The flexibility offered by mobile agents is quite noticeable in distributed computing environments. But the flexibility comes with a set of new levels of complexity due to their autonomous nature. The mobile agent paradigm introduce additional threats since agents systems are prone to failures originating from bad communication, security attacks, agent server crashes, system resources unavailability, network congestion or even deadlock situations. In such events, mobile agents either get lost or damaged (partially or totally) during execution. In order to gain solid foundation at the heart of today’s e-society, the mobile agent technology paradigm must address the issue of reliability. Making mobile agents fault tolerant is a measure taken to increase the dependability and reliability of agent-based application. Mobile agent’s fault tolerance is gaining momentum and many approaches have been proposed. Despite these efforts, the field still suffers from set backs in the form of persistent challenges. This study analyzes the existing fault tolerance approaches against a proposed generic fault tolerance framework that consists of a monitoring, planning and recovery process execution phases. Following the analysis, this study brings about the state-of-the-art in mobile agent’s fault tolerance approaches and the lingering challenges that affect mobile agent’s fault tolerance implementations from being efficiently and fully realized. The study will serve as a guide to future researches and possible solution for a more reliable and transparent fault tolerance in mobile agents.

The size and complexity of local area and wide area networks are continually growing and so do the requirements of high availability. Today we rely on the technology and it should always work. Network management is therefore getting more and more important. Network management includes: monitoring and isolating faults, measuring performance, configuring the resources, making sure the network is secured and more. Since in the early 1990s the management has typically been done with SNMPv1 or CMIP and using the client/server model. SNMPv1 is insecure, CMIP is complex and the traditional centralized paradigm is no longer sufficient to handle the management requirements of large networks. As the demands for security and flexibility increases, new ways to manage networks are needed. This research tries to find out how a network management system should function, what management protocol to use, how to enhance the flexibility and how to make the system more secure.

In this thesis we look at mobile agent solutions to black hole search and related problems. Mobile agents are computational entities that are autonomous, mobile, and can interact with their environment and each other. The black hole search problem is for a team of these agents to work together to map or explore a graph-like network environment where some elements of the network are dangerous to the agents. Most research into black hole search has focussed on finding a single dangerous node: a black hole. We look at the problem of finding multiple black holes and, in the case of dangerous graph exploration, multiple black links as well. We look at the dangerous graph exploration problem in the network model. The network model is based on a normal static computer network modelled as a simple graph. We give an optimal solution to the dangerous graph exploration problem using agents that start scattered on nodes throughout the network. We then make the problem more difficult by allowing an adversary to delete links during the execution of the algorithm and provide a solution using scattered agents. In the last decade or two, types of networks have emerged, such as ad hoc wireless networks, that are by their nature dynamic. These networks change quickly over time and can make distributed computations difficult. We look at black hole search in one type of dynamic network described by the subway model, which we base on urban subway systems. The model allows us to look at the cost of opportunistic movement by requiring the agents to move using carriers that follow routes among the network's sites, some of which are black holes. We show that there are basic limitations on any solution to black hole search in the subway model and prove lower bounds on any solution's complexity. We then provide two optimal solutions that differ in the agents' starting locations and how they communicate with one another. Our results provide a small window into the cost of deterministic distributed computing in networks that have dynamic elements, but which are not fully random.

Em aplicações distribuídas baseadas em agentes móveis, a coordenação das ações dos agentes móveis é uma tarefa complexa. A maior dificuldade é devido ao fato que agentes móveis podem mudar de endereço dinamicamente. Nesta dissertação, apresentamos o projeto e a implementação de um mecanismo de coordenação de agentes móveis que contorna este problema. Este mecanismo, que chamamos de Canal de Broadcast, está baseado na difusão de mensagens e possibilita que os membros de um grupo de agentes móveis interajam entre si, independentemente de suas localizações correntes. Modelos de coordenação existentes oferecem formas de interação entre agentes móveis, mas todos eles impõem alguma exigência. Ou os agentes móveis devem conhecer a localização de outros agentes, ou devem estar localizados no mesmo lugar ou devem migrar para um lugar específico. A principal vantagem deste mecanismo de coordenação está na total transparência de localização: as mensagens podem ser endereçadas a um conjunto de agentes móveis independentemente de sua localização corrente. Este mecanismo foi implementado no ASDK (Aglets Software Development Kit) da IBM e a sua utilidade foi demonstrada usando dois problemas típicos de coordenação em Sistemas Distribuídos: a Exclusão Mútua e o protocolo Manager-Workers. Testamos o desempenho do mecanismo e identificamos que o custo do Canal de Broadcast não é tão alto comparado aos benefícios que proporciona. Através deste mecanismo, os agentes móveis poderão executar as suas tarefas e interagir entre sí com o propósito da coordenação sem as exigências impostas por outros modelos de coordenação. / In distributed applications based on mobile agents, the coordination of mobile agents actions is a difficult task. The main difficulty comes from the fact that mobile agents can change their address dynamically. In this dissertation, we present the project and implementation of a mechanism for coordinating mobile agents that overcomes this problem. This mechanism, which we called Broadcast Channel, is based on the difusion of messages and enables the members of a mobile agent group to interact with each other independently of their current locations. Existing coodination models offer some means of interaction between mobile agents, but all of them impose some requirements. Either the mobile agents must know about each other's location, or must be located at the same place or must move to a specific place. The main advantage of our coordination mechanism is the full location transparency: the messages can be sent to a set of mobile agents independently of their current locations. This mechanism was implemented using IBM's ASDK (Aglets Software Development Kit) and its use was demonstrated using two typical coordination problems in Distributed Systems: the Mutual Exclusion and the Manager-Workers protocol. We tested the performance of the mechanism and identified that the cost of the Broadcast Channel is not too high, compared to the benefit it provides. Through this mechanism, the mobile agents can do their tasks and interact with each other for the purpose of coordination without the requirements imposed by other models.

