  In this paper we present PolarFly, a diameter-2 network topology based on the
Erdos-Renyi family of polarity graphs from finite geometry. This is a highly
scalable low-diameter topology that asymptotically reaches the Moore bound on
the number of nodes for a given network degree and diameter
  PolarFly achieves high Moore bound efficiency even for the moderate radixes
commonly seen in current and near-future routers, reaching more than 96% of the
theoretical peak. It also offers more feasible router degrees than the
state-of-the-art solutions, greatly adding to the selection of scalable
diameter-2 networks. PolarFly enjoys many other topological properties highly
relevant in practice, such as a modular design and expandability that allow
incremental growth in network size without rewiring the whole network. Our
evaluation shows that PolarFly outperforms competitive networks in terms of
scalability, cost and performance for various traffic patterns.
