Virtual Private Network

A virtual private network (VPN) is a technology for using the Internet or another intermediate network to connect computers to isolated remote computer networks that would otherwise be inaccessible. A VPN provides security so that traffic sent through the VPN connection stays isolated from other computers on the intermediate network. VPNs can connect individual users to a remote network or connect multiple networks together.

For example, users may use a VPN to connect to their work computer terminal from home and access their email, files, images, etc.

Through VPNs, users are able to access resources on remote networks, such as files, printers, databases, or internal websites. VPN remote users get the impression of being directly connected to the central network via a point-to-point link.

Virtual private networks have existed for many years in the form of private networks using frame relay. IP-VPNs have become more prevalent due to significant cost-reductions, increased bandwidth, convenience and security.

Types of VPN

VPNs can be either remote-access (connecting an individual computer to a network) or site-to-site (connecting two networks together). In a corporate setting, remote-access VPNs allow employees to access their company's intranet from home or while traveling outside the office, and site-to-site VPNs allow employees in geographically separated offices to share one cohesive virtual network. A VPN can also be used to interconnect two similar networks over a dissimilar middle network; for example, two IPv6 networks over an IPv4 network.

VPN systems can be classified by:

• the protocols used to tunnel the traffic
• the tunnel's termination point, i.e., customer edge or network-provider edge
• whether they offer site-to-site or remote-access connectivity
• the levels of security provided
• the OSI layer they present to the connecting network, such as Layer 2 circuits or Layer 3 network connectivity