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The last 3 days, I've been getting corrupt data when surfing and downloading from a 3G internet connection. This is easiest tested by downloading a zip file from anywhere (e.g. https://get.videolan.org/vlc/2.1.3/win32/vlc-2.1.3-win32.7z) and testing the archive for checksum errors. Tried the same transfer with a different ISP, and the zip archive was OK.
How is this possible, given that TCP segments have a 16 bit checksum? Are the TCP segments not transferred unaltered from the server I connect to (e.g. get.videolan.org) all the way to my computer?
Some background info:
- I connect via a Samsung GT-I8730 phone, which acts as a 3G modem+WiFi hotspot.
- I get the same problem on 2 different laptops connected to the phone.
- I've tried USB tethering instead of WiFi, but the result is the same.
- When I use a VPN service (IPsec IKEv2 native client), downloaded files are not corrupt. Still the same ISP and the same phone.
- I've tried a few large WiFi file transfers between the 2 laptops without any issues.
Its entirely possible the ISP is doing something to the traffic. It works with a VPN because the ISP isn't able to detect what your downloading. I would ask your ISP about this behavior. – Ramhound – 2014-05-02T13:19:44.430