Switchcore, A.b.

Per Andersson

Jonas Alowersson

Patrik Sundstr&ouml;m

Bertil Roslund

The invention relates to a buffer memory, method and a buffer controller for queue management usable in an ATM switch. An object of the invention is to achieve a high frequency throughput of data cells in the buffer memory. This object is achieved by using a buffer memory which is organized as 256*(424&plus;8) SRAM-cells. The memory is used for holding ten queues, one for each incoming channel and two free-queues containing idle cells.

Queue management system having one read and one write per cycle by using free queues

The invention relates to a method and an arrangement for multicasting, i.e. point to multipoint transmission of a data packet. A packet is copied and transmitted to multiple addresses. In the multicasting arrangement, switch core and input and output port are connected to input and output links, respectively, for transmitting data packets. According to the invention, the input port is adapted to detect a multicasting packet received on an input link or from an output port and send the multicasting packet to an output port. The output port is adapted to detect the multicasting packet, copy the data packet, modify an address portion of the multicasting packet, send one packet on the output link and return one packet with the modified address portion to an input port. Preferably, the input port and the output port are integrated in a link interface having a direct channel for returning the data packet. The present invention improves the efficiency of multicasting by distributing copying of the data packets on several output ports of the switch core (e.g. an ATM switch).

Multicasting method and arrangement

The invention relates to a CAM/RAM memory device with a scalable and flexible structure. The device has a number of rows of memory cells. At least one address decoder is connected by word lines to the cells of the rows. Vertical bit lines for match data implement CAM functionality of the memory device. According to the invention a mask is implemented in a row of the memory cells, the mask affecting the match data on the bit lines. Preferably, the memory device is divided into segments with a mask at the top of each segment. By means of the present invention, masking is obtained by inserting masks as mask rows between the CAM rows. The mask rows are programmed by writing the mask row cells in the same way as the CAM cells. The mask rows operate directly on the bit lines for the whole underlying segment of rows. By means of this arrangement, the invention makes efficient use of the available silicon area. The memory device has a useful application as a device for handling address look-up, e.g. in a switch or router.

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Lund, Sweden

Per Andersson