Policy-based management (PBM) is an adaptable security policy mechanism in information systems (IS) that confirm only authorised users can access resources. A few decades ago, the traditional PBM has focused on closed systems, where enforcement mechanisms are trusted by system administrators who define access control policies. Most of current work on the PBM systems focuses on designing a centralised policy decision point (PDP), the component that evaluates an access request against a policy and reports the decision back, which can have performance and resilience drawbacks. Performance and resilience are a major concern for applications in military, health and national security domains where the performance is desirable to increase situational awareness through collaboration and to decrease the length of the decision making cycle. The centralised PDP also represents a single point of failure. In case of the failure of the centralised PDP, all resources in the system may cease to function. The efficient distribution of enforcement mechanisms is therefore key in building large scale policy managed distributed systems. Moving from the traditional PBM systems to dynamic PBM systems supports dynamic adaptability of behaviour by changing policy without recoding or stopping the system. The SANTA history-based dynamic PBM system has a formal underpinning in Interval Temporal Logic (ITL) allowing for formal analysis and verification to take place. The main aim of the research to automatically distribute enforcement mechanisms in the distributed system in order to provide resilience against network failure whilst preserving efficiency of policy decision making. The policy formalisation is based on SANTA policy model to provide a high level of assurance. The contribution of this work addresses the challenge of performance, manageability and security, by designing a Decentralised PBM framework and a corresponding Distributed Enforcements Architecture (DENAR). The ability of enforcing static and dynamic security policies in DENAR is the prime research issue, which balances the desire to distribute systems for flexibility whilst maintaining sufficient security over operations. Our research developed mechanisms to improve the efficiency of the enforcement of security policy mechanisms and their resilience against network failures in distributed information systems.

En la actualidad se están realizando diversos esfuerzos para realizar la visión fu-turista de las redes de telecomunicación autogestionadas. La gestión basada en políticas ha sido reconocida como una herramienta potencial para habilitar esta visión. Mayorita-riamente, ésta técnica ha sido reconocida como proveedora de flexibilidad, adaptabilidad y soporte para asignar recursos, controlar Calidad de Servicio y seguridad, de una manera automática y de acuerdo a reglas administrativas. Adicionalmente, se ha considerado que la gestión basada en políticas proveería tal flexibilidad en tiempo de ejecución y como resultado de cambios en la red, interacciones entre usuarios, aplicaciones y disponibilidad de recursos. A pesar de enormes esfuerzos realizados con lenguajes de especificación de políticas, arquitecturas de gestión en diversos dominios y estandarización, la gestión ba-sada en políticas aún no es una realidad. Una de las razones para la reticencia en su utili-zación es la dificultad para analizar políticas que garanticen estabilidad en el sistema. Además de la problemática asociada a la gestión de conflictos entre políticas, otro obstá-culo para su utilización es la dificultad de derivar políticas ejecutables alineadas a objeti-vos administrativos o a otras políticas de alto nivel. Este último es el problema del refi namiento de políticas.Esta Tesis aborda el problema crítico de refinamiento de políticas. Damos una vi-sión completa del proceso de refinamiento, desde el análisis formal hasta su realización práctica, identificando los elementos que intervienen en cada paso de tal proceso. Inicialmente, proponemos un marco de trabajo para refinamiento de políticas ba-sado en Lógica Lineal Temporal, una lógica estándar que permite el análisis en sistemas reactivos. Esta técnica es utilizada para representar políticas a diferentes niveles jerár-quicos de abstracción. Acto seguido desarrollamos mecanismos que habilitan la obten-ción de políticas ejecutables a partir de ciertos requerimientos mediante la utilización de técnicas de exploración de estados basados en Lógica Lineal Temporal. Adicionalmente, aclaramos e identificamos las actividades y tareas de gestión de las partes administrativas durante el ciclo de vida de un sistema de gestión basado en políticas, desde la perspectiva del proceso de refinamiento de políticas. Esta Tesis presenta también directrices para abordar el proceso de refinamiento de políticas en contextos de gestión de red. Damos un paso adelante en la materialización de este proceso mediante la utilización de propiedades estructurales inherentes a sistemas de gestión de red. Proveemos, en fin, una metodología para aplicar los conceptos introduci-dos en el marco de trabajo desarrollado en esta Tesis en sistemas de gestión de red. En esta Tesis también realizamos un proceso de refinamiento de políticas com-pleto. Detallamos la realización de tal proceso en una solución exitosa de gestión basada en políticas. Tomando como base el dominio de Gestión de Calidad de Servicio, aclara-mos y presentamos las implicaciones del problema de refinamiento en este dominio de aplicación. / Current research efforts are being directed to commit with the long-term view of self management properties for telecommunications networks. One of the key approaches that have been recognised as an enabler of such a view is policy-based management. Pol-icy-based management has been mostly acknowledged as a methodology that provides flexibility, adaptability