On Thu, Dec 21, 2017 at 02:03:45PM +0100, Vladimir Vassilev wrote: > On 12/21/2017 11:34 AM, Robert Wilton wrote: > > > Hi Vladimir, > > > > First point of clarification is that this is not about running/intended > > at all. The contents of running/intended do not change in anyway > > depending on whether hardware is present or absent. > > > > The section is only concerned with how the configuration is applied in > > operational, and basically says that you cannot apply configuration for > > resources that are missing (which seems reasonable). E.g. I cannot > > configure an IP address on a physical interface that isn't there. Or if > > the physical interface gets removed then the configuration associated > > with that interface is also removed from operational. > > > > Operational isn't validated and data model constraints are allowed to be > > broken (ideally transiently). > I want to focus on this. IMO giving up schema validitiy for any datastore is > unacceptable price. Pre-NMDA devices had full model support in operational > data (all YANG constrains part of the model without discrimination were > enforced).
There was a long debate about the value of returning the true operational state. What do you do if the operational state is invalid? A server can reject configuration changes if they lead to invalid state, a server can not reject reality. > If this is about to change it will compromise interoperability > and a significant portion of the client implementation workload that can be > automated will need to be coded in hand and tested. Unresolved leafrefs, > undefined behaviour of different implementations removing different > configuration nodes in violation of YANG semantic constraints (which I do > not think can be so clearly separated from the syntactic constraints when > one considers types like leafref, instance-identifier etc.) and the > corresponding side effects based on the server implementators own creativity > is eventually going to create more problems. > > 1. IMO the only acceptable solution is to have YANG valid operational > datastore at all times. operational like any other datastore MUST be valid > YANG data tree and it has to be a system implementation task to consider all > complications resulting from the removal of the resources leading to any > data transformations. If this is difficult or impossible other mechanisms to > flag missing resources should be used (e.g. > /interfaces/interface/oper-status=not-present) This sounds like a useful > contract providing the value of a standard the alternative does not. As said above, it is impossible to report valid operational state if the operational state is not valid according to the models. > 2. Even with the change in 1. I do not see the removal of intended > configuration nodes from operational as a solution worth implementing on our > servers. I do not see a real world plug-and-play scenario that can be > automatically solved without specific additions to the models e.g. > /interfaces/interface/oper-status=not-present is oversimplified solution but > it needs to be extended exactly as much as the solution provided by the > removal of config true; nodes without the sacrifice of YANG validity of > operational. Your thinking is likely wrong. <operational> reports the operational state. It may have little in common with <intended>. Trying to derive operational from intended is likely a not well working approach. > 3. Solutions like /interfaces/interface/admin-state stop working. With the > interface removed you can no longer figure if the if-mib has or does not > have the interface enabled so an operator has to use SNMP or wait for a > replacement line card to be connected to figure this bit of information. At least on my boxes, if I remove a line card, the interface also disappears in SNMP tables. Stuff that is operationally not present is simply operationally not present. > My > interpretation of the MAY as requirement level in sec. 5.3. The Operational > State Datastore (<operational>) is that plug-and-play solutions can be > implemented without this limited approach that has the same problem as the > pre-NMDA only now we have to have /interfaces-state to keep config false; > data relevant to hardware that is configured but not present: > > configuration data nodes supported in a configuration datastore > MAY be omitted from <operational> if a server is not able to > accurately report them. > > I realize this discussion comes late. I have stated my objections to this > particular part of the NMDA draft earlier. I believe there is a conceptual misunderstanding. I think there never was a requirement that a server reports the state of hardware that is not present. /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/> _______________________________________________ netmod mailing list netmod@ietf.org https://www.ietf.org/mailman/listinfo/netmod
