Atualmente, os usuários desejam obter, fornecer, compartilhar e interagir com informações e serviços com conteúdo multimídia em qualquer lugar, a qualquer momento e com qualquer dispositivo. Para que isso seja possível, um dos grandes desafios é assegurar a QoS (Quality of Service) fim a fim (entre o usuário final e a organização provedora de serviço) para a disponibilização de serviços móveis e interativos com conteúdo multimídia para os usuários finais. Em geral esse tipo de serviço têm maior exigência de QoS, pois além dos parâmetros de redes, possuem parâmetros específicos para áudio, imagem e vídeo, além de exigirem sincronização de áudio e vídeo, e a QoS fim a fim deve considerar parâmetros de QoS sob a percepção do usuário final. Com isso, o objetivo deste trabalho é propor um método para o levantamento de parâmetros de QoS para o estabelecimento de USLAs (User Service Level Agreements - Acordo do Nível de Serviço do Usuário) entre a organização provedora de serviço e o usuário final para serviços móveis e interativos com conteúdo multimídia em um ambiente de convergência tecnológica. O método consiste em quatro passos: 1. identificação do serviço a ser oferecido ao usuário final e elaboração de um grafo em árvore, que tem como objetivo identificar outros serviços que podem compor o serviço a ser oferecido ao usuário final; 2. mapeamento dos parâmetros de QoS em um metamodelo; 3. validação do metamodelo, para que se possa extrair do metamodelo os parâmetros de QoS; 4. elaboração do USLA. Este trabalho propõe um primeiro passo para solucionar a falta de métodos padronizados para o estabelecimento de USLA para serviços móveis e interativos com conteúdo multimídia sob a percepção do usuário final. Além de facilitar a identificação e composição de serviços e parâmetros, por meio de um metamodelo que proporciona a integração de classes de serviços que podem ser facilmente reutilizadas e customizadas, de acordo, com o tipo de serviço oferecido pela organização provedora de serviço e pela necessidade do usuário final. / In these days the final users wish to obtain, to furnish and to interact using interactive services with multimedia content anywhere, anytime and with any kind of user device. One of the biggest challenges is to assure the End-to End Quality of Service (E2E QoS) in the delivering of the interactive and multimedia services for moving users. In general, this kind of users have more strict requirements needs, because, besides of the computer network parameters, they need specify specific parameters like sound, image and video and their synchronization, on the users\' point of the view - perceived QoS. The main objective of this thesis is to present the application of a method for eliciting the E2E QoS parameters aiming the establishment of the User Service Level Agreement - USLA between the service provider and the final user applied to interactive and mobile services with multimedia content, inserted on a technological convergence environment. The method is a four steps method that consists of (1) an identification of the service to be offered to the final user and the elaboration of a tree graph aiming the identification of the composition of the service by other services (2) mapping the QoS parameters in a metamodel (3) validation of the metamodel, and extraction of the E2E QoS parameters (4) elaboration the USLA. This thesis proposes a first step to solve the lack of standardized methods for the establishment of the USLA for interactive and mobile services with multimedia content under the users\' perception. Besides of facilitating the identification and the composition of services and parameters, using a metamodel, that provides the integration of classes of services, that can be easily reused and customized, according, with the type of service offered for the service provider to the final user.

