On Measuring the Geographic Diversity of Internet Routes

Route diversity in networks is elemental for establishing reliable, high-capacity connections with appropriate security between endpoints. As for the Internet, route diversity has already been studied at both Autonomous System- and router-level topologies by means of graph theoretical disjoint paths. In this paper we complement these approaches by proposing a method for measuring the diversity of Internet paths in a geographical sense. By leveraging the recent developments in IP geolocation we show how to map the paths discovered by traceroute into geographically equivalent classes. This allows us to identify the geographical footprints of the major transmission paths between end-hosts, and building on our observations, we propose a quantitative measure for geographical diversity of Internet routes between any two hosts

Alocação de recursos com máxima conectividade em redes com topologia arbitrária

Orientador: Prof. Dr. Elias P. Duarte Jr.Coorientador: Prof. Dr. Jaime CohenDissertação (mestrado) - Universidade Federal do Paraná, Setor de Ciências Exatas, Programa de Pós-Graduação em Informática. Defesa : Curitiba, 27/08/2018Inclui referências: p.33-35Área de concentração: Ciência da ComputaçãoResumo: O posicionamento de recursos em redes é um problema que encontra diversas variantes, desde o posicionamento de servidores na arquitetura tradicional cliente-servidor, passando pelo posicionamento de controladores em redes SDN, ou caches em redes CDN, entre vários outros. Este trabalho apresenta o problema de posicionar o número mínimo de recursos de modo a maximizar o número de caminhos vértice-disjuntos entre um recurso e seus clientes. Uma das contribuições do trabalho é a prova de que o problema de encontrar o número mínimo de recursos sob essas condições é NP-completo. Uma solução exata para o problema foi implementada e sua execução se mostrou viável em diversas redes de topologia arbitrária. Apresentamos os resultados comparando-os com o problema clássico da p-mediana em que é minimizada a soma das distâncias entre os clientes e seus recursos. Resultados experimentais usando redes de The Internet Topology Zoo avaliam o ganho de conectividade e o aumento da soma das distâncias quando a solução proposta é aplicada. Palavras-chave: Alocamento de Recursos, vértice-conectividade, localização de origens, pmediana.Abstract: Resource placement is a problem that has several variants in computer networks, from server placement in the traditional client-server architecture to the allocation of controllers in SDN networks, or caches in CDN networks, among many others. This work presents the problem of placing the minimum number of resources in order to maximize the number of vertex-disjoint paths between a resource and its clients. One of the contributions of this work is the proof that the problem of finding the minimum number of resources under these conditions is NP-complete. An exact solution to this problem was implemented and experiments showed its feasibility for several arbitrary topology networks. This work presents a comparison between the connectivity based resource location problem with the classical p-median problem in which the sum of the distances between clients and their resources is minimized. Experimental results using networks from The Internet Topology Zoo show both the connectivity gains and the impact on the sum of the distances when the proposed solution is applied to real Internet-based networks. Keywords: Resource Allocation, vertex-connectivity, source location, p-median

Avaliação de estabilidade de transmissões de vídeo por protocolo de transporte multicaminho

