This document discusses factors to consider when assigning Flexible Single Master Operation (FSMO) roles and placing Global Catalogues in an Active Directory environment. It recommends having at least two domain controllers for environments with more than 20 users to improve recoverability. The roles that should be unique per domain are the RID Master, PDC Emulator Master, and Infrastructure Master. These roles are responsible for allocating relative IDs, processing password changes, and maintaining operations respectively. The document also briefly describes the functions of the Schema Master and Domain Naming Master roles.