Demystifying VPN is intended to help those individuals with little or no knowledge of internetworking understand VPNs and how they fit into the overall networking environment that includes TCP/IP. The material is presented in a logical fashion, beginning with the basic business reasons for selecting VPNs as a communications solution to the fundamentals of networking and the complexities of VPNs. The material also focuses on the Transmission Control Protocol and Internet Protocol that form the software platform on which VPNs are based, and the Point-to-Point Tunneling Protocol, which is the network protocol supporting VPNs.