The Unix system administrator traditionally uses the NIS service for name resolution and data distribution in a network. The configuration data contained in the files in /etc and the directories group, hosts, mail, netgroup, networks, passwd, printcap, protocols, rpc, and services are distributed by clients all over the network. These files can be maintained without major effort because they are simple text files. The handling of larger amounts of data, however, becomes increasingly difficult due to nonexistent structuring. NIS is only designed for Unix platforms. This means it is not suitable as a centralized data administration tool in heterogeneous networks.
Unlike NIS, the LDAP service is not restricted to pure Unix networks. Windows servers (from 2000) support LDAP as a directory service. Application tasks mentioned above are additionally supported in non-Unix systems.
The LDAP principle can be applied to any data structure that should be centrally administered. A few application examples are:
Employment as a replacement for the NIS service
Mail routing (postfix, sendmail)
Address books for mail clients, like Mozilla, Evolution, and Outlook
Administration of zone descriptions for a BIND9 name server
User authentication with Samba in heterogeneous networks
This list can be extended because LDAP is extensible, unlike NIS. The clearly-defined hierarchical structure of the data eases the administration of large amounts of data, because it can be searched more easily.