code: @Override
      boolean ping_i(final boolean fwd) {
  	boolean all_alive = true;
  	final Iterator it = elements.iterator();
  	while (it.hasNext() && all_alive) {
  	    final GroupElement e = (GroupElement) it.next();
  	    if (e instanceof GroupDeviceElement || fwd) {
  		all_alive = e.ping_i(fwd) ? all_alive : false;
  	    }
  	}
  	return all_alive;
      }
docs: Ping the group - access limited to package Group