[Cake] Trouble with CAKE

[Jonathan Morton]

> On 13 Dec, 2019, at 3:43 pm, Thibaut <hacks at slashdirt.org> wrote:
> 
> I've been using CAKE on my DSL-connected Linux router for the last few years, and it worked well until very recently. Two things happened:
> 
> 1) My ISP (French "Free") switched my DSLAM to native IPv6, which for the time being means that I had to revert to using their set-top-box (Freebox) instead of the VDSL2 model I was using in bridge mode until then (CAKE in "bridged-ptm ether-vlan" mode)
> 2) I upgraded my router from 3.16 (Devuan Jessie) to 4.9 (Devuan ASCII)
> 
> Since then, no matter which setup I use, I cannot get CAKE to work as intended. Specifically, any long-standing best effort stream (such as a remote rsync) will be throttled to a near grinding halt even though there is no other significant traffic going on. Some random bursts can be seen (with iftop) but nothing ever gets close to half the maximum bandwidth. This is notably affecting the OpenWRT buildbots I'm hosting on this link.

Old kernels, including 4.9 series, tend to be more problematic than the latest ones.  If you can, I would recommend updating to a 5.x series kernel, in which Cake is an upstream feature.  I won't presume to guess how best to achieve that with your distro.

The good news is that Free.fr is among the relatively few ISPs who have actively tackled bufferbloat themselves.  As a workaround while you sort this out, you should get reasonable performance just from using the Freebox directly.

 - Jonathan Morton