Radiator is a highly configurable and flexible Radius server that
supports authentication by a huge range of authentication methods such
as Flat files, DBM files, Unix password files, SQL databases, remote
Radius servers (proxying), external programs, NT User Manager, Active
Directory, LDAP, PAM, iPASS, GRIC, NIS+, Tacacs+, a wide range of ISP
billing packages such as Emerald, Platypus, Rodopi, Hawk-i,
Interbiller98, Freeside, your legacy user database, etc.