Allocation rules on networks

When allocating a resource, geographical and infrastructural constraints have to be taken into account. We study the problem of distributing a resource through a network from sources endowed with the resource to citizens with claims. A link between a source and an agent depicts the possibility of a transfer from the source to the agent. Given the supplies at each source, the claims of citizens, and the network, the question is how to allocate the available resources among the citizens. We consider a simple allocation problem that is free of network constraints, where the total amount can be freely distributed. The simple allocation problem is a claims problem where the total amount of claims is greater than what is available. We focus on consistent and resource monotonic rules in claims problems that satisfy equal treatment of equals. We call these rules fairness principles and we extend fairness principles to allocation rules on networks. We require that for each pair of citizens in the network, the extension is robust with respect to the fairness principle. We call this condition pairwise robustness with respect to the fairness principle. We provide an algorithm and show that each fairness principle has a unique extension which is pairwise robust with respect to the fairness principle. We give applications of the algorithm for three fairness principles: egalitarianism, proportionality and equal sacrifice.

Redes sociales en internet y Agenda Setting en el caso de María Camila Sánchez, víctima de acoso sexual en Transmilenio en Bogotá

Este artículo se propone analizar la manera en que se reubica la información de los medios en el contexto de los cambios tecnológicos y sociales que se han producido en el ámbito periodístico en Colombia, en general en Bogotá, en particular un caso específico de violencia contra la mujer; el caso escogido para el análisis es el de María Camila Sánchez, víctima de acoso sexual en Transmilenio en Julio de 2014, cuando se dirigía de regreso a su casa. Se espera proporcionar a partir del caso estudiado, nuevas miradas sobre el tema y aportar al conocimiento del periodismo sobre el fenómeno de intersección entre la información que se presenta en las redes sociales y que logra posicionarse en un lugar privilegiado en los medios de comunicación nacional. Facebook y Twitter son algunas las redes sociales en Internet que acaparan el interés de los colombianos como lo demuestra señala la más reciente “Encuesta de Calidad de Vida” del Departamento Administrativo Nacional de Estadística (DANE, 2014) de Colombia, que asegura que el 63,81 por ciento de los usuarios que accedieron a internet y redes sociales, lo hicieron desde cualquier lugar o dispositivo móvil y su aplicación móvil. En este contexto, el caso de María Camila permite analizar la vinculación actual de las redes sociales en la construcción de la agenda mediática, bajo la mirada de la teoría agenda setting, desarrollada por Maxwell McCombs.

Admission control schemes for TCP elastic traffic in class-based networks

En aquesta tesi proposem dos esquemes de xarxa amb control d'admissió per al trànsit elàstic TCP amb mecanismes senzills. Ambdós esquemes són capaços de proporcionar throughputs diferents i aïllament entre fluxos, on un "flux" es defineix com una seqüència de paquets relacionats dins d'una connexió TCP. Quant a l'arquitectura, ambdós fan servir classes de paquets amb diferents prioritats de descart, i un control d'admissió implícit, edge-to-edge i basat en mesures. En el primer esquema, les mesures són per flux, mentre que en el segon, les mesures són per agregat. El primer esquema aconsegueix un bon rendiment fent servir una modificació especial de les fonts TCP, mentre que el segon aconsegueix un bon rendiment amb fonts TCP estàndard. Ambdós esquemes han estat avaluats satisfactòriament a través de simulació en diferents topologies de xarxa i càrregues de trànsit.

Label space reduction in GMPLs and All-Optical Label Swapping networks

All-Optical Label Swapping (AOLS) es una tecnología clave para la implementación de nodos de conmutación completamente óptica de paquetes. Sin embargo, el costo de su desarrollo es proporcional al tamaño del espacio de etiquetas (label space). Debido a que los principios de funcionamiento de AOLS son casos particulares de los del MultiProtocol Label Switching (MPLS), esta tesis estudia métodos generales, aplicables a ambos, con el propósito de reducir el espacio de etiquetas tanto como sea posible. Modelos de programación lineal entera y heurísticas son propuestos para el caso en el que se permite apilar una etiqueta extra. Encontramos que cerca del 50% del espacio de etiquetas puede ser reducido, si se permite colocar una etiqueta extra en la pila. Además, particularmente para AOLS, encontramos que se puede reducir el espacio de etiquetas cerca al 25% si se duplica la capacidad de los enlaces y se permite re-encaminar el tráfico.

