Dissertations / Theses on the topic 'Network infrastructure'

Wireless Local Area Networks (WLANs) have become a major success in telecommunications during the last few years, due to advantages such as mobility, flexibility, and easier maintenance. A device called an access point (AP) acts as a base station in WLAN for connecting a group of users to the network via radio signal. During the planning of such a network an important problem is to determine the optimal number of these devices and their placement/distribution so that coverage, capacity, and physical security are maximised at minimum cost. In this thesis we are using continuous optimisation techniques to optimise the number of APs and their distribution while cost of deployment is reduced and physical security of the network is enhanced. To find the number and placement of APs, we developed a multi-objective functions model based on path losses and power for free space environments. The two functions in the models are combined by using a balancing parameter. Since it is recognised that some of the objectives can be handled one at a time, in another approach, we followed a step-by-step procedure. We start with a novel optimisation model based on path losses for indoor environments including obstacles. Cost of deployment is saved by finding the minimum number of APs ensuring that the path loss at each test point/receiver is below the given maximum path loss. Next, the physical security of the network is enhanced by placing the APs far from places accessible to unauthorised users to reduce the risk of intrusion into the network. This is achieved in the framework of the model by introducing potential unauthorised users in unauthorised areas for whom coverage is minimised. Due to the presence of obstacles in indoor buildings, the path loss function is discontinuous. Therefore, the objective functions are very complicated and most of the existing optimisation algorithms cannot be applied to solve the problem. We use a global optimisation algorithm that is not used by other researchers to solve the same problem. To validate the accuracy of the optimisation model and performance of the numerical methods, we run tests on several indoor buildings and use wide range of WLAN parameters. The results demonstrate the quality of our model and algorithm. Based on the proposed model and algorithm, we developed a software to assist the network designers in planning wireless LANs.<br>Doctor of Philosophy

<p> The prosperity of the Internet has made it attractive to hackers and malicious attackers. Distributed attacks, such as: DDoS attacks and Internet worms have become major threats towards the network infrastructure. Collaborating existent single-point-deployed security applications over multi-domains for distributed defense is promising. Taking advantage of the small-world network model, a three-layered network modeling platform was developed for exploring behaviors of collaborative defense under the scope of a complex system. Using this platform, a comparison study between two major collaborative defense schemes was conducted. Their performance and eectiveness against signature-embedded worm attacks were evaluated accordingly. </p><p> Given the rapid evolution of attack methods and toolkits, software-based solutions to secure the network infrastructure have become overburdened. The performance gap between the execution speed of security software and the amount of data to be processed is ever widening. A common solution to close this performance gap is through hardware implementation of security functions. After a comprehensive survey on major recongurable hardware-based approaches application on network infrastructure security area, an optimized design of FPGA-based Power Spectral Density (PSD) data converter for online Shrew DDoS attack detection was proposed and prototyped. Combining an innovative component-reusable Auto-Correlation (AC) algorithm and the adapted 2N-point real-valued Discrete Fourier Transform (DFT) algorithm, a maximum reduction of 61.8% processing time from 27471.4 us to 10504.8 us was achieved. These ecient hardware realization enabled the implementation of this design to a Xilinx Virtex2 Pro FGPA. </p><p> The scalability issue against continuously expanding signature databases is another major impediment aecting hardware application for network intrusion detection. With the observation that signature patterns are constructed from combinations of a limited number of primary patterns, a two-stage decomposition approach was developed to solve this issue. The evaluation results show that a reduction in size of over 77% can be achieved on top of signature patterns extracted from the Snort rule database after decomposition.</p>

Approved for public release; distribution is unlimited<br>IPv6 deployment is increasing as IPv4 address allocations near exhaustion. Many large organizations, including the Department of Defense (DOD), have mandated the transition to IPv6. With the transition to IPv6, new techniques need to be developed to accurately measure, characterize, and map IPv6 networks. This thesis presents a method of profiling the uninterrupted system availability, or uptime, of IPv6 addressable devices. The techniques demonstrated in this study infer system restarts and the operational uptime for IPv6 network devices with a specific focus on IPv6 routers on the Internet. Approximately 50,000 IPv6 addresses were probed continuously from March to June 2014, using the Too Big Trick (TBT) to induce the remote targets to return fragmented responses. By evaluating the responses, the uptime for approximately 35% of the IPv6 addresses can be inferred.

After many years of research the area of Artificial Intelligence is still searching for ways to construct a truly intelligent system. One criticism is that current models are not 'rich' or complex enough to operate in many and varied real world situations. One way to tackle this criticism is to look at intelligent systems that already exist in nature and examine these to determine what complexities exist in these systems and not in the current Al models. The research begins by presenting an overview of the current knowledge of Biological Neural Networks, as examples of intelligent systems existing in nature, and how they function. Artificial Neural networks are then discussed and the thesis examines their similarities and dissimilarities with their biological counterparts. The research suggests ways that Artificial Neural Networks may be improved by borrowing ideas from Biological Neural Networks. By introducing new concepts drawn from the biological realm, the construction of the Artificial Neural Networks becomes more difficult. To solve this difficulty, the thesis introduces the area of Evolutionary Algorithms as a way of constructing Artificial Neural Networks. An intellectual infrastructure is developed that incorporates concepts from Biological Neural Networks into current models of Artificial Neural Networks and two models are developed to explore the concept that increased complexity can indeed add value to the current models of Artificial Neural Networks. The outcome of the thesis shows that increased complexity can have benefits in terms of learning speed of an Artificial Neural Network and in terms of robustness to damage.

Mestrado em Engenharia Electrónica e Telecomunicações<br>An evolution of the current university’s networking infrastructure and service models has been shown to be necessary to enable the provisioning of innovative services that are able to respond to today’s needs. On this work a network orchestration tool is proposed that, integrated with the OpenStack cloud framework, is able to virtualize any network deployment in a non-disruptive manner, providing a clean upgrade path from the traditional networking to the world of virtualization. The framework is able to extend virtual networks created on the datacenter by OpenStack or other cloud frameworks, to the outside campus. It does so by directly reconfiguring the network devices according to the needs, independently of the device vendor, the type of device or its specificities, and independently of the specific physical network topology. This service is provided to the end user using a cloud like service model, much more flexible than the current one, properly integrated with the cloud framework services. The project was developed with the Aveiro University use cases in mind, but the final result can be applied in many academic or business environments. The framework is presented both from a conceptual perspective, by describing the abstractions and mechanisms created, and from an implementation perspective, provinding the reader the necessary understanding about the framework operation and the integration with OpenStack. The integration of this work with a broader vision for the future of the university’s services is left as future work.<br>A evolução da actual infraestrutura de rede e modelos de serviço da universidade tem-se mostrado necessária para permitir o fornecimento de serviços inovadores capazes de responder às necessidades do mundo actual. Neste trabalho é proposta uma ferramenta de orquestração de rede que, integrada com a plataforma de cloud OpenStack, é capaz de virtualizar qualquer infraestrutura de rede de forma não disruptiva, proporcionando um modelo de actualização simples dos tradicionais serviços para o novo mundo da virtualização. A framework é capaz de estender as redes virtuais criadas no datacenter pelo OpenStack ou qualquer outra plataforma de cloud, para o campus. Fá-lo reconfigurando directamente os dispositivos de rede de acordo com as necessidades, independentemente do fabricante, do tipo de dispositivo ou das suas especificidades, e independentemente da topologia da rede física. O serviço é fornecido ao utilizador usando um modelo de cloud, muito mais flexivel que o modelo actual, devidamente integrado com os serviços da plataforma de cloud. O projecto foi desenvolvido com os casos de uso da Universidade de Aveiro em mente, mas o resultado final pode ser aplicado em muitos outros ambientes académicos ou empresariais. A framework é apresentada tanto do ponto de vista conceptual, descrevendo as abstrações e mecanismos criados, como do ponto de vista de implementação, dando ao leitor o entendimento necessário acerca da operação da ferramenta e da sua integração com o OpenStack. A integração deste trabalho com uma visão mais abrangente para o futuro dos serviços da universidade é deixada como trabalho futuro.

