Conference netcad::hub_mgnt

Burance,

     That configuration is certainly supported by by DEChub 900MS. 
As a matter of facts, you are only using 12 out of the possible 14 
flexible cannels available for this. Keep in mind, however, that 
history of insertion, and slot position is important. In other 
words, if you start from scratch and connect all your 
concentrators from left to right, each pair being in contiguous 
slots, you should see no problem. On the other hand, if previous 
to doing this configuration you have done several LAN hopping 
changes, and your concentrators are connected so that each pair 
do not reside in contiguous slots, then you might see the situation 
where connections will be rejected. This could happen because you 
might end up with only split channels available when your connection 
requires full-length channels. Remember that out of the 14 channels, 
4 are split channels, i.e., they only run through half of the slots,
2 running from slot 1 to slot 4 and 2 running from slot 5 to slot 8. 

Eladio

    Hi Eladio,
    
    In a network seminar, I heard that only 6 flexible ethernet and
    2 FDDI flexible channels is supported for the time being.
    It is proved that no more than 6 flexible ethernet channels 
    can be created. 
    
    Since I don't have enough equipment to test the maximum number of
    FDDI channels, are you sure that under the current technology
    (not theoretical) 12 FDDI channels can be supported ?
    
    
    Thanks,
    Burance.
    

Burance,

I am not sure why they told you that in the seminar. Right now all the 
14 flexible channels in the backplane are available for FDDI. It is 
true that only 6 channels are available for Ethernet, and I believe it 
is done that way because of a repeater limitation rather than a hub 
limitation. I am conducting system test for the DEChub 900MS and for 
the DEF6X concentrator and believe me, I have created similar 
configurations many times. As a matter of facts, I have had 
configurations where all 14 channels are being utilized. This can be done 
with a hub fully populated with 8 concentrators. Since 8 concentrators 
configured Trunk AB will require 16 channels, the only way of having 
all of them in the hub is by configuring 6 of them Trunk AB, one Trunk A, 
and one Trunk B. I order to complete the ring you need to externally 
connect the Trunk A and Trunk B concentrators. However, all the 14 
internal channels are being used, and it works pretty good! This is not 
theory. It is a real configuration that we have tested many times in the 
lab. 

Eladio

    Hi Eladio,

    Thanks for your solid answer.
    
    >This can be done with a hub fully populated with 8 concentrators. 
    >Since 8 concentrators configured Trunk AB will require 16 channels, 
    >the only way of having all of them in the hub is by configuring 6 
    >of them Trunk AB, one Trunk A, and one Trunk B. 
    
     From your description, when DC900MX is configurated with AB pointed
     to the backplane and occupies 2 channels, should we see 2 
     "red leg" attached to the DC900MX icon ?  
    
     I have tried that there is only one "red leg" labeled with "1"
     attached to the icon. But does it mean that it occupies 
     2 channels ?
    
     If there are 2 concentrators with both AB pointed to backplane,
     how can we connect A-B and A-B (2 seperate channels) ?
    
    Thanks,
    Burance.
    

    supplement to .-1
    
    I use HUBwatch V3.0 and DEF6X200.bin for DC900MX.
    

    
    Burance,
    
    
    	Regardless of whether you have A, B, or AB to the backplane
        HUBwatch will show you the one "red leg". So it has 2 states,
        no "red leg" or one "red leg". You connect the module to the
        FDDI LAN by pulling that single leg down to the LAN. HUBwatch
        and the MAM do the rest. I think that having 4 seperate icon 
        states might be clearer (one of which is no leg for AB out the front).
        It would help someone looking at the LAN Interconnect Window
        know whether their A or B is going out the front, without needing
        to pull up additional windows.
    
    Bob
    

    Burance,
    
    	As Bob says, Hubwatch will always show only one "leg" regardless
    of your configuration. To know if it is trunk A, B or AB you have to go
    to the Station Configuration window and look there. I certainly believe 
    that it would be much better if we could tell the configuration directly
    from the LAN Interconnect window. 
    
    	If you have two concentrators configured Trunk AB, and connect both 
    to the same LAN (ring), the MAM will do all the work for you, i.e., you
    will end up with a correctly connected ring which, by the way, will 
    consume 4 flexible channels.
    
    	Regards,
    
    	Eladio 
    
    

 Elodio,

 can you explain (may be with a little picture) why 4 IMB are reserved
 for this particular config .

  thanks

    Each FDDI backplane connection requires 2 flex channels, one for
    transmit data and one for receive data. The FDDI signal definition for
    a flex channel is 5 bits of data and 1 bit for clock, thus using all 6
    bits of a flex channel. The FDDI channels are unidirectional, therefore
    one flex channel is needed for the transmit direction and one flex
    channel for the receive direction.
    
    The previous note mentioned a Trunk AB connection. This is a DAS
    connection. Thus each connection (A to B and B to A) requires 2 flex
    channels. Therefore the full Trunk AB connection between two modules
    requires 4 flex channels. A SAS connection (Trunk A or Trunk B) would
    have only required 2 flex channels, one for transmit and one for
    receive between the 2 modules.

  as you say, if i put 8 concentrators in DAS i consume 16 IMB
   in HUB900, as this configuation i'snt supported ???

  Jean-Yves

    I think 14 FDDI is the max so something should break if you go beyond
    that.
    
    dave

   Dave

>>>   I think 14 FDDI is the max so something should break if you go beyond
>>>    that.

 as you say  7 concentrators is a upper limit in DAS ???

  Jean-Yves

	You can put 8 concentrators in but you will get a wrapped ring unless
	you connect to the "outside".

	But most people will setup one concentrator as a Trunk_A, 6 Trunk_ABs,
	and one Trunk_B.  And then you take the whole HUB and connect that
	to the trunk ring in the building.

	Luc

  
  Thanks luc,

  i agree that's works in this configuration

  Jean-Yves

    Gee, until I entered this reply and screwed up the number of
    replies count, the "Replies" column had the correct answer
    to the question asked in .0's title.
    
    Never mind.
    
    Dave