VPNs Illustrated: Tunnels, VPNs, and IPsec

1. Introduction

1.1 Purpose

This book focuses on the technology behind tunneling and virtual private networks (VPNs). The explosive growth of the Internet and the buildout of the underlying infrastructure have led many enterprises to replace their private networks based on leased lines with far cheaper solutions based on the public Internet. Although the cost savings are substantial, using the Internet to carry sensitive information presents serious privacy and security problems. One way of addressing these problems is to create private, virtual networks within the Internet structure. These virtual networks are created by using tunneling, authentication, and encryption to provide a virtual leased line between enterprise networks. Because ...