Having designed the domain namespace, you can now concentrate on the internals of each domain. The design process itself is the same for each domain, but the order is mostly up to you. The first domain that you should design is the forest root domain. After that, iterate through the tree, designing subdomains within that first tree. Once the tree is finished, go on to the next tree and start at the root as before.
In a tree with three subdomains called Finance, Sales, and Marketing under the root, you could either design the entire tree below Finance, then the entire tree below Sales, and so on, or you could design the three tier-two domains first, then do all the subdomains immediately below these three, and so on.
When designing the internals of a domain, you need to consider both the hierarchical structure of Organizational Units and the users and groups that will sit in those Organizational Units. Let’s look at each of those in turn.
When we refer to a hierarchy, a tree, or the directory tree, we mean the hierarchical Organizational Unit structure within a domain. We are not referring to the hierarchy of domain trees in a forest.
Earlier, when we discussed how to design domains, we spoke of how to minimize the number of domains you have. The idea is to represent most of your requirements for a hierarchical set of administrative permissions using Organizational Units instead.