Active Directory Domain

In a network, if we talk about domain then it is nothing more than a gathering or collection of computers and resources that have a common namespace. Adding to that it also shares a common security database. Moreover, the namespace of domains are stored up in the DNS which is mainly a hierarchical structure of services and object names. Now, a domain in an active directory that primarily shares the common AD database, it gets essential that the active directory and DNS namespace remain same.

Administrative controls and security policies are carried out on a domain basis and at the same time are more suitable for individual domains only. Within a domain, administrators have got right to create and manage different resources and objects. In addition, an active directory domain usually consists of different AD objects like users, groups, computers, OU, etc. As a result, it can be said that a domain is more like a prime logical structure of the active directory, while the physical structures are the domain controllers and sites.

However, it is important to note that when more than one domain is clustered together, a domain tree is formed. Every single domain present within a domain tree usually shares a contiguous DNS namespace and naming structure. Talking about a domain tree, the root domain is primarily referred as the Parent domain while the multiple domains that are added to it are considered as the Child Domains. A collection of various multiple domain trees is termed as a forest. Inside a forest, the domains are connected through a two-way transitive trusts and at the same time also shares a common global record and schema. The root domain in a forest consists of specific groups like the Domain Naming Master Role, Schema Master Role, Enterprise Admins group and Schema Admins group.

Domain Functional Levels

The domain functional levels usually manage and restrict all the functions that are conducted within a domain. If the domain functional level is upgraded to Windows Server 2003 functional level, a few superior active directory features become available:

• Windows 2000 Native supports domain controllers running Windows 2000 and Windows Server 2003.
• Windows 2000 Mixed supports domain controllers running Windows NT 4.0, Windows 2000 and Windows Server 2003.
• Windows Server 2003 Interim supports domain controllers running Windows NT 4.0 and Windows Server 2003.
• Windows Server 2003 supports domain controllers running Windows Server 2003.

Domain Design Factor

While designing an active directory domain, the following factors should be kept in mind:

• Business requirements: Based upon the business requirements of the organization, the logical structure of active directory needs to be designed.
• Geographical factors: To control replication of diverse regions within the enterprise, it is important that one create and implement a geographic domain design so that the domain controllers replicate the changes only in their local domain.
• Domain Name strategy: Domain name has to be unique and different. Each domain is assigned a NetBIOS name and DNS name.
• WAN link costs: The price tag of implementing WAN links vary from one country to another.