What Are the Pieces in the Congestion Control Puzzle ?

The three flow-control techniques introduced in this paper are backpressure flow control, alpha scheduling, and balanced injection. Our variations on backpressure flow control essures that all the buffers in a node are not filled with one particular category of packet, such as those destined for the same node, so that buffers are available for other packets. Alpha scheduling exploits the distinction between message latency and packet latency to maximize the effective performance of the interconnect from the perspective of applications. Balance injection throttles the injection of traffic into a node from outside the network based on local congestion as measured by local buffer usage. These three flow-control techniques, together, provide a significant increase in fabric performance, both in sustainable throughput and in message latency, under a wide variety of realistic traffic patterns.