Re: [Netmod-ver-dt] [netmod-wg/yang-ver-dt] Status obsolete nodes (#2)

"Rob Wilton (rwilton)" <rwilton@cisco.com> Wed, 05 June 2019 13:34 UTC

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From: "Rob Wilton (rwilton)" <rwilton@cisco.com>
To: "Sterne, Jason (Nokia - CA/Ottawa)" <jason.sterne@nokia.com>, "netmod-ver-dt@ietf.org" <netmod-ver-dt@ietf.org>
Thread-Topic: [netmod-wg/yang-ver-dt] Status obsolete nodes (#2)
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Date: Wed, 05 Jun 2019 13:34:16 +0000
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References: <netmod-wg/yang-ver-dt/issues/2@github.com> <netmod-wg/yang-ver-dt/issues/2/498628782@github.com> <VI1PR07MB3981384DCEC43089F2E694D89B150@VI1PR07MB3981.eurprd07.prod.outlook.com> <BYAPR11MB2631509189C7F34A8E425143B5160@BYAPR11MB2631.namprd11.prod.outlook.com> <VI1PR07MB3981B6DB26CABC07D325C8A49B160@VI1PR07MB3981.eurprd07.prod.outlook.com>
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Subject: Re: [Netmod-ver-dt] [netmod-wg/yang-ver-dt] Status obsolete nodes (#2)
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From: Netmod-ver-dt <netmod-ver-dt-bounces@ietf.org> On Behalf Of Sterne, Jason (Nokia - CA/Ottawa)
Sent: 05 June 2019 14:23
To: Rob Wilton (rwilton) <rwilton@cisco.com>; netmod-ver-dt@ietf.org
Subject: Re: [Netmod-ver-dt] [netmod-wg/yang-ver-dt] Status obsolete nodes (#2)

I would have thought that "status obsolete" would trump "mandatory".
[RW]
Martin’s view was effectively the opposite.  I.e. if the node is implemented then mandatory would take effect.


It seems a bit odd to provide support for a node marked obsolete. Do we think there are servers out there today that support them?
[RW]
Unclear.

One scenario is a standards based model that is implemented, used by customers, and then some of the configuration gets obsoleted, but the vendor wants to keep supporting it because some of the customers are still using it.

Today, in RFC 7950, obsolete states:
   o  "obsolete" means that the definition is obsolete and SHOULD NOT be
      implemented and/or can be removed from implementations.

Noting the “SHOULD NOT” and “can be removed”, rather than “MUST NOT be implemented and/or MUST be removed …”.

Basically, I think that YANG ends up being slightly broken if obsolete nodes can be implemented, but allows implementations to do this.  I think that this will get fixed in YANG.Next, but that will only help with YANG 1.2 modules.  For everything else, it will still need a flag to report to clients what devices actually do.

Thanks,
Rob


From: Rob Wilton (rwilton) <rwilton@cisco.com<mailto:rwilton@cisco.com>>
Sent: Wednesday, June 5, 2019 4:46 AM
To: Sterne, Jason (Nokia - CA/Ottawa) <jason.sterne@nokia.com<mailto:jason.sterne@nokia.com>>; netmod-ver-dt@ietf.org<mailto:netmod-ver-dt@ietf.org>
Subject: RE: [netmod-wg/yang-ver-dt] Status obsolete nodes (#2)

Yes.  At the moment, a server is allowed to implement obsolete nodes that can break a client.

E.g. if an obsolete config node is mandatory, and it is implemented then the client must provide it, and if it is not implemented then the client must not provide it, and there is no way for a client to determine from the server whether it is implemented.

Thanks,
Rob


From: Netmod-ver-dt <netmod-ver-dt-bounces@ietf.org<mailto:netmod-ver-dt-bounces@ietf.org>> On Behalf Of Sterne, Jason (Nokia - CA/Ottawa)
Sent: 04 June 2019 18:54
To: netmod-ver-dt@ietf.org<mailto:netmod-ver-dt@ietf.org>
Subject: Re: [Netmod-ver-dt] [netmod-wg/yang-ver-dt] Status obsolete nodes (#2)

I know we wanted a flag for deprecated nodes.  But was there ever confusion about obsolete nodes?

From: Robert Wilton <notifications@github.com<mailto:notifications@github.com>>
Sent: Tuesday, June 4, 2019 7:16 AM
To: netmod-wg/yang-ver-dt <yang-ver-dt@noreply.github.com<mailto:yang-ver-dt@noreply.github.com>>
Cc: Subscribed <subscribed@noreply.github.com<mailto:subscribed@noreply.github.com>>
Subject: Re: [netmod-wg/yang-ver-dt] Status obsolete nodes (#2)


The YANG library changes indicate whether status obsolete nodes are implemented by the server., which I think is as much as we can do in this draft.

Otherwise, this issue can be deferred to YANG.Next. netmod-wg/yang-next#63<https://github.com/netmod-wg/yang-next/issues/63>

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