From: whiles@nswc.navy.mil (William Scott Hiles x1568)
Newsgroups: comp.dcom.lans.fddi
Subject: Re: Brands of Concentrators?
Date: 5 Nov 92 14:46:08 GMT
Article-I.D.: relay.1992Nov5.144608.19691
Reply-To: whiles@nswc.navy.mil
Organization: Naval Surface Warfare Center, Dahlgren Division

In article EBx@world.std.com, aep@world.std.com (Andrew E Page) writes:
>   Who makes the most reliable/compatible concentrators?  Single
>and Dual Access.  
>
>-- 
>Andrew E. Page   (Warrior Poet) |   Decision and Effort The Archer and Arrow
>Mac Consultant                  |     The difference between what we are
>Macintosh and DSP Technology    |           and what we want to be.

We have tested a number of concentrators and found that with the exception
of one, the question is not reliability or compatibility; rather, it is
more of capability and cost.

In almost all the concentrators we have used and tested none have had problems
with reliability.  We have stress tested each of them very thoroughly and
found only one to have problems.  Further, they all work perfectly together
(except for the one).

The concentrators we have tested range from the very basic 10k boxes up to
40k boxes.  The differences are in the area of services.   The 10k boxes have
a single MAC and no control over configuration.  The more expensive devices
allow for additional control over internal connection of the M ports to
the various paths (i.e. primary, secondary, local, or isolated).  Additionally
the more expensive concentrators also allow for software reconfiguration and
inband management through SNMP whereas the cheaper concentrators do not have
the SNMP and require switches for reconfiguration.  

Had all the tests been positive for all the concentrators, I would provide
names.  When evaluating concentrators I have learned a number of lessons.
First, don't listen to the salesman over the phone...get it all in writing
and as a quote.  Additionally, when purchasing require a contract that
specifies exactly which services will be required for operation.  This will
come in handy when the concentrator is delivered and the vendor "left out"
something or the latest version of the firmware is not ready.  

I also have made a list of questions that the vendors answer before I will
consider them.  Briefly:

1.  How many MACS?
    a.  How many are standard?
    b.  How many can be added later?
2.  How many internal paths are available?
    a.  Can any MAC be placed on any of the internal paths?
    b.  Can any M port be placed on any of the internal paths?
    c.  Are the internal connections software configurable?
3.  What version of SMT?
    a.  What will be delivered?
    b.  Will I get future upgrades and at what cost?
4.  How are firmware upgrades made and do I have to return the concentrator
    to the manufacturer for upgrades?
5.  If bugs are found in the firmware, what is the process for correcting the
    problem?
6.  Does the concentrator support SNMP?
7.  Does the concentrator support remote Logins through TCP/IP?
8.  What is the maximum number of M ports that can be added?
9.  How many cards may be added to the backplane?
10. If bridging/routing are needed, does the vendor provide a card which can
    perform this function?

There is a slew of other questions that can be asked; however, I have found
that these cover most of the things that salesmen try to cover up if they
do not support them.  Just as an example, two concentrators that we purchased
cost approximately 40k.  Each provides multiple MACS.  Both salesmen said
that his concentrator had configurable MAC and port placement.  When they were received, one was very easy to configure though a console connected to a serial
port and the configuration is saved in eeproms.  The other required that you 
remove the main card and set DIP switches.  Clearly one is much easier to work 
with.  

As another example, most of the concentrators require that a set of proms
be replaced to upgrade the firmware.  However, we have found a number of
concentrators which use eeproms and allow for the firmware to be upgraded
either inband through the TCP over the FDDI or through a floppy disk on the
concentrator.  Additionally, some of these devices allow for this upgrade
to take place while the concentrator is in operation and the transition
is very simple and easy without ever opening up the box.

Compatibility does not seem to be an issue until you put something wierd on
the network.  We also do testing of FDDI stations and found that a one particular
vendor of FDDI cards for the SUN causes one of all concentrators to start doing
strange things.  The only way to remedy this problem is to remove the station
or remove the concentrators.  All the stations work with this particular station,
but the concentrators hose up.  Without names, this doesn't do you much good;
however, the underlying point is that most companies will allow you to test
their concentrator in your network for a week or more to determine these issues.
Take advantage of this.

As a disclaimer, our funds are limited and I have not had the opportunity
to test all the concentrators available.  When we purchased the equipment for
these tests we purposely looked for concentrators which covered the entire
spectrum (cheapest to most expensive, least functional to most functional).  
When the tests were started the number of vendors of concentrators was limited.  
However, you can find a large array of vendors now, and since we have not had the 
pleasure of testing a majority of products, I don't think that it would be
in anyone's best interest to list the names of the vendors we have tested.
---
Scott Hiles
whiles@relay.nswc.navy.mil

Standard disclaimer:
  The opinions expressed are those of my own and do not necessarily 
  reflect those of the DOD or the Navy.  I accept full responsibility.
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