Re: [netmod] I-D Action: draft-ietf-netmod-revised-datastores-02.txt

[Phil Shafer <[e-mail]>]

Andy Bierman writes:
>I think the remnant configuration text needs clarification.
>I thought the whole point of the operational datastore for config=true
>nodes was to
>provide the intended and applied values using the exact same
>instance-identifier.

Instance names are the same.  Remnant configuration is data that
remains in operational use (and is reported in <operational>) after
it has been removed from <intended>.  This is typically the brief
period during implementation of the incoming data.  The text says:

  - remnant configuration: Configuration that remains part of the
    applied configuration for a period of time after it has been removed
    from the intended configuration or dynamic configuration.  The time
    period may be minimal, or may last until all resources used by the
    newly-deleted configuration (e.g., network connections, memory
    allocations, file handles) have been deallocated.

There's also text in the "The Operational State Datastore" section
(quoted below).  What is needed to make it more clear?

>NC/RC/YANG does not allow the old operational value and new operational
>value to
>exist in the same datastore.  Once the server has the new value to report,
>it will overwrite
>the old value.

<operational> should report the currently in use values, even when
that differs from <intended>.  The draft currently says:

  As a result of remnant configuration, the semantic constraints defined
  in the data model cannot be relied upon for <operational>, since the
  system may have remnant configuration whose constraints were valid
  with the previous configuration and that are not valid with the
  current configuration.  Since constraints on "config false" nodes may
  refer to "config true" nodes, remnant configuration may force the
  violation of those constraints.  The constraints that may not hold
  include "when", "must", "min-elements", and "max-elements".  Note that
  syntactic constraints cannot be violated, including hierarchical
  organization, identifiers, and type-based constraints.

>Perhaps you mean other instances will be considered old, but the RD
>solution has no way to
>correlate the new instances to the old ones.
>Therefore, YANG validation may
>fail on the operational
>datastore while updates are being applied. I think the draft should make
>this more clear.

Yes, <operational> will be have circumstances where it's contents
will not be valid.  It's better that the box provide accurate data
than provide valid data that is not accurate.  So we say that while
syntactic constraints cannot be violated, semantic constraints can
be.

Thanks,
 Phil