Optimization of p-cycle protection schemes in optical networks

La survie des réseaux est un domaine d'étude technique très intéressant ainsi qu'une préoccupation critique dans la conception des réseaux. Compte tenu du fait que de plus en plus de données sont transportées à travers des réseaux de communication, une simple panne peut interrompre des millions d'utilisateurs et engendrer des millions de dollars de pertes de revenu. Les techniques de protection des réseaux consistent à fournir une capacité supplémentaire dans un réseau et à réacheminer les flux automatiquement autour de la panne en utilisant cette disponibilité de capacité. Cette thèse porte sur la conception de réseaux optiques intégrant des techniques de survie qui utilisent des schémas de protection basés sur les p-cycles. Plus précisément, les p-cycles de protection par chemin sont exploités dans le contexte de pannes sur les liens. Notre étude se concentre sur la mise en place de structures de protection par p-cycles, et ce, en supposant que les chemins d'opération pour l'ensemble des requêtes sont définis a priori. La majorité des travaux existants utilisent des heuristiques ou des méthodes de résolution ayant de la difficulté à résoudre des instances de grande taille. L'objectif de cette thèse est double. D'une part, nous proposons des modèles et des méthodes de résolution capables d'aborder des problèmes de plus grande taille que ceux déjà présentés dans la littérature. D'autre part, grâce aux nouveaux algorithmes, nous sommes en mesure de produire des solutions optimales ou quasi-optimales. Pour ce faire, nous nous appuyons sur la technique de génération de colonnes, celle-ci étant adéquate pour résoudre des problèmes de programmation linéaire de grande taille. Dans ce projet, la génération de colonnes est utilisée comme une façon intelligente d'énumérer implicitement des cycles prometteurs. Nous proposons d'abord des formulations pour le problème maître et le problème auxiliaire ainsi qu'un premier algorithme de génération de colonnes pour la conception de réseaux protegées par des p-cycles de la protection par chemin. L'algorithme obtient de meilleures solutions, dans un temps raisonnable, que celles obtenues par les méthodes existantes. Par la suite, une formulation plus compacte est proposée pour le problème auxiliaire. De plus, nous présentons une nouvelle méthode de décomposition hiérarchique qui apporte une grande amélioration de l'efficacité globale de l'algorithme. En ce qui concerne les solutions en nombres entiers, nous proposons deux méthodes heurisiques qui arrivent à trouver des bonnes solutions. Nous nous attardons aussi à une comparaison systématique entre les p-cycles et les schémas classiques de protection partagée. Nous effectuons donc une comparaison précise en utilisant des formulations unifiées et basées sur la génération de colonnes pour obtenir des résultats de bonne qualité. Par la suite, nous évaluons empiriquement les versions orientée et non-orientée des p-cycles pour la protection par lien ainsi que pour la protection par chemin, dans des scénarios de trafic asymétrique. Nous montrons quel est le coût de protection additionnel engendré lorsque des systèmes bidirectionnels sont employés dans de tels scénarios. Finalement, nous étudions une formulation de génération de colonnes pour la conception de réseaux avec des p-cycles en présence d'exigences de disponibilité et nous obtenons des premières bornes inférieures pour ce problème.

Vers une intégration écologique des technologies de l’information et de la communication en éducation en Afrique du Centre et de l’Ouest : une approche culturelle

