Lightweight Directory Access Protocol (LDAP)

What is LDAP?

The Lightweight Directory Access Protocol (LDAP) is a protocol for accessing online directory services. It runs directly over TCP, and can be used to access a standalone LDAP directory service or to access a directory service that is back-ended by X.500.

What is a directory service?

A directory is like a database, but tends to contain more descriptive, attribute-based information. The information in a directory is generally read much more often than it is written. As a consequence, directories don't usually implement the complicated transaction or roll-back schemes regular databases use for doing high-volume complex updates. Directory updates are typically simple all-or-nothing changes, if they are allowed at all. Directories are tuned to give quick-response to high-volume lookup or search operations. They may have the ability to replicate information widely in order to increase availability and reliability, while reducing response time. When directory information is replicated, temporary inconsistencies between the replicas may be OK, as long as they get in sync eventually.

How does LDAP work?

LDAP directory service is based on a client-server model. One or more LDAP servers contain the data making up the LDAP directory tree. An LDAP client connects to an LDAP server and asks it a question. The server responds with the answer, or with a pointer to where the client can get more information (typically, another LDAP server). No matter which LDAP server a client connects to, it sees the same view of the directory; a name presented to one LDAP server references the same entry it would at another LDAP server. This is an important feature of a global directory service, like LDAP.

LDAP Software

  • LDAP Client Software
  • LDAP Gateway Software

  • LDAP Server Software
      1. ldap (front end for an X.500 DSA)
      2. slapd (standalone LDAP directory server)
      3. slurpd (standalone LDAP update replication daemon)

Resources of LDAP



Products and Prototypes

Related sites


 This homepage is maintained by mjchoi .    Last updated : March 20, 2001