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When “idle” isn't idle: how a Linux kernel optimization became a QUIC bug

100 points by sbulaev

by lproven

3 subcomments

The article uses the term "CCAs" without ever defining it. I followed the links, and googled it, with no useful result.
What is a CCA in this context?

by neuralkoi

1 subcomments

I can see why they rewrote QUIC in Rust and for use in userspace, though going the in-house approach would warrant keeping an eye on the relevant kernel commits like a hawk to avoid missing bug fixes like these. These in-house implementations tend to have less eyeballs than the kernel.
I found it interesting that Cloudflare is not yet using BBR as the default in quiche. CUBIC's recovery in this day and age, and especially in datacenters with large pipes, seems so slooow to me. Almost two seconds with no loss whatsoever till achieving BDP again and then shooting itself in the foot every time it hits the ceiling. Each one of those losses a retransmission.

by echoangle

0 subcomment

Looking at the last plot, it seems like the backoff is roughly 1/5 of the total bandwith and it happens every 50 ms or so. Wouldn't it make sense to reduce the backoff and the growth speed if a backoff occurs repeatedly in rapid succession? We want to maximize the area under the curve (transmitted packages), right?

by extropy

2 subcomments

by blahgeek

1 subcomments

The more precise title should be: How we copied code from Linux kernel without fully understand it and missed its follow-up fixes, now it bites us