A domain controller is a server that manages the various subdomains and main domains of the Domain NameSystem( DNS) on the Internet. The DNS name system is hierarchical and has its origin in the root domain. This is followed by the top level domain( TLD), the sub-domains, the second level domain and the third level domain. The objects on these domains are managed by the domain controller.
The domain controller manages the access rights with which the users of a domain must authenticate themselves. Depending on the size of the network and the number of users, availability and load balancing can only be ensured by several powerful servers. The servers constantly update their databases and have redundant functions, so that they can take over the task of a server in case of failure. Logged-in users have access to specific datasets and other resources.