Sending SYN + ACK packet cannot be filtered, and more efficient than sending RST packet(may be filtered)
Sending SYN + ACK packet cannot be filtered, and more efficient than sending RST packet(may be filtered)
After DNS received query packet , DNS parse the packet and process proper in order to send proper response
But DQB sends the response after FQDN in query is matched entry in database in DQB.
Searching costs are similar, then no parsing FQDN and no process choice are good for performance.