Trust plays an important role in our daily life, both implicitly and explicitly. Our decisions are based on our estimation of how trustworthy a person is or how reliable a service is. Consequently, there has been a rise in trust systems that model human trust in a virtual or computing environment. These trust systems or trust models help to bridge the gap of human feelings and intuition in an unfamiliar environment. Trust models collect information regarding the participants' activities and give a trust rating based on observed activities. In a network environment, a plethora of network devices are in constant communication as data packets are transported from source to destination. The autonomous nature of network environments and devices make it difficult to monitor the services and devices from a central point. Security mechanisms, such as IPSec, exist in routing protocols to safeguard network packets travelling in a network, however routing devices that act as service providers are not protected by malicious attacks. For example, an attack aimed at the routing architecture of a network involves a routing device advertising itself as another routing device in order to divert network traffic away from its intended destination. This dissertation investigates trust models in network environments as a possible approach to predict and ultimately eliminate at- tacks on routing devices. To accomplish this, the role of routing devices as service providers and requesters must be stated explicitly. Activities on a routing device must be collected and used to determine the trust level of the routing device. This dissertation presents the TSONE - Trust in Service-Oriented Net- work Environment - model. The model incorporates traditional service- oriented architecture (SOA) principles to define a service-oriented network environment. Services in this environment are then defined. Furthermore the characteristics of this environment are adapted from SOA principles. An approach is defined to collect and measure activities on routing devices. This is later used to determine the trust level of the routing device. Finally, a pro- to type illustrates that incorporation of trust models is a possible option in assessing availability and reliability of routing devices. / Dissertation (MSc)--University of Pretoria, 2011. / Computer Science / unrestricted

The widespread use of wireless technologies has led to a tremendous development in wireless communication systems. Currently, an individual mobile user may carry multiple personal devices with multiple wireless interfaces, which can interconnect with each other to form a Wireless Personal Area Network (WPAN) which moves with this user. These devices exist in a heterogeneous environment which is composed of various wireless networks with differing coverage and access technologies and also the topology, device conditions and wireless connections in the WPAN may be dynamically changing. Such individual mobile users require ubiquitous communications anytime, anywhere, with any device and wish content to be efficiently and continuously transferred across the various wireless networks both outside and inside WPANs, wherever they move. This thesis presents research carried out into how to implement ubiquitous communications for WPANs in such an environment. Two main issues are considered. The first is how to initiate content transfer and keep it continuous, no matter which wireless network is used as a user moves or how the WPAN changes dynamically. The second is how to implement this transfer in the most efficient way: selecting the most suitable transfer mode for a WPAN according to the user’s and application’s requirements. User-centric (personal-area-centric) and contentcentric mechanisms are proposed in this thesis to address these issues. A scheme based on a Personal Distributed Environment (PDE) concept and designed as a logical user-based management entity is presented. This is based on three mechanisms which are proposed to overcome the technical problems in practical scenarios, which cannot be solved by existing approaches. A novel mechanism is proposed to combine local direct and global mobile communications, in order to implement ubiquitous communications in both infrastructure-less and infrastructurebased networks. This enables an individual user’s ubiquitous communications to be initiated in an infrastructure-less network environment and kept continuous when they move across infrastructure-based networks. Its advantages are evaluated by a performance analysis model and compared to existing solutions and verified by experiments. A cooperation and management scheme is also proposed for dynamic changes of multiple mobile routers and flexible switching of personal device roles in a WPAN while keeping ongoing ubiquitous communications continuous. This adopts a novel view of WPANs which solves the addressing problems caused by changes of mobile routers and makes these transparent to personal devices in the WPAN and external content sources. It provides an efficient method for changing the mobile router of a single WPAN or a WPAN merging with another moving network. Its benefits are demonstrated through performance analysis models. Finally, a novel user-centric and contentcentric mechanism for decision making, to select the most appropriate mobile router in a dynamically changing WPAN environment is proposed. This selects the most suitable content transfer mode for the WPAN to fulfil an individual user’s various requirements. It has different strategies to suit various types of applications. Selection results are demonstrated to verify the proposed mechanism in multiple scenarios of changing user requirements, applications and WPAN conditions.

