Network simulation is not just a concept but it's a real time application and totally practically oriented notion so the book primarily focus on basic practical approach to make it a lucid learning stream for readers. The basic notion behind compiling this book is to make students and scholar familiar with network simulation concepts with fundamental details to complex program. Network is amazing or we say network is abstraction. Set up a real network just to learn is not possible: if you want to do networking then you always want to do a demo then make a network which is small and learn from it, how it behave and what happens at each stage. These things happen by constructing a small network. Constructing a small network is expensive and that is very far from a normal person. So construction a real Hardware network for learning is not quite acceptable for many people. So Simulation on internet.