At the last PMP discussion, I suggested that the references to the
System and Interfaces group of MIB II be removed from the printer MIB
RFC. Indeed, since the current draft includes the reference in the
text but not in the MIB itself, the requirement for inclusion is
unclear. It is preferable to remove this cumbersome and
inconsistently implemented reference than to leave it ill defined and
functionally useless. Indeed, the problems with using the MIB-2
referenced objects are reflected in the facts that:
1. the MIB-2 groups referenced in the printer MIB were not
considered sufficiently significant to include in the
interoperability testing, and
2. the printer identification and configuration functions
originally intended to be addressed by MIB-2 objects are now to be
handled by HRMIB objects and additional objects in the main body of the
printer MIB,
The consideration of the cases of:
1. the workstation or printserver box supporting multiple printers , and
2. the printer sporting more than one network interface
have rendered the MIB-2 groups unable to provide useful printer objects.
Although MIB-2 continues to be applicable to the network interfaces
themselves, the variables can not be guaranteed to be either unique (when
multiple printers share the interface) nor single valued (when a printer
has multiple network interfaces). The need for unique values has been
addressed by using more of the HR MIB objects, and by adding objects to the
systems section of the printer MIB. There has been little consistency in
the handling of the of the multiple NIC problem. (e.g., which sysUpTime
does one use for the printer alert time?).
Consideration of compatible implementation of the interfaces group has been
avoided. There are no guidelines on whether the listed interfaces include
host workstation (or print server box) interfaces, just printer interfaces,
or just printer network interfaces. In the case of multiple printers,
discerning local interfaces to each printer could be a real puzzle. And
many of the objects in the interface table are of very little interest from
a printer maintenance viewpoint
I therefore suggest that the Printer MIB remove a direct reference to
including the systems and interface groups of MIB -2. A comment to the
desirability to have each network interface support MIB-2 for itself is
recommended; but the intent of the MIB-2 objects as applied to the printer
is handled elsewhere in the HRMIB groups and the modified printer MIB.
Note that I am not blithely suggesting the elimination of objects; I am
generally opposed to doing this. Nor am I suggesting that MIB-2 not be
used; I would suggest a strong encouragement that all network nodes
providing input to a printer be supported with MIB-2. I am observing that
MIB-2 objects cannot consistently be used as printer specific objects, that
the need for MIB-2 objects in a printer context has largely been removed by
the use of HRMIB and Printer MIB objects, and that the remaining
association between the referenced MIB-2 objects and the printer can be
better handled elsewhere.
The following list of System Group and Interfaces Group objects indicates
the disposition of the purpose for which this object may have been
originally intended in the Printer MIB.
sysDescr hrDeviceDesc
sysObjectID hrDeviceID
sysUpTime * (see note 1)
sysContact prtGeneralServicePerson
sysName prtGeneralAdminName
sysLocation can be uncluded in prtGeneralAdminName
sysServices hrDeviceType
-- the Interfaces group
ifNumber Implicit
ifIndex unnecessary if interfaces are defined in conjunction
with channel table
ifDescr not applicable to printer
ifType include in channel table
ifMtu not necessary
ifSpeed not necessary
ifPhysAddress include in channel table where necessary
ifAdminStatus not necessary.. implicit in channel status
ifOperStatus not necessary.. implicit in channel status
ifLastChange not necessary
ifInOctets not necessary
ifInUcastPkts not necessary
ifInNUcastPkts not necessary
ifInDiscards not necessary
ifInErrors not necessary
ifInUnknownProtos not necessary
ifOutOctets not necessary
ifOutUcastPkts not necessary
ifOutNUcastPkts not necessary
ifOutDiscards not necessary
ifOutErrors not necessary
ifOutQLen not necessary
ifSpecific not necessary
* Note 1. sysUpTime. In a printer context, this gives not only the time up,
but also allows the alert event times to be related to a time of day. It
may be desirable to provide this elsewhere. Although the function could
still be served by the sysUpTime in the associated network node MIB-2 (s),
the present question of which one to use, if there are more than one,
remains.
The Interface group relates primarily to the channel group of the printer
MIB.
1. prtChannelIfIndex would no longer be applicable and would be either
deprecated or redefined to refer to a printer interface index inherently
defined by the channel table.
2. prtChannelInformation: The description states "information to allow a
printing application to use the channel for data submission to the printer"
I suggest that this be made self sufficient by also identifying the
applicable information about the interface used by that channel. This would
include the interface type enum (perhaps copping the enums from the
"evolution of the interface group MIB) and, as applicable, an identifying
address. MAC address might be good for ethernet and token ring interfaces
and is applicable to many non-IP print services listed under channels. IP
address is an alternate address appropriate to any internet interface.
Perhaps URL might be an appropriate address in the future.
I would appreciate comment on this proposal. If there is agreement, I would
volunteer to edit text sections of the RFC that would be affected.
Bill Wagner, Osicom/DPI