A fundamental and comprehensive framework for network security designed for military, government, industry, and academic network personnel. Scientific validation of "security on demand" through computer modeling and simulation methods. The book presents an example wherein the framework is utilized to integrate security into the operation of a network. As a result of the integration, the inherent attributes of the network may be exploited to reduce the impact of security on network performance and the security availability may be increased down to the user level. The example selected is the ATM network which is gaining widespread acceptance and use.