Active Directory Domain Names

Windows 2000 uses DNS naming standards for hierarchical naming of Active Directory domains and computers. For this reason, domain and computer objects are part of both the DNS domain hierarchy and the Active Directory domain hierarchy. Although these domain hierarchies have identical names, they represent separate namespaces.


The domain hierarchy defines a namespace. A namespace is any bounded area in which standardized names can be used to symbolically represent some type of information (such as an object in a directory or an Internet Protocol [IP] address) and that can be resolved to the object itself. In each namespace, specific rules determine how names can be created and used. Some namespaces, such as the DNS namespace and the Active Directory namespace, are hierarchically structured and provide rules that allow the namespace to be partitioned. Other namespaces, such as the Network Basic Input/Output System (NetBIOS) namespace, are flat (unstructured) and cannot be partitioned.

The main function of DNS is to map user-readable computer names to computer-readable IP addresses. Thus, DNS defines a namespace for computer names that can be resolved to IP addresses, or vice versa. In Windows NT 4.0 and earlier, DNS names were not required; domains and computers used NetBIOS names, which were mapped to IP addresses by using the Windows Internet Name Service (WINS). Although DNS names are required for Windows 2000 domains and Windows 2000–based computers, NetBIOS names also are supported in Windows 2000 for interoperability with Windows NT 4.0 domains and with clients that are running Windows NT 4.0 or earlier , Microsoft® Windows® for Workgroups, Microsoft® Windows® 98, or Microsoft® Windows® 95.


WINS and NetBIOS are not required in an environment where computers run only Windows 2000, but WINS is required for interoperability between Windows 2000–based domain controllers, computers that are running earlier versions of Windows, and applications that depend on the NetBIOS namespace — for example, applications that call NetServerEnum and other "Net*" application programming interfaces (APIs) that depend on NetBIOS.