Vpn

An Introduction

Until recently, reliable communication has meant the use of leased lines to maintain a Wide Area Network (WAN). Leased lines, ranging from Integrated Services Digital Network (ISDN, which runs at 144 Kbps) to Optical Carrier-3 (OC3, which runs at 155 Mbps) fiber, provide a company with a way to expand their private network beyond their immediate geographic area. A WAN has obvious advantages over a public network like the Internet when it comes to reliability, performance, and security, but maintaining a WAN, particularly when using leased lines, can become quite expensive (it often rises in cost as the distance between the offices increases).

As the popularity of the Internet has grown, businesses have turned to it as a means of extending their own networks. First came intranets, which are sites designed for use only by company employees. Now, many companies are creating their own Virtual Private Networks (VPNs) to accommodate the needs of remote employees and distant offices.

A typical VPN might have a main Local Area Network (LAN) at the corporate headquarters of a company, other LAN's at remote offices or facilities, and individual users connecting from out in the field.

Basically a VPN is a private network that uses a public network (usually the Internet) to connect remote sites or users together. Instead of using a dedicated, real-world connection, such as leased line, a VPN uses "virtual" connections routed through the Internet from the company's private network to the remote site or employee.

What Makes a VPN?

There are two common types of VPNs:

1. Remote-Access

Also called a Virtual Private Dial-up Network (VPDN), this is a user-to-LAN connection used by a company that has employees who need to connect to the private network from various remote locations. Typically, a corporation that wishes to set up a large remote-access VPN provides some form of Internet dial-up account to their users using an Internet Service Provider (ISP). The telecommuter can then dial a 1-800 number to reach the Internet and use their VPN client software to access the corporate network. A good example of a company that needs a remote-access VPN would be a large firm with hundreds of sales people in the field. Remote-access VPNs permit secure, encrypted connections between a company's private network and remote users through a third- party service provider.

2. Site-to-Site

Through the use of dedicated equipment and large-scale encryption, a company can connect multiple fixed sites over a public network such as the Internet. Each site needs only a local connection to the same public network, thereby saving money on long private leased- lines. Site-to-site VPNs can be built between offices of the same company, or, for example, to an external supplier to share a database for product ordering.

A well-designed VPN can greatly benefit a company. For example, it can do the following:

o Extend geographic connectivity ? Extend geographic connectivity

o Reduce operational costs versus traditional WANs

o Reduce transit times and traveling costs for remote users

o Improve productivity

o Simplify network topology

o Provide global networking opportunities

o Provide telecommuter support

o Provide faster Return On Investment (ROI) than traditional WAN

A well-designed VPN should incorporate the following:

o Security

o Reliability

o Scalability

o Network Management

o Policy Management

Analogy: Each LAN Is an IsLANd

Imagine that you live on an island in a huge ocean. There are thousands of other islands all around you, some very close and others farther away. The normal way to travel is to take a ferry from your island to whichever island you wish to visit. Of course, traveling on a ferry means that you have almost no privacy. Anything you do can be seen by someone else.

Let's say that each island represents a private LAN and the ocean is the Internet. Traveling by ferry is like connecting to a Web server or to another other device through the Internet. You have no control over the wires and routers that make up the Internet, just like you have no control over the other people on the ferry. This leaves you susceptible to security issues if you are trying to connect between two private networks using a public resource.

Continuing with our analogy, your island decides to build a bridge to another island so that there is an easier, more secure and direct way for people to travel between the two. It is expensive to build and maintain the bridge, even though the island you are connecting with is very close. But the need for a reliable, secure path is so great that you do it anyway. Your island would like to connect to a second island that is much farther away, but you decide that the cost are simply too much to bear.

This situation is very much like having a leased line. The bridges (leased lines) are separate from the ocean (Internet), yet they are able to connect the islands (LAN's). Many companies have chosen this route because of the need for security and reliability in connecting their remote offices; however, if the offices are very far apart, the cost can be prohibitively high - just like trying to build a bridge that spans a great distance.

So how does VPN fit in to this analogy? We could give each inhabitant of our islands their own small submarine with the following amazing properties:

o It's fast.

o It's easy to take with you wherever you go.

o It's able to completely hide you from any other boats or submarines.

o It's dependable.

o It costs little to add additional submarines to your fleet once the first is purchased.

Although they