Re: [netmod] Notifications with state data reference

Juergen Schoenwaelder <j.schoenwaelder@jacobs-university.de> Thu, 08 March 2018 09:00 UTC

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Date: Thu, 8 Mar 2018 10:00:49 +0100
From: Juergen Schoenwaelder <j.schoenwaelder@jacobs-university.de>
To: Michal =?utf-8?B?VmHFoWtv?= <mvasko@cesnet.cz>
Cc: netmod <netmod@ietf.org>
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Subject: Re: [netmod] Notifications with state data reference
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On Thu, Mar 08, 2018 at 09:08:42AM +0100, Michal Vaško wrote:
> Hi Juergen,
> thanks for an answer. I realized that validation of such notifications could be difficult because of the reasons you mentioned so I was rather questioning the fact that it is allowed to have references to state data in notifications in the first place. Also, I am not sure it is as harmless as it seems.
> 
> What if there is a union in the notification that includes instance-identifier, for example. The client receives the notification from a replay and is unable to validate (resolve) this union leaf. In effect, I dare say the leaf (and likely the whole notification) becomes useless for the client as it simply cannot learn what value is actually stored there. Is all this really okay?
>

Yes, it is possible to design notifications that are mostly useless
when being replayed - and sometimes even when they are sent live. The
same is true for log messages, if they do not include enough context,
they are useless. Operational state must be understood as being under
constant change. Hence, any references to operational state data that
has a high churn rate is likely of limited value.

We have to trust that authors of YANG models understand the dynamics
of the technology they are modeling. Implementation experience with
the technology usually helps a lot.

/js

-- 
Juergen Schoenwaelder           Jacobs University Bremen gGmbH
Phone: +49 421 200 3587         Campus Ring 1 | 28759 Bremen | Germany
Fax:   +49 421 200 3103         <https://www.jacobs-university.de/>