Understanding Function Levels in Windows Server 2003 Active Directory
What are the domain and forest function levels in a Windows Server 2003-basedActive Directory?
Functional levels are an extension of the mixed/native mode concept introduced in Windows 2000 to activate new Active Directory features after all the domain controllers in the domain or forest are running the Windows Server 2003 operating system.
When a computer that is running Windows Server 2003 is installed and promoted to a domain controller, new Active Directory features are activated by the Windows Server 2003 operating system over its Windows 2000 counterparts. Additional Active Directory features are available when all domain controllers in a domain or forest are running Windows Server 2003 and the administrator activates the corresponding functional level in the domain or forest.
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To activate the new domain features, all domain controllers in the domain must be running Windows Server 2003. After this requirement is met, the administrator can raise the domain functional level to Windows Server 2003 (read Raise Domain Function Level in Windows Server 2003 Domains for more info).
To activate new forest-wide features, all domain controllers in the forest must be running Windows Server 2003, and the current forest functional level must be at Windows 2000 native or Windows Server 2003 domain level. After this requirement is met, the administrator can raise the domain functional level (read Raise Forest Function Level in Windows Server 2003 Active Directory for more info).
Note: Network clients can authenticate or access resources in the domain or forest without being affected by the Windows Server 2003 domain or forest functional levels. These levels only affect the way that domain controllers interact with each other.
|Raising the domain and forest functional levels to Windows Server 2003 is a nonreversible task and prohibits the addition of Windows NT 4.0–based or Windows 2000–based domain controllers to the environment. Any existing Windows NT 4.0 or Windows 2000–based domain controllers in the environment will no longer function. Before raising functional levels to take advantage of advanced Windows Server 2003 features, ensure that you will never need to install domain controllers running Windows NT 4.0 or Windows 2000 in your environment.|
When the first Windows Server 2003–based domain controller is deployed in a domain or forest, a set of default Active Directory features becomes available. The following table summarizes the Active Directory features that are available by default on any domain controller running Windows Server 2003:
|Multiple selection of user objects||Allows you to modify common attributes of multiple user objects at one time.|
|Drag and drop functionality||Allows you to move Active Directory objects from container to container by dragging one or more objects to a location in the domain hierarchy. You can also add objects to group membership lists by dragging one or more objects (including other group objects) to the target group.|
|Efficient search capabilities||Search functionality is object-oriented and provides an efficient search that minimizes network traffic associated with browsing objects.|
|Saved queries||Allows you to save commonly used search parameters for reuse in Active Directory Users and Computers|
|Active Directory command-line tools||Allows you to run new directory service commands for administration scenarios.|
|InetOrgPerson class||The inetOrgPerson class has been added to the base schema as a security principal and can be used in the same manner as the user class.|
|Application directory partitions||Allows you to configure the replication scope for application-specific data among domain controllers. For example, you can control the replication scope of Domain Name System (DNS) zone data stored in Active Directory so that only specific domain controllers in the forest participate in DNS zone replication.|
|Ability to add additional domain controllers by using backup media||Reduces the time it takes to add an additional domain controller in an existing domain by using backup media.|
|Universal group membership caching||Prevents the need to locate a global catalog across a wide area network (WAN) when logging on by storing universal group membership information on an authenticating domain controller.|
|Secure Lightweight Directory Access Protocol (LDAP) traffic||Active Directory administrative tools sign and encrypt all LDAP traffic by default. Signing LDAP traffic guarantees that the packaged data comes from a known source and that it has not been tampered with.|
|Partial synchronization of the global catalog||Provides improved replication of the global catalog when schema changes add attributes to the global catalog partial attribute set. Only the new attributes are replicated, not the entire global catalog.|
|Active Directory quotas||Quotas can be specified in Active Directory to control the number of objects a user, group, or computer can own in a given directory partition. Members of the Domain Administrators and Enterprise Administrators groups are exempt from quotas.|
When the first Windows Server 2003–based domain controller is deployed in a domain or forest, the domain or forest operates by default at the lowest functional level that is possible in that environment. This allows you to take advantage of the default Active Directory features while running versions of Windows earlier than Windows Server 2003.
