On Wed, Oct 14, 2015 at 10:49:02AM -0400, David Reid wrote:
> > >I'm reviewing 6020bis since it is in working group last call. 
> > >I see a new requirement that a server MUST NOT implement
> > >more than one revision of a module. I understand that supporting
> > >more than one revision can cause problems, but I expect that
> > >it will happen in practice. I know it happens sometimes with
> > >MIBs in SNMP. I think MUST NOT is too strong.
> > 
> > I've encountered the same phenomenon in the SNMP universe,
> > so if I expected Netconf to used as a replacement for SNMP
> > I'd have the same concern.
> > 
> > Randy
> 
> Here is the situation I face. We put a netconf server in our SNMP Master
> agent. Using the MIB to YANG conversion rules from RFC 6643 we can provide
> read-only access (or read-write in a non-standard way) via netconf and yang
> to all of the MIB data. We have existing customers using different revisions
> of the same MIB module in different subagents. If they convert those
> MIB modules to YANG modules and access the information via netconf, it
> would violate the proposed rule.

The RFC 6643 translation generates no mandatory statements in YANG and
the RFC 6643 translation is read-only. So for read-only access, using
the latest MIB module as a basis should work since SMIv2 has strict
backwards compatibility rules, no?

I do not know how you translate MIB modules into config true YANG
nodes but this is where things are tricky. In the SMIv2 world, you can
have many differnet conformance statements for a MIB module that can
slice MIB module implementation requirements in almost arbitrary ways
(and conformance statements may even be in different modules). In
other words, an SNMP agent claims conformance to a conformance
statement not to a MIB module per se. So in order to translate this
properly, you would have to either generate a YANG module with
suitable features for the different conformance statements or you
would have to find other ways to partition that data model to allow
differnet conformance levels.

/js

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

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