This book explains how to plan and build a Virtual Private Network (VPN), a collection of technologies that creates secure connections or "tunnels" over regular Internet lines. It discusses costs, configuration, and how to install and use VPN technologies that are available for Windows NT and Unix, such as PPTP and L2TP, Altavista Tunnel, Cisco PIX, and the secure shell (SSH). New features in the second edition include SSH and an expanded description of the IPSec standard.