Question Individual connections capped

Jul 19, 2019
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So I feel like this problem started maybe a month ago. On my PC (wired directly to my modem) each file download or connection seems to be capped at ~18Mbps (I have a network monitor running). If I download two files at once (say 2 Azure test blobs at once) each gets around 18Mbps and my total download is 34-36. If I use a download manager to split the file in parts, or Steam to download games, or open up 10 youtube links at once I can hit my provider cap of 250Mbps. I have a wireless network connected off of the modem (separate router) and two laptops on there can get the full speed for the same Azure blob file (takes just a couple of seconds vs a minute).

Summary/things tested:
Different browsers (Chrome and Firefox have same results)
Other machines connected can download at full speed
I turned off every running program and process I could, did not fix.
Restarted Modem/PC
Updated NIC driver
Multiple sites (azure test blob, dropbox, google drive downloads, random others)
Temporarily turning off AV/real time scanning/etc

(This may have coincided around the time I went through some windows updates to get GamePass and such working, but I don't want to say that cause as I don't remember exactly when it started. Nor do I want to blame my ISP before I see if anyone here may have heard or seen of this).

This specific issue is a hard one to search for, so wondering if this rings any bells for people here.
 

Ralston18

Titan
Moderator
On your PC are you certain that only one network adapter either wired or wireless is enabled? Not both.

Where is your PC getting its' IP address?

What/which device (modem or router) is providing DHCP IP addresses?
 
Jul 19, 2019
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Yes, this PC in fact only has a single wired adapter (1 thing listed in Network Connections).

PC is getting address from cable modem (192.168 off the internal side of modem). Connection is about 1 foot between the two.
 
Does the speedtest site also get restricted.

If someone asked how you would do this I would mostly say it can't be done. You would need some kinds of traffic management software.

Does it affect local file copies between machines.

All I can think of is a field call tcp window size. This field used to have a low limit on how much data you could have in transit and it would cap the transfer speeds based on the latency. Still for this to be the problem you would think you would see difference if you transfer to a site with much higher latency.

I have no idea where windows keeps this setting some tool may have changed the registry. The default settings generally work best except in unusual cases so I can't see why it would be changed.
 
Jul 19, 2019
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Speed test sites work fine. I get 240-245 with xfnity's test, and speedtest.net gives me around 150. The inter-PC test will take a bit as I don't immediately have a way to run that test.

I know that when I think this may have started, and friend and I were trying to get Gear of War 4 PC coop to work (which uses some Teredo VPN configuration to function). Most of the troubleshooting was done on his end (as we discovered UPnP wasn't working for him) and I did do a couple things to test on my end as well, but I think I set everything back. There may have been a registry setting change in there, so I will have to research the HATTON error troubleshooting to try to remember that.
 
That is extremely strange because speedtest really is a file download/upload that does not get saved. I can't see why it would be different. Any setting related to tcp windows size would affect all traffic.

There are other testing tools like iperf that will let you test raw transfer speed between machines in your house but I suspect that tool will not be affected so it will not give new information. It is easy to use so I suppose you could see if it shows anything.

I have seen issues with steam before but it is a different program than the browser. Microsoft is the site I normally recommend people test from, I know you can get close to 1gbit download rates if you have a gigabit internet.

Very puzzling You could try disabling ipv6 and maybe the teredo support but I doubt it is that.
 

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