A Microsoft technology that constitutes an LDAP directory service with centralized management functionality for user accounts, computer accounts, groups, and configuration management across many Windows servers and desktops.

Active Directory is a directory service created by Microsoft for managing Windows environments.

It is used for:

  • A centralized Authentication/Authorization source for Kerberos and NTLM protocols.
  • Providing a single authentication/authorization domain for member servers and workstations.
  • Providing LDAP services.
  • Providing centralized configuration methods of Windows workstations and servers through Group Policy and other methods.
  • Multi-site replication of directory-database data.

Non-Windows support is generally provided through the Samba package on POSIX operating systems (Linux, macOS, BSD, Solaris, etc). All modern Samba releases allow machines to join a domain as if they were a Windows machine.

For a list of ports which must be open in a firewall for AD to work properly, see http://serverfault.com/questions/304484/what-firewall-ports-need-to-be-open-for-active-directory.

Some useful links are below