Conference netcad::hub_mgnt

2671.0. "Framing Errors and Block Check Errors - How many permissable ?" by GIDDAY::STANISLAUS () Wed Aug 23 1995 23:58

	Also posted in Ethernet conference:
	-----------------------------------

	If I receive a total of "N" frames on a device (say DECbridge 90FL)
and have "X "framing errors plus "Y block check errors then (X+Y)/N converted to
a percentage say equals 0.1 percent, is that acceptable. I can't see figures
on this. Is there an IEEE spec on this.

	In the Network's Troubleshooting guide there is a helpful thumb-rule
that says Frames Sent Initially Defered Plus Single Collision Count Plus
Multiple Collision Count Divided By Total Data Blocks Received should be less
than 10%. I am looking for a similar thumb-rule for the receive errors.

	What we have is a customer with lots and lots and lots of DECrepeater
90FL repeaters with each of its ports connected to DECbridge 90FL bridges
at a remote site. We are talking about 100 DECrepeater 90FLs and about 300
or so DECbridge 90FLs, since not all DECrepeater 90FL ports at all sites are
used.

	This customer has a person dedicated to do the following:

	Come into the office everyday connect to every DECbridge 90FL using
MC NCP CONNECT VIA CIRCUIT circ-id PHYSICAL ADDRESS 08-00-2B-xx-xx-xx and at the
DECbridge 90's prompt show port 1 counters to see the number of errors on the
DECbridge 90FL port. If he gets a few Block Check Errors or Framing Errors, he
forces Field Service to change the DECrepeater 90FL, because all the DEcbridge 
90FLs connected to that DEcrepeater 90FL at that site logs errors. Field service
may get a DECrepeater 90FL that may fix the problem fully, or reduce the number
of Block Check Errors and Framing Errors on the remote DECbridge 90FL or may
show no difference to the original DEcrepeater 90FL. If Field Service keeps
trying 3 or 4 new DECrepeater 90FLs, they may get one with zero or very low
Block Check Errors and Framing Errors logged by the remote DECbridge 90FLs. This
site is consuming about 2 or 3 DECrepeater 90FLs every week. These DEcrepater
90FLs are in DEChub 90s with DR90T, DR90T, DECbrouter 90FL, DS90TL, etc.

	So I would like to get a specification on how many of the above errors
are permissible. I do understand there is fibre involved and losses in the fibre
splicing and ST connectors may all contribute to the problem.

	The question is, whether F/S is trying to fix something that is not
broken. If we can get some numbers on permissible receive errors then we can 
say whether we are trying to fix something that is not broken.

	I got seriously involved with this last week and I have asked F/Service
to send me a few of the replaced DR90FL to see if they are really broken.

	Also please see note 2304 in this conference.

	All DB90FL bridges are running S/W ver 3.9

Alphonse

    100 repeaters and 300 bridges?  what is the size of this LAN?
    
    what kind of traffic levels do you see?  5% 10% 30% ?
    
    ken