Many concepts of computer networking are independent of the network operating system (NOS). General networking concepts and services related to TCP /IP are covered in the section basic network concepts and the OSI model explained in simple terms.

What are directory services?

The power of today’s modern  business enterprise networks is fueled by the concept of directory services.

A common example of a directory in the non technology world is a telephone directory, where a list of names is used to cross reference addresses and phone numbers.

In computer networks directory services store, organize, and provide access to information in a directory, creating associations between names and other values. Directory services often use a hierarchical structure to organize various sets of records such as a corporate email directory or telephone directory.

The X.500 series established the basic standards covering electronic directory services with the concepts. The X.500 series, first approved in 1988, defined a hierarchical information tree structure consisting of the Distinguished Names of directory service entries. The International Organization for Standardization (ISO)  was a partner in developing the standards.

What is LDAP?

Lightweight Directory Access Protocol (LDAP) is an application protocol for accessing and maintaining distributed directory information services over an Internet Protocol (IP) network.

One of the advantages of a directory service compared to earlier types of network computing was to provide a single sign-on for a user so that only one log in was required on a network to access many shared services.

The latest version of LDAP established by the Internet Engineering Task Force (IETF) Standard Track Request for Comments (RFCs), was published as RFC 4511 in 2006.

What is Microsoft Active Directory?

Microsoft Active Directory is Microsoft’s directory service for Windows domain networks.

With Microsoft Active Directory a domain controller is a  Windows Server that authenticates and authorizes all users and computers in a Windows domain network.

when a user logs into a Windows domain computer the domain controller checks the submitted user name and password against active directory to determine what access rights the user has on the local workstation as well as network wide privileges.

Microsoft Active Directory is described as using LDAP as the access protocol and supports the X.500 information model without requiring systems to host the entire X.500 overhead. According to Microsoft (1) , “Lightweight Directory Access Protocol (LDAP) is a subset of the X.500 protocol. LDAP clients are, therefore, smaller, faster, and easier to implement than are X.500 clients.”

Microsoft Active Directory was first released with Windows 2000 Server edition.(2)  Active Directory was first released in beta in 1997.(3)

References:

(1) http://support.microsoft.com/kb/196455 (link is external)
Introduction to Lightweight Directory Access Protocol (LDAP)

(2) http://www.networkworld.com/news/2010/021710-active-directory-turns-10.html (link is external)
Network World states that “it all started on Feb. 17, 2000, with the official release of Windows 2000, which featured the first ever network directory from Microsoft.”

(3) Active Directory: Designing, Deploying, and Running Active Directory  By Brian Desmond, Joe Richards, Robbie Allen, Alistair G. Lowe-Norris
From the book, ” The NT NOS slowly evolved over the next eight years until Active Directory was first released in beta in 1997.”