Easily Boost Ubuntu Network Performance by Enabling TCP BBR

This tutorial shows you how to enable TCP BBR on Ubuntu. TCP BBR is a TCP congestion control algorithm developed by Google. It tackles the shortcomings of traditional TCP congestion control algorithms (Reno or CUBIC). According to Google, it can achieve orders of magnitude higher bandwidth and lower latency. TCP BBR is already being used on Google.com and YouTube servers, and the Internet Engineering Task Force (IETF) has been standardizing this algorithm Since July, 2017. BBR stands for Bottleneck Bandwidth and RTT.

BBR requires only changes on the sender side. You can enable TCP BBR on your Linux desktop to improve the overall web surfing experience. If you have a Linux web server, TCP BBR can achieve faster web page downloads for your website visitors.

Step 1: Check TCP Congestion Control Algorithms on Linux

By default, Linux uses the Reno and CUBIC congestion control algorithm. To check available congestion control algorithms, run the following command.

sysctl net.ipv4.tcp_available_congestion_control

Output:

net.ipv4.tcp_available_congestion_control = cubic reno

To check the current congestion control algorithm in use, run

sysctl net.ipv4.tcp_congestion_control

Output:

net.ipv4.tcp_congestion_control = cubic

Step 2: Make Sure You Have Linux Kernel 4.9 or Above

TCP BBR is supported by Linux since kernel version 4.9. Use the following command to check your Linux kernel version.

uname -r

Ubuntu 18.04 has kernel 4.13.

4.13.0-16-generic

Ubuntu 20.04 uses kernel 5.4.

5.4.0-96-generic

Ubuntu 22.04 uses kernel 5.15.

5.15.0-25-generic

Step 3: Enable TCP BBR in Ubuntu

Once you have kernel 4.9 or above, edit sysctl.conf file.

sudo nano /etc/sysctl.conf

Add the following two lines at the end of the file.

net.core.default_qdisc=fq
net.ipv4.tcp_congestion_control=bbr

ubuntu tcp bbr

Save and close the file. Then reload sysctl configurations.

sudo sysctl -p

If you have correctly added the above two lines in the file, then they will be included in the output like below.

[email protected]:~$ sudo sysctl -p
net.core.default_qdisc = fq
net.ipv4.tcp_congestion_control = bbr

Now check the congestion control algorithm in use.

sysctl net.ipv4.tcp_congestion_control

Output:

net.ipv4.tcp_congestion_control = bbr

Congrats! You have successfully enabled TCP BBR on Ubuntu.

Speed Improvements

I used Shadowsocks proxy on a low-end VPS to test TCP BBR. The speed improvement is huge. The following screenshot shows YouTube connection speed before enabling TCP BBR on my proxy server. As you can see, the speed is only around 400Kb/s (50KB/s).

enable TCP BBR on Ubuntu 16.04

This is YouTube connection speed after enabling TCP BBR on my proxy server. 9878 Kb/s is about 1234 KB/s. My proxy server just got 24 times faster!

enable google tcp bbr ubuntu

On a second Shadowsocks proxy server, the speed went from around 10Mbit/s to around 62Mbit/s (64172Kbit/s) after enabling TCP BBR.

TCP BBR performance boost

Don’t disable TCP Window Scaling

You might need to disable TCP window scaling in order to fix a problem, but doing so can greatly reduce the network performance. Add the following line in /etc/sysctl.conf file to enable TCP window scaling.

net.ipv4.tcp_window_scaling = 1

Then apply the changes.

sudo sysctl -p

That’s it! I hope this tutorial helped you enable TCP BBR on Ubuntu. As always, if you found this post useful, then subscribe to our free newsletter to get more useful tips and tricks.

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13 Responses to “Easily Boost Ubuntu Network Performance by Enabling TCP BBR

  • MrAdminus
    4 years ago

    You should write a little notice on Linuxtoday so more people get to know about your blog. I think what you’re doing is great and contributes to the Linux community. It’s free to write a post there too and many Linux users reads it!
    https://www.linuxtoday.com/

  • Greya Being
    4 years ago

    How do I undo this?

