Virtual Private Networks (VPN)

1. what is VPN?
A virtual private network extends a private network across a public network, and enables users to send and receive data across shared or public networks as if their computing devices were directly connected to the private network.

Types of VPNs.
 WAN VPN: Branch offices
 Access VPN: Roaming Users

 Extranet VPNs: Suppliers and Customers.

What Makes a VPN?
There are two common types of VPNs.
Remote−Access-
Also called a Virtual Private Dial−up Network (VPDN), this is a user−to−LANconnection 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 telecommuters 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.
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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 further categorized into intranets or extranets. A site−to−site VPN built between offices of the same company is said to be an intranet VPN, while a VPN built to connect the company to its partner or customer is referred to as an extranet VPN.