Multi-layer survivability: routing schemes for GMPLS-based networks

En les xarxes IP/MPLS sobre WDM on es transporta gran quantitat d'informacio, la capacitat de garantir que el trafic arriba al node de desti ha esdevingut un problema important, ja que la fallada d'un element de la xarxa pot resultar en una gran quantitat d'informacio perduda. Per garantir que el trafic afectat per una fallada arribi al node desti, s'han definit nous algoritmes d'encaminament que incorporen el coneixement de la proteccio en els dues capes: l'optica (WDM) i la basada en paquets (IP/MPLS). D'aquesta manera s'evita reservar recursos per protegir el trafic a les dues capes. Els nous algoritmes resulten en millor us dels recursos de la xarxa, ofereixen rapid temps de recuperacio, eviten la duplicacio de recursos i disminueixen el numero de conversions del trafic de senyal optica a electrica.

Enhanced fault recovery methods for protected traffic services in GMPLS networks

Les noves tecnologies a la xarxa ens permeten transportar, cada cop més, grans volums d' informació i trànsit de xarxa amb diferents nivells de prioritat. En aquest escenari, on s'ofereix una millor qualitat de servei, les conseqüències d'una fallada en un enllaç o en un node esdevenen més importants. Multiprotocol Lavel Switching (MPLS), juntament amb l'extensió a MPLS generalitzat (GMPLS), proporcionen mecanismes ràpids de recuperació de fallada establint camins, Label Switch Path (LSPs), redundants per ser utilitzats com a camins alternatius. En cas de fallada podrem utilitzar aquests camins per redireccionar el trànsit. El principal objectiu d'aquesta tesi ha estat millorar alguns dels actuals mecanismes de recuperació de fallades MPLS/GMPLS, amb l'objectiu de suportar els requeriments de protecció dels serveis proporcionats per la nova Internet. Per tal de fer aquesta avaluació s'han tingut en compte alguns paràmetres de qualitat de protecció com els temps de recuperació de fallada, les pèrdues de paquets o el consum de recursos. En aquesta tesi presentem una completa revisió i comparació dels principals mètodes de recuperació de fallada basats en MPLS. Aquest anàlisi inclou els mètodes de protecció del camí (backups globals, backups inversos i protecció 1+1), els mètodes de protecció locals i els mètodes de protecció de segments. També s'ha tingut en compte l'extensió d'aquests mecanismes a les xarxes òptiques mitjançant el pla de control proporcionat per GMPLS. En una primera fase d'aquest treball, cada mètode de recuperació de fallades és analitzat sense tenir en compte restriccions de recursos o de topologia. Aquest anàlisi ens dóna una primera classificació dels millors mecanismes de protecció en termes de pèrdues de paquets i temps de recuperació. Aquest primer anàlisi no és aplicable a xarxes reals. Per tal de tenir en compte aquest nou escenari, en una segona fase, s'analitzen els algorismes d'encaminament on sí tindrem en compte aquestes limitacions i restriccions de la xarxa. Es presenten alguns dels principals algorismes d'encaminament amb qualitat de servei i alguna de les principals propostes d'encaminament per xarxes MPLS. La majoria dels actual algorismes d'encaminament no tenen en compte l'establiment de rutes alternatives o utilitzen els mateixos objectius per seleccionar els camins de treball i els de protecció. Per millorar el nivell de protecció introduïm i formalitzem dos nous conceptes: la Probabilitat de fallada de la xarxa i l'Impacte de fallada. Un anàlisi de la xarxa a nivell físic proporciona un primer element per avaluar el nivell de protecció en termes de fiabilitat i disponibilitat de la xarxa. Formalitzem l'impacte d'una fallada, quant a la degradació de la qualitat de servei (en termes de retard i pèrdues de paquets). Expliquem la nostra proposta per reduir la probabilitat de fallada i l'impacte de fallada. Per últim fem una nova definició i classificació dels serveis de xarxa segons els valors requerits de probabilitat de fallada i impacte. Un dels aspectes que destaquem dels resultats d'aquesta tesi és que els mecanismes de protecció global del camí maximitzen la fiabilitat de la xarxa, mentre que les tècniques de protecció local o de segments de xarxa minimitzen l'impacte de fallada. Per tant podem assolir mínim impacte i màxima fiabilitat aplicant protecció local a tota la xarxa, però no és una proposta escalable en termes de consum de recursos. Nosaltres proposem un mecanisme intermig, aplicant protecció de segments combinat amb el nostre model d'avaluació de la probabilitat de fallada. Resumint, aquesta tesi presenta diversos mecanismes per l'anàlisi del nivell de protecció de la xarxa. Els resultats dels models i mecanismes proposats milloren la fiabilitat i minimitzen l'impacte d'una fallada en la xarxa.

