Esta dissertação de mestrado apresenta a implementação e validação de um modelo de servidor web que divide o funcionamento de o servidor web em quatro módulos onde cada um desses módulos é responsável por uma etapa que a requisição percorre ao longo de seu processamento. Esses módulos são: atendimento da requisição (módulo 1), transferência do arquivo para a memória principal (módulo 2), processamento de requisições dinâmicas (módulo 3) e envio do arquivo ao cliente (módulo 4). Esses quatro módulos são interligados e são alimentados primeiramente por uma carga inicial gerada pelo gerador de cargas W4Gen e passa obrigatoriamente, nessa ordem, pelo módulo 1, módulo 2 e módulo 4. O módulo 3 só é utilizado quando se trata de uma requisição dinâmica. Ao ser atendido por um dos módulos, é atribuído um tempo de execução (leia-se tempo que a requisição toma para ser processada por esse módulo). Esses tempos foram baseados em trabalhos que fizeram benchmarks em servidores web reais. Os resultados alcançados com o desenvolvimento deste trabalho visam principalmente integrar-se aos trabalhos de simulação envolvendo servidores web do grupo de Sistemas Distribuídos e Programação Concorrente (LaSDPC) e com isso alcançar resultados próximos a resultados aplicados em servidores web reais / This work presents the implementation and validation of a web server model that divides the web server functions into four modules and each one of these is responsible for an execution step, in which a request goes through during processing. These modules are: request serving (module 1); file transferring to the main memory (module 2); dynamic request processing (module 3); and client file sending (module 4). These four modules are linked and the W4Gen generates the initial loads. These loads run in the order as follows: modules 1, 2 and 4. The module 3 is used only when the request is dynamic. When a request is served by a module, an execution time is defined (i.e. the time used by the request in the module), which is based on real world web servers benchmark\'s. The results obtained in the work aims to be integrated to other projects conduced in the Distributed System and Concurrent Programming group (LaSDPC) in order to reach results close to real world web servers

Esta dissertação apresenta a construção de um protótipo de servidor Web distribuído, baseado no modelo de servidor Web com diferenciação de serviços (SWDS) e a implementação e avaliação de algoritmos de seleção, utilizando o conceito de controle de congestionamento para requisições HTTP. Com isso, além de implementar uma plataforma de testes, este trabalho também avalia o comportamento de dois algoritmos de controle de congestionamento. Os dois algoritmos estudados são chamados de Drop Tail e RED (Random Early Detection), no qual são bastante difundidos na literatura científica e aplicados em redes de computadores. Os resultados obtidos demostram que, apesar das particularidades de cada algoritmo, existe uma grande relação entre tempo de resposta e a quantidade de requisições aceitas / This MSc dissertation presents the implementation of a prototype for a distributed web server based on the SWDS, a model for a web server with service differentiation, and the implementation and evaluation of selection algorithms adopting the concept of congestion control for HTTP requests. Thus, besides implementing a test platform this work also evaluates the behavior of two congestion control algorithms. The two algorithms studied are the Drop Tail and the RED (Random Early Detection), which are frequently discussed in the scientific literature and widely applied in computer networks. The results obtained show that, although the particularities of each algorithm, there is a strong relation between the response times and the amount of requests accepted in the server

Esta dissertação de mestrado apresenta a prototipação de uma arquitetura denominada ServidorWeb com Diferenciação de Serviços (SWDS). O trabalho também apresenta a proposta, implementação e a avaliação de desempenho de dois algoritmos de controle de admissão denominados Algoritmo de Negociação e Algoritmo de Reserva de Conexões. O objetivo principal deste trabalho é a avaliação de desempenho dos algoritmos de controle de admissão no protótipo do SWDS. Como resultados, verificou-se que a Classe de maior prioridade consegue atender mais requisições que a Classe de menor prioridade em todos as configurações de carga. Também pode-se observar que o algoritmo de reserva de conexões consegue se adaptar a todas as variações de cargas / This masters dissertation presents the prototype of an architecture named SWDS. This work presents the proposal, implementation and performance evaluation of two admission control algorithms named negotiation algorithm and connection reserve algorithm. The aim of this work is to evaluate the performance of the control admission algorithms in the SWDS prototype. As a result, it could be seen the high priority Class met a higher number of requests than the low priority Class. Also it could be seen the connection reserve algorithm can adapt to all workloads variation

Esta dissertação de mestrado apresenta a prototipação de uma arquitetura denominada ServidorWeb com Diferenciação de Serviços (SWDS). O trabalho também apresenta a proposta, implementação e a avaliação de desempenho de dois algoritmos de controle de admissão denominados Algoritmo de Negociação e Algoritmo de Reserva de Conexões. O objetivo principal deste trabalho é a avaliação de desempenho dos algoritmos de controle de admissão no protótipo do SWDS. Como resultados, verificou-se que a Classe de maior prioridade consegue atender mais requisições que a Classe de menor prioridade em todos as configurações de carga. Também pode-se observar que o algoritmo de reserva de conexões consegue se adaptar a todas as variações de cargas / This masters dissertation presents the prototype of an architecture named SWDS. This work presents the proposal, implementation and performance evaluation of two admission control algorithms named negotiation algorithm and connection reserve algorithm. The aim of this work is to evaluate the performance of the control admission algorithms in the SWDS prototype. As a result, it could be seen the high priority Class met a higher number of requests than the low priority Class. Also it could be seen the connection reserve algorithm can adapt to all workloads variation