In the search and development of more participatory models for infrastructure development and management, in this dissertation, we investigate models for the financing, deployment, and operation of network and cloud computing infrastructures. Our main concern is to overcome the inherent exclusion in participation in the processes of development and management and in the right of use in the current dominant models. Our work starts by studying in detail the model of Guifi.net, a successful bottom-up initiative for building network infrastructure, generally referred to as a community networks. We pay special attention to its governance system and economic organisation because we argue that these are the key components of the success of this initiative. Then, we generalise our findings for any community network, aiming at becoming sustainable and scalable, and we explore the suitability of the Guifi.net model to the cloud computing infrastructure. As a result of both, we coin the attribute extensible to refer to infrastructure that is relatively easy to expand and maintain in contrast to those naturally limited or hard to expand, such as natural resources or highly complex or advanced artificial systems. We conclude proposing a generic model which, in our opinion, is suitable, at least, for managing extensible infrastructure. The Guifi.net model is deeply rooted in the commons; thus, the research in this field, in general, and Elinor Ostrom’s work, in particular, have left a profound imprint in our work. Our results show that the \guifinet model meets almost entirely the principles of long-enduring commons identified by E. Ostrom. This work has been developed as an industrial doctorate. As such, it combines academic research with elements of practice and pursues an effective knowledge transfer between academia and the private sector. Given that the private sector’s partner is a not-for-profit organisation, the effort to create social value has prevailed over the ambition to advance the development of a specific industrial product or particular technology.<br>En la recerca i desenvolupament de models més participatius per al desenvolupament i gestió d'infraestructura, en aquesta tesi investiguem sobre models per al finançament, desplegament i operació d'infraestructures de xarxa i de computació al núvol. La nostra preocupació principal és fer front a l’exclusió inherent dels models dominants actualment pel que fa a la participació en els processos de desenvolupament i gestió i, també, als drets d’us. El nostre treball comença amb un estudi detallat del model de Guifi.net, un cas d'èxit d'iniciativa ciutadana en la construcció d'infraestructura de xarxa, iniciatives que es coneixen com a xarxes comunitàries. En fer-ho, parem una atenció especial al sistema de governança i a l’organització econòmica perquè pensem que són els dos elements claus de l'èxit d'aquesta iniciativa. Tot seguit passem a analitzar d'altres xarxes comunitàries per abundar en la comprensió dels factors determinants per a la seva sostenibilitat i escalabilitat. Després ampliem el nostre estudi analitzant la capacitat i el comportament del model de Guifi.net en el camp de les infraestructures de computació al núvol. A resultes d'aquests estudis, proposem l'atribut extensible per a descriure aquelles infraestructures que són relativament fàcil d'ampliar i gestionar, en contraposició a les que o bé estan limitades de forma natural o be són difícils d'ampliar, com ara els recursos naturals o els sistemes artificials avançats o complexos. Finalitzem aquest treball fent una proposta de model genèric que pensem que és d'aplicabilitat, com a mínim, a tot tipus d'infraestructura extensible. El model de Guifi.net està fortament vinculat als bens comuns. És per això que la recerca en aquest àmbit, en general, i els treballs de Elinor Ostrom en particular, han deixat una forta empremta en el nostre treball. Els resultats que hem obtingut mostren que el model Guifi.net s'ajusta molt bé als principis que segons Ostrom han de complir els béns comuns per ser sostenibles. Aquest treball s'ha desenvolupat com a doctorat industrial. Com a tal, combina la investigació acadèmica amb elements de practica i persegueix una transferència efectiva de coneixement entre l'àmbit acadèmic i el sector privat. Ates que el soci del sector privat és una organització sense ànim de lucre, l’esforç per crear valor social ha prevalgut en l’ambició d’avançar en el desenvolupament d'un producte industrial específic o d'una tecnologia particular

Le parking intelligent, permettant aux conducteurs d'accéder aux informations de stationnement sur leurs appareils mobiles, réduit les difficultés des usagers. Tout d'abord, nous mettons en lumière la manière de recueillir les informations de parking en introduisant une architecture de réseaux de capteurs multi-saut, et les modèles d'intensité applicative en examinant la probabilité d'arrivées et de départs de véhicules. Puis nous étudions la stratégie de déploiement des réseaux de capteurs et définissons un problème multi-objectifs, puis nous le résolvons sur deux cartes de parking réelles. Ensuite, nous définissons un service Publish-Subscribe pour fournir aux conducteurs des informations pertinentes. Nous illustrons le système dans des réseaux véhiculaires et mobiles et soulignons l'importance du contenu et du contexte du message au conducteur. Afin d'évaluer la résilience du système, nous proposons un modèle Publish-Subscribe étendu et nous l'évaluons dans différentes circonstances imprévues. Notre travail est basé sur la prémisse que les capteurs de parking sont déployés à une grande échelle dans la ville. Nous considérons une vue d'ensemble des services urbains du point de vue de la municipalité. Ainsi, nous faisons la lumière sur deux thèmes principaux: la collecte d'informations sur le déploiement de capteurs et un modèle étendu de Publish-Subscribe. Notre travail donne un guide avant de démarrer un projet de parking intelligent ou tout service urbain similaire en temps réel. Il fournit également une plate-forme d'évaluation valable pour tester des jeux de données plus réalistes, comme des traces de véhicules ou de trafic réseau<br>Smart parking, allowing drivers to access parking information through their smart-phone, is proposed to ease drivers' pain. We first spotlight the manner to collect parking information by introducing the multi-hop sensor network architecture, and how the network is formed. We then introduce the traffic intensity models by looking at the vehicle's arrival and departure probabilities, following the heavy-tailed distribution. We study the deployment strategy of wireless on-street parking sensor layouts. We define a multiple-objective problem and solve it with two real street parking maps. In turn, we present a Publish-Subscribe service system to provide good parking information to drivers. We illustrate the system with a vehicular network and point out the importance of content and context of a driver’s message. To evaluate the resilience, we propose an extended Publish-Subscribe model, and evaluate it under different unforeseen circumstances. Our work is based on the premise that large-scale parking sensors are deployed in the city. We look at the whole picture of urban service from viewpoint of the municipality. As such, we shed light on two main topics: the information collection on sensor deployment and an extended version of Publish-Subscribe messaging paradigm. Our work gives a guideline from network-related perspectives for city before launching a smart parking or any similar real-time urban service. It also provides a meaningful evaluation platform for testing more realistic datasets, such as real vehicle traces or network traffic

With the increasing demand for energy throughout the world and the associated environmental problems, the development of a highly efficient and environmentally friendly Smart Grid has become an important objective worldwide. In Great Britain, the Smart Grid has been primarily focused on the distribution networks and smart metering is widely considered as a critical step towards the Smart Grid future. Conventionally, the communications infrastructure at the distribution level is very limited in terms of functionality and availability. There was very limited work to evaluate the impact of the communications performance of smart metering infrastructure on distribution network operation. This research investigated the impact of smart metering applications on communications requirements and the impact of the communications performance of smart metering infrastructure on distribution network operation. A smart metering communications infrastructure was modelled and simulated using OPNET. The impact of smart metering applications on smart metering communications requirements has been investigated. It is shown that individual communications requirements for smart meters are not particularly communications intensive and that infrequent large transactions posed the most significant challenges on the communications infrastructure. As the link speed decreased, large time delays were observed which have direct impact on the functions related to distribution network operations. An evaluation method was then developed to quantify the impact of smart metering communications infrastructure on distribution network operation. The main characteristics of the smart metering communications infrastructure were modelled. The characteristics of load variation were analysed and used to quantify the relationship between the time delay and the measurement error of the power system. The measured data from smart meters was refined to be used by the distribution network operational functions using state estimation and the impact was quantified using optimal power flow. Results show that fast data access is necessary for smart meter data to be used by the voltage control and the power control functions of a distribution network. The potential of using smart metering for outage management was investigated. A topology analysis method was developed which maps the physical plant model of a distribution network to a simplified analytical model. An outage area identification algorithm was developed which uses the information from smart meters and is based on the simplified network model. The outage area identification can act as one of the main functions of an outage management system providing possible outage extent information. The impact of smart meter communications on the outage area identification algorithm was investigated based on the OPNET communications model. Test results showed that smart metering has a potential to support outage management of a power distribution network. Test results showed that the arrival criterion and the smart metering communications infrastructure have a large impact on the performance of the outage area identification.

Thesis (Ph. D.)--Ohio State University, 2003.<br>Title from first page of PDF file. Document formatted into pages; contains xvi, 188 p.; also includes graphics (some col.). Includes abstract and vita. Advisor: Jean-Michel Guldmann, Dept. of City and Regional Planning. Includes bibliographical references (p. 164-170).

