Conference netcad::hub_mgnt

457.0. "Does this work?" by HGRNCC::FARADAYCHONG (Faraday Chong@hgo 852-8053590) Fri Oct 29 1993 08:13

*** Cross posted to ETHERNET and HUB_MGNT notes ***

Need help in verifying and confirming if the following network is
within 10BaseT and four repeater rules.

                  Systems
                    | |
o--------+----------|-+--------------------o Ethernet #1
         |          |
o--------|----------+---------------+------o Ethernet #2
         |                          |
         |                          |10BaseFL 2000m
         |                          |
+--+-----++-----+DEChub    +--+-----++-----+DEChub
|9|9|9|9|9|     |900 MS    |9|9|9|9|9|     |900 MS
|0|0|0|0|0|     | #1       |0|0|0|0|0|     | #2
|0|0|0|0|F|     |          |0|0|0|0|F|     |
|T|T|T|T|L|     |          |T|T|T|T|L|     |
|M|M|M|M| |     |          |M|M|M|M| |     |
+--+-+----------+          +--+-+----------+
  P|  \                       | |P
   |   \   10BaseT 100m       | |
   | ___\______________________ |
   |/S   \______________________|
  FTT                     S    FTT
   |                            |
  +++                          +++
  |9|    10BaseT 100m          |9|    10BaseT 100m    about 114 units of
  |0|________________          |0|________________    900TM at this level
  |0|________________          |0|________________    connection to 1,800
  |T|________________          |T|________________    PC via 10BaseT cable
  |M|                          |M|
  +-+#1                        +-+#2

900TM: DECrepeater 900TM, hub module in DEChub 900 MS, or DEChub ONE
90FL: DECbridge 90FL
FTT: Chipcom's Fault Tolerant Transceiver

We plan to propose this to a customer on Monday and need advice if any
potential problems.

(1) The 10BaseT cable between 900TM, and between 900TM and PC could be
each 100m, ie, the cable length from PC to DEChub 900 MS would be about
200m, this is required due to physical constraint in the customer
environment

Is 200m in this within 10BaseT specification?

(2) The FTT provide automatic switching of the entire 900TM at the lowest
level from one DEChub 900 MS to another. Path marked "P" is the normal
active path, path marked "S" is the standby path.

(3) PC connected to 900TM #1 talks to PC connected to 900TM #2 will pass
thru 4 repeaters (900TM #1, 900TM in hub #1, another 900TM in hub #1, then
900TM #2.

Is this ok?
(Since the hub would be several hundreds meters away from "systems", and
customer prefer fiber rather then coax, our only option is to use either
DECbridge 90FL or DECrepeater 90FL or DECrepeater 90FA without going with
future products. We think bridge is better than repeater since it can
filter certain amount of PC-PC traffic. The drawback of these DEChub 90
module is it cannot use IRB in the DEChub 900 MS backpance, and forces
all DEChub 900 module to use the ThinWire backplane.

(4) Do you foresee any potential problem with this config?

Faraday

    I will leave the Ethernet folks to answer the cable length questions,
    but I can address some of the DEChub 900 issues:
    
    See 442.2 for more on counting hops on the 900 backplane.
    
    1) Make sure that you don't exceed the 200 address limit on the
    workgroup (hub backplane) side of the DECbridge90FL.  If you
    daisy-chain repeaters like that you can multiply ports pretty fast. 
    If there is any danger of exceeding the address limit, switch to
    repeaters and loose the filtering. In particular - what is the port
    count if the FTT fails over and _all_ stations are 'in' just one hub
    (and therefor all on the workgroup side of 1 DECbridge90FL).
    
    2) You don't need to use the Thinwire for all backplane ethernet just
    because the DECbridge90FL cant use the flexible channels.  Configure
    the hub like this:
    
             A       B       C    
           +---+   +---+   +---+   +---+
           | 9 |   | 9 |   | 9 |   | 9 |
           | 0 |   | 0 |   | 0 |   | 0 |
           | 0 |   | 0 |   | 0 |   | F |
           | T |   | T |   | T |   | L |
           | M |   | M |   | M |   +---+
           +---+   +---+   +---+     |
            | |     | |     | |      |
              |       |     | |      |
   Thinwire---)-------)-----+-)------+---------
              |       |       | 
   Ethernet---+-------+-------+---------------
    
    Repeater C and the 90FL are connected to the Thinwire (the 90FL
        connection is not configurable).
    
    Repeaters A, B, and C are all connected to an Ethernet segment that you
    create on the backplane.
    
    Repeater C repeats between the Thinwire and the Ethernet (flex
    channel), which counts as one repeater hop, but any hop between A, B,
    or C does _not_ count as a hop.
    
    So in your example (3) there are only 3 repeater hops.