Re: [netmod] schema-mount pre09 branch

Martin Bjorklund <mbj@tail-f.com> Tue, 06 February 2018 14:01 UTC

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Date: Tue, 06 Feb 2018 15:00:49 +0100 (CET)
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To: rwilton@cisco.com
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From: Martin Bjorklund <mbj@tail-f.com>
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Subject: Re: [netmod] schema-mount pre09 branch
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Hi,

Thanks for your comments, see inline.

Robert Wilton <rwilton@cisco.com> wrote:
> Hi,
> 
> Some comments on the pre-09 version, particularly the data model.
> 
> 
> 1) I still don't get why this draft is called "YANG Schema Mount"
> rather than "YANG Mount", since to me this implies that it *only* the
> schema that is being made available, and by implication not the
> instance data.  I.e. I can see what schema a VM is using, but I cannot
> access the instance data of that VM.
> 
> I understand the scope of the draft (and I'm not trying to change that
> at all), and agree that it doesn't specify any protocol for how to
> remotely mount data (e.g. peer mount).  But my understanding of the
> solution here is that it doesn't just mount the schema.  I think that
> it also always makes the mounted instance data available using the
> regular NETCONF/RESTCONF operations right?  Which sounds like it is
> doing more than just mounting the schema!

Once you have a mounted schema, even in the inline case, a server
might be just a single normal server with no extra VMs or anything;
you just have a nested schema.  Such a server would allow you to use
normal edit-config to add mounted data, and it would just affect that
single server's database and instrumentation.

The point is that schema mount says nothing about *how* things are
instantiated.

Peer mount, OTOH, attaches instance-specific meaning to its mount
points - if you try to write to peer mounted data the server will act
as a "proxy" and write to the remote server.  (ok, current peer mount
is defined to be read-only, but you get my point).

> 2) Regarding the YANG Data Model:
> 
> (i) Should "schema-mounts" just be "mounts", since it is already under
> the "schema" container.

I don't have a strong opinion on this.

> (ii) Should "parent-references" be part of the "use-schema" container,
> or should then be part of a schema directly.  E.g. should schema-mount
> augment yanglib:schema with both a "mounts" container and a
> "parent-reference" leaflist.

This would mean the same parent-references for all mount points in a
schema, as opposed to per-mount-point parent-references as we have
today.  Lada, what's your opinion on this?

> (iii) Do we definitely need the namespace list?  Shouldn't the
> prefixes/namespaces be resolved against the implemented modules in the
> referenced schema, or is this not sufficient?  If this is not
> sufficient, I wonder if it would be helpful for the draft to describe
> this.

It is not sufficient b/c the only prefixes available from the
implemented modules are the prefixes in the modules themselves, and
they aren't necessarily unique.

> (iv) I agree with Juergen that "inline" is a confusing term because it
> is meaning that the mounted schema is available inline in the instance
> data tree, not that it is inline in the schema tree.



/martin



> 
> Thanks,
> Rob
> 
> 
> On 31/01/2018 21:36, Kent Watsen wrote:
> > All,
> >
> > The authors created a "pre09" branch on GitHub a few weeks back.  On
> > this branch, they completed a full update of the draft.  While waiting
> > for details on how to proceed with regards to a SM-bis, we thought it
> > would be helpful to make this text available now so that the technical
> > parts can be discussed.  With this in mind, can folks please have a
> > quick look and post any technical comments they have?
> >
> >
> > The "txt" version of the draft:
> > https://raw.githubusercontent.com/netmod-wg/schema-mount/pre09/draft-ietf-netmod-schema-mount-pre-09.txt
> >
> >
> > rfcdiff against the current -08 draft:
> > https://www.ietf.org/rfcdiff?url1=draft-ietf-netmod-schema-mount-08&url2=https://raw.githubusercontent.com/netmod-wg/schema-mount/pre09/draft-ietf-netmod-schema-mount-pre-09.txt
> >
> >
> > Since rfc7895bis obsoletes RFC 7895, the
> > server-must-implement-rfc7895bis requirement is no surprise, right?
> >
> > Thanks,
> > Kent // shepherd
> >
> >
> > _______________________________________________
> > netmod mailing list
> > netmod@ietf.org
> > https://www.ietf.org/mailman/listinfo/netmod
> > .
> >
>