Network Operating System Features – Directory Services

Directory services are an essential part of any network operating system (NOS). Networks have directories that provide information about the resources that are available on the network, such as users, computers, printers, shared folders, and files.

In early network operating systems, such as Windows NT 3.1 and NetWare 3.x, each server computer maintained its own directory database of resources that were available on just that server.

The problem with that approach was that network administrators had to maintain each directory database separately. That wasn’t too bad for networks with just a few servers, but maintaining the directory on a network with dozens or even hundreds of servers was next to impossible.

In addition, early directory services were application specific. For example, a server would have one directory database for user logins, another for file sharing, and yet another for e-mail addresses. Each directory had its own tools for adding, updating, and deleting directory entries.

Most modern networks — particularly those based on Windows servers — use a directory service called Active Directory. Active Directory is essentially a database that organizes information about a network and allows users and computers to gain permission to access network resources. Active Directory is simple enough to use for small networks with just a few computers and users, but powerful enough to work with large networks containing tens of thousands of computers.