Gerardo Rubino is a Senior Researcher at INRIA, France, where he is the scientific leader of the Dionysos team working on the design and the analysis of communication systems. His main research interests are in the quantitative analysis of computer and communication systems through the use of associated stochastic models. Bruno Sericola is a Senior Researcher at INRIA, France. His main research activity is in computer and communication systems performance evaluation, dependability and performability analysis of fault-tolerant systems and applied stochastic processes.