Hi - >From: "Alexander Clemm (alex)" <a...@cisco.com> >Sent: Sep 1, 2015 2:21 PM >To: Randy Presuhn <randy_pres...@mindspring.com>, "netmod@ietf.org" ><netmod@ietf.org> >Subject: RE: [netmod] Motivations for Structuring Models > >Hi Randy, > >GDMO had some very powerful concepts. The ability to separate >definition hierarchy and containment hierarchy is indeed very >powerful. In many ways, it was ahead of its time. The problem >I see is that in the context of YANG (much simpler), I don't >think the same concept of name bindings is applicable, really.
Agreed. At best it would probably be an ugly bolt-on; some of the concerns it is intended to address are ones that folks in the Netconf universe have tended to declare out-of-scope, though as more people use these tools we'll probably encounter more calls to revisit those long-held assumptions. > The difference is that in GDMO, MOC definitions did not make > any statement about naming/ containment - this made it possible > to separate containment out from other aspects of the model, > cleanly, as they were orthogonal concepts. In YANG, however, > the definition of the containment structure is very much at > the core of what is being defined as part of the model. That's a polite way of saying the difficulty is architectural, and *completely* fixing it would likely be disruptive. I think you're right. > This is in part what makes it simple (and IMHO arguably > also easier to read and consume - name bindings were arguably > "harder to follow"), but there are some limitations that we > are starting to bump into. They're essentially the same problems as arise with naming in SNMP-land, with the same causes and consequences. > I think it is possible to address these (allowing the > definition of mount points is one proposal), but the > mechanism will need to be different from name bindings > simply because the MOCs being linked are not defined "on > their own", but as part of containment relationships > intrinsically tied to their definitions. I agree a mechanism to accomplish something like it will likely be quite different. Name bindings rely on a particular characteristics of the metamodel and have specific consequences for the management protocol, and both sets of assumptions don't hold true in netconf/yang-land. Trying to ape GDMO does not seem like a productive route to me, given where Yang already finds itself. As long as naming is so closely bound to the definition, however, use of the models is constrained in unhelpful ways. Using mount points, at least as they've been formulated so far, only addresses parts of the problem. Whether that's going to be good enough remains to be seen. Without mount points or something similar, what we currently have is only about as broken as SNMP/SMI, and the industry got a lot of mileage out of that. I suspect the debate over mount points will be the beginning of netconf's counterpart to the "subagent wars" where the issue was not so much one of "can this be made to work with(out) this technology increment" than one of "what is the impact of this technology increment on our overall development/deployment/operational cost". Randy _______________________________________________ netmod mailing list netmod@ietf.org https://www.ietf.org/mailman/listinfo/netmod
