A Microsoft Windows 2000 domain controller that stores a copy of the global catalog. Administrators and users can utilize global catalog servers on a Windows 2000–based network to locate objects that are stored in Active Directory. Information stored on global catalog servers is updated each time Active Directory undergoes directory replication.
You must locate your global catalog servers appropriately so that queries on Active Directory perform effectively. Ideally, you should have at least one global catalog server at each site within the enterprise. However, in a multidomain environment, the replication traffic generated by maintaining these servers can be a burden on overall network traffic, especially if slow WAN links are involved. Consider placing your global catalog servers as follows: