Path: utzoo!utgpu!jarvis.csri.toronto.edu!clyde.concordia.ca!uunet!aplcen!uakari.primate.wisc.edu!ames!ncar!unmvax!ariel!dd
From: dd@ariel.unm.edu (dd)
Newsgroups: comp.dcom.lans
Subject: Re: Broadband Ethernet: What's out there?
Keywords: V2, Chipcom
Message-ID: <1173@ariel.unm.edu>
Date: 22 Dec 89 16:54:30 GMT
References: <2389@morticia.cme.nbs.gov>
Reply-To: dd@ariel.unm.edu.UUCP ()
Distribution: na
Organization: University of New Mexico, Albuquerque
Lines: 40

In article wallace@cme.nbs.gov (Evan Wallace) writes:
>[...]
>We now have some chipcom ethermodems front ended by DEC lanbridges
>in special service (supporting two diskless sun based CAD systems).
>Our experience when we expanded the user base on this channel was a
>catastrophic degradation of service.  These were by no means
>rigorous tests and their is no way to isolate the Lanbridges from
>the equation; however it does not inspire confidence in this
>technology.  

I may be mistaken, but I believe the Chipcom stuff is 10BROAD36
compliant.  That means that it performs as well as an Ethernet.
Period.  Well, almost period...

How long is your broadband?  The catastrophic performance
degradation may occur if your collision detection is not functioning
correctly, and the only mechanism I see for that is that you may not
be adhering to the maximum length specifications of 10BROAD36?

If this is the problem, you might actually want to go with something
that has a lower signalling rate, and a greater network radius (we
use UB buffered repeaters here, providing CSMA/CD 5 Mbps channels),
because you will actually get higher thruput out of this
configuration.  We have diskless and disked workstations separated
by the broadband system, but we have a company policy that paging
and swapping are not allowed over the broadband.  We experience some
less-than-optimal response, but no catastrophic collapse.

Anyway, vendors you might try:

   Ungermann Bass
   Lanex

But I really think Chipcom makes a very good product.

-- 
Don Doerner				dd@ariel.unm.edu
University of New Mexico CIRT
2701 Campus Blvd, NE
Albuquerque, NM, 87131			(505) 277-8036