Lightweight Directory Access Protocol





Lightweight Directory Access Protocol (LDAP) is a protocol for accessing
on-line directory services.

LDAP was defined by the IETF as a better way to make use of X.500
directories. The Directory Access Protocol (DAP) was seen as too complex for
simple internet clients to use. LDAP defines a relatively simple protocol
for updating and searching directories running over TCP-IP.

The common term "LDAP directory" is misleading. There is no specific type of
directory that is as an "LDAP directory". It is fair to use the term to
describe any directory which is accessible using the LDAP protocol and can
identify objects in the directory with X.500 identifiers. There are some
directories, such as OpenLDAP, which were primarily designed as repositories
for X.500 data using access by LDAP, but that doesn't make them any more of
an "LDAP directory" than any other directory accessible by the LDAP
protocol.

LDAP is gaining support from vendors such as Novell, Sun, HP, IBM/Lotus,
SGI, AT&T, Banyan, Oracle (through Oracle Internet Directory) and Microsoft
(through Active Directory).

An LDAP directory entry is a collection of attributes with a name, called a
distinguished name (DN). The DN refers to the entry unambiguously.
Each of the entry's attributes has a type and one or more values. The types
are typically mnemonic strings, like "cn" for common name, or "mail" for
e-mail address.

The values depend on the type. For example, a mail attribute might contain
the value "donald.duck@disney.com". A jpegPhoto attribute would contain a
photograph in binary JPEG/JFIF format.

LDAP directory entries are arranged in a hierarchical structure that
reflects political, geographic, and/or organisational boundaries. Entries
representing countries appear at the top of the tree. Below them are entries
representing states or national organisations. Below them might be entries
representing people, organisational units, printers, documents, or just
about anything else.

RFCs on LDAP

   * RFC 1777 LDAP
   * RFC 1778 String Representation of Standard Attribute Syntaxes
   * RFC 1959 URL Format
   * RFC 1960 String Representation of Search Filters
   * RFC 1823 C API