VNCviewer 4bit 2bit for very slow connection.

[Jonathan Morton]

>The problem in not the modem,I use 56K modem, but the net.
>In Italy durind
>the day internet is very slow specially when the
>two computer are connected
>in internet with two different providers.
>Sometimes the viewer end for itself.

I think I see what you mean.  It also defines the problem a little more
clearly, thank you.  I had in my mind's eye one of those palmtops with
little serial links or GSM cellphone connections...

Anyway, I think the issue here might not actually be bandwidth (which is
what encoding and bit-depth helps) but latency.  Run a 'ping' utility
between the two machines and you'll probably see what I mean - a ping time
above 500ms will make for a very slow VNC experience no matter how much
actual bandwidth is available.  VNC traffic, apart from sustained streams
caused by a large update, tends to be sent in small chunks which wouldn't
take long but for the latency.

Believe me, I have run VNC across T1 and cable lines which were separated
by a congested router - there was no problem with bandwidth (updates
arrived very quickly, even for large screen areas) but the latency was
horrible - the user sitting at the machine was typing into an IRC window
and I was seeing the text on my local IRC screen before I saw the letters
marching across his inputline.

In my tests with the 14.4k modem, the server (with the modem) was on a
reasonable ISP with good connectivity and the client was connected to the
JANet - very low latency, in the 100ms range - and apart from large
updates, which were affected by bandwidth, the speed of the connection was
unhampered due to the low latency.

Unfortunately, there is very very little we can do about latency.  The
client has to send mouse updates to the server, which then has to send
screen data back.  This is a round trip which on a reasonable net is
acceptable but on a slow net becomes intolerable - as you are noticing.
The only solution is to wait for Italy to upgrade it's networking...

Of course, if you find for some reason that ping times are good but
bandwidth is poor... then it is time to revisit the encoding question :).

--------------------------------------------------------------
from:     Jonathan "Chromatix" Morton
mail:     chromi "at" cyberspace.org  (not for attachments)
uni-mail: j.d.morton "at" lancaster.ac.uk

The key to knowledge is not to rely on people to teach you it.
--------------------------------------------------------------
Contributing to the VNC Project - http://www.uk.research.att.com/vnc/
Macintosh VNCserver v3.3.2 beta2.2 now posted at:
	http://chromatix.autistics.org/vnc/



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