This paper seeks to describe and explain the social efficacy of art by addressing it as contemporary western infrastructure for social cohesion. Social cohesion refers here not to teleological status quo, but to pluralistic, yet fairly peaceful co-habitation, allowing for gradual change while preserving continuity of the group identity. Employing Actor-Network Theory, this paper views artistic practice as actor-network assemblage process making connections and vehicles that enable movement of ideas, values, visions and dissents throughout the community. Parallel memberships of the same actors in artistic and non-artistic actor-networks create conditions for artistic meanings to “bleed over” also into other spheres of the social life where they can gain efficacy far beyond the “art world”. Art infrastructure operates under particular “regime of art” that suspends some of the “real world” rules and sanctions ambiguity, facilitating less confrontational reconciliation of diverse and contradictory meanings than is customary in e.g. science, religion, politics, economy, railways, sewage or other infrastructures that also have impact on social cohesion. Debates about the definitions of “art” or particular objects’ belonging to “art” emerge in this perspective as debates on the scope of applicability of the “regime of art”, as it may have significant social consequences. By outlining an infrastructural theory of art this paper seeks to fill a theoretical gap in a rather fragmented field of anthropology of art and to propose novel ways to deploy insights from anthropological engagements with infrastructure. Empirical data of this paper come from a five weeks fieldwork in Alaska.

Magister Scientiae - MSc<br>This thesis shows that mobility management protocols for infrastructure Internet may be used in a wireless mesh network environment. In this research Mobile IPv6 and Fast Handover for Hierarchical Mobile IPv6 are successfully implemented in a wireless mesh network environment. Two experiments were carried out: vertical and horizontal handover simulations. Vertical handover simulation involved a heterogeneous wireless environment comprising both wireless local area and wireless mesh networks. An OPNET Mobile IPv6 model was used to simulate the vertical handover experiment. Horizontal handover simulation involved Mobile IPv6 and Fast Handover for Hierarchical Mobile IPv6 applied in ns2 wireless mesh network. The vertical handover results show that MIPv6 is able to manage vertical handover between wireless local area and wireless mesh network. The horizontal handover results illustrate that in mesh networks, Fast Handover for Hierarchical Mobile IPv6's performance is superior to Mobile IPv6. Fast Handover for Hierarchical Mobile IPv6 generates more throughput and less delay than Mobile IPv6. Furthermore, Fast Handover for Hierarchical Mobile IPv6 drops less data packets than Mobile IPv6. The simulations indicate that even though there are multi-hop communications in wireless mesh networks, the performance of the multi-hop routing may not play a big role in the handover performance. This is so because the mesh routers are mostly static and the multi-hop routes are readily available. Thus, the total handover delay is not affected too much by the WMN hops in the paths for signaling message transmission.<br>South Africa

This dissertation is directed towards improving the performance of 5G Wireless Fronthaul Networks and Wireless Sensor Networks, as measured by reliability, fault recovery time, energy consumption, efficiency, and security of transmissions, beyond what is achievable with conventional error control technology. To achieve these ambitious goals, the research is focused on novel applications of networking techniques, such as Diversity Coding, where a feedforward network design uses forward error control across spatially diverse paths to enable reliable wireless networking with minimal delay, in a wide variety of application scenarios. These applications include Cloud-Radio Access Networks (C-RANs), which is an emerging 5G wireless network architecture, where Remote Radio Heads (RRHs) are connected to the centralized Baseband Unit (BBU) via fronthaul networks, to enable near-instantaneous recovery from link/node failures. In addition, the ability of Diversity Coding to recover from multiple simultaneous link failures is demonstrated in many network scenarios. Furthermore, the ability of Diversity Coding to enable significantly simpler and thus lower-cost routing than other types of restoration techniques is demonstrated. Achieving high throughput for broadcasting/multicasting applications, with the required level of reliability is critical for the efficient operation of 5G wireless infrastructure networks. To improve the performance of C-RAN networks, a novel technology, Diversity and Network Coding (DC-NC), which synergistically combines Diversity Coding and Network Coding, is introduced. Application of DC-NC to several 5G fronthaul networks, enables these networks to provide high throughput and near-instant recovery in the presence of link and node failures. Also, the application of DC-NC coding to enhance the performance of downlink Joint Transmission-Coordinated Multi Point (JT-CoMP) in 5G wireless fronthaul C-RANs is demonstrated. In all these scenarios, it is shown that DC-NC coding can provide efficient transmission and reduce the resource consumption in the network by about one-third for broadcasting/multicasting applications, while simultaneously enabling near-instantaneous latency in recovery from multiple link/node failures in fronthaul networks. In addition, it is shown by applying the DC-NC coding, the number of redundant links that uses to provide the required level of reliability, which is an important metric to evaluate any protection system, is reduced by about 30%-40% when compared to that of Diversity Coding. With the additional goal of further reducing of the recovery time from multiple link/node failures and maximizing the network reliability, DC-NC coding is further improved to be able to tolerate multiple, simultaneous link failures with less computational complexity and lower energy consumption. This is accomplished by modifying Triangular Network Coding (TNC) and synergistically combining TNC with Diversity Coding to create enhanced DC-NC (eDC-NC), that is applied to Fog computing-based Radio Access Networks (F-RAN) and Wireless Sensor Networks (WSN). Furthermore, it is demonstrated that the redundancy percentage for protecting against n link failures is inversely related to the number of source data streams, which illustrates the scalability of eDC-NC coding. Solutions to enable synchronized broadcasting are proposed for different situations. The ability of eDC-NC coding scheme to provide efficient and secure broadcasting for 5G wireless F-RAN fronthaul networks is also demonstrated. The security of the broadcasting data streams can be obtained more efficiently than standardized methods such as Secure Multicasting using Secret (Shared) Key Cryptography.

