[Search for users] [Overall Top Noters] [List of all Conferences] [Download this site]

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

1151.0. "MAC lost count meaning" by KERNEL::WEBSTERC () Wed Nov 17 1993 05:54

    
    	A customers ring consists of a couple of 3COM hubs with a
    	concentrator in each, hooked up as a dual ring. On each hub
    	is an FDDI M port card, and hanging off of these is
    	3x vaxs with demfa's and 2x cisco ags's.
    
    	The demfa's are clocking up ~ 2 / min "MAC lost count"
    
    	I have had a look at the ansi spec, which says "....an error 
    	is detected such that the credibilty of PDU reception is placed 
    	in doubt..."
    
        can anyone explain exactly what this means
    
    	Thanks in advance
    
    	Colin
T.RTitleUserPersonal
Name
DateLines
1151.1KONING::KONINGPaul Koning, B-16504Wed Nov 17 1993 15:2113
Yes, nice cryptic description...

The real meaning: "lost count" is incremented when a non-data symbol, other
than a valid termination, is encountered in the middle of a frame.

(For example, an R symbol in the middle of data will cause this.  Idle does
not; that's a "fragment" which is not counted, and is normal.)

Possible causes include bit errors on the wire, or defective stations.  Examine
the LEM counters to see if it's bit errors, and fix the offending connection
if so.

	paul