[CentOS] Inquiry:External USB modem and Remote PC Access?

Les Mikesell lesmikesell at gmail.com
Tue Oct 27 17:55:41 UTC 2009


Todd Denniston wrote:
> John R Pierce wrote, On 10/27/2009 02:42 AM:
>> GUI over a 28k dialup?  ouch.      there's no network connection at this 
>> remote site?   its going to be really really slow over dialup.  I'm 
>> talking minutes to paint a screen at 2-3kbyte/sec serial speeds (a 
>> 1280x1024 24bit desktop is 3.6 million bytes).     use a really simple 
>> theme on the desktop with no shaded borders, no backgroun graphics 
>> ('wallpaper'), etc.    Sending a single full screen 1280x1024 
>> photographic image could take a half hour or more.
>>
> 
> You Kids and your full desktop hosted back...
> back in the day I worked with individual applications across a 9.6kbps connection, and yes it was 
> slow and had a bit of lag, but it worked well enough to use xemacs and mozilla across.  Also when 
> hosting the application back, you are not transferring all the pixels, but only the X commands to 
> draw them, so unless you are running a picture editor/viewer (such as gimp) then a lot less than 
> your 3.6 million bytes per 1280X1024x24bit will be used.  Granted, running the gimp full screen 
> across such a link would be a near insane thing.
> 
> I was much happier when I discovered `ssh -C` (in combination with X or Y), to host the apps back. 
> There was still a little lag but overall it was _much_ snappier.
> 
> I have yet to use X across a vnc or with freenx so I can't comment on how they compare to `ssh -C`.

The problem with remote X is that it waits until each X command 
completes before doing anything else.  Just opening a new window can 
take several minutes over a slow link.  Vnc isn't particularly 
efficient, but at least it lets X update at full speed in a frame buffer 
and decouples the remote redraws. Freenx/nx are much more intelligent, 
acting as a proxy/cache for X on both ends of the connection so it 
doesn't force the program to wait and it reuses anything it can that has 
already been sent when things move around.

But, it's about 25 years too late to find anyone who still knows how to 
use modems and serial connections.   Unix pre-dates tcp networking and 
had very usable tools which Linux has inherited, but there are good 
reasons why they aren't used much these days.

-- 
    Les Mikesell
      lesmikesell at gmail.com




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