Atualmente, os usuários desejam obter, fornecer, compartilhar e interagir com informações e serviços com conteúdo multimídia em qualquer lugar, a qualquer momento e com qualquer dispositivo. Para que isso seja possível, um dos grandes desafios é assegurar a QoS (Quality of Service) fim a fim (entre o usuário final e a organização provedora de serviço) para a disponibilização de serviços móveis e interativos com conteúdo multimídia para os usuários finais. Em geral esse tipo de serviço têm maior exigência de QoS, pois além dos parâmetros de redes, possuem parâmetros específicos para áudio, imagem e vídeo, além de exigirem sincronização de áudio e vídeo, e a QoS fim a fim deve considerar parâmetros de QoS sob a percepção do usuário final. Com isso, o objetivo deste trabalho é propor um método para o levantamento de parâmetros de QoS para o estabelecimento de USLAs (User Service Level Agreements - Acordo do Nível de Serviço do Usuário) entre a organização provedora de serviço e o usuário final para serviços móveis e interativos com conteúdo multimídia em um ambiente de convergência tecnológica. O método consiste em quatro passos: 1. identificação do serviço a ser oferecido ao usuário final e elaboração de um grafo em árvore, que tem como objetivo identificar outros serviços que podem compor o serviço a ser oferecido ao usuário final; 2. mapeamento dos parâmetros de QoS em um metamodelo; 3. validação do metamodelo, para que se possa extrair do metamodelo os parâmetros de QoS; 4. elaboração do USLA. Este trabalho propõe um primeiro passo para solucionar a falta de métodos padronizados para o estabelecimento de USLA para serviços móveis e interativos com conteúdo multimídia sob a percepção do usuário final. Além de facilitar a identificação e composição de serviços e parâmetros, por meio de um metamodelo que proporciona a integração de classes de serviços que podem ser facilmente reutilizadas e customizadas, de acordo, com o tipo de serviço oferecido pela organização provedora de serviço e pela necessidade do usuário final. / In these days the final users wish to obtain, to furnish and to interact using interactive services with multimedia content anywhere, anytime and with any kind of user device. One of the biggest challenges is to assure the End-to End Quality of Service (E2E QoS) in the delivering of the interactive and multimedia services for moving users. In general, this kind of users have more strict requirements needs, because, besides of the computer network parameters, they need specify specific parameters like sound, image and video and their synchronization, on the users\' point of the view - perceived QoS. The main objective of this thesis is to present the application of a method for eliciting the E2E QoS parameters aiming the establishment of the User Service Level Agreement - USLA between the service provider and the final user applied to interactive and mobile services with multimedia content, inserted on a technological convergence environment. The method is a four steps method that consists of (1) an identification of the service to be offered to the final user and the elaboration of a tree graph aiming the identification of the composition of the service by other services (2) mapping the QoS parameters in a metamodel (3) validation of the metamodel, and extraction of the E2E QoS parameters (4) elaboration the USLA. This thesis proposes a first step to solve the lack of standardized methods for the establishment of the USLA for interactive and mobile services with multimedia content under the users\' perception. Besides of facilitating the identification and the composition of services and parameters, using a metamodel, that provides the integration of classes of services, that can be easily reused and customized, according, with the type of service offered for the service provider to the final user.

Le « Cloud computing » est un nouveau modèle de systèmes de calcul. L’infrastructure, les applications et les données sont déplacées de machines localisées sur des systèmes dématérialisés accédés sous forme de service via Internet. Le modèle « coût à l’utilisation » permet des économies de coût en modifiant la configuration à l’exécution (élasticité). L’objectif de cette thèse est de contribuer à la gestion de la Qualité de Service (QdS) des applications s’exécutant dans le Cloud. Les services Cloud prétendent fournir une flexibilité importante dans l’attribution des ressources de calcul tenant compte des variations perçues, telles qu’une fluctuation de la charge. Les capacités de variation doivent être précisément exprimées dans un contrat (le Service Level Agreement, SLA) lorsque l’application est hébergée par un fournisseur de Plateform as a Service (PaaS). Dans cette thèse, nous proposons et nous décrivons formellement le langage de description de SLA PSLA. PSLA est fondé sur WS-Agreement qui est lui-même un langage extensible de description de SLA. Des négociations préalables à la signature du SLA sont indispensables, pendant lesquelles le fournisseur de PaaS doit évaluer la faisabilité des termes du contrat. Cette évaluation, par exemple le temps de réponse, le débit maximal de requêtes servies, etc, est fondée sur une analyse du comportement de l’application déployée dans l’infrastructure cloud. Une analyse du comportement de l’application est donc nécessaire et habituellement assurée par des tests (benchmarks). Ces tests sont relativement coûteux et une étude précise de faisabilité demande en général de nombreux tests. Dans cette thèse, nous proposons une méthode d’étude de faisabilité concernant les critères de performance, à partir