Dans un monde de plus en plus interconnecté où le développement nécessite une participation active à la société de l’information, où les différentes cultures rentrent davantage en contact entre elles et où les biens culturels sont devenus des biens de consommation, les minorités culturelles mondiales intégrant les technologies de l’information et de la communication (TIC) se retrouvent marginalisées face à la menace d’hégémonie culturelle des réseaux de l’information par les cultures dominantes de certains pays développés. Pour qu’une culture prenne sa place dans la société de l’information, il revient en premier lieu à ses institutions éducatives de former leurs apprenants dans un contexte culturel qui leur est propre et de valoriser et d’encourager la production et l’utilisation de contenu endogène. C’est dans le cadre de cette problématique que la présente recherche s’est donnée comme premier objectif de faire le bilan du contenu culturel accédé et diffusé par les TIC dans des écoles de pays africains dits en développement ; pour ensuite, comme deuxième objectif, de décrire les barrières à une intégration des TIC qui favoriserait la promotion culturelle en ligne dans ces écoles ; et finalement, comme troisième objectif, d’identifier des stratégies pragmatiques favorisant une intégration écologique des TIC dans ces écoles, c’est-à-dire, une intégration durable, adaptée au contexte local et favorisant la pleine participation des enseignants et des élèves. Pour y parvenir, nous avons adopté une approche méthodologique essentiellement descriptive et qualitative. Nous avons réalisé des entrevues avec 168 enseignants et 230 élèves de 34 écoles pionnières TIC situées dans cinq pays d’Afrique de l’Ouest et du Centre, que nous avons traitées selon une analyse de contenu spécifique à chaque objectif. L’adoption des stratégies décrites dans nos résultats permettrait aux écoles étudiées de surmonter, en partie, la multitude de barrières auxquelles elles font face et de favoriser l’intégration écologique des TIC. Une telle intégration est nécessaire à l’atteinte d’une société de l’information plus équitable et à l’éventuelle réduction du fossé numérique séparant les « info-riches » des « info-pauvres ».

Evolving Distributed Algorithms with Genetic Programming

Distributed systems are one of the most vital components of the economy. The most prominent example is probably the internet, a constituent element of our knowledge society. During the recent years, the number of novel network types has steadily increased. Amongst others, sensor networks, distributed systems composed of tiny computational devices with scarce resources, have emerged. The further development and heterogeneous connection of such systems imposes new requirements on the software development process. Mobile and wireless networks, for instance, have to organize themselves autonomously and must be able to react to changes in the environment and to failing nodes alike. Researching new approaches for the design of distributed algorithms may lead to methods with which these requirements can be met efficiently. In this thesis, one such method is developed, tested, and discussed in respect of its practical utility. Our new design approach for distributed algorithms is based on Genetic Programming, a member of the family of evolutionary algorithms. Evolutionary algorithms are metaheuristic optimization methods which copy principles from natural evolution. They use a population of solution candidates which they try to refine step by step in order to attain optimal values for predefined objective functions. The synthesis of an algorithm with our approach starts with an analysis step in which the wanted global behavior of the distributed system is specified. From this specification, objective functions are derived which steer a Genetic Programming process where the solution candidates are distributed programs. The objective functions rate how close these programs approximate the goal behavior in multiple randomized network simulations. The evolutionary process step by step selects the most promising solution candidates and modifies and combines them with mutation and crossover operators. This way, a description of the global behavior of a distributed system is translated automatically to programs which, if executed locally on the nodes of the system, exhibit this behavior. In our work, we test six different ways for representing distributed programs, comprising adaptations and extensions of well-known Genetic Programming methods (SGP, eSGP, and LGP), one bio-inspired approach (Fraglets), and two new program representations called Rule-based Genetic Programming (RBGP, eRBGP) designed by us. We breed programs in these representations for three well-known example problems in distributed systems: election algorithms, the distributed mutual exclusion at a critical section, and the distributed computation of the greatest common divisor of a set of numbers. Synthesizing distributed programs the evolutionary way does not necessarily lead to the envisaged results. In a detailed analysis, we discuss the problematic features which make this form of Genetic Programming particularly hard. The two Rule-based Genetic Programming approaches have been developed especially in order to mitigate these difficulties. In our experiments, at least one of them (eRBGP) turned out to be a very efficient approach and in most cases, was superior to the other representations.

