LDAP is a Lightweight Directory Access Protocol. It is a protocol for accessing information directories such as organizations, individuals, phone numbers, and addresses. LDAP servers store data in a Directory Information Tree, which is a hierarchical grouping of related data.
The LDAP Data source driver is built on JNDI API to provide access to the directories. It provides the user with the ability to filter and extract LDAP entries.
LDAP is based on the X.500 standard but is significantly simpler. Unlike X.500, LDAP supports TCP/IP, which is necessary for any type of Internet access. A typical LDAP server is a simple network-accessible database where an organization stores information about its authorized users and what privileges each user has. The standards are specified in RFC 1777.
Attached is documentation on LDAP Datasource with Windows 2003 server Active Directory.