Does having an asymmetric speeds affect sqm?

I'm not sure if this question can go to "Installing and Using OpenWrt" so I'm asking here. I'm just a gamer trying to resolve bufferbloat and after roaming around and openwrt website, I figured flashing and openwrt things are just too complex for my little brain so I decided to buy a router with a stock firmware of openwrt. I got the Convexa-B from GL-iNet since it was highly recommended for its specs and ease of use. My internet speed when I first got the router was 600/15 and I was running fq_codel with simple.qos and my bufferbloat went from D to A if I remember correctly. And then cake became available and somehow I could not make things work no matter what I do with the sqm settings. Regardless of script or speeds I run on, I kept getting a B on and I got frustrated. I could not figure it out and I got really pissed with my ISP(Comcast) so I went to a store and told them to lower my bill. They happily did that and even increased my plan from (600/15) to (800/15)! I was so excited to come home and behold, the bufferbloat tests with cake on is now graded at C. Because I consistently got a C with cake no matter what tweaks I did in the settings, I went back to the reliable fq_codel but now the best grade I can get is a B! Which is just not good enough to game on honestly.
I really want to get the most of the download speed I'm paying for but that's just too ambitious I guess. So now I'm considering downgrading to (300/10) or even (200/5). Will downgrading resolve my issue? Or do I just need to learn/master the sqm settings? I'm also considering flashing the convexa b with the actual openwrt firmware but I just feel like it won't make a difference at all. Please help this poor newbie(and if you could, make your suggestions/instructions as dumb as possible because I really don't know much at all and everything I've done were from following youtube tutorials).

Having asymmetric speed should not be an issue with sqm. The only problem I would see is that download speed is disproportionally higher compared to upload speed and upload is congested from the acknowledges. In any case, sqm needs some tuning in regards to available speed as well as overhead, then some fine tuning to achieve the best result.

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If you mean down grade your plan that is not really relevant.

What ever your plan is you need to measure your upload and download speed.

Allow for overheads and then only use a percentage of the remaining bandwidth in each direction for sqm.

Maybe 85%

@trendy has hit the right spot here:
Having upload only 1/40 or 1/55 of the download is the main problem. The protocol traffic related to downloads is choking your upload.

That narrow upload also causes more upload prioritization calculation work, especially with cake that is more CPU intensive than fq_codel. (Originally cake was efficient, but devs added a bit too many bells and whistles to it. And the development was mainly down without CPU constraints.)

As you noted, you might get better results with simple/fq_codel. If that works for you, be happy. Cake is no magic bullet.

You might also limit download speed in cake, so that also the protocol upload traffic gets more manageable. (If your goal really is bufferbloat and good latency)


I think this could be a problem as well (in addition to the asymmetry between upload and download.) I don't know the specs of the Convexa-B, but it might not be able to shape traffic at 800mbps.

  • You were getting an A at 600/15
  • You increased the speed to 800/15, and your grade went to C
  • Maybe the router can't keep up?

A wacky thought: What would happen if you dropped the ISP speed down to, say 250 or 300mbps? Possible good effects:

  • That would likely decrease your bill (even further?)
  • That decreases the asymmetry, improving cake/fq_codel's ability to shape traffic
  • So the latency/responsiveness might even improve, since the router can keep up better

My bet is that you wouldn't even notice a difference in performance. People say, 'The network is slow' and the actual cause is high latency. If your router can keep the latency low, it'll always feel responsive, and it'll feel just as fast.

I'd love to hear the results of this experiment. Thanks.


use fq_codel on the download, cake ack-filter on the upload