An improved method for discovering link criticality in transport networks

Quantitatively assessing the importance or criticality of each link in a network is of practical value to operators, as that can help them to increase the network's resilience, provide more efficient services, or improve some other aspect of the service. Betweenness is a graph-theoretical measure of centrality that can be applied to communication networks to evaluate link importance. However, as we illustrate in this paper, the basic definition of betweenness centrality produces inaccurate estimations as it does not take into account some aspects relevant to networking, such as the heterogeneity in link capacity or the difference between node-pairs in their contribution to the total traffic. A new algorithm for discovering link centrality in transport networks is proposed in this paper. It requires only static or semi-static network and topology attributes, and yet produces estimations of good accuracy, as verified through extensive simulations. Its potential value is demonstrated by an example application. In the example, the simple shortest-path routing algorithm is improved in such a way that it outperforms other more advanced algorithms in terms of blocking ratio

Competing edge networks

We introduce a model for a pair of nonlinear evolving networks, defined over a common set of vertices, sub ject to edgewise competition. Each network may grow new edges spontaneously or through triad closure. Both networks inhibit the other’s growth and encourage the other’s demise. These nonlinear stochastic competition equations yield to a mean field analysis resulting in a nonlinear deterministic system. There may be multiple equilibria; and bifurcations of different types are shown to occur within a reduced parameter space. This situation models competitive peer-to-peer communication networks such as BlackBerry Messenger displacing SMS; or instant messaging displacing emails.

Building networks to work: an ethnographic study of informal routes into the UK construction industry and pathways for migrant up-skilling

The UK construction industry labour market is characterised by high levels of self-employment, sub-contracting, informality and flexibility. A corollary of this, and a sign of the increasing globalisation of construction, has been an increasing reliance on migrant labour, particularly that from the Eastern European Accession states. Yet, little is known about how their experiences within and outside of work shape their work in the construction sector. In this context better qualitative understandings of the social and communication networks through which migrant workers gain employment, create routes through the sector and develop their role/career are needed. We draw on two examples from a short-term ethnographic study of migrant construction worker employment experiences and practices in the town of Crewe in Cheshire, UK, to demonstrate how informal networks intersect with formal elements of the sector to facilitate both recruitment and up-skilling. Such research knowledge, we argue, offers new evidence of the importance of attending to migrant worker’s own experiences in the development of more transparent recruitment processes.

Modelo de gestão de risco em segurança da informação: um estudo de caso no mercado brasileiro de cartões de crédito

As questões ligadas a gestão de riscos associados a segurança da informação já é uma realidade no cenário empresarial brasileiro. O crescimento das operações de negócios em direção aos sistemas de informação baseados em tecnologia fez com que os números de ameaças e de vulnerabilidades sobre as redes de computadores e comunicações aumentassem. Vários são os desafios de estruturação e implementação de uma área de segurança da informação dentro das empresas. Este trabalho analisa as diversas formas de construção de uma infra-estrutura de gestão de risco em segurança de informação, não só no âmbito tecnológico, mas também, no operacional e no mercadológico, de forma a estabelecer uma relação transparente às demais áreas internas da organização, aos clientes e a todo o mercado. A segurança da informação, vista freqüentemente como um assunto ligado a tecnologia, passa a ser entendida cada vez mais como um processo de negócio, e conseqüentemente, uma grande vantagem competitiva para o mundo empresarial.

Proposta de integração das redes de comunicação da COSERN como uma solução de contigêncvia em caso de falhas nos enlaces do backbone de automação

T'his dissertation proposes alternative models to allow the interconnectioin of the data communication networks of COSERN Companhia Energética do Rio Grande do Norte. These networks comprise the oorporative data network, based on TCP/IP architecture, and the automation system linking remote electric energy distribution substations to the main Operatin Centre, based on digital radio links and using the IEC 60870-5-101 protoco1s. The envisaged interconnection aims to provide automation data originated from substations with a contingent route to the Operation Center, in moments of failure or maintenance of the digital radio links. Among the presented models, the one chosen for development consists of a computational prototype based on a standard personal computer, working under LINUX operational system and running na application, developesd in C language, wich functions as a Gateway between the protocols of the TCP/IP stack and the IEC 60870-5-101 suite. So, it is described this model analysis, implementation and tests of functionality and performance. During the test phase it was basically verified the delay introduced by the TCP/IP network when transporting automation data, in order to guarantee that it was cionsistent with the time periods present on the automation network. Besides , additional modules are suggested to the prototype, in order to handle other issues such as security and prioriz\ation of the automation system data, whenever they are travesing the TCP/IP network. Finally, a study hás been done aiming to integrate, in more complete way, the two considered networks. It uses IP platform as a solution of convergence to the communication subsystem of na unified network, as the most recente market tendencies for supervisory and other automation systems indicate

