Active Directory's multimaster replication model creates a distributed environment that allows any domain controller to be used for authentication and allows changes to be made to standard directory information without regard to which domain controller is used. The approach works well for most Active Directory operations—but not all. Some Active Directory operations can only be performed by a single authoritative domain controller called an operations master.
A designated operations master has a flexible single-master operations (FSMO) role. The five designated roles are
Domain naming master
Relative ID (RID) master