On Wed, Dec 8, 2021 at 9:27 AM tom petch <[email protected]> wrote:

> From: Ladislav Lhotka <[email protected]>
> Sent: 08 December 2021 12:38
>
> tom petch <[email protected]> writes:
>
> > The BFD WG are revising RFC9127 to add a new feature if-feature
> > "client-base-cfg-parms"; and make uses base-cfg-parms { conditional
> > thereon in module ietf-bfd-types.  Reading and re-reading RFC7950,
> > especially about mandatory and top-level, I am not convinced that
> > this is legal.
>
> Sorry, I don't get the problem - nothing in the "base-cfg-parms" grouping
> is mandatory. Why do you think this might be illegal?
>
> <tp>
> Reading that section I find parts less than clear, especially about top
> level and mandatory.  Could a PIM eg module importing that grouping make it
> top level or mandatory even if it is not so in the BFD module?
>
>

Yes. The refine-stmt can add or change a mandatory-stmt.
 https://datatracker.ietf.org/doc/html/rfc7950#section-7.13.2

This only affects the specific "uses" of the grouping, never the grouping
itself.

Andy



I realise that such as NACM can always make part of the tree invisible so
> software has to be prepared for something to be missing but I am not
> confident of my interpretation.
>
> Tom Petch
> Lada
>
> > The module bfd-types is imported by a number of other modules such
> > as OSPF, RIP, PIM so it is also a question if e.g. a leaf can be
> > made mandatory by its usage in another module.  I raised this on the
> > BFD list and the WG Chair tells me that this is a violation of the
> > intent of the RFC, 7950, but that it has been reviewed by YANG
> > doctors and is probably the best fix.
> >
> > If YANG Doctors collectively say that this violation is ok, then I think
> that such a statement needs to appear on the Netmod WG list.
> >
> > I think that there are a lot of other editorial changes needed to
> 9127-bis to make it legal but they can come later.  The I-D is in WG Last
> Call ending 20Dec2021
> >
> > Tom Petch
> > _______________________________________________
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> > [email protected]
> > https://www.ietf.org/mailman/listinfo/netmod
>
> --
> Ladislav Lhotka
> Head, CZ.NIC Labs
> PGP Key ID: 0xB8F92B08A9F76C67
>
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