Re: [netmod] Question on intefaces-state model

On Tue, Jun 13, 2017 at 11:52 AM, Ladislav Lhotka <lhotka@nic.cz> wrote:

> Andy Bierman <andy@yumaworks.com> writes:
>
> > On Mon, Jun 12, 2017 at 10:21 AM, Juergen Schoenwaelder <
> > j.schoenwaelder@jacobs-university.de> wrote:
> >
> >> On Fri, Jun 09, 2017 at 10:55:20AM +0000, Bogaert, Bart (Nokia -
> >> BE/Antwerp) wrote:
> >> >
> >> > We have a question regarding the statistics container as defined in
> the
> >> > interfaces-state model.  This container defines one mandatory leaf
> >> > (discontinuity-time) while all other leafs are optional.  What is the
> >> > rationale behind this leaf being mandatory and not an optional field?
> >> >
> >> > It does not make a lot of sense to return a discontinuity-time value
> and
> >> no
> >> > counters if none of the counters are relevant for a specific
> interface.
> >> >
> >> > Another alternative could be to add, via a deviation, a when clause to
> >> the
> >> > container indicating for which ifType(s) the container is (or is not)
> >> > present. But that would lead to not supporting the IETF interfaces
> model
> >> to
> >> > the full extent.
> >> >
> >>
> >> The discontinuity-time is relevant for _any_ counter associated with
> >> an interface, regardless whether the counter is defined in the
> >> interfaces model or elsewhere. I have a hard time to imagine an
> >> interface that has zero counters.
> >>
> >>
> > The mandatory-stmt is very confusing for config=false nodes.
> Mandatory=true
> > means
> > an <rpc-reply> must contain an instance of the mandatory leaf.
>
> I don't think it is that confusing. RFC 7950 defines what a valid data
> tree means and "mandatory" are among the constraints.
>
> I agree though that in terms of a management protocol it means different
> things for config true and false data, but this is true also for default
> values and maybe other YANG concepts as well.
>
> >
> > Mandatory=false does not mean optional-to-implement although it sure
> > looks that way for config=false nodes.  Only if-feature can make a node
> > optional to implement.
>
> I don't think this interpretation is supported by any text in the YANG
> spec. State data nodes that are optional needn't be implemented.
>
>
RFC 7950, sec 5.6  (Conformance) does not support your interpretation.
It defines basic behavior, optional (via features), and deviations as the
only mechanisms affecting conformance.

Lada
>
> >
>

Andy

> >
> >
> >  /js
> >
> >
> > Andy
> >
> > --
> >> Juergen Schoenwaelder           Jacobs University Bremen gGmbH
> >> Phone: +49 421 200 3587         Campus Ring 1 | 28759 Bremen | Germany
> >> Fax:   +49 421 200 3103         <http://www.jacobs-university.de/>
> >>
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> --
> Ladislav Lhotka, CZ.NIC Labs
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>