This book gives a hands-on view of exactly what needs to be done by IP Multimedia Subsystem application developers to develop an application and take it "live" on an operator's network. It offers practical guidance on building innovative applications using the features and capabilities of the IMS network, and shows how the rapidly changing development environment is impacting on the business models employed in the industry and how existing network solutions can be moved towards IMS. Elaborating on how IMS applies basic VoIP principles and techniques to realize a true multi-access and multimedia network, this book ensures that developers know how to use IMS most effectively for applications.