and support to automatically assign network resources, control Quality of Service and security, by considering administratively specified rules. The hype of policy-based management was to commit with these features in run-time as a result of changeable network conditions resulting from the interactions of users, applications and existing resources. Despite enormous efforts with policy languages, management archi-tectures using policy in different application domains, standardisation and industrial ef-forts, policy-based management is still not a reality. One reason behind the reticence for its use is the difficulty to analyse policies that guarantee configuration stability. In addi-tion to policy conflict analysis, a key issue for this reticence is the need to derive en-forceable policies from high level administrative goals or from higher level policies, namely the policy refinement process.This Thesis deals with the critical nature of addressing the policy refinement problem. We provide a holistic view of this process, from formal analysis to its practical realisation, identifying the key elements involved in each step of such critical process. We initially propose a policy refinement framework relying on Linear Temporal Logic (LTL), a standard logic that allows analysis of reactive systems. Based on the for-mer logic, we lay down the process of representing policies at different levels of abstrac-tion. Following on with this, we develop the mechanisms that enable the abstraction of enforceable policies from hierarchical requirements in a fully automatic manner, making use of Linear Temporal Logic based state exploration techniques. In addition, we clarify and identify the activities and management tasks that the administrative parties should carry out during the life cycle of the policy-based management system, from the perspec tive of the policy refinement process.This Thesis provides the guidelines to address policy refinement in network management contexts. Concretely, we take one step ahead in the materialisation of the policy refinement process by exploiting inherent containment properties of network management systems. For this purpose we provide the methodology to apply the concepts introduced in the policy refinement framework developed in this Thesis in the above context.In this Thesis we also execute a complete and rather detailed policy refinement process for a successful policy-based management solution. Taking the intra-domain Quality of Service Management application domain as background, we clarify and pre-sent the implications of the policy refinement problem in such a concrete application do-main.

Pervasive (ubiquitous) computing is a new paradigm where the computers are submerged into the background of the everyday life. One important aspect of pervasive systems is context-awareness. Context-aware systems are those that can adapt their behaviours according to the current context. Context-aware applications are being integrated into our everyday activity aspects such as: health care, smart homes and transportations. There exist a wide range of context-aware applications such as: mobile phones, learning systems, smart vehicles. Some context-aware systems are critical since the consequence of failing to identify a given context may be catastrophic. For example, an auto-pilot system is a critical context-aware system; it senses the humidity, clouds, wind speed and accordingly adjusts the altitude, throttle and other parameters. Being a critical context-aware system has to be provably correct. Policy-based approaches has been used in many applications but not in context-aware systems. In this research, we want to discover the anatomy (i.e. architecture, structure and operational behaviour) of policy-based management as applied to context-aware systems, and how policies are managed within such a dynamic system. We propose a novel computational model and its formalisation is presented using the Calculus of Context-aware Ambients (CCA). CCA has been proposed as a suitable mathematical notation to model mobile and context-aware systems. We decided to use CCA due to three reasons: (i) in CCA, mobility and context-awareness are primitive constructs and are treated as first-class citizens; (ii) properties of a system can be formally analysed; (iii) CCA specifications are executable, and thus, leading to rapid prototyping and early validation of the system properties. We, then show how policies can be expressed in CCA. For illustration, the specification of the event-condition-action (ECA) conceptual policy model is modelled in CCA in a natural fashion. We also propose a policy-based architecture for context-aware systems, showing its different components, and how they interact. Furthermore, we give the specification of the policy enforcement mechanism used in our proposed architecture in CCA. To evaluate our approach, a real-world case study of an infostation-based mobile learning (mLearning) system is chosen. This mLearning system is deployed across a university campus to enable mobile users to access mobile services (mServices) represented by course materials (lectures, tests and tutorials) and communication services (intelligent message notification and VoIP). Users can access the mServices through their mobile devices (Hand-set phones, PDAs and laptops) regardless of their device type or location within a university campus. We have specified the mLearning system in CCA (i.e. specification based on policies of the mServices), afterwards, the specification is simulated using the CCA interpreter tool. We have developed an animation tool specially designed for the mLearning system. The animation tool provides graphical representation of the CCA processes. In terms of safety and liveness, some important properties of the mLearning system have been validated as a proof of concept.

