Platform-independent Dynamic Reconfiguration of Distributed Applications

The aim of dynamic reconfiguration is to allow a system to evolve incrementally from one configuration to another at run-time, without restarting it or taking it offline. In recent years, support for transparent dynamic reconfiguration has been added to middleware platforms, shifting the complexity required to enable dynamic reconfiguration to the supporting infrastructure. These approaches to dynamic reconfiguration are mostly platform-specific and depend on particular implementation approaches suitable for particular platforms. In this paper, we propose an approach to dynamic reconfiguration of distributed applications that is suitable for application implemented on top of different platforms. This approach supports a platform-independent view of an application that profits from reconfiguration transparency. In this view, requirements on the ability to reconfigure components are expressed in an abstract manner. These requirements are then satisfied by platform-specific realizations

Performance Evaluation of CORBA Concurrency Control Service Using Stochastic Petri Nets

The interest in performance evaluation of middleware systems is increasing. Measurement techniques are still predominant among those used to carry out performance evaluation. However, performance models are currently being defined due to their flexibility, precision and facilities to carry out capacity planning activities. This paper presents stochastic Petri net models for performance evaluation of the CORBA Concurrency Control Service (CCS), which mediates concurrent access to objects. In order to validate the proposed models, CCS performance results obtained using those models are then compared against ones obtained through actual measurements.The interest in performance evaluation of middleware systems is increasing. Measurement techniques are still predominant among those used to carry out performance evaluation. However, performance models are currently being defined due to their flexibility, precision and facilities to carry out capacity planning activities. This paper presents stochastic Petri net models for performance evaluation of the CORBA Concurrency Control Service (CCS), which mediates concurrent access to objects. In order to validate the proposed models, CCS performance results obtained using those models are then compared against ones obtained through actual measurements

