When email was introduced and started to be used in corporations, one challenge was to look up the email address of someone that had never communicated with you. It required some sort of central repository for searching the email addresses of other people within the organization.

Necessity is the mother of invention. The need for a central data depot brought companies like Microsoft, Lotus, Netscape, and IBM together, and they defined a standard called LDAP. It is a protocol for accessing data stored in a directory structure over the network.

The LDAP server, which holds and indexes the data in a hierarchical manner, can be accessed by LDAP-aware clients. The data can be filtered to select a particular person or group stored in a different entity. For example, imagine searching for all employees located in Chicago that are from the admin department and have been working for more than three years, and receiving their full name, designation, and email address. This is quite possible with LDAP. 

Apart from contact information, LDAP can also be used to store access control data, which can then be used to perform authentication and authorization. We will start by covering the basics of LDAP and how to construct a data structure with it.