LDAP, Lightweight Directory Access Protocol,
is an Internet protocol that email programs
use to look up contact information from a server,
such as ClickMail Central Directory. As soon
as Internet email became popular, it was clear
we needed a good phone book. Printed directories
were obsolete before the ink was dry. Older
Internet methods of looking up names, such as
whois, Ph, or finger, were limited or arcane.
Every email program has a personal address book,
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's why software companies such as Microsoft,
IBM, Lotus, and Netscape agreed 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
For example, here's an LDAP search translated
into plain English:
"Search for all people located in Chicago
whose name contains "Eddi" that have
an email address. Please return their full name,
email, title, and description." (However,
many email clients have more limited search
and retrieval options.) "Permissions"
are set by the administrator to allow only certain
people to access the LDAP database, and optionally
keep certain data private. LDAP servers also
provide "authentication" service,
so that web, email, and file-sharing servers
(for example) can use a single list of authorized
users and passwords.
LDAP was designed at the University of Michigan
to adapt a complex enterprise directory system
(called X.500) to the modern Internet. A directory
server runs on a host computer on the Internet,
and various client programs that understand
the protocol can log into the server and look
up entries. 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 such as
BigFoot and Infospace, large organizational
servers at universities and corporations, and
smaller LDAP servers for workgroups. You probably
already have an LDAP-aware client installed
on your computer.
Most modern email clients are set up to search
an LDAP directory for email addresses. These
include Outlook, OS X Mail, Eudora, Netscape,
QuickMail Pro, and Mulberry. LDAP has broader
applications, such as looking up services and
devices on the Internet (and intranets). Netscape
Communicator can store user
preferences and bookmarks on an LDAP server.
There is even a plan for linking all LDAP servers
into a worldwide hierarchy, all searchable from
LDAP promises to save users and administrators
time and frustration, making it easy for everyone
to connect with people without frustrating searches
for email addresses and other trivia.
[ Submitted by Siddharth Wankade ]