Very bad latency when WAN upload is high

  • I'm on ADSL with a 1 MBit/s upload. This sort of connection really needs some sort of buffer/queue management to not have uploads introduce massive latency. It seems like the Amplifi doesn't have any sort of Smart Queue or fq_codel implementation? Or is there some setting I'm missing somewhere?

    Here's a speedtest showing the very bad latency on upload

  • As far as I can tell there's nothing in Amplifi to fix this, so I ended up configuring an EdgeRouter X in bridge mode between the ADSL modem and the Amplifi. The ERX just does it's Smart Queue thing and that's fixed the huge latency spikes on upload.

  • @dan-everton Thank you for the update! Yes, AmpliFi has wireless QoS features, but the EdgeRouter X will have more advanced features.

  • Hi @dan-everton - what settings did you use to configure the ERX in bridge mode?

  • Hi @ubnt-brett - would you be willing to share how to configure an ER-X as a simple Smart Queue control bridge device?

    It would be great to to see if this could improve Teleport streaming.

    How does one create the transparent bridge and enable Smart Queue from the EdgeOS GUI?


  • @derek-saville You can configure this in the QoS > Smart Queue section and basically only need to define the WAN interface + speed.

    There is an example in the release post:

  • @ubnt-brett I understand the WiFi QoS features but as far as I know they only affect performance from the Amplifi to the WLAN client devices. With the slow WAN speeds I have it'd be nice to have some sort of QoS like fq_codel or cake to better manage the slow internet connection.

    I originally used an EdgeRouter X but found the complexity a bit much so was hoping Amplifi would provide a turnkey solution for this.

  • To me it would be interesting if AmpliFi created their own firmware images for the ER-X or even the USG to "amplifi" them so they play nicely with and/or manage the AmpliFi mesh network and allow for more advanced features to be tried out.

    I would personally pay for a WiFi-less AmpliFi Security Gateway with more options exposed...

  • @dan-everton @Derek-Saville In the past, people have requested fq_codel in AmpliFi. I will add both of your requests to the list as well 🙂

  • @ubnt-brett can you explain how the Gamers Edition with NVIDIA QoS works? Is it WLAN only or does it work in the WAN traffic as well?

    Basically, do I need to buy a gamers edition if I want WAN QoS features?

  • @Dan-Everton / @Derek-Saville I've been looking to add some sort of QoS/Sqm to my Amplifi HD system and trying to figure out if an Edgerouter ER-12 would work.

    How did your ERX end up working out in bridge mode between your modem and your Amplifi?

    I'm thinking an ER-12 because it has a faster processor than the ERX and also has a switch chip which is supposed to be better for bridging.

    Is it just a case of bridging eth0 (WAN) to say eth1 (to Amplifi HD WAN) and then applying QoS to IP address of devices connected to the Amplifi HD? (All my devices on my Amplifi HD has static IPs).

    Or @UI-Brett do you know if this is possible?


  • @LainB The QoS settings between the EdgeRouter products should be the same, but for better clarifications I would direct this question to their community where the experts who use those products may better assist. I have found a support article about QoS on EdgeRouters that may help.:

    You would need to place AmpliFi into Bridge Mode, which means you may also need to reassign all of the static IP's using the EdgeRouter.

  • @UI-AmpliFi Thanks for the article.
    I don't want to Bridge the Amplifi and loose all it's app features which is why I was looking to bridge the EdgeRouter so there's no double NAT and all it's doing is QoS/Sqm between a Ethernet port and the WAN.
    When Dan said he Bridged the EdgeRouter, I'm assuming that's what he did instead of Bridging the Amplifi.

    I've found some posts on different forums from years ago about people bridging the Edgerouter and putting it between modems and routers for QoS, but nothing 100% complete, the threads pretty much stop when they say they got it working. So I just ordered an ER-X to see if I can get it to work and if it works but at limited speed I'll swap it for the ER-12.

    If Amplifi ever put into the Aliens QoS for wired devices like they already have for wireless I'd instantly buy 2 of them to replace my 3 HD units.

    Fingers crossed the Edgerouter works like this and I can get some sort of QoS/SQM mainly for my wired devices.

    Thanks again.

  • @LainB I believe you will lose QoS features on the Edge router when it is in bridge mode.. Either option it seems will have some cons.

  • @UI-AmpliFi Ya, I would have thought that also but I couldn't find a 100% definitive answer from someone who actually tried it. I could only find posts where people were looking to do it and then said they got it working but never said exactly how or confirmed if they did or didn't bridge the Amplifi HD.
    So figured best just to try it myself.

  • Hi @LainB - I believe my situation was a little different than what you are trying to accomplish

    I was suffering from buffer bloat when streaming from online video services to a HW Teleport abroad

    At the time, my ISP connection couldn't handle pulling in streaming video, repackage it with an HD for VPN, and then send it back out without significant latency hits causing pausing on the other end

    So I created a simple transparent bridged interface using an ER-X following these instructions (without assigning an IP address)...

    Then I could play with enabling SQM on either Ethernet port and play with the parameters

    It did improve the streaming quality, but not 100% of the time, and it only worked because the streaming rates were low enough for the ER-X's CPU to handle it

    I would remote login (via Teleport to ETH0 from a connection on the LAN side) to the ER-X and enable or disable the SQM as needed, as you didn't want it on full time

    If the ER-12 has enough processing grunt to meet your throughput needs you can probably make a difference by enabling SQM on the interface, but there were a lot of parameters to play with as you get into more complicated routing needs

    Eventually with a DOCSIS update to the modem and ISP infrastructure the buffer bloat problem disappeared and I no longer needed the band-aid solution

  • @Derek-Saville Thanks for the reply Derek. My bufferbloat rating is D right now 🙂 only a 15Mbps upload speed (200 Mbps down).
    When our desktops upload to a wed server or my NAS offsite backs up it saturates my upload and slows everything down. Figured I'd give SQM a shot to see if it can fix it a bit. Or at least add QoS bandwidth limits to the desktop and NAS for uploading.

    So from the sounds of it you were able to bridge the ER-X, leave the Amplifi as a router (full functionality) and still do SQM on your WAN. Is that correct?


  • Hi @LainB - yes, the ER-X was basically turned into a SQM buffer device

    Note that SQM could be enabled in both directions on any Ethernet port, so you have to be careful not to trip over yourself...the modem's download to the ER is the same as the ER's upload to the router and each could have its own settings even though they are trying to control the same thing

    But the ER-X's CPU was not very strong in bridged mode, so had to keep things as simple as possible

  • @Derek-Saville Perfect. I think that's what I'm looking for then.
    If I can get it all setup on the ER-X but find it's not powerful enough then it's just a case of upgrading to the ER-12.
    Thanks again for the info, I'm glad you chimed in to confirm you were able to do SQM when the ER-X is bridge, so as least I know it's possible when I'm trying to set it up.

  • Hi @LainB - it was possible, but I would say don't expect any miracles...and a lot of trial and error on settings

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