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

[[e-mail]]

Hi Bob, 

Thank you for double checking. 

I confirm that your initial AD review message I received was truncated (see attached). 

Will update the draft to take into account the missing part.

Cheers,
Med

> -----Message d'origine-----
> De : Rob Wilton (rwilton) [mailto:[e-mail]]
> Envoyé : vendredi 18 septembre 2020 19:21
> À : BOUCADAIR Mohamed TGI/OLN <[e-mail]>; opsawg
> <[e-mail]>
> Cc : [e-mail]
> Objet : RE: AD review for draft-ietf-opsawg-model-automation-
> framework-04
> 
> Hi Med,
> 
> The changes that you have made look good.  But I had some comments
> at the end of my review email that it doesn't look like you have
> responded to, or actioned.  Hence, I'm wondering if my review email
> might have been truncated, or the end of it missed (from "Also, I
> ...") onwards (copied below).
> 
> 
> 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.
> 
> Also, I wouldn't regard schema mount as necessarily being specific
> to device models, and could be used for network and service YANG
> models as well.  Although there may not be a good place to put it.
> 
> 14.
> A.3.2.  Device Models: Samples
> 
> As above, having a section for interfaces/interface management would
> be useful.  I also think think it would be good to have a section
> for device management (e.g. system, nacm)
> 
> I would potentially reorder the list of modules:
>    - Move Core Routing up, near the top of the list (above BGP)
>    - L2VPN (next to) but before EVPN
>    - Perhaps move BGP down, and having routing policy next to it
> might be helpful
>    - NAT and Stateless Address Sharing could perhaps move down.
> 
> 
> Editorial nits to check:
> 
> 1. Network Operator -> network operator?
> 2. Perhaps "it can accommodate modules" -> "it can also accommodate
> modules"?
> 3. "follow top-down approach" -> "follow a top-down approach"
> 4. "validated during the implementation time" -> "validated during
> implementation"
> 5. For Diagram A2, possibly could have just used the full names and
> not requried the legend.
> 6. "[RFC8345] with TE topologies specifics." -> "[RFC8345] with TE
> topology related content."
> 7. "Network Topology Models" -> Network Topologies Model"?
> 8. "TE Topology Models" => "TE Topology Model"?
> 9. "Layer 3 Topology Models:" -> "Layer 3 Topology Model:"
> 10. "Layer 3 topologies specifics" -> "Layer 3 topology specifics"
> 11. "Layer 2 Topology Models:" -> "Layer 2 Topology Model:"
> 12. "Layer 2 topologies specifics" -> "Layer 2 topology specifics"
> 13. Figure 4: "Config Validate" -> "Config Validation", and realign
> "Monitoring"
> 
> Please can you check?
> 
> Regards,
> Rob
> 
> 
> > -----Original Message-----
> > From: [e-mail] <[e-mail]>
> > Sent: 08 September 2020 13:28
> > To: Rob Wilton (rwilton) <[e-mail]>; opsawg
> <[e-mail]>
> > Cc: [e-mail]
> > Subject: RE: AD review for
> > draft-ietf-opsawg-model-automation-framework-04
> >
> > 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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--- Begin Message ---

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?

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?

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 (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.

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?  Does the potential existence of these East-West APIs need to be described in any more detail?


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?


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.

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.


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?

9.
   o  Tunnel identities to ease manipulating extensions to specific
      tunnels [RFC8675].

I found this sentence slightly unclear.  Perhaps it could be reworded?

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.

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.

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.

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

--- End Message ---