X.500 and Lightweight Ditectory Access Protocol
International Telecommunication Union (ITU) and International Organization of Standardization (ISO) proposed X.500 standard in 1988.
X.500 was a very good Directory Standard and provided a lot of new functionality and security. The problem with X.500 was it was difficult to implement. The X.500 Directory Access Protocol (DAP) was too complex and was using OSI network protocol instead of TCP/IP.
Lightweight Directory Access Protocol (LDAP) was developed after X.500 and LDAP was based on X.500. Since Lightweight Directory Access Protocol (LDAP) was originated from X.500, the structure of X.500 and Lightweight Directory Access Protocol (LDAP) directories are almost similar. LDAP directory implementations are often also X.500 compliant.
The first version of the Lightweight Directory Access Protocol (LDAP) was released in 1993 as RFC 1487 and it was not successful because of the absence of many features provided by X.500. The University of Michigan scientists released the first LDAP directory server, as RFC 1777 (LDAPV2) in 1995 and it became the basis for many future directory servers. LDAP version 3 (v3) is defined by nine RFC documents. RFC’s 2251 through 2256 give the core details, and were later followed by RFC 2829, 2830 and 3377. All these RFC’s together known as LDAPV3. LDAPV3 was released on December 1997.