One of the most exciting technologies coming in Windows Server 2008 is improved Active Directory domain controller
security features. Called read-only domain controller (RODC), this new domain controller technology includes a number of features aimed at improving overall security of the Active Directory environment at branch locations.
One way in which the RODC improves the security of your AD environment is by providing a read-only copy of the Active Directory database. This means that no one -- user or administrator -- can make changes to the Active Directory database from a read-only domain controller.
You can connect to an RODC to read almost all of the same information just as you can from a writeable DC, but you will not be able to perform any write operations without connecting to a writeable DC using Remote Desktop. Or, you could update Active Directory by connecting to a writeable DC using an MMC snap-in, script or command-line tool.Read the entire article at SearchWinIT.com