Re: [mpls] [netmod] [Teas] Use of schema mounts for common model
Balazs Lengyel <balazs.lengyel@ericsson.com> Thu, 05 May 2016 14:36 UTC
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To: Xufeng Liu <xufeng.liu.ietf@gmail.com>, "'Joel M. Halpern'" <jmh@joelhalpern.com>, "'Tarek Saad (tsaad)'" <tsaad@cisco.com>, 'Martin Bjorklund' <mbj@tail-f.com>
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From: Balazs Lengyel <balazs.lengyel@ericsson.com>
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Date: Thu, 05 May 2016 16:28:20 +0200
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Cc: draft-ietf-teas-yang-te@ietf.org, mpls@ietf.org, teas@ietf.org, netmod@ietf.org, draft-ietf-netmod-schema-mount@ietf.org
Subject: Re: [mpls] [netmod] [Teas] Use of schema mounts for common model
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Hello,
As I see it the problem is that as we don't know the mount
relationships early. All you can say in the constraint is "point
at some interface". So having a specific path statement is not
feasible.
Using instance-identifiers may help. While it is hard it is not
impossible to constrain instance-identifiers. You can put a
regular expression on their "string" representation, e.g.
rematch(.,'/.*/interface[name=.*]')
regards Balazs
We still hope that schema mount can handle cross-referencing across mounted modules. It is also needed when ietf-interfaces model is mounted to logical-network-element and network-instance models. More comments for this case below in-line. Thanks, - Xufeng-----Original Message----- From: Teas [mailto:teas-bounces@ietf.org] On Behalf Of Joel M. Halpern Sent: Friday, April 29, 2016 1:05 PM To: Tarek Saad (tsaad) <tsaad@cisco.com>; Martin Bjorklund<mbj@tail-f.com>Cc: draft-ietf-teas-yang-te@ietf.org; mpls@ietf.org; teas@ietf.org; netmod@ietf.org; draft-ietf-netmod-schema-mount@ietf.org Subject: Re: [Teas] [netmod] Use of schema mounts for common model With regard to leafrefs trying to point into groupings, wouldinstance-identifierswork for your use case?In this case, it would be hard to specify the must conditions for these instance-identifiers to make them always applicable when the groupings are used in various situations. If we are willing to re-structure everything, the method used in draft-halpern-supa-generic-policy-data-model could be an option to explore.Yours, Joel On 4/29/16 12:17 PM, Tarek Saad (tsaad) wrote:Thanks Martin, please see inline.. On 2016-04-29, 6:29 AM, "Martin Bjorklund" <mbj@tail-f.com <mailto:mbj@tail-f.com>> wrote: "Tarek Saad (tsaad)" <tsaad@cisco.com <mailto:tsaad@cisco.com>>wrote:Hi authors/WG, In draft-ietf-teas-yang-te, we are driving the definition for a generic TE YANG model that can/may be used (and extended when necessary) for different data plane technologies (e.g. MPLS, OTN, WDM, etc.). Reviewing the schema mount idea presented in draft-ietf-netmod-schema-mount, we are thinking this proposal is useful and can facilitate the reuse of the our model in multiple places in the YANG tree (once per each technology), e.g.: ./mpls/mount-points/mount-point/module=ietf-te.yang ./otn/mount-points/mount-point/module=ietf-te.yang Schema mount is probably not the right solution to your problem. I think a better solution in your case is to define groupings. Groupings are designed to be re-used at different places in the hierarchy. We thought of this earlier, and found groupings pose their own set of challenges too.. Specifically: - a groupings with leafrefs could not reference data nodes that reside in another grouping - a grouping with leafrefs of relative path were challenge when the relative path references data nodes outside the grouping - the augmentation of the grouping by other modules is not as straightforward That said, the grouping proposal seems to one could also think that with groupings one could address reuse of the a model (e.g. Ietf-interfaces) for logical devices or VM (see below). In fact, in your draft (section 2) you explicitly discourage this approach as not scalable solution With the "uses" approach, ietf-interfaces would have to define a grouping with all its nodes, and the new model for logical devices would have to use this grouping. This is a not a scalable solution, since every time there is a new model defined, we would have to update our model for logical devices to use a grouping from the new model. Another problem is that this approach cannot handle vendor- We have a comment/concern/suggestion and we value your feedback. The generic TE model currently references data nodes in theglobaltree (e.g. from the ietf-interfaces model to define additionalTEproperties associated with a specific device interface). Our understanding after reading section 3.1 of your draft is themountedmodel can *not* reference any data nodes outside the scope ofthemount-point (e.g. global data nodes in the yang tree). Thisposes alimitation for us, do you have a suggestion for this problem? One possible solution we thought of was to replace the leaf-refs pointing to the global data nodes (e.g. Ietf-interfaces) with context names (e.g. the interface name).. This decouples the data-nodes defined in the TE generic model from those in the global tree (e.g. the actual interface ietf-interfaces model). Any feedbackonthis or better suggestions?In this case, there are multiple augmentations to ietf-te.yang, such as ietf-rsvp-te and ietf-sr-te. If ietf-te is a grouping, we cannot do the augmentations before ietf-te is used. Using the grouping would be very awkward when ietf-te is used. We would have to make the same many augmentations at that time. Even worse, there could be future augmentations, we cannot specify these augmentations now because they are not defined yet.If you use groupings instead, you can still use proper leafrefs. Not in all cases - as described above. Regards, Tarek /martin Regards, Tarek Excerpt from draft-ietf-netmod-schema-mount 3.1<https://tools.ietf.org/html/draft-ietf-netmod-schema-mount" rel="nofollow">https://tools.ietf.org/html/draft-ietf-netmod-schema-mount-01#section-3.1>.Augment and Validation in Mounted Data All paths (in leafrefs, instance-identifiers, XPath expressions, and target nodes of augments) in the data models mounted at a mount point are interpreted with the mount point as the root node, andthemounted data nodes as its children. This means that data within a mounted subtree can never refer to data outside of thissubtree._______________________________________________ netmod mailing list netmod@ietf.org https://www.ietf.org/mailman/listinfo/netmod" rel="nofollow">https://www.ietf.org/mailman/listinfo/netmod_______________________________________________ Teas mailing list Teas@ietf.org https://www.ietf.org/mailman/listinfo/teas" rel="nofollow">https://www.ietf.org/mailman/listinfo/teas_______________________________________________ netmod mailing list netmod@ietf.org https://www.ietf.org/mailman/listinfo/netmod" rel="nofollow">https://www.ietf.org/mailman/listinfo/netmod
-- Balazs Lengyel Ericsson Hungary Ltd. Senior Specialist Mobile: +36-70-330-7909 email: Balazs.Lengyel@ericsson.com
- [mpls] Use of schema mounts for common model Tarek Saad (tsaad)
- Re: [mpls] [netmod] Use of schema mounts for comm… Martin Bjorklund
- Re: [mpls] [netmod] Use of schema mounts for comm… Tarek Saad (tsaad)
- Re: [mpls] [netmod] Use of schema mounts for comm… Joel M. Halpern
- Re: [mpls] [Teas] [netmod] Use of schema mounts f… Xufeng Liu
- Re: [mpls] [netmod] Use of schema mounts for comm… Robert Wilton
- Re: [mpls] [netmod] [Teas] Use of schema mounts f… Balazs Lengyel
- Re: [mpls] [netmod] Use of schema mounts for comm… Tarek Saad (tsaad)