Efficient Topologies for Large-Scale Cluster Networks
Venue
2010 Conference on OFC/NFOEC, IEEE, pp. 1-3
Publication Year
2010
Authors
John Kim, William J. Dally, Dennis Abts
BibTeX
Abstract
Increasing integrated-circuit pin bandwidth has motivated a corresponding increase
in the degree or radix of interconnection networks and their routers. This paper
describes the flattened butterfly, a cost-efficient topology for high-radix
networks. On benign (load-balanced) traffic, the flattened butterfly approaches the
cost/performance of a butterfly network and has roughly half the cost of a
comparable performance Clos network. The advantage over the Clos is achieved by
eliminating redundant hops when they are not needed for load balance. On
adversarial traffic, the flattened butterfly matches the cost/performance of a
folded-Clos network and provides an order of magnitude better performance than a
conventional butterfly. In this case, global adaptive routing is used to switch the
flattened butterfly from minimal to non-minimal routing — using redundant hops only
when they are needed. Different routing algorithms are evaluated on the flattened
butterfly and compared against alternative topologies. We also provide a detailed
cost model for an interconnection network and compare the cost of the flattened
butterfly to alternative topologies to show the cost advantages of the flattened
butterfly.