In this research, the application of intelligent mobile agents to the management of distributed network environments is investigated. Intelligent mobile agents are programs which can move about network systems in a deterministic manner in carrying their execution state. These agents can be considered an application of distributed artificial intelligence where the (usually small) agent code is moved to the data and executed locally. The mobile agent paradigm offers potential advantages over many conventional mechanisms which move (often large) data to the code, thereby wasting available network bandwidth. The performance of agents in network routing and knowledge acquisition has been investigated and simulated. A working mobile agent system has also been designed and implemented in JDK 1.2.

Le déploiement de logiciels répartis dans des environnements à grande échelle et ouverts (tels les systèmes ubiquitaires, les systèmes mobiles et les systèmes P2P) est une problématique actuelle ouverte. Ces environnements sont distribués, hétérogènes et peuvent être de nature instable (dotés d’une topologie dynamique du réseau). Le déploiement dans ces environnements met en jeu un très grand nombre de machines, de liens réseau ainsi qu’un ensemble de contraintes de déploiement. Quelques solutions de déploiement existent aujourd’hui, mais ne sont exploitables que dans le cadre d’architectures figées et fiables. Dans la plupart des solutions, une personne en charge du déploiement doit décrire plus ou moins manuellement la topologie. En outre, la majorité de ces outils ne prennent pas en compte les problèmes dûs à la variabilité de la qualité de service du réseau, aux pannes des hôtes, aux défaillances des liens du réseau ou encore aux changements dynamiques de topologie, qui caractérisent les environnements ouverts. Dans ce mémoire, nous présentons les motivations de la réalisation d'une infrastructure de déploiement logiciel autonomique et les exigences sous-jacentes d'une telle plate-forme. Nous présentons un état de l’art du déploiement logiciel que nous analysons au regard du contexte visé. Ensuite, nous présentons notre contribution pour le déploiement autonomique. Notre proposition s'appuie sur une combinaison de technologies (composants logiciels, agents mobiles adaptables, intergiciel, langage dédié). Nous proposons j-ASD, un intergiciel qui exploite la complémentarité de ces technologies pour réaliser un déploiement logiciel autonomique. Le processus de déploiement contient trois étapes : description des contraintes de déploiement, résolution, et déploiement autonomique. Pour la première étape, nous avons défini un langage dédié (DSL) comme langage de haut niveau pour exprimer des contraintes de déploiement. Pour la deuxième, nous avons conçu une infrastructure répartie pour collecter les propriétés des sites cibles, ce qui permet de résoudre les contraintes de déploiement. Pour la troisième étape, nous proposons un intergiciel à base d’agents mobiles pour la réalisation et la supervision du déploiement autonomique. Enfin, nous donnons les éléments de conception du prototype que nous avons implémenté, ainsi que les résultats de certaines expérimentations pour montrer la validité de notre approche / Software deployment in large-scale and open distributed systems (such as ubiquitous systems, mobile systems and P2P systems) is still an open issue. These environments are distributed, heterogeneous and can be naturally unstable (fitted with a dynamic network topology). Deployment in such environments require the management of a large number of hosts, network links and deployment constraints. Existing distributed deployment solutions are usable only within static and reliable topologies of hosts, where a man in charge of the deployment has to describe more or less manually the topology. Moreover, majority of these tools do not take into account network and computer QoS variabilities, hosts crashes, network link failures and network topology changes, which characterize open and mobile environments. In this thesis, we discuss the motivations for an autonomic software deployment and the requirements underlying for such a platform. We carefully study and compare the existing work about software deployment. Then, we propose a middleware framework, designed to reduce the human cost for setting up software deployment and to deal with failure-prone and change-prone environments. We also propose an autonomic deployment process in three steps : deployment constraints description step, constraints resolution step and the autonomic deployment step. For the first step, we defined a high-level constraint-based dedicated language (DSL) as support for expressing deployment constraints. In the second step, we have designed a distributed infrastructure to collect target hosts properties used to solve deployment constraints. For the third step, we propose an agent-based system for establishing and maintaining software deployment. At last, we give an overview of our working prototype with some details on some experimental results

