Path: utzoo!attcan!uunet!samsung!sol.ctr.columbia.edu!cica!iuvax!purdue!bu.edu!buit13!kwe
From: kwe@buit13.bu.edu (Kent England)
Newsgroups: comp.dcom.lans
Subject: Re: FDDI vs HPPI [was FDDI over copper]
Summary: They aren't really comparable
Message-ID: <53312@bu.edu.bu.edu>
Date: 5 Mar 90 14:50:55 GMT
References: <1990Feb28.105322.4274@hellgate.utah.edu> <549@sword.bellcore.com> <1990Mar3.224014.26968@hellgate.utah.edu> <21184@bcsaic.UUCP>
Sender: news@bu.edu.bu.edu
Reply-To: kwe@buit13.bu.edu (Kent England)
Followup-To: comp.dcom.lans
Organization: Boston U. Information Technology
Lines: 30

In article <21184@bcsaic.UUCP> carroll@bcsaic.UUCP (Jeff Carroll) writes:
>	Related question: how does FDDI compare, cost-wise, to HPPI?
>
	As I understand it, HPPI has a 75 meter limit on coax media.
I am not aware of any other media options.  (I am sure someone will
enlighten us if there are options.)  Remember, HPPI is warmed-over
HSC, a mainframe-to-mainframe interconnect standard.

	While FDDI started out as a machine room interoperable
interconnect standard, it left those kind of media and signaling
limitations behind when it decided to follow Pronet-80.  FDDI is
limited to fiber, which means that you can't substitute cheaper media
and trade-off distance and stay within the spec.  (That is one of the
things I like about Pronet-80; you have some media choices when the
fiber optic interface is outboard of the node.)

	Therefore, there is no comparison between FDDI and HPPI except
in the machine room definition of "local area".  HPPI is extremely
local (like a bus) and FDDI is nearly a WAN (will be a WAN when
someone does it).

	But, I imagine that if FDDI is not already cheaper, it will be
soon.  Remember, the cost of a proprietary interface is directly
related to the cost of the machine being interfaced.  (England's 12th
law of successful marketing to captive communities.)  The extension to
interoperable standard interfaces is slightly modified to include a
deflation factor based on the cost of the cheapest machine with a
standard interface.  So, FDDI wins at the moment.   :-)

	Kent England, Boston University