What Is Lightweight Directory Access Protocol (LDAP)?

Lightweight directory access protocol (LDAP) is an application protocol for accessing and managing directory information that is widely used within an organization. It is a vendor-neutral protocol that provides a means for accessing and modifying directory services over a network. LDAP builds upon a client-server model and operates over TCP/IP, making it suitable for distributing computing environments such as the internet.

LDAP is lightweight, efficient, and extensible, making it an ideal choice for directory services. A directory service is a centralized database that stores and organizes information in a hierarchical manner. Such information is typically about users, systems, networks, and other resources. LDAP allows clients to search, read, and modify data in the directory service. It provides a standardized way to interact with directory services, regardless of the specific implementation or underlying technology.

At its core, LDAP defines a protocol for communication between LDAP clients and LDAP servers. The protocol uses a simple string-based format for querying and exchanging messages, which eliminates the requirement of manually entering multiple queries for a certain task. LDAP messages travel over a network connection using the lightweight directory access protocol data units (PDUs).

LDAP operates on a directory information tree (DIT) structure, which is a hierarchical organization of entries that represent objects or resources in the directory. The organization of entries in the DIT uses a naming scheme called the distinguished name (DN). The DN uniquely identifies each entry in the directory and specifies its position in the tree.

Read more: Information Technology (IT) Terms: A to Z Glossary

LDAP examples

Consider an organization that uses LDAP for managing employee information. The directory contains entries for each employee, storing attributes such as name, email address, phone number, and department. 

Each entry in the directory has a unique DN that identifies its position in the tree. For example, the DN for Jane Smith would be ‘cn=Jane Smith, ou=Employees, ou=Marketing, o=Acme.’ The ‘cn’ stands for common name, ‘ou’ for organizational unit, and ‘o’ for organization.

LDAP clients can perform various operations on the directory entries, such as searching, adding, modifying, or deleting. Let's consider a scenario where an LDAP client wants to search for employees in the marketing department whose name starts with "J".

The LDAP server receives the search request, traverses the DIT starting from the base DN, and returns the matching entries. 

The client receives the search results and processes them according to its needs. It can extract the employee name from the returned entry and display it, perform further operations on the entry, or retrieve additional attributes.

Related terms

• Information technology (IT) infrastructure

• DHCP

• Transmission control protocol/internet protocol (TC/IP)

• CPU

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