Physical-layer adaptive resource allocation in software-defined data center networks

With the deep physical-layer programmability enabled by software-defined networking (SDN), it is now feasible to realize optical data center transceivers that adapt their transmission parameters in response to timevarying traffic demand and signal quality conditions. In this paper, we develop a cross-layer performance tuning framework for wavelength-tunable data center transceivers, combining scalable and secure modulation order and code rate adaptation. We develop new physical-layer control modules and combine SDN control with distributed preamble encoding in order to achieve both rate adaptation and node synchronization in a wavelength-routing data center testbed. Our experimental and theoretical studies based on pulse amplitude modulation and low-density parity-check coding point to the significance of joint modulation order and code-rate adaptation in data centers. We report real-time resource adaptation with switching speeds on the order of hundreds of milliseconds.