Les expectatives dels usuaris en relació a la quantitat i qualitat del serveis de xarxa estan creixent ràpidament. En canvi, desenvolupar e implantar nous serveis de xarxa (serveis que operen a nivell de xarxa) seguint el procés d'estandardització és massa lent i no pot satisfà les expectatives.Les xarxes actives i programables van ser proposades per acomodar la ràpida evolució de noves tecnologies i accelerar la implantació de serveis sofisticats. Les xarxes actives permeten que tercers (usuaris finals, operadors i proveïdors de servei) introdueixin serveis específics per aplicacions (en forma de codi) dins la xarxa. D'aquesta manera, les aplicacions poden fer servir aquests serveis per obtenir el suport necessari de la xarxa en termes de comportament per exemple.Tanmateix, les tecnologies de xarxes actives i programables introdueixen una complexitat addicional als elements de xarxa que ha de ser tractada pel sistema de gestió. Alguns exemples d'aquesta complexitat addicional són la necessitat de suportar nous serveis introduïts dinàmicament a la xarxa o la gestió de xarxes actives virtuals. Aquestes xarxes poden ser creades dins una infrastructura de xarxa programable per satisfer les creixents necessitats de control i particularització que els clients imposen a les xarxes. A més, la probable implantació progressiva de les xarxes actives i programables dins les xarxes IP actuals afegeix un altre requisit important al pla de gestió: aquest ha de ser capaç de suportar tecnologies de xarxa heterogènies (passives, actives i programables).La solució proposada en aquesta tesi millora els sistemes de gestió basats en polítiques amb conceptes de les tecnologies de xarxes actives i programables per satisfer tots els requisits abans esmentats; assolint, d'aquesta manera, una solució sòlida per la gestió de xarxes actives i programables.Finalment, l'arquitectura per la gestió de xarxes actives basada en polítiques (MANBoP) que proposem ha estat dissenyada per poder ser instanciada a qualsevol nivell de gestió (xarxa, sub-xarxa o element). A més, diferents instàncies es poden agrupar fàcilment per crear una infrastructura de gestió. Per exemple, una instància MANBoP de nivell de xarxa pot treballar sobre instàncies de nivell de element, o vàries instàncies de nivell de sub-xarxa poden ser creades per treballar en paral·lel, cadascuna gestionant una regió geogràfica de la xarxa diferent. L'objectiu d'aquest atribut de l'arquitectura és facilitar la tasca de creació d'una infrastructura de gestió. D'aquesta manera, els operadors de xarxa poden crear la infrastructura de gestió que més els convingui segons els seus objectius de negoci i reduir així els costs de gestió. / -RESUMENLas expectativas de los usuarios en relación con la cantidad y calidad de los servicios de red están creciendo rápidamente. En cambio, desarrollar e implantar nuevos servicios de red (servicios que operan al nivel de red) siguiendo los procesos de estandarización es demasiado lento y no colma las expectativas.Las redes activas y programables fueron propuestas para acomodar la rápida evolución de las nuevas tecnologías y acelerar la implantación de nuevos servicios más sofisticados. Las redes activas permiten que terceros (usuarios finales, operadores o proveedores de servicio) introduzcan servicios específicos para aplicaciones (en forma de código) dentro de la red. De esta forma, las aplicaciones pueden utilizar estos servicios para obtener el soporta que necesitan de la red en términos, por ejemplo, de comportamiento.Sin embargo, las tecnologías de redes activas y programables introducen una complejidad adicional en los elementos de red que debe ser tratada por el sistema de gestión. Algunos ejemplos de esta complejidad adicional son la necesidad de soportar nuevos servicios introducidos dinámicamente en la red o la gestión de redes activas virtuales. Éstas pueden ser creadas dentro de una infraestructura de red programable para satisfacer las necesidades crecientes de control