How To Use Directory Services

Other than DCE administrators, the people who use directory services normally do so indirectly, through an application interface. An application can interact with the Directory Service on behalf of users who create a name for a resource and subsequently refer to it by that name. The following examples, both real and hypothetical, explain some of the ways that users can use the Directory Service:

· A user invokes a spell-checking application on a new document. The application contains DCE RPC client code on the user's local system. The RPC client contacts the Directory Service for information on an available spell-checking server. The Directory Service returns the address of the server, the protocol type it uses to communicate, and a Universal Unique Identifier (UUID) that represents an interface. Using this information, the RPC client makes a remote call to the server and the server checks the spelling in the user's document. The user is unaware that use of the spell checker involved a call to the Directory Service and interaction with a remote server.

· A user logging into a system enters a name and password. The Directory Service helps the login program locate an authentication server, which verifies the user's identity in an authentication database.

· A user enters a file specification. The Directory Service provides the address of a DFS fileset location database, which contains the network address of a server that allows the user to access the file.

· A user enters the name of a computer conference or electronic bulletin board and the Directory Service provides an address, allowing the application to connect to the conference service.

· By entering a name or some information about a printer's capabilities, a user can learn the printer's network address. For example, the user may want to find the address of the closest and fastest available color printer.

· A user needs information from an employee in the marketing department. The user remembers that the employee's last name is Wong, but cannot remember the first name. By entering the last name and department name in an employee locator application, the user can check the Directory Service for information on all Wongs in the marketing department and find out how to contact the employee.

· A user enters a report in a problem-tracking database. Although the database was recently moved to a new node, the user is not aware of the change because the database is always referred to by its name only. The Directory Service stores the current network address and provides it to the problem-tracking application and any other application that requests it.

The remainder of this topic explains how the Directory Service environment works with regard to cells. It introduces the main Directory Service components: the Cell Directory Service (CDS), the Global Directory Service (GDS), and the Global Directory Agent (GDA), which is a gateway between the local and global naming environments. The topic also discusses DCE support for the Domain Name System (DNS), which is a global name service that is not a part of the DCE technology offering.