Available Bandwidth Inference Based On Node-Centric Clusters

End-to-End Available Bandwidth (AB) is a real-time network metric that is useful for a wide range of applications including content distribution networks, multimedia streaming applications and overlay networks. In a large network with several thousand nodes, it is infeasible to perform all-pair bandwidth measurements as AB measurements could induce traffic overhead along the path. Also because of its dynamic nature, the measurements have to be performed frequently thus imposing significant probe traffic overhead on the network. In this paper, we discuss a clustering based distributed algorithm to infer the AB between any pair of nodes in a large network based on measurements performed on a subset of end-to-end paths. The algorithm was validated on Planet-Lab and for some nodes, 80% of the inferences were within 50% of the actual value

DECENTRALIZED NETWORK BANDWIDTH PREDICTION AND NODE SEARCH

As modern computing becomes increasingly data-intensive and distributed, it is becoming crucial to effectively manage and exploit end-to-end network bandwidth information from hosts on wide-area networks. Inspired by the finding that Internet bandwidth can be represented approximately in a tree metric space, we focus on three specific research problems. First, we have designed a decentralized algorithm for network bandwidth prediction. The algorithm embeds the bandwidth information as distance in an edge-weighted tree, without performing full n-to-n measurements. No central and fixed infrastructure is required. Each joining node performs a limited number of sampling measurements. Second, we designed a decentralized algorithm to search for a centroid node that has high-bandwidth connections with a given set of nodes. The algorithm can find a centroid accurately and efficiently using the bandwidth data produced by the prediction algorithm. Last, we have designed another type of decentralized search algorithm to find a cluster of nodes that have high-bandwidth interconnections. While the clustering problem is NP-complete in a general graph, our algorithm runs in polynomial time with the bandwidth data predicted in a tree metric space. We provide proofs that our algorithms for bandwidth prediction and node search have perfect accuracy and high scalability when a network is modeled as a tree metric space. Also, experimental results with real-world data sets validate the high accuracy and scalability of our approaches

Design and Evaluation of Distributed Algorithms for Placement of Network Services

Network services play an important role in the Internet today. They serve as data caches for websites, servers for multiplayer games and relay nodes for Voice over IP: VoIP) conversations. While much research has focused on the design of such services, little attention has been focused on their actual placement. This placement can impact the quality of the service, especially if low latency is a requirement. These services can be located on nodes in the network itself, making these nodes supernodes. Typically supernodes are selected in either a proprietary or ad hoc fashion, where a study of this placement is either unavailable or unnecessary. Previous research dealt with the only pieces of the problem, such as finding the location of caches for a static topology, or selecting better routes for relays in VoIP. However, a comprehensive solution is needed for dynamic applications such as multiplayer games or P2P VoIP services. These applications adapt quickly and need solutions based on the immediate demands of the network. In this thesis we develop distributed algorithms to assign nodes the role of a supernode. This research first builds off of prior work by modifying an existing assignment algorithm and implementing it in a distributed system called Supernode Placement in Overlay Topologies: SPOT). New algorithms are developed to assign nodes the supernode role. These algorithms are then evaluated in SPOT to demonstrate improved SN assignment and scalability. Through a series of simulation, emulation, and experimentation insight is gained into the critical issues associated with allocating resources to perform the role of supernodes. Our contributions include distributed algorithms to assign nodes as supernodes, an open source fully functional distributed supernode allocation system, an evaluation of the system in diverse networking environments, and a simulator called SPOTsim which demonstrates the scalability of the system to thousands of nodes. An example of an application deploying such a system is also presented along with the empirical results

Evaluation of the applicability of available bandwidth estimation techniques and tools

