PIE Proportional Integral controller Enhanced
AQM algorithm from Cisco — RFC 8033. Selected as AQM for the DOCSIS 3.1 cable-modem standard, so present in nearly every cable modem from 2016+.
Control theory approach: PI controller for drop probability based on queue delay. Default target 15ms. Easier to implement in hardware than CoDel (less state). Competitor: CoDel (winner in Linux/OpenWrt world), RED (the old classic).