Dynamic Upgrade of Distributed Software Components

Die Aktualisierung von komplexen Telekommunikationssystemen, die sich durch die ihnen eigene Verteiltheit und hohe Kosten bei System-Nichtverfügbarkeit auszeichnen, ist ein komplizierter und fehleranfälliger Wartungsprozess. Noch stärkere Herausforderungen bergen solche Software-Aktualisierungen, die die Systemverfügbarkeit nicht beeinträchtigen sollen. Dynamic Upgrade ist eine Wartungstechnik, die das Verwalten und die Durchführung von Software-Aktualisierung automatisiert und damit den Betrieb des Systems während der Wartungszeit nicht unterbricht. In dieser Arbeit wird das Dynamic Upgrade als ein Sonderfall der Bereitstellung und Inbetriebnahme (Deployment) von Software betrachtet, in dem Teile der einen Dienst repräsentierenden Software durch neue Versionen im laufenden Betrieb ersetzt werden. Die Problemstellung des Dynamic Upgrade wird anhand einer vom Autor erarbeiteten Taxonomie erläutert, die die Entwurfsmöglichkeiten für ein System zur Unterstützung von Dynamic Upgrade hinsichtlich dreier Systemaspekte klassifiziert: Deployment, Evolution und Zuverlässigkeit (Dependability). Mit Hilfe dieser Taxonomie lassen sich auch andere Systeme zur Unterstützung von Dynamic Upgrade miteinander vergleichen. Aufbauend auf einem ausführlichen Vergleich über existierende Ansätze zur Unterstützung von Dynamic Upgrade, wird in der vorliegenden Arbeit eine Lösung entwickelt und dargestellt, die Dynamic Upgrade in verteilten komponentenbasierten Software-Systemen ermöglicht. Ausgehend von der Problemanalyse wird mit Hilfe des Unified Process ein als Deployment and Upgrade Facility bezeichnetes Modell entwickelt, das sowohl die benötigten Leistungsfähigkeiten eines Dynamic Upgrade unterstützenden Systems als auch Eigenschaften von aktualisierbaren Software-Komponenten beschreibt. Dieses Modell ist Plattform-unabhängig und einsetzbar für mehrere unterliegende Middleware-Technologien. Das Modell wird in einem Java-basierten prototypischen Rahmenwerk programmiert und um plattformspezifische Mechanismen auf der Jgroup/ARM Middleware erweitert. Das Rahmenwerk umfasst allgemeine Entwurfslösungen und ?muster, die sich für die Konstruktion einer Unterstützung für Dynamic Upgrade eignen. Es erlaubt die Kontrolle der Lebenszyklen von Aktualisierungsprozessen und ihre Koordination im Zielsystem. Darüber hinaus definiert es eine Reihe von Unterstützungsmechanismen und Algorithmen für den dynamischen Aktualisierungsprozess, der gegebenenfalls mit unterschiedlichen Zielsetzungen und unter verschiedenen Randbedingungen erfolgen soll. Insbesondere wird ein Aktualisierungsalgorithmus für replizierte Software-Komponenten dargestellt. Das entwickelte Rahmenwerk wird zwecks Plausibilitätsprüfung der dargestellten Ansätze und zur Auswertung der Auswirkungen der Dynamic Upgrade unterstützenden Mechanismen im Hinblick auf Systemperformanz in mehreren Experimenten eingesetzt. Diese quantitative Evaluierung der Experimente führt zu einer Spezifikationen eines einfachen Bewertungsmaßstabs (Benchmark), der sich zum Vergleich von Dynamic Upgrade unterstützenden Systemen eignet.Upgrading complex telecommunication software systems, characterized by their inherent distribution and a very high cost of system unavailability, is a difficult and error-prone maintenance activity. Even more challenging are such software upgrades that do not compromise the system availability. Dynamic upgrades is a technique, which automates performing and managing upgrades so that the software system remains operational during the upgrade time. In this thesis, the dynamic upgrade is considered as a special case of software deployment, in which a running service has to be replaced with its new version. The problems of dynamic upgrades are introduced using a novel taxonomy that classifies the design issues to be solved when building support for dynamic upgrade with regard to three system aspects: deployment, evolution and dependability and provides a reference to comparing other systems supporting dynamic upgrades. An extensive and thorough survey of existing approaches to dynamic upgrades follows and, furthermore, is as a starting point to designing a solution supporting dynamic upgrades in distributed component-based software systems. Derived from the problem analysis, a model called Deployment and Upgrade Facility describing the capabilities needed for managing and performing dynamic upgrades as well as properties of upgradable software components is developed using the Unified Process approach. The model is platform independent and can be used with a range of underlying middleware technologies. The model is implemented in a Java-based prototypical framework and extended with platform specific mechanisms on top of the JGroup/ARM middleware. The framework captures common design solutions and patterns for building a support for dynamic upgrade. The framework allows for controlling life-cycle and coordination of upgrade processes in the system. It also defines a number of supporting mechanisms and algorithms for the upgrade process. A special attention is drawn to an upgrade algorithm for replicated software components for achieving a synergy of replication techniques and dynamic upgrade . The developed framework is used to validate the feasibility of the approach and to measure the overhead of the mechanisms supporting dynamic upgrade with regard to the performance of the system being upgraded in a number of practical experiments. This quantitative evaluation of the experiments leads to a specification of a simple benchmark for systems supporting dynamic upgrades

Distributed control of reconfigurable mobile network agents for resource coordination

Includes abstract.Includes bibliographical references.Considering the tremendous growth of internet applications and network resource federation proposed towards future open access network (FOAN), the need to analyze the robustness of the classical signalling mechanisms across multiple network operators cannot be over-emphasized. It is envisaged, there will be additional challenges in meeting the bandwidth requirements and network management...The first objective of this project is to describe the networking environment based on the support for heterogeneity of network components..

