Short for
Remote Authentication Dial-In User Service, an
authentication and accounting system used by many
Internet Service Providers (ISPs). When you dial in to the ISP you must enter your
username and
password. This information is passed to a RADIUS
server, which checks that the information is correct, and then
authorizes access to the ISP system.
Though not an official standard, the RADIUS specification is maintained by a working group of the IETF.