In a Windows 2000 or Windows Server 2003 environment, DNS is the primary method for name resolution. However, even in these environments, NetBIOS name resolution might still be extensively used. For example, if the network consists of older clients, such as Windows NT 4 and Windows 9 x clients, you must still support NetBIOS name resolution. Also, certain applications, such as Microsoft Exchange Server, still rely on NetBIOS for their functionality. So, even if the domain is upgraded to AD and all of the clients on the network are upgraded to Windows 2000 or Windows XP, it might still be necessary to support NetBIOS name resolution.

The primary means for ensuring fault-tolerant and timely NetBIOS name resolution is through the implementation of WINS. Through its ability to replicate information with other WINS servers, WINS provides a distributed database that allows NetBIOS clients to register their NetBIOS names to ensure uniqueness and to resolve NetBIOS-to-IP address mappings consistently throughout the network infrastructure. Because WINS servers are capable of replicating database information to one another, this means that multiple WINS servers can provide both fault tolerance and availability of records for NetBIOS resolution to even very large networks that involve many different sites.