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Are SFTP up/download speeds something that's in the control of the hosting company? Can they throttle SSH traffic, regardless of the port?

I just signed up with a new hosting company. We'll call them Slow SFTP, Inc. I have another server with Fast SFTP, Inc. Both are in Dallas and both are in different data centers.

I noticed my SSH client (PuTTY) lagging when connecting to Slow SFTP, Inc., so I decided to run some tests from both companies. I ran several tests over several hours. I also changed sshd ports just to make sure traffic wasn't being throttled based on the port. It made no difference.

     | Slow SFTP, Inc. | Fast SFTP, Inc.
-----------------------------------------
UP   |    744 KB/s     |     352 KB/s
DOWN |    150 KB/s     |   1,723 KB/s

I find it strange that the download speed from Slow SFTP, Inc. is so much slower than the upload speed.

Note: These are 1:1 comparisons. Identical setups on both servers. No firewalls. Vanilla Debian 7/sshd installs.

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  • What speed transfer do you get between you machine and each Debian box via a different protocol such as HTTP? Try something like wget the same file from the web root of both machines. You know to baseline SSH against something to determine if SSH/SFTP is the problem here or something larger.
    – Baldrick
    Commented Jun 19, 2013 at 14:03
  • Well maybe you could install one? :p Or FTP? Or just use iperf between them and your home/office test machine
    – Baldrick
    Commented Jun 19, 2013 at 14:04
  • No web/ftp server installed. I can't mess with one of the boxes, so that's a no-go right now. Seems like Slow SFTP, Inc. just fixed it (I had a ticket open). I'll give an update after they tell me what they did.
    – Jeff
    Commented Jun 19, 2013 at 14:13
  • Different datacenters = different routing path. It's possibly the cause.
    – Nathan C
    Commented Jun 19, 2013 at 14:23
  • From support, "The number one factor that effects transfer rates is routing problems." So is my routing path to Slow SFTP, Inc. different just a few minutes after opening the ticket? I'll leave this question up just in case someone has any other ideas. @NathanC, Nice.
    – Jeff
    Commented Jun 19, 2013 at 14:27

2 Answers 2

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Routing can play a big part in speeds. As seen in the comments the datacenter likely had a bad route and swapped it when performance was suffering.

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The two companies can very well limit the upstream/downstream transfer speed with packet shapers. And most likely they do, especially if they're hosting companies. You only have a certain amount of upload bandwidth and a certain amount of download bandwidth. Plus, some hosting companies also meter the actual amount of transferred data, and after a certain threshold they "cut" your speed to a lower limit.

And to precisely address the main point in your question, YES, they can throttle traffic to/from your server (or virtual server) regardless of the port, they can set global limits per-machine, per port-group, or even per-service-type if they have a content-inspection capable firewall.

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