Re: [netmod] upcoming adoptions

Martin Bjorklund <mbj@tail-f.com> Wed, 30 August 2017 12:09 UTC

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Date: Wed, 30 Aug 2017 14:07:56 +0200 (CEST)
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From: Martin Bjorklund <mbj@tail-f.com>
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Subject: Re: [netmod] upcoming adoptions
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"Acee Lindem (acee)" <acee@cisco.com> wrote:
> Hi Martin, 
> 
> On 8/30/17, 6:28 AM, "Martin Bjorklund" <mbj@tail-f.com> wrote:
> 
> >Hi,
> >
> >Kent Watsen <kwatsen@juniper.net> wrote:
> >> 3. https://tools.ietf.org/html/draft-acee-netmod-rfc8022bis-00
> >
> >I found some trivial errors in this draft:
> >
> >  o  The revision for ietf-routing doesn't match the filename's date.
> >
> >  o  The filename for ietf-ipv6-router-advertisements is wrong (last
> >     "s" is missing)
> >
> >  o  All the old -state definitions are removed, rather than being
> >     marked as "deprecated".
> 
> 
> I’m glad you brought this up. We discussed this in the Routing YANG Design
> Team and were planning to discuss it on a wide scale.
> 
> One of the advantages of the NMDA is that it makes the models easier to
> read and consume. This is somewhat negated if we have to retain all these
> data nodes in the associated modules and mark them as “deprecated”. What
> is the consequence of not including them? They are available in the
> previous version of the model if they are need for compatibility.

It is fairly common that instead of removing functions from a
published API, you mark them as deprecated for some time, and then,
later, remove them (*).

Note that since a server cannot implement two versions of a given
module, it has to decide which version to implement.  There might be
other modules that use / augment the -state tree; if the server
implements the latest version w/o the -state tree, it cannot at the
same time implement these augmenting modules.

(*) YANG inherits the deprecation model from SMIv2.  We actually have
three states: current -> deprecated -> obsolete.  And even when
something is obsolete, it is not removed.  I guess in SMIv2 this was
necessary b/c of OID assignments; maybe this could be revisited for
YANG.  But this would require an update to RFC 7950.


If we think that a module becomes cluttered with all the deprecated
definitions, we can actually move them all to a separate submodule.


/martin