Microsoft® Windows® 2000 Security Handbook

Why Use a VPN?

Until recently, there has been a pretty clear division between a private network (such as a frame relay network for a corporate WAN) and a public network (the Internet). Everyone knew that to tie branch offices together, you went to a telecommunications provider, bought your T-1s, and created your internal network. If you were very lucky, your IT department would have one or two sites connected to the Internet and protected by an industrial-strength firewall. These days, with the explosion of high-speed, low-cost Internet connections, telecommuting, and a need to control costs, people are looking to do more with the Internet than just get their email and surf the Web.

A VPN is a mechanism for providing secure, encrypted communications ...