP-Friendly), which is part of project SAM, is one of the alternatives for the multicast congestion control in the Internet. One advantage of this algorithm is its ability to infer the network congestion level, assigning the best receiving rate for each receptor. Besides that, the protocol manages the received rate, aiming to achieve fairness and impartiality with the competing network traffic. The ALMTF was developed originally in a Ph.D. Thesis and had its validation under NS-2 simulator. The goal this work is to extend the protocol ALMTF for a real network, validating its mechanisms and considering new alternatives to adapt it for this environment. Moreover, to make the comparison of the real results with the simulation, being identified the differences and promoting the experimental research in the area.

O presente trabalho analisa e discute a crise de mobilidade cotidiana nas duas últimas décadas, em São Paulo, tendo em vista o agravamento gradativo das condições de circulação viária na metrópole paulistana. Considerando o espaço como produto, condição e meio de reprodução das relações sociais, defendemos a tese de que a atual crise da mobilidade cotidiana advém de um conjunto de medidas que foram formuladas e implantadas através de políticas econômicas de orientação neoliberal, com destaque para os novos meios de financiamento à produção do espaço urbano e à reorganização produtiva da indústria automobilística nacional, bem como para as estratégias voltadas ao incentivo do consumo de bens duráveis, viabilizado pela ampliação das linhas de crédito para a aquisição de bens duráveis, principalmente carros. A esses elementos associam-se outros, tais como: a extensão e a densidade da ocupação urbana, a baixa qualidade dos sistemas de transportes coletivos e o traçado da infraestrutura viária. A apreciação conjunta desses elementos constitui o quadro a partir do qual realizamos nossa análise / This dissertation analyzes and discusses the crisis of daily mobility in the past two decades in São Paulo, caused by the gradual worsening of the conditions of road circulation in the metropolis. Regarding space as a product, a condition and a means of the reproduction of social relations, we put forth the hypothesis that the current crisis of mobility is the outcome of a number of actions that were formulated and implemented as part of neoliberal economic policymaking. Among such actions are the new sources of credit for the production of urban space, the restructuring of the domestic automobile industry and the strategies that encourage the purchase of durable goods (especially cars) made possible by the expansion of consumer credit. Other elements combine with these three basic causes, such as the low quality of public transit systems and the road layout. By taking account of all these elements together, we build the framework upon which we carry out our analysis

A Região Metropolitana de São Paulo (RMSP) sofre de sérios problemas de congestionamento, assim como muitas outras cidades de grande porte. Uma possível solução, proposta por pesquisadores de transportes, economia e ciências ambientais, é a implantação de um sistema de congestion charging, chamada no Brasil de pedágio urbano. Um dos objetivos do presente trabalho foi estabelecer os conceitos relacionados a este assunto e ilustrar as principais questões relacionadas à sua implantação. Espera-se que este trabalho possa auxiliar o desenvolvimento de estudos de avaliação da viabilidade e de impactos de sistemas propostos de congestion charging. Para atingir este objetivo, toca-se em diversos assuntos, como a definição de congestionamento e as formas de medi-lo, a base conceitual e teórica dos sistemas de congestion charging e seus diversos esquemas de diferenciação. São expostas também as medidas de mitigação de congestionamento que já foram implantadas na RMSP, quais foram os estudos já desenvolvidos considerando este tipo de política para a RMSP, e casos em que sistemas de congestion charging já foi implantado. Neste trabalho, desenvolveu-se também um modelo de escolha discreta a partir dos dados da Pesquisa Origem e Destino 2007 do METRÔ, onde pessoas deveriam escolher entre \"Transporte Coletivo\" e \"Transporte Público\". Este modelo foi utilizado para avaliar o potencial de impacto na divisão modal e de arrecadação de um congestion charge aplicado ao centro expandido de São Paulo. Adverte-se, porém, que os resultados obtidos são meramente ilustrativos. Mostra-se, também, que é possível avaliar a capacidade ociosa do sistema de transporte coletivo a partir dos dados disponíveis de bilhetagem e de GPS dos ônibus. Este processo é exemplificado através do cálculo de capacidade de uma única viagem de um único ônibus, dada a dificuldade de automatização deste processo para abranger toda a frota. / The São Paulo Metropolitan Region (SPMR) suffers from severe traffic congestion, as do many other large-scale urban areas around the world. A possible solution to this issue, which has been suggested by transportation, economics and environmental researchers, is the implementation of a congestion charging system. One of the objectives of this project is to establish clear concepts and shed light on the main issues regarding these systems by means of a comprehensive literary review. It is expected that this project may help the development of in-depth studies carried in order to evaluate the viability and impacts of congestion charging proposals. In order to achieve this goal, many subjects are addressed, such as the definition of congestion, how its measured, the theoretical backgrounds that support congestion charging schemes, their different degrees of differentiation, which policies were enacted in order to reduce traffic congestion in São Paulo, what considerations and studies have already been developed for Brazil and São Paulo regarding these systems and where have these systems been successfully installed. Later chapters deal with another goal of this project: estimating how a congestion charging system would affect SPMR. This was achieved through a multinomial logit model, where decision-makers choose between \"Public Transportation\" and \"Private Automobile\". The results presented at this phase are merely indicative of certain tendencies and should not be considered final. This project also attempts to show that given the available Automated Fare Collection (AFC) data and Automated Vehicle Location (AVL) data, it is possible to estimate the current public transportation system\'s unused capacity. The author shows this by calculating the capacity of one bus trip using these data, but also explains the difficulties of expanding this analysis to the whole of SPMR\'s public transportation system.

