Active Directory (AD) is a directory service developed by Microsoft for Windows domain networks. It is included in most Windows Server operating systems as a set of processes and services. Initially, Active Directory was used only for centralized domain management. However, Active Directory eventually became an umbrella title for a broad range of directory-based identity-related services. A server running the Active Directory Domain Service (AD DS) role is called a domain controller. It authenticates and authorizes all users and computers in a Windows domain type network, assigning and enforcing security policies for all computers, and installing or updating software. For example, when a user logs into a computer that is part of a Windows domain, Active Directory checks the submitted username and password and determines whether the user is a system administrator or normal user. Also, it allows management and storage of information, provides authentication and authorization mechanisms and establishes a framework to deploy other related services: Certificate Services, Active Directory Federation Services, Lightweight Directory Services, and Rights Management Services. Active Directory uses Lightweight Directory Access Protocol (LDAP) versions 2 and 3, Microsoft's version of Kerberos, and DNS. Robert R. King defined it in the following way: History Like many information-technology efforts, Active Directory originated out of a democratization of design using Request for Comments (RFCs). The Internet Engineering Task Force (IETF), which oversees the RFC process, has accepted numerous RFCs initiated by widespread participants. For example, LDAP underpins Active Directory. Also, X.500 directories and the Organizational Unit preceded the Active Directory concept that makes use of those methods. The LDAP concept began to emerge even before the founding of Microsoft in April 1975, with RFCs as early as 1971. RFCs contributing to LDAP include RFC 1823 (on the LDAP API, August 1995), RFC 2307, RFC 3062, and RFC 4533. Microsoft previewed Active Directory in 1999, released it first with Windows 2000 Server edition, and revised it to extend functionality and improve administration in Windows Server 2003. Active Directory support was also added to Windows 95, Windows 98 and Windows NT 4.0 via patch, with some features being unsupported. Additional improvements came with subsequent versions of Windows Server. In Windows Server 2008, additional services were added to Active Directory, such as Active Directory Federation Services. The part of the directory in charge of the management of domains, which was previously a core part of the operating system, was renamed Active