With the fast development of wireless networks and devices, Mobile IP is expected to be used widely so that mobile users can access the Internet anywhere, anytime without interruption. However, some problems, such as firewall traversal and use of private IP addresses, restrict use of Mobile IP. The objective of this thesis is to design original schemes that can enable a mobile node at abroad to access its home network as well as the Internet securely and that can help Mobile IP to be used widely and commercially. Our solutions are secure, efficient, and scalable. They can be implemented and maintained easily. In this thesis, we mainly consider Mobile IPv4, instead of Mobile IPv6. Three research topics are discussed. In each topic, the challenges are investigated and the new solutions are presented. The first research topic solves the firewall traversal problems in Mobile IP. A mobile node cannot access its firewall-protected home network if it fails the authentication by the firewall. We propose that an IPsec tunnel be established between the firewall and the foreign agent for firewall traversal and that an IPsec transport security association be shared by the mobile node and a correspondent node for end-to-end security. The second topic researches further on firewall traversal problems and investigates the way of establishing security associations among network entities. A new security model and a new key distribution method are developed. With the help of the security model and keys, the firewall and the relevant network entities set up IPsec security associations to achieve firewall traversal. A mobile node from a private home network cannot communicate with other hosts with its private home address when it is visiting a public foreign network. A novel and useful solution is presented in the third research topic. We suggest that the mobile node use its Network Access Identifier (NAI) as its identification and obtain a public home address from its home agent. In addition, a new tunnel between the mobile node and its home agent is proposed.

Made available in DSpace on 2016-08-17T14:52:33Z (GMT). No. of bitstreams: 1 Rafael Fernandes Lopes.pdf: 4191329 bytes, checksum: d7582da9cb0e7c9fbb1def0451444863 (MD5) Previous issue date: 2006-01-13 / In recent years, Grid computing has emerged as a promising alternative to the integration and sharing of multi-institutional resources. However, constructing a Grid middleware is a complex task. Developers must address several design and implementation challenges, such as: e±cient management and allocation of distributed resources, dynamic task scheduling, high scalability and heterogeneity, fault tolerance, e±cient mechanisms for collaborative communication among Grid nodes, and security issues. MAG (Mobile Agents for Grid Computing Environments) explores the mobile agent technology as a way to overcome several of these challenges. MAG middleware executes Grid applications by dynamically loading the application code into a mobile agent. The MAG agent can be dynamically reallocated among Grid nodes through a transparent migration mechanism called MAG/Brakes, as a way to provide load balancing and support for non-dedicated nodes. MAG middleware also includes mechanisms for providing application fault tolerance, an essential characteristic for Grid environments. We make extensive use of the agent paradigm to design and implement MAG components, forming a multi-agent infrastructure for computational Grids. This master thesis describes MAG and MAG/Brakes architecture, implementation and performance issues. / Nos ultimos anos, a computação em grade tem emergido como uma promissora alternativa para a integração e compartilhamento de recursos multi-institucionais. Entretanto, a construçãoo de um middleware de grade é uma tarefa complexa. Desenvolvedores devem lidar com vários desafios de projeto e implementação, como: gerenciamento e alocação suficiente de recursos distribuidos, escalonamento dinâmico de tarefas, alta escalabilidade e heterogeneidade, tolerância a falhas, mecanismos suficientes para a comunicação colaborativa entre nós da grade e aspectos de segurança; O MAG (Mobile Agents for Grid Computing Environments) explora a tecnologia de agentes móveis como uma forma de superar vários destes desafios. O middleware MAG executa as aplicações da grade carregando dinamicamente o código da aplicação no agente movel. O agente do MAG pode ser realocado dinamicamente entre nós da grade através de um mecanismo de migração transparente chamado MAG/Brakes, como uma forma de prover balanceamento de carga e suporte para nós não dedicados. O middleware MAG também inclui mecanismos para prover tolerância a falhas de aplicações, uma caracteristica essencial para ambientes de grade. O paradigma de agentes foi extensivamente utilizado para projetar e implementar os componentes do MAG, formando uma infraestrutura multiagente para grades computacionais. Esta dissertação de mestrado descreve a arquitetura, implementação e aspectos de desempenho do MAG e do MAG/Brakes.

