Network virtualization can offer more flexibility and better manageability for the future Internet by allowing multiple heterogeneous virtual networks (VN) to coexist on a shared infrastructure provider (InP) network. A major challenge in this respect is the VN embedding problem that deals with the efficient mapping of virtual resources on InP network resources. Previous research focused on heuristic algorithms for the VN embedding problem assuming that the InP network remains operational at all times. In this thesis, we remove that assumption by formulating the survivable virtual network embedding (SVNE) problem and developing baseline policy heuristics and an efficient hybrid policy heuristic to solve it. The hybrid policy is based on a fast re-routing strategy and utilizes a pre-reserved quota for backup on each physical link. Our evaluation results show that our proposed heuristic for SVNE outperforms baseline heuristics in terms of long term business profit for the InP, acceptance ratio, bandwidth efficiency, and response time.

Two research topics in next-generation optical networks with wavelength-division multiplexing (WDM) technologies were investigated: (1) scalability of network management and control, and (2) resilience/reliability of networks upon faults and attacks. In scalable network management, the scalability of management information for inter-domain light-path assessment was studied. The light-path assessment was formulated as a decision problem based on decision theory and probabilistic graphical models. It was found that partial information available can provide the desired performance, i.e., a small percentage of erroneous decisions can be traded off to achieve a large saving in the amount of management information. In network resilience under malicious attacks, the resilience of all-optical networks under in-band crosstalk attacks was investigated with probabilistic graphical models. Graphical models provide an explicit view of the spatial dependencies in attack propagation, as well as computationally efficient approaches, e.g., sum-product algorithm, for studying network resilience. With the proposed cross-layer model of attack propagation, key factors that affect the resilience of the network from the physical layer and the network layer were identified. In addition, analytical results on network resilience were obtained for typical topologies including ring, star, and mesh-torus networks. In network performance upon failures, traffic-based network reliability was systematically studied. First a uniform deterministic traffic at the network layer was adopted to analyze the impacts of network topology, failure dependency, and failure protection on network reliability. Then a random network layer traffic model with Poisson arrivals was applied to further investigate the effect of network layer traffic distributions on network reliability. Finally, asymptotic results of network reliability metrics with respect to arrival rate were obtained for typical network topologies under heavy load regime. The main contributions of the thesis include: (1) fundamental understandings of scalable management and resilience of next-generation optical networks with WDM technologies; and (2) the innovative application of probabilistic graphical models, an emerging approach in machine learning, to the research of communication networks.

With the progress of wireless radio technology and telecommunication, various wireless specifications and protocols form the unhandy heterogeneous network. The routing problems in heterogeneous network become popular researches nowadays. In this thesis, we integrate cellular (3G) network and Mobile Ad-Hoc Network (MANET) into a hybrid network. This hybrid network is called heterogeneous wireless network(HWN) with multi-cells architecture to overcome the weakness of cellular network and Ad-Hoc network. Based on HWN, we propose a routing algorithm with quality of service (QoS) supported for requirements in the original homogeneous cellular network and Ad-Hoc network. Simulation results show that HWN with the proposed algorithm has lower request block rate and shorter transmission time.

In the thesis, we study the rearrangeability of the Banyan-type network with crosstalk constraint. Let $x$, $p$ and $c$ be nonnegative integers with $0leq x,cleq n$ and $n,pgeq 1$. $B_{n}(x,p,c)$ is the Banyan-type network with, $2^{n+1}$ inputs, $2^{n+1}$ outputs, $x$ extra-stages, and each connection containing at most $c$ crosstalk switch elements. We give the necessary and sufficient conditions for rearrangeable Banyan-type networks $B_{n}(x,p,c)$.

Network virtualization can offer more flexibility and better manageability for the future Internet by allowing multiple heterogeneous virtual networks (VN) to coexist on a shared infrastructure provider (InP) network. A major challenge in this respect is the VN embedding problem that deals with the efficient mapping of virtual resources on InP network resources. Previous research focused on heuristic algorithms for the VN embedding problem assuming that the InP network remains operational at all times. In this thesis, we remove that assumption by formulating the survivable virtual network embedding (SVNE) problem and developing baseline policy heuristics and an efficient hybrid policy heuristic to solve it. The hybrid policy is based on a fast re-routing strategy and utilizes a pre-reserved quota for backup on each physical link. Our evaluation results show that our proposed heuristic for SVNE outperforms baseline heuristics in terms of long term business profit for the InP, acceptance ratio, bandwidth efficiency, and response time.

<p>Delivering content of interest to clients is one of the most important tasks of the Internet </p><p>and an everlasting research question of today's networking. Content distribution networks(CDNs) </p><p>emerged in response to the rising demand of content providers to deliver contents to clients efficiently, </p><p>reliably, and securely at relatively low cost.</p><p>This dissertation explores how CDNs can achieve major performance benefits by adopting better </p><p>caching strategies without changing the network, or by collaboration with ISPs and taking advantage of their </p><p>better knowledge of network status and topology. It discusses the emerging trends of hybrid CDN architectures </p><p>and solutions to reliability problems introduced by them. Finally, it demonstrates how CDNs could better </p><p>protect both content providers and consumers from attacks and other malicious behaviors.</p> / Dissertation

