The Internet is one of the great technology success stories of the twentieth century, enabling greater access to information and providing new modes of communication among people and organizations. Unfortunately, the Internet's very success is now creating obstacles to innovation in the networking technology that lies at its core. In order to free the global communications infrastructure from stagnation, the nation must find ways to enable its continuing renewal. This planning grant is developing a case for network virtualization as a means to enable innovation in networks and services. Virtualization allows multiple logically independent virtual networks to share a common physical infrastructure or substrate. This program is developing a plan for a major new research initiative in network virtualization that includes both basic research, the development of key technology components and the creation of an experimental test bed, to establish feasibility and provide a context in which networking researchers can develop innovative new network architectures and services. The program is articulating the case for network virtualization, soliciting input from the network research community and working with the community to develop recommendations to NSF for a major initiative in this area.