Re: [netmod] Question on intefaces-state model

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.

Lada

>
>
>
>  /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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