LIA: latency-improved adaptive routing for dragonfly networks

Abstract

Low-diameter network topologies require non-minimal routing, such as Valiant routing, to avoid network congestion under challenging traffic patterns like the so-called adversarial. However, this mechanism tends to increase the average path length, base latency, and network load. The use of shorter non-minimal paths has the potential to enhance performance, but it may also introduce congestion depending on the traffic patterns. This article introduces LIA (Latency-Improved Adaptive), a routing mechanism for Dragonfly networks which dynamically exploits minimal and non-minimal paths. LIA harnesses the traffic counters already present in contemporary switches to determine when it is safe to shorten non-minimal paths and to adjust routing decisions based on their information about the network conditions. Evaluations reveal that LIA achieves nearly optimal latency, outperforming state-of-the-art adaptive routing mechanisms by reducing latency by up to 30% while maintaining stable throughput and fairness.