OUs are normally hierarchical, based on the company s specific administrative model. They can be based on function, geography, or any other model. The OU hierarchy within a domain is independent of the OU hierarchy structure of other domains. The domain containing the first domain controller created in a forest. Schema A collection of object class definitions that are within a domain.
Schemas are extensible and can be updated dynamically.
Areas of a network separated by wide area network technologies, multiple routers, or other slower links should be defined as separate sites. The function of sites is to improve efficiency and optimize replication traffic. There is no necessary correlation between the network s physical structure and its domain structure, or between site and domain namespaces. While a site can have multiple domains, it is also true that a single domain can contain multiple sites. Tree A hierarchical arrangement of one or more domains with a single root name.