A domain model used in small to mid-sized Microsoft Windows NT–based networks. In the single domain model, all global users and group accounts reside in a single domain and all network resources reside in the same domain. The single domain model is simple to implement and offers centralized administration of accounts and resources.
The model works for as many as 40,000 accounts, although it performs poorly with large numbers of accounts.
When you upgrade a Windows NT–based network based on the single domain model to a Microsoft Windows 2000–based network, you usually end up with a single domain in Active Directory. You can then use Active Directory to create organizational units (OUs) to organize your network and assign administrative rights and permissions.