VNC Bandwidth use

[James [Wez] Weatherall]

On Fri, 13 Nov 1998, Carroll, Patrick S wrote:

> Hello All,
> 
> Has anyone done any testing to see how much "average" bandwidth VNC takes up
> on a network?

The VNC protocol is inherently bandwidth-adaptive - if the bandwidth is
low then more updates will be batched together to produce lower overall
bandwidth.  At peak, VNC will generally use as much bandwidth as is
available, while when the display isn't changing, no bandwidth will be
required except for mouse, keyboard or clipboard events, which are
generally tiny.

> Will there be any features to allow 1,2,4 bit transmissions for extremely
> low bandwidth connections?

It doesn't look likely - the decrease in bandwidth requirements would be
fairly small, since for most encodings, the actual pixel data isn't the
predominant part of the update, and in addition, the event of zlib
compression will make the difference between 32, 16, 8 and <=4 bit smaller
still.  Using less that 8 bits per pixel would also significantly
complicate the on-the-wire protocol and require extra, probably quite
slow, munging code to pack the pixel values.

Cheers,

James "Wez" Weatherall
--
Olivetti & Oracle Research Laboratory, Cambridge, UK - Tel : 343000
Laboratory for Communications Engineering, Cambridge - Tel : -


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