When you raise the functional level of a domain or forest, a set of advanced features becomes available. For example, the Windows Server 2003 interim forest functional level supports more features than the Windows 2000 forest functional level, but fewer features than the Windows Server 2003 forest functional level supports. Windows Server 2003 is the highest functional level that is available for a domain or forest. The Windows Server 2003 functional level supports the most advanced Active Directory features; however, only Windows Server 2003 domain controllers can operate in that domain or forest.
If you raise the domain functional level to Windows Server 2003, you cannot introduce any domain controllers that are running versions of Windows earlier than Windows Server 2003 into that domain. This applies to the forest functional level as well.
Domain Functional Level
Domain functionality activates features that affect the whole domain and that domain only. The four domain functional levels, their corresponding features, and supported domain controllers are as follows:
Windows 2000 mixed (Default)
- Supported domain controllers: Microsoft Windows NT 4.0, Windows 2000, Windows Server 2003
- Activated features: local and global groups, global catalog support
Windows 2000 native
- Supported domain controllers: Windows 2000, Windows Server 2003
- Activated features: group nesting, universal groups, SidHistory, converting groups between security groups and distribution groups, you can raise domain levels by increasing the forest level settings
Windows Server 2003 interim
- Supported domain controllers: Windows NT 4.0, Windows Server 2003
- Supported features: There are no domain-wide features activated at this level. All domains in a forest are automatically raised to this level when the forest level increases to interim. This mode is only used when you upgrade domain controllers in Windows NT 4.0 domains to Windows Server 2003 domain controllers.
Windows Server 2003
- Supported domain controllers: Windows Server 2003
- Supported features: domain controller rename, logon timestamp attribute updated and replicated. User password support on the InetOrgPerson objectClass. Constrained delegation, you can redirect the Users and Computers containers.
Domains that are upgraded from Windows NT 4.0 or created by the promotion of a Windows Server 2003-based computer operate at the Windows 2000 mixed functional level. Windows 2000 domains maintain their current domain functional level when Windows 2000 domain controllers are upgraded to the Windows Server 2003 operating system. You can raise the domain functional level to either Windows 2000 native or Windows Server 2003.
After the domain functional level is raised, domain controllers that are running earlier operating systems cannot be introduced into the domain. For example, if you raise the domain functional level to Windows Server 2003, domain controllers that are running Windows 2000 Server cannot be added to that domain.
The following describes the domain functional level and the domain-wide features that are activated for that level. Note that with each successive level increase, the feature set of the previous level is included.
Forest Functional Level
Forest functionality activates features across all the domains in your forest. Three forest functional levels, the corresponding features, and their supported domain controllers are listed below.
Windows 2000 (default)
- Supported domain controllers: Windows NT 4.0, Windows 2000, Windows Server 2003
- New features: Partial list includes universal group caching, application partitions, install from media, quotas, rapid global catalog demotion, Single Instance Store (SIS) for System Access Control Lists (SACL) in the Jet Database Engine, Improved topology generation event logging. No global catalog full sync when attributes are added to the PAS Windows Server 2003 domain controller assumes the Intersite Topology Generator (ISTG) role.
Windows Server 2003 interim
- Supported domain controllers: Windows NT 4.0, Windows Server 2003. See the “Upgrade from a Windows NT 4.0 Domain” section of this article.
- Activated features: Windows 2000 features plus Efficient Group Member Replication using Linked Value Replication, Improved Replication Topology Generation. ISTG Aliveness no longer replicated. Attributes added to the global catalog. ms-DS-Trust-Forest-Trust-Info. Trust-Direction, Trust-Attributes, Trust-Type, Trust-Partner, Security-Identifier, ms-DS-Entry-Time-To-Die, Message Queuing-Secured-Source, Message Queuing-Multicast-Address, Print-Memory, Print-Rate, Print-Rate-Unit
Windows Server 2003
- Supported domain controllers: Windows Server 2003
- Activated features: all features in Interim Level, Defunct schema objects, Cross Forest Trust, Domain Rename, Dynamic auxiliary classes, InetOrgPerson objectClass change, Application Groups, 15-second intrasite replication frequency for Windows Server 2003 domain controllers upgraded from Windows 2000
After the forest functional level is raised, domain controllers that are running earlier operating systems cannot be introduced into the forest. For example, if you raise forest functional levels to Windows Server 2003, domain controllers that are running Windows NT 4.0 or Windows 2000 Server cannot be added to the forest.