Submitted by Haroudo Xavier Filho (haroudo.xavierfo@ufpe.br) on 2016-04-06T17:23:43Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Andson_M_Balieiro_PhDThesis_ComputerScience_2015.pdf: 2709720 bytes, checksum: 2432ca198603426dffdf0ce2f34f3162 (MD5) / Made available in DSpace on 2016-04-06T17:23:43Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Andson_M_Balieiro_PhDThesis_ComputerScience_2015.pdf: 2709720 bytes, checksum: 2432ca198603426dffdf0ce2f34f3162 (MD5) Previous issue date: 2015-08-28 / FACEPE / The wireless technologies are progressing at a rapid pace such that the future of digital communication will be dominated by a dense, ubiquitous and heterogeneous wireless network. Along with this, there is a growing demand for wireless services with different requirements. In this respect, the management of this complex wireless ecosystem becomes challenging, and the wireless virtualization is pointed as an efficient solution to perform it, where different virtual wireless networks can be created, sharing and running on the same wireless infrastructure, and providing differentiated services to users. However, to satisfy the high demand for mobile communications, it is necessary the availability of a natural and scarce resource, the electromagnetic spectrum. Although the insertion of virtualization in wireless networks provides better resources utilization, the current approaches to employ the wireless virtualization can cause resource underutilization. To overcome this underutilization and enable that new wireless virtual networks can be deployed, the wireless virtualization can be combined with the cognitive radio technology and dynamic spectrum access (DSA) techniques in order to achieve the deepest level of wireless virtualization and to improve the resource utilization through the deployment of opportunistic resource sharing. Thus, virtual wireless networks with different access priorities to the resources (e.g. primary and secondary) can be deployed in an overlay form, sharing the same substrate wireless network, where the secondary virtual network (SVN) accesses the resources only when the primary one (PVN) is not using them. However, this new scenario brings new challenges: from the mapping to operation of these networks. The SVN mapping is a NP-hard problem and presents some constraints and objectives related to both PVNs and SVNs. Achieving all objectives simultaneously is a challenging process. This thesis addresses the SVNs mapping problem onto substrate network considering the existence of the PVNs on the same substrate network. It discloses the environment composed by these networks, denoted as cognitive radio virtual network environment (CRVNE), models this environment by using a M/M/N/N queue with preemptive and priority service, and delineates a multi-objective problem formulation for the SVNs mapping. Moreover, a scheme based on Genetic Algorithms to solve the SVNs mapping problem is proposed and evaluated in terms of collision, secondary user (SU) dropping, and SU blocking probabilities, and joint utilization, achieving better results than other based on the First-Fit strategy. / Recentemente, as tecnologias sem fio estão progredindo rapidamente de modo que o futuro da comunicação digital será dominado por uma rede sem fio densa, ubíqua e heterogênea. Adicionado a isso, existe uma demanda crescente por serviços sem fio com diferentes requisitos. Neste aspecto, o gerenciamento deste ecossistema complexo se tona desafiador e a virtualização sem fio é apontada como uma solução eficiente para realizá-lo, onde redes virtuais sem fio diferentes podem ser criadas, compartilhando e executando sobre a mesma infraestrutura de rede sem fio e provendo serviços diferenciados aos usuários. Entretanto, para satisfazer à alta demanda por comunicação móvel é necessária a disponibilidade de um recurso natural e escasso, o espectro eletromagnético. Embora a inserção de virtualização em redes sem fio forneça maior utilização dos recursos, as abordagens