Active Directory

It is a centralized database where it contains the information about the objects like users, groups, computers, printers etc.
AD is a centralized hierarchical Directory Database.
AD is a searchable Database.

2003 O/S. when installed (gets installed as a stand alone server) to promoting to D.C. We have to install A.D.
Domain Controller (D.C.): 

A server where A.D. is installed is called D.C.
Functionality of A.D.:
Using A.D. we can organize, manage and control resources.
It provides single point of administration.

Purpose of A.D.: 
1. Provides user logon authentication services.
2. To organize and manage user A/Cs, computers, groups and n/w resources.
3. Enables authorized users to easily locate n/w resources.

Features of A.D.: 

1. Fully integrated security system with the help of Kerberos.
2. Easy administration using group policy.
3. Scalable to any size n/w
4. Flexible (install/uninstall)
5. Extensible (modify the schema)

New features in 2003

6. Rename computer name & Domain names.
7. Cross –forest trust relationship.
8. Site-to-Site replication is faster.

Evolution of LDAP:
Earlier we had no database standard; hence TTU & ISO introduced X-500

LDAP (Light Weight Directory Access Protocol):
It is an industry standard directory access protocol used for querying and providing communication among the objects in A.D.
It is directory access protocol.
It runs on the port no. 389.

DAP: It is based on OSI model.
LDAP: Is based on TCP/IP model