Orientador : Prof. Dr. Eduardo Parente RibeiroCoorientador : Prof. Dr. Carlos Marcelo PedrosoDissertação (mestrado) - Universidade Federal do Paraná, Setor de Tecnologia, Programa de Pós-Graduação em Engenharia Elétrica. Defesa: Curitiba, 23/02/2017Inclui referências : p. 70-75Resumo: A evoluc¸a˜ o tecnolo' gica de dispositivos mo' veis e o aumento da disponibilidade de redes IP, criam novas oportunidades para distribuic¸a˜ o de conteu' do multimedia pela Internet. Atualmente os usua' rios teˆ m a possibilidade de acessar filmes, pec¸as de teatros, concertos de mu' sica transmitidos ao vivo ou armazenados sob-demanda. Aplicac¸o˜ es de tempo-real requerem alta qualidade de servic¸o, na˜ o sendo tolerantes a variac¸o˜ es do atraso me' dio por exemplo. Neste contexto, o delay-centric foi proposto para realizar handover entre redes mo' veis no protocolo SCTP. Sua proposta de realizar a troca de caminho utilizando o valor do atraso me' dio suavi- zado mostrou uma melhora significativa quando utilizado em aplicac¸o˜ es de tempo-real. Va' rios autores tem estudado a utilizac¸a˜ o do SCTP padra˜ o, do CMT e do CMT-PF em transmisso˜ es de v'?deo de tempo real. Este trabalho se propoˆ s a estudar a estabilidade de transmisso˜ es de v'?deo HD com diferentes caracter'?sticas de GOP, por protocolos de transporte multicaminho. Simulac¸o˜ es foram realizadas com trac¸ados de v'?deo de caracter'?sticas distintas e foram anali- sados, para fins de comparac¸a˜ o, o comportamento do delay-centric com diferentes histereses, SCTP padra˜ o, CMT e do CMT-PF. Foram utilizados cena' rios com va' rios n'?veis de diversidade e observadas me' tricas de atraso me' dio, Goodput, justic¸a na divisa˜ o do throughput e trhoughput me' dio nas interfaces dos agentes que enviavam e recebiam o v'?deo. Nos cena' rios com dois e treˆ s caminhos completamente disjuntos, os resultados obtidos confirmaram os dados conti- dos na literatura onde o delay-centric, independente da histerese, teve desempenho igual ou superior do CMT e ao CMT-PF. O SCTP Padra˜ o na˜ o se beneficiou da existeˆ ncia de mu' ltiplos caminhos, obtendo o pior desempenho dentre todos os protocolos estudados nos cena' rios com dois e treˆ s caminhos completamente disjuntos. Entretanto, no cena' rio com treˆ s no' s de acesso interligados a dois cores, com duas redes de acesso compartilhando um core, os resul- tados indicaram que o delay-centric sem histerese obteve o melhor desempenho dentre todos os protocolos estudados e o SCTP Padra˜ o mostrou melhor desempenho que o CMT, CMT-PF e delay-centric com histerese de 10ms, 20ms e 30ms. Palavras-chave: SCTP. Delay-centric. Multihoming.Abstract: The mobile devices technological evolution and the increased availability of IP networks, create new opportunities for multimedia content distribution over Internet. Nowadays, users have ac- cess to movies, plays or music concerts live over demand via video streaming over the Internet. Real-time applications require high quality service and are not tolerant to delay variations. The delay-centric was initially proposed to make the handover between mobile networks in SCTP by using the smoothed round trip time and delivering a higher user experience on real-time appli- cations. Other authors have studied the use of CMT and CMT-PF in real-time video streaming. The main objective of this work is to study the stability of HD video streaming, with different GOP characteristics, using multipath transport protocols. Video traces were used in the simu- lations with various path configurations to compare the behavior of delay-centric with different hysteresis, standard SCTP, CMT and CMT-PF. Results were analyzed using the metrics of de- lay, jitter, Goodput, mean throughput and throughput division justice. In scenarios with two or tree disjoint paths, the results confirmed the previous results on the literature that the delay- centric, independent of hysteresis level, have same or better performance when compared to CMT and CMT-PF. The standard SCTP do not take advantage of the multiple disjoint paths, having the worst performance when compared to the other protocols. In scenarios with tree access nodes connected to two cores, with two access networks sharing the same core, the results showed that the delay-centric with no hysteresis 5have the best performance in compa- rison to the other protocols, followed by the standard SCTP that presented better performance than CMT, CMT-PF and delay-centric with 10ms, 20ms, 30ms of hysteresis respectively. Key words: SCTP. Delay-centric. Multihoming

WS-mediator for improving dependability of service composition

Web Services and service-oriented architectures (SOAs) represent a new paradigm for building distributed computing applications. In recent years, they have started to play a critical role in numerous e-Science and e-Commerce applications. The advantages of Web Services, such as their loosely coupled architecture and standardized interoperability, make them a desirable platform, especially for developing large-scale applications such as those based on cross-organizational service composition. However, the Web Service technology is now facing many serious issues that need to be addressed, one of the most important ones being the dependability of their composition. Web Service composition relies on individual component services and computer networks, particularly the Internet. As the component services are autonomous, prior to use their dependability is unknown. In addition to that, computer networks are inherently unreliable media: from the user's perspective, network failures may undermine the dependability of Web Services. Consequently, failures of individual component services and of the network can undermine the dependability of the entire application relying on service composition. Our research is intended to contribute to achieving higher dependability of Web Service composition. We have developed a novel solution, called WS-Mediator system, implementing resilience-explicit computing and fault tolerance mechanisms to improve the dependability of Web Service composition. It consists of a number of subsystems, called Sub-Mediators, which are deployed at various geographical locations across the Internet to monitor Web Services and dynamically generate Web Service dependability metadata in order to make resilience-explicit decisions. In addition to applying the fault tolerance mechanisms that deal with various kinds of faults during the service composition, the resilience-explicit reconfiguration mechanism dynamically selects the most dependable Web Services to achieve higher service composition dependability fault tolerance. A specific instance of the WS-Mediator architecture has been developed in the Java Web Service technology. A series of experiments with real-world Web Services, in particular in the bioinformatics domain, have been carried out using the Java WS- Mediator. The results of the experiments have demonstrated the applicability of the WS-Mediator approach.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Managed access dependability for critical services in wireless inter domain environment

