"But needing “multiple” DNS Root Zone Servers and coming up with the number 13 appears to be somewhat curious. It seems such an odd limitation in the number of root servers given that a common rule of thumb in computer software design is Willem van der Poel’s Zero, One or Infinity Rule, which states a principle that either an action or resource should not be permitted (zero), should happen uniquely (one) or have no arbitrary limit at all (infinity). For root servers, it appears that we would like more than one root server. But why set that number to 13?"