Alexandre Sztajnberg - Academia.edu (original) (raw)

Papers by Alexandre Sztajnberg

Network Function Virtualization increases flexibility and reduces the costs of telecommunication ... more Network Function Virtualization increases flexibility and reduces the costs of telecommunication infrastructures. To do so, network functions are implemented on virtualized servers, rather than embedded in dedicated equipment. One of the challenges of this approach is the placement of virtual network functions over the infrastructure, which must be resilient and energy-efficient. This work formulates a mixed integer programming problem to place such functions, choosing the servers meeting service demands. The problem formulated minimizes energy utilization and provides resilience to the services through function replication. As solution, TRELIS heuristic is proposed, which reduces the size of the problem and saves up to 15% of the energy consumption. Resumo. A Virtualização de Funções de Rede aumenta a flexibilidade e reduz custos de infraestruturas de telecomunicações. Para tal, as funções de rede são implementadas em servidores virtualizados, ao invés de embarcadas em equipamentos dedicados. Um dos desafios dessa abordagemé o posicionamento de funções virtuais de rede, que deve ser resiliente e energeticamente eficiente. Este trabalho formula um problema de programação inteira mista para posicionar tais funções, escolhendo os servidores para atenderàs demandas de serviço. O problema formulado minimiza o uso da energia e provê resiliência aos serviços através de replicação de funções. Como solução, propõe-se a heurística TRE-LIS, que reduz o tamanho do problema e economiza até 15% da energia. * Este trabalho foi realizado com recursos da FAPERJ, CNPq e CAPES.

As the computer networks have become wider and more complex, always dealing with greater informat... more As the computer networks have become wider and more complex, always dealing with greater information traffic and high computational effort applications, the distributed systems appeared as a way to share the resources needed by different entities and execute tasks in different stations. Many solutions were developed, such as cloud computing, grids, clusters and peerto-peer networks (P2P). Nevertheless, planning such networks involves greater costs, what makes it more interesting to use simulators to verify its planning decisions. Therefore, this survey addresses to different simulation environments and their features, performing a comparative study of their functionalities. Resumo. Conforme as redes de computadores se tornaram maiores e mais complexas, sempre lidando com maiores tráfegos e aplicações de alto esforço computacional, os sistemas distribuídos surgiram como uma forma de partilhar os recursos necessários por diversas entidades e executar tarefas em diferentes estações. Muitas soluções foram desenvolvidas, como a computação em nuvem, as grades, os clusters e as redes par-a-par (P2P). No entanto, projetar tais redes envolve custos maiores, o que torna interessante a utilização de simuladores para verificar as decisões de planejamento. Sendo assim, este trabalho se endereça a diferentes ambientes de simulação e suas características, realizando um estudo comparativo de suas funcionalidades.

SBC Journal on Interactive Systems, Nov 16, 2011

In this paper we present an overview of the LATVI-Laboratório de Tecnologias Virtuais e Inteligen... more In this paper we present an overview of the LATVI-Laboratório de Tecnologias Virtuais e Inteligentes (Laboratory of Virtual and Intelligent Technologies) at the Rio de Janeiro State University. The mission and main objectives are discussed. Current and ongoing projects are outlined.

Separation of concerns is a key goal in achieving software reusability. Meta-Level Programming ap... more Separation of concerns is a key goal in achieving software reusability. Meta-Level Programming approaches pave the way to separation of concerns by handling functional and non-functional aspects in different levels, but provide little help for software composition, verification and evolution activities. Approaches based on Software Architecture Description Languages can overcome these deficiencies and additionally may discipline, and make explicit, the deployment of meta-level programming. R-RIO combines both approaches providing a useful framework to develop, implement and maintain applications.

Software - Practice and Experience, Sep 15, 2010

Resource management is an important aspect to consider regarding applications that might have dif... more Resource management is an important aspect to consider regarding applications that might have different non‐functional or operational requirements, when running in distributed and heterogeneous environments. In this context, it is necessary to provide the means to specify the required resource constraints and an infrastructure that can adapt the applications in light of the changes in resource availability. We adopted a contract‐based approach to describe and maintain parallel applications that have non‐functional requirements in a Computing Grid context, called ZeliGrid. To form the supporting infrastructure we have designed a software architecture that integrates some of the Globus services, the LDAP and the NWS monitoring services. Some modules that map the contract approach into software artifacts were also integrated to this architecture. This paper addresses the architecture and integration issues of our approach, as well as how we put the pieces together highlighting deployment and implementation details, which have to consider diverse aspects such as monitoring, security and dynamic reconfiguration. Copyright © 2010 John Wiley & Sons, Ltd.

