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From: mccallum@opus.UUCP (Doug McCallum)
Newsgroups: net.lan,net.dcom
Subject: Re: ETHERNET on Broadband
Message-ID: <1270@opus.UUCP>
Date: Wed, 3-Jul-85 14:49:28 EDT
Article-I.D.: opus.1270
Posted: Wed Jul  3 14:49:28 1985
Date-Received: Sat, 6-Jul-85 10:40:37 EDT
References: <2926@decwrl.UUCP> <449@bu-cs.UUCP>, <1263@opus.UUCP> <454@bu-cs.UUCP>
Organization: NBI,Inc, Boulder CO
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Xref: watmath net.lan:900 net.dcom:1080

> Yes, I would like a black box that just snapped onto an ethernet cable
> and broadband tap and magically forwarded to another, remote box with
> the same connections, but I don't like the idea of 2 or 3 dedicated
> channels to do it. I also wonder exactly what gets forwarded (every
> packet? the DEC box certainly doesn't read IP packets.)  I guess for now
> I am using a couple of Vaxes as this 'black box'.

The DEC ethernet on broadband isn't a black box that forward packets, although
you could use the Vitalink box using baseband on oneside and broadband on
the other.  The DEC product is a broadband tranceiver that connects to an
ethetnet/802.3 controller on whatever type of system you have.  It even uses
the same drop cable as far as I can tell.  What gets put on the coax
is exactly the same bits that would go on the baseband coax.  It really is
a broadband implementation of 802.3 CSMA/CD at 10Mb/s.  It is being considered
as a new family member to the IEEE 802.3 family of access methods.

Given this form, there are no protocol dependencies.  You could run a mixture
of TCP/IP, XNS, DECNET, etc. over the same cable as you can do now with
the baseband implementation.  It requires no new hardware or software other than
what is needed to connect to the cable (ie tranceivers and a headend).

I intend this article to be informational only and not specifying a preference.
Both the U-B approach and the DEC approach have advantages and disadvantages.
Just to throw more confusion our, the Sytek network which IBM is using as
their PC network is a broadband network using an 802.3 compatible packet
format.  It only uses 1 CATV channel but operates at lower speed.  It needs
a new controller and tap since it uses a different scheme for encoding the
signal.