Conference 7.286::fddi

    We're looking at building an FDDI-FDDI bridge as you suggest, but its
    not just another configuration of a DECbridge 500 that you can order.
    The DECconcentrator can be configured with different boards in place
    when ordered, but the bridge (today) comes "as is", with one Ethernet
    port and one FDDI port. The modular design is so when we DO build a
    100-100 bridge, we might be able to upgrade existing bridges by
    swapping out the Ethernet card for and FDDI card and swapping out the
    processor for a faster processor but more likely, it will just make it
    easier to manufacture as a specific configuration.
    
    Today, the recommended way to link two FDDI rings together is to use an
    Ethernet segment as a go-between with a DECbridge 500 on either side.
    
    Debbie
    

    
    Thanks Debbie.
    
    The problem with the "interim" solution is that it limits the link
    bandwidth somewhat, thus only useful for limited traffic etc.
    
    Do you have any feel for when the 100-100 local bridge might hit the
    streets ? My customer is looking to procure around mid-'91 - the
    project is the subject of a "Technical Design Study" at the present.
    Is this information included in a new PID (updated since the product
    launches) for FDDI ? 
    
    Obviously anything I can add into this project "design" will be useful
    to help us win the bid.
    
    Rog

    Rog,
    We're looking at a n10-100 bridge first (mulitple Ethernets
    to 1 FDDI ring) first. A 100-100 bridge would come after that. This should 
    be part of the new PID which is supposed to be available by the end of 
    this month. I don't know if you can change this schedule at all but the 
    product manager for the bridges is Jim DELNI::CAPOBIANCO. You might want 
    to contact him for further info or to present your customer's requirements 
    to him.
    
    Debbie
    
    

    One other thing.....using Ethernet as an interim solution might not be
    as bad as you think considering the only traffic that would use it
    would be traffic destined for the Ethernet anyway or traffic that had
    to reach the other ring. With careful network plaaning and design, this
    could me minimized so the reduced bandwidth in the middle wouldn't
    necessarily be a problem.
    
    Debbie
    
    

What ever happened with this?  Do we yet offer a FDDI-to-FDDI bridge?

Thanks!
tl

Don't think we can discuss unannounced products in a notesfile,
but keep your eyes open for a program announcement at DECworld.
Also look for the April 13 issue of Sales Update.

>Don't think we can discuss unannounced products in a notesfile,
>but keep your eyes open for a program announcement at DECworld.
>Also look for the April 13 issue of Sales Update.

	Well, I just looked in the april 13 issues and I
	did not see anything about and fddi-fddi bridge...

	What I am looking for are two end to end bridges
	that can do fddi and also bridge in 10mbs on each
	side.  Do I have to get decbridge 600s to do this?

thanks
ort1

    It sounds like you need two DECbridge 62x or 52x, depending on how many
    Ethernets you want to bridge on to the FDDI ring. This config looks
    like:
    
          Ethernet  Ethernet    Ethernet
            \         |           /
             \        |          /
              \       |         /
                 DECbridge 62x
                    ||   ||
                    ||   ||  FDDI Ring
                    ||   ||
                 DECbridge 62x
                /      |       \
               /       |        \
              /        |         \
        Ethernet  Ethernet    Ethernet
    
    
    Is this what your customer wants? If not, replace the FDDI ring between
    the two bridges with a GIGAswitch with concentrators from each of the
    two rings you want to bridge together connected to it. Then put the
    DECBridges on the other rings or connected to the concentrator.
    
    Debbie
    

	Thanks for the reply!!!

	So, this is the configuration that should work...


                   Ethernet
                      |    
                      |    
                      |    
                 DECbridge 528
                    ||   ||
                    ||   ||  FDDI Ring (single mode)
                    ||   ||
                 DECbridge 528
                       |    
                       |    
                       |    
                    Ethernet
    


	And this configuration would NOT work...


                   Ethernet
                      |    
                      |    
                      |    
                 DECbridge 518
                      ||
                      || (not really a ring, single mode)
                      ||
                 DECbridge 518
                       |    
                       |    
                       |    
                    Ethernet


thanks a ton
ort1

    Ort,
       Somewhere else in this conference Paul Koning discusses hooking up
    two S-ports back-to-back as you show in your second config. This is a
    legal config, but isn't redundant in any way, nor is it expandable. So,
    while it would work, it isn't a very practical solution. The first
    config that I drew using the 528s would be a more reasonable solution.
    
    Debbie
     

	Thanks:

	I did a dir/author on koning, and alot of his notes
	don't have a title, do I'll have to look as all of his
	notes when I get a chance.

	Due to the price sensitive nature of this project to
	the customer, we will use the "lesser" solution.  There
	will be backup fiber incase of a fiber loss.

	thanks again.
ort1

It's fine to point out the non-expandable nature of SAS-SAS connections,
but a blanket negative such as "not practical" is NOT correct.  For situations
where the limitations are acceptable -- and there are several such -- the
SAS-SAS configuration is legal, supported, AND practical.

	paul

    I realize that S-S connections are okay, legal and supported.  In fact
    the GIGAswitch will have only A, B and S ports (its not a concentrator)
    so S-S connections will be common.
    
    Some of the confusion regarding the legality of S-S connections may be
    caused by the wording in the  FDDI System Level Descvription
    (EK-DFSLD-SD-001) pg. 2-20 last bullit,
    
    	"Port S - connects a SAS to a CON.  Can also connect to a DAS or
    		  another SAS, but these configurations are not
    		  recommended."
    
    We should probably describe the limitations and strike out the not 
    recommended statement.
    
    /bill

The same wording occurred in a draft of rev 2 of the FDDI Primer, but it was
corrected just before publication.  So at least one place has it fixed...

	paul