Computer network switching system with expandable number of ports

A method for transferring data between ports of a switching fabric circuit wherein a first plurality of ports is coupled to local area network (LAN) segments that transfer data at a first rate and a second plurality of ports is coupled to LAN segments that transfer data at a second rate, the method comprising the steps of:

• indicating a start of a synchronization period;
• requesting high priority access to a bus of switching fabric circuit by at least one of a plurality packet processors coupled to the first and second plurality of ports and the bus;
• granting all high priority access requests the synchronization period;
• requesting low priority access to the bus by at least one of the plurality of packet processors coupled to the first and second plurality of ports after all high priority access request have been granted;
• granting low priority access requests for the remainder of the synchronization period;
• and
• indicating a start of a new synchronization period by the central arbiter of the switching fabric circuit.

A method for forwarding a multiple destination packet in a switching link of a switching fabric circuit, comprising the steps of:

• monitoring a bus of the switching link by a plurality of packet processors coupled to the bus;
• selecting a first packet processor to transmit the multiple destination packet;
• indicating via the bus that the first packet processor is selected to transmit the multiple destination packet during a synchronization period;
• indicating by the first packet processor that the first packet processor has the multiple destination packet to transfer during the synchronization period;
• transmitting a port of exit mask on the bus by the first packet processor, the port of exit mask indicating which of the plurality of packet processors are destination packet processors for the multiple destination packet;
• indicating by the destination packet processor that the destination packet processors are ready to receive the multiple destination packet;
• and
• transmitting the multiple destination packet via the bus by the first packet processor during the synchronization period.

A method for transferring a data packet comprising the steps of:

• requesting control of a bus by a first port to transfer the data packet during a synchronization period;
• granting control of the bus to the first port by a central arbiter;
• transferring destination information by the first port via the bus during the synchronization period, the destination information indicating a second port as a destination of the data packet;
• requesting control of the bus by the second port in response to receiving the destination information;
• granting control of the bus to the second port by the central arbiter;
• transferring information by the second port via bus indicating to the first port that the second port is ready to receive the data packet;
• and
• requesting access of the bus by the first port to transfer the data packet to the second port during the synchronization period.