BBR(Bottleneck Bandwidth and RTT) is a new congestion control algorithm for TCP released by Google. It’s added into Linux kernel since 4.9. Instead of regarding packet loss as the signal of congestion, BBR sequentially probes the bottleneck bandwidth and RTT.
Check if the kernel supports BBR:
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uname -r # kernel >= 4.9
After that, use lsmod | grep bbr to test if the output has the word “bbr”. If not: