Running SSH X forwarded session from my Ubuntu 12LTS client to a SLES server results in very slow(seconds per mouse click) GUI app(on the server) performance.

Using a windows client from the same LAN with Putty and XMing to SSH to the same server hosted application is blazing fast(instantaneous).

Likewise, SSH -X from other SLES machines to the same server hosted application is very fast.

I have tried numerous combinations of ssh parameters(listed below) with no effect on performance. The Ubuntu client is painfully slow while PuTTY/XMing are very fast.

-o GSSAPIAuthentication no
-c blowfish-cbc

UseDNS no -- on the servers sshd_config
  • Post a picture of your speedtest results here. I think it may be an internet issue with Ubuntu. Do one in Windows as well so we may compare the two. – Zzzach... Mar 26 '14 at 3:10
  • @user241527: Did you solve this problem in the mean time? I have a similar problem: I used to work remotely from my laptop to my desktop, running Ubuntu 12.04 and 10.04 respectively, and connected through my home network. After I have bought a new desktop and upgraded to 12.04, I can barely work remotely: sometimes a window will just freeze for half a minute or so. – Giorgio Apr 20 '14 at 16:05

XMing doesn't support the X11 security protocol, causing it to default to trusted forwarding. It's possible SLES has ForwardX11Trusted enabled, while Ubuntu doesn't. That option allows the remote X client to make trusted calls on the local X server, which is a security risk if you don't trust the server, but can provide a substantial performance boost if you do.

You can use ssh -Y to connect with trusted X11 forwarding or set the ForwardX11Trusted option in your ssh client config.

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