Re: [netmod] OpsState Direction Impact on Recommended IETF YANG Model Structure

[Robert Wilton <[e-mail]>]

Hi,

So after the various meetings and discussions this week, I think that 
the most important thing for IETF to do is to publish reviewed YANG 
models quickly, with the understanding that it is better to publish 
imperfect models than to end up not publishing any models at all.  This 
is with the understanding that these models could be fixed by subsequent 
RFCs if required.

So, I effectively support Acee's solution (2).  But to state this more 
precisely, I would suggest that the specific guidance should be:
1) IETF Models MUST NOT have a split for applied configuration leaves.  
All IETF models that have not been turned into RFCs must be modified to 
remove any applied configuration nodes.  Any models that have this 
convention in RFCs should be revised to follow a consistent 
intended/applied convention for IETF models.  [The justification here is 
that IETF standard models have to be able to assume that the applied 
configuration will be available via a separate applied configuration (or 
operational state) datastore or equivalent mechanism.]
2) All IETF Models MUST put "derived state and statistics" into a 
separate namespace from the configuration (i.e. top level "feature" and 
"feature-state").  The two trees must be as structurally similar as 
possible, sharing the same paths, node names (except the top level 
node), using the same lists keys where appropriate, etc.*
3) Both of these rules should be written into rfc6087bis.  We should 
then get this guidelines document finished as quickly as possible at the 
highest priority, and use that as the definitive guideline for the 
modules that the working groups are working on.

* Note, I chose this option not because I think that it is elegant 
(because I don't) but because it seems to me that it is the only 
pragmatically option that we have available.  The alternatives appear to 
be: (i) we wait another year before publishing any models (if ever), or 
(ii) we publish models that no-one can use today without violating the 
existing RFCs, or (iii) we end up with a hybrid mess without any 
consistency.

Thanks,
Rob


On 11/07/2016 18:36, Acee Lindem (acee) wrote:
> While there are details to be worked out between the two data stores
> models (as indicated below), we now have implicit modeling of applied
> configuration. Existing models (both standard and draft) do not take this
> into consideration and, consequently, much of the state that is modeled
> explicitly represents the application configuration. For the RFC models,
> it probably doesn’t make much sense to redo them (unless they are being
> reworked for other reasons). This still leaves the existing WG draft
> models for which we have basically 3 options:
>
>    1. Do nothing - allow them proceed as they are with multiple ways of
> representing the applied configuration. This would provide visibility to
> the data independent of whether or not the device supported the revised
> data-stores supporting implicit retrieval of the applied configuration.
>    2. Prune out the redundant data nodes except those required as list
> keys, etc, since they can be obtained from the applied state data store.
>    3. #2 plus collapse the config (read-write) and  system-state
> (read-only) into common containers. No more branching of
> <model-name>-config and <model-name>-state at the top level of the model.
>
> At I high-level, I feel these are the options. I’m not married to any one
> of these and the worse thing we could do is hold up progression of the
> existing YANG model drafts for another couple years while we debate the
> best course. Having said that, #3 is compelling since it will yield the
> most concise models and colocates the schema data nodes for any managed
> object.
>
> Thanks,
> Acee
>
> On 7/1/16, 12:36 PM, "netmod on behalf of Lou Berger"
> <[e-mail] on behalf of [e-mail]> wrote:
>
>> All,
>>
>> It's time to make a consensus call on this topic, so that we can all move
>> on to defining a solution and aligning modules under development. Based
>> on the feedback received and the overall discussions on the topic, we see
>> that there is consensus to follow a datastore based approach to
>> supporting operational state, i.e., direction 'B'.
>>
>> We will be asking the authors of [4] and [5] to review their proposals
>> (individual drafts) in Berlin, as well as to highlight differences and
>> suggest ways that their work could be consolidated. Of course, others may
>> also choose to submit their own proposals. Given the importance of this
>> work, we will be looking to have active discussion on the topic both in
>> Berlin and on the list, with an objective of having a draft ready for
>> considerations as a WG document by the November IETF.
>>
>> We have reviewed this decision with our AD and the NetConf chairs and
>> have agreed to begin this work in NetMod. We certainly expect to
>> coordinate the work with the NetConf WG and re-home work as/if needed.
>>
>> Finally, we'd also like to thank all those who have contributed to this
>> discussion to date, from problem identification to proposed solutions,
>> and we look forward to your continued efforts to publish a standard
>> solution.
>>
>> Lou (and Kent)
>>
>>
>> On 6/7/2016 10:19 AM, Lou Berger wrote:
>>> All,
>>>
>>> We want to provide an update based on the off line discussions
>>> related to OpState Solutions that we have been having and solicit
>>> input from the WG.
>>>
>>> All authors of current solution drafts [1,2,3] together with those
>>> who helped conduct the solutions analysis* were invited to the these
>>> discussions -- with the objective of coming up with a single
>>> consolidated proposal to bring to the WG. (I/Lou acted as facilitator
>>> as Kent and Juergen were and are involved with the technical details.)
>>>
>>> The discussions have yielded some results but, unfortunately,
>>> not a single consolidated proposal as hoped, but rather two
>>> alternate directions -- and clearly we need to choose one:
>>>
>>>      1) Adopt the conventions for representing state/config
>>>         based on Section 6 of [1].
>>>
>>>         From a model definition perspective, these conventions
>>>         impact every model and every model writer.
>>>
>>>      2) Model OpState using a revised logical datastore definition
>>>         as introduced in [4] and also covered in [5]. There is
>>>         also a variant of this that we believe doesn't significantly
>>>         impact this choice.
>>>
>>>         With this approach, model definitions need no explicit
>>>         changes to support applied configuration.
>>>
>>> >From a technology/WG standpoint, we believe an approach
>>> that doesn't impact every model written (i.e., #2) is superior.
>>> The counterpoint to this is that the conventions based
>>> approach (i.e., #1) is available today and being followed in
>>> OpenConfig defined models.
>>>
>>> We would like to hear opinions on this from the WG before
>>> declaring one of the following as the WG direction:
>>>
>>>      A) models that wish to support applied configuration MUST
>>>         follow conventions based on [1] -- and the WG needs to
>>>         formalize these conventions.
>>> or
>>>      B) no explicit support is required for models to support
>>>         applied configuration -- and that the WG needs to
>>>         formalize an opstate solution based on the approach
>>>         discussed in [4] and [5].
>>>
>>> We intend to close on this choice before Berlin.
>>>
>>> Thank you,
>>> Lou (and co-chairs)
>>>
>>> [1] https://tools.ietf.org/html/draft-openconfig-netmod-opstate-01
>>> [2] https://tools.ietf.org/html/draft-kwatsen-netmod-opstate-02
>>> [3] https://tools.ietf.org/html/draft-wilton-netmod-opstate-yang-02
>>> [4]
>>> https://tools.ietf.org/html/draft-schoenw-netmod-revised-datastores-00
>>> [5]
>>> https://tools.ietf.org/html/draft-wilton-netmod-refined-datastores-00
>>> * - Chris H. and Acee L.
>>>
>>>
>>> _______________________________________________
>>> netmod mailing list
>>> [e-mail]
>>> https://www.ietf.org/mailman/listinfo/netmod
>>>
>>
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