Subject: PMP> 1: More on Toner Low/Critical or Warning ??\n2: Host Resources/Printer MIB status conflicts.

From: [email-masked] (peter smartt)
Date: Fri, 9 May 1997 11:36:11 +1000

2: Host Resources/Printer MIB status conflicts.

I would also like to throw in my opinion, as someone who has just joined
the group.  I have been working on an agent implementation for the last
couple of months, and we develop controllers for a number of different
(mostly Japanese) Laser Printer manufacturers.

I think a big part of the problem is that different engines (and
controllers) handle the toner low condition differently. Some cause the
printer to stop immediately, and some just carry on trying to print, but
put a warning message up on the console. Some printers don't even
differentiate between Toner Low and No Toner, and some do, causing
printing to stop (and sometimes the printer goes "Offline". I think
everyone probably has a slightly different concept of what to tell the
SNMP manager when one of these conditions occurs, depending on what their
printers do.

Anything that stops the printer from printing should cause a critical
alert (and thus a trap), so that Bill Wagner's idea of having 2 alerts
(one for Toner Low and another for Off Line) is probably workable.
But some printers stop printing without actually going "Offline" (a dated
concept in my opinion), and it would not be immediately obvious to the
Manager why the printer had suddenly gone offline and what action is
required. So I suggest that a way ahead might be to have an alert conditon
something like "lowTonerPreventsPrinting", which would be critical, and a
warning alert "lowToner". The agent would then implement whichever alert
is appropriate for its own machine, as it would probably be inconsistent
to implement both. The manager could then understand what is going on
unambiguously (possibly the wording could be changed to accomodate printers
that differentiate between Low Toner and Toner Out (or Replace Toner)).

While on the subject of Toner Low, I had a lot of trouble knowing how to
implement prtMarkerSuppliesLevel. I don't know of any devices that can
measure how many tenths of grams of toner are remaining, but a lot can tell
if there is still plenty, "Toner Low" and "Toner Out". Would it be possible
to add a value (-4) indicating that the printer has detected the "Toner Low"
condition.

Concerning conflicts with the Host Resources MIB objects, one of the
fundamental SNMP principles is that

	"No object should provide information that could have been
	 deduced from other objects."

To give information that may be IN CONFLICT with information that can be
deduced from other objects would seem to be MUCH worse. Is it socially
acceptable in the SNMP world to ask the Host Resources people to deprecate
the hrPrinterStatus and hrPrinterDetectedErrorState objects?? As Jay Martin
pointed out, hardly any (if any) hr applications implement any printer
objects, and that in itself should be enough reason to deprecate them.
But the fact that we can provide a much more accurate description of the
state of the printer should also be a good reason.

If they can't deprecate these items, then lets hope we don't have to separate
completely from the HR MIB.

I hope you will take all this into account in San Diego. I doubt whether I
willl be able to attend many meetings, unless you decide to have them in
Sydney.

Best reagrds,

Peter Smartt.

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Peter Smartt                       |    Email:  [email-masked]
Pacific Semiconductor Pty Limited  |    Voice:  +61-2-9956-5211
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