code: public boolean
  isCurrent() {
  	BasicHandler handler = getBasicHandler();
  	return (handler.axfr == null && handler.ixfr == null);
  }
docs: Returns true if the response indicates that the zone is up to date.
  This will be true only if an IXFR was performed.
  @throws IllegalArgumentException The transfer used the callback interface,
  so the response was not stored.