d’une proposition de SLA exprimée en PSLA. Cette méthode est un compromis entre la précision d’une étude exhaustive de faisabilité et les coûts de tests. Les résultats de cette étude constituent le modèle initial de la correspondance charge entrante-allocation de ressources utilisée à l’exécution. Le contrôle à l’exécution (runtime control) d’une application gère l’allocation de ressources en fonction des besoins, s’appuyant en particulier sur les capacités de passage à l’échelle (scalability) des infrastructures de cloud. Nous proposons RCSREPRO (Runtime Control method based on Schedule, REactive and PROactive methods), une méthode de contrôle à l’exécution fondée sur la planification et des contrôles réactifs et prédictifs. Les besoins d’adaptation à l’exécution sont essentiellement dus à une variation de la charge soumise à l’application, variations difficiles à estimer avant exécution et seulement grossièrement décrites dans le SLA. Il est donc nécessaire de reporter à l’exécution les décisions d’adaptation et d’y évaluer les possibles variations de charge. Comme les actions de modification des ressources attribuées peuvent prendre plusieurs minutes, RCSREPRO réalise un contrôle prédictif fondée sur l’analyse de charge et la correspondance indicateurs de performance-ressources attribuées, initialement définie via des tests. Cette correspondance est améliorée en permanence à l’exécution. En résumé, les contributions de cette thèse sont la proposition de langage PSLA pour décrire les SLA ; une proposition de méthode pour l’étude de faisabilité d’un SLA ; une proposition de méthode (RCSREPRO) de contrôle à l’exécution de l’application pour garantir le SLA. Les travaux de cette thèse s’inscrivent dans le contexte du projet FSN OpenCloudware (www.opencloudware.org) et ont été financés en partie par celui-ci. / Cloud computing is a new computing model. Infrastructure, application and data are moved from local machines to internet and provided as services. Cloud users, such as application owners, can greatly save budgets from the elasticity feature, which refers to the “pay as you go” and on-demand characteristics, of cloud service. The goal of this thesis is to manage the Quality of Service (QoS) for applications running in cloud environments Cloud services provide application owners with great flexibility to assign “suitable” amount of resources according to the changing needs, for example caused by fluctuating request rate. “Suitable” or not needs to be clearly documented in Service Level Agreements (SLA) if this resource demanding task is hosted in a third party, such as a Platform as a Service (PaaS) provider. In this thesis, we propose and formally describe PSLA, which is a SLA description language for PaaS. PSLA is based on WS-Agreement, which is extendable and widely accepted as a SLA description language. Before signing the SLA contract, negotiations are unavoidable. During negotiations, the PaaS provider needs to evaluate if the SLA drafts are feasible or not. These evaluations are based on the analysis of the behavior of the application deployed in the cloud infrastructure, for instance throughput of served requests, response time, etc. Therefore, application dependent analysis, such as benchmark, is needed. Benchmarks are relatively costly and precise feasibility study usually imply large amount of benchmarks. In this thesis, we propose a benchmark based SLA feasibility study method to evaluate whether or not a SLA expressed in PSLA, including QoS targets, resource constraints, cost constraints and workload constraints can be achieved. This method makes tradeoff between the accuracy of a SLA feasibility study and benchmark costs. The intermediate of this benchmark based feasibility study process will be used as the workload-resource mapping model of our runtime control method. When application is running in a cloud infrastructure, the scalability feature of cloud infrastructures allows us to allocate and release resources according to changing needs. These resource provisioning activities are named runtime control. We propose the Runtime Control method based onSchedule, REactive and PROactive methods (RCSREPRO). Changing needs are mainly caused by the fluctuating workload for majority of the applications running in the cloud. The detailed workload information, for example the request arrival rates at scheduled points in time, is difficult to be known before running the application. Moreover, workload information listed in PSLA is too rough to give a fitted resource provisioning schedule before runtime. Therefore, runtime control decisions are needed to be performed in real time. Since resource provisioning actions usually require several minutes, RCSREPRO performs a proactive runtime control which means that it predicts future needs and assign resources in advance to have them ready when they are needed. Hence, prediction of the workload and workload-resource mapping are two problems involved in proactive runtime control. The workload-resource mapping model, which is initially derived from benchmarks in SLA feasibility study is continuously improved in a feedback way at runtime, increasing the accuracy of the control.To sum up, we contribute with three aspects to the QoS management of application running in the cloud: creation of PSLA, a PaaS level SLA description language; proposal of a benchmark based SLA feasibility study method; proposal of a runtime control method, RCSREPRO, to ensure the SLA when the application is running. The work described in this thesis is motivated and funded by the FSN OpenCloudware project (www.opencloudware.org).

