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From: ernie@nucsrl.UUCP (Ernest Woodward)
Newsgroups: comp.dcom.modems
Subject: Re: Codenoll Fiber modems
Message-ID: <3890001@nucsrl.UUCP>
Date: Thu, 22-Oct-87 08:47:20 EST
Article-I.D.: nucsrl.3890001
Posted: Thu Oct 22 08:47:20 1987
Date-Received: Sun, 25-Oct-87 17:25:51 EST
References: <1100@julian.UWO.CDN>
Organization: Northwestern U, Evanston IL, USA
Lines: 43


> Xref: chinet comp.dcom.modems:946 comp.protocols.tcp-ip:1389
> 
> We put a pair of FiberCom Whisperlan transcievers into operation
> recently.  These are running over about 2000' of fiber between
> two buildings here at Rutgers.  One end is plugged directly into
> an IP/DECNET Gateway (CISCO) and the other is plugged into a
> TCP multiport box which intern has the central gateways (a collection
> of several CISCO boxes and a VAX 750).  The boxes cost about $850

	I was curious about the TCP multiport boxes. I am aware of
several ETHERNET multiport boxes like the DEC DELNI, EXCELAN fan-out box,
HP multiport, etc. The reason for pointing this out, is that I
currently have an ETHERNET multiport box connected to a CODENOLL 3030A
and believe that one could connect several units with two fiber modems
and two ETHERNET mutliport boxes, or as in my network, connect several
units to one branch of the fiber optic star coupler via one 3030A.

> and we haven't had any problem with them.  They have the advantage
> (unlike the Codenol, I believe) of allowing multiple units to be
> ringed.  That is, you can connect three or more of these boxes
> together using fiber rather than using them as a point to point
> link.  This ends up saving you the price and the overhead of a
> board in the CISCO box in the middle of the net having to copy
> packets bridging accross the two fiber segments.

	I believe that the CISCO boxes allow for one possible network
configuration based on internetworking. It is possible to purchase
CODENOLL bridge equipment that could connect ETHERNET segments via fiber
links, or it is possible to connect as suggested above, i.e. two fiber
modems and an ETHERNET multiport box. The multiport boxes require that
all the units be within a 45 meter radius of the multiport box. I believe
that either CODENOLL or FiberCom or maybe even Siecor ( DEC and Siecor were
once selling a system similar to CODENOLL but used different collision
detection schemes) offer equivalent opportunities to design the inter-
connection with one of three possible methods; gateway, coax to fiber
bridge, or multiport to modem. I thinks it will be boil down to a simple
cost comparison of equipment prices and features.

Sincerely,
Ernie Woodward
Academic Computing and Network Services
Northwestern University