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From: jmg@cernvax.UUCP
Newsgroups: net.lan
Subject: Re: Will the real DELNI restriction please stand up?
Message-ID: <173@cernvax.UUCP>
Date: Wed, 12-Jun-85 10:52:57 EDT
Article-I.D.: cernvax.173
Posted: Wed Jun 12 10:52:57 1985
Date-Received: Fri, 14-Jun-85 05:06:28 EDT
References: <2581@decwrl.UUCP> <2740001@acf4.UUCP>
Reply-To: jmg@cernvax.UUCP (Mike Gerard, DD Division, CERN.)
Organization: CERN, Geneva/Switzerland
Lines: 30

In article <2740001@acf4.UUCP> russell@acf4.UUCP (Bill Russell) writes:
>Quoting from the DEC "1985 April to June Edition of 'Networks & Communications
>Buyer`s Guide' pages 4.20-4.21 (Configuration Guidelines):
>
>The DELNI hierarchical stand-alone configuration (Fig 4.19) supports a
>combination of DELNIs and devices using standard Ethernet transceiver cables
>up to 50 meters (164 feet) away for other DELNI and between 40 and 45 meters
>(131.2 & 147.6 feet) depending on the communications controller.

The DELNI Installation/Owners manual  starts by saying that a DELNI allows
work stations "over a 20 meter (65 foot) square". Then, later, it says
"NOTE: Check for any cable length restrictions by referring to the
appropriate installation manual for each station's ETHERNET controller.

Can you imagine what happens when you want to use a non-DEC controller,
and you ask the manufacturer of the controller what are the length
restrictions? I have tried it, and the answer is non-informative.

Also, DEC say that you should not hang a DELNI on a DELNI on a real
ETHERNET. Of course, it works, and if we had the real DELNI specs we
could perhaps see why. Maybe one can hang them n-deep (we have enough
here to try small integers for n).

My feeling is that we want a technical specification for a DELNI. Neither
a buyer's guide (trying to get you to buy it) nor an installation
manual (when you already have it) is the correct place for such a spec.

p.s. After the various remarks about troubles with DELNIs I shall test
an equivalent product from another manufacturer. Maybe the grass in the
next field really will be greener.