De nos jours, le Cloud Networking est considéré comme étant l'un des domaines de recherche innovants au sein de la communauté de recherche du Cloud Computing. Les principaux défis dans un environnement de Cloud Networking concernent non seulement la garantie de qualité de service (QoS) et de sécurité mais aussi sa gestion en conformité avec un accord de niveau de service (SLA) correspondant. Dans cette thèse, nous proposons un Framework pour l'allocation des ressources conformément à un SLA établi de bout en bout entre un utilisateur de services Cloud (CSU) et plusieurs fournisseurs de services Cloud (CSP) dans un environnement de Cloud Networking (architectures d’inter-Cloud Broker et Fédération). Nos travaux se concentrent sur les services Cloud de types NaaS et IaaS. Ainsi, nous proposons l'auto-établissement de plusieurs types de SLA ainsi que la gestion autonome des ressources de Cloud correspondantes en conformité avec ces SLA en utilisant des gestionnaires autonomes spécifiques de Cloud. De plus, nous étendons les architectures et les SLA proposés pour offrir un niveau de service intégrant une garantie de sécurité. Ainsi, nous permettons aux gestionnaires autonomes de Cloud d'élargir leurs objectifs de gestion autonome aux fonctions de sécurité (auto-protection) tout en étudiant l'impact de la sécurité proposée sur la garantie de QoS. Enfin, nous validons notre architecture avec différents scénarios de simulation. Nous considérons dans le cadre de ces simulations des applications de vidéoconférence et de calcul intensif afin de leur fournir une garantie de QoS et de sécurité dans un environnement de gestion autonome des ressources du Cloud. Les résultats obtenus montrent que nos contributions permettent de bonnes performances pour ce type d’applications. En particulier, nous observons que l'architecture de type Broker est la plus économique, tout en assurant les exigences de QoS et de sécurité. De plus, nous observons que la gestion autonome des ressources du Cloud permet la réduction des violations, des pénalités et limite l'impact de la sécurité sur la garantie de la QoS. / Today, Cloud Networking is one of the recent research areas within the Cloud Computing research communities. The main challenges of Cloud Networking concern Quality of Service (QoS) and security guarantee as well as its management in conformance with a corresponding Service Level Agreement (SLA). In this thesis, we propose a framework for resource allocation according to an end-to-end SLA established between a Cloud Service User (CSU) and several Cloud Service Providers (CSPs) within a Cloud Networking environment (Inter-Cloud Broker and Federation architectures). We focus on NaaS and IaaS Cloud services. Then, we propose the self-establishing of several kinds of SLAs and the self-management of the corresponding Cloud resources in conformance with these SLAs using specific autonomic cloud managers. In addition, we extend the proposed architectures and the corresponding SLAs in order to deliver a service level taking into account security guarantee. Moreover, we allow autonomic cloud managers to expand the self-management objectives to security functions (self-protection) while studying the impact of the proposed security on QoS guarantee. Finally, our proposed architecture is validated by different simulation scenarios. We consider, within these simulations, videoconferencing and intensive computing applications in order to provide them with QoS and security guarantee in a Cloud self-management environment. The obtained results show that our contributions enable good performances for these applications. In particular, we observe that the Broker architecture is the most economical while ensuring QoS and security requirements. In addition, we observe that Cloud self-management enables violations and penalties’ reduction as well as limiting security impact on QoS guarantee.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal.

