[Bloat] fq_codel, high bandwidth, and delays

[Aaron Wood <woody77@gmail.com>]

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List,

In talking with a friend over the weekend that moves data around for the
national labs (on links at rates like 10Gbps), we ended up having a rather
interesting discussion about just how radically different the problem
spaces are vs. what he's seen in the bufferbloat community.

They have few flows, long lived, and are trying to push >1Gbps per flow,
across the continent (or from Europe to the US), with inherent delays on
the order of 100ms.  TCP under these conditions is, from his reports,
incredibly fragile, where even a tiny packet error rate stops TCP for
saturating the link (since it can't tell the difference between congestion
and a non-congestion-related dropped packet).

And suddenly the "every packet is precious" mode of thought becomes crystal
clear.

Clearly they are trying to solve different problems, yet they do have
congestion events, when new flows are added to the network.

Has anyone used fq_codel (or it's friends) in scenarios like this?  fq is
fairly new (2 years?) and I can't find much about it and high bandwidth
links in my searches.

Given that their problems aren't those that fq is trying to solve, I
wouldn't expect it, but curious to see if anyone has any research on it.

Thanks,
Aaron

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