ETYM Old Eng. realme, ream, reaume, Old Fren. reialme, roialme, French royaume, from (assumed) Late Lat. regalimen, from Latin regalis royal. Related to Regal.
1. A royal jurisdiction or domain; a region which is under the dominion of a king; a kingdom.
2. Hence, in general, province; region; country; domain; department; division.
A network served by a single Kerberos database and group of key distribution centers (KDCs).
To ensure that Kerberos authentication can scale to arbitrarily large networks, realms can be created to partition
the network into different portions, each under the authority of a group of KDCs sharing the same Kerberos database. In popular Kerberos systems such as the Microsoft Active Directory directory service, such realms are identified using Domain Name System (DNS) names, but some Kerberos systems use X.500 names instead. A user in one realm can be authenticated by a different realm using cross-realm authentication. In Kerberos V4 such authentication could take place directly only between two realms that trust each other, but in Kerberos V5 a chain of trust can be established in order to traverse a hierarchy of realms and authenticate a user.