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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=.*]')
This would alow you to point at an interface anywhere (as long as
the list is named interface with a key called name :-( ). Note the
regexp is not 100% OK.
regards Balazs
On 2016-04-29 22:55, Xufeng Liu wrote:
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:[email protected]] On Behalf Of Joel M. Halpern
Sent: Friday, April 29, 2016 1:05 PM
To: Tarek Saad (tsaad) <[email protected]>; Martin Bjorklund
<[email protected]>
Cc: [email protected]; [email protected]; [email protected];
[email protected]; [email protected]
Subject: Re: [Teas] [netmod] Use of schema mounts for common model
With regard to leafrefs trying to point into groupings, would
instance-identifiers
work 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" <[email protected]
<mailto:[email protected]>> wrote:
"Tarek Saad (tsaad)" <[email protected] <mailto:[email protected]>>
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 the
global
tree (e.g. from the ietf-interfaces model to define additional
TE
properties associated with a specific device interface). Our
understanding after reading section 3.1 of your draft is the
mounted
model can *not* reference any data nodes outside the scope of
the
mount-point (e.g. global data nodes in the yang tree). This
poses a
limitation 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 feedback
on
this 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-
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, and
the
mounted data nodes as its children. This means that data
within a
mounted subtree can never refer to data outside of this
subtree.
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--
Balazs Lengyel Ericsson Hungary Ltd.
Senior Specialist
Mobile: +36-70-330-7909 email: [email protected]
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