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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

1401.0. "AXP 3000-500 SAS-to-SAS connection without concentrator ?????" by 60600::STANISLAUS () Thu Jul 14 1994 02:03

	Can a 3000-500 FDDI card (I think it is called  a DEFTA) of one system
be directly connected to the same card of another 3000-500 system with no 
FDDI concentrators in between. 

	Is the above possible at all ? If yes does it depend on the drivers
and hence the Operationg System - OpenVMS/AXP or DEC OSF1 ?

ALphonse
T.RTitleUserPersonal
Name		DateLines
1401.1NPSS::CAUDILLKelly - Net Prod Support - 226-6815Thu Jul 14 1994 09:5525
    I think this has been covered in here before.
    
    Two stations can be connected "back to back" and thereby form a two
    station ring.  This is the minimal configuration and is perfectly valid.
    
    There are general issues with this configuration that may be confusing
    but don't really matter.  For example, if one station is not up (or its
    FDDI adapter is not initialized) the other station's FDDI adapter will
    not come up on the ring.  This is because, since it is a two station
    ring, both must be up for the ring to be up.  And if one is down, you
    can't talk to it anyway, so it doesn't matter that your connection to
    the ring is not up.  If you had a concentrator in this picture, the
    station that is up would be "up on the ring" but it still wouldn't have
    anyone to talk to if there is only one other station.
    
    Also, this "back to back" config is the only way to use full duplex.
    
    There were some problems in VMS where the driver was not initializing
    the adapter in the same way OSF was.  This meant that it was sometimes
    difficult to use a VMS system in a two station ring like this.  But
    that has been resolved.
    
    Note!  (baring GIGAswitch's new M-port support) plugging a station
    directly into a GIGAswitch (as opposed to into a concentrator which is
    plugged into a GIGAswitch) is a two station ring.
1401.2gigaswitch = fdxHOO78C::RIETKERKBart Rietkerk-Hoogeveen-HollandThu Jul 14 1994 10:049
    
    Some off-topic addition to .1 (couldn't resist)
    
    Add one and one to two and you'll see that system-gigaswitch-system
    also supports FDX.
    
    Just to be complete.
    
    Bart Rietkerk.
1401.3koning.lkg.dec.com::koningPaul Koning, B-16504Thu Jul 14 1994 12:519
Right.  That's because each Gigaswitch port is a separate FDDI interface,
so each separately can be connected to one other station for a two-node
ring (FDX capable) or a larger ring (not FDX capable).

For the ultimate performance, you could have a fully loaded Gigaswitch
(34 (?) ports), each connected to one station, every one of them running
full duplex.

	paul