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From: velasco%beowulf@ucsd.edu (Gabriel Velasco)
Newsgroups: sci.virtual-worlds
Subject: Re: telecommunications
Message-ID: <2227@milton.acs.washington.edu>
Date: 2 Mar 90 09:33:40 GMT
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Reply-To: velasco%beowulf@ucsd.edu (Gabriel Velasco)
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brandonl%amadeus.wr.tek.com@RELAY.CS.NET (Brandon Lovested) writes:

>The problem of bandwidth will be partially alleviated when high
>speed communications links like ISDN, and better yet, FDDI will
>be adopted.  The speed (>1 Gigahertz) and bandwidth of these links
>could possibly allow massive VR communication environments.

>That's what the people behind the curtains are working on as we speak...

	ISDN is actually a description of an interface to a carrier.  It says
nothing about how the information will be transported once it has left the
customers equipment.  ISDN offers various types of services which are
combinations of several channel types.  The highest bandwidth channel type
which has been standardized, so far, is only 1920 kbps.  You could put 521 of
these together to get one 1 Gbps channel.
	FDDI is a Token-Ring type network operating at 100 Mbps.  There are
actually two rings with data traveling in opposite directions.  The second ring
is intended to be for crash-proofing the system.  If a site goes down, its ends
can be connected and you can have one big ring until the site is fixed.  You
could, however, use the two rings at the same time and get speeds of about 200
Mbps.  FDDI is only intended to run over distances of up to 200 km which really
makes it suitable as a Metropolitan Area Network not as a replacement for the
ARPANET.  They are working on a >1 Gbps ARPA internet which will hopefully be
up by the turn of the century.
	Speed is usually measured in bits per second because that can vary
over a fixed number of hertz depending on the encoding scheme.  It (speed) is
roughly synonymous with bandwidth, however, because if you use the same
encoding scheme, you can transmit more bits per second on a higher bandwidth
channel.

                              ________________________________________________
 <>___,     /             /  | ... and he called out and said, "Gabriel, give |
 /___/ __  / _  __  ' _  /   | this man an understanding of the vision."      |
/\__/\(_/\/__)\/ (_/_(/_/|_  |_______________________________________Dan_8:16_|