// external ports are unknown The reason is that it will make
// rate information propagate from an actor input port to
// another actors input port that are connected on the inside
// to the same external input port. See
// BaseSDFScheduler.setContainerRates.
Iterator ports = model.portList().iterator();
while (ports.hasNext()) {
IOPort port = (IOPort) ports.next();
if (_debugging && VERBOSE) {