Setting proper SQM to ensure low latency and jitter

Installing and Using OpenWrt Network and Wireless Configuration
#21

Alrighty, really big thank you and dlakelan for helping out, I have one more question tho - would changing stuff like checksum offloads etc. on my network adapter would help anything a little? Because it seems like my connection has problems when it comes to sending bigger packets and it probably fragments em very often during gaming, that's why my ping fluctuates horribly probably.

Here's the test I made just now with those 2 SQM instances:

seems pretty good overally for this connection, but If I can somehow combat that bufferbloat a little more, it would be great.

#22

So, let's just do a little math to help you understand the limits of what's possible.

if you have 470kbps upload, then to send a single 1500 byte packet it takes 1500*8 / 470000 = .026 seconds. So, the smallest your jitter will ever get if SQM is tuned perfectly is on the order of 25ms.

Basically, at those speeds, you want to be the only person on the network if you're a gamer. The only way to combat this is to either subscribe to something with about 10x the upload speed, or actually to buy a second line and dedicate it to low-latency communications purposes.

#23

Thanks for clarification dlakelan, well, at the place where I live I have a very limited choice of ISPs, I will try swapping to an ISP who can probably connect me through broadband but we'll have to see if that's even possible. So far thank you for the help again and best of luck to you!

#24

Well, I am resurrecting my topic because I have some more questions and doubts regarding my situation and if some of those could improve anything.

  1. Should I change my MTU size anywhere if ISP itself is reducing it to 1480 and should I change some SQM settings according to it?
  2. Would marking certain packets with DSCP high prio marks improve anything? I need it only for one application.
    I have resolved some issues with my ISP, but ingame I still experience "skipping" from time to time, latency ingame hovers around 50-70ms with no packet loss, but still "skipping" occurs e.g. when sprinting it sometimes teleports me a step/frame backward, feels like a delayed packet.
  3. I have also found a fancy program which you probably know - startrinity continous speed test - as you can see below my uplink is struggling really hard, but first of all I don't even know if that program is accurate and I am reading it right.
    uplinkloss
    uplinkloss1920×1051 166 KB
#25

You could try to follow https://forum.openwrt.org/t/sqm-cake-and-being-a-twitch-streamer-upload-direction/62474/13 and @StarWhiz's linked blog post to get upstream priority for your gaming packets/gaming host. Please note that for ingress that is much harder....

1 Like
#26

Nah, didn't help at all... My ISP just somehow made their host (to which I am connecting first after my home network) less prone to packet loss, its nearly 0 percent, but my ping jitter is still around +- 100, so it's really unplayable. I have ordered a new router+modem from another ISP to try LTE connection (their BTS is 1.5km from me). I'll try it and if it will look promising, I'll probably get an directional SMA antenna to improve the signal. We'll see in next few days... I am already super tired from trying to get things to at least bearable state so I can just play the game without lagging around, but I cannot see the end of it yet...

#27

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I was also wondering if this test would help to understand the situation - I have typed in 0.03s packet interval with 280 byte size to somehow imitate the game connection - it seems like the antenna device (3rd host) is the first to delay stuff and increase the latency... I am wondering if showing this to my ISP would help them locate the problem or will I basically make myself look like a fool?

#28

this clearly shows that the device with IP address 192.168.240.1 occasionally causes delays of hundreds of ms as all devices after it have worst case times that are high like that.

if these are wireless devices it may be an inevitable issue with interference or lack of signal strength from your transmitter etc