OpenWRT Quality-of-Service module caveat: speed limit

As I still have “issues” with my DSL line being extremely slow during certain times (especially between 18:30 and 23:00), I wanted to use USB tethering from my OpenWRT router to my Android LTE phone to enjoy the massive speed I have in our area (up to 90 MBit/s downlink and 70 MBit/s uplink, according to the Ookla Speedtest.Net).

So I configured the router according to the OpenWRT wiki. The internet connection did not come up immediately, and I couldn’t find out why, so as a last resort I rebooted the router. After I switched on USB tethering again on my mobile phone (which seems to be required each time you reboot the router since the mobile phone then loses the USB tethering connection), I suddenly had a working Internet connection.

However, for some reason the Internet speeds I was seeing in Ookla’s web browser-based speed test (which is a Flash applet) were very disappointing, around the same speeds I’m used to with my DSL line (14 MBit/s downlink, about 0.8 MBit/s uplink). I thought it might be an issue with USB tethering not working well in my build of OpenWRT (still r39582), so I tried USB tethering with my Mac (using HoRNDIS). I got the full speed I expected. So back to OpenWRT…

Then suddenly I suspected what might be going on: Since I had more or less exactly the same speed as my DSL connection (with the uplink of less 1 MBit/s being dramatically slower than what I should get via LTE) I thought about what could possibly limit the speed. And then I remembered that in the “Quality of Service” (QoS) module I configured the speeds of my DSL line (at the top of the page, in the Download speed (kbit/s) and Upload speed (kbit/s) fields). Could it be that these settings actually limit your speed to these values?!

I disabled QoS, and immediately thereafter I got the full LTE speed I expected.

So, another thing learnt.

I hope this helps people who might be in a similar situation…

2 thoughts on “OpenWRT Quality-of-Service module caveat: speed limit”

  1. I had a similar issue, where with my freshly bought, and freshly flashed router, I was limited to about 1.5 down and .15 up when switching from my old DD-WRT 400N linksys
    I had to go to the QOS page, enable it, it was off by default, and set the up and down limits to values greater than my Uverse DSL was supposed to deliver.
    After that, I then got the same speed as I did before I switched to the OpenWRT router.
    It appears that the router sometimes obeys the QOS speed limits, even if QOS is unchecked and uses the greyed out default values.
    Hope this helps some others.
    My router specs are as follows:
    Model TP-Link TL-WDR3500 v1
    Firmware Version OpenWrt Barrier Breaker r40360 / LuCI Trunk (svn-r9964)
    Kernel Version 3.10.34

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