Authentication is an essential part of securing any service or network, and one of the heavyweights of network authentication is RADIUS. RADIUS, which is an acronym for "Remote Authentication Dial In User Service", is a network authentication protocol that widely implemented for a number of different services.
According to Wikipedia, RADIUS was originally specified in an RFI by Merit Network in 1991 to control dial-in access to NSFnet. Livingston Enterprises was awarded the contract and delivered their PortMaster series of Network Access Servers and the initial RADIUS server to Merit. RADIUS was published as RFC 2058 in 1997 and RFC 2059 (current versions are RFC 2865 and RFC 2866).