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I encountered many corrupted downloads recently. Sometimes compressed files wouldn’t open or checksums would not match. Sometimes images on Websites would just be grey (or a wild mix of colour) after a few lines of correct pixels.
So I decided to take a deeper look at it and ran Memtest86+ (5.0.1) for 24 hours with no errors.
To rule out my Internet connection I set up another computer as a simple apache http file host. I created some test files of ~100 MiB each but after transmission the checksums would not match. Not even the checksums of the whole set downloaded twice.
When I ran Wireshark during transmission I came across several “Dup ACK” packets and “Spurious Retransmission” Packets during the file transfer between me and the apache server.
The Checksum Comparison of two different downloads of the same set of files can be found in picture
and one example of the “Dup ACK” and “Spurious Retransmission” between file server and my machine is:
![[this][3].](https://i.stack.imgur.com/dVqkg.png)
Does anyone know likely causes for this behavior?
Kapt.Brackbier
Posted 2015-09-20T16:47:42.687
Reputation: 13
If you feel pictures will make your question easier to understand or allow us to answer it better, post the pictures anywhere and [edit] the question to include a URL to them. Someone with enough reputation will edit the pictures in if they are legitimate. However, please don't post screenshots of text; rather, copy and paste the text into code blocks (begin each line by four spaces). – a CVn – 2015-09-20T17:05:39.663
if this suddenly started the first port of call is your NIC. If this is over ethernet grab a USB WLAN adapter if you have one and test over WLAN. – Linef4ult – 2015-09-20T18:19:13.363