How to enable native Google BBR on CentOS 7 / Debian 9 to achieve TCP acceleration

New kernels such as CentOS 7/Debian 9 come with BBR, which can be enabled directly and is safe.

1. CentOS 7 enables native Google BBR

1. Update the CentOS 7 kernel to support BBR

1. Check the Centos kernel

 uname -r

2. If it is lower than 4.10, update the kernel

 rpm --import https://www.elrepo.org/RPM-GPG-KEY-elrepo.org
rpm -Uvh http://www.elrepo.org/elrepo-release-7.0-2.el7.elrepo.noarch.rpm
yum --enablerepo=elrepo-kernel install kernel-ml -y

3. After the installation is complete, check the installed kernel:

 rpm -qa | grep kernel

If you see kernel-ml-5.3.5-1.el7.elrepo.x86_64, it is successful.
4. Update startup

 egrep ^menuentry /etc/grub2.cfg | cut -f 2 -d \'

You will see something like this

 CentOS Linux (5.3.5-1.el7.elrepo.x86_64) 7 (Core)
CentOS Linux (3.10.0-957.1.3.el7.x86_64) 7 (Core)
CentOS Linux (0-rescue-96820b9851c24560b5f942f2496b9aeb) 7 (Core)

Set CentOS Linux (5.3.5-1.el7.elrepo.x86_64) 7 (Core) as the first boot order (because the boot starts from 0)

 grub2-set-default 0

5. Restart the system

 reboot

(II) Enabling BBR in CentOS 7

1. Execution

 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
sysctl -p

2. Check whether BBR is enabled in the kernel

 sysctl net.ipv4.tcp_available_congestion_control

and

 lsmod | grep bbr

If the word BBR is displayed, it means that BBR is enabled successfully.

2. Debian 9 enables native Google BBR

1. Modify system variables

 echo "net.core.default_qdisc=fq" >> /etc/sysctl.conf echo "net.ipv4.tcp_congestion_control=bbr" >> /etc/sysctl.conf

2. Save and take effect

 sysctl -p

3. Check whether BBR is enabled in the kernel

 sysctl net.ipv4.tcp_available_congestion_control

The following content is displayed to indicate that it is enabled:

 sysctl net.ipv4.tcp_available_congestion_control net.ipv4.tcp_available_congestion_control = bbr cubic reno

4. BBR should have been started through the above operations. Then check whether BBR is started.

 lsmod | grep bbr

The following is displayed, indicating successful startup:

 lsmod | grep bbr tcp_bbr 20480 14