Pie's principal advantage is that it is slightly easier to implement in hardware, it's disadvantages are that it does tail drop, rather than head drop, and struggles to be stable at a target of 16ms, where codel can go down to us and targets 5ms by default. I haven't really revisited pie since the above paper was published.
COBALT in cake is a codel derivative. It is slightly tighter in some respects (hitting slow start sooner), and looser in others (it never drops the last packet in a queue, which fq_codel does.fq_codel scales to hundreds of instances and 10s of thousands of queues, still aiming for 5ms across that target, where it would be easier to essentially DOS that many instances of cake with tons of flows.
Pie had a severe problem in the rate estimator which was fixed in 2018, in Linux, at least:
https://www.sciencedirect.com/science/article/abs/pii/S13891...
Pie's principal advantage is that it is slightly easier to implement in hardware, it's disadvantages are that it does tail drop, rather than head drop, and struggles to be stable at a target of 16ms, where codel can go down to us and targets 5ms by default. I haven't really revisited pie since the above paper was published.
COBALT in cake is a codel derivative. It is slightly tighter in some respects (hitting slow start sooner), and looser in others (it never drops the last packet in a queue, which fq_codel does.fq_codel scales to hundreds of instances and 10s of thousands of queues, still aiming for 5ms across that target, where it would be easier to essentially DOS that many instances of cake with tons of flows.