Electronic Notes in Theoretical Computer Science, May 1, 2004

The Internet of Things will expose services enabling developers to easily explore data generated ... more The Internet of Things will expose services enabling developers to easily explore data generated by an enormous number of devices. These devices, such as industrial sensors and actuators, and house appliances can have different interfaces, interaction protocols, and payload data semantics. Manual, ad hoc, integration of these different devices would become infeasible. This paper presents an approach to dynamically integrate devices into an IoT context-aware infrastructure, which includes a well-defined architecture and a reflective description model. This infrastructure, named ContQuest, also offers a set of middleware services for context-aware applications, which rely on the reflective data to provide adaptation capabilities. In ContQuest, a device is considered a resource and is represented by Resource Agent. Each Resource Agent is structured following an architecture that aims to ease the integration and deployment of heterogeneous devices, including design solutions to adapt devices that can have different communication protocols. The approach is demonstrated using examples: (i) a wireless sensor network and (ii) a RFID reader.

This paper presents the project of a compiler for the Architecture Description Language (ADL) CBa... more This paper presents the project of a compiler for the Architecture Description Language (ADL) CBabel, developed as part of the R-RIO framework. This compiler verifies software architecture descriptions, and generates appropriate files to integrate the compiled architecture into the framework's execution environment. These files contain configuration instructions, for loading the architecture, and a repository with the architecture meta-level information for runtime consulting. It is also presented a repository explorer, developed for viewing the repository metalevel information data.

Lecture Notes in Computer Science, 2004

This paper presents an approach to describe, deploy and manage component-based applications havin... more This paper presents an approach to describe, deploy and manage component-based applications having dynamic functional and non-functional requirements. The approach is centered on architectural descriptions and associated high-level contracts. Besides specifying non-functional (or QoS) requirements, these contracts are used to guide architecture customizations required to enforce the requirements. The infrastructure required to manage the contracts follows an architectural pattern, which can be directly mapped to specific components included in a supporting reflective middleware. This approach allows designers to write a contract and to follow a standard recipe to insert the extra code required to its enforcement in the supporting middleware.

This work addresses wireless communication for a fleet of unmanned surface vehicles (USVs) in aqu... more This work addresses wireless communication for a fleet of unmanned surface vehicles (USVs) in aquatic environment. In order to carry out the communication in this complex scenario, an application protocol operating over a Wi-Fi network in the ad hoc mode combined with the AODV routing protocol (Ad-hoc On-demand Distance Vector) is proposed. The proposed protocol is based on IP broadcast messages limited to one hop and bounded length (bytes). The performance and limitations of the protocol are evaluated by means of simulations. The results indicate that the proposed protocol extends the range of the communication network and may be used for the cooperative control and monitoring of USVs. Resumo: Este trabalho aborda a comunicação sem fio para uma frota de veículos de superfície não tripulados (Unmanned Surface Vehicles, USVs) em ambiente aquático. Para realizar a comunicação neste cenário desafiador, propõe-se um protocolo de aplicação que opera sobre uma rede Wi-Fi em modo ad hoc combinado com o protocolo de roteamento AODV (Ad-hoc On-demand Distance Vector). O protocolo proposto utiliza mensagens broadcast IP limitadas a um salto e com comprimentos (bytes) limitados. Foram realizadas simulações para verificar o desempenho do protocolo e identificar suas limitações. Os resultados indicam que o protocolo proposto amplia o alcance da rede de comunicação e pode ser utilizado para o controle cooperativo e monitoramento de USVs.

Page 1. Utilização de Redes Neurais para Gerência de Servidores Virtuais Web (Use of Neural Netwo... more Page 1. Utilização de Redes Neurais para Gerência de Servidores Virtuais Web (Use of Neural Networks in the Management of Virtual Web Servers) André Felipe Monteiro1, Marcus V. Azevedo1 1Postgraduate Program in ...

