Hi, I don't think that the AQM story is completed right now. There is a number of open issues that, I feel, are not well reflected by the currently discussed AQM proposals.
Some examples: - Bi-directional congestion (simultaneous up and download) produces a coarse oscillation between the involved queues. Any heuristics on "standing" or "steady" queue size should misinterpret that effect. Has it been investigated for the actual AQMs? - the "small RTT" issue (as Bob presented in Prague): At small RTT the AQM might want to lower the CWND to less than 2 packets, which TCP does not permit. As a result we get an uncontrolled queue growth despite AQM, ending up with drastic drop rates >20%, tail drop, retransmission timeouts, etc. This is a topic, not only, but also for AQM. - degradation of per flow queuing in less-than-BDP buffers: AQMs are targeting small queues, i.e. less than BDP. FQ is understood as the perfect complement to achieve fairness. But at small buffers at a given moment only a fraction of the involved flows have packets in their queue. Empty queues are not participating in the round robin scheduling. The respective flows are not earning credits as supposed for fairness reasons. Just to mention a few of the open issues. Wolfram
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