DNS provides the indispensable service of name resolution in TCP- or IP-based networks. DNS is used to map host names to IP addresses and vice versa. It can also be used to store and retrieve other information about a host, such as the services it provides.

The two most important changes in the Windows architecture between Windows NT 4.0 and Windows 2000 were AD and the use of DNS for name resolution. AD extended the Windows 4.0 directory into a fully-extensible, scalable directory service. Windows NT Server and earlier versions depended on NetBIOS names and implemented Windows Internet Name Service (WINS) to resolve computer names to IP addresses. Windows 2000 Server introduced DNS as the name resolution mechanism.

DNS is the backbone of AD and another crucial system for Exchange as it is the principal name resolution mechanism of any Windows server and client. DCs use DNS to dynamically register information about their configuration and about the AD system. Other Windows...