Currently, there exist disparate wireless networks, such as Bluetooth for personal areas, wireless LANs (WLANs) for local areas, GSM and UMTS for wide areas. These networks are designed for specific service needs and vary widely in terms of bandwidth, latency, area of coverage, cost, and quality of service (QoS) provisioning. None of the existing wireless systems can simultaneously satisfy the low latency, high bandwidth, and ubiquitous coverage needs of mobile users at low cost. In next generation networks, users will move between these different networks. They want to maintain their ongoing communications while using the best available connection. These heterogeneous networks may or may not belong to the same service provider. Hence, support for smooth handoff between networks of different service providers is required. In this work, we describe the design of a new architecture, namely SeSMo, for fast handoff in heterogeneous environments. Our proposal introduces the use of an intelligent handoff decision mechanism for the discovery and the prediction of future access routers (ARs) and the generation of new session keys.Our architecture has the following characteristics:• Scalable: It should be able to integrate any number of wireless systems of both existing and future service providers.• Transparency to heterogeneous access technologies: The architecture should be transparent to different access technologies of different networks.• Secure: The architecture should be able to provide secure vertical and horizontal handoff.• Seamless mobility support to eliminate connection interruption and QoS degradation during intersystem handoff.