You can specify only a failure threshold percentage using the UNRESPONSIVETHRESHOLD resolver setup statement, or you can use the default value, which is 25%. In either case, the resolver reacts to unresponsive name servers by notifying the network operator of the condition and continues to send DNS queries to the unresponsive name server. The network operator notification function collects name-server statistics at 1-minute intervals, but makes decisions based on the last five monitoring intervals. These intervals are called sliding 5-minute windows.