Enable TCP BBR on AlmaLinux 8 | Boost Network Efficiency

In this guide from Orcacore, we aim 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. The goal of enabling BBR is to improve network performance.

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 networks have changed significantly.

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. Therefore, learning how to enable TCP BBR on AlmaLinux 8 is essential.

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 on the Initial Server Setup with AlmaLinux 8.

Now follow the steps below to complete this guide.

How To Enable TCP 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

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

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

Add 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. The steps above have shown you how to enable TCP BBR on AlmaLinux 8.

Conclusion

At this point, you learn to enable TCP BBR on AlmaLinux 8. Enabling BBR improves network performance by optimizing bandwidth and reducing latency, especially on high-speed or long-distance connections.

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FAQs

Is TCP BBR safe and stable to use in production?

Yes, TCP BBR is considered stable and has been adopted in production environments by major tech companies.

Will enabling BBR affect existing connections or services?

No, enabling BBR applies to new TCP connections. Existing connections will continue using the previously assigned congestion control algorithm.

Alternative Solutions for Enabling TCP BBR on AlmaLinux 8

While the method described above is a standard way to enable TCP BBR on AlmaLinux 8, there are alternative approaches that can achieve the same result. These methods provide flexibility and cater to different system configurations or preferences. Here are two different ways to enable BBR:

1. Using `tuned` profiles

tuned is a system tuning daemon that dynamically adjusts system settings based on predefined profiles. We can create a custom tuned profile to enable BBR, making the configuration persistent and manageable through tuned. This is another way to enable TCP BBR on AlmaLinux 8.

Explanation:

tuned profiles allow you to group system settings and apply them based on the detected system environment.
Creating a custom profile specifically for BBR allows you to easily enable or disable it, and it integrates seamlessly with other tuned profiles.
This method ensures that the BBR settings are applied at boot and are consistently managed.

Steps:

Create a custom tuned profile:

Create a new directory for the profile:
```
sudo mkdir /etc/tuned/bbr
```
Create a tuned.conf file within the new directory:
```
sudo nano /etc/tuned/bbr/tuned.conf
```
Add the following content to the tuned.conf file:
```
[main]
include = network-throughput

[sysctl]
net.core.default_qdisc = fq
net.ipv4.tcp_congestion_control = bbr
```
Explanation:
- [main] section: include = network-throughput inherits settings from the network-throughput profile, providing a base configuration.
- [sysctl] section: Sets the required sysctl parameters to enable BBR.
Enable the BBR tuned profile:
```
sudo tuned-adm profile bbr
```

Verify the settings:

sudo sysctl net.ipv4.tcp_congestion_control
sudo sysctl net.core.default_qdisc

Reboot the system to ensure changes persist:
```
sudo reboot
```

After rebooting, verify that BBR is enabled using the sysctl and lsmod commands as outlined in the original article.

2. Using `systemd-tmpfiles`

systemd-tmpfiles manages temporary files and directories and can also be used to set sysctl parameters at boot. This method involves creating a configuration file that sets the BBR-related sysctl values during system startup.

Explanation:

systemd-tmpfiles provides a way to set system settings at boot time using configuration files.
This is a lightweight method that doesn’t require an additional daemon like tuned.
The configuration file is processed at boot, ensuring that the BBR settings are applied.

Steps:

Create a configuration file:

Create a new configuration file in the /etc/tmpfiles.d/ directory:
```
sudo nano /etc/tmpfiles.d/bbr.conf
```
Add the following content to the bbr.conf file:
```
w /proc/sys/net/core/default_qdisc - - - - fq
w /proc/sys/net/ipv4/tcp_congestion_control - - - - bbr
```
Explanation:
- w specifies that the entry should write to the given path.
- /proc/sys/net/core/default_qdisc and /proc/sys/net/ipv4/tcp_congestion_control are the paths to the sysctl parameters.
- fq and bbr are the values to be written.

Reload the systemd-tmpfiles configuration:

sudo systemd-tmpfiles --create /etc/tmpfiles.d/bbr.conf

Reboot the system:
```
sudo reboot
```

After rebooting, verify that BBR is enabled using the sysctl and lsmod commands as outlined in the original article.

Considerations:

Both alternative methods provide persistent solutions for enabling BBR.
The tuned method is more comprehensive and integrates with other system tuning profiles.
The systemd-tmpfiles method is simpler and doesn’t require an additional daemon.
Choose the method that best suits your system configuration and management preferences.

These alternative solutions offer different ways to achieve the same goal of enabling TCP BBR on AlmaLinux 8. Understanding these options allows you to choose the most appropriate method for your specific needs and environment. Regardless of the method chosen, enabling BBR can significantly improve network performance on your AlmaLinux 8 server.