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[RT-AC88U] Slow download speeds (buggy qos?)

Discussion in 'ASUS AC Routers & Adapters' started by kgk, Mar 26, 2019.

  1. kgk

    kgk New Around Here

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    I am having a very strange problem where my AC88U router appears to be throttling my download speeds.

    My ISP is webpass, and is supposed to get >=100mpbs.

    If I plug my laptop directly to the ethernet cable from the wall, bypassing the router, my download speeds are around 80-120mpbs. However, if I then plug my computer to an ethernet jack on the router, my download speeds fall to 2-3mpbs. It is similarly slow if I connect to the router via wifi.

    The strange thing about this issue is that it doesn't affect my speedtest.net results. speedtest.net and dslreports.com both consistently report a download speed of >120mbps. However, in practice, my internet experience is much much worse.

    I have been using testmy.net to get results that seem to reflect my real-world download speeds. To verify that testmy.net is realistic, I used curl to download some various large files from the internet. I compared my curl download speed when plugged directly into the wall and when plugged into the router and saw a similarly huge speed difference.

    Here is the command I used (on Ubuntu 18.04):
    curl http://ipv4.download.thinkbroadband.com/512MB.zip --output 512mb.zip

    Wall average speed: 39.76 megabits / s
    AC88U average speed: 183.84 kilobits / s

    Note the unit for the first measurement is megabits, and the second is kilobits. Yes, I am struggling with speeds measured in kilobits / s :(. It is several orders of magnitude slower than plugging my pc straight into the wall. I tried a few other large files on the internet to make sure there wasn't anything specific to thinkbroadband.com.

    I have no custom settings besides creating the wifi networks for 5ghz and 2.4ghz and disabling upnp. While testing, I had no other devices on the network besides my computer. I changed the wifi password so all other devices would be kicked off. Disabling the wifi entirely with the button on the front also made no difference.

    So far I have tried / verified the following without any effect:
    * Upgrade / downgrade to new and older versions of merlin and stock asuswrt (factory resetting after each upgrade, and not restoring settings from file).
    * Disable qos (I originally had set up traditional qos with fq_codel, but disabled qos entirely for the whole time I have been debugging this issue)
    * Enable qos with all 3 different strategies, but set the bandwidth limits very high
    * Disable firewall
    * Verify ethernet cable speed negotiation. The merlin gui reports 1000Mbps negotiated speed on the wan port as well as on the lan port to my computer.
    * Replacing the wan cable (tried multiple different cables that I verified are good).
    * Use curl to download large files from various sites. I tried this while plugged into the wall (faster) and when plugged into the router (much much slower).

    I didn't notice the speed issue until sometime in the last week or two. Before that it has been running since January seemingly fine.

    I'm using cat6 cable everywhere. It's worth noting that the building is wired with some very old cables (cat 4 or even cat 3, I believe) from my unit to the antenna on the roof, sadly. But this doesn't affect my speed when plugged directly into the wall instead of through the router, and again, the router reports a speed of 1000Mbps for the wan ethernet connection.

    The closest post I found to my issue is this one. It looks like my issue, but it doesn't look like they found a resolution.
    https://www.snbforums.com/threads/slow-internet-speed-for-single-computer-rt-ac88u.37812/

    This video might also potentially be relevant? It was for a different qos-related bug.
     
  2. L&LD

    L&LD Part of the Furniture

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    This seems like a hardware issue with all you've described. For science, could you try putting the router in AP mode and connecting the wall Ethernet cable to the WAN port and seeing if the issue persists? It shouldn't of course, but if it does, looks like it's time for an RMA?
     
  3. kgk

    kgk New Around Here

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    Mar 26, 2019
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    It did persist after putting it in AP mode! Exact same behaviour where downloading a file over http was very slow (154kbps this time), but speedtest.net shows 130mpbs.

    It's so strange to me that speedtest.net is fine, but downloads are so slow! If it were a hardware issue, wouldn't you expect speedtest.net results to be slow too?

    Will probably RMA it anyways if nothing works in the next day or so.
     
