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:
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.
Features | Windows NT | Active Directory |
Scalability | 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. |
Schema Extensibility | Does not support the addition of new objects | Schema is fully extensible |
Access methodologies | Supports Microsoft API | Supports LDAP based access to objects. LDAP is the standard protocol used by directories. |
Replication | Single master replication | Multimaster replication across the domain controllers |
Administration | Per-domain basis | Administration boundaries can vary from the entire forest level to individual attribute level of an object |
Name Resolution | NetBIOS is used | DNS is used |
Trust relationship | 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 |
Most importantly, the growth of Active Directory over Windows NT is obvious because of its capability to satisfy the requirements to function as a multipurpose directory service.