Active Directory Domain

IT administrators have been working with and around Active Directory since the introduction of the technology in Windows 2000 Server. Windows 2000 Server was released on February 17, 2000 but many administrators began working with Active Directory in late 1999 when it was released to manufacturing (RTM) on December 15, 1999.

In this part of the tutorial we speal about AD domains.

What is AD Domain?

A domain is the logical container that sits directly below the forest container.

Historically, the beginning of the domain as we know it goes back to X.400 which is a telecommunications standard first recommended in 1984!

Each domain is contained in a single forest container. A domain houses other containers and objects below it. In the early days of Active Directory, the domain was originally defined as the security boundary. However, that definition has been updated and now the forest is defined as the security boundary. That was a key change that went unnoticed by some administrators.

From a scalability perspective, you can have a very large number of domains in a single forest, as follows:

  • Windows 2000 Server

Upon initial release, Active Directory supported up to 800 domains in a single forest.

  • Windows Server 2003 and later

Once you use the Windows Server 2003 forest functional level or a higher level, a single forest can support up to 1,200 domains.
Several components work together in a domain. A domain includes the following components:

  • Schema
  • Global catalog
  • Replication service
  • Operations master roles

The schema, defined earlier in the Forest section, defines objects that are used in a domain. These can be both physical and logical objects.

For example, a physical computer is represented by a computer account object, while a subnet is represented by a subnet object.

Objects have many attributes. Object attributes define the properties, limits, and format of the objects. Attributes can be multi-valued, strings, integers, Boolean (true or false), or many other types.

The specific attributes that an object has is defined by the schema.

A global catalog server stores information about every object within a domain. Administrators and users query a global catalog server to find information about objects.

For example, if an administrator needs to look up information about a user account, including address, phone number, and office location, he would query the global catalog server to retrieve the information.

More information about Active Directory basisc you will find in our AD tutorial for begginners.