O escalonamento de processos é um assunto que requer dos alunos dos cursos de graduação em Ciênci... more O escalonamento de processos é um assunto que requer dos alunos dos cursos de graduação em Ciências da Computação uma alta capacidade de abstração. Seria desejável uma ferramenta que auxiliasse na compreensão dos aspectos cuja compreensão é mais difícil quando apresentados apenas pelos métodos de ensino convencionais. Desenvolvemos um simulador de mecanismos de alocação da CPU que se propõe a facilitar a tarefa de avaliar o impacto da implantação de um determinado mecanismo de alocação da CPU sobre um sistema computacional. O simulador fornece aos usuários meios de criar mecanismos de alocação da CPU de forma personalizada e, em seguida, testá-los sobre diferentes condições de funcionamento. Conseguimos um software didático, extensível, reutilizável, modular e independente de plataforma.

Journal of Systems and Software, Nov 1, 2013

This work proposes a reusable architecture that enables the self-configuration of a supporting in... more This work proposes a reusable architecture that enables the self-configuration of a supporting infrastructure for Web server clusters using virtual machines. The goal of the architecture is to ensure service quality, evaluating how broadly it complies with the application's operating restrictions and proportionally acting on the configuration of physical servers (hosts) or virtual machines. In addition, through the rational use of resources, the proposal aims at saving energy. A prototype of the architecture was developed and a performance evaluation carried out with two different resource management approaches. This evaluation shows how fully functional and advantageous the proposal is in terms of using resources, avoiding waste, yet maintaining the application's quality of service within acceptable levels. The architecture also shows to be flexible enough to accept, with a reasonable amount of effort, different resource self-configuration policies.

Journal of the Brazilian Computer Society, Feb 1, 2004

This paper presents a comprehensive approach to describe, deploy and adapt component-based applic... more This paper presents a comprehensive approach to describe, deploy and adapt component-based applications having dynamic non-functional requirements. The approach is centered on high-level contracts associated to architectural descriptions, which allow the non-functional requirements to be handled separately during the system design process. This helps to achieve separation of concerns facilitating the reuse of modules that implement the application in other systems. Besides specifying non-functional requirements, contracts are used at runtime to guide configuration adaptations required to enforce these requirements. The infrastructure required to manage the contracts follows an architectural pattern, which can be directly mapped to specific components included in a supporting reflective middleware. This allows designers to write a contract and to follow standard recipes to insert the extra code required to its enforcement in the supporting middleware.

Cadernos do IME, Apr 25, 2014

Cadernos do IME, Dec 31, 2011

This work proposes a new representation to be used on online signature authenticating systems. Ou... more This work proposes a new representation to be used on online signature authenticating systems. Our approach is based on features used in graphoscopy which takes the form of a signature to classify it as genuine or forgery. For each point of the captured signature it calculates the normal vector to compare with the variation of the curvature in the signature's trajectory. The proposed approach is also invariant to scale, rotation and translation. The obtained vector is aligned using Dynamic Time Warping in the classification process. Experiments were performed using the linear classifier in conjunction with the Principal Component Analysis (PCA) to compare the results with those obtained in [3].

Neste trabalho discutimos a implementação de um sistema de simulação de estratégias de negócios, ... more Neste trabalho discutimos a implementação de um sistema de simulação de estratégias de negócios, desenvolvido a partir de um jogo chamado GOALS (Game Oriented Advanced Learning System)[2]. Este jogo foi proposto com o objetivo de treinar e capacitar empresários a tomar decisões de forma rápida e precisa. A implementação do simulador foi desenvolvida no contexto de um projeto de graduação no DICC/IME/UERJ [1]. Um primeiro protótipo deste projeto, desenvolvido em parceria com a Goals Project do Brasil, foi aplicado em um curso ministrado na Riosoft. A partir desta experiência, foi possível aperfeiçoar a implementação. Palavras-chave. Simuladores e jogos educativos, simuladores estratégicos, mercados controlados, simuladores distribuídos.

Anais do XXVI Simpósio Brasileiro de Telecomunicações, 2008

Resumo-Este artigo propõe uma nova métrica, AP (Alternative Path), a ser utilizada para o cálculo... more Resumo-Este artigo propõe uma nova métrica, AP (Alternative Path), a ser utilizada para o cálculo de rotas em protocolos de roteamento em redes em malha sem fio. Esta métrica leva em consideração a interferência causada por nós vizinhos na escolha de uma rota para um destino. O desempenho da métrica AP é avaliado e comparado com o da métrica ETX (Expected Transmission Count). As simulações realizadas mostram que a métrica AP pode propiciar desempenho superior à rede. Palavras-chave-redes em malha, métricas de roteamento, protocolos de roteamento.