OSF DCE Administration Guide--Core Components

OSF DCE Administration Guide—Core Components
addresses of RPC servers and the interfaces they support.
When an RPC client wants to make a call to a particular server, it can query the directory
service for the information necessary to contact that server. If the client wants to access
a specific resource that is named in the directory service, it can query for that specific
name. If a client application knows the type of service that it wants, such as C
compilers, printers, or employee information, but does not know the address of a specific
server, it can also use the directory service to find that information.
The DCE Security Service, which verifies the identity of users when they log in, uses the
directory service to store the addresses of its authentication servers.
The Distributed File Service (DFS) provides a location service for filesets (logical
groups of files) so that users can access remote files as if they are on the local system.
DFS uses the DCE Directory Service to find out how to contact its fileset location
servers.
The Distributed Time Service (DTS) is responsible for synchronizing system clocks in
the network. Synchronized clocks are important to any distributed application that needs
to keep track of the order in which events occur across multiple systems. DTS uses the
DCE Directory Service to find out how to locate its time servers.
11.2 How to Use DCE 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.
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