Orientador: Manuel de Jesus Mendes / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-04T00:34:30Z (GMT). No. of bitstreams: 1 Silva_PauloSergioda_D.pdf: 1777936 bytes, checksum: 623cb05483de0ceb59da755ce1eb66ce (MD5) Previous issue date: 2004 / Resumo: Este trabalho contribui para a convergência de agentes móveis e agentes inteligentes através da proposta de um framework para incorporar técnicas de Inteligência Artificial (IA) a agentes móveis criados com os principais sistemas de mobilidade contemporâneos baseados em Java. Os requisitos a serem satisfeitos pelo framework são identificados e sua arquitetura é estabelecida. Um dos principais mecanismos de IA, o mecanismo de inferência com encadeamento progressivo baseado em regras, é implementado de acordo com o framework sugerido. Uma metodologia de desenvolvimento de software orientada a objetos e vários padrões de projeto são utilizados na concepção tanto do framework quanto do mecanismo de inferência. Os modelos resultantes são documentados através da Linguagem Unificada de Modelagem (UML) e as principais decisões de projeto, na forma de diretrizes a serem adotadas na criação de outros mecanismos. A proposta é avaliada através da construção de agentes móveis controlados pelo mecanismo desenvolvido e pelo levantamento do custo de transporte de seu código e dados. Os resultados mostram que o framework é viável e que o custo de transporte do mecanismo implementado é bem menor que o dos equivalentes encontrados na literatura / Abstract: This thesis contributes for the convergence of mobile and intelligent agents by proposing a framework for embedding Artificial Intelligence (AI) techniques in mobile agents built with the main actual Java-based mobile agent systems. The requirements to be satisfied by the framework are identified and its architecture is established. One of the most essential AI engines, the rule-based forward-chaining inference engine is implemented in agreement with the suggested framework. An object-oriented software development methodology and several design patterns are used in the conception of both, the framework and the inference engine. The resulting models are documented using the Unified Modeling Language (UML) and the main design decisions, as directions to be adopted in the development of other engines. The proposal is evaluated by the construction of mobile agents controlled by the developed engine and by the estimation of the transportation cost of the engine¿s code and data. The results show the framework is feasible and that the transportation cost of the implemented engine is much lower than the cost of similar engines found in literature / Doutorado / Engenharia de Computação / Doutor em Engenharia Elétrica

Orientador: Mauricio Ferreira Magalhães / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-04T04:09:19Z (GMT). No. of bitstreams: 1 Guimaraes_ElianeGomes_D.pdf: 1203376 bytes, checksum: 8baa98d5b0b9753d8a292e0c940b5f41 (MD5) Previous issue date: 2004 / Resumo: Esta tese descreve CM-tel, um modelo de componentes para aplicações telemáticas e ubíquas. CM-tel é neutro em termos de tecnologia, sendo especificado por meio da linguagem UML (Unified Modeling Language). Componentes CM-tel são capazes de executar em plataformas destinadas tanto a computadores tradicionais quanto a dispositivos com limitado poder computacional tais como dispositivos móveis. CM-tel define os três tipos de interfaces prescritas pelo Modelo de Referência para Processamento Distribuído Aberto (RM-ODP), as interfaces operacional, de sinal e de fluxo contínuo. Interfaces de fluxo contínuo são fundamentais para o desenvolvimento de aplicações telemáticas. A arquitetura do contêiner CM-tel integra componentes e agentes móveis em um único ambiente computacional. Esta integração permite que aplicações implementem suas funcionalidades combinando componentes e agentes móveis. Esta tese propõe ainda uma arquitetura para plataformas de software que suportam o modelo CM-tel. A arquitetura utiliza XSLT (XML Stylesheet Language Transformation) para transformação de modelos e geração de código. Uma plataforma baseada na tecnologia CORBA (Common Object Request Broker Architecture) e uma aplicação na área de laboratórios virtuais foram implementadas com a finalidade de avaliar o modelo CM-tel / Abstract: This thesis describes CM-tel, a component model for telematic and ubiquitous applications. CMtel is neutral in terms technology and is specified through the Unified Modeling Language (UML). CM-tel components can execute on platforms targeted to both conventional computers and devices with limited computing power such as mobile devices. CM-tel defines the three types of interfaces prescribed by the Reference Model for Open Distributed Processing (RM-ODP), the operational, signal, and stream interfaces. Stream interfaces are central to the development of telematic applications. The CM-tel container architecture integrates both components and mobile agents into a single computing environment. This integration allows applications to implement their functionalities by combining components and mobile agents. This thesis also proposes an architecture for software platforms supportting the CM-tel component model. The architecture relies on XSLT (XML Stylesheet Language Transformation) for model transformation and code generation. A platform based on the CORBA (Common Object Request Broker Architecture) technology and an application in the field of virtual laboratories were implemented in order to assess the CM-tel component model / Doutorado / Engenharia de Computação / Doutor em Engenharia Elétrica