Extensões na arquitetura SDN para o provisionamento de QoS através do monitoramento e uso de múltiplos caminhos

The substantial increase in the number of applications offered through the computer networks, as well as in the volume of traffic forwarded through the network, have hampered to assure adequate service level to users. The Quality of Service (QoS) offer, honoring specified parameters in Service Level Agreements (SLA), established between the service providers and their clients, composes a traditional and extensive computer networks’ research area. Several schemes proposals for the provision of QoS were presented in the last three decades, but the acting scope of these proposals is always limited due to some factors, including the limited development of the network hardware and software, generally belonging to a single manufacturer. The advent of Software Defined Networking (SDN), along with the maturation of its main materialization, the OpenFlow protocol, allowed the decoupling between network hardware and software, through an architecture which provides a control plane and a data plane. This eases the computer networks scenario, allowing that new abstractions are applied in the hardware composing the data plane, through the development of new software pieces which are executed in the control plane. This dissertation investigates the QoS offer through the use and extension of the SDN architecture. Based on the proposal of two new modules, one to perform the data plane monitoring, SDNMon, and the second, MP-ROUTING, developed to determine the use of multiple paths in the forwarding of data referring to a flow, we demonstrated in this work that some QoS metrics specified in the SLAs, such as bandwidth, can be honored. Both modules were implemented and evaluated through a prototype. The evaluation results referring to several aspects of both proposed modules are presented in this dissertation, showing the obtained accuracy of the monitoring module SDNMon and the QoS gains due to the utilization of multiple paths defined by the MP-Routing, when forwarding data flow through the SDN.

The Importance of Proper Measurement for a Cloud Security Assurance Model

Winner of a best paper award.

Information Security in the Cloud: Should We be Using a Different Approach?

Postprint

A branch and efficiency algorithm for the optimal design of supply chain networks

Supply chain operations directly affect service levels. Decision on amendment of facilities is generally decided based on overall cost, leaving out the efficiency of each unit. Decomposing the supply chain superstructure, efficiency analysis of the facilities (warehouses or distribution centers) that serve customers can be easily implemented. With the proposed algorithm, the selection of a facility is based on service level maximization and not just cost minimization as this analysis filters all the feasible solutions utilizing Data Envelopment Analysis (DEA) technique. Through multiple iterations, solutions are filtered via DEA and only the efficient ones are selected leading to cost minimization. In this work, the problem of optimal supply chain networks design is addressed based on a DEA based algorithm. A Branch and Efficiency (B&E) algorithm is deployed for the solution of this problem. Based on this DEA approach, each solution (potentially installed warehouse, plant etc) is treated as a Decision Making Unit, thus is characterized by inputs and outputs. The algorithm through additional constraints named “efficiency cuts”, selects only efficient solutions providing better objective function values. The applicability of the proposed algorithm is demonstrated through illustrative examples.

Managing Rentals with Usage-Based Loss

Motivated by new and innovative rental business models, this paper develops a novel discrete-time model of a rental operation with random loss of inventory due to customer use. The inventory level is chosen before the start of a finite rental season, and customers not immediately served are lost. Our analysis framework uses stochastic comparisons of sample paths to derive structural results that hold under good generality for demands, rental durations, and rental unit lifetimes. Considering different \recirculation" rules | i.e., which rental unit to choose to meet each demand | we prove the concavity of the expected profit function and identify the optimal recirculation rule. A numerical study clarifies when considering rental unit loss and recirculation rules matters most for the inventory decision: Accounting for rental unit loss can increase the expected profit by 7% for a single season and becomes even more important as the time horizon lengthens. We also observe that the optimal inventory level in response to increasing loss probability is non-monotonic. Finally, we show that choosing the optimal recirculation rule over another simple policy allows more rental units to be profitably added, and the profit-maximizing service level increases by up to 6 percentage points.

