Conference netcad::hub_mgnt

    
    If I remember my DEChub 900 training correctly, repeaters connected
    across the backplane do NOT increment the repeater count. 

    Multiple 900 repeaters on the same IMB are counted as one repeater
    count.  However as soon as you link a 900 repeater from a IMB to the
    thinwire, to pick up a 90C or a 90FA, you start the count.
    
    Since you have done this in both hubs you now have 4 repeaters and 5
    coax segments.  The number of coax segments allowed is 3 but since 2 of
    the coax segments are the 90 thinwire backplane, they can be counted a
    zero length segments.
    
    Bottom line is that you are OK for now.
    
    dave

    I would count that SPECIFIC config as 4 repeaters, and FIVE segments.
    because the 90FA does not attach to an IMB, so you don't get the
    benefit of the 900-series single-repeater functionality. 
    The Thickwire as SEgment 1, the Hub internal THINWIRE backplane does
    count as a tapped segment, (and you have one in each hub) that that's
    THREE tapped segments.  you also have a link segment going to each
    workstation, for a total of five segments.  Your network is valid, and
    at it's maximum extents.
    
    If you used all 900 series hardware (and perhaps a fiber backbone) you
    would reduce your segment counts.  
    
    JR
    
    JR

>>  I would count that SPECIFIC config as 4 repeaters, and FIVE segments.

    Yes, to be safe.

>>                               the Hub internal THINWIRE backplane does
>>  count as a tapped segment, (and you have one in each hub) that that's

    I'm assuming that the same rules that apply to the 90 hub, apply to the
    900 hub thinwire.  If the 90 hub is terminated, it can be counted as a
    ZERO length segment and effectively ignored.  However, as soon as you add
    a piece of thinwire to the hub, it then must be counted.  The same should 
    apply to the 900 chasis as the thinwire is permanently terminated.  If
    that is the case the config would be 4 repeaters and 3 segments (one
    coax and 2 link segment).

    If Ed or someone from engineering disagrees, let me know.

    dave
    

    
    	Dave, I asked this back in Topic 1766 and the answers in 1766.3 and
    1766.5 seem to disagree that you can disregard the length of the
    thinwire connection in the DH90 or the DH900.
    
    					Bill

    A zero length segment?   I have never heard this.   the rules that I
    use to configure a 90-series hub is:
    
    The internal impedance loss of each connector of the backplane create a
    virtual thinwire equivalance of 15 stations, and 65 meters of ThinWire.
    
    That is why you cannot attach more than 125 meters outside the hub, or
    55 meters directly (no "T" connectors) to another hub.
    
    I always count the backplane of a 90 Hub as a ThinWire segment.  You
    get to it through ONE repeater, and leave it through the SECOND
    repeater.
    
    JR
    

    
    You can be creative with paired DEChub 90s. I've sold solution with
    systems in the middle of DEChub 90 pairs and they've always worked. I
    come out each one with a cable and connect them in the middle with a
    T-connector to connect up systems and standalone module remembering not
    to exceed the 185 meter Thinwire. Always worked for me...

    re. .5
    
    Bill,
    
Note 1766.3 mostly references repeater hop count within the hub.  It does
talk about the actual segment count.
    
Again I agree with the repeater count.  Ed Buzzell's explaination with
regards to zero segment length has nothing to do with how many taps the
the hub thinwire has on it, be it 1 or 8.  It has to do with length.  If
the thinwire is contained within the hub, ie. terminated, the segment
is so short, ie. ~17 inches, that it can be ignored.  If you add coax to
the side of a 90 hub it is no longer just 17 inches.  Usually its many feet
so no longer that nice short internal thinwire.  While contained in the hub
the collision domain is short that its length can be ignored and according
to Ed the segment can effectively be ignored.

Anyways, I'll leave it to Ed to correct me if the philosophy has changed.
    
dave

    I wouldn't want to assume that the customer will never expand that "T"
    connector at the side of his DEChub 90.  
    
    I feel that it is important to provide a customer with a configuration
    that has room to grow, and is not "MAX'ed out" at install time.  He
    should be able to buy a repeater module and insert it in any hub (you
    know they will try...), or attach ThinWire to the end of an existing
    terminator without causing my design to stop working.
    
    
    It depends on the goal of your sale.  If you want to meet an immediate
    connectiviy need, or meet his architecture needs for his MIS strategy.
    
    

    You are sooo right.
    
    dave