In a deregulated power market financial transmission rights (FTR) serve as a mechanism for protecting market participants from price variation resulting from network congestion. Possession of FTRs allows participants to recover congestion related losses resulting from unequal locational marginal prices that arise from out of merit dispatch. There exists different strategies for allocating FTR which are in use in the deregulated market. Designing a comprehensive framework for market specific FTR allocation that includes factors like unbalanced FTR, FTR for losses and AC-OPF is currently a major research issue in the deregulated power industry. This thesis develops a method for allocation of financial transmission rights that maximizes revenue while satisfying the system security constraints of alternating current (AC) networks and the revenue adequacy constraint of the financial market. Both the maximization of the FTR revenue and maintaining the constraints are accomplished through solving a modified version of the optimal power flow program. The methodology developed here considers allocation of both balanced and unbalanced point to point FTR obligations. The design of the framework is centered around three main scenarios that arise in the allocation of FTR. In the first scenario the total FTR bid quantity is much less than the total generation quantity available in the network. To maximize revenue the ISO will allocate the entire quantity and needs to only determine the loss quantity associated with the FTR quantity. In the second scenario the total FTR bid quantity is much greater than the total generation quantity available in the network. The ISO is required to determine the maximum allocatable FTR bid per bus in the network for the given generation limit in the network. A novel adaptation of the OPF program that maximizes the total FTR quantity allocated is run in this case to determine the maximum allocatable bid quantities. The third scenario is when the total FTR bid quantity is less than the total generation quantity available in the network but when the losses stipulated by the FTR quantity are added to the bid quantity the total generation capacity is exceeded. Here the novel adaptation of the OPF program is run to determine the maximum allocatable FTR bid quantity per bus (ceiling values). The original FTR bid quantities are then allocated upto the ceiling values determined. When multiple FTR bids are offered on a point-to-point node pair, allocation of FTRs among the bidders for that node pair is done through an auction process. Various auction strategies such as first price uniform, discriminatory auction, and second price uniform auction are considered. The performance of the FTR allocation process is evaluated for the above auction strategies through sample IEEE networks with 9 and 32 buses, available in the MATPOWER software.

The level of air pollution in urban areas, which is largely affected by road traffic, is an issue of high political relevance. Congestion is most prevalent in urban areas and a common and increasingly present phenomenon worldwide. The first four chapters of this study have investigated how and to what extent models, which are used to predict emissions on road links in urban road networks, include the effects of congestion on emissions. In order to make this assessment, traffic engineering literature and empirical studies have been examined and used as a basis to review (current) emission models that exist or have been used around the world. Congestion causes changes in driving patterns of individual vehicles in a traffic stream, and these changes are subsequently reflected in changes in congestion indicators and changes in emission levels. This consideration and a literature review has led to a proposed 'congestion typology' of emission models, which reflects the different ways in which and the extent to which congestion has been incorporated in these models. The typology clarifies that six of in total ten families of emission models that were investigated in this thesis explicitly consider congestion in the modelling process (i.e. model variables are related to congestion), although this is done in different ways. For the remaining four families of emission models it was not possible to determine the extent to which congestion has been incorporated on the basis of literature review alone. Two families fell beyond the scope of this work since they cannot be used to predict emission on road links. For the other two families it became clear in the course of the thesis that the extent can be determined through analysis of driving pattern data (and other information with respect to e.g. data collection) that were used in the model development. A new methodology is presented in this thesis to perform this analysis and to assess the mean level of congestion in driving patterns (driving cycles). The analysis has been carried out for one important family of emission models, the so-called travel speed models ('average speed models'), which are used extensively in urban network modelling. For four current models (COPERT III, MOBILE 6, QGEPA 2002, EMFAC 2000), it is concluded that these models implicitly (i.e. congestion is inherently considered) take varying levels of congestion into account, but that this conclusion is subject to a number of limitations. It became clear in the course of this study that prediction of (the effects of) congestion in both traffic models and emission models is generally restricted to certain modelling dimensions. As a consequence, the effects of congestion are only partially predicted in current air emission modelling. Chapter 5 has attempted to address the question whether congestion is actually an important issue in urban network emission modelling or not. It also addressed the question if different types of emission models actually predict different results. On the basis of a number of selection criteria, two types of models were compared, i.e. one explicit model (TEE-KCF 2002) and two implicit models (COPERT III, QGEPA 2002). The research objectives have been addressed by applying these emission models to a case-study urban network in Australia (Brisbane) for which various model input attributes were collected from different sources (both modelled and field data). The findings are limited by the fact that they follow from one urban network with particular characteristics (fleet composition, signal settings, speed limits) and application of only a few particular emission models. The results therefore indicate that: 1. Changes in traffic activity (i.e. distribution of vehicle kilometres travelled on network links) over the day appear to have the largest effect on predicted traffic emissions. 2. Congestion is an important issue in the modelling of CO and HC emissions. This appears not to be the case for NOx emissions, where basic traffic composition is generally a more important factor. For the most congested parts in the urban network that have been investigated, congestion can more than double predicted emissions of CO and HC. 3. Different types of emission models can produce substantially different results when absolute (arithmetic) differences are considered, but can produce similar results when relative differences (ratio or percent difference) are considered.