The Views of Young People about an Intervention Programme Designed to Support Them with Exam Related Anxiety and Stress

Both preparing for and sitting exams can be extremely stressful for children and young people. Whilst the research within the area of exam anxiety acknowledges the detrimental impact that it can have on individuals, much of the research has been completed with university students. Limited research has been carried out with children and young people. In addition to this, there is also little research that has been completed in order to understand which interventions are helpful in reducing exam anxiety in young people. The systematic literature review highlighted that much of the research employed quantitative techniques. This means young people’s views and experiences of exam anxiety has largely been unexplored. The EPS service in which the TEP currently works is a partially traded service. Some of the schools that had bought a service level agreement requested support for certain pupils that were experiencing exam anxiety. The EPS service therefore delivered an intervention called ‘beating exam anxiety together’ (further details of this intervention can be found within chapter 1). Seven semi-structured interviews were carried out with GCSE students who took part in the ‘beating exam anxiety together’ intervention. The purpose of the interviews was to understand more about young people’s views on exam anxiety, and also their experiences of the intervention in which they took part. The research highlighted the possible detrimental impact of exam anxiety on young people in terms of their mental health, and also how able they feel to prepare for their exams. The results of the research interestingly showed that young people experience high levels of pressure from school teachers and also their parents. Furthermore, students reported that they didn't know how to revise. The results revealed that young people feel that the way in which exams are spoken about in schools is largely negative. As a result of this, the researcher suggested that it may be helpful to shift the narrative around the way in which exams are currently spoken about. In addition to this, the results indicate that the intervention was largely helpful in improving young people’s well being and their ability to be able to manage exam anxiety.

Pico Cell Integration to Operator’s Incident Management Process

Mobile network coverage is traditionally provided by outdoor macro base stations, which have a long range and serve several of customers. Due to modern passive houses and tightening construction legislation, mobile network service is deteriorated in many indoor locations. Typically, solutions for indoor coverage problem are expensive and demand actions from the mobile operator. Due to these, superior solutions are constantly researched. The solution presented in this thesis is based on Small Cell technology. Small Cells are low power access nodes designed to provide voice and data services.. This thesis concentrates on a specific Small Cell solution, which is called a Pico Cell. The problem regarding Pico Cells and Small Cells in general is that they are a new technological solution for the mobile operator, and the possible problem sources and incidents are not properly mapped. The purpose of this thesis is to figure out the possible problems in the Pico Cell deployment and how they could be solved within the operator’s incident management process. The research in the thesis is carried out with a literature research and a case study. The possible problems are investigated through lab testing. Pico Cell automated deployment process was tested in the lab environment and its proper functionality is confirmed. The related network elements were also tested and examined, and the emerged problems are resolvable. Operators existing incident management process can be used for Pico Cell troubleshooting with minor updates. Certain pre-requirements have to be met before Pico Cell deployment can be considered. The main contribution of this thesis is the Pico Cell integrated incident management process. The presented solution works in theory and solves the problems found during the lab testing. The limitations in the customer service level were solved by adding the necessary tools and by designing a working question pattern. Process structures for automated network discovery and pico specific radio parameter planning were also added for the mobile network management layer..

Stratégie de gestion de stocks dans un réseau collaboratif

Le contenu de ce mémoire traite du problème de gestion des stocks dans un réseau constitué de plusieurs sites de stockage de produits. Chaque site i gère son stock de manière autonome pour satisfaire une demande déterministe sur un horizon donné. Un stock maximum Si est tenu à chaque site i. Lorsque le point de commande si est atteint, une commande de taille Qi est placée au centre de distribution qui alimente tous les sites. Qi est telle que Qi = Si - si. La quantité Qi est livrée dans un délai connu Li. Si, à un instant donné, la demande Di au site i excède la quantité en main, le site i fait appel à un ou à plusieurs autres sites du réseau pour le transfert d’une quantité Xji (j = 1, 2, …, n). Ce transfert s’effectue selon un certain nombre de règles de jeu qui tiennent compte des coûts de transfert, de stockage, d’approvisionnement et de pénurie. Ce mémoire examine six principales contributions publiées dans la littérature pour évaluer les contributions d’un modèle collaboratif aux performances, en termes de coûts et de niveau de service, de chaque site du réseau. Cette investigation se limite à une configuration du réseau à deux échelons : un entrepôt central et n (n > 2) sites de stockage. Le cas des pièces de rechange, caractérisé par une demande aléatoire, est examiné dans trois chapitres de ce mémoire. Une autre application de ces stratégies à la collaboration entre n centres hospitaliers (n > 2) est également examinée dans ce travail.

