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Conference 7.286::fddi

Title:FDDI - The Next Generation
Moderator:NETCAD::STEFANI
Created:Thu Apr 27 1989
Last Modified:Thu Jun 05 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:2259
Total number of notes:8590

1310.0. "How to connect 4 FDDI rings together" by CSOA1::TEATER (Fight the Good Fight) Fri Apr 08 1994 02:14

    Working on a response to an RFI (request for informtion), the customer
    wants 4 FDDI rings connected such that one ring connects to an adjacent
    in two (physical different) location.   Each ring will have multiple
    hubs that will then connect multiple LANS via routers.  This is a
    campus environment:
    
    (---H-------H-----H--------)                H = HUB (FDDI -> Ether)
    |                          |  Ring 1
    (---[    ]---H----[    ]---)                1-2x = FDDI routed from
        [1-2A]        [1-2B]                           ring 1 to ring 2
    (---[    ]---H----[    ]---)
    |                          |  Ring 2
    (---[    ]---H----[    ]---)                2-3x = FDDI routed from
        [2-3A]        [2-3B]                           ring 2 to ring 3
    (---[    ]---H----[    ]---)
    |                          |  Ring 3
    (---[    ]---H----[    ]---)                3-4x = FDDI routed from
        [3-4A]        [3-4B]                           ring 3 to ring 4
    (---[    ]---H----[    ]---)
    |                          |  Ring 4
    (---H----H----H----H----H--)
    
    This is a simplistic view, there are many more H type hubs on this
    network.  Can this config be accomplished using DEChub 900s?  I was
    thinking of using the FDDI modules, config the A/B ports for a single 
    ring and use the M ports to connect rings together.
    
    Could a gigaswitch be of more benefit?  The customer is looking for
    automatic failover (I believe the customer's spec are based on CISCO
    routers and Cabletron hubs).
    
    greg_t
T.RTitleUserPersonal
Name		DateLines
1310.1KONING::KONINGPaul Koning, B-16504Fri Apr 08 1994 18:5511
I'm having trouble parsing the picture.  What are those boxes that
interconnect the rings meant to be?

Note that a concentrator does not "connect two rings".  A concentrator
connects the things on its ports to a SINGLE ring.  It's the FDDI analog
of a repeater (which connects things to a single Ethernet).

Gigaswitch may be a good thing for what you're trying to do, but could
you make another stab at explaining the requirements?

	paul
1310.21 DEChub 900, 2 rings connected?CSOA1::TEATERFight the Good FightSat Apr 09 1994 01:5919
    I'll try again.
    
    Customer's wants four independent rings.  One ring will connect to an
    adjacent ring at two locations.  Thus R1 connects to R2, R2 connects to R3
    and R3 connects to R4.  The customer's terminology is four
    'overlapping' rings.  Picture four oval rings drawn side-by-side with
    adjacnet rings overlapping in two locations.  These overlapping areas
    is where the rings would join (somehow).
    
    My big boxes joining rings was attempt to show a DEChub 900.  I thought
    about having two seperate duel rings running on the backplane. Then
    connecting the rings via a 900 type module.  Please forgive my
    ignorance of the FDDI components of the DEChub 900.
    
    Can one FDDI module be on FDDI channel 1, a second FDDI module be on
    FDDI channel 2, then a third FDDI router/bridge module connect channels
    1 & 2 all in the same DEChub 900?
    
    greg_t
1310.3KONING::KONINGPaul Koning, B-16504Mon Apr 11 1994 16:5635
I still don't know hot to reconcile "independent rings" and "connect to
an adjacent ring".

Can we try this by Ethernet analogy?

Imagine four Ethernet coax cables, like the four rings you mentioned.
In what way do  you want these to be connected?

1. By repeaters?
2. By bridges?
3. By routers?
4. Not at all?

The implications are:

1. You really have just one Ethernet.  Everything is visible everywhere.
2. You have an "Extended LAN".  Every multicast/broadcast packet goes
   everywhere.  Individual packets go only where they need to.  Collisions
   and stuff like that doesn't cross from cable to cable.
3. You have a routed network; packets only go where they need to.
4. You have complete protection from failures elsewhere, at the expense of
   no communication elsewhere... :-)

The FDDI equivalents are:

1. Interconnection via concentrators.  You have only one ring, only one token;
   various failures will affect everyone.  All traffic goes everywhere.
2. Gigaswitch or DECNIS configured for bridging.
3. DECNIS configured for routing
4. (no connection).

Of the above, only (1) (and (4), of  course..) has a hub-based solution.
The others we can do also, but not exclusively with hub components.

	paul
1310.4Will look at other solutionsCSOA1::TEATERFight the Good FightTue Apr 12 1994 01:1743
    By the customer's terminology, they want the rings connect via routers.
    So I suppose I could have two different rings inside a DEChub 900 with
    them connect together via an external router box.
    
    Since the customer's RFI is based on Cabletron and Cisco, I would
    assume the backbone is several Cisco routers with FDDI cards that
    probably connect to a FDDI bridge module in the Cabletron HUB.  So the
    location where the rings "overlap" (or where adjacent rings join) would
    be a Cabletron hub on ring 1 connected to a Cisco a Cabletron hub on
    ring 2 connect to the same Cisco router.  This config can be repeated
    again on rings 1 and 2 at a different location on the rings and also
    repeat for the other adjacent rings:
    
           ----------------------------
    ring 1 |                          |
           -------hub----------hub-----
                   |            |
                 Cisco        Cisco
                   |            |
           -------hub----------hub-----
    ring 2 |                          |
           -------hub----------hub-----
                   |            |
                 Cisco        Cisco
                   |            |
    
    continue for rings 3 and 4.
    
    Since the Ciscos can have A/B port modules, they could probably have
    two installed per router and have each of the rings attached directly. 
    The router would then route and/or bridge between each ring (if they
    have that capability).
    
    I have other resources working other configurations.  The customer has
    96 strands of fiber in each dual ring which may be overkill.  A
    gigiaswitch config may provide what they are really trying to
    accomplish and that is to connect several FDDIs with firewall
    protection.
    
    Thanks for the time.
    
    greg_t