Preparation
- A CentOS 7 x64 server instance
- A sudo user
Step 1：Upgrade the Kernel using the ELRepo RPM repository
In order to use BBR, you need to upgrade the kernel of your CentOS 7 machine to 4.17.3. You can easily get that done using the ELRepo RPM repository.
Before the upgrade, you can take a look at the current kernel:
uname -r
This command should output a string which resembles:
3.10.0-862.3.2.el7.x86_64
As you see, the current kernel is 3.10.0.
Install the ELRepo repo:
sudo rpm --import https://www.elrepo.org/RPM-GPG-KEY-elrepo.org
sudo rpm -Uvh http://www.elrepo.org/elrepo-release-7.0-2.el7.elrepo.noarch.rpm
Install the 4.17.3 kernel using the ELRepo repo:
sudo yum --enablerepo=elrepo-kernel install kernel-ml -y
Confirm the result:
rpm -qa | grep kernel
If the installation is successful, you should see kernel-ml-4.17.3-1.el7.elrepo.x86_64 among the output list:
kernel-3.10.0-862.el7.x86_64
kernel-tools-3.10.0-862.3.2.el7.x86_64
kernel-ml-4.17.3-1.el7.elrepo.x86_64
kernel-tools-libs-3.10.0-862.3.2.el7.x86_64
kernel-3.10.0-862.3.2.el7.x86_64
Now, you need to enable the 4.17.3 kenel by setting up the default grub2 boot entry.
Show all entries in the grub2 menu:
sudo egrep ^menuentry /etc/grub2.cfg | cut -f 2 -d \'
The result should resemble:
CentOS Linux 7 Rescue 1b410a6be44a4bcd940575b49391319f (4.17.3-1.el7.elrepo.x86_64)
CentOS Linux (4.17.3-1.el7.elrepo.x86_64) 7 (Core)
CentOS Linux (3.10.0-862.3.2.el7.x86_64) 7 (Core)
CentOS Linux (3.10.0-862.el7.x86_64) 7 (Core)
CentOS Linux (0-rescue-4bbda2095d924b72b05507b68bd509f0) 7 (Core)
Since the line count starts at 0 and the 4.17.3 kernel entry is on the first line, set the default boot entry as 0:
sudo grub2-set-default 0
Reboot the system:
sudo shutdown -r now
When the server is back online, log back in and rerun the uname command to confirm that you are using the correct Kernel:
uname -r
You should see the result as below:
4.17.3-1.el7.elrepo.x86_64
Step 2: Enable BBR
In order to enable the BBR algorithm, you need to modify the sysctl configuration as follows:
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
Now, you can use the following commands to confirm that BBR is enabled:
sudo sysctl net.ipv4.tcp_available_congestion_control
The output should resemble:
net.ipv4.tcp_available_congestion_control = reno cubic bbr
Next, verify with:
sudo sysctl -n net.ipv4.tcp_congestion_control
The output should be:
bbr
Finally, check that the kernel module was loaded:
lsmod | grep bbr
The output will be similar to:
tcp_bbr 20480 1
Step 3(optionanl): Test the network performance enhancement
In order to test BBR's network performance enhancement, you can create a file in the web server directory for download, and then test the download speed from a web browser on your desktop machine.
sudo yum install httpd -y
sudo systemctl start httpd.service
sudo firewall-cmd --zone=public --permanent --add-service=http
sudo firewall-cmd --reload
cd /var/www/html
sudo dd if=/dev/zero of=500mb.zip bs=1024k count=500
Finally, visit the URL http://[your-server-IP]/500mb.zipfrom a web browser on your desktop computer, and then evaluate download speed.