Carrier Selection for Multi-commodity Flow Optimization in Cooperative Environments

Part 18: Optimization in Collaborative Networks

Improving Resource Management in Virtualized Data Centers using Application Performance Models

The rapid growth of virtualized data centers and cloud hosting services is making the management of physical resources such as CPU, memory, and I/O bandwidth in data center servers increasingly important. Server management now involves dealing with multiple dissimilar applications with varying Service-Level-Agreements (SLAs) and multiple resource dimensions. The multiplicity and diversity of resources and applications are rendering administrative tasks more complex and challenging. This thesis aimed to develop a framework and techniques that would help substantially reduce data center management complexity. We specifically addressed two crucial data center operations. First, we precisely estimated capacity requirements of client virtual machines (VMs) while renting server space in cloud environment. Second, we proposed a systematic process to efficiently allocate physical resources to hosted VMs in a data center. To realize these dual objectives, accurately capturing the effects of resource allocations on application performance is vital. The benefits of accurate application performance modeling are multifold. Cloud users can size their VMs appropriately and pay only for the resources that they need; service providers can also offer a new charging model based on the VMs performance instead of their configured sizes. As a result, clients will pay exactly for the performance they are actually experiencing; on the other hand, administrators will be able to maximize their total revenue by utilizing application performance models and SLAs. This thesis made the following contributions. First, we identified resource control parameters crucial for distributing physical resources and characterizing contention for virtualized applications in a shared hosting environment. Second, we explored several modeling techniques and confirmed the suitability of two machine learning tools, Artificial Neural Network and Support Vector Machine, to accurately model the performance of virtualized applications. Moreover, we suggested and evaluated modeling optimizations necessary to improve prediction accuracy when using these modeling tools. Third, we presented an approach to optimal VM sizing by employing the performance models we created. Finally, we proposed a revenue-driven resource allocation algorithm which maximizes the SLA-generated revenue for a data center.

Asociaciones público privadas para la infraestructura social en salud: hacia la identificación de pautas para la definición de un modelo colombiano

Las asociaciones público privadas "APP" han sido utilizadas para distribuir riesgos y fomentar el desarrollo de los países a través de la provisión de infraestructura. Así, se implementan para proveer bienes y servicios públicos tanto en los sectores de infraestructura productiva (carreteras, puertos, aeropuertos, trenes), como en el sector de infraestructura social (escuelas, universidades, hospitales, edificaciones públicas, etc.). En Colombia, ante la escasez de recursos públicos y la necesidad de formular posiibles soluciones a la crisis del sector salud, surge como una posible solución el modelo de APP consagrado en la Ley 1508 de 2008.

Delegation, Arbitration and High-Level Service Discovery as Key Elements of a Software Infrastructure for Pervasive Computing

The dream of pervasive computing is slowly becoming a reality. A number of projects around the world are constantly contributing ideas and solutions that are bound to change the way we interact with our environments and with one another. An essential component of the future is a software infrastructure that is capable of supporting interactions on scales ranging from a single physical space to intercontinental collaborations. Such infrastructure must help applications adapt to very diverse environments and must protect people's privacy and respect their personal preferences. In this paper we indicate a number of limitations present in the software infrastructures proposed so far (including our previous work). We then describe the framework for building an infrastructure that satisfies the abovementioned criteria. This framework hinges on the concepts of delegation, arbitration and high-level service discovery. Components of our own implementation of such an infrastructure are presented.

Can population-level variation in early childhood development be measured in a manner that supports service planning and intervention?

Background: The Early Development Instrument (EDI) is a population-level measure of five developmental domains at school-entry age. The overall aim of this thesis was to explore the potential of the EDI as an indicator of early development in Ireland. Methods: A cross-sectional study was conducted in 47 primary schools in 2011 using the EDI and a linked parental questionnaire. EDI (teacher completed) scores were calculated for 1,344 children in their first year of full-time education. Those scoring in the lowest 10% of the sample population in one or more domains were deemed to be 'developmentally vulnerable'. Scores were correlated with contextual data from the parental questionnaire and with indicators of area and school-level deprivation. Rasch analysis was used to determine the validity of the EDI. Results: Over one quarter (27.5%) of all children in the study were developmentally vulnerable. Individual characteristics associated with increased risk of vulnerability were being male; under 5 years old; and having English as a second language. Adjusted for these demographics, low birth weight, poor parent/child interaction and mother’s lower level of education showed the most significant odds ratios for developmental vulnerability. Vulnerability did not follow the area-level deprivation gradient as measured by a composite index of material deprivation. Children considered by the teacher to be in need of assessment also had lower scores, which were not significantly different from those of children with a clinical diagnosis of special needs. all domains showed at least reasonable fit to the Rasch model supporting the validity of the instrument. However, there was a need for further refinement of the instrument in the Irish context. Conclusion: This thesis provides a unique snapshot of early development in Ireland. The EDI and linked parental questionnaires are promising indicators of the extent, distribution and determinants of developmental vulnerability.