y particularización que los clientes imponen sobre las redes. Además, la probable progresiva implantación de la redes activas y programables en la redes IP actuales añade otro importante requisito al plano de gestión: éste tiene que ser capaz de soportar tecnologías de red heterogéneas (pasivas, activas y programables).La solución propuesta en esta tesis mejora los sistemas de gestión basados en políticas con conceptos de las tecnologías de redes activas y programables para satisfacer todos los requisitos enumerados anteriormente, consiguiendo, de esta forma, una solución sólida para la gestión de redes activas y programables.Finalmente, la arquitectura de gestión de redes activas basada en políticas (MANBoP) que proponemos ha sido diseñada para poder ser instanciada en cualquier nivel de gestión (red, sub-red o elemento). Además, diferentes instancias pueden ser agrupadas fácilmente para crear una infraestructura de gestión. Por ejemplo, una instancia MANBoP de nivel de red puede trabajar sobre instancias de nivel de elemento, o varias instancias de nivel de sub-red pueden ser creadas para trabajar en paralelo sobre diferentes regiones geográficas de la red. El objetivo de esta característica de la arquitectura es facilitar la creación de una infraestructura de gestión para que los operadores de red puedan crear la que más les convenga según sus objetivos de negocio, reduciendo así los costes de gestión. / User expectations of the range and quality of network services are growing rapidly. However, developing and deploying new network services (i.e. services that operate on the network layer), through best practice and standardization, is too slow and cannot match the steps of expectations. Active and programmable networks were proposed to accommodate the rapid evolution of new technologies and accelerate the deployment of new sophisticated services. Active networks (AN) enable third parties (end users, operators, and service providers) to inject application-specific services (in the form of code) into the network. Applications are thus able to utilize these services to obtain required network support in terms of, e.g. performance; that is, applications are now becoming network-aware. Nonetheless, active and programmable networking technologies introduce additional complexity in network elements that must be handled by the management architecture. Examples of this additional complexity are the need of coping with new services dynamically introduced in the network, or the management of virtual active networks (VANs). VANs might be created over a programmable network infrastructure to satisfy increasing requirements for the control and customization of resources that customers impose on networks. Furthermore, the likely progressive deployment of active and programmable routers in today's IP networks introduces another important requirement in the management plane; that is, it has to be able to cope with heterogeneous network technologies, i.e., passive, active and programmable.The solution proposed in this thesis enhances a policy-based management system with active networking technology concepts to fulfill the above-mentioned requirements, thus achieving a sound solution for the management of active and programmable networks.In addition, the Management of Active Networks Based on Policies (MANBoP) framework proposed is designed to be instantiated at any management level (i.e. network, sub-network or element). Moreover, different instances can be easily set up jointly to create a management infrastructure, e.g., a network-level MANBoP instance can be set up over element-level instances, or several subnetwork-level instances can work in parallel each one managing a different geographical region of the network, etc. The aim of this framework property is to ease the management infrastructure creation task, thus allowing network operators to adapt the management infrastructure to their business needs, resulting in a reduction of management costs.

