Re: [OPSAWG] AD review for draft-ietf-opsawg-model-automation-framework-04

[[e-mail]]

Rob,

FWIW, an updated version with changes to address your review is available online:

URL:            https://www.ietf.org/id/draft-ietf-opsawg-model-automation-framework-05.txt 
Status:         https://datatracker.ietf.org/doc/draft-ietf-opsawg-model-automation-framework/ 
Htmlized:       https://datatracker.ietf.org/doc/html/draft-ietf-opsawg-model-automation-framework 
Htmlized:       https://tools.ietf.org/html/draft-ietf-opsawg-model-automation-framework-05 
Diff:           https://www.ietf.org/rfcdiff?url2=draft-ietf-opsawg-model-automation-framework-05

Please let us know if any of your comments is still pending. Thank you.

Cheers,
Med

> -----Message d'origine-----
> De : [e-mail]
> [mailto:[e-mail]]
> Envoyé : lundi 7 septembre 2020 16:35
> À : Rob Wilton (rwilton) <[e-mail]>; opsawg <[e-mail]>
> Cc : [e-mail]
> Objet : RE: AD review for draft-ietf-opsawg-model-automation-
> framework-04
> 
> Hi Rob,
> 
> Thank you for the detailed review.
> 
> Please see inline.
> 
> I let my co-authors further comment.
> 
> Cheers,
> Med
> 
> > -----Message d'origine-----
> > De : Rob Wilton (rwilton) [mailto:[e-mail]] Envoyé :
> vendredi
> > 4 septembre 2020 19:22 À : opsawg <[e-mail]>;
> > draft-ietf-opsawg-model-automation-
> > [e-mail]
> > Objet : AD review for draft-ietf-opsawg-model-automation-framework-
> 04
> >
> > Apologies for the lengthy delay in performing the AD review.
> >
> > I found that this document to be well written so I would like to
> thank
> > the authors, WG, and doc shepherd for that.  My more significant
> > comments relate to questions on the scope of this architecture.
> >
> >
> > More significant comments:
> >
> > 1. By "Data Model" does this document mean "YANG data model"?  And
> if
> > so, does it take this meaning all through this document, or only
> some
> > of the time?
> >
> 
> [Med] "Data Model" is used as a generic term as per rfc3444#section-4.
> We are using "YANG data models" or "YANG module" when we wanted to be
> more specific about the DM flavour.
> 
> I double checked the text to make sure this is consistently used along
> the document. Updated some occurrences in the text where the use of
> "YANG data model" is more accurate.
> 
> > 2. Generically, service data models are not necessarily written in
> > YANG (e.g., I think that MEF are defining them using OpenAPI).  So,
> > related to (1), is this architecture intended to be tied to only
> > service models defined in YANG, or be more broadly applicable?
> 
> [Med] We don't require the service models to be YANG-modelled (see for
> instance the example depicted in Figure 2). That's said, the use of
> YANG in all levels would ease mapping operations.
> 
> >
> > 3. This architecture seems to quite strictly represent 3 layers
> > (service, network, device).  Does it envisage that these layers may
> > themselves be deconstructed?  E.g. a customer service can be
> > constructed from underlying services
> 
> [Med] Yes, that's not excluded. The architecture can be "recursive"
> (Such as rfc8597#section-3.1.3).
> 
>  (e.g., as discussed in section
> > 3.1, but more as an East-West relationship).  Similarly, device
> models
> > could also be deconstructed, e.g., if the dataplane is decoupled
> from
> > the control plane, or if a device itself acts as a controller
> managing
> > other devices.
> 
> [Med] The document does not make assumptions on the organic structure
> or where the functions are provided. Having a controller co-located
> with other YANG-controlled functions is not excluded.
> 
> >
> > 4. My minimal understanding of the MEF LSO architecture was that
> they
> > put quite a lot of emphasis on East-West models, probably at the
> > service layer. Is this effectively the same as what is described in
> > Figure 1 in section 3.1?
> 
> [Med] Inter-domain interactions between two services or two adjacent
> networks are not shown in Figure 1. This figure focuses mainly on the
> interface between a service and an underlying network.
> 
>   Does the potential existence of these East-
> > West APIs need to be described in any more detail?
> >
> 
> [Med] A network can act as a "customer" and request services from
> other networks. The peer network will then follow the levels depicted
> in the architecture. This is for example hinted in this text for
