"Network Security, Firewalls, and VPNs is written for a course on Network Security and Perimeter Defense, with special emphasis placed on Firewalls and VPNs - two key tools for securing networks. It is currently divided into three parts - Part 1: Foundations of Network Security, Part 2: Technical Overview of Network Security, Firewalls, and VPNs, and Part 3: Implementation, Resources, and the Future"--