Collisions free scheduling in the NEPHELE hybrid electrical/optical datacenter interconnect

The NEPHELE datacenter network is divided into pods/clusters of racks and relies on hybrid electro-optical top-of rack switches that access an all-optical network consisting of WDM rings. To enable dynamic and efficient sharing of the optical resources and a collision-free network operation, the NEPHELE network is designed to operate in a slotted manner with a software-defined-network (SDN) based control plane. We describe the NEPHELE resource allocation problem, consider the wavelength conflicts on the shared WDM rings, translate them into resource allocation constraints and investigate the effect of these constraints on network performance. To do so, we define the worst-case traffic pattern and perform simulations to evaluate performance for the average traffic. Finally, we propose a variation to the NEPHELE architecture that reduces the effects of these wavelength conflict constraints on performance.