On Thu, May 01, 2014 at 07:38:39AM +0200, Juergen Schoenwaelder wrote:
> On Wed, Apr 30, 2014 at 08:24:51PM -0400, Jeffrey Haas wrote:
> > 
> > This is where I think we're getting stuck.  There is some vagueness between
> > operational state that can be modified and ephemeral configuration.
> 
> Are you saying there is a difference between 'writable operational
> state' and 'ephemeral configuration' but the difference is still
> unclear and hence vague?

Yes and no.  I'm still absorbing appropriate terminology from the N/Y RFCs
so please have patience with me.

State that I2RS injects into a system may be intended to be ephemeral.
That state may overlap with state that is otherwise configured in the usual
configuration based datastore.  E.g. static routes.

It is clearly possible to generate yang for I2RS that duplicates as much of
the yang for that configured state (e.g. static routes).  Yang provides
mechanisms to allow for re-use of the yang inputs (e.g. grouping) in another
module, provided that the original module was authored to enable re-use.

My observation is that in cases where there may be significant overlap of
I2RS injected ephemeral state, e.g. static routes, that it might be
desirable to not have to have a separate I2RS yang module unless there are
differences that necessitate a new module.  Effective, if I have my
terminology correct, to permit more than one datastore to be manipulated
using the same module.  I.e. "running configuration" and "I2RS ephemeral".

If such a thing were possible, then it would only compound the issues noted
in draft-bjorklund-netmod-operational since the configuration state for the
overlapping datastores also had related potentialy overlap in the
operational state.

To offer an older analogy for comparison, if I can configure static routes
via CLI and simultaneously by SNMP and both configurations can serve as
inputs to the RIB, the installed static route may come from either of the
candidates and the active entry will be selected by a preference.

In such a scenario, I still need to be able to see my configuration for the
CLI route and the SNMP installed route along with the actual route installed
in the RIB as active.

-- Jeff

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