Internet móvel em Portugal: variáveis de acesso, uso e consumo

A emergência de novas formas de acesso à internet vem reforçar a necessidade de desenvolvimento de iniciativas de I&D que facilitem a melhor compreensão dos processos de transformação associados à evolução tecnológica e aferir se de tais processos resultam novas consequências sociais ao nível das formas de uso e consumo de uma tecnologia e arranjos sociais associados. Este projecto pretende avaliar o papel e relevância das tecnologias móveis de acesso à internet, a importância da mobilidade e dos dispositivos móveis como instrumentos na promoção do envolvimento social, da interação e da expressão subjectiva. Na sequência da aplicação de metodologias qualitativas numa fase exploratória, através de entrevistas com os principais representantes da indústria das comunicações móveis e dos estudos de mercado, e de metodologias quantitativas com a aplicação de um questionário a uma amostra representativa da sociedade portuguesa, temos como objectivo desenvolvimento de um protótipo para uma aplicação móvel no contexto educativo do ensino superior, ligada ao apoio aos alunos e docentes e incluindo conteúdos escolares, institucionais e de envolvimento social. Esta aplicação vem corresponder às necessidades dos utilizadores de acordo com os resultados obtidos anteriormente. A análise do uso desta plataforma e consequências daí resultantes em termos de participação, usabilidade, actividades e potencial para produção de capital será realizada com base na análise de redes sociais (SNA). Através desta pretendemos observar e estudar as relações e os padrões de relacionamentos entre os utilizadores de internet móvel num contexto educativo.

Mobile Internet : perspectives from the Stakeholders

Mobile internet represents a major new trend in communication technologies use and consumption, but few evidence exists that confirms claims of novelty and social change in association with this technology use. This paper characterizes the use of mobile internet in a southern European country and associated patterns of use, focusing both on users’ profiles, forms of access, motivations to use and most popular activities undertaken via this technology, from a diffusion of innovations and social adoption of technologies perspectives, and tries to compare mobile it with fixed access to the internet in order to validate possible transformations that point to new social configurations. We seek to understand the way stakeholders perceive and characterize the European context of mobile internet. The depicted study involved a qualitative stage consisting of a set of interviews with mobile communications industry representatives and market research community in the country. These interviews were analysed in Nvivo, leading to the following eleven main categories that are explored throughout the paper: smartphones in Europe, mobile internet in Europe, users profiles, obstacles to the spread, forms of access, forms of use, motivations to use mobile internet, limitations of smartphones, apps, digital divide VS digital union and predictions for the future, as well as several subcategories forming a tree categorization. According to the data collected, mobile phones’ sales are decreasing in Europe and worldwide but on the other hand smartphones are having an exponential growth which leads to the democratization of internet access via mobile devices. As a consequence of this, it is believed that mobile internet access will soon exceed the fixed one. Mobile internet users are multiplatform, they exploit all the possibilities of mobility and they are spending less time on computers. The main obstacles to the spread of mobile internet are the high prices of price plans and there is still a lack of information and knowledge regarding the service. Mobile internet users are developing new online surfing behaviours based on apps and less in browsers and social networks represent a very high share of internet traffic through mobile phones. With mobility, “dead time” is turning into useful time and users are more likely to be available to try new services and analyze products. Innovative services concerning geolocation, consumerism, share and relationships are growing and it is necessary to highlight that mobile internet allows calling and texting, which can turn telecommunications companies into the role of Dump Pipes. This exploratory design raises questions in relation with mobile internet access and its social consequences, and provides interesting indicative research results relevant for future research in this area.

Biblioteca 2.0 : produção e organização do conhecimento na Internet

O objectivo principal deste trabalho de investigação é na análise do aproveitamento das potencialidades da tecnologia da Web 2.0 pelos profissionais de informação na gestão do conhecimento nas bibliotecas, especialmente nas universitárias, onde a utilização destas tecnologias se revela de extrema importância. Para enquadrar o estudo no âmbito da aplicação das tecnologias da Web 2.0 ao serviço da biblioteca foi analisado, em primeiro lugar, o impacto que o desenvolvimento tecnológico teve na sociedade e a globalização do saber originado pelo software social. Para complementar o estudo e verificar a gestão de uma das redes sociais, o Blogue, foi usado o método qualitativo, através da aplicação de uma grelha de avaliação da qualidade dos Blogues desenvolvida por Luísa Alvim. Os resultados obtidos da análise dos Blogues foram submetidos à observação dos princípios da Web 2.0, defendidos por Maness. Concluiu-se que as potencialidades do Blogue não são completamente exploradas pelos profissionais de informação, nem mesmo nas bibliotecas universitárias. Este estudo pretende fazer a análise da situação, mas também ser um ponto de partida para que os responsáveis das bibliotecas, especialmente das bibliotecas universitárias, repensem o conceito e mais-valia da Web 2.0, de forma a que o Blogue seja gerido estrategicamente em benefício do utilizador, profissionais de informação e do próprio serviço da biblioteca.

