LDAP stands for Lightweight Directory Access Protocol -- a fact we learned from a Yahoo! search that took us to a category called LDAP (Lightweight Directory Access Protocol), located in part of the Computers & Internet hierarchy. Apparently, LDAP is an up-and-coming acronym that hasn't made it into popular parlance, yet. We headed to the LDAP FAQ for a definition.
Here's an answer to the first part of your question:
(Warning: If you suffer from jargon allergies hit the back button on your browser now.)
"LDAP is a client-server protocol for accessing a directory service. It was initially used as a front-end to X.500, but can also be used with stand-alone and other kinds of directory servers."
Uh-oh� We headed off to Whatis.com, a friendly encylcopedia of information technology terminology. Clicking our way from "L" toLDAP, we learned a little more.
LDAP lets you "locate organizations, individuals, and other resources such as files and devices in a network, whether on the Internet or on a corporate intranet," and whether or not you know the domain name, IP address, or geographic whereabouts. An LDAP directory can be distributed among many servers on a network, then replicated and synchronized regularly. An LDAP server is also known as a Directory System Agent (DSA).
LDAP was developed at the University of Michigan; it's "lightweight" in contrast to DAP, a part of the older X.500 directory protocol for networks. It is both simpler and less secure, hence lighter. It can be used to route email in large organizations as well as look up people and machines across public or private networks.
Many current email clients, including Microsoft Outlook, Eudora, and Netscape Communicator, use some form of LDAP database to look up email addresses. Internic and Infospace are two examples of big public look-up services built with LDAP.
If this has whetted your LDAP appetite, visit the informative LDAP Roadmap & FAQ, the OpenLDAP Project, where you can help develop open implementations of programs with names like slapd andslurpd, or the always dapper LDAP Central.
LDAP, Lightweight Directory Access Protocol, is an Internet protocol that email and other programs use to look up information from a server.
Every email program has a personal address book, but how do you look up an address for someone who's never sent you email? How can an organization keep one centralized up-to-date phone book that everybody has access to?
That question led software companies such as Microsoft, IBM, Lotus, and Netscape to support a standard called LDAP. "LDAP-aware" client programs can ask LDAP servers to look up entries in a wide variety of ways. LDAP servers index all the data in their entries, and "filters" may be used to select just the person or group you want, and return just the information you want. For example, here's an LDAP search translated into plain English: "Search for all people located in Chicago whose name contains "Fred" that have an email address. Please return their full name, email, title, and description."
LDAP is not limited to contact information, or even information about people. LDAP is used to look up encryption certificates, pointers to printers and other services on a network, and provide "single signon" where one password for a user is shared between many services. LDAP is appropriate for any kind of directory-like information, where fast lookups and less-frequent updates are the norm.
As a protocol, LDAP does not define how programs work on either the client or server side. It defines the "language" used for client programs to talk to servers (and servers to servers, too). On the client side, a client may be an email program, a printer browser, or an address book. The server may speak only LDAP, or have other methods of sending and receiving data—LDAP may just be an add-on method.
If you have an email program (as opposed to web-based email), it probably supports LDAP. Most LDAP clients can only read from a server. Search abilities of clients (as seen in email programs) vary widely. A few can write or update information, but LDAP does not include security or encryption, so updates usually requre additional protection such as an encrypted SSL connection to the LDAP server.
LDAP also defines: Permissions, set by the administrator to allow only certain people to access the LDAP database, and optionally keep certain data private. Schema: a way to describe the format and attributes of data in the server. For example: a schema entered in an LDAP server might define a "groovyPerson" entry type, which has attributes of "instantMessageAddress", and "coffeeRoastPreference". The normal attributes of name, email address, etc., would be inherited from one of the standard schemas, which are rooted in X.500 (see below).
LDAP was designed at the University of Michigan to adapt a complex enterprise directory system (called X.500) to the modern Internet. X.500 is too complex to support on desktops and over the Internet, so LDAP was created to provide this service "for the rest of us."
LDAP servers exist at three levels: There are big public servers, large organizational servers at universities and corporations, and smaller LDAP servers for workgroups. Most public servers from around year 2000 have disappeared, although directory.verisign.com exists for looking up X.509 certificates. The idea of publicly listing your email address for the world to see, of course, has been crushed by spam.
While LDAP didn't bring us the worldwide email address book, it continues to be a popular standard for communicating record-based, directory-like data between programs.
