> On 24 May 2016, at 14:52, Martin Bjorklund <[email protected]> wrote:
>
> Ladislav Lhotka <[email protected]> wrote:
>> 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)
>
> But A, B and C are device names (instances).
So what? A, B and C can be the values of the "name" key, too.
>
> Also, C would be:
>
> /managed-devices/device[name="A"]/root/managed-devices/device[name="C"]
Yes.
>
>
>> 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",
>
> Can the root contain instance information?
No, it is a schema-node-path, that's why it can contain "choice" and "case"
nodes. It should be possible to construct the complete schema without looking
into any instances.
Lada
>
>
> /martin
>
>
>> "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
>>
--
Ladislav Lhotka, CZ.NIC Labs
PGP Key ID: E74E8C0C
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