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In article <1992Oct10.131926.1@elgr.epfl.ch>, grandjean@elgr.epfl.ch writes:
|>
|>     We are evaluating multiple ethernet segment  vs  FDDI.
|>

Assuming that you have reasonable adapters, FDDI will buy you a lot
more than 10 Ethernet segments connected by a switch; figure that you
only get 30 megabits out of your FDDI adapter (I'd call that a dog).
If there is no contention, then you'll move data at 3 times the rate
as you can on Ethernet.  If there is contention, you get the same total
data rate as if you had 10 Ethernet segments where the traffic was all
local; but if the traffic is all going thru a switch and optimally
balanced, then you'll need 20 Ethernet segments to get the same total
thruput as a single FDDI segment.

It's all simple queuing theory: a single k unit server is always better
than k single unit servers.  (Of course, the complex part of the theory
is dealing with the bottlenecks that every system ends up with because
life isn't as simple as theory needs life to be.)

|>Does anyone have experience with 30+ networked workstations with FDDI?
|>What are the issue on management and upgradability?

I don't have experience with workstations, but in testing 10+ `servers'
on FDDI, FDDI has its faults, ie., there is a lot more overhead than
when using proprietary interconnects (CI, DSSI), but the performance is
generally about equal and the flexibility and cost better.

|>Is there somewhere on the NET performance figure of such configuration
|>(DEC & SUN hardware)?

There was an article in the DEC Technical Journal that focused on FDDI
that reported on benchmarking the DECcontroller 700 on a DECstation 5000.
However, unless you have easy access to this journal, I don't think its
worth tracking down these days; it is getting rather dated.

|>
|>Thanks for anyone who can make the point clearer.
|>--
|>Daniel Grandjean, Swiss Federal Institute of Technology        __  __
|>Address:     EPFL SI-DGR, CH-1015 Lausanne, Switzerland       |  \/  |
|>E-mail:      grandjean@elgr.epfl.ch                           |o ()o _
|>Phone:       +41 21 693 27 24	(Central European Time)       |__/\__/
|>Fax:         +41 21 693 27 27                                    __
|>


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