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From: michaels@hplabsc.UUCP (Robert Michaels)
Newsgroups: comp.dcom.lans
Subject: Re: request for broadband info
Message-ID: <1953@hplabsc.UUCP>
Date: Sat, 6-Jun-87 04:42:27 EDT
Article-I.D.: hplabsc.1953
Posted: Sat Jun  6 04:42:27 1987
Date-Received: Wed, 10-Jun-87 03:22:30 EDT
References: <4663@columbia.UUCP> <12471@topaz.rutgers.edu>
Organization: Hewlett-Packard Laboratories
Lines: 30
Keywords: broadband
Summary: our experience

In article <12471@topaz.rutgers.edu>, ron@topaz.rutgers.edu (Ron Natalie) writes:
> 
> I'd be interested in hearing other peoples experiences.  I know that
> the following people are bridging ethernets on their Broadband network:
> 
We have been using Ungermann-Bass buffered repeaters on our network. These
are similar to the BRIDGE box in that it only does 5 Mbits in a 6 Mhz channel.
So, it simply buffers incoming traffic on the 10Mbit baseband side into
a 256K buffer for retranssmission on the broadband. It will work with
most any translator (we use a 3M) and it is frequency agile. We are using
8 units on a system which spans about 3 miles. To reduce the possiblity
of overloading the repeaters we isolate them from the baseband ethernets
with IP gateways. This makes the broadband logically a subnet of only 
gateways and from measurements I have made this has quite an effect
on total utilzation.

The Ungermann-Bass repeaters cost around $3800 each. I have found them
to be very reliable, we have yet to have one fail. Our cable system also
supports several video channels, some 9.6 Zeta modems, and some Applitek
terminal concentrators. From what I can tell the UB repeaters do not effect
nor  are effected by the other equipment.

Ron, I'm curious about your experience with the Chipcomm stuff. I read
that it requires 18Mhz bandwidth. Do you need guard bands in addition
to that? Also, have you tried using their newly announced modems which
only require 12Mhz bandwidth?


Robert Michaels
HP Labs