The aim of this thesis is to design and implement a new Grid Resource Management methodology, where non-massive resources owners would be able to share their resources and integrate human collaboration across multiple domains regardless of network technology, operative platform or administrative domain.This thesis proposes a distributed and heuristic policy-based resource management architecture for large-scale Grids. The resource management architecture proposed herein is composed of four main building blocs: services management, resource discovery and monitoring, resource scheduling and jobs allocation and activation. The Grid Services Management (GSM) and Jobs Allocation and Activation (JAA) are supported by means of a Policy-based Grid Resource Management Architecture (PbGRMA). This architecture is able to identify service needs arising from diverse sources during the deployment and management of Grid Services, such as requirements demanded by customers, applications and network conditions. Afterwards, the PbGRMA merges these requirements into deployment policies for the corresponding Grid Services. The Grid Resource Discovery and Monitoring (GRDM) is supported by the introduction of the SNMP-based Balanced Load Monitoring Agents for Resource Scheduling (SBLOMARS), in which network and computational resources are monitored by distributed agents. This allows for a flexible, heterogeneous and scalable monitoring system. The Grid Resource Scheduling (GRS) is based on the Balanced Load Multi-Constrained Resource Scheduler (BLOMERS). This heuristic scheduler represents an alternate way of solving the inherent NP-hard problem for resource scheduling in large-scale distributed networks by means of the implementation of a Genetic Algorithm.Finally, based on the outcome of both the GRDM and GRS, the PbGRMA allocates the corresponding Grid Services by means of its interfaces with Globus ToolKit Middleware and Unix-based CLI commands along of any large-scale Grid Infrastructure. The synergy obtained by these components allows Grid administrators to exploit the available resources with predetermined levels of Quality of Service (QoS), reducing computational costs and makespan in resource scheduling while ensuring that the resource load is balanced throughout the Grid. The makespan of a schedule is the time required for all jobs to be processed when no one job could be interrupted during its execution and each node can perform at most one operation at any time.This new approach has been successfully tested in a real large-scale scenario such as Grid5000. The results presented along this Thesis show that our general solution is a reliable, flexible and scalable architecture to deploy and manage Grid Services in large-scale Grid Infrastructures. Moreover, the substitution of the heuristic algorithm approach used into the Grid Resource Scheduling (GRS) phase by other non-heuristics selection algorithms could make our solution useful in smaller Grid Infrastructures.

Redes definidas por software (Software-Defined Networking – SDN) tem como objetivo fornecer uma arquitetura mais sofisticada e precisa para gerenciar e monitorar o tráfego da rede. SDN permite centralizar parte da lógica de tomada de decisão sobre o processamento de fluxo e roteamento de pacotes em dispositivos chamados controladores. Apesar disso, o comportamento dos dispositivos de rede e suas configurações são muitas vezes escritos para situações específicas diretamente no controlador. Isto torna-se um problema quando há um aumento no número de elementos, ligações e serviços de rede, resultando numa grande quantidade de regras e uma elevada sobrecarga relacionada à configuração da rede. Como alternativa , técnicas, tais como gerenciamento baseado em políticas (Policy-Based Management – PBM) e refinamento de políticas podem ser utilizadas por operadores de alto nível para escrever Acordos de Nível de Serviço (Service Level Agreements – SLAs) em uma interface amigável, sem a necessidade de alterar o código implementado nos controladores. No entanto, o refinamento de políticas na nova área de pesquisa SDN tem sido um tema negligenciado, em parte, porque o refinamento não é um processo trivial. Ao utilizar SLAs, a sua tradução para políticas de baixo nível, por exemplo, regras para a configuração de elementos de comutação, não é simples. Se essa tradução não for realizada corretamente, os elementos do sistema podem não ser capaz de cumprir os requisitos implícitos especificados no SLA. Neste contexto, este trabalho apresenta ARKHAM: um avançado conjunto de ferramentas de refinamento para manipulação de acordos de nível de serviço em redes definidas por software. Este conjunto de ferramentas é composto por (i) um framework para criação de políticas que usa raciocínio lógico para a especificação de objetivos de nível de negócio e automatização de seu refinamento; (ii) um controlador OpenFlow que realiza a coleta de informações e implantação de configurações na rede; e (iii) uma representação formal de políticas de alto nível utilizando Event Calculus e aplicando raciocínio lógico para modelar tanto o comportamento do sistema quanto o processo de refinamento de políticas para o gerenciamento de SDN. Como resultado, a abordagem é capaz de identificar as necessidades e os recursos que precisam ser configurados de acordo com o refinamento do SLA, podendo assim configurar e executar com sucesso ações dinâmicas de suporte à reconfiguração de infraestrutura. / Software-Defined Networking (SDN) aims to provide a more sophisticated and accurate architecture for managing and monitoring network traffic. SDN permits centralizing part of the decision-making logic regarding flow processing and packet routing in controller devices. Despite this, the behavior of network devices and their configurations are often written for specific situations directly in the controller. This becomes an issue when there is an increase in the number of network elements, links, and services, resulting in a large amount of rules and a high overhead related to network configuration. As an alternative, techniques such as Policy- Based Management (PBM) and policy refinement can be used by high-level operators to write Service Level Agreements (SLAs) in a user-friendly interface without the need to change the code implemented in the controllers. However, policy refinement in the new research area of SDN has been a neglected topic, in part, because refinement is a nontrivial process. When using SLAs, their translation to low-level policies, e.g., rules for configuring switching elements, is not straightforward. If this translation is not performed properly, the system elements may not be able to meet the implicit requirements specified in the SLA. In this context, we introduce ARKHAM: an Advanced Refinement Toolkit for Handling Service Level Agreements in Software-Defined Networking. This work presents (i) a Policy Authoring Framework that uses logical reasoning for the specification of business-level goals and to automate their refinement; (ii) an OpenFlow controller which performs information gathering and configuration deployment; and (iii) a formal representation using event calculus that describes our solution. As a result, our approach is capable of identifying the requirements and resources that need to be configured in accordance with SLA refinement, and can successfully configure and execute dynamic actions for supporting infrastructure reconfiguration.

