Per-packet jamming in a multi-port bridge for a local area network

Abstract

A technique for controlling the flow of packets in a multi-port bridge according to availability of resources within the bridge. The bridge includes a memory for storing packets and a plurality of ports. Each port includes a receive buffer, a transmit buffer and a memory pointer buffer. A data packet is received by the receive buffer of a port. As the packet is still being received, a look-up table is utilized to determine which is the appropriate destination port for the packet. If the memory pointer buffer in the destination port is nearly full, the destination port generates a jam request. The source port receives the jam request and, in response, discards the incoming packet and sends a jam signal. Otherwise, the memory pointer is stored in the destination port until the packet can be retrieved from the memory for transmission by the destination port. Because packets are not stored in the ports, the receive buffer and the transmit buffer will not become full and, thus, need not be checked to determine whether to transmit a jam signal. Instead, only the memory pointer buffer in the destination port for a packet need to checked to determine whether to transmit a jam signal.