Windows Server 2000
The Windows 2000 forest functional level provides all Active Directory Domain Services features that are available in Windows 2000 Server. If you have domain controllers running later versions of Windows Server, some advanced features will not be available on those domain controllers while this forest is at the Windows 2000 functional level.
Windows Server 2003
The Windows Server 2003 forest functional level provides all features that are available in Windows 2000 forest functional level, and the following additional features:
- Linked-value replication, which improves the replication of
changes to group memberships.
- More efficient generation of complex replication topologies
by the KCC.
- Forest trust, which allows organizations to easily share
internal resources across multiple forests.
Any new domains that are created in this forest will automatically operate at the Windows Server 2003 domain functional level.
Windows Server 2008
This forest functional level does not provide any new features over the Windows 2003 forest functional level. However, it ensures that any new domains created in this forest will automatically operate at the Windows Server 2008 domain functional level, which does provide unique features.
Windows Server 2008 R2
The Windows Server 2008 R2 forest functional level provides all the features that are available in the Windows Server 2008 forest functional level, plus the following additional feature:
- Recycle Bin, which, when it is enabled, provides the ability to restore
deleted objects in their entirety while Active Directory Domain
Services is running.
Any new domains that are created in this forest will operate by default at the Windows Server 2008 R2 domain functional level.