Conference 7.286::fddi

    Soumetty,
       YOu can connect two systems back to back using a SAS device
    (cheapest). But this will be the extent of your FDDI network as there
    is no way to add any other stations. If you use DAS devices you will
    have created a 2 node FDDI ring and can add other devices in to the
    ring at will.
    
    Debbie
    

re .1

Hi Debbie,

I was under the impression that it would be possible to extend the SAS to 
SAS case in your reply by adding a DAS in the middle.  Am I correct about 
this?

Of course, even if my understanding is right, the ring would not be 
operational while the DAS were being inserted between the two SAS.  A 
solution starting with DAS only would have an advantage in this regard.


Malcolm

    Hi Malcolm,
       A-S and B-S connections are valid, but you don't gain much by it and
    can have some management headaches. If the DAS in the middle is
    concentrator then of course this would be the way to go. If it were a
    system, then you would have something that looked like this:
    
    
    ------        --------       ------
    |   S|........|A    B|.......|S   |
    |    |        |      |       |    |
    ------        --------       ------
    
    A port = Primary Ring in, Secondary Ring out (when in a ring config)
    B port = Primary Ring out, Secondary Ring in  ""    ""      ""
    S port = Primary Ring only (in and out)
    
    So you haven't gained too much by adding that DAS device in the middle,
    but it can be done to increase your non-ring FDDI network by one node.
    
    Not something I would recommend to a customer except in unusual
    circumstances.
    
    Debbie
    
    

    
    Per .1
   > YOu can connect two systems back to back using a SAS device
   >     (cheapest).
    
    
    How do accomplish this? Is it as simple as taking a set of fiber optic 
    cables and plugging them on to the distribution panels of each system?
    Or do you need a concentrator?
    
    
    thanks,
    
    Bob

    
    Just take a cable, and plug the two systems together. Nothing else
    is required.
    
    When you want add a 3rd system you will need to buy a concentrator.

    Which cable do you need to connect 2 SAS/UTP FDDI controllers together
    (eg. 2 DEFTA-UA) ?
    
    Direct or cross-over ?
    
    Any reference plse ?
    
    Regards
    
    	Pierre

All FDDI UTP connectors are pinned out the same. This means you will
*always* need an *odd number* (1,3,5,etc) of crossovers when connecting
two ports together. Obviously one cable is sufficient.

Digital's UTP crossover patch cord is the BN25H.

bill

    Thank you !
    
    	Pierre

    
    
    Just to make sure I understand, then in .3, that it is valid
    to connect a SAS directly to either the A or B port of a DAS?
    
    I would like to do this only for testing purposes, as it is
    not the true network configuration.
    
    -BobF

    Yes, an S-A or S-B is valid.  The only problem that you may have is if
    the A or B, of the DAS, is already connected to an M port.  In this case 
    the tree cnx (M) would be preferred over the other.
    
    For example -
    
    			DAS
    		      A	    B
    		     /	     \
    		    /         \
    		   M           S
    
    	The A-M cnx would come up and the B-S would not.
    
    Bill                                                
    
    

    
    
    For testing purposes, can I connect the A connector to the
    B connector on a DAS device to form a loopback connection?
    
    -Bob

    ...except that it isn't a loopback - it's a ring with one station on it
    - your station.
    
    MDL