Purpose - The purpose of this study is to examine and map out the network innovative companies and to calculate values of the network structure in order to compare them to different performance measures. Furthermore, we aim to investigate the trade-off efficiency of innovations in a particular network structure, more specifically to investigate if the same elements generating more innovations have a relationship with economic performance that originates from innovations.   Methodology - This study give emphasis to map and illustrate the Swedish companies on NASDAQ OMX First North network through direct and indirect connection and to compare the centrality, density and size of the companies ego network in our population with the performance measures which are logically connected with the launch of an innovation; average EBITDA (earnings before interest, taxes, depreciation and amortization) and average annual turnover. Findings - First we noticed that there was a significant connection between a negative average EBITDA and positive average annual turnover for our population, as we foretold would occur during the launch of an innovation. Secondly, the paper suggests that there is a weak or near non-existent connection between the elements that generates more innovations and the result of innovations, e.g. the economic performance of innovative firms. This might indicate that the focus of recent studies in the subject might have been mistaken focusing on the quantity of innovation, when the basic assumption of an innovation is that it is qualitative and thereby generates money for the company. This study suggests that more innovations do not necessarily lead to better economic performance for the companies within our population.

The idea of a Media Frame network (MFN) was proposed very recently for solving the explosively growing demand for end-to-end large file transfers. This networking method combines the advantage of high transmission speed from optical networks and flexibility and fast header parsing from electronic networks. The MFN is based on very large data units or media frames (MF) compared to IP packets. Due to the logical continuity, transporting data in a media frame network largely reduces the power consumption in the intermediate nodes and routers. Currently the backbone of media frame network has been studied. The remaining challenge is to devise a system solving the problem of transporting MFs through access networks (i.e., the last mile) connecting customers to the backbone networks. To our knowledge, no other research activity regarding this challenge has been reported. If this challenge is overcome and if the overall concept is accepted, the MFN could be a very important step in the evolution of the Internet. This thesis focuses mainly on the access network. For the first time, a solution is proposed to establish the ability to transport media frames over a standard PON (e.g. Passive Optical Network) architecture. Because of the unique properties of the media frame network, the physical layer model and transport protocols must be rebuilt. Referring to the ITU-T G.987 recommendations, the physical layer is built based on the XGPON specification. In this thesis, the initialization protocols, bandwidth allocation plan, OLT-ONU (OLT: Optical Line Terminal, e.g. central office. ONU: Optical Network Unit, e.g. customer side box) negotiation protocols are designed. Different schemes for each protocol are proposed, with simulation support based on Omnet++. For the transmission of a 7GB file on average, different transparency degrees under different traffic conditions are compared, and the tradeoffs among essential factors are investigated. / Graduate

Made available in DSpace on 2014-06-12T15:48:27Z (GMT). No. of bitstreams: 2 arquivo1249_1.pdf: 1963665 bytes, checksum: 4d41d19894034bb41cfe58785e1d816a (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2011 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / Usuários de aplicações avançadas, tais os de grade computacional, encontram algumas vezes problemas de desempenho de rede que frustram as suas expectativas de realização de atividades. Por isso, a assistência para comunidades de usuários que tem dificuldades em usar a rede tem sido identificada como uma das principais questões de suporte relacionadas ao desempenho. Isso explica a crescente demanda por serviços de monitoramento que tentam auxiliar os usuários no entendimento das propriedades de rede, bem como no uso de suas aplicações. Serviços de monitoramento trouxeram grandes benefícios em termos de suporte aos usuários. Mesmo assim, existe uma carência por serviços de aconselhamento que beneficie os usuários com informações que vão além da simples apresentação das propriedades de rede. Atualmente, tanto usuários avançados quanto equipes de suporte contam com ferramentas que apresentam informações de uma perspectiva puramente técnica. A maioria delas se baseiam em informações obtidas como resultado de atividades de monitoramento, independentemente dos níveis de qualidade de serviços percebidos pelos usuários. Tais ferramentas de medição atendem razoavelmente os requisitos dos gerentes, operadores e usuários finais quando se trata de aplicações comuns. Contudo, a comunidade de pesquisa vem destacando a importância da qualidade de experiência (QoE) durante a avaliação dos serviços de rede quando se trata de aplicações avançadas. Ao considerar as opiniões dos usuários, o gerenciamento da qualidade de serviços torna-se mais efetivo, uma vez que a avaliação do serviço não está restrita às considerações da equipe de suporte e gerenciamento. Essa tese apresenta uma abordagem de aconselhamento para o suporte de usuários de rede que foca na colaboração entre usuários através do compartilhamento das suas experiências no uso das aplicações para construir uma base de conhecimento. O conhecimento representado inclui não somente a informação sobre os problemas de desempenho, como também as características as aplicações e as opiniões dos usuários. Através dessas características, a abordagem procura alcançar altos níveis de satisfação dos usuários pela redução gradual do volume de informações de suporte erradas. Para avaliar a viabilidade dessa abordagem, um modelo de sistema de raciocínio baseado em casos (RBC) foi construído e validado através de um estudo experimental conduzido em laboratório por meio de um sistema multiagente. O sistema é apoiado por uma base de conhecimento baseada no uso de ontologias e um esquema de reputação baseado no algoritmo Pagerank. Os resultados do estudo mostraram a efetividade da abordagem proposta, sua resilência à comportamento de usuários incoerentes e em conluio, e a importância do conhecimento do domínio sobre as atividades de suporte a usuários

Master thesis deals with the design of network topologies with multiple redundant links for investor’s local area network. The objective of the thesis is to design more topology proposals according to investor’s requirements and applied technologies. Design is based on an analysis of the current state, which describes current topology of investor’s network. The main part of the thesis proposes a solution based on currently available network redundancy protocols. The functionality of the proposed solutions is tested in laboratory conditions. Finally, the individual variants are compared and their individual benefits evaluated.