[Bloat] AQM and PPP on Linux

[Toke Høiland-Jørgensen]

Juliusz Chroboczek <jch at pps.univ-paris-diderot.fr> writes:

> I'm currently away from home, and using a 3G modem for Internet
> access. I've found out that both NetworkManager and wvdial/pppd setup
> the interface to use pfifo_fast (with a qlen of a mere 3 packets!).
> Setting fq_codel manually appears to work fine, but needs to be redone
> every time the modem has a hiccup.

I don't think NetworkManager does anything to set qdiscs. The kernel
simple sets pfifo_fast if not told otherwise (but see below).

> Is that the expected behaviour? Shouldn't we be pushing patches
> somewhere to change the default?

What distro are you on?

There's a sysctl to set the default qdisc: net.core.default_qdisc. Set
this to fq_codel and you should be good to go. This is becoming the
default in more and more distros (currently at least Arch and Fedora;
and OpenWrt has been patching out pfifo_fast entirely for a while).

There's a bug for Ubuntu here:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1436945 -- feel
free to bug them :)

-Toke