P4BS: Leveraging Passive Measurements From P4 Switches to Dynamically Modify a Router's Buffer Size.

The performance of networked applications can be dramatically impacted by the size of the buffer at the bottleneck router. Shallow buffers may increase packet losses and decrease link utilization, while deep buffers may increase the queueing delays for latency-sensitive flows. Operators nowadays configure large buffers statically without considering the characteristics of flows or dynamic traffic patterns. This paper presents P4BS, a system that dynamically modifies the buffer size of a legacy router. P4BS leverages programmable switches as passive instruments to measure various metrics that are vital when deciding on buffer size. The measured metrics include the number of long-lived flows and their round-trip times, the packet loss rates, and the queueing delays. Using these measurements, the programmable switch sequentially searches for a buffer size that minimizes the queueing delays and the packet loss rates. The system was implemented on a Tofino hardware switch and the system was tested on a wide range of network scenarios. The results show improvements in the quality of service of various applications including web browsing, video streaming, and voice over IP.