Re: [netmod] Comments on NMDA-04

Robert Wilton <> Thu, 14 September 2017 17:02 UTC

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To: Balazs Lengyel <>, Martin Bjorklund <>
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From: Robert Wilton <>
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Date: Thu, 14 Sep 2017 18:01:52 +0100
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Subject: Re: [netmod] Comments on NMDA-04
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Hi Balazs,

Thanks for the review and comments.

On 14/09/2017 16:44, Balazs Lengyel wrote:
> See below !
> On 2017-09-14 16:32, Martin Bjorklund wrote:
>>> CH 4.4.)  "Validation is performed on the contents of <intended>."
>>> This to me means that default data is not considered at validation
>> Note that RFC 7950, section 6.4.1, says:
>>     In the accessible tree, all leafs and leaf-lists with default values
>>     in use exist (see Sections 7.6.1 and 7.7.2).
>> So defaults are taken into account when intended is validated.
> BALAZS: Yes the two seem to contradict each other. This can be 
> understood in your way, however the current text is not clear enough. 
> I would add:
> Validation is performed on the contents of <intended> (EXTENDED WITH 
As an alternative suggestion, rather than saying contents of <intended>, 
we could instead say something like "<intended>must always be a valid 
configuration data tree.". Is that better?  I would rather not talk 
about "defaults for <intended> since that may imply that they are not 
applicable to other configuration datastores".  E.g. if <running> is 
validated then you would also expect defaults to be considered. Ditto 
for startup, candidate.


>>> which would be a backwards incompatible change. Also if validation
>>> does not consider system configured data that would allow cases like
>>> multiple interfaces named lo0. One from <intended> one from system
>>> configuration. IMHO while it is OK to violate uniqueness because of
>>> remnant data, the above violation of uniqueness seems a bad idea.
>> If your system adds data to <running>, or to <intended>, it will be
>> validated.
>>> Ch. 4.7) Is it allowed to violate uniqueness of key values? IMHO it
>>> should not be.
>> Agreed.  Note that the draft explicitly lists the constraints that can
>> be violated, and uniqueness of keys is not listed.
> BALAZS: If that is the intent I would propose to explicitly state it. 
> For me it was non-trivial.
> Can a a choice statement be violated? Having to existing branches at 
> the same time? It seems a semantic constraint to me. IMHO yes.
> Can an if-feature be violated? If  support has just changed and we 
> have some remnant config, I can very well imagine it violated.
> Also here could you change
> If a node in  <operational> does not meet the syntactic constraints 
> then it cannot   be returned
> to
> If a node in  <operational> does not meet the syntactic constraints 
> then it MUST NOT be returned
>> /martin