Secured networks are usually implemented in hardware that delivers security at a level below the network layer. VPNs act in the network layer and so can utilize any security built into a network. But a VPN should be designed to function without any reliance on the network's assumed security.

There has been some confusion about the difference between a VPN and a DPN. A dedicated private network (DPN) is simply a wide area network (WAN) that has specifiable data paths. If one built a local area network (LAN) with an ATM switch instead of a wiring hub, that would be a DPN. DPNs have data paths that can be specified, and may differ from the physical wiring. This means fewer patch panels, but nothing for the overall system security.