Redes definidas por software (Software-Defined Networking – SDN) tem como objetivo fornecer uma arquitetura mais sofisticada e precisa para gerenciar e monitorar o tráfego da rede. SDN permite centralizar parte da lógica de tomada de decisão sobre o processamento de fluxo e roteamento de pacotes em dispositivos chamados controladores. Apesar disso, o comportamento dos dispositivos de rede e suas configurações são muitas vezes escritos para situações específicas diretamente no controlador. Isto torna-se um problema quando há um aumento no número de elementos, ligações e serviços de rede, resultando numa grande quantidade de regras e uma elevada sobrecarga relacionada à configuração da rede. Como alternativa , técnicas, tais como gerenciamento baseado em políticas (Policy-Based Management – PBM) e refinamento de políticas podem ser utilizadas por operadores de alto nível para escrever Acordos de Nível de Serviço (Service Level Agreements – SLAs) em uma interface amigável, sem a necessidade de alterar o código implementado nos controladores. No entanto, o refinamento de políticas na nova área de pesquisa SDN tem sido um tema negligenciado, em parte, porque o refinamento não é um processo trivial. Ao utilizar SLAs, a sua tradução para políticas de baixo nível, por exemplo, regras para a configuração de elementos de comutação, não é simples. Se essa tradução não for realizada corretamente, os elementos do sistema podem não ser capaz de cumprir os requisitos implícitos especificados no SLA. Neste contexto, este trabalho apresenta ARKHAM: um avançado conjunto de ferramentas de refinamento para manipulação de acordos de nível de serviço em redes definidas por software. Este conjunto de ferramentas é composto por (i) um framework para criação de políticas que usa raciocínio lógico para a especificação de objetivos de nível de negócio e automatização de seu refinamento; (ii) um controlador OpenFlow que realiza a coleta de informações e implantação de configurações na rede; e (iii) uma representação formal de políticas de alto nível utilizando Event Calculus e aplicando raciocínio lógico para modelar tanto o comportamento do sistema quanto o processo de refinamento de políticas para o gerenciamento de SDN. Como resultado, a abordagem é capaz de identificar as necessidades e os recursos que precisam ser configurados de acordo com o refinamento do SLA, podendo assim configurar e executar com sucesso ações dinâmicas de suporte à reconfiguração de infraestrutura. / Software-Defined Networking (SDN) aims to provide a more sophisticated and accurate architecture for managing and monitoring network traffic. SDN permits centralizing part of the decision-making logic regarding flow processing and packet routing in controller devices. Despite this, the behavior of network devices and their configurations are often written for specific situations directly in the controller. This becomes an issue when there is an increase in the number of network elements, links, and services, resulting in a large amount of rules and a high overhead related to network configuration. As an alternative, techniques such as Policy- Based Management (PBM) and policy refinement can be used by high-level operators to write Service Level Agreements (SLAs) in a user-friendly interface without the need to change the code implemented in the controllers. However, policy refinement in the new research area of SDN has been a neglected topic, in part, because refinement is a nontrivial process. When using SLAs, their translation to low-level policies, e.g., rules for configuring switching elements, is not straightforward. If this translation is not performed properly, the system elements may not be able to meet the implicit requirements specified in the SLA. In this context, we introduce ARKHAM: an Advanced Refinement Toolkit for Handling Service Level Agreements in Software-Defined Networking. This work presents (i) a Policy Authoring Framework that uses logical reasoning for the specification of business-level goals and to automate their refinement; (ii) an OpenFlow controller which performs information gathering and configuration deployment; and (iii) a formal representation using event calculus that describes our solution. As a result, our approach is capable of identifying the requirements and resources that need to be configured in accordance with SLA refinement, and can successfully configure and execute dynamic actions for supporting infrastructure reconfiguration.

