Need help regarding SQM

[moeller0]

@AlanDias17

Connection type: PPPoE (So I guess there is no need to specify overhead. Cake handles it automatically?)

No not at all, you always need to specify the overhead, otherwise you will only get what the kernel might automatically add (0 bytes for pppoe). What kind of link technology are you using?

@AlanDias17

I agree default RTT 100ms is the best choice overall & I shouldn't change it.

So depending on where you live in relation to the game servers it might make sense to change these, but given your numbers I would leave this at 100ms.

@AlanDias17

But the thing is that even without load due to default 100ms RTT enemies are able to peek & shoot me before I could even react.

That is not how this parameter works, you basically just tell cake how long it should give each isolated flow to respond to a drop or ECN mark before dropping/marking more, if this is below the real RTT the flow will never reach full speed even if it would be the only active flow, setting it to high is more benign for well responding flows and for non-responsive flows the fq (flow queueing) isolation will make sure, that the increased latency coming from non responsive flows is only experienced by those flows themselves.

@AlanDias17

I don't have empirical statistics to prove but I did a lot of tests while playing lan game & found putting less than 30ms RTT makes it a fair match. I think it has to do with tight target so SQM has to send packets without waiting for 5ms more?

SQM will not really wait on purpose, these 5ms is just what cake will acccept as standing queue under saturating load (in cake you can not set this directly, so if you really need a shorter target you also need to reduce interval, which you will pay for with reduced throughput for TCP flows with longer RTT than interval, again a policy decision).

@AlanDias17

Alright so for this setup Squash DSCP on inbound packets (ingress) should be SQUASH.

Policy decision, you need to make, but unless testing what shenanigans my ISP does to DSCP marks, I normally squash them.

@AlanDias17

But here we're avoiding DSCP tags on ingress flow (ingress shaping is disabled on both SQM instances) hence this option won't affect result at all right?

It will make all the special DSCP assignments in your firewall.user moot for ingress...

@AlanDias17

So go with default options for both ingress/egress?

Sure.

@AlanDias17

sch_cake: Add DiffServ handling document suggests to tag gaming packets to CS4. I tried that but the end result was horrible even in unloaded network. CS6/CS7 works better for me.

I would assume this comes from your firewall.user. It appears that you are trying to combine a standard sqm-scripts installation with the bespoke qos-scheme from https://forum.openwrt.org/t/ultimate-sqm-settings-layer-cake-dscp-marks/ that is a bit tricky.

I guess you need to decide whether you want to go all in with the ultimate scheme or start (at least initially) with a more run-of the mill "white-bread" sqm-scripts install ;). I would personally start with the white-bread approach, if only to be able to appreciate all the goodness the ultimate-scheme buys you (as its complexity cost is obvious). But again, your network, your decisions.