The optimal design and/or selection of a local area network (LAN) is of the utmost importance if the computing facility is to provide the new and improved services. The software tool can be used to model a variety of LAN topologies and control environments as well as the details of the underlying policies and mechanisms that govern LAN operations. The modeler must understand the system in order to provide a faithful perspective of its important features and in order to make the model useful. The process of developing the model from the problem statement is iterative and time-consuming. Analytical implementations of models rely on the ability of the modeler to describe a model in mathematical terms. Test beds are abstractions of systems and are used to study system components and interactions to gain further insight into the essence of the real system. Finally, this chapter also provides an overview of this book.