Tim Daniels ([log in to unmask]) wrote:
: I am in the process of working on a mosaic site which will be used to
: help students design virtual museums.  In talking with the campus
: internet guru he explained to me that my machine, which is off campus will
: be slow because one of the cable's which connects the machine to the main
: unix service is not fiber optic cable.  It seems that if at any point
: along the line the connection is not fiber optic the whole transfer
: process is slowed down. I just thought I would put that out for what it's
: worth.
: Tim Daniels
: TD6560@[log in to unmask]
 
For the interested: the speed of the world wide web, or any network
really, is dependent on two factors: data rate, and latency.
 
Data-rate is the speed data can move through a particular medium. Media
include copper wire (as in your phone line), coaxial cable (as in an
ethernet network or your cable TV hookup), or fiber optic cable, to name
a few. The wire connecting your phone to the world is usually copper and
of a grade to support your standard modem rates: 2400,9600,14400,24400
bits/sec. A bit is one piece of information: 1 or 0, on or off, +5volts
or 0volts. The wire in many networks is can be similar to phone wire (but
of a higher grade) or can be coxial. These will support up to 10mbits/sec
(10million bits/sec) data rates theoretically, but in practice get
between 1-3mbits/sec. Soon, Unsheilded Twisted Pair, or UTP, the stuff
that is like phone cable only much better, will support 100mbits/sec.
This will be very good. Fiber Optic is capable of even greater data rates
than that and can move many signals at once across the same cable.
 
Latency is the time between a message being sent and a message being
recieved across a network. This is affected not only by the medium in
use, but also by the way a message is "packaged", or the protocol used to
pass messages.
 
Mosaic access to the World Wide Web is an information rich feature of the
internet and requires aconnection providing high sustained data rates as
well as computer with above average graphics capabilities. (But not that
high above average). A single graphic image at a medium
resolution(say 160x180dpi) and 256 colors to appear on your screen would
require 28000bytes of data to be transferred across the net to your
computer. If your at a data rate of 14,400bits/sec, you'll need about 16
seconds for that data to show up on your machine (without any latency)
and another second or so for the computer to turn it into an image on your
screen.  If your perusing an online image bank or museum, this could get
tiring.
 
The above example is for 14400 baud modem. The access would imporve
dramatically when going directly through a medium with higher data rates
( like fiber optic, or UTP). Or using a modem with 24400baud capability.
 
 
Final conclusion: if it's graphical, it's a big CPU and bandwidth
consumer. A lot of information needs to flow fast and then be
manipulated even faster to experience any kind of fluid operations when
dealing with graphic interfaces.
 
 
 
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____________________________
Ed McLaughlin              |
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