Analysis of group communication protocols to assess quality of service properties

This paper focuses on a QoS analysis carried out through analytical modelling and experimental evaluation. QoS is defined as a set of qualitative and quantitative characteristics of a (sub)system, which are necessary for obtaining the required functionality of an application. Its 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 to the user requirements. In this paper, we concentrate on a family of group communication protocols in a wireless environment, which is used as the reference system to which the QoS analysis is applied. Specific indicators have been defined and evaluated, which capture the main characteristics of the protocols and of the environment, focusing our attention on performance and dependability attributes. The model-based analysis is devoted to give an estimate of the coverage of the protocol assumptions and performance. We integrate the analytical modelling with fine-grained experimental measurements to determine realistic parameters of message delays and messages losses, and we compare the measured protocol performance with the analytical results. The main purpose of our analysis is to provide a fast, cost-effective and formally sound way to further analyse and understand the protocol behaviour and its environment.