  • Sayyed Alireza
    4 years ago

    Best Blog website ever

    thanks for being born :*

  • Michael
    3 years ago

    Thank you for this little gem! So easy to do too 🙂

  • Hi
    I have tried to enable it but my output is different from yours. Below is the output from my system

    [email protected]:~$ sysctl net.ipv4.tcp_available_congestion_control
    net.ipv4.tcp_available_congestion_control = reno cubic
    [email protected]:~$ sysctl net.ipv4.tcp_congestion_control
    net.ipv4.tcp_congestion_control = cubic
    [email protected]:~$ sudo nano /etc/sysctl.conf
    [sudo] password for jieru:
    [email protected]:~$ sudo sysctl -p
    [email protected]:~$ sysctl net.ipv4.tcp_congestion_control
    net.ipv4.tcp_congestion_control = cubic

    • Xiao Guoan (Admin)
      1 year ago

      /etc/sysctl.conf
      ubuntu-tcp-bbr

      If you have correctly added the above two lines in the file, then they will be included in the output like below when you run sudo sysctl -p.

      [email protected]:~$ sudo sysctl -p
      net.core.default_qdisc = fq
      net.ipv4.tcp_congestion_control = bbr
      
      • Hi
        Here is the updated outputs

        [email protected]:~$ sudo cat /boot/config-$(uname -r) | grep 'CONFIG_TCP_CONG_BBR'
        [sudo] password for jieru:           
        CONFIG_TCP_CONG_BBR=m
        [email protected]:~$ sudo cat /boot/config-$(uname -r) | grep 'CONFIG_NET_SCH_FQ'
        CONFIG_NET_SCH_FQ_CODEL=m
        CONFIG_NET_SCH_FQ=m
        [email protected]:~$ sudo nano /etc/sysctl.conf
        [email protected]:~$ sudo sysctl --system
        * Applying /etc/sysctl.d/10-console-messages.conf ...
        kernel.printk = 4 4 1 7
        * 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-magic-sysrq.conf ...
        kernel.sysrq = 176
        * Applying /etc/sysctl.d/10-network-security.conf ...
        net.ipv4.conf.default.rp_filter = 2
        net.ipv4.conf.all.rp_filter = 2
        * 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 /usr/lib/sysctl.d/50-coredump.conf ...
        kernel.core_pattern = |/lib/systemd/systemd-coredump %P %u %g %s %t 9223372036854775808 %h
        * Applying /usr/lib/sysctl.d/50-default.conf ...
        net.ipv4.conf.default.promote_secondaries = 1
        sysctl: setting key "net.ipv4.conf.all.promote_secondaries": Invalid argument
        net.ipv4.ping_group_range = 0 2147483647
        net.core.default_qdisc = fq_codel
        fs.protected_regular = 1
        fs.protected_fifos = 1
        * Applying /usr/lib/sysctl.d/50-mint.conf ...
        fs.inotify.max_user_watches = 65536
        * Applying /usr/lib/sysctl.d/50-pid-max.conf ...
        kernel.pid_max = 4194304
        * Applying /etc/sysctl.d/99-sysctl.conf ...
        net.core.default_qdisc = fq
        net.ipv4.tcp_congestion_control = bbr
        * Applying /usr/lib/sysctl.d/protect-links.conf ...
        fs.protected_fifos = 1
        fs.protected_hardlinks = 1
        fs.protected_regular = 2
        fs.protected_symlinks = 1
        * Applying /etc/sysctl.conf ...
        net.core.default_qdisc = fq
        net.ipv4.tcp_congestion_control = bbr
        [email protected]:~$ sysctl net.ipv4.tcp_congestion_control
        net.ipv4.tcp_congestion_control = bbr
        [email protected]:~$ 
        

        Is everything correct?

        Thanks

    • Xiao Guoan (Admin)
      1 year ago

      Yes. it’s correct.

  • i did not understand what net.ipv4.tcp_window_scaling = 1 means

    • Xiao Guoan (Admin)
      11 months ago

      If you don’t understand this, then ignore it. It’s on by default. Learn the TCP/IP protocol and you will understand TCP window scaling.

  • Bruno Cabral
    4 months ago

    Is it necessary to install hwe kernel? Because Ubuntu 18.04 already has kernel > 4.9 (4.15, as today). HWE kernel would be 5.4

    • Xiao Guoan (Admin)
      4 months ago

      If you have Linux kernel 4.9 or above, then you don’t need to install a new kernel.

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