Current transport network owners are focused on offering services on top of the infrastructures they own, while end users have no control over them. Traditionally, this has been their business model, as the cost of building the infrastructures to provide services is considerably high. However, the traffic on Internet has been, and still is, rapidly increasing over the years. Additionally new emerging services are pushing the limits of existing telecommunication infrastructures, particularly transport optical networks. To overcome such situation, network virtualization has been considered as an effective solution for the future optical networks architectures. Thanks to Virtual Optical Networks (VONs), it is possible to create mission-specific logic infrastructures, which fulfil the exact requirements of the applications that will run on top of them, sharing a unique physical substrate. However, the applicability of virtualization techniques to the optical domain is still under research, being on key point the mapping of the virtual resources to the actual physical ones. However, virtualization per se does not provide a solution flexible enough in terms of bandwidth utilization. For this to happen, an equally flexible transport technology must be adopted. Elastic Optical Networks (EONs) have been presented as an efficient solution for flexible bandwidth allocation. Additionally, due to the dinamicity of the traffic patterns that such virtual networks will face, it is highly desirable to provide a physical substrate that will help on keeping the associated operational expenditures (OPEX) at low levels, being a very important parameter the energy consumption. The energy consumption topic has been subject of big research efforts in order to provide more energy efficient optical transport networks, which, at their turn, will help on the creation of less costly virtual infrastructures. This thesis is devoted to the study of resource allocation to VONs, aiming to provide a flexible, efficient and optimized environment for the embedding of the VONs to the actual physical substrate. The considered scenario is composed of an underlying optical transport network and multiple client VONs that have to be allocated on top. In such scenario, a key aspect relates to how actual resources are associated to the virtual ones, guaranteeing the isolation among VONs and satisfying the resources requirements of every one of them. After an introduction to the thesis, chapter 2 surveys nowadays optical network infrastructures, concluding on the need to move towards a more dynamic and efficient optical network infrastructure. Next, it proceeds to summarize the state of the art of the concepts that enable for such network architecture, namely, VONs, EONs and energy efficient optical infrastructures. Then, chapters 3, 4 and 5 focus on providing solutions to optimize specific aspects of these enabling concepts. More in details, chapter 3 studies the main challenges on the VON embedding problem and presents solutions that allow for an optimized resoure assignment to VONs in a physical substrate depending on the VONs characteristics and the sppecific network substrate. Chapter 4 proposes the Split Spectrum (SS) approach as a way to improve the spectrum utilization of EONs. Finally, chapter 5 focuses on provide and evaluate routing and architectural solutions in aims to reduce the energy consumption of the optical substrate so as VONs with lower OPEX can be deployed on top of it.<br>Els actuals propietaris de xarxes de transport es centren en oferir serveis mitjançant les infraestructures que posseeixen, mentre els usuaris finals no tenen cap control sobre aquests. Tradicionalment, aquest ha estat el seu model de negoci, ja que el cost de construir aquestes infraestructures és considerablement elevat. Tanmateix, el tràfic a Internet ha estat creixent de manera ràpida durant els últims anys. A més, l'aparició de nous serveis està portant al límit les actuals infraestructures de telecomunicacions, especialment les xarxes òptiques de transport. Per tal de superar aquesta situació, la virtualització de xarxes és considerada com una solució efectiva per les futures arquitectures de xarxes òptiques. Gràcies a les Xarxes Òptiques Virtuals (VONs), és possible crear infraestructures lògiques específiques en la seva missió, les quals permeten satisfer els requisits de les aplicacions que s'executaran a través d'elles, compartint un únic substrat físic. Tanmateix, l'aplicació de les tècniques de virtualització en el domini òptic encara és subjecte d'investigació, sent el mapeig entre els recursos virtuals i els recursos físics un punt clau que cal adreçar. No obstant això, la virtualització en si mateixa no proporciona una solució prou flexible en termes d'utilització de l'espectre. Per aquest motiu és necessari que el substrat físic adopti una tecnologia igualment flexible. Les Xarxes Òptiques Elàstiques (EONs) es presenten com una solució eficient per a una assignació flexible de l'espectre. A més, a causa del dinamisme dels perfils de trafic als quals s'enfrontaran les VONs, és desitjable proporcionar una infraestructura física que ajudi a mantenir baixes les despeses operatives (OPEX) d'aquestes xarxes, sent un paràmetre molt important el consum energètic. El tema del consum energètic ha estat subjecte de grans iniciatives de recerca per tal de proporcionar xarxes de transport òptiques més eficients energèticament, les quals permetran crear VONs menys costoses. Aquesta tesi està dedicada a l'estudi l'assignació de recursos a les VONs, amb l'objectiu de proporcionar un entorn flexible, eficient i optimitzat per a la incrustació de les VONs al substrat físic. L'escenari considerat es compon d'una xarxa de transport subjacent i múltiples VONs client a col·locar sobre el substrat físic. En aquest escenari, un aspecte clau es refereix a com els recursos reals s'associen als virtuals, garantint l'aïllament entre VONs i satisfent els recursos demanats per cada una d'elles. Després d'una introducció a la tesi, el capítol 2 revisa les infraestructures de xarxa òptica actuals, concloent en la necessitat d'avançar cap a infraestructures més dinàmiques i eficients. Tot seguit, es procedeix a resumir l'estat de l'art dels conceptes que habilitaran aquesta arquitectura de xarxa, bàsicament, VONs, EONs i les xarxes òptiques de baix consum. A continuació, els capítols 3, 4 i 5 es centren en proporcionar solucions per optimitzar aspectes específics d'aquests conceptes. Més en detall, el capítol 3 estudia els principals reptes en el problema de la incrustació de VONs i presenta solucions que permetin assignar recursos de manera optimitzada a les VONs en un substrat físic. El capítol 4 proposa el concepte de l'Split Spectrum (SS) com una forma de millorar la utilització de l'espectre en les EONs. Finalment, el capítol 5 es centra en proporcionar i avaluar solucions arquitectòniques i d'enrutament amb l'objectiu de reduir el consum d'energia del substrat òptic de tal manera que VONs amb menor OPEX puguin ser desplegades a través d'ell.<br>Los actuales propietarios de las redes de transporte se centran en ofrecer servicios mediante las infraestructuras que poseen y gestionan, mientras que los usuarios finales no tienen ningún control sobre estos. Tradicionalmente, este ha sido el modelo de negocio adoptado por los operadores de redes, ya que el coste de construir y mantener las infraestructuras correspondientes por tal de ofrecer servicios mediante ellas era, y aun es, considerablemente elevado. No obstante, el tráfico en Internet ha crecido de manera rápida y sostenida durante los últimos años y se prevé que continuara con este crecimiento en el futuro. Además, la aparición de nuevos servicios y paradigmas, están llevando al límite las actuales infraestructuras de telecomunicaciones, especialmente las redes de trasporte óptico. Por tal de superar dicha situación, la virtualización de redes ha sido considerada como una solución efectiva para las futuras arquitecturas de redes ópticas. Gracias a las Redes Ópticas Virtuales (VONs), es posible crear infraestructuras lógicas especificas en su misión, las cuales podrán satisfacer los requisitos de las aplicaciones que se ejecutaran a través de ellas, usando y compartiendo un único sustrato físico. No obstante, la aplicación de las técnicas de virtualización en el dominio óptico aun es sujeto de investigación, siendo el mapeo entre los recursos virtuales y los físicos (también conocido como incrustación de la red virtual) un punto clave a solucionar. No obstante, la virtualización por si misma no ofrece una solución suficientemente flexible en términos de utilización del ancho de banda. Por tal de proporcionar un entorno de virtualización suficientemente flexible para acomodar cualquier ancho de banda con suficiente granularidad, es necesario que el sustrato físico adopte una tecnología de transporte igual de flexible. Las Redes Ópticas Elásticas (EONs) se presentan como una solución eficiente para una asignación flexible del ancho de banda en redes ópticas. Además, debido a la heterogeneidad y dinamismo de los perfiles de tráfico a los cuales se enfrentaran las redes virtuales, es altamente deseable proporcionar una infraestructura física que ayuda a mantener bajos los gastos operativos (OPEX) de estas redes, siendo un parámetro muy importante el consumo energético asociado a la operación de las VONs. El tema del consumo energético ha sido, y aun es, sujeto de grandes iniciativas de investigación centradas en desarrollar nuevas arquitecturas de dispositivos o algoritmos de asignación de recursos conscientes del consumo energético por tal de proporcionar redes de transporte ópticas más eficientes energéticamente que, a su vez, permitan crear infraestructuras virtuales menos costosas des del punto de vista energético. Esta tesis se centra en el estudio de la composición y asignación de recursos a las VONs, con el objetivo de proporcionar un entorno flexible, eficiente y optimizado para la incrustación de las VONs en el sustrato físico real. El escenario considerado se compone de una red de transporte subyacente, ya sea una Red Óptica de Conmutación de Longitud de Onda (WSON) o EON, y múltiples VONs cliente, las cuales se colocaran encima del sustrato físico. En este escenario, un aspecto clave se refiere a como los recursos reales se asocian a los virtuales, garantizando el aislamiento entre VONs y satisfaciendo los recursos pedidos (por ejemplo, capacidad de enlace) por cada una de ellas. Después de una introducción a la tesis, el capítulo 2 revisa las infraestructuras de redes ópticas actuales, concluyendo en la necesidad de avanzar hacia una infraestructura de red óptica más dinámica y eficiente por tal de afrontar el crecimiento del tráfico en Internet y la aparición de nuevos servicios y paradigmas. Seguidamente, se procede a resumir el estado del arte de los conceptos y paradigmas que permitirán habilitar esta arquitectura de red, básicamente, VONs, EONs y las infraestructuras ópticas de bajo consumo energético. A continuación, los capítulos 3, 4 y 5 se centran en proporcionar soluciones para optimizar aspectos específicos de estos conceptos con la finalidad de proporcionar un marco optimizado que ayudara en la configuración de las futuras infraestructuras de redes ópticas y sus modelos de negocio. Concretamente, el capítulo 3 estudia los principales retos en el problema de la incrustación de VONs y presenta soluciones que permiten una asignación de recursos optimizada a las VONs en un sustrato físico dependiendo de las características de las VONs y del sustrato de red. El capítulo 4 propone el concepto de Split Spectrum (SS) como una forma de mejorar la utilizaci_on del espectro en las EONs. Finalmente, el capítulo 5 se centra en proporcionar y evaluar soluciones arquitectónicas y de enrutamiento con el objetivo de reducir el consumo energético del sustrato óptico de tal manera que VONs con menor OPEX puedan ser desplegadas mediante este sustrato.

The dissertation investigates the issues of dependability of the Internet network infrastructure that were studied by using the network topology analysis, graph theory and network modelling. The object of the study is the Internet network infrastructure, based on autonomous systems and interconnecting lines. Stable functioning of the Internet network determines the availability of information, electronic commerce, control of remote objects, etc. The main objective is to develop the methodologies and algorithms for analysing the Internet network infrastructure and controlling the reliability of functioning. The scope of application of the study is the supervision and regulation of continuity of the Internet. The following main tasks are solved: development of the topological scheme of the Internet network, selection of models and tools for analysis; the Internet network connectivity analysis for the purpose of identification of the critical network elements, whose violations would result in loss of connectivity of the network; as well as development of the model for monitoring of the critical elements of the Internet network and cyber-attacks simulation experiments. The scientific work consists of the general characteristic of the dissertation, 5 chapters, conclusions, list of literature, list of publications and annexes.<br>Disertacijoje nagrinėjama interneto tinklo infrastruktūros patikimumo problematika, analizei naudojant tinklo topologijos tyrimus, grafų teorijos taikymą ir tinklo modeliavimą. Tyrimų objektas, interneto tinklo infrastruktūra, kurios pagrindą sudaro autonominės sistemos ir tarptinklinių sujungimų linijos. Nuo stabilios interneto tinklo veiklos priklauso informacijos pasiekiamumas, elektroninė komercija, nutolusių objektų valdymas ir t. t. Pagrindinis disertacijos tikslas – sukurti metodikas ir algoritmus, skirtus interneto tinklo infrastruktūros analizei bei veiklos patikimumo kontrolei. Tyrimų taikymo sritis – interneto tinklo veiklos tęstinumo priežiūra ir reguliavimas. Darbe sprendžiami šie pagrindiniai uždaviniai: interneto tinklo topologijos analizės modelio ir priemonių sudarymas; interneto junglumo tyrimas siekiant identifikuoti kritinius elementus, kurių pažeidimai susiję su tinklo funkcionalumo praradimu; kritinių interneto tinklo elementų stebėsenos modelio sudarymas; eksperimentiniai kibernetinių atakų simuliacijos bandymai; bei interneto tinklo infrastruktūros patikimo stiprinimo parinkimas. Disertaciją sudaro įvadas, 5 skyriai, rezultatų apibendrinimas, naudotos literatūros ir autoriaus publikacijų disertacijos tema sąrašai bei priedai.

