Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!purdue!haven!mimsy!chris
From: chris@mimsy.UUCP (Chris Torek)
Newsgroups: comp.dcom.lans
Subject: Re: high speed networking between buildings
Message-ID: <19661@mimsy.UUCP>
Date: 19 Sep 89 08:30:38 GMT
References: <4574@ursa-major.SPDCC.COM> <337@ai.etl.army.mil> <4609@ursa-major.SPDCC.COM>
Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742
Lines: 45

>In article <337@ai.etl.army.mil> hoey@ai.etl.army.mil (Dan Hoey) writes:
>>But of course, in the words of Charles Hedrick, ``We do not recommend running
>>copper of any kind between buildings.  You can sometimes get away with it, but
>>it's asking for trouble.''

In article <4609@ursa-major.SPDCC.COM> eli@spdcc.COM (Steve Elias) writes:
>there are thousands of sites which run broadband and other coax
>between buildings with no problem.  many of them do run computer
>networks across such cables, as well!  many thousands more run
>cable TV channels across broadband cable between buildings...
>
>i'm not sure if 4 out of 5 networking cats would agree with
>Mr. Hedrick's recommendation.

I think they would---certainly so if they had experience with both
broadband and fiber:

	a) broadband is slow.

You can get 10 MB/s by using three broadband channels (TV channel
bandwidth is ~4.5 MB/s), as in DEC's product(s?).  You can buy
80 MB/s off the shelf from Proteon.  (18 TV channels anyone? :-) )

	b) broadband requires maintenance.

A large broadband cable plant (such as the one at the University of
Maryland) requires a full-time person simply to go around and adjust
head ends.  (If you have ever wondered why it is that your cable TV
reception improves every time the line is restored after it gets zapped
by lightning, it is because the average cable TV plant does not bother
adjusting their repeaters.  This causes some minor picture degredation
on a TV set, but similar `tuneup problems' are pretty much fatal to
networking.)

By and large, one pulls fiber, plugs it in, and forgets about it.
Lightning strikes do not require replacing transceivers, etc.

I am not up on the current costs for new installations of each.  It
does seem obvious (which does not make it necessarily true) that it
should cost less to use existing broadband facilities than to run new
fiber optic lines, at least initially (maintenance costs add up fast).
But fiber is much nicer, and should be cheaper in the long run.
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163)
Domain:	chris@mimsy.umd.edu	Path:	uunet!mimsy!chris