La estimación del ancho de banda disponible en una red de extremo a extremo, es útil porque permite mejorar el rendimiento de las aplicaciones de red, sin embargo las Técnicas y Herramientas de Estimación de Ancho de Banda Disponible proveen medidas inexactas, en parte por la naturaleza variable del tráfico cruzado y en parte porque se generan errores asociados a la infraestructura de la red. Incrementar la precisión de la medición implica incrementar también el overhead y el tiempo de respuesta de la herramienta de estimación. Es decir, que se gana en una métrica a expensas de otras, por lo que se hace necesario clasificar las herramientas de estimación de ancho de banda disponible de manera que para una aplicación determinada pueda seleccionarse aquella que se adapte mejor para favorecer la métrica que se requiera en dicho escenario, a saber, exactitud de la medición, nivel de overhead, tiempo de convergencia de la herramienta o confiabilidad de la medición. Este trabajo presenta una extensa evaluación de las técnicas y herramientas de medición de ancho de banda disponible desde los enfoques analítico y experimental realizados en un banco de pruebas flexible y controlado y una taxonomía de las aplicaciones que pueden beneficiarse de la información sobre la capacidad disponible en una red de conmutación de paquetes. Los resultados de la evaluación objeto de este proyecto muestran que las herramientas de estimación concentran su desempeño en una de tres métricas: la disminución del error de estimación, la rapidez en la estimación o la disminución en la cantidad de tráfico adicional insertado a la red para realizar la estimación. Todas las herramientas afectan una de las métricas para obtener adecuados resultados en las otras. La revisión de la literatura utilizada para la configuración del presente trabajo consideró a más de 30 artículos seleccionados por su relevancia en cuanto a la descripción de herramientas de estimación de ancho de banda disponible, la presentación de resultados de evaluación de estimadores y la descripción de ambientes controlados de evaluación. Estos artículos se obtuvieron a través de Google Scholar y su referencia a bases de datos de ACM, IEEE y Sciece Direct, principalmente.RESUMEN ……………………………………………………………………………… 11 INTRODUCCIÓN 12 1. MARCO TEORICO 15 1.1 Antecedentes 15 1.1.1 Vía de Extremo a Extremo (End-to-End Path) 16 1.1.2 Ancho de Banda Disponible de Extremo a Extremo 16 1.1.3 Medición del Ancho de Banda Disponible 17 1.2 Dificultades para la Medición del Ancho de Banda Disponible 18 1.2.1 Medición de Tiempo del Sistema 19 1.2.2 Capacidad de Procesamiento de Host de Extremo 21 1.2.3 Patologías de Extremo a Extremo 21 1.2.4 Comportamiento de Cola 22 1.3 Formulación del Problema 22 2. ESTADO DEL ARTE 24 2.1 Técnicas de Medición del Ancho de Banda Disponible 24 2.1.1 Probe Gap Model (PGM) (Modelo de Separación de Pruebas) 25 2.1.2 Probe Rate Model (PRM) (Modelo de Velocidad de Prueba) 27 2.2 Herramientas de Medición del Ancho de Banda Disponible 28 2.2.1 Spruce 28 2.2.2 Abing 30 2.2.3 IGI 31 2.2.4 Pathload 35 2.2.5 Pathchirp 39 3. EVALUACIÓN DE LAS HERRAMIENTAS ACTUALES DE MEDICIÓN DE ANCHO DE BANDA DISPONIBLE 411 3.1 Métricas de Rendimiento 422 3.2 Testbed 444 3.3 Evaluación de Ancho de Banda Disponible con Base Analítica 466 3.3.1 Modelo de Redes cola de Jackson 477 3.3.2 Procesos Estocásticos 488 3.3.3 Experimentos 544 3.3.4 Resultados 566 3.3.4.1 Error de Medición ………………………………………………………56 3.3.4.2 Overhead ………………………………………………………………. 57 3.3.4.3 Tiempo de Medición ………………………………………………….. 58 3.5 Evaluación Experimental del Ancho de Banda Disponible 59 3.5.1 El Diseño Factorial 2k 600 3.5.2 Métricas Utilizadas ………………………………………………………… 62 3.5.3 Matriz de Diseño 644 3.5.4 Estimación de los Efectos Significativos 655 3.6 Análisis de la Varianza 666 3.6.1 Análisis de la Varianza para la Herramienta Pathload 666 3.6.1.1 Análisis de la Varianza de la Métrica Tiempo de Estimación para la Herramienta Pathload ……………………………………………………………. 66 3.6.1.2 Análisis de la Varianza de la Métrica Error de Estimación para la Herramienta Pathload…………………………………………………………….. 71 3.6.1.3 Análisis de la Varianza de la Métrica Overhead para la Herramienta Pathload ……………………………………………………………. 73 3.6.2 Análisis de la Varianza para la Herramienta IGI 777 3.6.2.1 Análisis de la Varianza de la Métrica Tiempo de Estimación para la Herramienta IGI …………………………………………………………………… 77 3.6.2.2 Análisis de la Varianza de la Métrica Error de Estimación para la Herramienta IGI …………………………………………………………………… 81 3.6.2.3 Análisis de la Varianza de la Métrica Overhead para la Herramienta IGI …………………………………………………………………… 83 3.6.3. Análisis de la Varianza para la Herramienta SPRUCE 866 3.6.3.1 Análisis de la Varianza de la Métrica Tiempo de Estimación para la Herramienta SPRUCE……………………………………………………………. 86 3.6.3.2 Análisis de la Varianza de la Métrica Error de Estimación para la Herramienta SPRUCE …………………………………………………………… 90 3.6.3.3 Análisis de la Varianza de la Métrica Overhead para la Herramienta SPRUCE …………………………………………………………… 93 3.6.4 Análisis de la Varianza de la Métrica Confiabilidad 966 3.6.5 Resumen de los efectos producidos por la variación de los factores en cada una de las métricas 99 3.7 Resultados de los experimentos ……………………………………………. 102 3.7.1 Capacidad Variable del Tight Link 1022 3.7.2 Retardo de Propagación Variable Unidireccional 1055 3.7.3 Tasa Variable de Pérdida Paquetes o (Variable Packet Loss Rates) 1066 3.7.4 Cantidad Variable de Tráfico Cruzado 10808 3.7.5 Tamaño Variable de Paquetes de Tráfico Cruzado 10909 3.8 Aplicabilidad de las Actuales Herramientas de Medición de Ancho de Banda Disponible 10909 4. CONCLUSIONES Y TRABAJO FUTURO 1166 4.1 Conclusiones 1166 4.2 Trabajo Futuro 11717 BIBLIOGRAFIA 11919MaestríaEstimating the available bandwidth in an end-to-end network is useful because it allows improving the performance of network applications, however the Available Bandwidth Estimation Techniques and Tools provide inaccurate measurements, partly due to their nature. variable of cross traffic and partly because errors associated with the network infrastructure are generated. Increasing the accuracy of the measurement also means increasing the overhead and response time of the estimation tool. That is, it is gained in one metric at the expense of others, so it is necessary to classify the available bandwidth estimation tools so that for a given application the one that best suits can be selected to favor the metric that is used. required in such a scenario, namely, measurement accuracy, overhead level, tool convergence time, or measurement reliability. This work presents an extensive evaluation of the available bandwidth measurement techniques and tools from analytical and experimental approaches performed in a flexible and controlled test bed and a taxonomy of applications that can benefit from the information on the capacity available in a packet switched network. The results of the evaluation object of this project show that the estimation tools concentrate their performance on one of three metrics: the decrease in the estimation error, the speed in the estimation or the decrease in the amount of additional traffic inserted into the network to make the estimate. All the tools affect one of the metrics to obtain adequate results in the others. The review of the literature used for the configuration of this work considered more than 30 articles selected for their relevance in terms of the description of available bandwidth estimation tools, the presentation of estimator evaluation results and the description of environments. controlled evaluation. These articles were obtained through Google Scholar and its reference to ACM, IEEE and Sciece Direct databases, mainly.Modalidad Presencia

