Networking also: Bottleneck Bandwidth and RTT

BBR

Congestion control that models the path instead of reacting to loss.

In plain terms

Cardwell et al at Google, 2017. Replaces CUBIC's "halve cwnd on loss" with active probing of bandwidth and RTT. Default in Linux 4.9+ and Google's edge.

Origin

Neal Cardwell, Yuchung Cheng, C. Stephen Gunn, Soheil Hassas Yeganeh, Van Jacobson at Google, 2016. Default in Linux 4.9+ and YouTube's edge.

Where it shows up in production

YouTube + Google.com BBR has been the default congestion controller at Google's edge since 2017. Cuts P99 latency by ~30%.
AWS Enabled per-instance on EC2 since 2020; default on Graviton instances.

On Semicolony

Paper papers

Sources & further reading

Paper Cardwell et al. — BBR paper (ACM Queue, 2016)
Talk Google — BBR talk (NSDI 2017)

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