Considering the Directory Services Model

The concept of the directory services model grew out of a need to better manage large, complex networks found in today's organizations. The complexity was due in large part to two factors: First, applications used over the network were becoming more popular and created a greater demand; second, it was becoming increasingly common to have software and hardware from different vendors in operation on the same network. Directory server provides a centralized system for managing applications, files, printers, people, and other resources in large groups or individually.

In a directory services model, a hierarchical database contains all the network resources. Conceptually, the database looks like an upside-down tree structure. The root of the tree is at the top and is used to represent the organization. Users logging on to the network are actually logging on to the directory services database. The user can access any objects within the database that they have been given access to. Objects can be users, groups, servers, printers, and so on.

The directory services database consists of a hierarchical structure of objects. You can think of objects as towns located along a river. Each town has characteristics that make it unique. Like the town, each object in directory services has properties that can be managed. Continuing with the analogy, the towns are linked together by water whether they are on the river or a tributary that connects to the river. Similar to the river that links the towns, the link between the objects is called the directory tree. The directory tree is what helps organize management of directory services. This structure enables the administrator to logically group directory service objects.

When Appropriate

For medium to large networks, this model is the wave of the future. The main network operating systems-NetWare 4.x, 5.x, and 6.x, and Windows 2000 and Windows Server 2003-use a directory services network model.

Consider these advantages to using directory services:

• This model scales well to any size network.

• The administrator can logically group users and resources within the directory services tree.

• You can centralize or decentralize account and resource management as much as you wish. Administrative tasks can be delegated to other individuals without jeopardizing consistency in the directory services database.

You should also consider these disadvantages:

• This model is the most difficult to design and manage.

• This model requires a trained and experienced network administrator to install and manage it.

• There is added complexity when migrating from the domain model to a directory services model.