Re: [netmod] Y60 - coexistence with YANG 1.0

[Martin Bjorklund <[e-mail]>]

Ladislav Lhotka <[e-mail]> wrote:
> 
> > On 10 Sep 2015, at 12:55, Martin Bjorklund <[e-mail]> wrote:
> > 
> > Hi,
> > 
> > I think we agreed that is ok for a YANG 1.1 module to import a YANG
> > 1.0 module.
> > 
> > But should it also be ok for a 1.0 module to import a 1.1 module?
> 
> I think it should be illegal for a 1.0 module to import with revision
> if the requested revision is 1.1.

Ok.

> > If we make this illegal, we might run into problems.  For example,
> > ietf-ip imports ietf-interfaces.  Suppose we update ietf-interfaces
> > and the new version use YANG 1.1.  Is it ok for a server to implement
> > the 1.0 version of ietf-ip and 1.1 version of ietf-interfaces?  If the
> > answer is no, it means that we either have to update all modules to
> > 1.1 more or less at the same time (including vendor models!), or we
> > keep existing modules on 1.0 "forever".
> > 
> > At the lastest interim, it was suggested that a server that implements
> > such a combination of models would internally promote the 1.0 module
> > to 1.1, and thus make this combination legal.
> 
> I think we need a way for the server to identify itself to the client
> as 1.1-capable, and then:
> 
> - 1.1-capable server: if 1.0 module X imports Y *without revision*, and
>   the revision of Y advertised by the server (with
>   default-revision=true), then module X is automatically interpreted as
>   1.1.

I assume you mean that Y is 1.1.

> - 1.0-only server: if 1.0 module X import Y without revision, then the
>   latest 1.0 revision of Y is used. If 1.1 revisions exist, they are not
>   used.

Yes.

> > Such a strategy should also be safe for old clients, still treating
> > the module as being 1.0.
> 
> I am not sure about this, I think a 1.0-only client cannot work with a
> 1.1-capable server is some 1.1 additions are used (e.g. if-feature
> expressions).

Note that the 1.0 client worked with the 1.0 server with 1.0 modules X
and Y before.  Now Y is updated to 1.1.  According to section 10, Y is
not allowed to add if-feature to existing definitions.


/martin


> > It is a bit unclear what the server should do if the 1.0 module that
> > it "internally promotes" to 1.1 contains something that is illegal in
> > 1.1, e.g.:
> > 
> >        default "a\xb”;
> 
> We should write an erratum to 6020 making this illegal in 1.0, too.
> 
> Lada
> 
> > 
> > Comments?
> > 
> > 
> > /martin
> > 
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> 
> --
> Ladislav Lhotka, CZ.NIC Labs
> PGP Key ID: E74E8C0C
> 
> 
> 
>