Re: [Netconf] Draft Charter Proposal for NETCONF WG

["Susan Hares" <[e-mail]>]

Robert: 

Pulling your comment to the front for ease of reference.  You stated: 
 
- YANG is the schema for that data.
- Datastores are really just views on data, bound to the schema and the data
life cycle
- Protocols are mechanism to access and modify that data, aided by the
schema & datastores.

Can you explain what you mean by "bound to the schema" and "data life
cycle"? 

My understanding from the revised datastores draft was that control plane
datastores are:

1) form a place in which to mount modules 
2) can have global characteristics [E.g. I2RS control plane datastore is
ephemeral] 
3) have their own validation rules  
4) can be tracked by meta-data when mixed with other datastores for
installation - which the applied datastore tracks. 
5) protocols are mechanisms to access/modify data - aided by schema and
datastores, but the 
protocols (NETCONF and RESTCONF) may need augmentation to support other
datastores 
(E.g. "get data <datatstore>") 

Sue 

-----Original Message-----
From: Netconf [mailto:[e-mail]] On Behalf Of Robert Wilton
Sent: Thursday, March 9, 2017 10:29 AM
To: t.petch; 'Netconf'
Subject: Re: [Netconf] Draft Charter Proposal for NETCONF WG

Hi Tom,


On 09/03/2017 12:12, t.petch wrote:
> ----- Original Message -----
> From: "Robert Wilton" <[e-mail]>
> Sent: Friday, March 03, 2017 5:41 PM
>
>> On 03/03/2017 17:18, t.petch wrote:
>>> ----- Original Message -----
>>> From: "Mehmet Ersue" <[e-mail]>
>>> Sent: Friday, March 03, 2017 2:33 PM
>>>
>>>>> Back to your question, it seems obvious to me that YANG and the
> XML
>>>> encoding rules naturally belong to NETMOD, the 'NETCONF protocol
>>> details
>>>> that NETCONF
>>>>> did not define' naturally belong to NETCONF.
>>>> Basically it is our aim to make the YANG language specification
>>> generally
>>>> applicable to all protocols and to put protocol-specific details
> into
>>> the
>>>> protocol specifications.
>>> See my response to Juergen; I agree with you but I define XML as not 
>>> being a protocol and so XML would remain; and I think that YANG will 
>>> have to say something about operations on the data it defines, just
> that
>>> they are defined as an abstract 'create', 'delete' etc and not as
> the
>>> set that NETCONF currently offers.
>> FWIW, this is the block
>> "      Common protocol abstraction
>> (that all YANG protocols should conform to). "
>>
>> That I was referring to in the diagram that I gave previously,
> although
>> I was suggesting that should belong in NETCONF WG rather than in YANG.
> Robert
>
> It has taken me a while to work out what you mean but now I have, I 
> disagree!
>
> You seem to place data(stores) at the heart of things, the root from 
> which all else flows.  I think that this can work with application 
> software in a stable, secure, delay-less environment where nothing 
> ever goes wrong (a mobile phone app perhaps!).
Yes, I definitely want to place accurate and meaningful data at the heart of
it.

As I see it:
- YANG is the schema for that data.
- Datastores are really just views on data, bound to the schema and the data
life cycle
- Protocols are mechanism to access and modify that data, aided by the
schema & datastores.

I really hope that the solution that we are constructing will work well for
systems that have real delays, unreliable communications, and potentially
buggy software.  Certainly, that is my goal ... Some of this will need
protocol assistance.

>
> Network management is different;  the failing network is both the 
> subject under consideration and an integral part of the solution.  The 
> operator has to use the failing network to find out what is failing 
> and what might be done about it and then use the failing network to 
> convey changes to the failing component of the network.  SNMP 
> recognised this but I am not sure the NETCONF/YANG do - after all, 
> their focus is on configuration, before things start going wrong.
I don't know the history, but my perception is that NETCONF/YANG was focused
on config because that is the part of SNMP that failed to gain traction in
the industry.  As NETCONF/YANG gains traction, it seems reasonable to want
to fix the operational state aspect of it that seems somewhat incomplete
today.

>
> I see revised-datastores as an attempt to fix this but one that will 
> fail, in the sense that it cannot go far enough; what may be needed is 
> a paradigm shift in Computer Science so a server can say that the 
> model it has been given cannot reflect reality but here is a better 
> one freshly created for the client to use!

So, I think that that issue that you are raising here is that a device might
not be able to accurately populate the schema being used for the operational
state datastore.  The latest (unpublished) datastores draft states that even
all values (including defaults) are returned in the operational state
datastore.  I.e. everything is explicit, meaning that if a device cannot
return the correct value for a node then it has the choice of returning no
value at all.

In terms of dynamic schema, devices can already define their own custom
schema and augmentations that can carry any extra vendor/device specific
data that cannot be readily mapped back into the standard schema.  The
problem here is that these schema are non standard (between vendors and/or
devices) and hence much harder for automated clients to use.  I think that
there is also a scope question of these additional vendor schema, given that
a lot of the data is likely to be verbose, possibly expensive to obtain, and
perhaps more diagnostics orientated.

>
> I don't see that happening just yet so revised-datastores will have to 
> do but I think it wrong to make that central - it will not be close 
> enough to reality.
It will be central in the sense that YANG models will either be built
assuming that it exists, or that it doesn't.  I don't think that you can
really have well constructed, fully useful, YANG models where the
operational state datastore is optional.

I don't think that the datastores draft is going to be a silver bullet that
solves all problems, but if the solution gains traction then I do think that
it will give a step improvement to making it easier to manage network
devices in an automated and robust way.

Regards,
Rob


>
> Tom Petch
>
>> Rob
>>
>>> Tom Petch
>>>
>>>> Mehmet
>>>>
>>>>> -----Original Message-----
>>>>> From: Juergen Schoenwaelder [mailto:j.schoenwaelder@jacobs- 
>>>>> university.de]
>>>>> Sent: Friday, March 3, 2017 2:35 PM
>>> <snip>
>>>
>>> _______________________________________________
>>> Netconf mailing list
>>> [e-mail]
>>> https://www.ietf.org/mailman/listinfo/netconf
>>> .
>>>
> .
>

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