Nos tempos atuais, cada vez mais as organizações têm investido em equipamentos e infra-estrutura de educação a distância (EAD). Grande parte dos estudos até hoje realizados dizem respeito a aspectos pedagógicos relacionados a esse tipo de sistema produtivo. Contudo, há poucos estudos dedicados a sua gestão. Esta dissertação busca, por meio de uma pesquisa à literatura pertinente, seguida de uma pesquisa de campo, sistematizar o conhecimento sobre a gestão de um sistema de operações de EAD, buscando formas para otimizar sua disponibilidade operacional. Ao longo do trabalho, a disponibilidade é tratada com um indicador de resultado de duas diferentes funções da organização: função gestão de contratos e função manutenção. A primeira diz respeito ao acordo de nível de serviço (SLA) firmado entre a organização foco deste estudo e um fornecedor de serviços de telecomunicações. A segunda função compreende a forma como são adotadas abordagens ou políticas de manutenção para os equipamentos utilizados para a execução desse tipo de serviço. Assim, descreve-se o contexto em que se inserem a disponibilidade e as duas funções a ela relacionadas e buscam-se formas para coordenar essas funções com o objetivo de otimizar a disponibilidade operacional do sistema produtivo. Algumas proposições foram estruturadas e verificadas numa organização, através da metodologia científica pesquisa-ação. Um instrumento referencial foi elaborado para amparar a pesquisa de campo visando facilitar a verificação das proposições propostas, além de colaborar para melhor atingir os objetivos propostos. A conclusão da pesquisa revela que as proposições de estudo não se confirmaram de forma plena, apontando para um sensível distanciamento entre teoria e pratica organizacional, deixando, assim, espaço aberto para novos estudos. / In present days, organizations are investing increasingly in equipment and infrastructure for distance education (DE). Great part of the studies carried out until today focus on the pedagogical aspects related to this type of productive system. However, there are few studies dedicated to its management. It is the goal of this study, through research in specific literature followed by a field research, to systemize the knowledge on management of an operational system for DE, searching for ways to optimize its operational availability. Throughout the work, the availability is considered a result indicator for two different functions of the organization: contract management function and maintenance function. The former one says respect to the service level agreement (SLA) firmed between the organization, focus of this study, and a supplier of telecommunications services. The latter is concerned with the ways that maintenance approaches and politics for the equipment involved in the execution of this type of service are adopted. Thus, the context in which the availability and both related functions are enclosed has been described and ways to co-ordinate these functions with the goal of optimizing the productive system operational availability is searched. The framework of some proposals was developed and verified in an organization through the scientific methodology ?Action Research?. A reference instrument was elaborated to support the field research aiming to ease the verification of the proposals that have been made, besides helping to achieve the proposed goal. The research conclusion discloses that the study proposals weren?t fully confirmed, leading to a considerable withdraw between organizational theory and practice, leaving, thus, an open space for new studies.

<p>Revenue maximization for network operators is considered as a criterion for resource allocation in wireless cellular networks. A business model encompassing service level agreements between network operators and service providers is presented. Admission control, through price model aware admission policing and service level control, is critical for the provisioning of useful services over a general purpose wireless network. A technical solution consisting of a fast resource scheduler taking into account service requirements and wireless channel properties, a service level controller that provides the scheduler with a reasonable load, and an admission policy to uphold the service level agreements and maximize revenue, is presented.</p><p>Two different types of service level controllers are presented and implemented. One is based on a scalar PID controller, that adjusts the admitted data rates for all active clients. The other one is obtained with linear programming methods, that optimally assign data rates to clients, given their channel qualities and price models.</p><p>Two new scheduling criteria, and algorithms based on them, are presented and evaluated in a simulated wireless environment. One is based on a quadratic criterion, and is implemented through approximative algorithms, encompassing a search based algorithm and two different linearizations of the criterion. The second one is based on statistical measures of the service rates and channel states, and is implemented as an approximation of the joint probability of achieving the delay limits while utilizing the available resources efficiently.</p><p>Two scheduling algorithms, one based on each criterion, are tested in combination with each of the service level controllers, and evaluated in terms of throughput, delay, and computational complexity, using a target test system. Results show that both schedulers can, when feasible, meet explicit throughput and delay requirements, while at the same time allowing the service level controller to maximize revenue by allocating the surplus resources to less demanding services.</p>

Revenue maximization for network operators is considered as a criterion for resource allocation in wireless cellular networks. A business model encompassing service level agreements between network operators and service providers is presented. Admission control, through price model aware admission policing and service level control, is critical for the provisioning of useful services over a general purpose wireless network. A technical solution consisting of a fast resource scheduler taking into account service requirements and wireless channel properties, a service level controller that provides the scheduler with a reasonable load, and an admission policy to uphold the service level agreements and maximize revenue, is presented. Two different types of service level controllers are presented and implemented. One is based on a scalar PID controller, that adjusts the admitted data rates for all active clients. The other one is obtained with linear programming methods, that optimally assign data rates to clients, given their channel qualities and price models. Two new scheduling criteria, and algorithms based on them, are presented and evaluated in a simulated wireless environment. One is based on a quadratic criterion, and is implemented through approximative algorithms, encompassing a search based algorithm and two different linearizations of the criterion. The second one is based on statistical measures of the service rates and channel states, and is implemented as an approximation of the joint probability of achieving the delay limits while utilizing the available resources efficiently. Two scheduling algorithms, one based on each criterion, are tested in combination with each of the service level controllers, and evaluated in terms of throughput, delay, and computational complexity, using a target test system. Results show that both schedulers can, when feasible, meet explicit throughput and delay requirements, while at the same time allowing the service level controller to maximize revenue by allocating the surplus resources to less demanding services.

