Introduction to Network Security maintains its focus on the network and its vulnerabilities, protocols, and security solutions. This book discusses network architecture, the functions of layers in a typical network, and network based attacks including header, protocol, and authentication attacks. Using a bottom-up approach, it provides understanding of the vulnerabilities and mechanisms of each layer of network security. A define-attack-defend methodology is used throughout the text to introduce relevant protocols. It also presents homework problems, laboratory experiments, and appendices that demonstrate how to develop a low cost lab environment and that offer an overview of cryptology.