The Evolution of Microsoft Directory Services

Active Directory is the latest version of a directory service for the Microsoft Windows operating system. Active Directory first appeared in Windows 2000 Server and is also a component of Windows Server 2003. The need for directory services in the Microsoft workstation computing environment grew out of the proliferation of personal computers in the workplace. As more and more computers entered the corporate work environment, so the need grew to interconnect them to share resources and to enable users to communicate in near-real time. But when a company has shared resources available on a network, it also needs a catalog, or directory, of users and a system for assigning user permissions to the resources.

LAN Manager for OS/2 and MS-DOS

In 1987, the first directory service developed to support a Microsoft workstation computing environment (OS/2 and MS-DOS) was found in the Microsoft LAN Manager network operating system. The LAN Manager’s “directory service” provided basic functionality for sharing file and print resources and for user security, but it was not suitable for largeenterprise environments. It did not scale well, and it did not support trust relationships. Instead, network users had to log on to each domain separately to access shared resources.