Specify the BBR Congestion Control Algorithm for each connection

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Dhvit Mehta

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Dec 11, 2021, 1:14:20 PM12/11/21
to BBR Development

I want to know if I can allow only a few TCP connections to use BBR, I want to run Cubic or any other algorithm for the other connections

As far as I know once BBR is enabled using the systctl method it will be used for all TCP connections on the sender side

Ayush Mishra

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Dec 11, 2021, 1:25:27 PM12/11/21
to Dhvit Mehta, BBR Development
Hey Dhvit,

You can select which congestion control algorithm you want to use for a connection using the socket options. If you're planning to run experiments using iperf, for example, you can set the congestion control algorithm of an iperf flow using the -Z option for iperf, and -C for iperf3. Sysctl sets the default congestion control algorithm - it will be overridden by whatever you set with iperf.

Example:
iperf3 -s -p 1000 -C bbr
iperf -s -p 1000 -Z bbr

~Ayush

On Sun, Dec 12, 2021 at 2:14 AM Dhvit Mehta <icm20...@iiita.ac.in> wrote:

I want to know if I can allow only a few TCP connections to use BBR, I want to run Cubic or any other algorithm for the other connections

As far as I know once BBR is enabled using the systctl method it will be used for all TCP connections on the sender side

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Neal Cardwell

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Dec 11, 2021, 2:57:55 PM12/11/21
to Dhvit Mehta, BBR Development
You can use a BPF program to do that sort of thing. Here's an example BPF program to set the congestion control algorithm based on the port number and IP address range:
 https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/samples/bpf/tcp_cong_kern.c

neal


On Sat, Dec 11, 2021 at 1:14 PM Dhvit Mehta <icm20...@iiita.ac.in> wrote:

I want to know if I can allow only a few TCP connections to use BBR, I want to run Cubic or any other algorithm for the other connections

As far as I know once BBR is enabled using the systctl method it will be used for all TCP connections on the sender side

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