Effectiveness of landmark analysis for establishing locality in p2p networks

Locality to other nodes on a peer-to-peer overlay network can be established by means of a set of landmarks shared among the participating nodes. Each node independently collects a set of latency measures to landmark nodes, which are used as a multi-dimensional feature vector. Each peer node uses the feature vector to generate a unique scalar index which is correlated to its topological locality. A popular dimensionality reduction technique is the space filling Hilbert’s curve, as it possesses good locality preserving properties. However, there exists little comparison between Hilbert’s curve and other techniques for dimensionality reduction. This work carries out a quantitative analysis of their properties. Linear and non-linear techniques for scaling the landmark vectors to a single dimension are investigated. Hilbert’s curve, Sammon’s mapping and Principal Component Analysis have been used to generate a 1d space with locality preserving properties. This work provides empirical evidence to support the use of Hilbert’s curve in the context of locality preservation when generating peer identifiers by means of landmark vector analysis. A comparative analysis is carried out with an artificial 2d network model and with a realistic network topology model with a typical power-law distribution of node connectivity in the Internet. Nearest neighbour analysis confirms Hilbert’s curve to be very effective in both artificial and realistic network topologies. Nevertheless, the results in the realistic network model show that there is scope for improvements and better techniques to preserve locality information are required.

A parallel genetic algorithm for the Steiner Problem in Networks

This paper presents a parallel genetic algorithm to the Steiner Problem in Networks. Several previous papers have proposed the adoption of GAs and others metaheuristics to solve the SPN demonstrating the validity of their approaches. This work differs from them for two main reasons: the dimension and the characteristics of the networks adopted in the experiments and the aim from which it has been originated. The reason that aimed this work was namely to build a comparison term for validating deterministic and computationally inexpensive algorithms which can be used in practical engineering applications, such as the multicast transmission in the Internet. On the other hand, the large dimensions of our sample networks require the adoption of a parallel implementation of the Steiner GA, which is able to deal with such large problem instances.

A peer-to-peer approach to content dissemination and search in collaborative networks

There are three key driving forces behind the development of Internet Content Management Systems (CMS) - a desire to manage the explosion of content, a desire to provide structure and meaning to content in order to make it accessible, and a desire to work collaboratively to manipulate content in some meaningful way. Yet the traditional CMS has been unable to meet the latter of these requirements, often failing to provide sufficient tools for collaboration in a distributed context. Peer-to-Peer (P2P) systems are networks in which every node is an equal participant (whether transmitting data, exchanging content, or invoking services) and there is an absence of any centralised administrative or coordinating authorities. P2P systems are inherently more scalable than equivalent client-server implementations as they tend to use resources at the edge of the network much more effectively. This paper details the rationale and design of a P2P middleware for collaborative content management.

Mobility based energy efficient and multi-sink algorithms for consumer home networks

With the fast development of the Internet, wireless communications and semiconductor devices, home networking has received significant attention. Consumer products can collect and transmit various types of data in the home environment. Typical consumer sensors are often equipped with tiny, irreplaceable batteries and it therefore of the utmost importance to design energy efficient algorithms to prolong the home network lifetime and reduce devices going to landfill. Sink mobility is an important technique to improve home network performance including energy consumption, lifetime and end-to-end delay. Also, it can largely mitigate the hot spots near the sink node. The selection of optimal moving trajectory for sink node(s) is an NP-hard problem jointly optimizing routing algorithms with the mobile sink moving strategy is a significant and challenging research issue. The influence of multiple static sink nodes on energy consumption under different scale networks is first studied and an Energy-efficient Multi-sink Clustering Algorithm (EMCA) is proposed and tested. Then, the influence of mobile sink velocity, position and number on network performance is studied and a Mobile-sink based Energy-efficient Clustering Algorithm (MECA) is proposed. Simulation results validate the performance of the proposed two algorithms which can be deployed in a consumer home network environment.

Networks and plant disease management: concepts and applications

A network is a natural structure with which to describe many aspects of a plant pathosystem. The article seeks to set out in a nonmathematical way some of the network concepts that promise to be useful in managing plant disease. The field has been stimulated by developments designed to help understand and manage animal and human disease, as well as by technical infrastructures, such as the internet. It overlaps partly with landscape ecology. The study of networks has helped identify likely ways to reduce flow of disease in traded plants, to find the best sites to monitor as warning sites for annually reinvading disease, and to understand the fundamentals of how a pathogen spreads in different structures. A tension between the free flow of goods or species down communication channels and free flow of pathogens down the same pathways is highlighted.