Populated with users, applications, services, system resources and numerous devices, a network is often enormously complex. Furthermore, for administrators to manage the complexity, a network has to be able to do several things. The task is so critical, in fact, that the network operating system devotes an entire system service to organizing network objects and their relationships. This system-level service is called directory services. The goal is to allow users to easily locate network resources, and use them efficiently.
Every network operating system implements some form of directory services.
This is one of its core functions. But because system directories are typically organized and grouped in files, offering a two-dimensional view, typical directories have little value as organizational tools. This changes in Windows NT version 5, where the directory becomes hierarchical. This new directory understands relationships among its objects, as well as the network's contents. The Microsoft Active Directory Model Microsoft brings business modeling together with network modeling, and makes directory services far more than some arcane tool rooted in server rooms.