[486] in linux-net channel archive
Re: plip progress
daemon@ATHENA.MIT.EDU (Martin Kraemer)
Wed Jun 14 07:04:13 1995
To: m-ke0082@SPARKY.CS.NYU.EDU (Ken Estes)
Date: Wed, 14 Jun 1995 10:52:40 +0200 (MDT)
From: "Martin Kraemer" <Martin.Kraemer@mch.sni.de>
Cc: linux-net@vger.rutgers.edu (Linux Network Channel)
In-Reply-To: <9506140445.AA28232@SPARKY.CS.NYU.EDU> from "Ken Estes" at Jun 14, 95 00:45:57 am
Ken Estes wrote...
>
> could I wire together a bunch of plip cables and run several (3-10)
> machines on a cheap network?
> [...], but is it feasible?
Yes, but not in a bus topology like this
+-----+ +-----+
|hostA| |hostC|
+-----+ +-----+
I I
...=======+=======+=======+====...
I
+-----+
|hostB|
+-----+
Because when no host transmits, then the cable is not "idle" (you'd need a
third electric state beside "on" and "off", you call that tri-state
drivers; Not available on centronics port). [Instead, the different levels
on the output lines of all hosts would result in a short circuit, you
might blow up the parallel interface chips]
But what you can of course do is this (how much is a cheap printer card?
how much do you pay for a cheap arc/ether card? is it worth the
performance penalty?):
+-----+ +-----+
|hostA| |hostC|
+-----+ +-----+
I I I I
...======+ +=====+ +=====+ +===...
I I
+-----+
|hostB|
+-----+
that is, give every host _two_ parallel ports, and forward packets from,
e.g., hostA to hostC on hostB. This makes configuration less simple of
course, because you have to define all routes manually (is this right? or
can I have _two_ default routes and hope that either of the two interfaces
will succeed in reaching the destination?). Or use dynamic routing via
gated (or routed?).
What I would ask myself in your situation is this: if you ever plan to use
more than two hosts, is the added complexity and low performance worth the
price? (2 * $10 for centronics cards, or $30 for ethernet?)
Martin
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