> Delay-based ARED behaves similar to tail drop at max threshold. >> > I think I now understand what you mean by this sentence ;-) and therefore please ignore the paragraph responding to this specific point in the previous email (sorry about that, I got it mixed with max_target). Indeed ARED drops every packet when the average queue length grows beyond th_max as drop probability jumps to 1 (when it's not in gentle mode). For this to happen, the "average queue length" has to grow beyond th_max and depending on how the averaging is done, that can correspond to certain burst allowance at AQM. Moreover, this is done over 500 ms interval which means the average queue length has to stay above th_max for mostly few rounds of RTTs (assuming the typical distribution of RTTs on the Internet to have a mean/average somewhere below that value e.g. 100~200 ms). This allows burst that don't take the average queue size to above th_max over 500 ms period to pass and clear themselves up the queue.
> This is unacceptable of an AQM even for max thresholds around 50ms. Whether this is a good thing or bad thing is a subjective matter in my opinion, as most AQMs at some point will drop every packet whether it be the maximum queue length or at some thresholds. Cheers, Naeem
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