CoDel

CoDel - The Controlled-Delay Active Queue Management algorithm.

• Source Code
• Buffer Bloat

Explanations for the average person:

• this video (YT, 41 minutes) starting at ~21:00 explains CoDel
• it also explains Fair Queue CoDel
• but it does not explain HFSC

• measure the latency in the queue (from ingress to egress, via time stamping on entry and checking the timestamp on exit
• when latency exceeds tartget, think about dropping a packet
• after latency exceeds target, drop a packet at the HEAD of the queue (not the tail!)
• if that does not fix it, after a shorter interval (inverse sqrt), drop the net packet sooner, again at the HEAD
• keep decreasing the interval between drops until the latency in the queue drops below target
• we start with 100ms at the interval of the estimate and 5ms as the target (for 4Mbit/s and up); 10Gb/s needs a smaller target.
• below 4Mbit/s ... well, we don't know