<p>With Cloud Computing becoming a popular term on the Information Technology (IT) market, security and accountability has become important issues to highlight. In our research we review these concepts by focusing on security risks with Cloud Computing and the associated services; Software, Platform and Infrastructure (SPI) and connecting them with a social study of trust.</p><p>The method that was conducted during our research was reviewing secondary literature, interviewing different experts regarding Cloud Computing and relating standards already established by ENISA, NIST, and CSA to the interviews.</p><p>The result of this study shows connections between the specific SPIs, both how they compare, but also how they differ. In the end we were also able to rank the top security risks from interviews with experts and see which SPI could be the most insecure one and  what countermeasures could be applied.</p><p>This was further related to trust and Service Level Agreement (SLA) in Cloud Computing to show how the security risks we discuss are related to these two specific areas. By highlighting this we wanted to present useable information for both clients and providers in how to create a better Cloud Computing environment.</p>

Αντικείμενο της παρούσας Διατριβής είναι η μελέτη της απόδοσης και η εισαγωγή νέων χαρακτηριστικών σε μοντέλα για την παροχή υπηρεσιών με εγγυήσεις ποιότητας στα σύγχρονα IP δίκτυα καθώς και η εισαγωγή των απαραίτητων επιχειρησιακών λειτουργιών για την εφαρμογή των μοντέλων αυτών, με στόχο τη βελτίωση της απόδοσης. Ακολουθώντας μια καταγραφή και αξιολόγηση των μηχανισμών και αρχιτεκτονικών που εισάγουν τη διαφοροποίηση εξυπηρέτησης στα IP δίκτυα, η μελέτη που παρουσιάζεται εδώ ακολουθεί σε όλα της τα στάδια τις αρχές της αρχιτεκτονικής DiffServ, η οποία επιτρέπει την παροχή ενός συγκεκριμένου εύρους υπηρεσιών με εγγυήσεις ποιότητας σε συναθροίσεις ροών και περιορίζει την πολυπλοκότητα στα όρια του δικτύου. Η απόδοση και η αποτελεσματικότητα των μηχανισμών και λειτουργιών διαφοροποίησης εξυπηρέτησης με βάση την αρχιτεκτονική DiffServ αξιολογούνται με βάση την εξασφάλιση εγγυημένης χωρητικότητας, φραγμένης από-άκρο-σε-άκρο καθυστέρησης, ελαχιστοποιημένων απωλειών πακέτων και φραγμένου jitter. Ωστόσο, σε κάθε μοντέλο υπηρεσίας για την παροχή QoS, τονίζεται η σημασία της εξασφάλισης των καλύτερων δυνατών εγγυήσεων ποιότητας με την ελάχιστη δυνατή πολυπλοκότητα. Τα διαφορετικά μοντέλα υπηρεσιών θέτουν συγκεκριμένους στόχους λαμβάνοντας υπόψη τις ανάγκες των εφαρμογών στις οποίες απευθύνονται. Οι δύο επικρατέστερες κατηγορίες υπηρεσιών στα πλαίσια της αρχιτεκτονικής DiffServ είναι η κατηγορία των υπηρεσιών μέγιστης προτεραιότητας και η κατηγορία των υπηρεσιών εγγυημένης χωρητικότητας σε συνθήκες συμφόρησης. Στην πρώτη κατηγορία, προτείνεται το μοντέλο υπηρεσίας Gold, το οποίο ακολουθεί τις αρχές τις αρχιτεκτονικής DiffServ για να παρέχει βέλτιστη ποιότητα εξυπηρέτησης σε συναθροίσεις IP ροών, ενώ ταυτόχρονα μπορεί να εφαρμοστεί πρακτικά σε δίκτυα παραγωγής. Στη δεύτερη κατηγορία, προτείνεται το μοντέλο υπηρεσίας Relative για την παροχή υπηρεσιών εγγυημένης χωρητικότητας σε συνθήκες συμφόρησης, με βασικά χαρακτηριστικά την μείωση της υπολογιστικής πολυπλοκότητας και την βελτίωση της δικαιοσύνης μεταξύ των εξυπηρετούμενων TCP ροών. Η υπηρεσία Gold διατηρεί την αρχή της επεκτασιμότητας και παρέχει αυστηρές εγγυήσεις ποιότητας αλλά ταυτόχρονα επιτρέπει την εφαρμογή μηχανισμού ελέγχου αποδοχής νέων αιτημάτων χωρίς διακοπή της λειτουργίας του δικτύου. Eισάγει επίσης ένα νέο χαρακτηριστικό σε σχέση με τα υπάρχοντα σχήματα: την διαφοροποίηση ως προς την εγγυημένη μέγιστη καθυστέρηση που παρέχεται στις ροές. Υλοποιείται με τη χρονοδρομολόγηση LA-EDF, που