Martin Bjorklund <[email protected]> writes:
> Ladislav Lhotka <[email protected]> wrote:
>>
>> > On 23 May 2016, at 14:30, Lou Berger <[email protected]> wrote:
>> >
>> > Hi Lada,
>> > I looks like no one really jumped on this one -- so better late than
>> > never ...
>> >
>> > When looking at the question below, we should consider the uses cases.
>> > I'm particularity interested (as a contributor) in the use case of
>> > nested mounts (NIs mounted within LNEs), as well as the case if models
>> > that will only permit mounting of specific other models vs generically
>> > mounting any model.
>> >
>> > On 4/6/2016 10:07 AM, Ladislav Lhotka wrote:
>> >> Hi,
>> >>
>> >> with a schema mount mechanism in place, there are two different
>> >> options
>> >> for constructing the overall schema (their combinations are possible,
>> >> too):
>> >>
>> >> 1. Define schema mount as an extension of YANG library so that it
>> >> defines YANG modules, revisions, features and deviations as before but
>> >> also the way how they are combined into a hierarchical structure of
>> >> schemas.
>> >
>> > I think this only makes sense if this is scoped in some way. For
>> > example, with LNEs, the parent/host server may not have visibility
>> > into
>> > the mounted models, (see draft-rtgyangdt-rtgwg-lne-model). And even
>> > if
>>
>> As I understand it, schema-mount is about accessing the LNE models
>> from the parent/host management interface. I believe the real question
>> is whether we want to allow the schema to dynamically change at run
>> time and possibly throw in new modules that the client never heard
>> of. #2 can do it while #1 can't. I am not sure though whether the LNE
>> model really requires something like this.
>>
>> > does, you have to consider the cases of mounted models contained
>> > within
>> > mounted models.
>>
>> This is possible either way, provided that the complete schema is
>> known upfront.
>
> I don't think I have seen a concrete proposal for such a compact
YSDL was such a proposal.
> format that can handle the case where different instances of a list
> with a mount point have different modules mounted, and some of them
> have mounted models within the mounted models.
>
> As a concrete example, suppose we have the model
> example-network-manager from Appendix B in
> draft-ietf-netmod-schema-mount-01:
>
> +--rw managed-devices
> +--rw device* [name]
> +--rw name string
> +--rw transport
> +--rw root yangmnt:mount-point managed-device
>
> Now, let's assume that two devices exist, A and B:
>
> A implements: ietf-interfaces, example-netowrk-manager
> B implements: ietf-system
>
> In A, there is a managed-device C which implements ietf-interfaces and
> ietf-ip.
>
> What would this look like in the compact form?
The module "example-network-manager" would be modified as follows:
+--rw managed-devices
+--rw device* [name]
+--rw name string
+--rw transport
+--rw (root)
+--:(A)
+--:(B)
+--:(C)
And then:
{
"ietf-ysdl:schemas": {
"top-schema": "host",
"schema": [
{
"name": "host",
"yang-modules": [ "example-logical-devices" ],
"subschema": [
{
"root":
"/example-network-manager:managed-devices/device/root/A",
"schemas": [ "schema-A" ]
}
{
"root":
"/example-network-manager:managed-devices/device/root/B",
"schemas": [ "schema-B" ]
}
]
},
{
"name": "schema-A",
"yang-modules": [
"ietf-interfaces",
"example-network-manager"
],
"subschema": [
{
"root":
"/example-network-manager:managed-devices/device/root/C",
"schemas": [ "schema-C" ]
}
]
},
{
"name": "schema-B",
"yang-modules": [ "ietf-system" ]
},
{
"name": "schema-C",
"yang-modules": [
"ietf-interfaces",
"ietf-ip"
]
}
]
}
}
As long as all modules comprising the schema and their possible
arrangement is known in advance, it should flexible enough. And as I
said, I'd prefer to address this case in schema-mount because the model
of trust between the server and client isn't changed in any way.
>
> BTW, in this case, it is not obvious that the top-level server knows
> anything about the data models mounted by C...
But then the top-level server cannot possibly serve data for C.
Lada
>
>
> /martin
>
>
>
>
>>
>> >
>> >>
>> >> 2. Apart from YANG Library data, the server just specifies the mount
>> >> points. A client of an NM protocol is expected to fetch a new instance
>> >> of YANG library and/or subordinate mount points as state data from a
>> >> well-known location under each mount point.
>> >
>> > I think this depends on the use case. For LNEs, I think this is
>> > right.
>> > For some of the other possible use cases being discussed only a
>> > specific
>> > model can be mounted.
>>
>> I guess I need some example scenarios demonstrating that #1 cannot be
>> used for LNE.
>
--
Ladislav Lhotka, CZ.NIC Labs
PGP Key ID: E74E8C0C
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