Hi -
My recollection is that part of the motivation for the use of
zero-length strings as sentinel values in situations like this
in MIB modules (rather than skipping the object instance) was
to permit a clear distinction between "information not available"
and "access denied".
Randy
On 12/15/2016 7:21 AM, Juergen Schoenwaelder wrote:
I do not think the goal should be to emulate SMIv2 compliance levels
using features. So I propose to do nothing about entity4CRCompliance.
The other question (which should perhaps have been a separate issue)
is whether non-existing values are indicated by zero-length strings or
non-existing objects. I think in general we prefer to simply not
report those objects in the YANG world. If so, I am not sure whether
the goal to not depart too much from the ENTITY-MIB overrules
this. Note that there are a couple of objects where non-existing
values lead to zero-length string or other special values. (The
'alias' description is kind of interesting - the server may set the
value of this node to a locally unique value; entPhysicalAlias says
something different, namely On the first instantiation ... is set to
the zero-length string.)
Looking at the YANG fragment, I am also not sure how useful it is to
carry the 32 'something' restriction forward. Note that 32 means
unicode characters in YANG but space of the UTF-8 encoding of
characters for SMIv2 (since it all ends up being a restriction for the
OCTET STRING). Perhaps this deserves a feature, namely, whether an
implementation supports flexible names or restricts names according to
the SMIv2 ENTITY-MIB rules.
/js
On Thu, Dec 15, 2016 at 04:01:10PM +0100, Martin Bjorklund wrote:
Hi,
Issue https://github.com/netmod-wg/entity/issues/11
RFC 6933 introduced a new compliance level for constrained resources
- entity4CRCompliance. Do we need a corresponding feature?
In YANG, we cannot to the equivalent of compliance levels, so we would
need to mark all nodes with some optional feature, except the few
nodes that a constrained device would implement.
OTOH, most nodes are already optional and config false. So a
constrained server that doesn't know the serial number for example
could just no return it. There is one catch though; the current text,
copied from the MIB, says e.g.:
If the manufacturer name string associated with the
physical component is unknown to the server, then this
node will contain a zero-length string.
Maybe we should change this so that the object isn't returned at all
instead of returning a zero-length string.
/martin
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