Processes in parallel applications running on high-performance computing (HPC) clusters communicate extensively with each other through the interconnection network. Therefore, the interconnection networks and their communication system software play a significant role in the performance of such clusters. This book studies a number of high-speed interconnects from different perspectives. It first evaluates the basic performance metrics of these interconnects, namely latency, bandwidth, and memory registration overheads. Then, some internal characteristics of their Message Passing Interface (MPI) implementations such as queue usage and buffer re-use effect. In addition, VANETS (Vehicular Ad-hoc Networks) are a form of MANETs (Mobile Ad-hoc Networks) that provide communication between vehicles and a fixed equipment or among nearby vehicles. This book focuses on the simulations of VANETs in the most possible realistic environments. Furthermore, spatial distribution models, like Poisson, binomial, and negative binomial functions have no power to predict spatial distribution. This book aims to develop some models, and use these models to describe or predict spatial distribution of arthropods. Other chapters in this book examine cluster analysis in a very general situation, in presence of mixed variables and replicates, present a linear pipeline scheme for image compositing in parallel visualisation to support efficient image delivery to remote client, and provide a qualitative and quantitative comparison among the various protocols, from which future research studies are indicated.