Re: [netmod] Extensions vs new YANG versions [was Re: yang-data-ext issues]
Ladislav Lhotka <lhotka@nic.cz> Tue, 24 April 2018 14:07 UTC
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From: Ladislav Lhotka <lhotka@nic.cz>
To: Robert Wilton <rwilton@cisco.com>, Andy Bierman <andy@yumaworks.com>, Juergen Schoenwaelder <j.schoenwaelder@jacobs-university.de>, Robert Varga <nite@hq.sk>, NetMod WG <netmod@ietf.org>
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Subject: Re: [netmod] Extensions vs new YANG versions [was Re: yang-data-ext issues]
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Robert Wilton <rwilton@cisco.com> writes: > [Renaming the thread because this doesn't seem to be directly applicable > to the yang-data extension.] > > I think that extensions are great in the sense that they allow YANG to > evolve more quickly without requiring a fork lift version upgrade that > may take a long time to produce. This is of course a double-edged sword. In my view, extensions must not influence the resulting data model, and I thought the last paragraph in sec. 6.3.1 of RFC 6020 had been intended to mean exactly this. I would prefer to indicate experimental versions of YANG in the version string (e.g. as a topical branch), and use YANG extensions only for stuff that's outside the realm of data modelling. For example, the extension in NACM is perfectly OK because it is a hint for protocol operation and doesn't affect the schema in any way. > > I agree that all standard defined extensions should cleanly > inter-operate with each other. > > I also think that it is useful to periodically define new versions of > YANG that fold back in all the extensions that have been successfully > and are widely deployed. And also to deprecate/obsolete stuff that > hasn't worked well. Without a metamodel, it is difficult to avoid YANG becoming a kitchen sink. And what about extensions that won't make it into the new official version? For example, imagine that "openconfig:pattern" won't be accepted - would it really matter? The forked versions will continue to exist but they could still claim adherence to the IETF standard (which is what marketing departments love). Lada > > For me, the interesting question is about namespaces when those > extensions are incorporated back into a new version of YANG: > - Does it just keep the extension prefix that the extension module was > originally defined in? > - Or does the extension get folded into core of the YANG language and no > extension prefix is used any more? > - Or does the extension get supported both with/without the extension > namespace prefix? > > Thanks, > Rob > > > On 23/04/2018 21:58, Andy Bierman wrote: >> >> >> On Mon, Apr 23, 2018 at 10:36 AM, Juergen Schoenwaelder >> <j.schoenwaelder@jacobs-university.de >> <mailto:j.schoenwaelder@jacobs-university.de>> wrote: >> >> On Mon, Apr 23, 2018 at 07:18:38PM +0200, Robert Varga wrote: >> > On 23/04/18 18:51, Juergen Schoenwaelder wrote: >> > > Some people will say that the cost of a new language version >> is high. >> > > (Well, when we did 1.1, some people said it will never be >> deployed.) >> > > Anyway, not bumping the YANG version number but having instead >> several >> > > (optional) language extensions is just hiding the version number >> > > change under the carpet. >> > >> > Not quite, as extensions allow for modular/incremental >> evolution, as an >> > implementer I do not have to go through a long development cycle >> where I >> > need to rewire language aspects just to get the features my >> users need >> > for their models... >> >> Once we standardize extensions (and this is what I am talking about), >> we better make sure that the whole stays consistent. Otherwise, we >> will end up with patchwork where all the patches may work in isolation >> but sooner or later they will fall apart when you look at all the >> possible combinations. >> >> I am in favour of managing a clean definition of the core of the YANG >> language instead of creating patchwork. It is great if people create >> and prototype new extensions but once such extensions are considered >> to be ready for general use, we should roll them into the core (and >> remove any cruft from the core at the same time). >> >> >> I agree with your concerns. >> If the intent is that a YANG extension is optional, then its semantics >> have >> to be well-scoped so that tools really can skip over the extension >> without any problems. >> If we create standard extensions that standard YANG 1.1 modules use, >> then this can >> become an unofficial add-on to YANG 1.1. (e.g. annotation could >> already be considered as such) >> >> >> >> /js >> >> >> Andy >> >> -- >> Juergen Schoenwaelder Jacobs University Bremen gGmbH >> Phone: +49 421 200 3587 Campus Ring 1 | 28759 Bremen | Germany >> Fax: +49 421 200 3103 <https://www.jacobs-university.de/ >> <https://www.jacobs-university.de/>> >> >> _______________________________________________ >> netmod mailing list >> netmod@ietf.org <mailto:netmod@ietf.org> >> https://www.ietf.org/mailman/listinfo/netmod >> <https://www.ietf.org/mailman/listinfo/netmod> >> >> >> >> >> _______________________________________________ >> netmod mailing list >> netmod@ietf.org >> https://www.ietf.org/mailman/listinfo/netmod > -- Ladislav Lhotka Head, CZ.NIC Labs PGP Key ID: 0xB8F92B08A9F76C67
