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hamfish45's avatar
hamfish45
Tutor
Feb 11, 2019

XR500 bandwidth reduction with QoS enabled

Hello,

 

I have an XR500 at the latest firmware version (2.3.2.40). I noticed that when I have QoS enabled, my download and upload speeds are slightly lower than normal. I have a fiber connection, and with my PC directly connected, or if I'm connected through the XR500 with QoS disabled, my download/upload are at 480/118. However, if I have QoS enabled, I'm seeing a 2-3% reduction in speed, taking me down to roughly 470/115 depending on the test.

 

I realize this is a small reduction, but I was curious to know why this is happening. Is there an additional bandwidth buffer reserved by the router any time QoS is enabled, irrespective of anti-bufferbloat and bandwidth allocation settings?

 

I've tried testing QoS enabled with Anti-Bufferbloat at 70/70 on Always, When High Priority Traffic Detected, and Never, and have also reset Bandwidth Allocation to defaults with with Share Excess option checked. Additionally, I unchecked the DumaOS classified games from Traffic Prioritization and removed all of my additional ports I had added for games not covered under the DumaOS games list. Testing under these conditions produces the same output as when I have everything customized the way I prefer it.

 

Any input would be appreciated.

 

Thanks

6 Replies

  • FURRYe38's avatar
    FURRYe38
    Guru - Experienced User
    Feb 11, 2019

    This is mostly called overhead with QoS. When enabled there will be a small portion of QoS that will show a bit lower speeds. If your getting to speeds with QoS disabled and just under with it enabled, then QoS is working correctly. 

    • hamfish45's avatar
      hamfish45
      Tutor
      Feb 11, 2019

      Thanks for the input. After performing further testing, I realized the download and upload bandwidth set under the anti-bufferbloat options actually dictates how much bandwidth the router allows, even before the anti-bufferbloat settings are taken into consideration. If I list it as 200/50, for example, my speedtest reflects just slightly under those numbers. If I list it as 500/125 (what I'm rated for by my ISP but I don't actually get these speeds even when directly connected to the fiber ONT), I get the same 480/118ish numbers as when QoS is disabled.