Reusability and hierarchical simulation modeling of communication systems for performance evaluation: Simulation environment, basic and generic models, transfer protocols

The main contribution of this thesis is the emphasis made on the reusability concept, on one side, for designing a simulation environment, and on the other side, for defining two different levels of granularity for reusable network component libraries.

The design of our simulation environment, called AMS for Atelier for Modeling and Simulation, was based on existing pieces of software, which proved their usefulness in their respective fields. In order to carry out this integration efficiently, a modular structure of the atelier was proposed. The structure has been divided into four phases. Each phase is responsible of a part of the performance evaluation cycle. The main novelty of this structure is the usage of a dedicated language as a means to define a clear border between the editing and simulation phases and to allow the portability of the atelier upon different platforms. A prototype of the atelier has been developed on a SUN machine running the SunOs operating system. It is developed in C language.

The kernel of the AMS is its library of Detailed Basic Models (DBMs). Each DBM was designed in order to comply with the most important criterion which is reusability. Indeed, each DBM can be used in aeveral network architectures and can be a component of generic and composite models. Before the effective usage of a DBM, it is verified and validated in order to increase the model credibility. The most important contribution of this research is the definition of a methodology for modeling protocol entities as DBMs. We then tried to partly bridge the gap between specification and modeling. This methodology is based on the concept of function. Simple functions are modeled as reusable modules and stored into a library. The Function Based Methodology was designed to help the modeler to build efficiently and rapidly new protocols designed for the new generation of networks where several services can be provided. These new protocols can be dynamically tailored to the user' s requirements.