The UM server can make use of a variety of backend Directory servers or mechanisms, as controlled by the Nirvana.directory.provider system property, which specifies the pluggable Java class representing the Directory.

Usernames are case-sensitive and are used in the form supplied to do the Directory lookup. This is the authentication step, and is followed by an authorization step in which the username is normalized to lowercase to match against Nirvana ACLs. Nirvana ACLs are case-insensitive but expressed in lower-case and any ACLs created via the Enterprise Manager will be forced to lower case.