Multilevel secure mixed-media communication networks

A communication system architecture that provides security for different groups of users while allowing each group access to a common pool of network and transmission assets is presented. Transmission assets can be mixed, operating with different propagation media and network protocols. Placement of encryption processes required to support security services is of particular interest. Support of secure relaying services within and between networks, separation of user groups, and security against denial-of-service threats are provided. The architecture has applicability to problems of current interest in mobile and military communications