VPN is an abbreviation that has been more and more used when the Internet has expanded. The term VPN is used for Virtual Private Network, which mans a net in the network, private confident traffic is transported in a safe way over an public, insecure network.

A popular way to describe VPN is like a "tunnel" between two endpoints. Whereas the IP technology has matured the VPN technology has replaced frame relay, ATM and other switched networks like X.25 and ISDN.

The overwhelming number of implementations of VPN is used to transport traffic over the Internet. The standardized way to do this today is by using IP-sec, a standard description of how to exchange keys, handle certificate and setup a secure encrypted communication between two endpoints. With this method no case of intrusion or fraud identity has been proven.

It is today fully possible to use inexpensive Internet connections and build a VPN network between all of an enterprises different location. The drawback with this method is that all traffic has to pass the central point (main office) in the network, some times even twice which gives that connection an unnecessary large load. However this can be solved by intelligent design.

Another problem with VPN is maintenance where the owner need to maintain and setup hardware around the network. The troubleshooting can also be costly in terms of both money and time. The majority of companies are therefore using telecom operators private virtual networks which are using the same technology but run by a telecom operator.

A standard has emerged in how to build public and private networks for public use. Ethernet (Level 2) is often used as the access method and IP / MPLS in the core network for transporting and separating multiple private networks in a secure way.