Need advice - large throughput drops when downloading large files (single threaded only) - via ethernet

[g67575]

I'm getting large throughput drops when downloading a 1GB file from the following server (and other similar websites):

Download Test Files

Download speed test files to help diagnose problems.

xcal1.vodafone.co.uk

Here are some screenshots of the issue on an ethernet 1gbps LAN connection:

The same problem occurs via WI-FI also:

I've tried the same ethernet port in my room with a laptop, and the 1GB file downloads at a steady 400mbps.

The issue only occurs with single threaded / single connection downloads (multi connection downloads are approx. 400mbps), it's very strange.

My ISP is Virgin Media, technology type= FTTP (via Nexfibre).

The testing I've done so far indicates an issue with my PC, I think it's probably a Windows 11 issue. Changing the ethernet adapter makes no difference. I've tried a full reset of the network connection, followed by a full repair of Windows 11, but no luck yet.

EDIT - tested safe mode with networking as well, with the same result.

 

[g67575]

Do you have jumbo packets enabled in the Advanced tab of the NIC's properties?

It's disabled.

A couple of days ago, I found out about different TCP profile configurations in Windows, which can be changed with this command via command prompt:

netsh interface tcp set global autotuninglevel=

The options are:

• disabled
• highlyrestricted
• restricted
• normal
• experimental

Setting it to disabled seems to stabilise the download rate, but reduces the bandwidth significantly.

I'm going to try a Linux Live CD install, to see if Linux behaves in a similar way.

 

[g67575]

I followed a guide to install Windows 10 (Windows to Go) on an external SSD, and I'm impressed with how well Windows works installed like this, seems to be fully functional. Ideal for testing.

You can tell Rufus (used to install the ISO file to external drive) not to allow this Windows version to access other drives on your PC, which is very useful.

I've just tested downloading the same 1GB file in Chrome and it seems to be downloading very consistently and well:

Test 1:

Test 2:

It's pretty annoying tbh, I last reinstalled Windows 11 a couple of months ago, and I've already run into a problem I can't solve.

 

[g67575]

Nah, there's a huge difference. The downloads complete more quickly on my W10 install.

On Windows 11, the download time was approx. 27 seconds.

On Windows 10, the download time was approx. 21 seconds.

in this post:
https://forums.overclockers.co.uk/t...aded-only-via-ethernet.18998672/post-37632989

This is showing Windows 10 (test install on external SSD), the initial post shows Windows 11.

I haven't worked out the reason why yet. It's not the driver, I tried the W10 network driver on Windows 11 (had to disable driver enforcement), but got the same result.

 

[g67575]

I uninstalled malware bytes fully. I'll see if there's anything else.

I've just downloaded a Windows 11 ISO, and the same erratic downloading behavior can be seen here also:

I'm going to see what happens with a Windows 11 (Windows to Go) install on an external SSD.

 

[g67575]

I've tried it on Windows 11 (Windows to Go) on an external SDD now.

The issue doesn't occur, which means it's an issue with my install of Windows 11 on my internal SSD.

 

[g67575]

Anyone got any ideas?

I'm probably gonna have to backup files, format the C drive and re-install Windows 11, it looks like.

 

[g67575]

That's nice of you to offer

When downloading the 1GB file on Vodafone's server, I basically see a lot of 'TCP DUP ACK' messages, once the download has begun.

When Googling - this is what the generative AI has to say:

Google Search

Here's a snippet of the messages shown in Wireshark, with IPs removed:

 

[g67575]

I did the same thing in my Windows 11 (Windows to Go) external SSD install.

The capture showed almost entirely ACK packets, with 1 part showing a pattern of DUP ACK packets.

Not all that interesting to look at.

Back on the Windows 11 internal SSD install, when the bandwidth drops down to almost nothing I see these kind of messages:

 

[g67575]

I've formatted and re-installed Win11 on the internal drive, all drivers setup.

It's appears to be functioning normally now :

The above is at default settings (except for side scaling which seems to cause issues sometimes. Power saving settings off also).

I can make it even smoother by using this command:
netsh interface tcp set global autotuninglevel=restricted

setting autotuninglevel=highlyrestricted

seems to give the best overall results when it comes to TCP retransmission. At least, according to Mlab's speed test:

 

[g67575]

I think I finally figured out the cause of the problem.

I have just re-enabled 'compress this drive to save disk space' on my C drive, which is something I did with my last windows 11 install as well.

This can save quite a lot of space on a 2TB drive, and at the moment I'm only using a single SSD.

After the compression process completed, downloading now looked like this again:

I managed to reverse the effect by simply disabling compression on the user folder on C, which is where I typically download files too (specifically to the desktop).

I will think twice before enabling disk compression in the future...