GNU Radius is a suite of programs for performing user authentication and
accounting services using RADIUS protocol.

Its major features are:
1) All server parameters are configurable.
2) Flexible support for VSA (vendor-specific attributes) pairs.
3) Fast lookup in the users database.
4) Support for several accounting types, among them MySQL and
PostgreSQL accounting.
5) Configurable SQL queries.
6) Ability to parse and rebuild incoming requests on the fly, for
example to facilitate their storing in database. Such parsing is
done by functions written in an extension language so no
recompilation is needed.
7) Guile interface allows for writing client-side applications. A set
of scheme primitives is provided to facilitate writing such
programs.