[Solved] Bufferbloat Lag Fix

Hi All

How do I go about fixing bufferbloat lag on my router?

The speed I got on my old BT firmware was 32MB/s down 10MB/s Up.

This is my current speeds.





And now you show 14.7/10 and 16.2/9.7; I could be wrong but that does not really look like a bufferbloat issue (unless you are mainly concerned about the bufferbloat rating of C).
BTW for the excellent dslreports speedtest it is better to link the actual result summary image that you get to once you click the "Resukts + Share" button...
https://forum.openwrt.org/t/sqm-qos-recommended-settings-for-the-dslreports-speedtest-bufferbloat-testing/2803/11 has some pointers for configuring the dslreports speedtest, just in case...

Okay, this pretty much looks like your downstream is massively congested; assuming this is a VDSL link, what sync rates are reported by your modem?

sqm-scripts, if configured correctly, should help you in getting bufferbloat down, but it will not help getting more bandwidth....

I have BT FTTC VDSL link. I will give the sqm-scripts a go.

Should I set the Download and Upload speeds to 80-95% of the speed from the 14.55Mb/s down 8.04Mb/s up or the 32Mb/s down 10Mb/s up I got on the old BT firmware?


In the first iteration, base this in the speedtest results (say 90%) as that should get bufferbloat under control, then you can iteratively try to increase the bandwidth settings while measuring bufferbloat until you hit your sweet spot.
Ah, I would do:

15789 * 64/65 * 0.9 = 13991 Kbps
9989 * 64/65 * 0.99 = 9737 Kbps
Note the 64/65 is to account for PTMs 64/65 encoding.
There are two relevant thresholds, a) the actual sync rates which you will never be able to exceed and potentially b) a traffic shaper at your ISP. If the proposed values do not keep bufferbloat under control you might hit such a shaper, in that case start to gently reduce the sqm bandwidth setting until you are happy with the resulting bufferbloat

You might want to inquire with your ISP why your sync is so low, as your SNR seem quite high, indicating that there should be some reserves left.

I slit improvement on the speed.



Could it be that your ISP requires vectoring (e.g. Line Mode: G.993.5 (VDSL2 with down- and upstream vectoring)), with only a 16 MBit/s G.993.2 fallback profile?

Okay, that is still terrible, please try 10000/8000, and set the overhead to 26 (unless your ISP uses PPPoE then set the overhead to 34). This is now an attempt to find setting for which the bufferbloat rating does not get worse than a B...

I think the OP is confusing the conversion from Mbps to kbit/s...




For 32 Megabit per sec (Mbps) should I enter 32768 Kilobit per sec (Kbps) down.

9 Megabit per sec (Mbps) should I enter 9216 Kilobit per sec (Kbps) up.

Into the download speed (kbit/s) (ingress) set to 0 to selectively disable ingress shaping. & upload speed (kbit/s) (egress) set to 0 to selectively disable egress shaping.

Your new firmware is only syncing (raw line speed) to 15.8 Mb down, not the 32 you are subscribed for. This is either a misconfiguration of the modem or a firmware limitation. Need to resolve that first before looking into SQM. Right now the best download speed it will do is only half of what you're paying for.

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I would disable SQM for now and just test speed.

I would also select a server on DSL Reports that is closest to you geographically.

As an aside, Ookla now has a desktop version of Speedtest...


I don't have a standalone modem I have a Router = Router+Modem+Switch in one device.


I Need help for best config my QOS/SQM, above showing actual DSLReports before adjust parameters

Link: 50/10 - Gpon Fiber conected btridge in Archer C7

Hardware : TP-Link Archer C7 v2 LEDE @r00t last build.


Please don't hijack someone else's thread...

If I disable SQM do my router parameters go back to there default values?