Definition: IPsec is a technology standard for implementing security features in Internet Protocol (IP) networking. IPsec network protocols support encryption and authentication. IPsec is most commonly used in so-called "tunnel mode" with a Virtual Private Network (VPN). However, IPsec also supports a "transport mode" for direct connection between two computers.
Technically, IPsec functions at the network layer (Layer 3) of the OSI model. IPsec is supported in Microsoft Windows (Win2000 and newer versions) as well as most forms of Linux / Unix.
