How does LDAP works , What is LDAP , Practical use of LDAP

what is LDAP

LDAP stands for Lightweight Directory Access Protocol. As it says LDAP is Lightweight protocol used to access directory service.
So what is a directory service?
Directory service is something similar to a database but with some major differences as follows

+ Directory contains more detailed information
+ Directories are attribute based
+ It is more read than written.
+ Supports high-volume search/lookup
+ Supports replication

How does LDAP works

LDAP works on a Client-Server model.One or more server can act as directory tree or back end database.LDAP client request information and servers provides it.
LDAP server runs sldapd deamon and tree structure is written in LDIF file.

Sldapd config file

http://www.openldap.org/doc/admin21/slapdconfig.html
A simple practical use of LDAP

A new employee joining the company requires access to many resource to perform his duties. Organization will define group of  authentication for each team and levels.Once he joins the company HR would had his record to the LDAP server and the respective managers will add him to the groups depending on the role and group he joins. Thus he get the appropriate access. Main advantage here is , if he needs to move to a different group current permissions can be revoked and new once can be granted easily.Thus complexity in managing identity is reduced.Even the user can use same password for multiple applications , if the applications are LDAP authentication supported.

Windows LDAP servers

if any one know some good LDAP servers which can be tried for free on internet, please comment.
Reference
RFC 2251

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