Windows XP Unwired

Virtual Private Networks

Imagine you are out of the office and need to access a printer or file server on the office network. Unless you dial in to the company’s server, it is not possible for you to access the resources in the office. Moreover, using a dial-up line is not a cheap alternative (despite the slow speed), especially if you are overseas.

A Virtual Private Network (VPN) allows you to establish a secure, encrypted connection to the office’s network, all through a public network such as the Internet. Using a VPN, you can work as though you are connected to your company’s network.

There are two main types of VPN:

User-to-Network

This type allows a client to use a VPN to connect to a secure network, such as a corporate intranet.

Network-to-Network

This type connects two networks via a VPN connection. This effectively combines two disparate networks into one, eliminating the need for a Wide Area Network (WAN).

Tunneling

Tunneling is the process of encapsulating packets within other packets to protect their integrity and privacy during transit. A tunnel performs such tasks as encryption, authentication, packet forwarding, and masking of IP private addresses. Figure 4-1 shows a tunnel established between two computers through the Internet. Think of a tunnel as a private link between the two computers: whatever one sends to another is only visible to the other, even though it is sent through a public network like the Internet.

Figure 4-1. A tunnel established between two computers ...