εισάγει την έννοια της διαφοροποιημένης εξυπηρέτησης εντός της ίδιας κλάσης υπηρεσίας και λειτουργεί ως υποστηρικτικός μηχανισμός του ελέγχου αποδοχής κλήσεων, τον αλγόριθμο DBAC για την αποδοχή κλήσεων χωρίς επέμβαση στη λειτουργία του δικτύου και την δρομολόγηση εξισορρόπησης φόρτου για την καλύτερη αξιοποίηση των διαθέσιμων πόρων χωρίς να παραβιάζονται οι εγγυήσεις ποιότητας. Η υπηρεσία Relative επιτυγχάνει προσαρμοστικότητα σε συνθήκες μεταβαλλόμενου φόρτου, δίκαιη διαφοροποίηση, υψηλή απόδοση, αύξηση της χρησιμοποίησης των διαθέσιμων πόρων ενώ αντιμετωπίζει πολλές από τις αδυναμίες που παρουσιάζουν αντίστοιχα μοντέλα. Υλοποιείται με τον μηχανισμό μαρκαρίσματος TWAM ο οποίος εφαρμόζεται στο σημείο εισόδου των ροών στο δίκτυο και αντιμετωπίζει τα θέματα της μη δίκαιης μεταχείρισης TCP ροών με τη μικρότερη δυνατή υπολογιστική επιβάρυνση σε σχέση με υπάρχοντες μηχανισμούς μαρκαρίσματος και τον μηχανισμό DWRED για την ενεργητική διαχείριση του αποθηκευτικού χώρου των ουρών, ο οποίος λειτουργεί με βάση το μαρκάρισμα της κίνησης που επιφέρει ο TWAM και προσαρμόζεται στις μεταβαλλόμενες συνθήκες λειτουργίας. Μεταξύ των καθοριστικών παραγόντων για την ευρεία υιοθέτηση υπηρεσιών βασισμένων στην αρχιτεκτονική DiffServ στα σύγχρονα δίκτυα παραγωγής, αναδεικνύονται η εισαγωγή ευέλικτων επιχειρηματικών μοντέλων για την υλοποίηση των υπηρεσιών αυτών στο εσωτερικό ενός δικτύου καθώς και χρέωσης των παρεχόμενων υπηρεσιών. Ο ορισμός Συμβολαίων Εξασφάλισης Επιπέδου Υπηρεσιών (ΣΕΕΥ) για δίκτυα που υποστηρίζουν την παροχή QoS υπηρεσιών με βάση την αρχιτεκτονική DiffServ έχει ως στόχο την εξασφάλιση της συμβατότητας των παρεχόμενων από διαφορετικά διασυνδεδεμένα δίκτυα υπηρεσιών προκειμένου για την από-άκρο-σε-άκρο εξασφάλιση εγγυήσεων ποιότητας. Προτείνεται ένα πρότυπο για την υλοποίηση διμερών ΣΕΕΥ σε IP δίκτυα που παρέχουν υπηρεσίες μέγιστης προτεραιότητας καθώς και μια μεθοδολογία για την υλοποίηση από-άκρο-σε-άκρο Συμβολαίων πάνω από διασυνδεδεμένα δίκτυα. Σε ένα IP δίκτυο, η εισαγωγή ενός αριθμού κλάσεων υπηρεσιών που διαφοροποιούνται στις παρεχόμενες ποιοτικές εγγυήσεις απαιτεί την εισαγωγή διαφοροποιημένων μοντέλων χρέωσης που επιπρόσθετα οδηγούν τους χρήστες στην επιλογή της κατάλληλης κλάσης υπηρεσίας η οποία μεγιστοποιεί την αντιληπτή χρησιμότητα. Προκειμένου για τη χρέωση υπηρεσιών με βάση την αρχιτεκτονική DiffServ, τα προφίλ κίνησης των χρηστών και οι διαφορές στην αντιληπτή ποιότητα αντιπροσωπεύουν τη χρησιμότητα που αντιλαμβάνεται ο χρήστης. Προτείνεται ένα μοντέλο χρέωσης όπου το προφίλ της κίνησης αποτελεί το αντικείμενο διαπραγμάτευσης του χρήστη με τον πάροχο, αφού ο χρήστης συνυπολογίσει τις εγγυήσεις ποιότητας εξυπηρέτησης που ανακοινώνονται από τον τελευταίο προκαταβολικά. Η καινοτομία του προτεινόμενου μοντέλου συνίσταται στις εξωτερικές συνθήκες (externalities) που υπεισέρχονται στα υφιστάμενα κόστη και προκαλούνται από τη φύση των υπηρεσιών που υλοποιούνται με βάση το μοντέλο DiffServ, καθώς επίσης και στον καθορισμό των πραγματικών τιμών με βάση τις οποίες χρεώνονται οι χρήστες. / The goal of this Dissertation is to study the performance of existing tools and the introduction of new features to quality of service provisioning models in IP networks as well as the introduction of the business models required for applying these models in an operational environment in ways that the performance is improved. Following the evaluation of mechanisms and architectures for differentiation of service in IP networks, the principles of the DiffServ framework have been adopted. The DiffServ framework specifies the provision of a set of services with qualitative guarantees to traffic aggregates, while keeping complexity at the network edges. The performance and