Study of fault-tolerant software technology

Presented is an overview of the current state of the art of fault-tolerant software and an analysis of quantitative techniques and models developed to assess its impact. It examines research efforts as well as experience gained from commercial application of these techniques. The paper also addresses the computer architecture and design implications on hardware, operating systems and programming languages (including Ada) of using fault-tolerant software in real-time aerospace applications. It concludes that fault-tolerant software has progressed beyond the pure research state. The paper also finds that, although not perfectly matched, newer architectural and language capabilities provide many of the notations and functions needed to effectively and efficiently implement software fault-tolerance

Explicit Representation of Exception Handling in the Development of Dependable Component-Based Systems

Exception handling is a structuring technique that facilitates the design of systems by encapsulating the process of error recovery. In this paper, we present a systematic approach for incorporating exceptional behaviour in the development of component-based software. The premise of our approach is that components alone do not provide the appropriate means to deal with exceptional behaviour in an effective manner. Hence the need to consider the notion of collaborations for capturing the interactive behaviour between components, when error recovery involves more than one component. The feasibility of the approach is demonstrated in terms of the case study of the mining control system

Application-level fault tolerance in real-time embedded systems

Critical real-time embedded systems need to make use of fault tolerance techniques to cope with operation time errors, either in hardware or software. Fault tolerance is usually applied by means of redundancy and diversity. Redundant hardware implies the establishment of a distributed system executing a set of fault tolerance strategies by software, and may also employ some form of diversity, by using different variants or versions for the same processing. This work proposes and evaluates a fault tolerance framework for supporting the development of dependable applications. This framework is build upon basic operating system services and middleware communications and brings flexible and transparent support for application threads. A case study involving radar filtering is described and the framework advantages and drawbacks are discussed.Fundação para a Ciência e a Tecnologia (FCT

Improving The Fault Tolerance of Ad Hoc Routing Protocols using Aspect-oriented Programming

[ES] Las redes ad hoc son redes inalámbricas distribuidas formadas por nodos móviles que se ubican libremente y dinámicamente, capaces de organizarse de manera propia en topologías arbitrarias y temporales, a través de la actuación de los protocolos de encaminamiento. Estas redes permiten a las personas y dispositivos conectarse sin problemas rápidamente, en áreas sin una infraestructura de comunicaciones previa y con un bajo coste. Muchos estudios demuestran que los protocolos de encaminamiento ad hoc se ven amenazados por una variedad de fallos accidentales y maliciosos, como la saturación de vecinos, que puede afectar a cualquier tipo de red ad hoc, y el ruido ambiental, que puede afectar en general a todas las redes inalámbricas. Por lo tanto, el desarrollo y la implementación de estrategias de tolerancia a fallos para mitigar el efecto de las fallos, es esencial para el uso práctico de este tipo de redes. Sin embargo, los mecanismos de tolerancia a fallos suelen estar implementados de manera específica, dentro del código fuente de los protocolos de encaminamiento que hace que i) ser reescrito y reorganizado cada vez que una nueva versión de un protocolo se libera, y ii) tener un carácter completamente remodelado y adaptado a las nuevas versiones de los protocolos. Esta tesis de máster explora la viabilidad de utilizar programación orientada a aspectos (AOP), para desarrollar e implementar los mecanismos de tolerancia a fallos adecuados para toda una familia de protocolos de encaminamiento, es decir, las versiones actuales y futuras de un protocolo determinado (OLSR en este caso). Por otra parte, se propone una nueva metodología para ampliar estos mecanismos a diferentes familias de protocolos proactivos (OLSR, BATMAN y Babel) con un nuevo concepto de AOP, el metaaspecto. La viabilidad y efectividad de la propuesta se ha evaluado experimentalmente, estableciendo así un nuevo método para mejorar la implementación de la portabilidad y facilidad de mantenimiento de los mecanismos de tolerancia a fallos en los protocolos de enrutamiento ad hoc y, por lo tanto, la fiabilidad de las redes ad hoc.[EN] Ad hoc networks are distributed networks consisting of wireless mobile nodes that can freely and dynamically self-organize into arbitrary and temporary topologies, through the operation of routing protocols. These networks allow people and devices to seamlessly interconnect rapidly in areas with no pre-existing communication infrastructure and with a low cost. Many studies show that ad hoc routing protocols are threatened by a variety of accidental and malicious faults, like neighbour saturation, which may affect any kind of ad hoc network, and ambient noise, which may impact all wireless networks in general. Therefore, developing and deploying fault tolerance strategies to mitigate the effect of such faults is essential for the practical use of this kind of networks. However, those fault tolerance mechanisms are usually embedded into the source code of routing protocols which causes that i) they must be rewritten and redeployed whenever a new version of a protocol is released, and ii) they must be completely redeveloped and adapted to new routing protocols. This master thesis explores the feasibility of using Aspect-Oriented Programming (AOP) to develop and deploy fault tolerance mechanisms suitable for a whole family of routing protocols, i.e. existing and future versions of a given protocol (OLSR in this case). Furthermore, a new methodology is proposed to extend these mechanisms to different families of proactive protocols (OLSR, B.A.T.M.A.N and Babel) using a new concept in AOP, the meta-aspect. The feasibility and effectiveness of the proposal is experimentally assessed, thus establishing a new method to improve the deployment, portability, and maintainability of fault tolerance mechanisms for ad hoc routing protocols and, therefore, the dependability of ad hoc networks.Bustos Rodríguez, AJ. (2012). Improving The Fault Tolerance of Ad Hoc Routing Protocols using Aspect-oriented Programming. http://hdl.handle.net/10251/18421Archivo delegad