Conference netcad::hub_mgnt

    I can talk about this with unbridled authority thanks to other notes
    who bore with my thickheadedness on understanding these products.
    Currently, only SIX (6) flexible channels are available to the
    DECrepeater 900FP and DECbridge 900MX. Basically, the hardware in each
    of these modules are HARDWIRED to the pins which touch the first SIX
    (6) flex channels. 
    
    Also, the DECrepeater 900FP has SIX (6) port-pairs which can be
    assigned to the SIX (6) flex channels. In order to do what you want,
    you'll need TWO (2) DEChub 900 Multiswitch units. Then, you can join
    the units together using the front panel FDDI A/B connectors to create
    the configuration you want. 

    Wade,
    
    I called but you weren't in.
    
    You could get a little wierd (read creative).  You could put 2 DB900's
    in one DEChub 900.  Leave the AUI ports switched to the front panel.
    On 1 DB900 switch the 4 UTP to the backplane.  On the other DB900
    switch 2 UTP to the backplane and either leave the other 2 to the
    front panel (or possibly switch 1 to the thinwire).  You can still
    plug in 2 or more of the DR900FP's into the hub.  Take your 6 Ethernet
    channels and distribute them across the DR900FP's ie. one or more
    fiber pairs get Channel 1. Same for Channel 2 and so on.
    
    You still have 4 AUI's.  You could put fiber MAU's on them and patch
    them directly into the fiber to each location.  Or you can take
    the fiber from the MAU and connect into one of the fiber ports on
    the DR900FP and create several LANs within the DR900FP that DO NOT
    connect to any of the backplane channels.  Essentially a self contained
    LAN.
    
    The remaining UTP ports on the front panel could be used to connect
    servers, etc.
    
    I talked to Daryl Whitlock yesterday and he said that with only
    6 Ethernets per hub (and needing 12) it would double your quote.
    You still need the same number of DB900's and DR900FP's.  What you
    only need is twice the number DEChub 900's or am I smoking shredded
    gym socks?  8^)
    
    dave

    
    	I have read note 651 which states that I require 2 channels for
    interconnection of FDDI modules.  Are these restricted to the same 6
    channels previously mentioned???  Does this mean I'm restricted to
    three FDDI modules in an 8 slot hub?
    
    Scott
    

    I'm told that the FDDI modules can use any channel.  Ethernet channels
    are assigned from the top down and FDDI from the bottom up.  FDDI
    modules have enough chips in them to connect to any channel.  Ethernet
    modules presently have enough chips to connect to 6 channels.
    Hopefully that will be extended to 10 to 12 in the future.
    
    Another interesting thing I've found with HUBWATCH and the 900 hub.
    I regularily create 8 to 10 Ethernets in the hub and everything
    is fine.  I take a 900TM and connect leg 2 to Ethernet 1.  Then
    I connect that leg to Ethernet 10 and everything still works fine.
    I assume that by creating a LAN that nothing really happens in the
    hub other than the hub manager noting how many wires are used or
    free.  Only by connecting a module to a channel are wires actually
    assigned.  With the 900TM in the hub and being connected to Ethernet
    1 and then being moved to Ethernet 10, I'm assuming that the SAME
    wires are being utilized.  Only us poor humans think we've selected
    a different channel.  The hub manager assigns wires in the most
    effective way.
    
    dave

    
    All the FDDI-capable modules can use 14 flex channels (they can't use
    the 1 flex channel on the upper connector), so you can configure a full
    hub of FDDI.
    
    .4 notes that you can actually use HUBwatch to create more Ethernets
    than any (current) module can use; this is correct - but if you were to
    try to actually use more than 6 of them it would fail because the
    modules would be out of signals.  For the new half-height repeaters
    that can LAN-hop (DEFMI and DETMI) this limit is 1, since they can use
    only the 1 channel on the upper connector.  No signals are allocated to
    a LAN that has nothing connected to it.
    
    The allocation is more involved than top-down/bottom-up, but the
    results are pretty much the same; the hub manager reads from the
    modules what signals each module can use for what interface and then
    matches the least flexible interfaces (the ones than can use the fewest
    signals) with the least valuable signals they can use (a signals value
    is the number of interfaces that can use it).  The result is that if
    there are any Ethernet capable modules in the hub, then the FDDI will
    be allocated on the signals that can't be Ethernet.
    

    If you only have FDDI in the hub and then start adding Ethernet,
    does the hub manager relocate FDDI modules off the Ethernet wires?
    
    If it does then I assume its fast enough that only packets on the
    wires at that time are lost?
    
    dave

    
    If there is no Ethernet in the hub, the hub manager will not attempt to
    avoid using the channels that could have been Ethernet.
    
    If you then add Ethernet and start connecting it, you may displace FDDI
    connections onto different channels.
    
    As for how much is lost when you do this, it will certainly be fewer
    packets than if you were to swap UTP connections around by hand.  LAN
    hopping is not switching - you will loose some packets (no, I don't
    have a number).

>>    (no, I don't have a number).
    
    And you were doing so well until then.  8^)  8^)  It's just as well
    you said that or the next next question would have been...

    dave