By default, Linux uses the Reno and CUBIC congestion control algorithm. To check available congestion control algorithms, run the following command.

sysctl net.ipv4.tcp_available_congestion_control

Output:

net.ipv4.tcp_available_congestion_control = cubic reno

To check the current congestion control algorithm in use, run

sysctl net.ipv4.tcp_congestion_control

Output:

net.ipv4.tcp_congestion_control = cubic

TCP BBR is supported by Linux since kernel version 4.9. Use the following command to check your Linux kernel version.

uname -r

Ubuntu 18.04 has kernel 4.13.

4.13.0-16-generic

Enable TCP BBR in Ubuntu

Once you have kernel 4.9 or above, edit sysctl.conf file.

sudo nano /etc/sysctl.conf

Add the following two line at the end of the file.

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

Save and close the file. Then reload sysctl configurations.

sudo sysctl -p

Now check the congestion control algorithm in use.

sysctl net.ipv4.tcp_congestion_control

Output:

net.ipv4.tcp_congestion_control = bbr

Congrats! You have successfully enabled TCP BBR on Ubuntu.

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