Supervisory software development according to IEEE 1451.1 standard

IEEE 1451 is Standard to connect transduscers through a communication network. This article describes a supervisory system implementaion according to IEEE 1451 Standard using Java. This software, named NCAP, may be used in several industrial applications, besides making feasible to obtain TEDS as a report or by Internet. NCAP communicates with transduscer module through RS232 Interface and was testes in industrial automation processes. © 2009 IEEE.

Simulation in NS-2 of DNP3 protocol encapsulated over TCP/IP in smart grid applications

In dealing with computer networks, these allow the flow of information through the resources of various equipment's. This work describes the implementation through the encapsulation of Protocol DNP3, usually employed in Smart Grid communication, in a simulator of discrete events. The NS-2 is a simulator in open source of network events, that facilitate the development of communication networks scenarios considering the protocols involved, in wireless or wired technologies. The objective of this work is to develop the DNP3 protocol encapsulation over a TCP/IP in the in the discrete event Simulator NS-2, allowing an analysis of behavior of a middle or large network sized in Smart Grid applications. © 2013 IEEE.

Monitoramento de hosts em redes tcp/ip sobre base georreferenciada com métricas de qualidade

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Análise de desempenho de redes de comunicação wireless em aplicações de Smart Grid

Pós-graduação em Engenharia Elétrica - FEIS

Simulation of visible light communications in vehicular networks

The rapid development in the field of lighting and illumination allows low energy consumption and a rapid growth in the use, and development of solid-state sources. As the efficiency of these devices increases and their cost decreases there are predictions that they will become the dominant source for general illumination in the short term. The objective of this thesis is to study, through extensive simulations in realistic scenarios, the feasibility and exploitation of visible light communication (VLC) for vehicular ad hoc networks (VANETs) applications. A brief introduction will introduce the new scenario of smart cities in which visible light communication will become a fundamental enabling technology for the future communication systems. Specifically, this thesis focus on the acquisition of several, frequent, and small data packets from vehicles, exploited as sensors of the environment. The use of vehicles as sensors is a new paradigm to enable an efficient environment monitoring and an improved traffic management. In most cases, the sensed information must be collected at a remote control centre and one of the most challenging aspects is the uplink acquisition of data from vehicles. My thesis discusses the opportunity to take advantage of short range vehicle-to-vehicle (V2V) and vehicle-to-roadside (V2R) communications to offload the cellular networks. More specifically, it discusses the system design and assesses the obtainable cellular resource saving, by considering the impact of the percentage of vehicles equipped with short range communication devices, of the number of deployed road side units, and of the adopted routing protocol. When short range communications are concerned, WAVE/IEEE 802.11p is considered as standard for VANETs. Its use together with VLC will be considered in urban vehicular scenarios to let vehicles communicate without involving the cellular network. The study is conducted by simulation, considering both a simulation platform (SHINE, simulation platform for heterogeneous interworking networks) developed within the Wireless communication Laboratory (Wilab) of the University of Bologna and CNR, and network simulator (NS3). trying to realistically represent all the wireless network communication aspects. Specifically, simulation of vehicular system was performed and introduced in ns-3, creating a new module for the simulator. This module will help to study VLC applications in VANETs. Final observations would enhance and encourage potential research in the area and optimize performance of VLC systems applications in the future.

Mac protocols for linear wireless (sensor) networks

Wireless sensor networks (WSNs) consist of a large number of sensor nodes, characterized by low power constraint, limited transmission range and limited computational capabilities [1][2].The cost of these devices is constantly decreasing, making it possible to use a large number of sensor devices in a wide array of commercial, environmental, military, and healthcare fields. Some of these applications involve placing the sensors evenly spaced on a straight line for example in roads, bridges, tunnels, water catchments and water pipelines, city drainages, oil and gas pipelines etc., making a special class of these networks which we define as a Linear Wireless Network (LWN). In LWNs, data transmission happens hop by hop from the source to the destination, through a route composed of multiple relays. The peculiarity of the topology of LWNs, motivates the design of specialized protocols, taking advantage of the linearity of such networks, in order to increase reliability, communication efficiency, energy savings, network lifetime and to minimize the end-to-end delay [3]. In this thesis a novel contention based Medium Access Control (MAC) protocol called L-CSMA, specifically devised for LWNs is presented. The basic idea of L-CSMA is to assign different priorities to nodes based on their position along the line. The priority is assigned in terms of sensing duration, whereby nodes closer to the destination are assigned shorter sensing time compared to the rest of the nodes and hence higher priority. This mechanism speeds up the transmission of packets which are already in the path, making transmission flow more efficient. Using NS-3 simulator, the performance of L-CSMA in terms of packets success rate, that is, the percentage of packets that reach destination, and throughput are compared with that of IEEE 802.15.4 MAC protocol, de-facto standard for wireless sensor networks. In general, L-CSMA outperforms the IEEE 802.15.4 MAC protocol.

Adapting health-risk communication to the specific cultural contexts of diverse populations : an assessment of malaria-treatment programs in Liberia

Drawing on theories of technical communication, rhetoric, literacy, language and culture, and medical anthropology, this dissertation explores how local culture and traditions can be incorporated into health-risk-communication-program design and implementation, including the design and dissemination of health-risk messages. In a modern world with increasing global economic partnerships, mounting health and environmental risks, and cross-cultural collaborations, those who interact with people of different cultures have “a moral obligation to take those cultures seriously, including their social organization and values” (Hahn and Inhorn 10). Paradoxically, at the same time as we must carefully adapt health, safety, and environmental-risk messages to diverse cultures and populations, we must also recognize the increasing extent to which we are all becoming part of one, vast, interrelated global village. This, too, has a significant impact on the ways in which healthcare plans should be designed, communicated, and implemented. Because communicating across diverse cultures requires a system for “bridging the gap between individual differences and negotiating individual realities” (Kim and Gudykunst 50), both administrators and beneficiaries of malaria-treatment-and-control programs (MTCPs) in Liberia were targeted to participate in this study. A total of 105 people participated in this study: 21 MTCP administrators (including designers and implementers) completed survey questionnaires on program design, implementation, and outcomes; and 84 MTCP beneficiaries (e.g., traditional leaders and young adults) were interviewed about their knowledge of malaria and methods for communicating health risks in their tribe or culture. All participants showed a tremendous sense of courage, commitment, resilience, and pragmatism, especially in light of the fact that many of them live and work under dire socioeconomic conditions (e.g., no electricity and poor communication networks). Although many MTCP beneficiaries interviewed for this study had bed nets in their homes, a majority (46.34 percent) used a combination of traditional herbal medicine and Western medicine to treat malaria. MTCP administrators who participated in this study rated the impacts of their programs on reducing malaria in Liberia as moderately successful (61.90 percent) or greatly successful (38.10 percent), and they offered a variety of insights on what they might do differently in the future to incorporate local culture and traditions into program design and implementation. Participating MTCP administrators and beneficiaries differed in their understanding of what “cultural incorporation” meant, but they agreed that using local indigenous languages to communicate health-risk messages was essential for effective health-risk communication. They also suggested that understanding the literacy practices and linguistic cultures of the local people is essential to communicating health risks across diverse cultures and populations.