The Master Domain model is geaared towards a large enterprise and is much better suited for a large number of computers and domains. See diagram 1. The Red signifies the Master domain. The Blue signifies resource domain 2. The Green signifies resource domain 3.
Security is simplified by pulling groups from the master domain into the resource domain.
Now we get into global and local groups. The global groups can span domains but local groups cannot. The key here is knowing how to utilize both sets of groups. Global groups go into Local groups, in one or more domains. Resources are secured by Local groups.