A New Mechanism to Identify Congesting Packets in High-Performance Interconnection Networks

Interconnection networks are key components in Data Centers and Supercomputers, as they must guarantee high communication bandwidth and low latency under very demanding communication patterns generated by computing-and data-hungry applications and services. These traffic patterns may generate congestion, clogging different parts of the intercon-nection network, and impact the overall system performance if no countermeasures are taken. Unfortunately, congestion detection mechanisms used by congestion control techniques in current interconnection networks, such as DCQCN, do not precisely identify which packets contribute to generating congestion, so false-positive congestion detection events are possible. To overcome these problems, in this paper, we propose a new mechanism, called Enhanced Congestion Point (ECP), which accurately identifies packets that truly contribute to congestion. Specifically, ECP monitors packets at the head of the switch ingress queues and identifies them as congesting when a queue occupancy is over a given threshold and a crossing request for that packet within the switch is rejected. In addition, to solve the false-positive congestion-detection events, ECP defines are-evaluation mechanism that cancels the identification of congesting packets, if they no longer contribute to congestion after congestion areas have been sidestepped. We have evaluated ECP through different experiments using a network simulator that models different interconnection network configurations and realistic traffic patterns. This simulator also provides specific metrics for measuring the quality of the congestion detection mechanism. The obtained results show that ECP precisely identifies contesting packets with a low error margin, improving the DCQCN performance under congestion scenarios.