Flow identifier data of layered audiovisual data to be processed on the occurrence of congestion, as well as control code data for initiating or terminating the discard of packet data, is retained. When congestion occurs, selective transmission units perform discard initiation or termination on data having the flow identifier data indicating the layered audiovisual data retained, based on the control code data for performing the discard-initiating or -terminating operation of the packet data.