Companies that operate with critical infrastructure face a growing threat from cyber-attacks while at the same time the development in the business is rapidly moving towards a higher level of digitalization. A common type of system in critical infrastructure is supervisory control and data acquisition systems, these systems have properties that can affect their security and will therefore serve as the basis for this thesis work. To stay protected despite systems changes, companies need to make risk assessments in order to analyze how changes will affect the overall system. One thing that is important to focus on is dependencies within the system, this means that not only interaction among computers and networks are concerned but instead a more holistic view of the system need to be considered. This thesis aims to aid the process of a future risk assessment by providing a methodology to be used as a preparatory step before a risk assessment by describing the current situation of the system. This is done by evaluating two system modeling approaches, and also by proposing a number of perspectives that each provides different kind of information about the system’s dependencies. These perspectives are then evaluated by creating system models and dependency graphs, and discussing the outcomes with experts in a utility company to find out their applicability. According to the experts, the proposed perspectives have promising properties that can be useful in future risk assessments as well as in other scenarios. Moreover, the evaluated modeling approaches got positive comments during evaluation and are considered to serve their purpose.

Approved for public release; distribution is unlimited<br>The potential for cascade failure of the U.S. crude oil pipeline infrastructure is analyzed using Model Based Risk Assessment software. The pipeline system that distributes crude oil to refineries across the United States has gained much media attention with President Obamas denial of a permit to complete a key portion the Keystone-XL pipeline that will carry oil from Alberta, Canada to the Cushing Oil Trading Hub (COTH) in Cushing, OK. The analysis identified the COTH as the primary critical hub. The COTH is one of the worlds major oil terminals. A disruption of the COTH, Midwest/West Coast oil distribution networks, or critical hubs would have far-reaching negative consequences affecting global trade. The analysis also identified regional differences in network resiliency and susceptibility to cascade failure. Protecting all 55,000 miles of the U.S. crude oil pipeline infrastructure from catastrophic failure is an unachievable goal, but protection of the network from cascade failure and a Black Swan event can be achieved by protecting network hubs. The results of this analysis should be used as a starting point to increase network resiliency and prioritize the use of resources to secure the crude oil pipeline network against cascade failure.

Cloud Infrastructure-as-a-Service (IaaS) is a form of utility computing which has emerged with the recent innovations in the service computing and data communication technologies. Regardless of the fact that IaaS is attractive for application service providers, satisfying user requests while ensuring cloud operational objectives is a complicated task that raises several resource management challenges. Among these challenges, limited controllability over network services delivered to cloud consumers is prominent in single datacenter cloud environments. In addition, the lack of seamless service migration and optimization, poor infrastructure utilization, and unavailability of efficient fault tolerant techniques are noteworthy challenges in geographically distributed datacenter clouds. Initially in this thesis, a datacenter resource management framework is presented to address the challenge of limited controllability over cloud network traffic. The proposed framework integrates network virtualization functionalities offered by software defined networking (SDN) into cloud ecosystem. To provide rich traffic control features to IaaS consumers, control plane virtualization capabilities offered by SDN have been employed. Secondly, a quality of service (QoS) aware seamless service migration and optimization framework has been proposed in the context of geo-distributed datacenters. Focus has been given to a mobile end-user scenario where frequent cloud service migrations are required to mitigate QoS violations. Finally, an SDN-based dynamic fault restoration scheme and a shared backup-based fault protection scheme have been proposed. The fault restoration has been achieved by introducing QoS-aware reactive and shared risk link group-aware proactive path computation algorithms. Shared backup protection has been achieved by optimizing virtual and backup link embedding through a novel integer linear programming approach. The proposed solutions significantly improve bandwidth utilization in inter-datacenter networks while recovering from substrate link failures.

Doctor of Philosophy<br>Department of Biological & Agricultural Engineering<br>Naiqian Zhang<br>A two-tier wireless data communication system was developed to remotely monitor sediment concentration in streams in real time. The system used wireless motes and other devices to form a wireless sensor network to acquire data from multiple sensors. The system also used a Stargate, a single-board computer, as a gateway to manage and control data flow and wireless data transfer. The sensor signals were transmitted from an AirCard on the Stargate to an Internet server through the General Packet Radio Service (GPRS) provided by a commercial GSM cellular carrier. Various types of antennas were used to boost the signal level in a radio-hostile environment. Both short- and long-distance wireless data communications were achieved. Power supplies for the motes, Stargate, and AirCard were improved for reliable and robust field applications. The application software was developed using Java, C, nesC, LabView, and SQL to ensure seamless data transfer and enable both on-site and remote monitoring. Remote field tests were carried out at different locations with different GPRS signal strengths and a variety of landscapes. A three-tier wireless sensor network was then developed and deployed at three military installations around the country – Fort Riley in Kansas, Fort Benning in Georgia, and Aberdeen Proving Ground in Maryland - to remotely monitor sediment concentration and movement in real time. Sensor nodes, gateway stations, repeater stations, and central stations were strategically deployed to insure reliable signal transmissions. Radio signal strength was tested to analyze effects of distance, vegetation, and topographical barriers. Omni- and Yagi-directional antennas with different gains were tested to achieve robust, long-range communication in a wireless-hostile environment. Sampling times of sensor nodes within a local sensor network were synchronized at the gateway station. Error detection algorithms were developed to detect errors caused by interference and other impairments of the transmission path. GSM and CDMA cellular modems were used at different locations based on cellular coverage. Data were analyzed to verify the effectiveness and reliability of the three-tier WSN.

