We have published guidelines for planning and deploying read-only domain controllers (RODCs). There is a Read-Only Domain Controller (RODC) Branch Office Guide available on TechNet (http://technet.microsoft.com/en-us/library/dd734758(WS.10).aspx) and a .doc version on the Microsoft Download Center (http://go.microsoft.com/fwlink/?LinkId=153714). There is another guide that covers RODCs in DMZ scenarios named Active Directory Domain Services in the Perimeter Network (Windows Server 2008) on TechNet at http://technet.microsoft.com/en-us/library/dd728034(WS.10).aspx.
You can also learn a lot conceptual information about RODCs by reading Read-Only Domain Controller (RODC) Planning and Deployment Guide at http://technet.microsoft.com/en-us/library/cc771744.aspx. This guide covers information that is applicable to any deployment scenario that invloves RODCs. The branch office and DMZ guides cover just the information that is pertinent to each of those scenarios.
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