Path: utzoo!attcan!uunet!husc6!bu-cs!kwe
From: kwe@bu-cs.BU.EDU (kwe@bu-it.bu.edu (Kent W. England))
Newsgroups: comp.dcom.lans
Subject: Re: status lights on lan equipment
Message-ID: <23457@bu-cs.BU.EDU>
Date: 21 Jun 88 15:19:10 GMT
References: <5808@dcatla.UUCP>
Reply-To: kwe@buit13.bu.edu (Kent England)
Followup-To: comp.dcom.lans
Organization: Boston Univ. Information Tech. Dept.
Lines: 55

In article <5808@dcatla.UUCP> dnwcv@dcatla.UUCP (William C. VerSteeg) writes:

>The consensus on lights vs. no lights on lan equipment seems to be
>overwhelming in favor having status lights.
>
>Box status indicators
>_____________________
>Power on indicator
>Box running/loading indicator
>
>
>
>Interface status indicators
>___________________________
>Receive Data
>Transmit Data
>Media Error (i.e. Collisions, no Carrier, etc)

I think you also need:
SQE (Heartbeat) enabled

	There is a difference in what is required for bus versus star
topology Ethernet.  As an example, Cabletron defines 5 status lights
for a bus transceiver: Power, Receive, Transmit, Collision, SQE
enabled.  All of these are very useful for bus transceivers:
	Power=  is this transceiver plugged into anything?
	Rcv/Xmit=  is data flowing both ways?
	Collision= are there too many collisions (get the analyzer)?
	SQE=  do I have a problem with heartbeat (on a repeater)?

	For star topology (UTP of fiber) they define two more signals
for the point-to-point MAU to concentrator [not IEEE jargon]:
	Host Link OK
	Hub Link OK

	These signals are not data signals.  They indicate a good or
bad circuit and may eliminate the need for TDRs, special analyzers or
breakout boxes.  If Link OK not lit, then find the open or crossed
circuit.  Very, very useful.

	When forced to eliminate all but two lights on hub
concentrators and MAUs, Cabletron chose to keep Link OK and Rcv.
Seems reasonable to me.

	One more thing.  It's very very important that vendors
implement the IEEE repeater fault protection functionality.  Just
because they spec 802.3 compatible doesn't mean they implement the
fault isolation feature= make sure they implement the fault isolation.
Isolation is based on too many consecutive collisions or jamming and
provides for automatic recovery.  You really need this feature to
isolate hardware faults and to allow you to unplug things for
debugging.  I am not sure of existing vendor compliance, but I think
most of the star concentrator equipment will have this feature.

	Kent England, Boston University