The rapidly increasing expansion of the Internet has brought dramatic impact to our life and education alike. The major feature differentiates e-learning from the traditional learning is its ability to train anyone, anytime, and anywhere attributed to the Internet. Many experts tell us that e-learning will plays the key-enabling role in knowledge management for individual, schools, and enterprise. Nevertheless, the lack of standard in courseware and learning management system (LMSs) makes courseware in different LMS platforms can not be exchanged directly, and there is no way to monitor and evaluate learner¡¦s behavior from one platform to another. And there are LMS platforms do not provide the effective protection mechanism for courseware in the LMS platforms; this will let an unauthorized user can retrieve courseware as well as he knows the correct URL in the LMS. In this thesis, in order to overcome those hurdles, we refer to the e-learning standard, called Sharable Content Object Reference Model (SCORM), to enhance this feature on our existing LMS platform. And we propose an effective courseware access control mechanism which implement at the kernel of the web server.

A World Wide Web é um meio de comunicação em constante crescimento, agregando diversos componentes e serviços em um ritmo acelerado. Os novos tipos de sites, tais como, o comércio eletrônico (e-commerce), notí?cia/informação (Web-publishing), vídeo sob demanda exigem ainda mais recursos do servidor. Nesse contexto, visando adequar a avaliação de desempenho aos novos ambientes da Web, o presente trabalho apresenta um estudo caracterizando diversos traces de servidores Web Apache, permitindo coletar dados importantes que definem a forma como os usuários e servidores interagem. Com esses dados, quatro tipos de categorias de sites foram analisados: Padrão (composto da média de todos os traces analisados), Acadêmico, Notícia/Informação e Tradicional. Nessa análise avaliam-se quatro aspectos: o intervalo de chegada, o código de resposta, o tipo objeto e o tamanho do objeto e ao final, modelos matemáticos são propostos para representar essas características. Além disso, este trabalho também desenvolveu um gerador de cargas de trabalho sintéticas, o W4Gen(World Wide Web Workload Generator). Com uma interface gráfica amigável, ele permite aos seus usuários gerar novas cargas com base nos modelos matemáticos. Além disso, ele também permite modificar as características essenciais para simular novos tipos de cargas. Para validar os resultados deste trabalho, utilizou-se o modelo de servidor Web com diferenciação de serviços (SWDS), verificando o desempenho em situações de sobregarga / World Wide Web is a media in constant growth, joining several components and services in an accelerated evolution. The new kinds of sites, such as, E-commerce, Web-publishing and demand video still uses more servers resources. In this context, adapting the newWeb environment to performance evaluation, the present work accomplished a characterization study of several Apache Web servers traces, allowing collect important data that define the form as users and servers interact. With these data, four types of sites categories were analyzed: Default (composed of all trace), Academic, Web-publishing and Traditional. In this analysis, it was evaluated four aspects: the arrival time, the status code, the object class and the object size and at the end, mathematical models are proposed to represent those characteristics. Furthermore, a synthetic workload generator was also developed. With a graphical interface, the W4Gen (World WideWebWorkload Generator), as called, allows the users to generate new workloads based on mathematical models. Besides, it also allows to modify the four essential aspects preseted above to simulate new types of workloads. Finally, to validate the results, the Web server model with differentiated services was used, verifying the performance in overload situations

Esta dissertação de mestrado aborda a introdução de reconhecimento de sessões http em um modelo de servidor web com serviços diferenciados (SWDS). Algumas técnicas foram desenvolvidas com o objetivo de produzir diferenciação de serviços junto com garantias de que novas sessões poderiam ser aceitas no sistema. Esses objetivos constituem requisitos essenciais na Internet atual, especialmente para aplicações web modernas. Um novo esquema para controle de admissão de sessões foi desenvolvido e introduzido no modelo SWDS, considerando dois mecanismos para aceitar novas sessões, com garantia de nalização. O mecanismo que estima a capacidade do sistema de aceitar novas sessões, baseado em um modelo de sessão construído dinamicamente a partir da carga do sistema, é destacado. A proposta global deste trabalho também considera um controle de admissão de requisições, baseado em sessões, onde a nova política de atendimento criada mantém o sistema livre de sobrecargas e oferece atendimento diferenciado para as sessões. As políticas de negociação desenvolvidas para o controle de admissão de requisições tiveram um papel importante neste trabalho, contribuindo para a priorização do atendimento das sessões. Os resultados obtidos mostram que os controles propostos constituem estruturas fundamentais para a estabilidade do desempenho do sistema, tanto quanto os mecanismos desenvolvidos têm grande importância no atendimento das sessões e, portanto de seus clientes, através de uma abordagem baseada em diferenciação. / This MSc dissertation approaches the introduction of the HTTP sessions recognition in a web server model with diferentiated services (SWDS). Some techniques have been developed aiming at issuing diferentiation of services together with guarantees that new sessions could be accepted in the system. These aims constitute essential requirements for the current Internet, especially for modern web applications. A new scheme for the admission control system has been developed and introduced in the SWDS model, considering two mechanisms for accepting new sessions, with guarantee of their nalizations. The mechanism that estimates the system capacity of acceptance of a new session, based on a session model built dynamically from system workload information, is highlighted. The global propose of this work also considers a request admission control, based on sessions, where the new attendance polices created keep the system free from overloads and over diferentiated attendance for the sessions. The negotiation polices developed for request admission control had an important place in this work, contributing for the session attendance prioritization. The results reached show that the controls proposed comprise fundamental structures for system performance stability, as well as the mechanisms developed have great importance in attending sessions and, therefore, their clients by means of a diferentiation-based approach.

