A virtual private network (VPN) is a technology that creates a safe and encrypted connection over a less secure network, such as the internet. VPN technology was developed as a way to allow remote users and branch offices to securely access corporate applications and other resources. To ensure safety, data travels through secure tunnels and VPN users must use authentication methods -- including passwords, tokens and other unique identification methods -- to gain access to the VPN.
The benefit of using a secure VPN is it ensures the appropriate level of security to the connected systems when the underlying network infrastructure alone cannot provide it. The justification for using VPN access instead of a private network usually boils down to cost and feasibility: It is either not feasible to have a private network -- e.g., for a traveling sales rep -- or it is too costly to do so.
VPN performance can be affected by a variety of factors, among them the speed of users' internet connections, the types of protocols an internet service provider may use and the type of encryption the VPN uses. Performance can also be affected by poor quality of service and conditions that are outside the control of IT.
There are several different protocols used to secure and encrypt users and corporate data:
IP security (IPsec)
Secure Sockets Layer (SSL) and Transport Layer Security (TLS)
Point-To-Point Tunneling Protocol (PPTP)
Layer 2 Tunneling Protocol (L2TP)
The most common types of VPNs are remote-access VPNs and site-to-site VPNs.