What is LDAP?
The Lightweight Directory Access Protocol (LDAP) is a protocol for accessing online directory services. It runs directly over TCP, and can be used to access a standalone LDAP directory service or to access a directory service that is back-ended by X.500.
What is a directory service?
A directory is like a database, but tends to contain more descriptive, attribute-based information. The information in a directory is generally read much more often than it is written. As a consequence, directories don't usually implement the complicated transaction or roll-back schemes regular databases use for doing high-volume complex updates. Directory updates are typically simple all-or-nothing changes, if they are allowed at all. Directories are tuned to give quick-response to high-volume lookup or search operations. They may have the ability to replicate information widely in order to increase availability and reliability, while reducing response time. When directory information is replicated, temporary inconsistencies between the replicas may be OK, as long as they get in sync eventually.
How does LDAP work?
LDAP directory service is based on a client-server model. One or more LDAP servers contain the data making up the LDAP directory tree. An LDAP client connects to an LDAP server and asks it a question. The server responds with the answer, or with a pointer to where the client can get more information (typically, another LDAP server). No matter which LDAP server a client connects to, it sees the same view of the directory; a name presented to one LDAP server references the same entry it would at another LDAP server. This is an important feature of a global directory service, like LDAP.
LDAP Software
- LDAP Client Software
-
LDAP Client software has a page of its own, since the list is large:
LDAP Client Software Page - LDAP Gateway Software
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1. in.xfingerd (finger gateway)
2. mail500 (LDAP-aware mailer)
3. fax500 (mail-to-fax gateway)
4. go500 (simple Gopher gateway)
5. go500gw (a general Gopher gateway)
6. rcpt500 (directory lookup via e-mail)
7. web500gw (HTTP gateway)
8. CX (PH/CSO Gateway)
- LDAP Server Software
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1. ldap (front end for an X.500 DSA)
2. slapd (standalone LDAP directory server)
3. slurpd (standalone LDAP update replication daemon)
Resources of LDAP
- LDAP Implementation
The University of Michigan LDAP implementation includes libraries for writing LDAP clients, and it has been ported to many flavors of Unix as well as to the Macintosh, MS-DOS, Microsoft Windows, and VMS:
- Collection of patches
- Documentation
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1. LDAP Documentation
2. The SLAPD and SLURPD Administrators Guide University of Michigan 3. Referrals Within the LDAPv2 Protocol
- Some other related resources include
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1. LDAP World (Critical Angle Inc.)
2. LDAP mirror at SUNET (Sweden)
3. LDAP mirror at SURFNET (Netherlands)
4. LDAP mirror at VSE (Czech Republic)
5. LDAP http mirror at Univ. of Technology Vienna (Austria)
6. LDAP ftp mirror at Univ. of Technology Vienna (Austria)
7. Yahoo's List of Internet Directory Service Links
8. LDAP Tutorial and FAQ (Stanford University)
Standards
- RFC-1777 Lightweight Directory Access Protocol.
- RFC-1558 A String Representation of LDAP Search Filters
- RFC-1778 The String Representation of Standard Attribute Syntaxes
- RFC-1779 A String Representation of Distringuished Names
- RFC-1798 Connectionless LDAP
- RFC-1823 The LDAP Application Program Interface
- RFC-1959 An LDAP URL Format
- Update to RFC-1777: LDAPv2 Protocol
- Update to RFC-1778: LDAPv2 Attributes
- X.500 standards
- Current State of the LDAP Protocol Standards
Papers
-
U-M LDAP team members have published several LDAP-related papers, some of
which are available online:
- A Scalable, Deployable, Directory Service Framework for the Internet (INET '95, HTML)
- The same document is also available as CITI Technical Report 95-7 (PostScript format)
- The Lightweight Directory Access Protocol: X.500 Lite (CITI Tech Report 95-8, Postscript)
- An X.500 and LDAP Database: Design and Implementation (Postscript)
Products and Prototypes
- OpenLDAP Home Page
- LDAP Browser/Editor
- Linux Directory Services
- Perl-LDAP Homepage
- Netscape
- Mozilla
- Novell
- UMich
- PAM LDAP Module
- web2ldap: WWW gateway to LDAP server
- Windows LDAP Browser
- Python-LDAP
Related sites
- An LDAP Roadmap & FAQ : A tutorial aid to navigating various LDAP and X.500 Directory Services resources on the Internet
- Innosoft's LDAP World
- LDAP Linux HOWTO
- LDAPCentral
- PHP: Manual of LDAP functions
- Alan's Linux Information Center Project: LDAP
- Secure LDAP
- Public LDAP Server
- TCI LDAP Resources
- AE SLAPD LDAP v3 server for Windows 95/98/NT
- hotLDAP - LDAP Resources and Sources of Information