Subject: Re: [netmod] new issue: configuration versus state data

From: Randy Presuhn <[email-masked]>
Date: Fri, 11 Apr 2014 11:34:18 -0700 (GMT-07:00)

Hi -

>From: Ladislav Lhotka <[email-masked]>
>Sent: Apr 11, 2014 10:03 AM
>To: Andy Bierman <[email-masked]>
>Cc: "[email-masked]" <[email-masked]>
>Subject: Re: [netmod] new issue: configuration versus state data
...
>Well, I think there has to be *the* operational state datastore
>that’s used by all management interfaces.
...

At the bottom of the pile, on most systems there is.  The
problems are that:

  (1) the nature of this datastore may actually be different
      for different resources on the same system

  (2) the relationship between this datastore and
      data/information models mapped onto it is (to varying
      degrees) both model- and implementation-specific

  (3) the various models mapped onto the datastore
      sometimes impose conflicting requirements, and
      the various sets of instrumentation accessing the
      datastore often ignore each other's needs

It would be lovely to have a way of formally expressing the
relationships for a given system with a particular configuration
(since the relationships depend on the exact combination of
hardware and software and their configuration), so that the
behaviour of that system might be rigorously described.

But I suspect the reality would turn out to be that for too
many "open" systems, the formal description would only tell you
that the system's behaviour either not fully deterministic,
or that the inter-relationships are so complicated that the
formal description is unhelpful.

Randy

---

From: Ladislav Lhotka <[email-masked]>
Date: Fri, 11 Apr 2014 20:59:41 +0200

Hi Randy,

>      datastore often ignore each other's needs

I agree the concept of state datastore is not completely straightforward but

- it is even worse to assume that it is a super-tree of the configuration tree,

- a hierarchical data structure seems to be quite common - YANG, MIB, /proc, most CLIs.  

Lada

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Ladislav Lhotka, CZ.NIC Labs
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