A virtual private network (VPN) extends a private network across a public network and enables users to send and receive data across shared or public networks as if their computing devices were directly connected to the private network. Applications running on an end system (PC, smartphone, etc.) across a VPN may, therefore, benefit from the functionality, security, and management of the private network. Encryption is a common, though not an inherent, part of a VPN connection.[1]
VPN technology was developed to allow remote users and branch offices to access corporate applications and resources. To ensure security, the private network connection is established using an encrypted layered tunneling protocol, and VPN users use authentication methods, including passwords or certificates, to gain access to the VPN. In other applications, Internet users may secure their connections with a VPN to circumvent geo-restrictions and censorship or to connect to proxy servers to protect personal identity and location to stay anonymous on the Internet. Some websites, however, block access to known VPN technology to prevent the circumvention of their geo-restrictions, and many VPN providers have been developing strategies to get around these blockades.
A VPN is created by establishing a virtual point-to-point connection through the use of dedicated circuits or with tunneling protocols over existing networks. A VPN available from the public Internet can provide some of the benefits of a wide area network (WAN). From a user perspective, the resources available within the private
VPN systems may be classified by:
  • the tunneling protocol used to tunnel the traffic
  • the tunnel's termination point location, e.g., on the customer edge or network-provider edge
  • the type of topology of connections, such as site-to-site or network-to-network
  • the levels of security provided
  • the OSI layer they present to the connecting network, such as Layer 2 circuits or Layer 3 network connectivity
  • the number of simultaneous connections