> example:
> 
>    o  allow customers (or Network Operators) to dynamically adjust the
>       network resources based on service requirements as described in
>       Service Models (e.g., Figure 2) and the current network
>       performance information described in the telemetry modules.
> 
> We can add some more text if needed.
> 
> Section 4.3 discusses how multi-domain mapping can be handled at the
> server level. This assumes that the interaction is not between the
> domains themselves but driven by the service layer.
> 
> >
> > Minor comments/clarifications:
> >
> > Section 3.1: Data Models: Layering and Representation
> >
> > 5. Network Models are mainly network resource-facing modules; they
> >    describe various aspects of a network infrastructure, including
> >    devices and their subsystems, and relevant protocols operating at
> > the
> >    link and network layers across multiple devices (e.g., network
> >    topology and traffic-engineering tunnel modules).
> >
> > Would it be fair to say that Network Models might be protocol
> > specific, or might be generalized?  If so, is that worth mentioning?
> >
> 
> [Med] Network models may include some protocol-specific parameters.
> I'm neutral whether this needs to be mentioned in the text.
> 
> >
> > 6. Re: DOTS & RFC 8783, I'm not sure how well the YANG model defined
> > in that drafts fits into the category of Service YANG model.
> >
> 
> [Med] RFC8783 defines the filtering service requested by a
> client/customers; how this request triggers the selection of the
> devices that need to be configured, the exact set of ACLs, and the
> enforcing of the ACLs in these devices is managed by other layers
> (RFC8519). From that perspective, we do think that the module in RFC
> 8783 satisfies the following from RFC8309:
> 
>    "Details
>    included in the service model include a description of the service
> as
>    experienced by the customer, but not features of how that service
> is
>    delivered or realized by the service provider. "
> 
> > 7. Pipe vs hose vs funnel.  Are these terms, or do they need to be,
> > defined somewhere?  In particular it is not obvious to me what the
> > distinction is between pipe vs hose.
> 
> [Med] "pipe" means that only point-to-point communications are allowed
> while "hose" means that communications from one to N is allowed.
> 
> We can text to explain this.
> 
> >
> >
> > In Appendix A:
> > 8. Would it be useful to discuss or reference YANG Catalog (as a
> > source of querying YANG models), the public YANG github repository,
> or
> > YANG module tags as a method of organizing YANG models?
> >
> 
> [Med] Good point. Will consider adding some text.
> 
> > 9.
> >    o  Tunnel identities to ease manipulating extensions to specific
> >       tunnels [RFC8675].
> >
> > I found this sentence slightly unclear.  Perhaps it could be
> reworded?
> >
> 
> [Med] Fair point. Updated to :
> 
> " o  Tunnel identities: [RFC8675] defines a collection of YANG
> identities used
>      as interface types for tunnel interfaces."
> 
> > 10.
> >    o  Generic Policy Model:
> >
> >    The Simplified Use of Policy Abstractions (SUPA) policy-based ...
> >
> > It does not like this draft is going anywhere, and I'm not convinced
> > that it is really helpful to reference it here.  Or, if it must be
> > referenced, it should be caveated accordingly.
> >
> 
> [Med] Fair enough. I tend to agree with you.
> 
> > 11.
> > A.3.  Device Models: Samples
> >
> > I think that it would be helpful if this diagram, and the list in
> > section A3.2, had references to the interface YANG module.
> >
> 
> [Med] Point taken.
> 
> > 12.
> > A.3.1.  Model Composition
> >
> >    o  Device Model
> >
> >    [I-D.ietf-rtgwg-device-model] presents ...
> >
> > Again, I'm not sure that this is a helpful reference, given that the
> > approach defined in this draft did not gain traction, and instead, a
> > more loosely coupled structure was preferred.  E.g., I see that tags
> > (and arguably schema mount) solve this organizational problem in a
> > more flexible way.
> >
> 
> [Med] Fair point.
> 
> > 13.
> > A.3.1.1.  Schema Mount
> >
> >    That capability does not cover design time.
> >
> > This sentence is unclear on its own.  Perhaps either expand it or
> > remove it
> 
> [Med] OK.


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