Broadcom Corporation

Jason Chao

William Dai

Yao-Ching Liu

Jun Cao

Cheng-Chung Shih

A shared memory packet switching device includes: a shared memory providing a shared memory space; an input logic unit associated with at least one receive port, and being operative to determine whether the associated receive port is saturated by determining whether a number of packets received via the associated receive port and currently stored in the shared memory exceeds a drop threshold value; a packet routing control unit operative to determine a destination one of the transmit ports for each of the received data packets; and an output logic unit associated with at least one of the transmit ports, the output logic unit being communicatively coupled with the packet routing control unit, and being operative to determine whether the associated transmit port is congested by determining whether a number of packets currently stored in the shared memory that are to be transmitted via the associated transit port exceeds a congestion threshold value, and also being operative to generate an associated output full signal indicative of whether the associated transmit port is congested. The input logic unit is responsive at least in part to each of the output full signals, and further operative to cause a selected packet received via the associated receive port to be dropped if the associated receive port is currently saturated and the output full signals indicate that a destination transmit port associated with the selected packet is currently congested.

Starvation free flow control in a shared memory switching device

A packet switching fabric includes means forming a data ring, means forming a control ring, and means forming a plurality of data communication network links each having at least one network node coupled thereto. The fabric further includes a plurality of output queuing controlled switching devices coupled together by the data ring means and the control ring means so that the network links can be selectively communicatively coupled. Each of the output queuing controlled switching devices includes control ring processing means operative to develop, transmit and receive control messages to and from adjacent ones of the devices via the control ring means. The control messages provide for controlling packet transfer operations including transmitting associated selected ones of the received data packets from the associated source device to the associated destination device via an associated source-destination channel path including associated ones of the data ring segments and an associated one of the memory unit links. A channel resource patrol message is passed by each one of the devices, the patrol message carrying channel bandwidth information indicative of bandwidth available on the data ring means and bandwidth available on memory unit links. The control ring processing means is responsive to the channel bandwidth information and operative to read and modify the channel bandwidth information for the purpose of managing data transfer via the data ring means and via each of the memory unit links.

Packet switching fabric having a segmented ring with token based resource control protocol and output queuing control

A queue length arbiter system provides for selecting from a plurality of N queues requiring access to a resource. The system includes: an arbitration circuit; and a plurality of weight circuits each being associated with a corresponding one of the queues, and being operative to store a corresponding weight count value, and also being operative to initialize the corresponding weight count value to a corresponding initial weight value determined based on a length value indicative of a number of data portions enqueued at the corresponding queue at an initial time, and being further operative to decrease the corresponding weight count value in response to a corresponding one of a plurality of grant signals, and also being operative to generate a corresponding one of a plurality of weight count signals, the corresponding weight count signal carrying the corresponding weight count value. The arbitration circuit includes: a plurality of weight checking circuits associated with corresponding ones of the queues, each checking circuit being operative to generate a corresponding one of a plurality of select signals indicative of a corresponding selected one of the queues in response to each of the weight count signals, the corresponding selected queue being determined based on the weight count values; and a resolving circuit responsive to each of the select signals, and being operative to choose one of the weight checking circuits, and also being operative to provide the grant signals, the grant signals indicating a granted queue that is selected by the chosen weight circuit.

Quantized queue length arbiter

A packet switching fabric includes a data ring, a control ring, a plurality of network links each coupled to at least one network node, and a plurality of switching devices coupled together by the data ring and the control ring so that the network links can be selectively communicatively coupled. Each of the switching devices includes: a data ring sub-system for transmitting and receiving bursts of data via data ring channels concurrently active on the data ring; a network interface coupled to the data ring sub-system and having at least one network port for transmitting and receiving data packets to and from one of the network links, the network interface also having a packet buffer for storing the data packets, the packet buffer providing bursts of packet data to the data ring sub-system via a plurality of concurrently active packet buffer channels; and a control ring sub-system coupled to the data ring sub-system and to the network interface and being responsive to control messages received from an adjacent one of the devices via the control ring, and operative to develop and transmit the control messages to an adjacent one of the devices via the control ring, the control messages for reserving bandwidth resources used in setting up and controlling the data ring channels and the packet buffer channels, the control ring sub-system also being operative to perform queuing operations for controlling the transfer of the bursts of packet data from the packet buffer to the data ring sub-system.

Growing community of inventors

Cupertino, CA, United States of America

Jason Chao