Lightweight Directory Access Protocol (LDAP) is a standard based on X.500, the OSI Directory Access Protocol (DAP). Just like a telephone directory will allow you to look up a telephone number by name, the LDAP standard for directories makes it possible for an LDAP complient client to look up information that’s contained in computer systems and networks. Devices on a network like printers and fax machines, users, e-mail addresses, and many more objects and attributes are stored in X.500 directories.

In addition, the ability to keep track of people, their identities and their attributes, including their credentials for authentication or their public keys, make directory structures an essential element in any identity and access management (IAM) applications.

LDAP is a second generation protocol, stripped down a bit from the original DAP protocol but generally interoperable with it. It also works with more common Internet protocols. Directory products built on the X.500 foundation include Microsoft® Active Directory®, Sun® ONE LDAP Directory and Novell® eDirectory­™.