Technique for optimizing cut-through for broadcast and multi-cast packets in a multi-port bridge for a local area network

Abstract

A technique for optimizing cut-through for broadcast and multi-cast data packets in a multi-port bridge for a local area network (LAN). The multi-port bridge includes a plurality of ports for communicating packets with an associated segment of the LAN. Each of the ports is coupled to a data bus for communicating packets among the ports. A packet buffer is coupled to the data bus for temporarily storing packets undergoing communication between the ports. At least one of the ports includes a transmit packet store for receiving packets to be transmitted by the port and a broadcast packet store for receiving broadcast and multi-cast packets to be transmitted by the port wherein the broadcast packet store receives a broadcast or multi-cast packet only when the transmit packet store is occupied. The transmit packet store can receive a packet from the packet buffer or at the same time the packet buffer receives the packet. Because the broadcast packet store receives the broadcast or multi-cast packet from the data bus at the same time the packet buffer receives it, even when the transmit packet store is occupied, the invention minimizes the number of ports which need to retrieve such a broadcast or multi-cast packet from the packet buffers. This minimizes bandwidth of the data bus occupied by retrieving broadcast and multi-cast data packets from the packet buffers.