DNS and LDAP are the two protocols on which the Internet and the Intranet are built.
Most of the time, you don't have to care about them. But sometimes, you need to access them directly, especially in a corporate environment.
We just introduced in our Open Source mORMot 2 framework two client units to access DNS and LDAP/CLDAP servers.
You can resolve IP addresses and services using DNS, and ask for information about your IT infrastructure using LDAP.