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From: pat@hprnd.HP.COM (Pat Thaler)
Newsgroups: comp.dcom.lans
Subject: Re: Ethernet over twisted pair: a summary of the "whys"
Message-ID: <2230039@hprnd.HP.COM>
Date: 5 Dec 89 18:36:05 GMT
References: <4686@blake.acs.washington.edu>
Organization: HP Roseville Networks Division
Lines: 48

> 
> At the risk of beating this subject to death, I would like to point out
> that you can use the exact same configuration using thinnet.  Run one
> thinnet to each device and connect them all to standard thinnet multiport
> repeaters.  There are even some advantages to doing it this way:
> 
>  1) longer distance per run
>  2) lower cost - the twisted pair equipment is alot more expensive
>     when your devices have built in thinnet xcvrs (as most now do)
>     You can but an 8 port thinnet multiport for <$2K and 4 port <$1.4K

You can buy a 12 port twisted pair hub for <$2K.  More devices with
built-in twisted-pair ports are becoming available.  As integrated
transceiver and repeater chips become available, I expect prices to drop. 

>  3) more noise immunity/less RF

Bit error rate and RF is about the same for the two media.  The distance
of twisted-pair was limited to 100 m in order to attain the 1 in 
10**9 BER.  Of course if you are in a very noisy area, you may be
better off with fiber than with either electrical media.  Another
option is to run over twisted-pair cable with an overall shield.  This
is a truely shielded cable as opposed to coax where the shield is
used for signal return path.

>  4) you can daisy chain off another device if a quickie install is needed
> 
> Of course, there are disadvantages to thinnet as well.  Two that are
> relevant to the star topology are:
> 
>  1) thinnet multiports are rather stupid about disconnecting screwed up
>     segments, which can result in a hung network.
>  2) thinnet patch panels/closet hardware/wall plates/etc are harder to come
>     by and more expensive than telco type stuff.
> 
> Randy
> -- 
> Randy Smith
> wsmith@umn-cs.cs.umn.edu
> ...!rutgers!umn-cs!wsmith
> ----------
There are certainly useful applications for thinnet because of its
greater distance and its ability to daisy-chain.  Twisted-pair with
a fiber or coax backbone works well in a lot of office environments.
I have worked on the development of both 10BASE-T and 10BASE2.  They
are not mutually exclusive, some LANs should use both.

Pat Thaler