I have remote server with Ubuntu Linux and I want to establish SSH tunnel with this server from Windows machine using PuTTY(plink). I have to use this method for getting access to some service on this server, because firewall is blocking all ports on this server except 22 ssh port. But speed of connection over SSH tunnel is VERY SLOW. I have checked speed using iperf tool.

Here is results of using iperf without SSH tunnel:

[  5] local <remote_server_ip> port 5001 connected with <my_internet_ip> port 11154
[ ID] Interval       Transfer     Bandwidth
[  5]  0.0-10.4 sec  5.12 MBytes  4.13 Mbits/sec

And it is results of using iperf over SSH tunnel:

[  4] local port 5001 connected with port 38231
[ ID] Interval       Transfer     Bandwidth
[  4]  0.0-15.2 sec   896 KBytes   484 Kbits/sec

Speed is really different. How is it possible? What should I do to fix it?

  • What's the latency between the two hosts? – Cakemox Aug 8 '13 at 11:01
  • 1
    Try adding a "-C" to your ssh command line. That enables compression so it may increase your CPU load. – Travis Hegner Aug 8 '13 at 14:01
  • I'd look closely at your SSH options. Perhaps you can choose a faster encryption algorithm, for example. – David Schwartz Jul 2 '14 at 22:37

Probably it's worth a read of this "Why TCP over TCP is a bad idea", it would be better to use a VPN than to rely on SSH for anything more than throw away tunnels.

Admittedly, that's a lot slower than I would have expected, even from an SSH tunnel. Perhaps you need to tune your SSH options.

  • I know about great overhead when we are using TCP over TCP, but even we use this method - connection still userfull. I have some experience with using OpenVPN over TCP and yes with this way connection is slower. But not so SLOW like in my example. So I guess it is something wrong in my sshd setting. But what exact? – John Green Aug 8 '13 at 9:04

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