Keeping up to Date with P4Runtime: An Analysis of Data Plane Updates on P4 Switches

The continuous increase of achievable data rates in computer networks is both blessing and curse. Increasing data rates enable novel applications through higher bandwidths. However, support for higher data rates requires devices to process packets reliably in an ever-decreasing amount of time per packet. In terms of software-defined networking: higher data rates call for a faster data plane. Nevertheless, the control plane must not be ignored; to faithfully react to data plane behavior, a high-performance control plane is essential. Otherwise, e.g., the data plane's state cannot be updated fast enough to cope with fast-paced traffic changes. In this case study, we investigate the control plane of a high-performance P4 switching ASIC. Moreover, we create a measurement methodology to track the delay between the reception of a rule update on the control plane and its actual application on the data plane of a P4 hardware switch. By applying the methodology to said ASIC, we can precisely describe its performance and non-atomicity in updates. Based on our findings, we apply multiple different approaches to optimize control plane latency. Our results highlight the need to consider latency on the control plane proportionate with the increase of achievable data rates.