Conference netcad::hub_mgnt

1) Yes, it's true that the current Ethernet line-card's hardware can only 
   connect to six of the flex-channels on the DEChub900 backplane.
2) Since this is a hardware restriction, a firmware upgrade won't help.
3) Don't know.
						-Shawn

    I'd be curious to know what kind of network configuration would need
    more than 6 lans in the Hub? Are they all independent, would there be a 
    switch in the Hub, etc.
    
    Mike

    Thanks for the quick replies.  The customer has successfully 
    reconfigured his hub to use only 5 lans.  He is happy now.  
    I think the real issue is that the documentation implies that there 
    are 14 usable lans and he wanted to use them, even if he didn't
    need to.   I agree that there are 14 lans there,  but if there
    are not any modules that use them,  then they are not really 
    usable and that was the customers issue.
    
    					Thanks again,
    			
    						Danny 
    
    

Danny,

Yes, I can see how this is a customer perception issue.

One minor point though.  You stated, "...I agree that there are 14 lans 
there, but if there are not any modules that use them, then they are not 
really usable...".  In fact, the FDDI modules are capable of connecting 
to any of the 14 backplane flex-channels.  However, this does not mean
that you can have 14 FDDI LANs on the backplane.  It means you can have 
up to 4 FDDI LANs on the backplane.  You need at least two modules to make
a ring and there are 8 slots.  8 of the 14 flex channels are used in
this case.  How many would you describe and "usable"?

How many LANs can you have on the backplane with our current offerings?
I'd guess 9 - 6 Ethernet and 3 FDDI.  Your mileage may vary.

And by the way, there are ways to share channels.  So, in the future,
there may be more than 14 available channels for some media types.
How many will qualify as "usable".  I dunno.

You can see how marketing these capabilities is challenging.  I don't know
how to concisely explain the existing capabilities.  Perhaps the 
flex-channels should be presented to customers as "capabilities" and 
"investment protection."  (I'm not in marketing so I'll shut up now.)

							-Shawn

    re .2
    >I'd be curious to know what kind of network configuration would need
    >more than 6 lans in the Hub? Are they all independent, would there be a 
    >switch in the Hub, etc.
     
    I have encountered a configuration a couple of times where I could use
    more than the 6 internal channels and have not found a good solution.
    For a collapsed fiber Ethernet backbone.  To even put 2 * DEFMMs and 
    2 * DEFBAs with all 10BaseFL links coming in the best I can see to do 
    it to get 7 Ethernets in the hub, 4 with tranceivers on the AUI ports,
    six IMBs and the ThinWire.  This still does not make full use of both
    DECSwitches and using the tranceivers limits me to one fiber link.
    With more LANS you might be able to put another set of fiber repeaters
    and switches.   
    
    ...scott

> How many LANs can you have on the backplane with our current offerings?
> I'd guess 9 - 6 Ethernet and 3 FDDI.  Your mileage may vary.

Sorry, Shawn!  You don't win the new Ford Aspire and the "Greatest Hits
of the '70's" collection from Time-Life Records.  But we do have some
lovely consolation prizes for you...

You forgot the ThinWire Ethernet and the Token Rings...  That's 3 more.

So, 9+3 = 12.

    I'm currently working on a proposal were the customer has 12 distinctly
    different ethernet lans. the proposal calls for 6 wiring closets and a
    computer center. Each closet has multiple lans. Most are under 6, but 2
    have 11 potential connections and the computer center gets all 12.
    
    We were able to configure 1 DEChub 900, 1 PORTswitch 900FP and a
    combination of DECrepeater 900TM and PORTswithc 900TPs per hub. The
    closets with more that 6 lans required 2 hubs even thought there are
    plenty of available slots.
    
    	-Scott

    
    Of course it's a hardware limitation.
    What you have is only 6 "LAN Engines", the term refers to the
    physical circuitry that all the modules have for connection 
    to the backplane.
    Modules like the 900TM only have one LAN engine instead
    of 6 like in the port switching modules (900FP & 900TP).
     
    

    Most designs of a large building, switched to each closet, multi
    DECswitch 900EFs require more than 6 internal LANS to gracefully
    execute.  The media flexibility of the DECswitch 900EF limits remote
    fiber connections.  When you substitute a Portswitch FP you then can't
    interconnect beyond 6 across the backplane.  
    
    The real "gotcha" is the media flexibility on the switch.  We lost
    HealthAmerica because the CISCO offering allowed modular media
    adapters.
    
    With the ENVISN marketing - push-point-click virtual lans the need to
    be physical flies in the face.
    
    So - yes, we DO need more than 6 LAN segments or better media
    flexiblity!
    
    ttfn,
    j
    

    re. .2
    
    Over a year ago a customer of mine wanted to do switched Ethernet to 10
    floors.  Each floor was to have their own 10Mb.  But since the hub, or
    should I say, modules only have chips for 6 segments, they were forced
    to pair some floors until they got enough money and rack space to put
    in a second hub.
    
    With modules like the PS 900TP, you can do some front panel patching to
    get around the module limitations like 6 Ethernets.  Not eligant but it
    works.  I like to avoid front panel patching as much as possible
    because we start to look like Synoptics.
    
    The need is here and has been for some time.
    
    dave

    
    I must add my voice here in support of .10.
    
    A lot of vendors are offering switches that can support 12 or more
    ethernets and 2 or more FDDIs. In large work areas where you have 100+
    users requiring descent ethernet performance you have to give one
    ethernet segment to 10 or less users thus requiring 10 or more ethernet
    channels on your hub.
    
    We just lost a major customer because of the limited number of
    ethernets on our backplane.
    
    Sam Mokbel
    Resident consultant at Mcclellan Air Force Base.