Conference 7.286::fddi

    Walter,
      Are you looking for the product manager for STP, the marketing person
    or someone in engineering? I don't believe we showed FDDI over STP at
    Interop, but we did show it this week at ComNet'91 as a technology
    demo. There was no announcement of a product, but we did state that we
    are considering using STP for the horizontal runs in structured wiring
    environments. Since the standard has just been started for FDDI over
    Copper, it will be awhile before you see actual products from any
    vendor (at least anything that will be interoperable with anyone else).
    
    Debbie
    

    I am the one of the people dealing with FDDI over both ThinWire and
    STP.  Your external sources are wrong!  DEC did not show any FDDI over
    copper at Interop (although others did).  DEC did show FDDI over both
    ThinWire and STP at the COMNET '91 show last week.  There was an article
    written for the Sales Update last month but because it was too long the
    article was bounced until this months issue.  I will post the article 
    as the next reply.
    
    DEC did a technology demo and did not do any product announcement
    surrounding the technology.
    
    If you have any futher questions about copper FDDI please let me know.
    
    		Jamie Warter
       		DEFCN Product Manager
    		DELNI::WARTER
    		226-5892

                              TELECOMMUNICATIONS and NETWORKS

     ANNOUNCING TECHNOLOGY DEMONSTRATION ...

          Communication Networks `91 Event, January 28 to February 1, 1991
                               Washington, D.C.

          Digital demonstrates FDDI technology over ThinWire(tm) and
          Shielded Twisted Pair (STP) media

                         James Marsh         James Warter
                         DTN:  226-5127      DTN:  226-5892
                         LKG2-1/N2      LKG2-1/Z3

            ===============================================================
            |                                                             |
            | o Demonstration will show applications running 100 Mb/sec   |
            |   FDDI over 100 meters of Shielded Twisted Pair (150 ohm)   |
            |   and ThinWire(tm) (50 ohm Coax) media                      |
            |                                                             |
            | o Support for low-cost media in cabling to the desktop      |
            |                                                             |
            | o Potential for significant decrease in cost of FDDI        |
            |   interconnection                                           |
            |                                                             |
            | o Products based on this technology NOT announced           |
            |                                                             |
            ===============================================================

     In response to customer requests, Digital has been working on solutions
     which would allow customers to make use of existing, ThinWire(tm) and/or
     Shielded Twisted Pair (STP) cabling in FDDI topologies.

     The American National Standards Institute (ANSI) X3T9 Committee is on the
     verge of establishing a formal committee, or working group, to develop a
     standard for FDDI over Copper.

     This technology affects only the Physical Media Dependent (PMD) component
     of the ANSI standard, and complies with the existing Physical Protocols
     (PHY), Media Access Control (MAC) and Station Management (SMT) sections of
     the standard.


     Advantages of using FDDI with copper media:

        o  Support for low-cost media in horizontal, "to the desktop"
           applications

        o  Protection of existing cable plant investments

        o  Greater flexibility in creating FDDI topologies

        o  Less expensive FDDI implementations, expanding the use of
           existing Digital FDDI platforms

     More detailed information on Digital's ongoing research and development
     with alternate media can be found in the FDDI Proprietary Information
     Disclosure, PID #TAN040.1.

    
    Hey guys - can you please clarify where we're going with all this
    Copper-DDI ?!
    
    Future support for STP (& UTP eventually ?) and Thin-wire with the
    constraints of distance etc. 
    What about Standard Thickwire cable too, or is this cable not
    "suitable" for FDDI implementation ? Didn't we say that about TP and
    Thinwire to start with ??
    Just think if we could use existing Ethernet backbones we may not need 
    to put fibre in at all !!    ;-} Only kiddin' chaps.
    Is there any mileage in this train of thought ?
    
    Regards
    
    Rog

Clearly you can use thickwire wherever thinwire works, since it's higher
grade cable.  (Actually, that's not quite true: the cutoff frequency
of small cable is higher than that of large cable, but unless you're
working at many gigahertz that's a non-issue...)

FDDI wiring is radial from concentrator to end station, which makes it
a good fit for standard twisted pair configurations, and also for many
thinwire configurations.  Ethernet thick wire is normally backbone wire,
not office radial wire.  In other words, while it should work just fine,
you're unlikely to have it installed in the places where it could be used.
And if you have to pull new cable, would you pull thick Ethernet cable
for FDDI?  Probably not.

	paul

    I'm at NET-U right now.  You could use thick/thinwire in theory but the
    topology is the problem.  Thinwire works by way of full duplex
    operation on the coax by something similar to FDM (muxing of 2 signals,
    one for each direction).  By doing it this way eliminates the need
    for 2 coax cables to the end system but now eliminates the the ability
    to daisy chain systems like 10baseT.
    
    So you could use thickwire for FDDI but by the nature of the way
    it's done you would have to remove all taps and systems except the
    one system at the end of the coax.  You would have to run an individual 
    thickwire coax cable to each system.  Not an inexpensive way to
    do it.

    dmm