Cruise tourism is the fastest growing sector within the global leisure travel industry. This growth is manifested in the number of passengers and ships being added to the global cruise fleet each year as well as the size of ships. Also, new destinations continue to be added as many coastal cities aspire to deriving economic benefit from cruise tourism. Accordingly, destinations are obliged to consider the (re)development of new cruise infrastructure. Stakeholders within these destinations form networks, initially to advance proposals for that (re)development. These networks may be formal or informal, but each is faced with issues such as the exercise of power within the network, how stakeholders engage with each other, the existence of competing interests and the control over information. In networks where effective governance mechanisms are in place, greater network cohesion and therefore consensus can be achieved, However, where no such mechanisms exist, network fragmentation can result. Network fragmentation can give rise to risks which threaten cruise infrastructure development projects. Previous studies on cruise infrastructure development have focused either on the impacts of cruise infrastructure on host communities and the environment or on stakeholder and community response to cruise infrastructure development. A few have considered the specific issues of cruise port economics and governance. In contrast, studies in the area of public infrastructure development, generally, have recognised that key stakeholders form networks to advance proposals for development and have described those networks. However, limited research appears to have addressed the specific topics of the formation of networks to progress cruise infrastructure development. Moreover, there appears to be an absence of research on the types or characteristics of those networks, the operation of power within them and the potential for risk where there is political debate or dysfunction. Thus, the aim of this research is to understand how stakeholder networks influence proposals for cruise infrastructure development. In the context of this research, the term stakeholder network is used to identify the type of social network which has formed. However, the empirical research undertaken in this study informs a discussion which presents opportunities to further refine the types of networks which form to influence such proposals. Identification of the specific type of network which has formed can assist key stakeholders effectively manage such networks. This research uses a mixed methods approach to address this aim. It uses a media discourse analysis approach to identify the issues of concern to stakeholders over an eightyear period and to build a rich case study based on these issues. In-depth, semi-structured interviews probed stakeholders’ responses to a range of pertinent issues including the exercise of power within the decision-making process, identification of the decisionmakers, sources and sharing of information, governance and risk. A qualitative approach was also used to assess the stakeholders’ roles within the network so that their perceptions of key issues, such as power, could be analysed. Auckland, New Zealand, was chosen as the study site for this research. Auckland is a mature cruise destination which is experiencing significant growth of its cruise tourism sector. However, its cruise infrastructure requires improvements to accommodate bigger ships and more than two ships at a time. Therefore, proposals for its redevelopment are being considered. These proposals are being advanced against the backdrop of a contestable political environment and high profile competing interests. Respondents’ perceptions revealed a network which is neither outwardly identifiable as a network nor cohesive in its organisation. On the contrary, respondents described a network characterised by, for example, the asymmetric exercise of power, the presence of competing interests, a lack of transparency in the decision-making process and the absence of effective governance. They also articulated a wide range of risks which they believed could flow from this lack of cohesion, or fragmentation. Respondents’ perceptions supported recognition of Auckland’s cruise infrastructure development network as a policy issue network, given the network’s openness, instability and the unequal contribution of and control over resources. This research makes several original contributions. Firstly, it presents a conceptual analysis of stakeholder interrelationships and the power stakeholders exercise in relation to cruise infrastructure development. Secondly, it advances a novel framework for analysing power in relation to proposals for cruise infrastructure development. Thirdly, it analyses empirical evidence which conveys how stakeholders perceive the exercise of power within the stakeholder networks formed to advance proposals for cruise infrastructure development. Fourthly, it applies media discourse analysis to analyse the media discourse surrounding proposals for cruise infrastructure development. This approach enables key stakeholders and researchers to construct a nuanced analysis of the key issues as well as reconstruct a cohesive narrative based on media reports. Fifthly, it differentiates between the types of networks which can form to advance proposals for cruise infrastructure development. Applied, original contributions include analyses of the characteristics of stakeholder networks which form to advance proposals for cruise infrastructure development and of stakeholder perceptions of the exercise of power within these networks. This thesis also presents empirically informed insights into the potential for risk where such networks become fragmented. There are limitations to this research which should be recognised. Firstly, this study is based on a single case study. Secondly, a qualitative approach was used to allow for the detailed probing of stakeholders’ perceptions rather than a quantitative approach which can offer precision in describing the structure of the network. Thirdly, this research is based on an informal, open network and not one which has purposely been established. Fourthly, the number of respondents was limited by the small potential pool of respondents. Lastly, this research is limited to the proposal stage of cruise infrastructure development. Several opportunities for future research should be considered. A social network analysis (SNA) approach can be used to provide a more precise view of the contours of similar networks and provide a means for triangulating the qualitative approach taken in this research. While this research was focused on the proposal stage for (re)development in a mature cruise destination, further research could consider other stages of development. A longitudinal study could provide valuable evidence given the protracted time period which is usually associated with large public infrastructure development projects. Another avenue includes extending this research to the broader field of cruise tourism, as destination networks seek to build a sustainable cruise tourism sector.<br>Thesis (PhD Doctorate)<br>Doctor of Philosophy (PhD)<br>School of Natural Sciences<br>Science, Environment, Engineering and Technology<br>Full Text

<p>Denna avhandling handlar om hur befintliga datorinfrastrukturer i t.ex. sjukhus och industrier kan avlasta sensornätverk med energikrävande uppgifter. Vi har forskat på olika aspekter som gör det möjligt att förlänga livslängden på dessa sensornätverk. Avhandlingen presenterar en ny plattform för sensornätverk tillsammans med inledande simuleringar som påvisar att vår plattform ökar livslängden på dessa typer av nätverk.</p><p>Generella sensornätverk är uppbyggda av tätt grupperade, trådlösa, batteridrivna datorer som kan vara så små som en kubikmillimeter. Datorerna kallas för sensorer eller sensornoder eftersom de har en eller flera inbyggda sensorer som känner av sin omgivning. En sensor har till uppgift att samla information från sin omgivning, t.ex. temperatur, fuktighet, vibrationer, hjärtslag eller bilder. Sensorerna skickar sedan informationen till en insamlingsstation någonstans i nätverket.</p><p>I de typer av tillämpningar vi tittar på är det viktigt att minimera energiförbrukningen, så att man maximerar livslängden på sensornätverket. Avhandlingen presenterar en lösning där befintlig datorinfrastruktur fungerar som hjälpdatorer/avlastare till ett sensornätverk. Hjälpdatorerna, eller basstationerna som vi kallar dem i avhandlingen, hanterar energikrävande uppgifter som t.ex. vilken sensor som ska kommunicera med vem samt vid vilken tidpunkt etc. Då kan sensorerna i nätverket fokusera på att utföra sina egna uppgifter tills dess att basstationen säger att uppgifterna ändrats.</p><p>Simuleringar visar att vår plattform kan skicka upp till 97 % mera information till basstationen än en jämförbar plattform med samma energimängd. 88 % av våra sensorer är fortfarande vid liv när den andra plattformens sensorer förbrukat all sin energi.</p><p>Ett exempel på hur dessa typer av nätverk kan användas är att övervaka patienters hälsa och kondition i sjukhus eller sjukhem. Patienter behöver inte ha en fast sängplats där en viss typ av medicinskt övervakningsinstrument finns tillgänglig utan kan placeras där det finns en ledig sängplats. Via trådlös kommunikation skickar sensorerna sedan hälsoinformation som t.ex. hjärtfrekvens och blodtryck till en basstation som i sin tur skickar vidare till ett centralt övervakningsinstrument någonstans på sjukhuset. Övervakningsinstrumentet behandlar informationen och larmar personal med rätt kompetens vid behov. Larmet kan skickas till en mobiltelefon eller en liten handdator som personalen alltid bär med sig. Med larmet skickas även information om var patienten befinner sig och all nödvändig data för att personalen snabbt ska kunna ställa en första diagnos. På detta sätt kan man spara in på antalet specialbyggda sängplatser och slippa dyrbara installationer av medicintekniska utrustningar knutna till en sängplats.</p><br><p>Recent advancements in electronic design, such as low-power circuits, energy efficient wireless communication, and improved energy supply, has enabled the vision of wireless sensor networks to become a reality. Wireless sensor networks typically consist of hundreds up to thousands of collaborating low-cost, battery-driven and wireless sensor nodes with scarce resources. The wireless sensor nodes are typical small physical entities, and usually small as a matchbox but can in extreme cases be no larger than a cubic millimeter.</p><p>In this thesis we present an architecture called AROS that uses existing infrastructure to aid in the management of wireless sensor networks. As an example, the existing infrastructure could be situated in hospitals or industrial buildings. The existing infrastructure can aid in prolonging the lifetime of the wireless sensor network by having "unlimited'' energy, long range radio capacity, and high-speed computers. We enable prolonged lifetime by centralizing some of the energy consuming administrative functionality of wireless sensor networks.</p><p>We show, by simulations, that the AROS architecture is able to prolong the lifetime of the sensor nodes. AROS is compared to a well known cluster based architecture, LEACH. The comparisons show that AROS with static configuration performs at least as well as LEACH in small wireless sensor networks in the size 100x100m, and up to 97 % better in long distance wireless sensor networks in the size of 400x400m. We show that AROS still has got 88 % of its sensor nodes alive when LEACHs' network demises.</p><p>In our simulations we have also studied how dynamic network clustering in AROS, using a TDMA scheduler and non-mobile wireless sensor nodes, affects the amount of data received by a base station. We show that AROS is better than LEACH-C in collecting data to the base station with the same total amount of energy for long distance networks and that AROS performs as well or better than LEACH-C in small wireless sensor networks.</p>

A thesis submitted to the Faculty of Science and Agriculture in fulfilment of the Degree of Doctor of Philosophy in the Department of Computer Science at the University of Zululand, 2017<br>InfrastructureWireless Mesh Networks (I-WMNs) are increasingly used to provide network connectivity and Internet access to previously under-served areas in the developing world. It is common for some of these deployments to be battery-powered due to a lack of electrical infrastructure in the targeted areas. Thus, the energy-efficiency of these networks gains additional importance. Topology Control (TC) has been previously reported to improve the energy-efficiency and network performance of wireless ad-hoc networks, including I-WMNs. However,simulation-based studies have been relied upon to reach these conclusions and the study of TC prototypes applicable to I-WMNs has largely been limited to design issues. Thus, the study of the efficacy of TC prototypes as a mechanism for improving energy-fficiency and network performance remains an open issue. The thesis addresses this knowledge gap by studying the dynamic, run-time behaviours and the network topologies created by two standards-compatible TC prototypes. This study provides unique insight into how the prototypes consume computational resources, maintain network connectivity, produce cumulative transceiver power savings and affect the workings of the routing protocol being employed. This study also documents the topology instability caused by transceiver power oscillations produced by the PlainTC prototype. A context-based solution to reduce transceiver power oscillations and the subsequent topology instability is proposed. This solution applies the Principal Component Analysis statistical method to historical network data in order to derive the weights associated with each of the identified context variables. A threshold value is defined that only permits a node to adjust its transceiver power output if the observed change in a node’s context exceeds the threshold. The threshold mechanism is incorporated into the PlainTC+ prototype and is shown to reduce topology instability whilst improving network performance when compared to PlainTC.The results obtained in this study suggest that I-WMN topologies formed by TC are able to closely match the performance of networks that do not employ TC. However, this study shows that TC negatively affects the energy efficiency of the network despite achieving cumulative transceiver power savings.

