What Are The Domain Functional Levels In The Windows Server 2003?

There are 4 domain functional levels in the Windows Server 2003.They are

1-Windows 2000 Mixed:
It is the default domain functional level.

2-Windows 2000 Native
After upgrading to this level, additional features such as group nesting, universal groups, SID History become available.

3-Windows Server 2003 Interim
It provides support for both Windows NT and Windows Server 2003 domain controllers but does not provide new features.

4-Windows Server 2003
It only supports Windows Server 2003 domain controllers but its important to use Windows Server 2003 full features.