The domain remains the primary organizational unit in Windows 2000. Those familiar with NT will recognize this level of organization and coordination. A domain contains various types of objects, including users, groups, printers, workstations, member servers, and domain controllers (see Figure 3.6).
Figure 3.6 Domains contain objects in a centralized administrative grouping.
User logins provide access to resources. Each account will have an associated name, logon ID, and password as well as many other optional attribute values. User logons may be directly granted permissions allowing access or restricting access to various resources and administrative rights.
Groups provide a simple method for the administration of large numbers of users. Although it may be simple to assign access rights and restrictions individually to a small number of users, this can rapidly become a significant administrative burden when 20,000 or more users are involved. Assigning access and administrative rights to groups, and making users members of these groups, allows users to inherit the access permissions assigned to those groups of which they are members.
For example, in order to change the access rights of a user promoted from Sales to an executive office, the administrator need do nothing more than make the user a member of the Executive group and remove her membership from the Sales group. Changing individually assigned permissions is no longer necessary, which eases the administrative burden in a large deployment.
Considerations for the use of groups in order to provide access and administrative rights inheritance are provided later in Chapter 6.
Other object accounts may be created within the catalog including printers, workstations, and servers. The Active Directory database may contain references to objects. Attributes assigned to these object references may allow them to be more easily located, accounted for, or organized in large deployment scenarios.
Member servers are computers running software designed to provide centralized services to distributed users and workstations, but which do not participate in login authentication as do domain controllers. Member servers have local user accounts and may be used when resource access is desired without the use of domain-level account permissions.
Windows 2000 introduces a new subdomain grouping category: the organizational unit (OU). Objects may be grouped into organizational units, and administrative rights over those objects may be granted to users or groups that do not require full domain administrative rights. Organizational units may also be grouped within one another, allowing many levels of administrative capability to be granted, each inclusive of those organizational units under its level of authority.
Organizational units may be created that more closely match the administrative structure of a business model. For example, an admin can group users, printers, and computers within the Sales department into one organizational unit. Users, printers, and computers within the Human Resources department may then be grouped into another organizational unit, with separate access rights appropriate to its separate requirements (see Figure 3.7).
Figure 3.7 Organizational units allow objects to be grouped to match a business model.
Unlike a Domain Administrator account, a user account granted administrative rights over the Sales organizational unit would have no inherent rights over the Human Resources organizational unit. If there were nested organizational units for the Conflict Management and Employee Retention subdepartments within the Human Resources organizational unit, the administrator over the Human Resources department would also have administrative rights over both nested organizational units as well. However, a user account granted administrative rights over the Employee Retention organizational unit would not have any inherent rights over the Conflict Management nor parent Human Resources organizational units.
Configuration settings and software deployment may also be enacted based on organizational unit membership using Group Policy Object (GPO) assignment, which will be discussed in detail in Chapter 7.
The Windows 2000 active directory allows for nested domains as well. Often, it is useful to separate domains based on separate business requirements such as internationally deployed corporate offices. In this case, the root (or top-level) domain might be mycorp.com, which has child domains of europe.mycorp.com, asia.mycorp.com, and australia.mycorp.com. Additional child domains may be created beneath existing domains, allowing extensible subordination of domain administration to whatever degree is required. In this way, the child domain europe.mycorp.com may function as the parent to the second-level child domains germany.europe.mycorp.com and denmark.europe.mycorp.com.
A hierarchical collection of parent/child domains with a contiguous namespace (one in which all child domains contain the full name of their parent domain) is referred to as a tree. Figure 3.8 illustrates a tree for the mycorp.com domain namespace.
Figure 3.8 Tree diagram for mycorp.com.
The first domain installed will form the root domain for a tree. No parents may be added to existing domains, only children.
It is occasionally useful to link multiple trees into larger administrative groupings. This is often done when it is necessary to maintain separate legal holdings, or after a merger of two corporations has occurred and migration to a single tree has not yet been accomplished. Multiple trees joined by full two-way transitive trusts create a larger grouping called a forest.
Forests may be identified by the lack of a continuous namespace such as is found within a tree. A forest may contain the trees whose root domains are mycorp.com and newcorp.com (see Figure 3.9).
Figure 3.9 Forest diagram for trees mycorp.com and newcorp.com.