This is embarrassing, but I seem to have inadvertently set a persistent bandwidth throttle on SSH connections from my Ubuntu machine.

When transferring files from a remote server via scp, sftp, or rsync, the download rate is throttled to 2MB/s. When transferring files to the remote server, the upload rate is unthrottled. From other computers on the same network, transferring the same files from the same remote server, I can fully saturate my download bandwidth.

This didn't begin until roughly three weeks ago, and prior to that, I have frequently transferred files from this remote server for several years. Sometimes I would throttle the download rate with rsync's --bwlimit flag.

It's possible that I limited the bandwidth via some other mechanism while intoxicated, but I have no recollection of doing so, and I cannot find anything in my command history that indicates this.

I've checked my router's QOS settings multiple times, it is completely disabled. I've combed through the rest of the router's settings interface (it's running Tomato FWIW) to no avail.

What could possibly be throttling this specific machine's download rate?

Things I have checked:

  • usage of ionice or nice
  • usage of wondershaper
  • usage of trickle
  • router settings

Does anyone have any other thoughts on what to check or how to debug this?

  • Does the issue only occur over SSH, or also for other TCP connections? (If there's no HTTP, FTP, or similar service running on the server, try playing with iperf, nc or /dev/tcp). – TooTea Nov 2 '18 at 10:07

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