Hybrid optical/electrical switching in directly connected datacenter networks

The direct-connect topology, such as xD (x=3, 4, 5, 6, etc) torus, has been pervasive in High Performance Computing (HPC) platforms and is also appearing in datacenters. This paper discusses prospects and challenges of using the direct-connect topology in HPCs and datacenters, and proposes a new hybrid optical/electrical switching architecture to solve the major challenges such as high end-to-end latencies in multi-hop routing. We developed an OpenFlow-based software defined networking testbed to control both the electrical and optical switching components in such network architecture, and conducted experiments to verify the networking performance of the hybrid optical/electrical direct-connect network. The experimental results show that the hybrid architecture can indeed reduce the network diameter and therefore the end-to-end latency. Applications which require all-to-all communications, such as MapReduce, can greatly benefit from the reduced network diameter and end-to-end latency.