A virtual private network (VPN) can be defined as an on-demand connection between two computers in different locations. The VPN consists of the two computers (one computer at each end of the connection) and a route, or tunnel, over the public or private network. To ensure privacy and secure communication, data transmitted between the two computers is encrypted by the Point-to Point Protocol (PPP) (a remote access protocol) and then routed over a previously established dial-up or LAN connection by a PPTP device. In Windows NT and Windows 95 terminology, this device is referred to as a virtual private network or VPN.
PPTP uses the VPN device to establish and maintain private, secure communication between computers. It does this by using Remote Access Service (RAS) and Dial-Up Networking to communicate over dial-up lines and public and private networks.
You can use PPTP in the following three scenarios:
· In the most common scenario, you can connect your workstation to a remote network by making a Dial-Up Networking connection to an Internet Service Provider (ISP) and then tunneling through the Internet to a PPTP server that is attached to both the Internet and to the remote network. Once you are connected to the PPTP server, you can transparently access any public or private network that is connected to it.
· If you have a permanent IP connection to a PPTP tunnel server, you can use Dial-Up Networking to connect directly to that tunnel server. You can then use that PPTP server to tunnel to any public or private network that is connected to it.
· Some ISPs are introducing a service that automatically tunnels your traffic to a PPTP server on a remote network. If your ISP supports this service, you can use Dial-Up Networking to make a dial-up connection to the ISP’s PPTP tunnel server. You can then use that tunnel server to tunnel to any public or private network that is connected to it.