TCP BBR (Bottleneck Bandwidth and Round-trip propagation time) is a modern TCP congestion control mechanism developed by Google. By measuring RTT (Round-Trip Time), TCP BBR ensures higher and more stable network bandwidth, while also reducing packet latency. It adapts to changing network conditions and remains aggressive in transferring data, even during short-term network issues.
Activating BBR on CentOS 7
BBR can be enabled on most Linux-based operating systems, and in this guide, we'll show you how to activate it on CentOS 7.
Requirements
To enable BBR, your server's kernel version must be at least 4.9. Unfortunately, buycheapvps Container VPS servers with kernel 3.10.0 and Storage VPS servers with kernel 2.6.32 won't support BBR. You’ll need a Linux VPS server with a compatible kernel.
Check your kernel version with this command:
uname -r
If your kernel version is too low, consider upgrading it.
Enabling BBR
To activate BBR, you'll need to update the sysctl settings by adding specific parameters to the sysctl.conf file. These parameters include FQ (Fair Queueing) and BBR.
Using the vi editor, add the following values:
vi /etc/sysctl.conf
Add these lines:
net.core.default_qdisc=fq
net.ipv4.tcp_congestion_control=bbr
Then, apply the changes:
sysctl --system
Alternatively, you can use the echo command:
echo 'net.core.default_qdisc=fq' | sudo tee -a /etc/sysctl.conf
echo 'net.ipv4.tcp_congestion_control=bbr' | sudo tee -a /etc/sysctl.conf
sudo sysctl -p
Verifying BBR Activation
Check if BBR is enabled with this command:
sudo sysctl net.ipv4.tcp_available_congestion_control
You should see an output like:
net.ipv4.tcp_available_congestion_control = bbr cubic reno
You can also confirm with:
sudo sysctl -n net.ipv4.tcp_congestion_control
The output should include:
bbr
Testing BBR
To see the impact of BBR, run tests like iperf3 or wget to compare network speeds before and after enabling BBR.
Before:
After:
Before
After:
Keep in mind, while BBR can significantly improve performance, the results may vary based on various factors. BBR is especially effective in multi-hop networks, like those connecting servers across continents.
For more details on BBR, refer to Google’s documentation on the congestion control algorithm.
