Notes on TCP BBR

2026-06-30

BBR is a congestion control algorithm that models bandwidth and RTT instead of reacting to packet loss. On links with some loss it can be much faster than CUBIC.

net.core.default_qdisc = fq
net.ipv4.tcp_congestion_control = bbr

Put those in /etc/sysctl.d/, run sysctl --system, and check with sysctl net.ipv4.tcp_congestion_control.

On a long-distance link my downloads went from noticeably bursty to steady. On a local link I saw no difference, which is what you'd expect.

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