Doctor of Philosophy

dissertationNetwork emulation has become an indispensable tool for the conduct of research in networking and distributed systems. It offers more realism than simulation and more control and repeatability than experimentation on a live network. However, emulation testbeds face a number of challenges, most prominently realism and scale. Because emulation allows the creation of arbitrary networks exhibiting a wide range of conditions, there is no guarantee that emulated topologies reflect real networks; the burden of selecting parameters to create a realistic environment is on the experimenter. While there are a number of techniques for measuring the end-to-end properties of real networks, directly importing such properties into an emulation has been a challenge. Similarly, while there exist numerous models for creating realistic network topologies, the lack of addresses on these generated topologies has been a barrier to using them in emulators. Once an experimenter obtains a suitable topology, that topology must be mapped onto the physical resources of the testbed so that it can be instantiated. A number of restrictions make this an interesting problem: testbeds typically have heterogeneous hardware, scarce resources which must be conserved, and bottlenecks that must not be overused. User requests for particular types of nodes or links must also be met. In light of these constraints, the network testbed mapping problem is NP-hard. Though the complexity of the problem increases rapidly with the size of the experimenter's topology and the size of the physical network, the runtime of the mapper must not; long mapping times can hinder the usability of the testbed. This dissertation makes three contributions towards improving realism and scale in emulation testbeds. First, it meets the need for realistic network conditions by creating Flexlab, a hybrid environment that couples an emulation testbed with a live-network testbed, inheriting strengths from each. Second, it attends to the need for realistic topologies by presenting a set of algorithms for automatically annotating generated topologies with realistic IP addresses. Third, it presents a mapper, assign, that is capable of assigning experimenters' requested topologies to testbeds' physical resources in a manner that scales well enough to handle large environments

