Question download speed suddenly slows down while upload remains fast

Nov 9, 2020
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Hello,

as title says my download speed suddenly slows down while the upload speed remains proper, i have ultrabroadband fiber 1000/200.

I will explain thoroughly

I turn on my pc and the download speed is just fine at approximately 350mbps, after a while especially if idle it slows down to 1/2/3 max 6 mbps while upload speed remains at 200mbps.
Other devices in the network do not encounter the same problem, tablets, smartphones, smart tv work just fine, speed test show normal results.

I tried rebooting the router and does not solve the problem, If i reboot my pc download speed returns to normal.

I tried rolling back wifi adapter drivers, same problem.
I tried rolling back windows updates, same problem.

my pc has the following hardware

Intel i5 9400f
16mb hyperx ddr4 RAM
MSI b360M PRO VH
GTX 1660 SUPER
INTEL WIFI6 AX200 ADAPTER produced by uBit http://shorturl.at/mqtFG

router is supplied by ISP and is MediaAccess FGA2130FWB

i write from Italy

It is clearly a software problem

I searched online for days if someone asked the same issue, found similar situations but not quite the same.

thank you very much in advance to anyone who responds.
 
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Nov 9, 2020
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One more test done, when internet speed is slowed down so is WLAN file transfer, a download of a file from NAS to pc is of approximately same speed as measured in speed test online.

The problem is not internet related in any way.

All other devices in the network do not experience any kind of problem.
 
Last edited:
Nov 9, 2020
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How does this system perform when connected via a wired connection?
Good intuition, if with wired connection the problem does not appear we can say with reasonable certainty that the problem is with the wifi adapter.

The PC is on the other side of the room from the router, I have not tried this yet, I will buy a long enough LAN cable and do the test. Will report back in a few days.

Thank you for now.
 
Nov 9, 2020
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I'm back to report, with wired connection there is no issue, absolutely, connection is stable as was with wifi until the issue started.


I bought the new wifi adapter on the 10th of august. NO issue what so ever until end of october, approximately on the 30th or 31st.

In the past days I searched thoroughly on the web and i found a post on reddit where this user had the exact same issue and found that the problem was caused by MSI dragon center wich has bundled in a connection manager software called cfosspeed. I tried first to disable network access on firewall to both this software and dragon center as a whole, not solved, then i tried uninstalling both, not solved.

I tried uninstalling my antivirus and firewall (kaspersky), not solved.

Any ideas? anyone?
 
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Nov 9, 2020
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The adapter itself could be the issue.

Back to report,

I changed the adapter, bought a new TP-Link Pci-E wifi adapter, installed it, but the problem was not solved.

I then by chance realized that the connection slowed down after I opened sonicwall global VPN software, did a speed test and closed the application during the speed test and from 3/4mbps it skyrocketed to 350mbps.

Did some research, its a recurring problem, microsoft explains it here, and has a fix for it.

https://answers.microsoft.com/en-us/windows/forum/windows_10-networking/wifi-issues-with-creators-update/4a20ba4f-33dc-4397-9823-e12dcb2607ba?auth=1

It is sufficient to disable Receive Segment Coalescing on the wireless adapter, or download the patch in the link above.

Thanks COLGeek for helping and to anyone that took the time to read.

Hope this is useful for future reference.
 

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