FreeRADIUS is an Internet authentication daemon, which implements
the RADIUS protocol, as defined in RFC 2865 (and others).  It allows
Network Access Servers (NAS boxes) to perform authentication for
dial-up users.  There are also RADIUS clients available for Web
servers, firewalls, Unix logins, and more.  Using RADIUS allows
authentication and authorization for a network to be centralized, and
minimizes the amount of re-configuration which has to be done when
adding or deleting new users.