This thesis proposes a novel working paradigm for transportation infrastructure asset management by viewing the transportation networks as key components (or nodes) of a broader network of resources, which includes infrastructure linked with societyâ s ecological, social, and economic systems. An extensive review of network science literature suggested that to understand the behavior of a complex network is imperative to characterize its topology. Consequently, this thesis focused on developing a framework to characterize the topology of the transportation infrastructure systems, and understanding how the unveiling topology can be used for supporting transportation asset management decisions. The proposed methodology determines whether the transportation infrastructure networks can be modeled as scale-free or exponential networks, using a framework for characterizing the agents of the network, their direct and indirect interactions among each other, and their importance as elements of a complex network, and utilizes these data to support transportation asset management. The methodology consist of seven steps: (1) define the networks of interest; (2) identify their intrinsic components; (3) visualize the identified networks using GIS maps; (4) identify direct and indirect interactions through superposition of the networks; (5) represent the relationship between the nodes and their linkages by frequency diagrams in order to determine the intrinsic topology of the network; (6) illustrate (graphically) the overall transportation infrastructure with the help of GIS; and (7) analyze the TINs from the decision-maker point of view, identifying the elements that are more relevant or need more attention on the network. The procedure is then implemented in a small network in a localized area (Town of Blacksburg, Virginia) to show its practicality, and recommendations for further development and mathematical modeling in order to allow its implementation in larger networks are provided. Based on frequency analysis of the nodes and their connectivity, it was concluded that the transportation infrastructure networks in the case study behave as exponential networks. The study showed that the links determine how the infrastructure network grows and that problems like congestion can be addressed by analyzing other factors related with topology, such as speed, unit size, and lane width. The proposed methodology was found to be useful as an asset management tool. Finally, a list of findings and recommendations for further research are presented as opportunities to enhance the management of transportation infrastructure networks.<br>Master of Science

ITC/USA 2012 Conference Proceedings / The Forty-Eighth Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2012 / Town and Country Resort & Convention Center, San Diego, California<br>The iNET program uses network technology and infrastructure to enhance traditional telemetry systems. The program's components were designed with an eye to existing and emerging technology and infrastructure, requiring the program to gather data about these systems. The methods used in this design effort can be used to characterize existing network infrastructure to determine what upgrades and changes are necessary to deploy a TmNS. This paper describes the methods used for characterizing a range network infrastructure and explores network capacity and policy issues effecting a TmNS deployment. This effort includes making estimates and taking measurements of network capacity, surveying and analyzing network routing/management policies, and proposes a system for evaluating networks for future TmNS deployments.

Thesis (M.S. in Information Technology Management) Naval Postgraduate School, June 1995.<br>Thesis advisor(s): Norman Schneidewind. "June 1995." Includes bibliographical references. Also available online.

Measurement collection is a primary step towards analyzing and optimizing performance of a telecommunication service. With an Mobile Broadband (MBB) network, the measurement process has not only to track the network's Quality of Service (QoS) features but also to asses a user's perspective about its service performance. The later requirement leads to "user-side measurements" which assist in discovery of performance issues that makes a user of a service unsatisfied and finally switch to another network. User-side measurements also serve as first-hand survey of the problem domain. In this thesis, we exhibit the potential in the measurements collected at network edge by considering two well-known approaches namely crowdsourced and distributed testbed-based measurements. Primary focus is on exploiting crowdsourced measurements while dealing with the challenges associated with it. These challenges consist of differences in sampling densities at different parts of the region, skewed and non-uniform measurement layouts, inaccuracy in sampling locations, differences in RSS readings due to device-diversity and other non-ideal measurement sampling characteristics. In presence of heterogeneous characteristics of the user-side measurements we propose how to accurately detect mobile coverage holes, to devise sample selection process so to generate a reliable radio map with reduced sample cost, and to identify cellular infrastructure at places where the information is not public. Finally, the thesis unveils potential of a distributed measurement test-bed in retrieving performance features from domains including user's context, service content and network features, and understanding impact from these features upon the MBB service at the application layer. By taking web-browsing as a case study, it further presents an objective web-browsing Quality of Experience (QoE) model.

Ce travail considère la sécurité de l'infrastructure multicast du point de vue de l'opérateur de réseau. Or, l'opérateur est essentiellement concerné par un problème de "continuité de service en toutes circonstances", même en le cas ou son réseau est victime d'une attaque. Dans cette thèse nous identifions les attaques possibles, nous les classons selon leurs impacts pour l'opérateur, et identifions divers mécanismes de sécurité pour y faire face. Cette étude révèle que l'infrastructure est fortement vulnérable aux attaques DoS consommanl les ressources de réseau, ce dernier devenant alors lent voir indisponible. Ces attaques sont faciles à lancer de la périphérie de réseau (intentionnellement ou non) en utilisant les protocoles de gestion de groupe IGMP/MLD. Notre étude révèle également les limites des approches proposées pour répondre à ces attaques. A la lumière de l'analyse détaillée de la problématique, des vulnérabilités, et des solutions actuelles, nous proposons une nouvelle approche pour aider le réseau de l'opérateur à se défendre contre les attaques basées sur IGMP ou MLD. Notre Proposition suit une approche pragmatique et flexible, qui garantit qu'elle sera facilement déployée dans les infrastructures existantes, et vise également à protéger les clients légitimes en cas d'attaque<br>Ln this thesis we adopt the security from the multicast Network Operator's viewpoint. The kind of security required by a network operator, who manages and operates the multicast routing infrastructure, largely differs from that of end-to-end security. More specifically, the operator is concerned by service continuity no matter what happens. While many theoretically ideal proposais have been done to secure the routing protocols, they have rarely been accepted by the operator community. For instance, because they require to modify existing and widely deployed protocols, or they introduce heavy authentication mechanisms, which is in practice almost impossible to deploy in legacy networks, and even infeasible, since a corrupted host may be the source of a DoS attack, even if it has been authenticated. Ln this thesis analyze in depth the threats to the multicast infrastructure. We show that the vulnerability of the multicast model comes largely from the edge. More specifically, several attacks arise from the use of group management protocols, IGMP for IPv4 and MLD for IPv6. Ln the light of this analysis, we introduce and evaluate a simple, yet efficient filtering approach to thwart some DoS attacks that are based on IGMP or MLD flooding, and that threaten the whole operator's infrastructure

More than a billion people access the Internet through residential broadband connections worldwide, and this number is projected to grow further. Surprisingly, little is known about some important properties of these networks: What performance do users obtain from their ISP? What factors affect performance of broadband networks? Are users bottlenecked by their ISP or by their home network? How are applications such as the Web affected by these factors? Answering these questions is difficult; there is tremendous diversity of technologies and applications in home and broadband networks. While a lot of research has tackled these questions piecemeal, the lack of a good vantage point to obtain good measurements from these networks makes it notably difficult to do a holistic characterization of the ﾓlast mileﾔ. In this dissertation we use the home gateway to characterize home and access networks and mitigate performance bottlenecks that are specific to such networks. The home gateway is uniquely situated; it is always on and, as the hub of the network, it can directly observe the home network, the access network, and user traffic. We present one such gateway- based platform, BISmark, that currently has nearly 200 active access points in over 20 countries. We do a holistic characterization of three important components of the last mile using the gateway as the vantage point: the access link that connects the user to the wider Internet, the home network to which devices connect, and Web performance, one of the most commonly used applications in today's Internet. We first describe the design, development, and deployment of the BISmark platform. BISmark uses custom gateways to enable measurements and evaluate performance opti- mizations directly from home networks. We characterize access link performance in the US using measurements from the gateway; we evaluate existing techniques and propose new techniques that help us understand these networks better. We show how access link technology and home networking hardware can affect performance. We then develop a new system that uses passive measurements at the gateway to localize bottlenecks to either the wireless network or the access link. We deploy this system in 64 homes worldwide and characterize the nature of bottlenecks, and the state of the wireless network in these homes - specifically we show how the wireless network is rarely the bottleneck as throughput exceeds 35 Mbits/s. Finally, we characterize bottlenecks that affect Web performance that are specific to the last mile. We show how latency in the last mile results in page load times stagnating at throughput exceeding 16 Mbits/s, and how simple techniques deployed at the gateway can mitigate these bottlenecks.

