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From: neal@weitek.UUCP (Neal Bedard)
Newsgroups: net.med
Subject: Re: ethernet in a hospital
Message-ID: <357@weitek.UUCP>
Date: Mon, 30-Dec-85 15:26:54 EST
Article-I.D.: weitek.357
Posted: Mon Dec 30 15:26:54 1985
Date-Received: Sun, 5-Jan-86 02:02:35 EST
References: <188@bigtuna.UUCP> <1895@saber.UUCP> <623@osiris.UUCP> <8192@ucla-cs.ARPA>
Distribution: net
Organization: Weitek Corporation, Sunnyvale
Lines: 35
Keywords: ethernet, reliability

In article <8192@ucla-cs.ARPA>, dgc@ucla-cs.UUCP writes:
> -------
> I think the various notes about ethernets miss the real question:
> 
>     Just how reliable are ethernets? [...]
> 
> To explain the last question further:  Ethernets and other
> non-redundant, non-star nets have the feature that ANYone on the net,
> ANYwhere can at ANYtime take down the entire system, and with very
> little effort.  This has happened at ethernet installations.
> 
> What, for example, if the technician who installs "vampires" makes a
> mistake and, while installing one, shorts the cable just while the
> ethernet is being used to monitor some critical life support function?
> 

I think the poster already answered his own question - usually, anything so
critical is implemented with some sort of redundancy.

A similar problem arises with fire alarm/life safety equipment. The
answer here, too, is redundancy in the communications network, with fail-safe
i/o hardware (i.e., the network does not crash if say, the power fails at
one of the nodes.) Ethernet can be implemented in this way.

To answer the specific case that the poster outlined, I would tend to think
that the installation of a new `vampire' is something that would be a rare
occurence in a up-and-running system, and would probably be a scheduled
downtime sort of item. Further, situations where such critical remote telemetry
functions are used (as in ICU or CCU) probably would be carried on with the
usual sort of equipment anyway, and probably would not be served by Ethernet.
Thus, that paticular argument of the poster's is, in my estimation, moot.

-Neal
-- 
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