The buzzword of this decade has been convergence. Thus the future Next Generation Mobile Network (NGMN) is envisioned as a group of co-existing heterogeneous wireless mobile data networking technologies sharing a common Internet Protocol (IP) based backbone. In such all-IP based heterogeneous networking environments, ongoing sessions are subjected to frequent vertical handoffs. Therefore, ensuring uninterrupted service continuity during session handoffs requires successful architectures, protocols, and standards to be implemented in these participating access networks. This book introduces a common interworking framework for ensuring seamless service continuity over dissimilar networks. Hence the key features of this book can be stated as: to propose a mobility-aware novel architecture for interworking between heterogeneous mobile data networks and to propose a framework for facilitating unified real-time session management across these different networks. This book is aimed towards a broad audience of engineers, researchers, and graduate students in the areas of mobile and wireless communications.