VPN (virtual private network)

A virtual private network (VPN) is programming that creates a safe and encrypted connection over a less secure network, such as the internet. VPNs were originally developed to provide branch office employees with safe access to corporate applications and data. Today, VPNs are often used by remote workers and business travelers who require access to sites that are geographically restricted. The two most common types of VPNs are remote access VPNs and site-to-site VPNs. Remote access VPN Remote access VPN clients connect to a VPN gateway on the organization's network. The gateway requires the device to authenticate its identity before granting access to internal network resources such as file servers, printers and intranets. This type of VPN usually relies on either IP Security (IP-sec) or Secure Sockets Layer (SSL) to secure the connection, although SSL VPNs are often focused on supplying secure access to a single application rather than to the entire internal network. Some VPNs provide Layer 2 access to the target network; these require a tunneling protocol like the Point-to-Point Tunneling Protocol or the Layer 2 Tunneling Protocol running across the base IP-sec connection. In addition to IP-sec and SSL, other protocols used to secure VPN connectivity and encrypt data are Transport Layer Security and OpenVPN. Site-to-site VPN In contrast, a site-to-site VPN uses a gateway device to connect an entire network in one location to a network in another location. End-node devices in the remote location do not need VPN clients because the gateway handles the connection. Most site-to-site VPNs connecting over the internet use IP-sec. It is also common for them to use carrier MPLS clouds rather than the public internet as the transport for site-to-site VPNs. Here, too, it is possible to have either Layer 3 connectivity (MPLS IP VPN) or Layer 2 (virtual private LAN service) running across the base transport.