Introduction

As you progress through this chapter, you will understand the concepts of virtual private networks (VPNs), how VPNs operate, and how to implement VPN tunnels using Internet Protocol Security (IPSec) on NetScreen appliances. A VPN is a means of creating secure communications over a public or insecure network infrastructure. VPNs use encryption and authentication to ensure that information is kept private and confidential. This means that you can share data and other network resources among two or more locations without the worry of the data or its integrity being compromised.

The primary advantage of a VPN is its capability to make use of an insecure public network infrastructure to create a private and secure network. The most common method of deployment is over the public Internet. Today fast, cheap, and fairly reliable Internet access is available almost anywhere. Organizations are widely replacing legacy frame relay and point-to-point networks with VPNs deployed over the public Internet. This provides several advantages when compared to legacy networks including cost savings, increased bandwidth, and additional redundancy. Without using the Internet as a transport mechanism, you would have to purchase point-to-point circuits or some other form of leased line to connect multiple locations. Leased lines are traditionally expensive to operate, especially if the two points being connected are across a large geographic region. Using VPNs instead of leased lines reduces the operating cost for your company. VPNs enable connectivity where leased line access just isn t possible or cost justified. Companies today need global connectivity.