It is at this juncture (when centralized computing and resource management was a demand that grew imperative every day) that Microsoft came up with Windows NT, which simplified and enhanced the domain-centric approach to resource management in its directory service. Soon, Microsoft enhanced NT further and introduced Active Directory, which provided everything expected of a multipurpose directory service including:
User and Resource management
Centralized directory management
Directory enabled infrastructure
Directory enabled applications
To function as a multipurpose directory service, there are some core requirements that must be met. The requirements include scalability, management of active directory objects, simple and flexible security. By comparing Windows NT with Active Directory, we will be able to understand how Active Directory succeeds in functioning as a multipurpose directory service and the extent of enhancement it has upon its predecessor.
Maximum database size is 40 MB with a maximum of 40,000 users.
Maximum database size is 16 TB with millions of objects per forest.
Does not support the addition of new objects
Schema is fully extensible
Supports Microsoft API
Supports LDAP based access to objects. LDAP is the standard protocol used by directories.
Single master replication
Multimaster replication across the domain controllers
Administration boundaries can vary from the entire forest level to individual attribute level of an object
NetBIOS is used
DNS is used
Simple trust relationship.
Transitive trust relationship.
Eg. If domain A trusts Domain B and if Domain B trusts Domain C, there is no automatic trust created between Domains A and C
Eg. If domain A trusts Domain B and if Domain B trusts Domain C, there is automatic trust created between Domains A and C