Problem with running X apps

[Thomas Chadwick]

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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