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 time-varying 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.