Virtual Private Network (VPN)

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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.

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