Active Directory uses Lightweight Directory Access Protocol
History
Like many information-technology efforts, Active Directory originated out of a democratization of design using Requests for Comments (RFCs). The Internet Engineering Task Force (IETF) oversees the RFC process and 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 uses 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 unsupported features. Additional improvements came with subsequent versions of Windows Server. In Windows Server 2008, Microsoft added further services to Active Directory, such as Active Directory Federation Services.  The part of the directory in charge of managing domains, which was a core part of the operating system, was renamed Active Directory Domain Services (ADDS) and became a server role like others. "Active Directory" became the umbrella title of a broader range of directory-based services. According to Byron Hynes, everything related to identity was brought under Active Directory's banner.Lightweight Directory Services
Active Directory Lightweight Directory Services (AD LDS), previously called Active Directory Application Mode (ADAM), implements the LDAP protocol for AD DS. It runs as a service on Windows Server and offers the same functionality as AD DS, including an equal API. However, AD LDS does not require the creation of domains or domain controllers. It provides a Data Store for storing directory data and a Directory Service with an LDAP Directory Service Interface. Unlike AD DS, multiple AD LDS instances can operate on the same server.
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