QoS analysis of group communication protocols in wireless environment

QoS analysis is a necessary step for the early verification and validation of an appropriate design, and for taking design decisions about the most rewarding choice, in relation with user requirements. The area of distributed applications, whose development is increasing more and more, favoured by the high connectivity provided by advanced Internet and Web technologies, poses special challenges in this respect. In this chapter, we describe an analytical approach for the evaluation of the QoS offered by two group communication protocols in a wireless environment. Experimental data are used both to feed the models and to validate them. Specific performance and dependability related indicators have been defined and evaluated. To improve the utility of our study, we analysed the protocols taking into account relevant phenomena affecting the environment in which such protocols are called to operate. Specifically, the fading phenomenon and the user mobility have been explicitly introduced in our models, to evaluate their impact on the correlation among successive packet transmissions. Also, in order to enhance the correctness of the derived models, a formal description of the protocols has been performed, adopting the timed asynchronous system model. The aim of this work is to provide a fast, cost effective, and formally sound way to analyse and understand protocols behaviour and their environment.