No silver bullet: extending SDN to the data plane

The data plane is in a continuous state of flux. Every few months, researchers publish the design of a new high-performance queueing or scheduling scheme that runs inside the network fabric. Many such schemes have been queen for a day, only to be surpassed soon after as methods --- or evaluation metrics --- evolve. The lesson, in our view: there will never be a conclusive victor to govern queue management and scheduling inside network hardware. We provide quantitative evidence by demonstrating bidirectional cyclic preferences among three popular contemporary AQM and scheduling configurations. We argue that the way forward requires carefully extending Software-Defined Networking to control the fast-path scheduling and queueing behavior of a switch. To this end, we propose adding a small FPGA to switches. We have synthesized, placed, and routed hardware implementations of CoDel and RED. These schemes require only a few thousand FPGA "slices" to run at 10 Gbps or more --- a minuscule fraction of current low-end FPGAs --- demonstrating the feasibility and economy of our approach.