Method and apparatus for port memory multicast common memory switches

A switch for tracking multicast cell copies and including a plurality of output ports from which cell copies are transmitted toward destinations, the switch comprising:

• a plurality of output port registers, each output port register being associated with at least one switch output port;
• a port memory controller for receiving a bit map on the enqueue of a cell into the switch, the bit map including a bit corresponding to each output port register, the controller including;
• means for writing to each output port register the bit from the bit map corresponding to that port register;
• means for clearing the bit in the output port register associated with the output port from which a cell copy is dequeued while reading the bits in the other output port registers;
• and
• means for testing the bits read from the other output port registers to determine the value of the bits read.

A method for tracking multicast cell copies in a switch in an ATM network, the switch including a port memory controller and a plurality of groups of output ports, each group having an associated output port register, the method comprising the steps of:

• enqueueing into the switch a cell to be dequeued from the switch;
• receiving a bit map into the port memory controller on the cell enqueue, the bit map including a bit corresponding to each output port register;
• writing to each output port register the bit from the bit map corresponding to that output port register, the bit indicating that at least one copy of the enqueued cell is to be dequeued from the group of output ports associated with that output port register;
• maintaining a count of the copies of the cell that have been dequeued from each group of output ports;
• determining when the last copy of the cell has been dequeued from a group of output ports;
• and
• clearing the bit in the output port register after the last copy of the cell has been dequeued from the group associated with the output port register.

A switch for tracking multicast cell copies and including a plurality of output ports from which cell copies are transmitted toward destinations, the switch comprising:

• a plurality of output port registers, each output port register being associated with at least one switch output port;
• and
• first and second port memory controllers, at least one of the controllers receiving a bit map on the enqueue of a cell into the switch, the bit map including a bit corresponding to each output port register in a group of output port registers associated with the at least one controller that received the bit map, the controller including
• means for writing to each output port register in the group the bit from the bit map corresponding to that port register.

A method for tracking multicast cell copies in a switch in an ATM network, the switch including first and second port memory controllers, a plurality of output ports, a data store for storing cells enqueued to the switch, and a plurality of output port registers, each output port register being associated with at least one switch output port, the method comprising the steps of:

• enqueuing a cell into the switch;
• receiving a bit map into at least one of the port memory controllers on the enqueue of the cell, the bit map including a bit corresponding to each output port register in a group of registers associated with the at least one controller that received the bit map;
• writing to each output port register in the group a bit from the bit map corresponding to that port register;
• storing the enqueued cell at a cell address in the data store memory;
• directing the bit map to the one port memory controller based on the cell address;
• and
• determining whether the cell address is even or odd.

A method for tracking multicast cell copies in a switch in an ATM network, the switch including first and second port memory controllers, a plurality of output ports, a data store for storing cells enqueued to the switch, and a plurality of output port registers, each output port register being associated with at least one switch output port, the method comprising the steps of:

• enqueuing a cell into the switch;
• receiving a bit map into at least one of the port memory controllers on the enqueue of the cell, the bit map including a bit corresponding to each output port register in a group of registers associated with the at least one controller that received the bit map;
• writing to each output port register in the group a bit from the bit map corresponding to that port register;
• storing the enqueued cell at a cell address in the data store memory;
• directing the bit map to the one port memory controller based on the cell address;
• and
• writing the bit of the bit map to the output port register at a corresponding cell address in that register.

A method for tracking multicast cell copies in a switch in an ATM network, the switch including first and second port memory controllers, a plurality of output ports, and a plurality of output port registers, each output port register being associated with at least one switch output port, the method comprising the steps of:

• enqueuing a cell into the switch;
• receiving a bit map into at least one of the port memory controllers on the enqueue of the cell, the bit map including a bit corresponding to each output port register in a group of registers associated with the at least one controller that received the bit map;
• writing to each output port register in the group a bit from the bit map corresponding to that port register;
• dequeuing a copy of the cell from an output port of the switch;
• clearing the bit in the output port register of the group associated with the output port from which the cell copy was dequeued;
• and
• reading the bits in the other output port registers of the group.