OSF DCE Administration Guide--Core Components

Introduction to the DCE Directory 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 chapter explains how the DCE 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 chapter 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.
11.3 Directory Services and the Cell Environment
This section introduces the following main components of the DCE naming environment
and explains their relationship to the cell:
• CDS
• GDS
• DNS
• GDA
CDS is a high-performance distributed service that provides a consistent, location-
independent method for naming and using resources inside a cell (intracell). CDS can
also be used for communication between cells (intercell) when cells are connected into a
hierarchy.
GDS supports the global naming environment inside cells (intracell) and outside of cells
(intercell). GDS is an implementation of a directory service standard known as X.500.
This standard is specified by the International Organization for Standardization (ISO)
9594 and the International Telegraph and Telephone Consultative Committee (CCITT)
X.500 series. Because it is based on a worldwide standard, GDS offers the opportunity
for a universally interoperable global directory.
Figure 11-1 represents a hypothetical configuration of two cells that each use GDS to
access names in the other cell. Names that are stored directly in GDS also are accessible
from each cell. CDS is the directory service within each cell. The same organization
administers both cells, which are configured based on geographic location and network
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