Reliability simulation of component-based software systems

Prevalent Markovian and semi Markovian methods to predict the reliability and performance of component based heterogeneous systems suffer from several limitations: they are subject to an intractably large state space for more complex scenarios, and they cannot take into account the influence of various parameters such as reliability growth of individual components, dependencies among components, etc., in a single model. Discrete event simulation offers an alternative to analytical models as it can capture a detailed system structure, and can be used to study the influence of different factors separately as well as in a combined fashion on dependability measures. We demonstrate the flexibility offered by discrete event simulation to analyze such complex systems through two case studies, one of a terminating application, and the other of a real time application with feedback control. We simulate the failure behavior of the terminating application with instantaneous as well as explicit repair. We also study the effect of having fault tolerant configurations for some of the components on the failure behavior of the application. In the second case of the real time application, we initially simulate the failure behavior of a single version taking into account its reliability growth. We also study the failure behavior of three fault tolerant systems: DRB, NVP and NSCP which are built from the individual versions of the real time application. Results demonstrate the flexibility offered by simulation to study the influence of various factors on the failure behavior of the applications for single as well as fault tolerant configurations