Why not use WFQ for Predictive Service?
Goal: minimize actual measured delay bounds
A burst by one source causes a sharp increase in delay (jitter) seen by that source
In FIFO, bursts are multiplexed, thus a burst affects other sources but sees less delay (burst sharing => less jitter)
Average delay is same (cf. conservation law), but 99.9 percentile delays are much smaller under FIFO
Isolate different classes using WFQ, and use FIFO to benefit from sharing within each class
FIFO+ reduces the accumulation of jitter over multiple hops by serving packets in order of expected arrival times under average service