OpenVPN is a free and open source virtual private network (VPN) program for creating point-to-point or server-to-multiclient encrypted tunnels between host computers. OpenVPN is considered to be extremely secure when compared to the PPTP VPN, and also more stable. The disadvantages are related are to the installation (it requires client software) and to the lower speed.
OpenVPN is an open-source software application that implements virtual private network (VPN) techniques for creating secure point-to-point or site-to-site connections in routed or bridged configurations and remote access facilities. It uses a custom security protocol that utilizes SSL/TLS for key exchange. It is capable of traversing network address translators (NATs) and firewalls. It was written by James Yonan and is published under the GNU General Public License (GPL).
OpenVPN allows peers to authenticate each other using a pre-shared secret key, certificates or username/password. When used in a multiclient-server configuration, it allows the server to release an authentication certificate for every client, using signature and Certificate authority. It uses the OpenSSL encryption library extensively, as well as the SSLv3/TLSv1 protocol, and contains many security and control features.
OpenVPN has been ported and embedded to several systems. For example, DD-WRT has the OpenVPN server function. SoftEther VPN, a multi-protocol VPN server, has an implementation of OpenVPN protocol.
Private Tunnel VPN is a commercial spin-off of OpenVPN Technologies, a VPN service provider based in the US that, unusually, charges according to data transferred rather than per month.