Windows administrators are smack-dab in the middle of a challenging security balancing act: how to enable easy access to resources while still meeting ever-increasing information and network security requirements. As this feature describes, a great way to help strike the appropriate balance between access and security is to shift from traditional connectivity models to one that seeks to define network access in a more logical and policy-centric fashion.
Full Article – http://blogs.technet.com/tnmag/archive/2008/03/25/policy-driven-network-access-with-windows-server-2008.aspx