ITC/USA 2010 Conference Proceedings / The Forty-Sixth Annual International Telemetering Conference and Technical Exhibition / October 25-28, 2010 / Town and Country Resort & Convention Center, San Diego, California<br>Network switches are an integral part of most network-based data acquisition systems. Switches fall into the category of network infrastructure. They support the interconnection of nodes and the movement of data in the overall network. Unlike endpoints such as data acquisition units, recorders, and display modules, switches do not collect, store or process data. They are a necessary expense required to build the network. The goal of this paper is to show how a small integrated network switch can be used to maximize the value proposition of a given switch port in the network. This can be accomplished by maximizing the bandwidth utilization of individual network segments and minimizing the necessary wiring needed to connect all the network components.

L'informatique en nuage (Cloud Computing) a émergé comme un nouveau paradigme pour offrir des ressources informatiques à la demande et pour externaliser des infrastructures logicielles et matérielles. Le Cloud Computing est rapidement et fondamentalement en train de révolutionner la façon dont les services informatiques sont mis à disposition et gérés. Ces services peuvent être demandés à partir d’un ou plusieurs fournisseurs de Cloud d’où le besoin de la mise en réseau entre les composants des services informatiques distribués dans des emplacements géographiquement répartis. Les utilisateurs du Cloud veulent aussi déployer et instancier facilement leurs ressources entre les différentes plateformes hétérogènes de Cloud Computing. Les fournisseurs de Cloud assurent la mise à disposition des ressources de calcul sous forme des machines virtuelles à leurs utilisateurs. Par contre, ces clients veulent aussi la mise en réseau entre leurs ressources virtuelles. En plus, ils veulent non seulement contrôler et gérer leurs applications, mais aussi contrôler la connectivité réseau et déployer des fonctions et des services de réseaux complexes dans leurs infrastructures virtuelles dédiées. Les besoins des utilisateurs avaient évolué au-delà d'avoir une simple machine virtuelle à l'acquisition de ressources et de services virtuels complexes, flexibles, élastiques et intelligents. L'objectif de cette thèse est de permettre le placement et l’instanciation des ressources complexes dans des infrastructures de Cloud distribués tout en permettant aux utilisateurs le contrôle et la gestion de leurs ressources. En plus, notre objectif est d'assurer la convergence entre les services de cloud et de réseau. Pour atteindre cela, nous proposons des algorithmes de mapping d’infrastructures virtuelles dans les centres de données et dans le réseau tout en respectant les exigences des utilisateurs. Avec l'apparition du Cloud Computing, les réseaux traditionnels sont étendus et renforcés avec des réseaux logiciels reposant sur la virtualisation des ressources et des fonctions réseaux. En plus, le nouveau paradigme d'architecture réseau (Software Defined Networks) est particulièrement pertinent car il vise à offrir la programmation du réseau et à découpler, dans un équipement réseau, la partie plan de données de la partie plan de contrôle. Dans ce contexte, la première partie propose des algorithmes optimaux (exacts) et heuristiques de placement pour trouver le meilleur mapping entre les demandes des utilisateurs et les infrastructures sous-jacentes, tout en respectant les exigences exprimées dans les demandes. Cela inclut des contraintes de localisation permettant de placer une partie des ressources virtuelles dans le même nœud physique. Ces contraintes assurent aussi le placement des ressources dans des nœuds distincts. Les algorithmes proposés assurent le placement simultané des nœuds et des liens virtuels sur l’infrastructure physique. Nous avons proposé aussi un algorithme heuristique afin d’accélérer le temps de résolution et de réduire la complexité du problème. L'approche proposée se base sur la technique de décomposition des graphes et la technique de couplage des graphes bipartis. Dans la troisième partie, nous proposons un cadriciel open source (framework) permettant d’assurer la mise en réseau dynamique entre des ressources Cloud distribués et l’instanciation des fonctions réseau dans l’infrastructure virtuelle de l’utilisateur. Ce cadriciel permettra de déployer et d’activer les composants réseaux afin de mettre en place les demandes des utilisateurs. Cette solution se base sur un gestionnaire des ressources réseaux "Cloud Network Gateway Manager" et des passerelles logicielles permettant d’établir la connectivité dynamique et à la demande entre des ressources cloud et réseau. Le CNG-Manager offre le contrôle de la partie réseau et prend en charge le déploiement des fonctions réseau nécessaires dans l'infrastructure virtuelle des utilisateurs<br>Cloud computing emerged as a new paradigm for on-demand provisioning of IT resources and for infrastructure externalization and is rapidly and fundamentally revolutionizing the way IT is delivered and managed. The resulting incremental Cloud adoption is fostering to some extent cloud providers cooperation and increasing the needs of tenants and the complexity of their demands. Tenants need to network their distributed and geographically spread cloud resources and services. They also want to easily accomplish their deployments and instantiations across heterogeneous cloud platforms. Traditional cloud providers focus on compute resources provisioning and offer mostly virtual machines to tenants and cloud services consumers who actually expect full-fledged (complete) networking of their virtual and dedicated resources. They not only want to control and manage their applications but also control connectivity to easily deploy complex network functions and services in their dedicated virtual infrastructures. The needs of users are thus growing beyond the simple provisioning of virtual machines to the acquisition of complex, flexible, elastic and intelligent virtual resources and services. The goal of this thesis is to enable the provisioning and instantiation of this type of more complex resources while empowering tenants with control and management capabilities and to enable the convergence of cloud and network services. To reach these goals, the thesis proposes mapping algorithms for optimized in-data center and in-network resources hosting according to the tenants' virtual infrastructures requests. In parallel to the apparition of cloud services, traditional networks are being extended and enhanced with software networks relying on the virtualization of network resources and functions especially through network resources and functions virtualization. Software Defined Networks are especially relevant as they decouple network control and data forwarding and provide the needed network programmability and system and network management capabilities. In such a context, the first part proposes optimal (exact) and heuristic placement algorithms to find the best mapping between the tenants' requests and the hosting infrastructures while respecting the objectives expressed in the demands. This includes localization constraints to place some of the virtual resources and services in the same host and to distribute other resources in distinct hosts. The proposed algorithms achieve simultaneous node (host) and link (connection) mappings. A heuristic algorithm is proposed to address the poor scalability and high complexity of the exact solution(s). The heuristic scales much better and is several orders of magnitude more efficient in terms of convergence time towards near optimal and optimal solutions. This is achieved by reducing complexity of the mapping process using topological patterns to map virtual graph requests to physical graphs representing respectively the tenants' requests and the providers' physical infrastructures. The proposed approach relies on graph decomposition into topology patterns and bipartite graphs matching techniques. The third part propose an open source Cloud Networking framework to achieve cloud and network resources provisioning and instantiation in order to respectively host and activate the tenants' virtual resources and services. This framework enables and facilitates dynamic networking of distributed cloud services and applications. This solution relies on a Cloud Network Gateway Manager and gateways to establish dynamic connectivity between cloud and network resources. The CNG-Manager provides the application networking control and supports the deployment of the needed underlying network functions in the tenant desired infrastructure (or slice since the physical infrastructure is shared by multiple tenants with each tenant receiving a dedicated and isolated portion/share of the physical resources)

Thesis (Ph. D.)--Ohio State University, 2004.<br>Title from first page of PDF file. Document formatted into pages; contains xvii, 203 p. : ill. Advisor: Morton E. O'Kelly, Department of Geography. Includes bibliographical references (p. 199-203).

Botnets are a pervasive threat to the Internet and its inhabitants. A botnet is a collection of infected machines that receive commands from the botmaster, a person, group or nation- state, to perform malicious actions. Instead of “cleaning” individual infections, one can sever the method of communication between a botmaster and her zombies by attempting a botnet takedown, which contains the botnet and its malicious actions. Unfortunately, takedowns are currently performed without technical rigor nor are there automated and independent means to measure success or assist in performing them. This dissertation focuses on understanding the criminal infrastructure that enables communication between a botmaster and her zombies in order to measure attempts at, and to perform, successful takedowns. We show that by interrogating malware and performing large-scale analysis of passively collected network data, we can measure if a past botnet takedown was successful and use the same techniques to perform more comprehensive takedowns in the future.

Thesis (M.S.)--University of Missouri--Rolla, 2007.<br>Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed March 26, 2008) Includes bibliographical references (p. 83-84).