LDAP directories

Individuals and businesses are increasingly using networks to access distributed applications and shared resources (websites, application servers, file servers, etc.).

These applications and resources need to interact with computers located on the same local network, via the company intranet, or more generally via the Internet. A priori, this requires knowledge of the addresses of these different machines. However, in the vast majority of cases, we never use actual machine addresses; we use names.

Let's take a few simple examples. Access to a web site will be via a name designating the site. Access to a printer will also be via a name designating the printer. This information is managed in a special database called a directory. The directory transforms the site or printer name into a physical address, enabling communication protocols to access the equipment concerned.

Over the years, numerous directory tools have been developed, offering a wide variety of services. Some of these have fallen by the wayside, while others, such as DNS (Domain Name System), have immediately become indispensable standards. For a few years now, a new standard has been appearing, itself on the way to becoming absolutely indispensable, known by its acronym LDAP (Lightweight Directory Access Protocol). This standard won't replace DNS - that's not what it's designed to do - but it does unify certain needs, such as those for white pages, NIS (Network Information Service; yellow pages) directories, authentication and so on.

The study of LDAP will be broken down as follows. In the first section, we'll cover the generalities of a directory. In the second section, we'll get to the heart of the matter, i.e. the theoretical concepts needed to understand this type of directory. The third section will cover everything you need to know to access an LDAP directory without any problems. The fourth section outlines a textual syntax that can be used to represent the data contained in a directory or to serve as an exchange format. Finally, before concluding, we'll give an overview of the different types of communication available in the context of LDAP directories, as well as a brief presentation of a few tools.