Dual key controlled content addressable memory for accessing packet switch data buffer for multicasting data packets

A content-addressable memory having a plurality of storage regions that store respectively different address pointer words, a respective storage region containing:

• a first plurality of content addressable memory cells, the contents of which are associated with a first field of a respective address pointer word that identifies data to be accessed from a storage location in a memory;
• and
• a second plurality of content addressable memory cells, the contents of which are associated with a second field of said respective address pointer word that identifies the address of said storage location in said memory, and wherein
• respectively different address pointer words stored in multiple ones of said plurality of storage regions of said content addressable memory contain respectively different first fields associated with respectively different ones of multiple instances of accessing said data from said storage location in said memory, and a common second field that identifies the address of said storage location in said memory for each of said multiple instances of accessing said data from said storage location in said memory.

For use with a communication system in which packetized data is to be controllably multicast to a plurality of recipients in accordance with multicast criteria, an output port data distribution architecture for buffering and controllably supplying packetized data for delivery to multiple ones of a plurality of output ports associated with said recipients comprising:

• a packet buffer containing a plurality of storage locations that store data packets intended for delivery to one or more of said plurality of output ports;
• a content-addressable memory containing a plurality of storage regions that store respectively different address pointer words, each address pointer word containing a respectively different key field that is used to identify a data packet to be delivered to one of said plurality of output ports, and an address field that identifies the address of one of said plurality of storage locations of said packet buffer in which said data packet is stored;
• and
• a packet buffer access controller, which is operative to couple a key to key fields of address pointer words of said plural storage regions of said content-addressable memory, and thereby access contents of the address field of an address pointer word whose key field contains said key, the accessed address field contents being coupled to read out a data packet stored in one of said plurality of storage locations of said packet buffer, said accessed address field contents being coupled to the address fields of address pointer words stored in said content-addressable memory, and wherein said content-addressable memory is operative to output a signal representative whether said accessed address field contents are contained in the address field of another address pointer word stored in said content-addressable memory.

For use with a communication system in which a data packet is to be multicast to a plurality of recipients, a method of buffering and controllably supplying said data packet for delivery to multiple ones of a plurality of output ports associated with said recipients comprising the steps of:

• (a) storing said data packet to be multicast in only a single data packet storage location of a data packet buffer;
• (b) storing, in a content-addressable memory, a plurality of respectively different address pointer words, containing respectively different first fields, associated with multicasting of said data packet to multiple ones of said plurality of output ports, and a common address field that identifies said single data packet storage location of said packet buffer in which said data packet to be multicast is stored;
• (c) coupling respectively different keys to said respectively different first fields of said respectively different address pointer words stored in said content addressable memory, to read out contents of said common address field for application to said packet buffer, and thereby cause said data packet to be read out from said single data packet storage location of said packet buffer and multicast to said multiple ones of said plurality of output ports;
• and
• (d) in the course of reading out said contents of said common address field for application to said packet buffer in step (c), coupling said contents of said common address field to address fields of all of the address pointer words stored in said content addressable memory, to determine whether said data packet has been multicast in accordance with each address pointer word stored in said content addressable memory.