effectiveness of service differentiation mechanisms according to the principles of the DiffServ framework are evaluated according to the following metrics: guaranteed capacity, bounded end-to-end delay, minimization of packet losses and jitter. However, in any QoS model, it is important to ensure the best quality possible by keeping complexity low. Each QoS model is designed to meet the needs of a different traffic type. The two prevailing service models within the DiffServ framework are the maximum priority, maximum quality model and the guaranteed capacity under congestion model. The proposed Gold service falls within the first category above, offering advanced quality to IP traffic aggregates with a set of principles that can easily be applied to operational networks. The proposed Relative service model provides guaranteed capacity under congestion by reducing the complexity and improving fairness among TCP flows. The Gold service preserves scalability and provides strict quality guarantees, incorporating a call admission control mechanism that operates without interfering with the network operations. It introduces a novel feature: differentiation of the guarantees on end-to-end delay provided to traffic flow. It is implemented using LA-EDF scheduling that introduces service differentiation within the same class and supports the call admission control functions, the DBAC algorithm for admission control and flow routing with load balancing for optimizing the use of available resources without compromising in terms of the guaranteed quality. The Relative service achieves high adaptability in transient load conditions, fair differentiation, high quality, increase in the utilization of available resources without demonstrating the same weaknesses as equivalent service models. It is implemented using the TWAM marking mechanism, which is applied at the network ingress and ensures fairness with less overhead than similar mechanisms, and DWRED, the active queue management mechanism that depends upon the TWAM marking and adapts to the varying load levels. The introduction of effective business and pricing models is crucial for the adoption of qualitative service models based on the DiffServ framework in a production network. The definition of Service Level Agreements (SLAs) for networks that provide QoS according to the principles of the DiffServ framework aims at introducing compatibility among the services provided for the provisioning of end-to-end quality guarantees. A template for the implementation for bilateral SLAs between networks that support the maximum priority, maximum quality service model is proposed, together with a methodology for implementing, based on the bilateral SLA, an end-to-end SLA over multiple domains. In an IP network, the introduction of a set of services classes with differing quality guarantees necessitates the application of differentiated pricing models that lead the users to the selection of the appropriate service class in order to maximize their perceived utility. Based on the principles of the DiffServ framework, the utility for each user is determined by the profile of his traffic and the quality of service he perceives. The proposed pricing model appoints the traffic profile as the parameter for negotiation between the user and the provider, after the user assesses the quality guarantees announced by the provider prior to the service provisioning. The innovation here lies in the introduction of externalities to the costs induced as well as the announcement of the actual prices upon which the user will eventually be charged. The externalities are imposed by the nature of the service models implemented according to the DiffServ framework.