Conference 7.286::fddi

474.0. "fddi and nfs problems?" by CSC32::D_LOWRY () Mon Feb 10 1992 13:18

    A short while back, some folks asked for some nfs performance
    numbers on fddi, did anyone ever get anything on this?
    
    I have some strange happenings between a 5000 using the FDDI
    i/f and a decstation 3100.  I can issue the mount command from
    the decstation, getting the files from the 5000.  The files get
    mounted okay, as evidenced by the mount command.  The problem is
    that when changing directories to one of the subdirectories, being
    exported and then doing a directory listing, the system gets a
    server not responding.  
    
    Between 2 FDDI systems, there is no problem doing this.  I can't
    understand why this would happen.  There is no tcpip problems,
    that is telnet and ftp and even something as low level as ping
    work fine between all systems.
    
    Any help would be appreciated.
    
    This also crossposted in Ultrix Notes.
    
    Dan Lowry
    

    If you get no response, try contacting Alex Conta - he works on UCX.
    Of course, onlay call Alex if you are using UCX.

    Turn on IP fragmentation in the bridge.

    As .2 indicates, the problem is caused by NFS using larger than 1500
    byte packets.  Since NFS runs on top of UDP which doesn't know about
    MTU restrictions, packets get dropped by the bridge since they
    don't fit on Ethernet.  However the DECbridge performs IP fragmentation
    if the switch is turned on (it's off by default I think).  (there's a
    competitive advantage for the sales folks out there.. no other
    FDDI to Ethernet bridge on the market has this feature!)
    
    Anil

Is it STILL off by default?  That should be changed...

	paul

    I wasn't sure so I checked, and it _is_ on by default!  So this may
    be some other problem after all.
    
    To the base note author: you may want to check anyway just in
    case it had been turned off.
    
    Anil