How To Enable TCP BBR on AlmaLinux 8

In this guide, we intend to teach you How To Enable TCP BBR on AlmaLinux 8.

Bottleneck Bandwidth and Round-trip propagation time (BBR) is a TCP congestion control algorithm developed at Google in 2016.

Up until recently, the Internet has primarily used loss-based congestion control, relying only on indications of lost packets as the signal to slow down the sending rate. This worked decently well, but the networks have changed.

We have much more bandwidth than ever before; The Internet is generally more reliable now, and we see new things such as bufferbloat that impact latency. BBR tackles this with a ground-up rewrite of congestion control, and it uses latency, instead of lost packets as a primary factor to determine the sending rate.

Enable BBR Congestion Control Algorithm on AlmaLinux 8

To enable TCP BBR, you must log in to your server as a non-root user with sudo privileges. To do this, you can follow our guide the Initial Server Setup with AlmaLinux 8.

Now follow the steps below to complete this guide.

Enabling BBR on AlmaLinux 8

First, you need to update and upgrade your local package index with the following command:

sudo dnf update && sudo dnf upgrade -y

Then, you need to check your existing congestion controls on your server.

Check Existing Congestion Control Algorithms on AlmaLinux

Typically, Linux uses reno and cubic algorithms.

At this point, you need to run the following command to check what existing TCP congestion controls are in place:

sudo sysctl net.ipv4.tcp_congestion_control

Output
net.ipv4.tcp_congestion_control = cubic

In the above output, cubic is employed in our system, but your output may show different results.

Next, list available TCP congestion control algorithms on your server by using the following command:

sudo sysctl net.ipv4.tcp_available_congestion_control

Output
net.ipv4.tcp_available_congestion_control = reno cubic

From the output, reno and cubic are available, and once BBR has been added/enabled, this should feature BBR.

Add TCP BBR on AlmaLinux 8

Now that you have checked the basics to confirm the available algorithms, you need to open the sysctl.conf file. Here we use the vi editor to open the file:

sudo vi /etc/sysctl.conf

Add the following content to the file:

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

When you are done, save and close the file.

Then, reload the configuration file with the command below:

sudo sysctl -p

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

At this point, you need to verify that  BBR is enabled and active as the new TCP congestion control by using the following command on AlmaLinux 8:

sudo sysctl net.ipv4.tcp_congestion_control

Output
net.ipv4.tcp_congestion_control = bbr

Also, you can use the command below to verify it:

lsmod | grep bbr

Output
tcp_bbr                20480  1

Finally, list available TCP congestion controls on your server again:

sudo sysctl net.ipv4.tcp_available_congestion_control

You should see BBR in your list:

Output
net.ipv4.tcp_available_congestion_control = reno cubic bbr

That’s it. You have successfully added BBR to your server.

Conclusion

At this point, you learn to Enable BBR on AlmaLinux 8.

Hope you enjoy it.

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