Conference 7.286::fddi

1378.0. "DB520 resets on long jabbers..." by DPDMAI::DAVIES (Mark, SCA Area Network Consultant) Tue Jun 14 1994 18:41

    
    One of Digital's few remaining "all DEC" shops just gave me a call
    concerning their FDDI and Ethernet LAN they have had for a few years. 
    It is a FDDI ring composed of 1 DECconcentrator 500 and 1 DECbridge 520. 
    The DC500 has 4 FDDI workstations and the DB520 connects to the
    Ethernet world of about 500 system.
    
    They tell me that, generally speaking, the DB520 only stays alive for
    ~48 hours before it will crash and reset itself.  They have discussed
    this with the Support Center and got essentially no useful help (they
    had never heard of this problem and didn't know what to recommend).
    
    The folks from Cisco want to break-in to this account, so they loaned
    these guys a Cisco router with a FDDI port and 8 Ethernet ports.  They
    removed the DB520 and guess what;  the Cisco crashed/reset also, never
    staying alive much more than 48 hours.  SO, Cisco sent out some LAN
    analysis type folks and they say they found "long jabbers" on the
    network.  They then proceeded to adjust some timers on the Cisco unit
    and the Cisco router has NOT crashed since.
    
    Now, as a test, they re-inserted the DB520 and connected a single
    ethernet to it.  This particular ethernet segment has 4 VAXstations and
    4 PCs on it.  The DB520 has been up and running now for 5 days and is
    setting records.  The problem is that it will crash if we go back to
    the original setup.
    
    Looking at all this lends me to believe that the problem (jabbers or
    whatever) exist on the Ethernet side of the LAN and that the DB520
    cannot deal with it and resets itself.  
    
    MY QUESTION:  Is it a known problem that long jabbers or other
                  abnormalities will cause the DB520 to reset itself?
    
    		  If so, is their a fix and a timer that can be adjusted
                  to make it play in this environment?
    
    These folks went to Interop and DECUS and actually got to play with
    HUBwatch and the new DECbridge 900MX.  They want to get one of
    these units to further segment their network, but they have concerns that
    the same problem will exist and they will make a bad situation worse.
    
    If we cannot give them some help, Cisco is in and starts taking
    business from us.
    
    Any assistance on this is appreciated.
    
    Thanks,
    
    Mark
                                                                       

I don't know about the 520, but that problem very definitely should NOT exist
on the 900.  (The relevant code has nothing in common with the 520; that may
help as an argument for the customer.)

Note, however, that long jabbers are a sign of some sort of network problem
and deserve to be looked at & fixed.

	paul