Linux Firewalls, Third Edition

Overview of Virtual Private Networks

VPN systems are designed to connect two or more devices or networks securely over a public network such as the Internet. A VPN is so named because it is virtual, using an already existing infrastructure; it is private, having the data encapsulated through a secure protocol; and it is a network, because it connects two or more devices or networks together. VPNs are popular today because they provide a better value proposition than setting up individual leased connections between locations, especially for road warriors or other short-lived connections. VPNs can also provide seamless operation. After initial configuration is done, the networks connected with a VPN can operate as if they were one network.