Redes definidas por software (Software-Defined Networking – SDN) tem como objetivo fornecer uma arquitetura mais sofisticada e precisa para gerenciar e monitorar o tráfego da rede. SDN permite centralizar parte da lógica de tomada de decisão sobre o processamento de fluxo e roteamento de pacotes em dispositivos chamados controladores. Apesar disso, o comportamento dos dispositivos de rede e suas configurações são muitas vezes escritos para situações específicas diretamente no controlador. Isto torna-se um problema quando há um aumento no número de elementos, ligações e serviços de rede, resultando numa grande quantidade de regras e uma elevada sobrecarga relacionada à configuração da rede. Como alternativa , técnicas, tais como gerenciamento baseado em políticas (Policy-Based Management – PBM) e refinamento de políticas podem ser utilizadas por operadores de alto nível para escrever Acordos de Nível de Serviço (Service Level Agreements – SLAs) em uma interface amigável, sem a necessidade de alterar o código implementado nos controladores. No entanto, o refinamento de políticas na nova área de pesquisa SDN tem sido um tema negligenciado, em parte, porque o refinamento não é um processo trivial. Ao utilizar SLAs, a sua tradução para políticas de baixo nível, por exemplo, regras para a configuração de elementos de comutação, não é simples. Se essa tradução não for realizada corretamente, os elementos do sistema podem não ser capaz de cumprir os requisitos implícitos especificados no SLA. Neste contexto, este trabalho apresenta ARKHAM: um avançado conjunto de ferramentas de refinamento para manipulação de acordos de nível de serviço em redes definidas por software. Este conjunto de ferramentas é composto por (i) um framework para criação de políticas que usa raciocínio lógico para a especificação de objetivos de nível de negócio e automatização de seu refinamento; (ii) um controlador OpenFlow que realiza a coleta de informações e implantação de configurações na rede; e (iii) uma representação formal de políticas de alto nível utilizando Event Calculus e aplicando raciocínio lógico para modelar tanto o comportamento do sistema quanto o processo de refinamento de políticas para o gerenciamento de SDN. Como resultado, a abordagem é capaz de identificar as necessidades e os recursos que precisam ser configurados de acordo com o refinamento do SLA, podendo assim configurar e executar com sucesso ações dinâmicas de suporte à reconfiguração de infraestrutura. / Software-Defined Networking (SDN) aims to provide a more sophisticated and accurate architecture for managing and monitoring network traffic. SDN permits centralizing part of the decision-making logic regarding flow processing and packet routing in controller devices. Despite this, the behavior of network devices and their configurations are often written for specific situations directly in the controller. This becomes an issue when there is an increase in the number of network elements, links, and services, resulting in a large amount of rules and a high overhead related to network configuration. As an alternative, techniques such as Policy- Based Management (PBM) and policy refinement can be used by high-level operators to write Service Level Agreements (SLAs) in a user-friendly interface without the need to change the code implemented in the controllers. However, policy refinement in the new research area of SDN has been a neglected topic, in part, because refinement is a nontrivial process. When using SLAs, their translation to low-level policies, e.g., rules for configuring switching elements, is not straightforward. If this translation is not performed properly, the system elements may not be able to meet the implicit requirements specified in the SLA. In this context, we introduce ARKHAM: an Advanced Refinement Toolkit for Handling Service Level Agreements in Software-Defined Networking. This work presents (i) a Policy Authoring Framework that uses logical reasoning for the specification of business-level goals and to automate their refinement; (ii) an OpenFlow controller which performs information gathering and configuration deployment; and (iii) a formal representation using event calculus that describes our solution. As a result, our approach is capable of identifying the requirements and resources that need to be configured in accordance with SLA refinement, and can successfully configure and execute dynamic actions for supporting infrastructure reconfiguration.

