Technology-Driven, Highly-Scalable Dragonfly Topology

Evolving technology and increasing pin-bandwidth motivate the use of high-radix routers to reduce the diameter, latency, and cost of interconnection networks. High-radix networks, however, require longer cables than their low-radix counterparts. Because cables dominate network cost, the number of cables, and particularly the number of long, global cables should be minimized to realize an efficient network. In this paper, we introduce the dragonfly topology which uses a group of high-radix routers as a virtual router to increase the effective radix of the network. With this organization, each minimally routed packet traverses at most one global channel. By reducing global channels, a dragonfly reduces cost by 20% compared to a flattened butterfly and by 52% compared to a folded Clos network in configurations with 16K nodes. We also introduce two new variants of global adaptive routing that enable load-balanced routing in the dragonfly. Each router in a dragonfly must make an adaptive ...

• Type: Journal
• Year: 2008
• Where: ISCA
• Authors: John Kim, William J. Dally, Steve Scott, Dennis Abts
• Keywords: Adaptive Routing, Global Channel, Hardware, ISCA 2008, Router