As companies have expanded, and moved from just using telephones to email and web based systems, so the comon telephone directory has needed to expand and grow. In the 1980s telecommunication companies developed the X.500 specification, which is a suite of protocols to create and distribute a directory of data.

X.500 directory services were accessed via the X.500 Directory Access Protocol (DAP) which used the Open Systems Interconnect (OSI) protocol stack. As companies [spi]began|started[/spin] to use TCP/IP networks, many found the complexity of managing a large OSI/DAP infrastructure too much. The Lightweight Directory Access Protocol (LDAP) was developed to access X.500 directory servers via TCP/IP.

An LDAP server uses the idea of an organisational structure to organise data, which can include usernames, telephone numbers, office locations, photos, and more. This directory structure can closely match an organisation’s structure, making LDAP directories an obvious fit for replacing an organisation’s phonebook. The initial X.500 specification was deliberately designed with this scalable organisation of information in mind, which is one of the main factors behind the success of LDAP.

With the development of Voice Over IP (VOIP) technologies an entire company’s data can be held within LDAP, allowing access from email clients, instant messaging applications, and HR systems. Even products such as Microsoft’s Active Directory are based on LDAP and X.500 directory structures. LDAP’s power makes it an useful of any organisation infrastructure.