[Bloat] The NetEm qdisc does not work in conjunction with other qdiscs

[Stephen Hemminger]

On Fri, 25 Oct 2024 21:55:21 +0200
Maximilian Bachl via Bloat <bloat at lists.bufferbloat.net> wrote:

> From my experience (experimented with it last year), it still behaves
> weirdly. You can use htb for the shaping and you can create delay using
> netem by using it on another (virtual) host on a link that does not have
> any other qdiscs and where the link is not the bottleneck.
> 
> Best regards,
> Max

Yes, netem has expectations about how inner qdisc behaves,
and other qdisc used as inner have expectations about how/when packets
are sent. There is a mismatch, not sure if it is fixable with in the
architecture of how Linux queue disciplines operate.

The best way is to use netem on an intermediate hop and not expect
it to work perfectly when used on an endpoint. The same is true of Dummynet
and other network emulators; they are uses as man-in-the-middle systems.