Les communications de groupe telles que le multicast IP procurent un moyen efficace pour transmettre simultanément la même donnée vers plusieurs destinataires, comme par exemple pour la diffusion de l'IPTV. Or, il existe une demande pour utiliser le multicast sur des réseaux à capacité variable ou limitée tels que ceux des utilisateurs abonnés à l'ADSL ou ceux utilisés pour les usages mobiles avec un accès sans fil. Dans ces conditions, il est nécessaire de créer un mécanisme de contrôle de congestion pour le multicast capable de partager équitablement la bande passante entre les flux multicast et les flux TCP concurrents. Cette thèse commence par une étude de la latence du temps d'adhésion aux groupes multicast ainsi que son influence sur les différents protocoles existants de contrôle de congestion pour le multicast. Ainsi, nous proposons de créer M2C un protocole de contrôle de congestion prenant en compte cette latence du temps d'adhésion et capable de supporter le passage à très grande échelle. Côté source, M2C utilise des canaux dynamiques semblables à ceux de WEBRC et chaque récepteur M2C dispose d'une fenêtre de congestion mise à jour par des mécanismes de "Slow Start" et de "Congestion Avoidance" qui permettent d'obtenir de façon robuste un partage équitable de la bande passante. De plus, pour converger rapidement vers le débit équitable, un algorithme de "Fast Start" est utilisé au démarrage des sessions M2C. Par ailleurs, un mécanisme permettant de détecter les évolutions du débit équitable réactive le "Slow Start" afin de converger plus rapidement vers le nouveau débit équitable. Le protocole M2C a été implémenté et évalué sur plusieurs environnements complémentaires : aussi bien sur une plateforme locale spécialement mise en place pour ces tests au sein du laboratoire, qu'à travers Internet entre Strasbourg (France), Trondheim (Norvège) et Louvain-la-Neuve (Belgique). L'évaluation se déroule selon des scenarii rigoureux et réalistes : comme par exemple, la concurrence entre une population variable de flux M2C et TCP, avec ou sans bruit de fond tel que les communications courtes produites par la navigation sur des sites web ou la consultation de courriel. Cela permet de mettre en exergue le comportement de M2C grâce à l'évaluation de métriques telles que l'utilisation de la bande passante, le taux de pertes, l'équité, etc. Les canaux dynamiques utilisés par M2C peuvent rendre difficile le développement d'applications. En effet, la source doit être capable d'ordonner ses données en utilisant ces canaux dynamiques dont le débit est recalculé pour chaque paquet envoyé et en permettant à chaque récepteur ayant un débit différent de tirer parti de toutes les données reçues. Ces problèmes sont traités en proposant un séquenceur et une interface de programmation (API) qui permettent d'envoyer les données les plus importantes aux débits reçus par la majorité des récepteurs. Nous avons montré que l'efficacité de ce séquenceur est telle qu'un récepteur recevant N% du débit de la source, alors ce récepteur reçoit les N% les plus importants des données applicatives. De plus, l'API fournie permet à l'application de s'abstraire de connaître les mécanismes utilisés par le séquenceur et par M2C. Cette API est à la fois simple d'utilisation et très efficace pour différents types d'applications. Ainsi, nous l'avons utilisé pour implémenter des logiciels de transfert de fichiers [MUTUAL] et de diffusion de vidéos [MUST], dont les sources sont disponibles publiquement ainsi que celles de M2C~: - [M2C] http://svnet.unistra.fr/mcc/ - [MUTUAL] http://mutual.sourceforge.net/ - [MUST] http://must.sourceforge.net/

<p>The subject of this paper is the congestion tax in Stockholm, Sweden. The study has been conducted with the purpose to examine of how public attitudes towards congestion charging looks and the reason behind the attitude. And also to examine if there are any differences in attitudes between those living inside and outside the payment zones, between men and women and between car owners and those who do not own a car or have a driver's license. The study used a questionnaire sent out electronically to a group of friends of friends and of friends’ family members. The respondents think it´s very important to present a better option if price incitements are to be used; in this case the better option is public transportation. Revenues should be spent so that large amounts go to the public transportation. There were no attitude differences between residents living inside the payment zones and those living outside the payment zones and between men and women. There is an attitude difference between those who own a car and those who do not own a car or have a driver's license. Those who own a car are more negative to the congestion charge than those who do not own a car or have a driver's license. This is believed to diminish if information is given to the public on how the revenue is spent and if congestion charge is introduced in several of the larger cities in Sweden.</p>