Domains and Objects in Windows Server 2003
The whole point of using domainscollections or groups of computersis to make administration easier and the network more user-friendly. A domain-based network has centralized user authentication; in other words, a user account only needs to be created once and managed in one place (the domain controller), and the user can log into any machine in the domain. All user credentials and permissions are centralized and tracked by the domain's domain controller. By contrast, in a peer-to-peer network, user credentials and permissions are not centralized, but rather defined by the machine that the user is trying to access. For a user to log into a particular machine, he or she must have an account on that specific machine.
The same rule holds true for permissions. In a domain-based system, permissions can be set by an administrator for a domain account on any or all objects in the domain. An object can be a machine, file, folder, printer, or any other device that's a member of the domain.
How does a Windows Server 2003 domain keep track of all these objects as well as their permissions and attributes? With the Active Directory (AD). Think of an object as any physical or virtual resource on your network that collectively has its properties stored in AD. In AD, even the domain itself is an object, so you can have or manage multiple domain resources by using AD. Now, think of AD as a database that stores these objects on your network in a centralized manner, and that can be managed by an administrator from one location, and you've got the whole concept.
Active Directory 1.1 has introduced some improvements over previous versions:
Better replication of AD between domain controllers. Each domain controller in an AD domain is required to have a copy of that domain's Active Directory. AD data is replicated between domain controllers so that each has the most current copy. On a large network, this replicating can chew up a lot of bandwidth. AD 1.1 has been improved to replicate this data more efficiently between domain controllers, thus conserving bandwidth on a company's wide area network (WAN).
Large group support extended past 5,000 users. Previously, AD could only contain 5,000 users per group, but now the number is virtually unlimited.
Caching of user login credentials. If your company WAN goes belly up, users will still be able to log into the network, without having to find a global catalog (GC) server on the network to log in. Large companies with a domain controller at each branch office will benefit from this feature because a domain controller no longer needs to contact the GC server first in order to authenticate a user.
Typically, a large business will have multiple domain treescollections of similar domains that share the same namespace and schema. A forest is a collection of domain trees. Because each domain in the domain forest trusts the others, a user of one domain can log into another domain in the forest. In a large network environment, each domain's domain controller looks to the forest's global catalog servera machine that acts like an AD domain controller for all domains in an AD domain forestfor user authentication. A GC server basically keeps track of or keeps a copy of all objects in all of the AD domains on the network that make up the forest. Looking to the GC server for authentication allows for global access across the domain forest.
Renaming domains. Now you can rename domains without having to build a new Active Directory implementation. Let's say you have two companies (Sears and Kmart, for example), each of which has its own domain forest. Your job as an administrator is to merge these two forests. With the AD 1.1 capability of renaming domains, you can rebuild the domain while keeping the previous structure of the forest to which you're migrating.
Enhanced group policy management. The AD 1.1 architecture makes it possible to manage group policy for a domain forest. Administrators can now back up, import, restore, or copy policies across domains and sites within the forest.
As in previous versions, Windows Server 2003 comes with a set of administrative tools for managing AD. The remainder of this article briefly reviews these tools and their purposes in the enterprise.