CoDel Controlled Delay
Active queue management algorithm (Kathie Nichols + Van Jacobson, 2012) — drops packets when the queue's dwell time exceeds the target (5ms default).
Parameter-free (unlike RED which required manual tuning). Linux qdisc since 3.5 (2012). FQ-CoDel = fair queueing + CoDel combined, default qdisc in Linux + OpenWrt since ~2015. Powers all modern anti-bufferbloat implementations.