A control system for packet transmission. A forward control unit receives a packet providing a port count through an input port and implements a lookup operation. A queue control unit determines whether the port count is greater than a first predetermined value, and, if not, outputs the packet through a first port, and, if so, sends a first message. A multicast forward control unit receives the first message, adds one to a first packet count, determines whether the first packet count is greater than a threshold value, and, if so, sends a stop forward message to the forward control unit but does not send a grant message. The forward control unit receives the stop forward message and does not transmit subsequent packets to the first port but to a second port directly.