Radius Manager Roaming
RADIUS is commonly used to facilitate roaming between ISPs.
by companies which provide a single global set of credentials that are usable on many public networks.
by independent, but collaborating, institutions issuing their own credentials to their own users, that allow a visitor from one to another to be authenticated by their home institution, such as in ERduroam.
RADIUS facilitates this by the use of realms, which identify where the RADIUS server should forward the AAA requests for processing.