A, B, C and D will forward to NS1, then NS2, then other backup servers. Determines port on which server sends UDP queries to other DNS servers. Administrators can easily identify, monitor and control forwarding queries. Determines whether server attempts to clean up responses to avoid cache pollution. Limits number of A records put in answer to query.
Administrators can reduce logging to avoid DoS because of log entries.
Administrators can log to the packet level if needed. Administrators can control a specific servers behavior. Block an internal development DNS server and make the client fall back to a secondary server. Don't forget to stop and start the service for the changes to be in effect. I'm in the process of looking under the DNS hood of Windows 2000.