AT&T throttling bandwidth anytime a direct dropbox.com download is started
I have a Pace 5268AC router connected via the 18Mbps plan.
I spent about an hour tonight troubleshooting an issue with AT&T technician David who works via phone from Wisconsin. Here's what we finally deduced: Attempting to download a large (2GB) file via a web browser from dropbox.com results in my broadband WAN internet connection being throttled down to less than 1Mbps (with an effective download rate of <200Kbps.) A few minutes after the download is cancelled, the broadband WAN speed goes back up to normal.
How did we deduce this? David created a new network SSID on my router and had me only connect one device to it (so that no other devices would interfere with the test). The speeds were fine, in-line with the plan I have. I could visit sites, watch videos, run speedtest.net, etc. with no issues. Then, I would attempt to download a large file from dropbox.com. Within a minute of initiating the download, my overall broadband WAN connection speed would throttle down to <1Mbps. The download would suddenly become impossible (appearing to require 10+ hours to complete). If I tried to visit other sites, the connection was terrible. At one point, my broadband connection actually went down (the broadband light on the modem went red and I got an error showing "Broadband connection not available"). But then, if I stop the browser-based dropbox.com download, within minutes my broadband WAN connection speed goes right back up to ~18Mbps.
We tested this multiple times, and it is 100% reproducible. The AT&T network is simply rigged so that users cannot download large dropbox.com files directly.
You might say, "Well, the dropbox app and other filesharing apps use up a lot of bandwidth." But I wasn't using the dropbox app. I was using a web browser to download a single file. No filesharing apps are even installed on the one machine that was connected to the network.
You might say, "Well, the problem was that your download was eating up all the bandwidth, so the rest of your connection was slower." But that's not true. The download speed of the file itself went down to <200Kbps. And along with that, speed tests (both AT&T and Speedtest.net) showed speeds of <1Mbps. It wasn't that I was getting some great download speed on the file, and somehow the remaining bandwidth was "eaten up." Literally, my entire connection went down to <1Mbps.
This needs to be fixed. These are legal files I was downloading for legitimate purposes. AT&T should not be in the business of throttling my connection.