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XPS 15 9550 inconsistent wifi-speeds

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When I try my wifi speed on my XPS 15 9550 I get really different results depending on how I test it.

On http://bredbandskollen.se I get my full internet speed of 500Mbps.

If I try http://beta.speedtest.net I get around 270 Mbps.

Doing an HTTP download from http://speedtest.tele2.net I only get around 40Mbps.

I also tried downloading a file from a samba share on my server and get around 130Mbps.

All these sources max out my connection if I try over a wired connection.

I have also tried changing the Dell Wireless 1830 with an Intel AC 8265 and that didn't make any difference.

I also tried putting the 1830 card into an Intel NUC and got much closer to my max connection so I think it's safe to assume the card is not the issue here.

Where should I look into next?

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1 Copper

RE: XPS 15 9550 inconsistent wifi-speeds

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So just after I posted this I realized I have a USB 3.0 to ethernet adapter laying around so I tried that as well. Same issue.

This led me to the conclusion that the issue has to be software related and most likely somewhere in the Windows networking stack. With that in mind I took to Google and found this article: blogs.technet.microsoft.com/.../.

And sure enough, Receive Window Auto-Tuning Level was set to disabled. Setting it to normal solved the issue.