I. Introduction
Interconnect networks is an important component of large-scale systems as they affect overall scalability and performance. The topology of an interconnection network is a critical component of large-scale systems since it determines the performance bound including the network diameter [16]. Given the increasing pin bandwidth of routers [26], recent topologies for large-scale systems have exploited the availability of highradix routers to create high-radix topologies, including flattened butterfly [28], Dragonfly [27], HyperX [5], Slimfly [8], as well different variations, including Dragonfly [50] and Megafly [20]. These high-radix topologies have been adopted in various systems [1], [3] and recently announced Cray Slingshot [2] also adopts a Dragonfly topology with each group consisting of a fully-connected (or a 1D flattened butterfly) topology. One characteristics of high-radix topologies is the full connectivity within the topology – e.g., flattened butterfly or HyperX are fully connected within each dimension while Dragonfly have hierarchical “group” configuration that implements flattened butterfly topology. In this work, we exploit the full-connectivity in these high-radix topologies to provide routing deadlock avoidance without additional virtual channels.