The Information and Communications Technology (ICT) industry has through the last decades changed and still continues to affect the way people interact with each other and how they access and share information, services and applications in a global market characterized by constant change and evolution. For a networked and highly dynamic society, with consumers and market actors providing infrastructure, networks, services and applications, the mutual dependencies of failure free operations are getting more and more complex. Service Level Agreements (SLAs) between the various actors and users may be used to describe the offerings along with price schemes and promises regarding the delivered quality. However, there is no guarantee for failure free operations whatever efforts and means deployed. A system fails for a number of reasons, but automatic fault handling mechanisms and operational procedures may be used to decrease the probability for service interruptions. The global number of mobile broadband Internet subscriptions surpassed the number of broadband subscriptions over fixed technologies in 2010. The User Equipment (UE) has become a powerful device supporting a number of wireless access technologies and the always best connected opportunities have become a reality. Some services, e.g. health care, smart power grid control, surveillance/monitoring etc. called critical services in this thesis, put high requirements on service dependability. A definition of dependability is the ability to deliver services that can justifiably be trusted. For critical services, the access networks become crucial factors for achieving high dependability. A major challenge in a multi operator, multi technology wireless environment is the mobility of the user that necessitates handovers according to the physical movement. In this thesis it is proposed an approach for how to optimize the dependability for critical services in multi operator, multi technology wireless environment. This approach allows predicting the service availability and continuity at real-time. Predictions of the optimal service availability and continuity are considered crucial for critical services. To increase the dependability for critical services dual homing is proposed where the use of combinations of access points, possibly owned by different operators and using different technologies, are optimized for the specific location and movement of the user. A central part of the thesis is how to ensure the disjointedness of physical and logical resources so important for utilizing the dependability increase potential with dual homing. To address the interdependency issues between physical and logical resources, a study of Operations, Administrations, and Maintenance (OA&M) processes related to the access network of a commercial Global System for Mobile Communications (GSM)/Universal Mobile Telecommunications System (UMTS) operator was performed. The insight obtained by the study provided valuable information of the inter woven dependencies between different actors in the delivery chain of services. Based on the insight gained from the study of OA&M processes a technological neutral information model of physical and logical resources in the access networks is proposed. The model is used for service availability and continuity prediction and to unveil interdependencies between resources for the infrastructure. The model is proposed as an extension of the Media Independent Handover (MIH) framework. A field trial in a commercial network was conducted to verify the feasibility in retrieving the model related information from the operators' Operational Support Systems (OSSs) and to emulate the extension and usage of the MIH framework. In the thesis it is proposed how measurement reports from UE and signaling in networks are used to define virtual cells as part of the proposed extension of the MIH framework. Virtual cells are limited geographical areas where the radio conditions are homogeneous. Virtual cells have radio coverage from a number of access points. A Markovian model is proposed for prediction of the service continuity of a dual homed critical service, where both the infrastructure and radio links are considered. A dependability gain is obtained by choosing a global optimal sequence of access points. Great emphasizes have been on developing computational e cient techniques and near-optimal solutions considered important for being able to predict service continuity at real-time for critical services. The proposed techniques to obtain the global optimal sequence of access points may be used by handover and multi homing mechanisms/protocols for timely handover decisions and access point selections. With the proposed extension of the MIH framework a global optimal sequence of access points providing the highest reliability may be predicted at real-time

Algoritmos paralelos para árvores de cortes e medidas de centralidade em grafos

Resumo: Uma árvore de cortes é uma representação compacta da aresta-conectividade de um grafo não orientado. As árvores de cortes resolvem de maneira eficiente o problema de calcular a arestaconectividade entre todos os pares de vértices do grafo. As árvores de cortes têm muitas aplicações como, por exemplo, no projeto de redes confiáveis, na partição de grafos, no agrupamento em grafos, na análise de redes sociais, dentre outras. Dois algoritmos para a construção de árvores de cortes de grafos não orientados e capacitados são bem conhecidos: o algoritmo de Gomory-Hu e o algoritmo de Gusfield. Este trabalho apresenta propostas de implementações paralelas de três algoritmos para encontrar uma árvore de cortes. Versões paralelas para os algoritmos de Gusfield e de Gomory-Hu são descritas e avaliadas experimentalmente. Um algoritmo híbrido que combina esses dois algoritmos e que busca tirar proveito das vantagens de cada um deles também é apresentado. Resultados experimentais mostram que os três algoritmos apresentam boas acelerações nos tempos de execução. Os experimentos também mostram que o algoritmo híbrido é quase sempre mais rápido do que o algoritmo de Gomory-Hu e em certas instâncias ele é muito mais rápido do que o algoritmo de Gusfield. Heurísticas para a melhoria do algoritmo de Gomory-Hu e do algoritmo híbrido são propostas e analisadas. Na segunda parte desta tese, são estudadas medidas de centralidade dos vértices de um grafo que são baseadas na conectividade - algumas delas podem ser calculadas a partir de árvores de cortes. As medidas de centralidade de vértices têm como objetivo quantificar a importância dos vértices de um grafo com base em diferentes critérios. Dentre as medidas de centralidade propostas, destaca-se a i-aresta-conectividade, que mede a aresta-conectividade dos vértices em relação ao grafo. Uma medida de conectividade baseada em cortes de vértices também é proposta. Um estudo experimental com as medidas de conectividade foi executado para avaliar a relação das medidas propostas com outras medidas de centralidade mais conhecidas. Esse estudo mostra empiricamente que vértices com alta conectividade tendem a ter baixa excentricidade. Além disso, experimentos mostram que as medidas de conectividade não são equivalentes ao grau como critério de ordenação dos vértices