  4. kgk

    kgk New Around Here

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    lol now I have to factory reset it again since I can't find the router's IP address and I don't want to do an IP scan on my ISP's switch ;)
     
    L&LD likes this.
  5. L&LD

    L&LD Part of the Furniture

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    Did you test all the LAN ports? Is there even one which works?

    Can't seem to understand how it can work with speedtest.net?

    Can you try reflashing the 384.10 RMerlin firmware, resetting to factory defaults, formatting jffs on next reboot and then performing an NVRAM erase, and doing this a few times (even reflashing the firmware each time)?

    Even if this fixed it, I would want to still RMA it!
     
  6. kgk

    kgk New Around Here

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    I tested 2 of the LAN ports. I also tested with wifi and it has the exact same behaviour. And just to rule out any kind of bizarre linux compatibility issue, I also tried it on my iPhone over wifi. Same deal.

    Resetting from factory defaults (I believe) over-writes nvram. I reflashed 384.10 merlin, restored factory defaults, and then I formatted jffs, then rebooted. No effect. I did it twice to be thorough.

    RMA time I guess :(
     
  7. L&LD

    L&LD Part of the Furniture

    Joined:
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    Resetting to factory defaults should over-write NVRAM, but it may not (if the router is not already in a good/known state). ;)

    If you did not check the box beside the button to perform a factory reset (the initialize all settings checkbox), then jffs should have been formatted on next boot. If you did check that box, then format the jffs partition on next boot should not be required.

    Doing the manual/hardware based NVRAM erase steps though are essential if the GUI is possibly not working properly (and in this case, that seems to be a possibility).


    WPS NVRAM Erase https://www.snbforums.com/threads/b...eta-is-now-available.55520/page-9#post-473141

    It is important to not only unplug the router from the AC power plug and wait a couple of minutes before attempting to erase the NVRAM, but it is equally important to keep holding the WPS button continuously after applying power until the router turns reboots too.

    After it has rebooted, I would also physically unplug the power plug from the router. Wait a few minutes and then power it up again.

    Additionally, my curiosity would have me trying all of the LAN ports. Just to 'know', if nothing else. ;)

    Edit: I may not have been 100% clear in my earlier post(s), try flashing the firmware repeatedly (at least two consecutive times in a row) after doing the above.
     
  8. kgk

    kgk New Around Here

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    Thanks for clarifying. That was super helpful!

    On my router, there is a small red button next to the WPS button that you have to use a paper clip / pin to depress. I have been using that to factory reset the device. With the router on, I press and hold that button with a paper clip for 10 seconds; then the power LED starts flashing, and then I release the button and the router resets. When it comes back up I manually reconfigure everything. I've been assuming that this clears the nvram.

    Just to be thorough I followed your instructions too. I reflashed merlin, and then used the GUI to do the factory reset this time (with the "reset settings" check box checked), instead of using the pin button. Then after rebooting, I had to reconfigure the wifi. Then I followed your instructions to clear the nvram using the WPS button. Then I rebooted twice, waiting a couple minutes in between each with the power cable unplugged. After it came back up, I reconfigured the wifi again and reflashed merlin twice. Rebooted just to be sure after that by pulling the power cable and waiting a few minutes. Whew.

    No luck. Still same behaviour. Made no difference. I even tried all the ethernet ports and both 2.4ghz and 5ghz wifi. All the same.

    I honestly think there is some sort of software bug related to qos that is throttling file downloads. That's the only thing that could explain what I'm seeing with speedtest.net being blazing fast, but file downloads being slow. Maybe @RMerlin knows more. I did have the new fq_codel feature enabled, and I had manual rules configured that deprioritized file downloads if the wan bandwidth was saturated. It worked great for a while, but maybe something got irreversibly corrupted?

    At this point, I've invested too much time trying to make this work. I'm going to see if I can RMA / refund this one, and buy a different brand of router in the meantime.

    Lessons learned form this experience:
    * Don't trust speedtest.net or dslreports.com results alone. Those sites will sometimes give numbers that are much higher than your actual download performance in practice. testmy.net appears to be much closer to reality, at least in my testing here. Also, just go curl some large files for yourself.
    * Invest in enterprise-grade networking hardware?

    I really appreciate the help on this forum!