Cloud Computing has changed how computing is done as applications and services are being consumed from the cloud. It has attracted a lot of attention in recent times due to the opportunities it offers. While Cloud Computing is economical, the security challenges it poses are quite significant and this has affected the adoption rate of the technology. With the potential vulnerabilities being introduced by moving data to the cloud, it has become imperative for cloud service providers to guarantee the security of information, leaving cloud service consumers (e.g., enterprises) with the task of negotiating the terms and conditions of services provided by the cloud service providers as well as trusting them with their data. Although various security solutions used for addressing the security of data within the enterprises are now being applied to the cloud, these security solutions are challenged due to the dynamic, distributed and complex nature of the cloud technology. This thesis proposes a novel Policy-Based Management (PBM) framework capable of achieving cross-tenant authorization, handling dynamic and anonymous users while reducing the security management task to address cloud security. The framework includes an access control model adapted to the cloud environment that adopts features from role-based, task-based and attribute-based access control frameworks for a fine-grained access control. We demonstrate how this framework can be applied to develop an access control system for an enterprise using cloud services. The framework verifies the correctness of access control policies for cloud security through reasoning technique.

Student mobility in the area of Higher Education (HE) is gaining more attention nowadays. It is one of the cornerstones of the Bologna Process being promoted at both national and international levels. However, currently there is no technical system that would support student mobility processes and assist users in authoring educational curricula involving student mobility. In this study, the problem of student mobility programmes generation based on existing modules and programmes is considered. A similar problem is being solved in an Intelligent Tutoring Systems field using Curriculum generation techniques, but the student mobility area has a set of characteristics limiting their application to the considered problem. One of main limiting factors is that mobility programmes should be developed in an environment with heterogeneous regulations. In this environment, various established routines and regulations are used to control different aspects of the educational process. These regulations can be different in different domains and are supported by different authors independently. In this thesis, a novel framework was developed for generation of student mobility programmes in an environment with heterogeneous regulations. Two core technologies that were coherently combined in the framework are hierarchical planning and policy-based management. The policy-based planner was designed as a central engine for the framework. It extends the functionality of existing planning technologies and provides the means to carry out planning in environments with heterogeneous regulations, specified as policies. The policy-based planner enforces the policies during the planning and guarantees that the resultant plan is conformant with all policies applicable to it. The policies can be supported by different authors independently. Using them, policy authors can specify additional constraints on the execution of planning actions and extend the pre-specified task networks. Policies are enforced during the planning in a coordinated manner: situations when a policy can be enforced are defined by its scope, and the outcomes of policy evaluation are processed according to the specially defined procedures. For solving the problem of student mobility programme generation using the policy-based planner, the planning environment describing the student mobility problem area was designed and this problem was formalised as a planning task. Educational processes valid throughout the HE environment were formalised using Hierarchical Task Network planning constructs. Different mobility schemas were encoded as decomposition methods that can be combined to construct complex mobility scenarios satisfying the user requirements. New mobility programmes are developed as detailed educational processes carried out when students study according to these programmes. This provides the means to model their execution in the planning environment and guarantee that all relevant requirements are checked. The postponed policy enforcement mechanism was developed as an extension of the policy-based planner in order to improve the planning performance. In this mechanism, future dead-ends can be detected earlier during the planning using partial policy requests. The partial policy requests and an algorithm for their evaluation were introduced to examine policies for planning actions that should be executed in the future course of planning. The postponed policy enforcement mechanism was applied to the mobility programme generation problem within the descending policy evaluation technique. This technique was designed to optimise the process of programme components selection. Using it, policies for different domains can be evaluated independently in a descending order, gradually limiting the scope for the required component selection. The prototype of student mobility programme generation solution was developed. Two case studies were used to examine the process of student mobility programmes development and to analyse the role of policies in this process. Additionally, four series of experiments were carried out to analyse performance gains of the descending policy evaluation technique in planning environments with different characteristics.