[Jammy Jellyfish] Vote for TCP BBR by default

[Andrea Righi]

On Wed, Oct 27, 2021 at 09:47:48PM +0800, Daniel J Blueman wrote:
> One key distro leadership opportunity Ubuntu could introduce for Jammy
> Jellyfish 22.04 is to enable TCP BBR by default. It has matured
> upstream for 4 years already.
> 
> For communities further from the US/Europe, or with less strong
> network connections, this can make a significant improvement to the
> network experience and usability. Please take this as my vote!
> 
> Dan
> -- 
> Daniel J Blueman

I agree that using TCP BBR by default sounds promising and it would work
really well in many scenarios, but there might be still some downsides
in some environments (networks with shallow buffers in particular).

Fairness could be another issue (with other TCP streams that use say
Cubic or different congestion algorithms). BBRv2 should solve most of
these issues, but it's not upstream yet.

I'm not sure if it's for the reasons above or something else that
upstream is not using BBR by default. I think it would be nice to
address this topic upstream to get more information / opinions on this.

Moreover, BBR is already enabled in the Ubuntu kernel, it's just not the
default, but it can be easily enabled with a couple of sysctl settings.

-Andrea