Controlo de congestionamento em redes sem fios

Doutoramento em Engenharia ElectrotécnicaCongestion control in wireless networks is an important and open issue. Previous research has proven the poor performance of the Transport Control Protocol (TCP) in such networks. The factors that contribute to the poor performance of TCP in wireless environments concern its unsuitability to identify/detect and react properly to network events, its TCP window based ow control algorithm that is not suitable for the wireless channel, and the congestion collapse due to mobility. New rate based mechanisms have been proposed to mitigate TCP performance in wired and wireless networks. However, these mechanisms also present poor performance, as they lack of suitable bandwidth estimation techniques for multi-hop wireless networks. It is thus important to improve congestion control performance in wireless networks, incorporating components that are suitable for wireless environments. A congestion control scheme which provides an e - cient and fair sharing of the underlying network capacity and available bandwidth among multiple competing applications is crucial to the definition of new e cient and fair congestion control schemes on wireless multi-hop networks. The Thesis is divided in three parts. First, we present a performance evaluation study of several congestion control protocols against TCP, in wireless mesh and ad-hoc networks. The obtained results show that rate based congestion control protocols need an eficient and accurate underlying available bandwidth estimation technique. The second part of the Thesis presents a new link capacity and available bandwidth estimation mechanism denoted as rt-Winf (real time wireless inference). The estimation is performed in real-time and without the need to intrusively inject packets in the network. Simulation results show that rt-Winf obtains the available bandwidth and capacity estimation with accuracy and without introducing overhead trafic in the network. The third part of the Thesis proposes the development of new congestion control mechanisms to address the congestion control problems of wireless networks. These congestion control mechanisms use cross layer information, obtained by rt-Winf, to accurately and eficiently estimate the available bandwidth and the path capacity over a wireless network path. Evaluation of these new proposed mechanisms, through ns-2 simulations, shows that the cooperation between rt-Winf and the congestion control algorithms is able to significantly increase congestion control eficiency and network performance.O controlo de congestionamento continua a ser extremamente importante quando se investiga o desempenho das redes sem fios. Trabalhos anteriores mostram o mau desempenho do Transport Control Proto- col (TCP) em redes sem fios. Os fatores que contribuem para um pior desempenho do TCP nesse tipo de redes s~ao: a sua falta de capacidade para identificar/detetar e reagir adequadamente a eventos da rede; a utilização de um algoritmo de controlo de uxo que não é adequado para o canal sem fios; e o colapso de congestionamento devido á mobilidade. Para colmatar este problemas foram propostos novos mecanismos de controlo de congestionamento baseados na taxa de transmissão. No entanto, estes mecanismos também apresentam um pior desempenho em redes sem fios, já que não utilizam mecanismos adequados para a avaliação da largura de banda disponível. Assim, é importante para melhorar o desempenho do controlo de congestionamento em redes sem fios, incluir componentes que são adequados para esse tipo de ambientes. Um esquema de controlo de congestionamento que permita uma partilha eficiente e justa da capacidade da rede e da largura de banda disponível entre múltiplas aplicações concorrentes é crucial para a definição de novos, eficientes e justos mecanismos de controlo congestionamento para as redes sem fios. A Tese está dividida em três partes. Primeiro, apresentamos um estudo sobre a avaliação de desempenho de vários protocolos de controlo de congestionamento relativamente ao TCP, em redes sem fios em malha e ad-hoc. Os resultados obtidos mostram que os protocolos baseados na taxa de transmissão precisam de uma técnica de avaliação da largura de banda disponível que seja eficiente e precisa . A segunda parte da Tese apresenta um novo mecanismo de avaliação da capacidade da ligação e da largura de banda disponível, designada por rt-Winf (real time wireless inference). A avaliação é realizada em tempo real e sem a necessidade de inserir tráfego na rede. Os resultados obtidos através de simulação e emulação mostram que o rt-Winf obtém com precisão a largura de banda disponível e a capacidade da ligação sem sobrecarregar a rede. A terceira parte da Tese propõe novos mecanismos de controlo de congestionamento em redes sem fios. Estes mecanismos de controlo de congestionamento apresentam um conjunto de caracter ísticas novas para melhorar o seu desempenho, de entre as quais se destaca a utilização da informação de largura de banda disponível obtida pelo rt-Winf. Os resultados da avaliação destes mecanismos, utilizando o simulador ns-2, permitem concluir que a cooperação entre o rt-Winf e os algoritmos de controlo de congestionamento aumenta significativamente o desempenho da rede