Conference 7.286::fddi

1658.0. "FDDI HUB900 dual homing config and DECnis bridging" by TLSE01::MIRGHANE () Fri Apr 21 1995 18:25

    We are proposing the following architecture for a big project
    where 54 Alpha/PCI machines must be connected using FDDI with high
    availability requirements. The computers are also linked together 
    with an Ethernet LAN.
    For this Each Alpha computer is linked using a PCI/DAS Interface to 2
    concentrators ( dual homing).   The total number of connection are then 
    2x54=108. We propose 20 DECconcentrators 900 mounted on 3 DEChub900:
    - The 1st DEChub900 contains 8 DECconcentrators 900
    - The second contains 8 DECconcentrators 900
    - The third contains 5 DECconcentrators 900, 1 PEswitch, 2
    DECrepeater 900TM.
    We plan to utilise port 1 and 6 of one concentrator per hub to connect
    to the next and precedent hub to make the ring. This utilizes 6 slots 
    for a total of 120 leaving enough connections for the 108 required 
    by the computers.
    We suppose that all concentrators on a given hub are connected to the 
    backplane FDDI link.
    The 2 repeaters  "DECrepeater 900TM" are utilised for the Ethernet 
    network and the PEswitch enables to bridge the Ethernet and the FDDI.
    
    Furthermore we need to bridge this FDDI network with 2 other FDDI
    networks in a redundant way. For this we propose 2 DECnis 600 each with
    3 FDDI boards; each board being connected with one of the FDDI network.
    In the case of the described net above we shall use port 1 and 6 of 
    of 2 concentrators to make the link to the 2 DECnis. The DECnis is
    assume to bridge the 3 networks filtering traffic but letting 
    broadcast messages go through it.
    
    
    
    
    Here are our questions:
    1/ Does the FDDI  configuration based on the 3 DEChub900 and the 20
    concentrators work?
    
    If not how should we do this configuration? Knowing that dual homing of
    the computers is a must.
    
    2/ Is the DECnis the right device to bridge the FDDI rings? Does it filter
    the local traffic. Will it let the boadscast messages through?
    
    3/ Will doubling the DECnis for high availability correct?
    
    Thanks very much for help.
                                   
    Soumetty.
     
    
    

    
    I can't tell from the note whether you want the modules in the hub to
    be configured in a ring or a tree. If it is a ring, then what you 
    are proposing can't be built with the Hub900. If the plan is to 
    connect the backplane via a tree, it sounds like it works, assuming 
    that the connections between the concentrators is a dual ring. If there 
    are any requirements for wrapping the ring within the backplane, you 
    need to be careful, as the trees (by their nature) can't wrap. 
    
    Since the design appears to be very high availability, I suspect that 
    there might be some more details of the hub to hub config that we
    need to discuss. 

    
    Sorry, I just noticed a point of mass confusion. When I said that the 
    connections between the cons is a dual ring, I meant the connection 
    between the hubs.