code: public void disconnect(Destination d) throws KNXLinkClosedException
  	{
  		if (detached)
  			throw new KNXIllegalStateException("TL detached");
  		if (d.getState() != Destination.DESTROYED
  			&& d.getState() != Destination.DISCONNECTED)
  			disconnectIndicate(getProxy(d), true);
  	}
docs: /* (non-Javadoc)
  @see tuwien.auto.calimero.mgmt.TransportLayer#disconnect
  (tuwien.auto.calimero.mgmt.Destination)