The Mysterious Bandwidth Drop caused by Dell's bloatware
I do remote work from our home office, we have redundant WAN, wired gigabit ethernet to each desk, a pretty decent Ubnt AP if we decide to roam, and a symmetric 600Mbps FTTH connection and it performs quite well…. Except for my girlfriend.

A couple of months ago she got assigned a Dell Precision laptop besides her Mac, given her line of work she needs more beefy graphics adapter than those from an over-the-counter Mac laptop could offer.
As she settles in and starts using the Dell laptop regularly instead of unplugging and plugging the Mac, she starts telling me that from time to time her Internet becomes sluggish, we switched her wired connection to a dock, then a USB-C gigabit connector, but this random issue still happens from time to time.

I don’t think of it much as every time I run Fast or Speedtest on her laptop I get over 80% of the ISP speed stated on the service contract, and I don’t have this issue, so I brush it off and blame a transient problem with Box or any other cloud storage she’s using… (I have seen Azure blob storages / network shares working slower on certain ISPs that might be doing some kind of selective throttling, so I simply conclude it has to be something similar…)

This year as her team members start getting back online to work after the holidays she has to hold conference calls more regularly. And she starts complaining during each call that her internet is slow… but again, a few moments later once I’m available and she’s also available I check her laptop and I get speeds 80% - 85% of the advertised bandwidth from my ISP.

Her work involves uploading 50GB collections of files, sometime even 150GB at a time, so I wonder if she’s multitasking other uploads or downloads that might slow down her connectivity… Until today…

- Hey fcq, I just found out! My internet connection gets REAL SLOW when I answer Teams calls!

I go to her desk and she’s running fast.com she’s only getting like 20/30Mbps out of the 600/Mbps This makes no sense! She hangs up the call and the speed test starts going faster and reaches a decent result. Then she runs fast.com again and she gets the max speed!

I told her to start a call and we saw the drop in the speed! It is Teams!!!, or is it?

I’ve never seen anything like it, I checked the settings on Teams and there is nothing even resembling like a QoS or network setting there…
So a couple of Google searches later I found this

https://answers.microsoft.com/en-us/msteams/forum/all/teams-throttles-internet-when-calling/9fcbf261-a5b6-490d-a1d8-750a0b8a6da9

As OwenWhitehouse points out:

* I traced this issue down to the Dell Precision Optimizer. What a piece of garbage this app is. In the Network settings, there is an option to give conferencing apps maximum bandwidth, and IT IS ENABLED BY DEFAULT.*

I immediately open this mysterious app from Dell I’ve never even bothered to open, and voilà, there is that setting turned on, I turned it off and problem is gone!

So, the mysterious bandwidth drop during Microsoft Teams calls was caused by Dell…

I wonder who on Dell thought that crippling the overall bandwidth to 5% is beneficial AT ALL.

(Edit: Formatting...)