- Re: [netmod] yang-data-ext issues Kent Watsen
- Re: [netmod] yang-data-ext issues Joe Clarke
- Re: [netmod] yang-data-ext issues Kent Watsen
- [netmod] yang-data-ext issues Martin Bjorklund
- Re: [netmod] yang-data-ext issues Joe Clarke
- Re: [netmod] yang-data-ext issues Andy Bierman
- Re: [netmod] yang-data-ext issues Martin Bjorklund
- Re: [netmod] yang-data-ext issues Martin Bjorklund
- Re: [netmod] yang-data-ext issues Andy Bierman
- Re: [netmod] yang-data-ext issues Robert Wilton
- Re: [netmod] yang-data-ext issues Andy Bierman
- Re: [netmod] yang-data-ext issues Martin Bjorklund
- Re: [netmod] yang-data-ext issues Robert Wilton
- Re: [netmod] yang-data-ext issues Andy Bierman
- Re: [netmod] yang-data-ext issues Ladislav Lhotka
- Re: [netmod] yang-data-ext issues Kent Watsen
- Re: [netmod] yang-data-ext issues Martin Bjorklund
- Re: [netmod] yang-data-ext issues Andy Bierman
- Re: [netmod] yang-data-ext issues Martin Bjorklund
- Re: [netmod] yang-data-ext issues Andy Bierman
- Re: [netmod] yang-data-ext issues Kent Watsen
- Re: [netmod] yang-data-ext issues Robert Varga
- Re: [netmod] yang-data-ext issues Ladislav Lhotka
- Re: [netmod] yang-data-ext issues Martin Bjorklund
- Re: [netmod] yang-data-ext issues Andy Bierman
- Re: [netmod] yang-data-ext issues Martin Bjorklund
- Re: [netmod] yang-data-ext issues Andy Bierman
- Re: [netmod] yang-data-ext issues Robert Varga
- Re: [netmod] yang-data-ext issues Juergen Schoenwaelder
- Re: [netmod] yang-data-ext issues Robert Varga
- Re: [netmod] yang-data-ext issues Juergen Schoenwaelder
- Re: [netmod] yang-data-ext issues Martin Bjorklund
- Re: [netmod] yang-data-ext issues Martin Bjorklund
- Re: [netmod] yang-data-ext issues Andy Bierman
- Re: [netmod] yang-data-ext issues Martin Bjorklund
- Re: [netmod] yang-data-ext issues Andy Bierman
- [netmod] Extensions vs new YANG versions [was Re:… Robert Wilton
- Re: [netmod] yang-data-ext issues Robert Wilton
- Re: [netmod] Extensions vs new YANG versions [was… Ladislav Lhotka
- Re: [netmod] yang-data-ext issues Ladislav Lhotka
- Re: [netmod] yang-data-ext issues Ladislav Lhotka
- Re: [netmod] yang-data-ext issues Martin Bjorklund
- Re: [netmod] yang-data-ext issues Martin Bjorklund
- Re: [netmod] yang-data-ext issues Martin Bjorklund
- Re: [netmod] yang-data-ext issues Ladislav Lhotka
- Re: [netmod] yang-data-ext issues Andy Bierman
- Re: [netmod] yang-data-ext issues Kent Watsen
- Re: [netmod] yang-data-ext issues Martin Bjorklund
- Re: [netmod] yang-data-ext issues Martin Bjorklund
- Re: [netmod] yang-data-ext issues Andy Bierman
- Re: [netmod] yang-data-ext issues Andy Bierman
- Re: [netmod] yang-data-ext issues Ladislav Lhotka
- Re: [netmod] yang-data-ext issues Juergen Schoenwaelder
- Re: [netmod] yang-data-ext issues Ladislav Lhotka
- Re: [netmod] yang-data-ext issues Andy Bierman
- Re: [netmod] yang-data-ext issues Ladislav Lhotka
- Re: [netmod] yang-data-ext issues Ladislav Lhotka
- Re: [netmod] yang-data-ext issues Andy Bierman
- Re: [netmod] yang-data-ext issues Ladislav Lhotka
- Re: [netmod] yang-data-ext issues Martin Bjorklund
- Re: [netmod] yang-data-ext issues Robert Wilton
- Re: [netmod] yang-data-ext issues Ladislav Lhotka
- Re: [netmod] yang-data-ext issues Robert Wilton
- Re: [netmod] yang-data-ext issues Ladislav Lhotka
- Re: [netmod] yang-data-ext issues Juergen Schoenwaelder
- Re: [netmod] yang-data-ext issues Ladislav Lhotka
- Re: [netmod] yang-data-ext issues Andy Bierman
- Re: [netmod] yang-data-ext issues Juergen Schoenwaelder
- Re: [netmod] yang-data-ext issues Ladislav Lhotka
- Re: [netmod] yang-data-ext issues Kent Watsen
- Re: [netmod] yang-data-ext issues Andy Bierman
- Re: [netmod] yang-data-ext issues Kent Watsen
- Re: [netmod] yang-data-ext issues Juergen Schoenwaelder
- Re: [netmod] yang-data-ext issues Kent Watsen
- Re: [netmod] yang-data-ext issues Juergen Schoenwaelder
- Re: [netmod] yang-data-ext issues Martin Bjorklund
- Re: [netmod] yang-data-ext issues Ladislav Lhotka
- Re: [netmod] yang-data-ext issues Martin Bjorklund
- Re: [netmod] yang-data-ext issues Martin Bjorklund
- Re: [netmod] yang-data-ext issues Martin Bjorklund
- Re: [netmod] yang-data-ext issues Ladislav Lhotka
- Re: [netmod] yang-data-ext issues Martin Bjorklund
- Re: [netmod] yang-data-ext issues Robert Wilton
- Re: [netmod] yang-data-ext issues Martin Bjorklund
- Re: [netmod] yang-data-ext issues Juergen Schoenwaelder
- Re: [netmod] yang-data-ext issues Ladislav Lhotka
- Re: [netmod] yang-data-ext issues Robert Varga
- Re: [netmod] yang-data-ext issues Robert Varga
- Re: [netmod] yang-data-ext issues Kent Watsen
- Re: [netmod] yang-data-ext issues Juergen Schoenwaelder
- Re: [netmod] yang-data-ext issues Andy Bierman
- Re: [netmod] yang-data-ext issues Kent Watsen
- Re: [netmod] yang-data-ext issues Ladislav Lhotka