Technical IT Question: How do I troubleshoot interruption of downloads with browsers?

In short, in a certain network, users get their downloads from cloud storage providers interrupted - it invariably hangs when using Dropbox, and downloads from other providers too. (OneDrive seems to be an exception, curiously enough.) There’s no error message or anything, it just stops after a few MBs. It doesn’t matter which browser I use.

I’ve been working hard with the firewall but i doesn’t matter whatever I temporarily turn off. It’s not a Windows Server issue, because downloads in general work fine.

I’m not an expert on such tools, but Fiddler for instance show nothing strange. There’s a connection, and all seems fine, but the download hangs.

I don’t know how to troubleshoot this further. Somewhere there should be some indication of what it is that makes this happen (in browser or otherwise) – but I don’t know where to look. – The smallest hint is appreciated.

PS. I’ve been googling extensively, but haven’t had any hits on this particular scenario, but getting tons of “false positives”, so to speak.

If the issue can be reproduced semi-reliably, Wireshark or TCPDump to see which side is aborting/resetting the connection. Syslog router info and review. Sounds like something is forcibly dropping the TCP connection.

Thank you for your reply, Caldazar. I did fire up Wireshark but it was just much data. :confused: I used to know my way with old (Windows) Network Monitor, but that was a long time ago. I’ll give it another shot, perhaps it seemed more complicated than it was. I’ll try you other suggestion as well, and see if I can get some more logging from the router. It’s Friday afternoon where I am so I will quit for the day but look forward to give this (frustrating) problem another shot with new ideas. Thanks.

Filter the Wireshark display output with something like:

tcp.port eq 80 or tcp.port eq 443. Sort by time/packet number and scroll to the end. Chances are there will be entries highlighted that indicate an abort of some sort.

Debugging on your border router may be more revealing, though, since you’d be sitting between the two traffic endpoints.