I recently read that TCP BBR has significantly increased throughput and reduced latency for connections on Google’s internal backbone networks and google.com and YouTube Web servers throughput by 4 percent on average globally – and by more than 14 percent in some countries. The TCP BBR patch needs to be applied to the Linux kernel. The first public release of BBR was here, in September 2016. The patch is available to any one to download and install. Another option is using Google Cloud Platform (GCP). GCP by default turned on to use a cutting-edge new congestion control algorithm named TCP BBR.
Requirements
Make sure that your Linux kernel has the following option compiled as either module or inbuilt into the Linux kerne:
- CONFIG_TCP_CONG_BBR
- CONFIG_NET_SCH_FQ
You must use the Linux kernel version 4.9 or above. On a Debian/Ubuntu Linux type the following grep command/egrep command:
$ grep 'CONFIG_TCP_CONG_BBR' /boot/config-$(uname -r)
$ grep 'CONFIG_NET_SCH_FQ' /boot/config-$(uname -r)
$ egrep 'CONFIG_TCP_CONG_BBR|CONFIG_NET_SCH_FQ' /boot/config-$(uname -r)
Sample outputs:
I am using Linux kernel version 4.10.0-28. If above options not found, you need to either compile latest kernel or install the latest version of Linux kernel using the apt-get command/apt command.
How to enable TCP BBR congestion control on Linux
Edit the /etc/sysctl.conf file or create a new file in /etc/sysctl.d/ directory:
$ sudo vi /etc/sysctl.conf
OR
$ sudo vi /etc/sysctl.d/10-custom-kernel-bbr.conf
Append the following two lines:
net.core.default_qdisc=fq
net.ipv4.tcp_congestion_control=bbr
Save and close the file i.e. exit from the vim/vi text editor by typing :x!. Next you must either reboot the Linux box or reload the changes using the sysctl command:
$ sudo reboot
OR
$ sudo sysctl --system
Sample outputs:
* Applying /etc/sysctl.d/10-console-messages.conf ... kernel.printk = 4 4 1 7 * Applying /etc/sysctl.d/10-custom.conf ... net.core.default_qdisc = fq net.ipv4.tcp_congestion_control = bbr * Applying /etc/sysctl.d/10-ipv6-privacy.conf ... net.ipv6.conf.all.use_tempaddr = 2 net.ipv6.conf.default.use_tempaddr = 2 * Applying /etc/sysctl.d/10-kernel-hardening.conf ... kernel.kptr_restrict = 1 * Applying /etc/sysctl.d/10-link-restrictions.conf ... fs.protected_hardlinks = 1 fs.protected_symlinks = 1 * Applying /etc/sysctl.d/10-lxd-inotify.conf ... fs.inotify.max_user_instances = 1024 * Applying /etc/sysctl.d/10-magic-sysrq.conf ... kernel.sysrq = 176 * Applying /etc/sysctl.d/10-network-security.conf ... net.ipv4.conf.default.rp_filter = 1 net.ipv4.conf.all.rp_filter = 1 net.ipv4.tcp_syncookies = 1 * Applying /etc/sysctl.d/10-ptrace.conf ... kernel.yama.ptrace_scope = 1 * Applying /etc/sysctl.d/10-zeropage.conf ... vm.mmap_min_addr = 65536 * Applying /etc/sysctl.d/99-sysctl.conf ... * Applying /etc/sysctl.conf ...
You can verify new settings with the following sysctl command. Run:
$ sysctl net.core.default_qdisc
net.core.default_qdisc = fq
$ sysctl net.ipv4.tcp_congestion_control
net.ipv4.tcp_congestion_control = bbr
Test it
In my testing between two long distance Linux server with Gigabit ports connected to the Internet, I was able to bump 250 Mbit/s into 800 Mbit/s. You can use tools such as the wget command to measure bandwidths speed:
$ wget https://your-server-ip/file.iso
I also noticed I was able to push almost 100 Mbit/s for my OpenVPN traffic. Previously I was able to push up to 30-40 Mbit/s only. Overall I am quite satisfied with TCP BBR congestion control option for my Linux box.
References
Posted by: Vivek Gite
The author is the creator of nixCraft and a seasoned sysadmin and a trainer for the Linux operating system/Unix shell scripting. He has worked with global clients and in various industries, including IT, education, defense and space research, and the nonprofit sector. Follow him on Twitter, Facebook, Google+.
