On Mon, Apr 13, 2015 at 7:32 AM, Sebastian Moeller <moeller0@gmx.de> wrote:

> > >         "Squash DSCP on inbound packets (ingress):” this will replace all DSCP marks with 0x0 (I believe), but only after the ingress qdisc.
> > > In essence this means you can actually interpret ingress DSCP marks from upstream ("Ignore DSCP on ingress” set to ALLOW) but wipe them after the ingress shaping (with "Squash DSCP on inbound packets (ingress);” active). So the default should be “Ignore DSCP on ingress” and Squash (the second can be argued, as long as no one bases routing decisions on the marks they do not hurt). The rest of your questions are beyond my expertise...
> >
> > Hmm, why would we want to remove all DSCP on output then?
>
>         Because often we do not want to trust the internet to do the right thing and not game our classification? At least this is a common argument made...
>
> > I assume many ISPs and routers will squash them anyways,
>
>         ISPs are free to set the DSCP values to whatever suits them, and sometimes they do weird things, in essence per default we should not trust them...
>
> > but wouldn't it serve *some* purpose to differentiate between different traffic types?
>
>         Sure, if you know what you do setting reasonable DSCP values for VoIP sounds like a good thing (but due to fq_codel’s inner working might not be required). Alas iptables is only available to us after the packets went through the IFB, so any resetting of DSCP values would be for internal network nodes, our shaper unfortunately can not use this information…