2012R2 in colo - slow transfer speed in one direction only?

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ninja6o4

Member
Jul 2, 2014
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I have been bashing my head against the wall on this all day and can't make heads or tails of it. I've run iperf and throughput tests, ran TCP optimizations/tweaks, and yet the problem persists.

2012 R2, hosted at a colo in my town on 1Gbps symmetrical.
At home, 100Mbps downstream with 2012R2, Win10, ubuntu clients.

Using CuteFTP and Filezilla / Filezilla server as test setup.
All three clients get max speeds from colo test files, yet peaks at 3.5MB/sec via FTP from colo. It looks like a virtual ceiling as the speed chart is a straight line.

However, if I FTP upload to home, from the colo, it maxes out the line at 11MB/sec, with variations for congestion.

Can anyone help me figure out why initiating the download from home has a ceiling, but uploading from the colo has no limit?