Virtualization allows computer users to utilize their resources more efficiently and effectively. Operating system that runs on top of the Virtual Machine or Hypervisor is called guest OS. The Virtual Machine is an abstraction of the real physical machine. The main aim of this thesis work was to analyze different kinds of virtualization software packages and to investigate their advantages and disadvantages. In addition, we analyzed the performance of the virtual software packages with a real operating system in terms of web services. Web Servers play an important role on the Internet. The response time and throughput for a web server are different for different virtualization software packages and between a real host and a virtual host. In this thesis, we analyzed the web server performance on Linux. We compared the throughput for three different virtualization software packages (VMware, QEMU, and Virtual Box). The performance results clearly indicate that the real machine performance is better than the performance of the virtual machines. VMware has the better performance compared to other virtual software packages.

Context: Cloud computing is a concept in which a user get services like SaaS, PaaS and IaaS by deploying their data and application on remotely servers. Users have to pay only for the time the resources are acquired. They do not need to install and upgrade software and hardware. Due to these benefits organization are willing to move their data into the cloud and minimize their overhead. Organizations need to confirm that cloud can replace the traditional platform, software and hardware in an efficient way and provide robust performance. Web servers play a vital role providing services and deploying application. One might be interested to have information about a web server performance in the cloud. With this aim, we have compared cloud server performance with a local web server. Objectives: The objective of this study is to investigate cloud performance. For this purpose, we first find out the parameters and factors that affect a web server performance. Finding the parameters helped us in measuring the actual performance of a cloud server on some specific task. These parameters will help users, developers and IT specialists to measure cloud performance based on their requirements and needs. Methods: In order to fulfill the objective of this study, we performed a Systematic literature review and an experiment. The Systematic literature review is performed by studying articles from electronic sources including ACM Digital Library, IEEE, EiVillage (Compendx,Inspec). The Snowball method is used to minimize the chance of missing articles and to increase the validity of our findings. In experiment, two performance parameters (Throughput and Execution Time) are used to measure the performance of the Apache Web Server in Local and Cloud environment. Results: In Systematic literature review, we found many factors that affect the performance of a web server in Cloud computing. Most common of them are throughput, response time, execution time, CPU and other resource utilization. The experimental results revealed that web server performed well in local environment as compared to cloud environment. But there are other factors like cost overhead, software/ hardware configuration, software/hardware up -gradation and time consumption due to which cloud computing cannot be neglected. Conclusions: The parameters that affect the cloud performance are throughput, response time, execution time, CPU utilization and memory utilization. Increase and decrease in values of these parameters can affect cloud performance to a great extent. Overall performance of a cloud is not that effective but there are other reasons for using cloud computing

Parallel processing is prevalent in many manufacturing and service systems. Many manufactured products are built and assembled from several components fabricated in parallel lines. An example of this manufacturing system configuration is observed at a manufacturing facility equipped to assemble and test web servers. Characteristics of a typical web server assembly line are: multiple products, job circulation, and paralleling processing. The primary objective of this research was to develop analytical approximations to predict performance measures of manufacturing systems with job failures and parallel processing. The analytical formulations extend previous queueing models used in assembly manufacturing systems in that they can handle serial and different configurations of paralleling processing with multiple product classes, and job circulation due to random part failures. In addition, appropriate correction terms via regression analysis were added to the approximations in order to minimize the gap in the error between the analytical approximation and the simulation models. Markovian and general type manufacturing systems, with multiple product classes, job circulation due to failures, and fork and join systems to model parallel processing were studied. In the Markovian and general case, the approximations without correction terms performed quite well for one and two product problem instances. However, it was observed that the flow time error increased as the number of products and net traffic intensity increased. Therefore, correction terms for single and fork-join stations were developed via regression analysis to deal with more than two products. The numerical comparisons showed that the approximations perform remarkably well when the corrections factors were used in the approximations. In general, the average flow time error was reduced from 38.19% to 5.59% in the Markovian case, and from 26.39% to 7.23% in the general case. All the equations stated in the analytical formulations were implemented as a set of Matlab scripts. By using this set, operations managers of web server assembly lines, manufacturing or other service systems with similar characteristics can estimate different system performance measures, and make judicious decisions - especially setting delivery due dates, capacity planning, and bottleneck mitigation, among others.