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Conference 7.286::fddi

Title:FDDI - The Next Generation
Moderator:NETCAD::STEFANI
Created:Thu Apr 27 1989
Last Modified:Thu Jun 05 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:2259
Total number of notes:8590

92.0. "Config question" by WOTVAX::MEAKINS (Clive Meakins) Tue Jul 17 1990 06:52

    My coustomer has sent me a query on a possible configuration for their
    FDDI.
         
        Basically it would consist of two Wiring Concentrators (CON) in 
        separate locations dual connected to form a hub.  This would be the 
        entire extent of the FDDI dual ring.  Since CON's are Dual Attachment 
        Stations and we have been told that DAS's can be connected to two 
        different CON's, it is proposed that from each Intermediate Cross 
        Connect (ICC) located in the major site buildings a CON would be 
        connected to both of the hub CON's.  The advantage here would be 
        that should one of the pair of hub CON's go down the whole network 
        should continue from the other.  From the ICC the connections would 
        be tree form.  
    
    What I would like to know is, is this a viable (legal ?) configuration? 
    Would it work ?  Is it a worthwhile thing to do ?
    
    Any other comments/suggestions ?
   
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92.1sounds goodZPOV03::HWCHOYFE110000Tue Jul 17 1990 10:166
    re.0
    
    looks Ok to me! And if the customer is willing to pay for it, I'd say
    let's do it.
    
    hw
92.2KONING::KONINGNI1D @FN42eqWed Jul 18 1990 09:2911
What you described would work.  But in general it is best to keep the
dual ring entirely within a SINGLE room.  So I'd put the two concentrators
in the same room, and have all the other rooms be ICC with connections to
both concentrators.

The point is that your entire network is dependent on the integrity of
the dual ring, so it is wise not to expose it to damage.  If you keep it
in one room, you minimize the risk of having that vulnerable point
damaged.

	paul
92.3Separate physical locationsWOTVAX::MEAKINSClive MeakinsFri Jul 20 1990 06:4211
> What you described would work.  But in general it is best to keep the
> dual ring entirely within a SINGLE room. 
    
    I take your point, but waht my customer is worried about is a single
    point of failure.  There is a real possiblity of serious flooding on 
    this particular site and of course there is fire etc also.
    
    The intention of the described config was to remove a single point of
    failure in these circumstances, ie within a physical location, not just
    within a piece of equipment.  As such, is this a sensible way to
    approach the problem?
92.4KONING::KONINGNI1D @FN42eqMon Jul 23 1990 16:3813
Yes, if you are worried about the vulnerability of an entire location, then
clearly you need to branch out from two places.  I believe that the number
of cases where that level of paranoia is sensible is rather small, so the
recommendation to leave the dual ring confined to the MCC still applies to
most situations.  For those cases where you do go to this extreme, keep the
dual ring confined to just TWO locations, and watch closely over the cable
routing between them...

One reason why I make this point is to reduce the temptation to use "bypass
relays".  These are a popular nostrum but far worse than the problem they
"solve".

	paul