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From: chimiak@umbc3.UMBC.EDU (Mr. William J. Chimiak )
Newsgroups: comp.dcom.lans
Subject: Re: Ethernet alternative needed
Message-ID: <2406@umbc3.UMBC.EDU>
Date: 14 Oct 89 16:48:37 GMT
References: <9478@zodiac.ADS.COM>
Reply-To: chimiak@umbc3.umbc.edu.UMBC.EDU (Mr. William J. Chimiak (MMA))
Distribution: na
Organization: University of Maryland, Baltimore County
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In Article 3780 of comp.dcom.lans:
John L. Shelton writes

>We are running out of bandwidth on several of our seven ethernet
>subnets, and are considering the options.  The quick-and-dirty option
>is to add more subnets, and upgrade our Cisco gateway.  I'm not
>convinced this is a good long-range solution, however.
>
>I think a given is that we will not upgrade 100+ CPUs to FDDI; we can
>assume that all CPUs have Ethernet hardware interface, and will
>continue to have them for at least 2 years.

>I thought I had run across a network product last year that implements
>ethernet over fiber optic, but provides 100mb/s bandwidth.  You attach
>to the fiber with interconnects that support up to 8 ethernet-based
>hosts (sort of like a DELNI), and the box gets the packets going on
>the fiber at very high speed.  WHile any one host is limited to 10mb/s
>performance (ethernet limit), the aggregate network capacity is much
>higher.

>Can anyone give pointers to this (perhaps hypothetical) network
>system?  Thanks.

It seems to me that you are just implementing an FDDI concentrator.  Each
FDDI concentrator can then be placed in a ring.  The LLCs of IEEE 802.3 and
FDDI are the same but admittedly the drivers will be quite different.  If
the ethernet bandwidths and concomittent delays are satisfactory for your
applications, an FDDI concentrator scheme might be the way to go while
maintaining compliance with a strong standard so upward system evolution
would be less painful.  For new systems coming on line, be sure to do cost
and performance trade-offs between FDDI and ethernet before choosing either
one.

For further thoughts on FDDI/Ethernet hybrid networks, see the Data
Communications issue on designing FDDI networks - it is quite good.  I
think it appeared June 1989.