Patterns for Providing Real-Time Guarantees in DOC Middleware - Doctoral Dissertation, May 2002

The advent of open and widely adopted standards such as Common Object Request Broker Architecture (CORBA) [47] has simplified and standardized the development of distributed applications. For applications with real-time constraints, including avionics, manufacturing, and defense systems, these standards are evolving to include Quality-of-Service (QoS) specifications. Operating systems such as Real-time Linux [60] have responded with interfaces and algorithms to guarantee real-time response; similarly, languages such as Real-time Java [59] include mechanisms for specifying real-time properties for threads. However, the middleware upon which large distributed applications are based has not yet addressed end-to-end guarantees of QoS specifications. Unless this challenge can be met, developers must resort to ad hoc solutions that may not scale or migrate well among different platforms. This thesis provides two contributions to the study of real-time Distributed Object Computing (DOC) middleware. First, it identifies potential bottlenecks and problems with respect to guaranteeing real-time performance in contemporary middleware. Experimental results illustrate how these problems lead to incorrect real-time behavior in contemporary middleware platforms. Second, this thesis presents designs and techniques for providing real-time QoS guarantees in DOC middleware in the context of TAO [6], an open-source and widely adopted implementation of real-time CORBA. Architectural solutions presented here are coupled with empirical evaluations of end-to-end real-time behavior. Analysis of the problems, forces, solutions, and consequences are presented in terms of patterns and frame-works, so that solutions obtained for TAO can be appropriately applied to other real-time systems

3D-based Advanced Machine Service Support

In the face of today's unpredictable and fluctuating global market, there have been trends in industry towards wider adoption of more advanced and flexible new generation manufacturing systems. These have brought about new challenges to manufacturing equipment builders/suppliers in respect of satisfying ever-increasing customers' requirements for such advanced manufacturing systems. To stay competitive, in addition to supplying high quality equipment, machine builders/suppliers must also be capable of providing their customers with cost-effective, efficient and comprehensive service support, throughout the equipment's lifecycle. This research study has been motivated by the relatively unexplored potential of integrating 3D virtual technology with various machine service support tools/techniques to address the aforementioned challenges. The hypothesis formulated for this study is that a 3D-based virtual environment can be used as an integration platform to improve service support for new generation manufacturing systems. In order to ensure the rigour of the study, it has been initiated with a two-stage (iterative) literature review, consisting of: a preliminary review for the identification of practical problems/main issues related to the area of machine service support and in-depth reviews for the identification of research problems/questions and potential solutions. These were then followed by iterations of intensive research activities, consisting of: requirements identification, concept development, prototype implementation, testing and exploration, reflection and feedback. The process has been repeated and revised continuously until satisfactory results, required for answering the identified research problems/questions, were obtained. The main focus of this study is exploring how a 3D-based virtual environment can be used as an integration platform for supporting a more cost-effective and comprehensive strategy for improving service support for new generation manufacturing systems. One of the main outcomes of this study is the proposal of a conceptual framework for a novel 3D-based advanced machine service support strategy and a reference architecture for a corresponding service support system, for allowing machine builders/suppliers to: (1) provide more cost-effective remote machine maintenance support, and (2) provide more efficient and comprehensive extended service support during the equipment's life cycle. The proposed service support strategy advocates the tight integration of conventional (consisting of mainly machine monitoring, diagnostics, prognostics and maintenance action decision support) and extended (consisting of mainly machine re-configuration, upgrade and expansion support) service support functions. The proposed service support system is based on the integration of a 3D-based virtual environment with the equipment control system, a re-configurable automated service support system, coupled with a maintenance-support-tool/strategy support environment and an equipment re-configuration/upgrade/expansion support environment, in a network/lntenet framework. The basic concepts, potential benefits and limitations of the proposed strategy/ system have been explored via a prototype based on a laboratory-scale test bed. The prototype consists of a set of integrated modular network-ready software tools consisting of: (1) an integrated 20/30 visualisation and analysis module, (2) support tools library modules, (3) communication modules and (4) a set of modular and re-configurable automated data logging, maintenance and re-configuration support modules. A number of test cases based on various machine service support scenarios, have been conducted using the prototype. The experimentation has shown the potential and feasibility (technical implementation aspects) of the proposed 3D-based approach. This research study has made an original contribution to knowledge in the field of machine service support. It has contributed a novel approach of using a 3D-based virtual environment as an integration platform for improving the capability of machine builders/suppliers in providing more cost-effective and comprehensive machine service support for complex new generation manufacturing systems. Several important findings have resulted from this work in particular with respect to how various 20/30 visualisation environments are integrated with machine service support tools/techniques for improving service support for complex manufacturing systems. A number of aspects have also been identified for future work

