Book excerpt: The convergence of two powerful technologies—wireless and the Internet—through IPv4/v6 protocol has led to emergence of next-generation networks (NGNs). NGN is no more a network of mere computers but a connected conglomeration of varied networks with diverse physical properties, with a plethora of network elements, along with a variety of real-time multimedia applications. This book covers the entire gamut of technology challenges from physical layer to application layer including security from both academic and industrial perspectives.