Remote Authentication Dial In Service (RADIUS)

Non-proprietary (open) client-server authentication and accounting protocol which (although not an official standard) is a popular specification maintained by the internet engineering task force. Used by internet service providers and large firms, it maintains authentication server code and user names, passwords, and profiles in a centralized database against which all dialup-access attempts are matched. Originally developed by Livingston Enterprises, it is an alternative to TACACS.