My desktop PC (Windows 10) has slow internet, high ping and jitter on Ethernet.

I ran out of ideas on how to troubleshoot and fix this.

[UPDATE] This happens on this Windows 10 only (ie. software issue). It's fine on Linux on the same machine, and on other Windows 10 laptops.

[UPDATE 2] I get slow speed on speedtest.net and speedtest.exetel.com.au (my Internet provider's) only, on all browsers (Chrome, IE 11, Firefox, Edge, Brave). But I just tested Torrent and got full speed! Now I am really confused.

[UPDATE 3] I noticed a download (from the same Chrome browser) could reach fullspeed! Immediately re-tested speedtest and get half-speed as usual. This is too weird.

The issue:

Average result using the same LAN cable / docking station:

  • On the desktop (Windows 10):
    20 Mbps / 18 Mbps, 30ms / 10ms (<-- Download/Upload, Ping/Jitter)
  • On the same desktop (Ubuntu) and on other Windows 10 laptops:
    52 Mbps / 18 Mbps, 13ms / 2ms

My findings so far:

  • It is not the router or LAN cable, because the same cable achieves much higher speed and much lower ping/jitter on my other Windows 10 laptops (both directly (Ethernet port) or via docking station (USB 3), WiFi disabled to be sure).

  • It is not my docking station, because using Ethernet from the docking station on laptop (via the same USB 3 cable) is still fast, and plugging in the LAN cable directly on the PC is still slow.

  • [UPDATE] It is not the hardware, because when I try Ubuntu USB on the same machine it is fast (same speed as my laptops).

What I have tried:

  • How is the docking station connected to the laptop. What are the specifications of the USB LAN adapter? Instead of submitting a comment you should edit your question
    – Ramhound
    Jul 28 at 5:50
  • By unplugging the USB 3 cable from the PC and plugging it in to the laptop - Is that what you mean? I'm not sure how to check the specs of the USB LAN adapter. I have edited my question. Thanks
    – Aximili
    Jul 28 at 5:57
  • What's the usual CPU usage on the PC? What's the CPU on the PC? (Perhaps it literally can't keep up?) What non-USB Ethernet card does the PC have? Have you tested using other tools than web-based Speedtest (e.g. iperf3)?
    – user1686
    Jul 28 at 6:56
  • 1
    @Elikill58 Good point! I thought I did but I haven't updated all yet! I will try updating all thanks!
    – Aximili
    Jul 30 at 12:45
  • 1
    Why do you rule out drivers?
    – harrymc
    Aug 2 at 9:16

Taking into consideration all the details in your question and all the comments below it, I'd look for a solution elsewhere. Namely, in the software.

OS level network tuning is one thing and software has its ways to influence connections. This would explain why your torrents are fine.

I won't give you exact steps here. Just a few points:

  • What browsers have you tried? Can you give a go to some other ones and compare?
  • Search the web for "browser flags". These are runtime parameters, which may help.
  • If you're into software compilation, you might take a look, what can be done there. (Just an idea, I'm not sure, what you'll find.)
  • Analyse the traffic with Wireshark. This will give you more info, but it's a slightly advanced topic.

Edit: It still doesn't explain ping and jitter, but can introduce some news.

Edit: Malicious software activity also crossed my mind.

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