Use public networks to conduct private data communications. Most VPN implementations use the Internet as the public infrastructure, along with some other protocols to ensure private communications through the Internet. VPN typically uses a client-and-server approach.

VPN clients not only encrypt data and authenticate users utilizing a technique called tunneling but also manage sessions with VPN servers. Commonly, VPN clients and servers are used to form an extranet by joining networks between two companies, to support connections between a number of intranets within the same company, and to support remote access to an intranet.

The primary advantage with VPN is the reduced cost required for supporting this technology, relative to traditionally leased lines or remote access servers. Because VPN users normally use simple graphical client tools, these support connecting to and disconnecting from the VPN, creating tunnels, and setting configuration parameters.

VPN solutions use a number of network protocols, including IPsec, L2TP, PPTP, and SOCKS. VPN servers also can directly connect to other VPN servers, extending the intranet or extranet to span many networks.

Because of the very high demand, many vendors have made VPN hardware and software products; unfortunately, some of these do not interoperate because of the lack of maturity of some VPN standards. Moreover, the new generation of SSL-based but not the IPSec-based VPNÂ’s have recently flourished.

See Also: Internet; Internet Protocol Security (IPSec); Intranet; Remote Access; Servers.