[K12OSN] VNCViewer and speed of refresh

[Jeff Kinz]

On Wed, Jul 14, 2004 at 10:29:07AM -0500, Les Mikesell wrote:
> Errr..., no.  The complaint was about VNC speed over a low bandwidth
> link.  Running straight X is going to be much worse. VNC can skip

Errr..., no.

I have used X and TightVNC over the same link, and where VNC was doing
the typical "4-10 seconds" per screen redraw, X was mostly keeping up
with real time.

X-windows works much better over low bandwidth links than VNC.

Why?   Raw Data vs. Abstraction

Remote X-windows doesn't send any graphical information over the link.
It sends only events like "Close Window 27" to the X-server at your
display.

VNC, on the other hand, has to send an entire frame buffer of raster    
data (hopefully optimized), resulting in transfers of thousands
or tens of thousands of bytes where X sends only twenty or thirty bytes.
Even with intelligently optimized 'skipping" of redraw data remote frame
buffer systems like VNC have to send much more information over the
network.

If VNC is more efficient, then we should use it instead of an X server
for the thin clients right ?  Its certainly smaller than an X-Server.

(( Historical Note - VNC was invented by some folks at Olivetti in
the UK (Later became part of AT&T). Its designed and intended use was
to permit people using very small systems, incapable of running an
"X-server", to access a machine running X-Windows.

See top right corner of page 3 of:
http://www-lce.eng.cam.ac.uk/publications/files/tr.98.1.pdf  ))

-- 
Linux and Open Source.  The New Base.  

Now All your base belongs to you, for free.

Jeff Kinz, Emergent Research, Hudson, MA.