RADIUS
    RADIUS is a
        client/server protocol and software that enables remote access servers to communicate with a
        central server to authenticate dial-in users and authorize their access to the requested
        system or service. RADIUS allows a company to maintain user profiles in a central database
        that all remote servers can share. It provides better security, allowing a company to set up
        a policy that can be applied at a single administered network point. With RADIUS, you can
        track usage for billing and for keeping network statistics.