Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.1 6/24/83; site deepthot.UUCP
Path: utzoo!watmath!deepthot!julian
From: julian@deepthot.UUCP (Julian Davies)
Newsgroups: net.lan
Subject: Re: cheapernet?
Message-ID: <323@deepthot.UUCP>
Date: Fri, 15-Jun-84 12:25:56 EDT
Article-I.D.: deepthot.323
Posted: Fri Jun 15 12:25:56 1984
Date-Received: Sat, 16-Jun-84 06:24:29 EDT
References: <1259@sun.uucp>
Organization: UWO CS, London Canada
Lines: 21

At a presentation here by 3Com, it was explained that the 'thin cable'
is lossier by a factor of 3, not 2, so that 1 foot of thin cable
should be counted as 3 feet of thick-cable equivalent.  A system with
thick cable and only 3Com external transceivers can go to 1000m, so a
thin cable segment can only go to 300m.  However, the two can be
combined in one 'segment' up to the 1000m "thick equivalent", provided
there are only a few thickness transitions.
  Thick cable with less controlled transceivers is limited to 500m,
they said.

Another thing I learned and hadn't appreciated before is that the
'repeater' joining two cable segments is a bit-level repeater, not a
frame-level buffering repeater, so there is an upper limit if 2500m
and two repeaters between any pair of transceivers in a single
network made from several segments.  and *that* limit 2500m includes
the connecting cables used at repeaters or in fibre-optic repeater
connections.
  one can go beyond that limit if a full-fledged gateway buffering and
retransmiting frames is used.
		Julian davies
		university of Western Ontario