Re: [netmod] [Technical Errata Reported] RFC8342 (5514)

Lou Berger <lberger@labn.net> Mon, 08 October 2018 16:34 UTC

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To: Robert Wilton <rwilton@cisco.com>, Andy Bierman <andy@yumaworks.com>, Ignas Bagdonas <ibagdona@gmail.com>, NetMod WG <netmod@ietf.org>, Warren Kumari <warren@kumari.net>, RFC Errata System <rfc-editor@rfc-editor.org>
References: <20181005094808.A049EB800AE@rfc-editor.org> <20181005101427.bw7qo7ertxk2dj5d@anna.jacobs.jacobs-university.de> <1b34ccac-831f-505d-d40b-c21234efc475@labn.net> <20181005142816.avs2es2ymvc7qxwx@anna.jacobs.jacobs-university.de> <2e2f0188-770c-5fad-6a9d-a0be3abd1fce@labn.net> <CABCOCHS4GOVYC0FRJEtCpzQ+VB=u6g0LDEmL1ULqysBA=yhzNg@mail.gmail.com> <20181007064721.i4gfbmhrldvmtgbz@anna.jacobs.jacobs-university.de> <CABCOCHTZMabKuu-T4mGAwiaeWDpSWZopFB42W8A+u7g6ZvRg7w@mail.gmail.com> <20181007170907.23ussvtcds7ftnab@anna.jacobs.jacobs-university.de> <973c0b2d-cc42-fdc6-d405-dd7e561a37a3@cisco.com> <0073d57d-217d-3fff-54c3-7f0cf062c0cc@labn.net> <cd75f603-90bb-72dd-434b-6022856495ba@cisco.com>
From: Lou Berger <lberger@labn.net>
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Date: Mon, 8 Oct 2018 12:02:14 -0400
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Subject: Re: [netmod] [Technical Errata Reported] RFC8342 (5514)
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Hi Rob,


On 10/8/2018 9:51 AM, Robert Wilton wrote:
> Hi Lou,
>
>
> On 08/10/2018 13:57, Lou Berger wrote:
>> Hi Rob/All,
>>
>> Keep in mind that the document says what it says and that to change
>> text really requires a new version.
>>
>> On 10/8/2018 6:01 AM, Robert Wilton wrote:
>>> So there seem to be two available solutions here:
>>>
>>> (i) The server MUST provide an origin value for the top level datanode,
>> This is pretty close to what Andy previously quoted:
>>
>>       md:annotation origin {
>>         type origin-ref;
>>         description
>>           "The 'origin' annotation can be present on any configuration
>>            data node in the operational state datastore.  It specifies
>>            from where the node originated.  If not specified for a given
>>            configuration data node, then the origin is the same as the
>>            origin of its parent node in the data tree.  The origin for
>>            any top-level configuration data nodes must be specified.";
>>       }
>>
>>
>> I think it's clear that the reviewers, notably myself as shepherd,
>> missed that this is a lowercase "must" and should have asked for
>> clarification during the review process.
> So I think that the logic for it being must rather than MUST is that it
> is in a YANG module, and we didn't want to tie the YANG module to RFC
> 2119 language.
I'm not sure this is a great argument.  Using conformance language in 
such cases maybe exactly what is needed - but this is a different 
discussion.


>
>> Having an errata saying this "must" really is a "MUST" is quite
>> reasonable from my perspective.
> I'm not convinced that this has to change.
>
>>> but for NP containers it can use whatever origin value it likes - since
>>> the origin value imparts no direct meaning other than the default origin
>>> that descendants acquire if they haven't provided an explicit origin.
>>> In this case we would probably add a line of text to clarify this
>>> behavior of choosing a suitable origin value for top level NP
>>> containers.
>> I guess I'd need to see that specific language to understand if a new
>> requirement or recommended behavior is being prescribed.  If it is, we
>> need a new document to do so.
> The additional sentence (added at the paragraph above) could be
> something along the lines of:
>
> "For top level nodes that are non-presence containers, where the origin
> has no direct meaning other than as a hierarchical default origin, the
> server may choose any convenient origin value".
>
> But equally, perhaps the existing test is sufficient without requiring
> any changes at all.

I agree, it's not clear that this change is need as it is *already* what 
is allowed.
> Then the errata that is required is the one that
> Rohit submitted.
so the errata should be corrected

Lou

>
> Thanks,
> Rob
>
>
>>> (ii) The requirement is weakened as Juergen has described previously.
>>>
>>>
>>> Solution (i) minimizes the impact of the change to the RFC, but probably
>>> constrains server implementations slightly more than is strictly
>>> required.
>>>
>>> Solution (ii) gives a bit more flexibility to server implementations but
>>> in theory could break client implementation that rely on a top level
>>> origin always being provided.  Although, in reality I would expect a
>>> robust client implementation to either not care, or choose a suitable
>>> default origin (e.g. "unknown") if an explicit origin hasn't been
>>> provided.
>>>
>>> If solution (ii) is beyond the scope of what is allowed in an errata
>>> then it would seem that we should go with solution (i) instead. But how
>>> do we get to a final decision?
>> Either we agree that s/must/MUST in an errata or start a new (update
>> or bis) draft  to update the behavior.  It would also be fine to flag
>> the issue in the errata without specific resolution, with the
>> understanding that the issue would need to be resolved, in an update
>> or bis, at some point in the future.
>>
>> Lou
>>
>>> Thanks,
>>> Rob
>>>
>>>
>>> On 07/10/2018 18:09, Juergen Schoenwaelder wrote:
>>>> On Sun, Oct 07, 2018 at 09:49:57AM -0700, Andy Bierman wrote:
>>>>> Can somebody explain the rationale for the highlighted text from
>>>>> 5.3.4?
>>>> Note the difference between "applies to" and "carries". A non-presence
>>>> container has no relevance for configuration and hence an origin value
>>>> does not *apply* to a non-presence container. Still, a non-presence
>>>> container can *carry* an origin attribute.
>>>>
>>>>> There are many top-level configuration NP-containers defined already.
>>>>> It is clearly more efficient to have 1 origin attribute in the
>>>>> top-level
>>>>> container than in each of the child nodes.
>>>> There is no requirement to produce efficient encodings. This is up to
>>>> implementations, the cost of calculating a minimal encodings may be
>>>> high for systems that like to stream information. That said, even
>>>> toplevel origin attributes are not sufficient to guarantee an
>>>> efficient encoding. If most child nodes have an origin different than
>>>> what is stated in the toplevel container, you gain little.
>>>>
>>>> The requirement really is that an origin must be defined for all
>>>> configuration data nodes (except np-containers). The way how this
>>>> is done    is up to implementations. If implementations want to set
>>>> default    origins    at the toplevel, so be it.
>>>>
>>>> /js
>>>>
>> .
>>
>