atuais para empregar a virtualização sem fio podem causar subutilização de recursos. Para superar esta subutilização, a virtualização sem fio pode ser combinada com a tecnologia de rádio cognitivo e técnicas de acesso dinâmico ao espectro (DSA) para alcançar o mais profundo nível de virtualização sem fio e melhorar a utilização de recursos através do compartilhamento oportunista deles. Assim, redes virtuais sem fio com diferentes prioridades de acesso aos recursos (ex. primária e secundária) podem ser implantadas sobrepostas, compartilhando a mesma infraestrutura de rede sem fio, onde as redes virtuais secundárias (SVNs) acessam os recursos somente quando as redes virtuais primárias (PVNs) não os estiverem utilizando. Entretanto, este novo cenário traz novos desafios, desde o mapeamento até a operação destas redes. O mapeamento de SVNs é um problema NP-difícil e apresenta restrições e objetivos relacionados tanto às PVNs quanto às SVNs. Alcançar todos os objetivos simultaneamente é um processo desafiador. Esta tese aborda o problema de mapeamento de SVNs em redes de substrato considerando a existência de PVNs na mesma rede de substrato. Ela apresenta o ambiente de redes virtuais de rádio cognitivo (CRVNE), modela este ambiente utilizando uma fila M/M/N/N preemptiva e com prioridade e delineia uma formulação multiobjetivo para o mapeamento de SVNs. Além disso, um esquema baseado em Algoritmos Genéticos (GA) para resolver o problema de mapeamento de SVNs é proposto e avaliado em termos das probabilidades de colisão, descarte de usuário secundário (US), bloqueio de US e utilização conjunta, alcançando melhores resultados do que um esquema baseado na estratégia First-Fit.

Made available in DSpace on 2015-04-11T14:02:59Z (GMT). No. of bitstreams: 1 Alex Sander Pereira Regis.pdf: 1558751 bytes, checksum: 87bb0f2e05a92c301f304aa753235b32 (MD5) Previous issue date: 2013-09-27 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / A presente dissertação tem como horizonte temático a reflexão e análise de narrativas sobre a crise econômica mundial deflagrada inicialmente nos EUA em 2008, bem como sua articulação teórico-empírica com a ideia central da pesquisa, qual seja, a de que a ‗crise em questão está intimamente relacionada as implicações da Globalização, no quadro de uma ruptura teórico-epistemológica, cuja principal expressão é a crise generalizada de representações coletivas. Procurou-se no primeiro momento expor e problematizar a noção de Globalização a fim de privilegiar uma compreensão sobre globalização que sirva de pressuposto e soldo teórico para os fins do trabalho. No segundo momento apresento as diversas narrativas sobre a ‗crise , referidas, de um lado, em obras de teóricos ( Harvey, Boaventura, Touraine, Bauman), e de outro, em registros de análises extraídos de um arquivo digital construído a partir da sistematização de dados (artigos, entrevistas, dossiês etc) de três endereços eletrônicos (CartaMaior, IhuOnline e OutrasPalavras). Por fim, busca-se articular os momentos já referidos, tendo em vista operar as conexões de sentido entre a ‗crise econômica mundial , Globalização, Crise de representações coletivas e, portanto, apontar as implicações sociológicas daí oriundas, em outras palavras, no último momento afirmo que a crise evidencia, de um lado, as contradições e turbulências mais agudas de um período de ―ruptura histórico-epistemológica‖, de outro, a redefinição das representações coletivas clássicas através da intensificação de lutas , conflitos e resistências (Indignados, Occupy, Jornada de Junho etc) contra uma globalização totalitária que privilegia o mercado financeiro e, a favor de outras globalizações e formas de produzir e viver que valorizam a vida e suas populações. Conflitos e resistências que a longo e médio prazo determinaram o vir a ser do Estado-Nação e sua soberania; da Democracia e sua legitimidade, da globalização hegemônica face às globalizações contra e alter-hegemônicas. Estamos no interior de um parto histórico!