Fundamental Challenges for Hybrid Electrical/Optical Datacenter Networks

Recent research proposals on building hybrid electrical/optical networks as a way of interconnecting the core layer of a modular datacenter promise reduction in the cost, deployment complexity as well as energy requirement of large scale datacenter networks. We summarize our two years of experience in dealing with such hybrid interconnects. We first show the feasibility of building hybrid networks under homogeneous environments where one application dominates the workload through building a completely functional prototype of Helios/c-Through systems. Then we uncover a number of fundamental challenges and problems, some quite unexpected, which must be addressed for wide adoption of these proposals in industry settings under heterogeneous traffic pattern with multi-tenancy. We then propose a significantly more flexible, fine-grained and responsive way of controlling such hybrid networks under Observe-Analyze-Act framework which is based on OpenFlow. Although the complete picture of how to build these networks in particular the best circuit scheduling algorithm to use is still unclear, but we show that this framework enables a variety of future solutions to the remaining challenges.