code: private boolean startUpdate(UpdateRackHeartbeat updateRack,
                                UpdatePodSystem updatePod)
    {
      long now = CurrentTime.currentTime();
      
      if (_lastHubTime + getTimeout() < now) {
      }
      else if (_lastRackCrc != updateRack.getCrc()) {
      }
      else if (updatePod != null && _lastPodCrc != updatePod.getCrc()) {
      }
      else {
        return false;
      }
      
      _lastHubTime = now;
      _lastRackCrc = updateRack.getCrc();
      
      if (updatePod != null) {
        _lastPodCrc = updatePod.getCrc();
      }
      
      return true;
    }
docs: Only send updates on changes or timeouts.