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RE: Problem with running X apps


Seems to me that on a reasonably fast LAN any slow down is going to be a function of the CPU "horsepower" at either end of the pipe, not the LAN bandwidth, since it's the processer which is doing the {de|en}cryption.

On the other hand, a narrow band connection (like 56k dialup) might actually benefit from the encyption (that is, if my assumption that encyption also compresses the packets is correct).

I observe in my office what I think is a "moderate" slowdown when using an ssh connection vs. an unencrypted connection. (For the record I run Cygwin/XFree on my Thinkpad w/ a 700MHz Pentium III, 256MB SDRAM, and Windows 2000; and connect to my RS/6000 Model 44P-170 w/ a 333MHZ POWER3 processor, 2GB SDRAM, and AIX4.3 over 100BaseT full-duplex Ethernet.)

Since I'm behind a corporate firewall, I'm not particularly concerned about who is looking at my X traffic, or what they might see, so I don't bother with ssh.

From: "Kerry Sanders" <ksanders@mindspring.com>
Reply-To: cygwin-xfree@cygwin.com
To: <cygwin-xfree@cygwin.com>
Subject: RE: Problem with running X apps
Date: Mon, 5 Aug 2002 18:50:23 -0500

Thanks Thomas.  This is the same thing that Jim posted earlier.

What I needed was the -X on the ssh command.  However, does the
encryption really slow stuff down that much?  I is really slow running X
apps like KDE, etc. over my 100 Base-T network.


-----Original Message-----
First, I would recommend against running XWin directly.  Use the
provided
startxwin.bat batch file instead and then run the ssh command from an
xterm.

However, if you REALLY want to do it this way, you need to set the
DISPLAY
variable FIRST, then launch XWin, then run ssh with X forwarding turned
on:

cygwin> export DISPLAY=locahostname:0
cygwin> XWin <options> &
cygwin> ssh -X -l remoteusername remotehostname

Once logged into the remote host, you can start running your Xclients
right
way.  No need to set the DISPLAY variable yourself (or run xhost).  Ssh
will
have already taken care of all of that.  In fact, setting the DISPLAY
variable as you describe below CIRCUMVENTS THE SSH CONNECTION ENTIRELY
and
sends your XWindows traffic unencrypted!

By the way, if the file .Xauthority exists in your home directory on
localhostname, it might cause problems.  If you find you are getting
errors
that refer to "MIT-MAGIC-COOKIE", then delete the .Xauthority file and
try
again.




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