Designing an ecology of distributed agents

Thesis (S.M.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 1998.Includes bibliographical references (p. 87-92).by Nelson Minar.S.M

Organization based multiagent architecture for distributed environments

[EN]Distributed environments represent a complex field in which applied solutions should be flexible and include significant adaptation capabilities. These environments are related to problems where multiple users and devices may interact, and where simple and local solutions could possibly generate good results, but may not be effective with regards to use and interaction. There are many techniques that can be employed to face this kind of problems, from CORBA to multi-agent systems, passing by web-services and SOA, among others. All those methodologies have their advantages and disadvantages that are properly analyzed in this documents, to finally explain the new architecture presented as a solution for distributed environment problems. The new architecture for solving complex solutions in distributed environments presented here is called OBaMADE: Organization Based Multiagent Architecture for Distributed Environments. It is a multiagent architecture based on the organizations of agents paradigm, where the agents in the architecture are structured into organizations to improve their organizational capabilities. The reasoning power of the architecture is based on the Case-Based Reasoning methology, being implemented in a internal organization that uses agents to create services to solve the external request made by the users. The OBaMADE architecture has been successfully applied to two different case studies where its prediction capabilities have been properly checked. Those case studies have showed optimistic results and, being complex systems, have demonstrated the abstraction and generalizations capabilities of the architecture. Nevertheless OBaMADE is intended to be able to solve much other kind of problems in distributed environments scenarios. It should be applied to other varieties of situations and to other knowledge fields to fully develop its potencial.[ES]Los entornos distribuidos representan un campo de conocimiento complejo en el que las soluciones a aplicar deben ser flexibles y deben contar con gran capacidad de adaptación. Este tipo de entornos está normalmente relacionado con problemas donde varios usuarios y dispositivos entran en juego. Para solucionar dichos problemas, pueden utilizarse sistemas locales que, aunque ofrezcan buenos resultados en términos de calidad de los mismos, no son tan efectivos en cuanto a la interacción y posibilidades de uso. Existen múltiples técnicas que pueden ser empleadas para resolver este tipo de problemas, desde CORBA a sistemas multiagente, pasando por servicios web y SOA, entre otros. Todas estas mitologías tienen sus ventajas e inconvenientes, que se analizan en este documento, para explicar, finalmente, la nueva arquitectura presentada como una solución para los problemas generados en entornos distribuidos. La nueva arquitectura aquí se llama OBaMADE, que es el acrónimo del inglés Organization Based Multiagent Architecture for Distributed Environments (Arquitectura Multiagente Basada en Organizaciones para Entornos Distribuidos). Se trata de una arquitectura multiagente basasa en el paradigma de las organizaciones de agente, donde los agentes que forman parte de la arquitectura se estructuran en organizaciones para mejorar sus capacidades organizativas. La capacidad de razonamiento de la arquitectura está basada en la metodología de razonamiento basado en casos, que se ha implementado en una de las organizaciones internas de la arquitectura por medio de agentes que crean servicios que responden a las solicitudes externas de los usuarios. La arquitectura OBaMADE se ha aplicado de forma exitosa a dos casos de estudio diferentes, en los que se han demostrado sus capacidades predictivas. Aplicando OBaMADE a estos casos de estudio se han obtenido resultados esperanzadores y, al ser sistemas complejos, se han demostrado las capacidades tanto de abstracción como de generalización de la arquitectura presentada. Sin embargo, esta arquitectura está diseñada para poder ser aplicada a más tipo de problemas de entornos distribuidos. Debe ser aplicada a más variadas situaciones y a otros campos de conocimiento para desarrollar completamente el potencial de esta arquitectura