Re: [Detnet] Éric Vyncke's No Objection on draft-ietf-detnet-yang-19: (with COMMENT)

[Don Fedyk <[e-mail]>]

Hi Eric

Comments inline [Don]

Thanks
Don

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Subject: [Detnet] Éric Vyncke's No Objection on draft-ietf-detnet-yang-19: (with COMMENT)

Éric Vyncke has entered the following ballot position for
draft-ietf-detnet-yang-19: No Objection

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COMMENT:
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# Éric Vyncke, INT AD, comments for draft-ietf-detnet-yang-19

Thank you for the work put into this document.

Please find below some non-blocking COMMENT points (but replies would be
appreciated even if only for my own education).

Special thanks to János Farkas for the shepherd's detailed write-up (using the
old template) including the WG consensus and a simple but present justification
of the intended status.

Please note that Jean-Michel Combes is the Internet directorate reviewer (at my
request) and you may want to consider this int-dir review as well when it will
be available (no need to wait for it though):
https://datatracker.ietf.org/doc/draft-ietf-detnet-yang/reviewrequest/18768//

I hope that this review helps to improve the document,

Regards,

-éric

# COMMENTS (non-blocking)

## Section 7

The following points may be purist or even pedantic, but here they are:

### Circular references

'traffic-profile' includes leaves such as 'member-app' and 'app-flow' has a
leaf 'traffic-profile'. This can lead to *inconsistency* if the values are not
compatible. Do YANG/netconf have functions to retrieve which 'app-flow' use
'traffic-profile' ?

Or did I miss something ?

[Don]
These items are read only leaf-references to the applications, service sub-layer and forwarding sub-layers that reference the traffic profile.  (Defined the traffic profile and allowing applications or service-sublayer of forwarding sub-layer to reference them saves having to repeat traffic profiles that are common.)  
A system can populate these back pointers to the applications refencing them if it desires, and the schema can display the reference list. It is not what I would call circular but forward and backward. 

When you are looking at an application, you can see which profile it uses. When you look at a profile you can see which application, service sub-layer or forwarding sublayer is using it is using it. But the configuration is only at the application, service sub-layer or forwarding sublayer to point to the profiles. 

### Leaves names

Why the leaves under 'traffic-profile' are named 'member-app',
'member-fwd-sublayer' rather than 'member-app-flows' and 'member-forwarding' to
match the naming used elsewhere ?

[Don]
We used lists titled:  
member-app
member-service
member-fwd-sublayer

Elsewhere we use: 
        +--rw app-flows
        |  +--rw app-flow* [name]
        +--rw service
        |  +--rw sub-layer* [name]
        +--rw forwarding
           +--rw sub-layer* [name]

So, I concur not totally consistent. 
I suggest: 
member-app-flows
member-svc-sublayers
member-fwd-sublayers

Would be more consistent  (And I will manage the ripple effect this has on the examples.) 
Eg: 
       "member-app-flows": [
          "app-1",
          "app-2"
        ]


## IPv6 in the YANG module

I am uneasy with the model of an IPv6 flow

### inet:ip-address-no-zone

The use of inet:ip-address-no-zone is fine when purely matching on an IPv6
packet, but this also means that link-local addresses cannot be used probably.
Is it on purpose ?

[Don]
I was not aware that link local could not be expressed as inet:ip-address-no-zone  I thought inet:ip-address-no-zone   was simply ip-address without the extra characters of zone.  IE purely hexadecimal alpha numeric IPv6 format RFC 6991.  On further reading I see that is not correct. 

I think we need the to replace with:
inet:ip-address for Next-hops 

When specifying interfaces.  Good catch. -- The routing YANG uses ip-address for next-hops.

We use prefixes for matching packets. 



### protocol-next-header

```
      description
        "Internet Protocol number.  Refers to the protocol of the
         payload.  In IPv6, this field is known as 'next-header',
         and if extension headers are present, the protocol is
         present in the 'upper-layer' header.";
```

This description is rather vague... It should be really specific when using
IPv4. For IPv6 with extension headers, there is no protocol in 'upper-layer'
header.

[Don] suggest.
      description
        "Internet Protocol number.  Refers to the protocol of the
         Payload for IPv4.";

## Section 13.2

Reference IEEE8021QCX is marked as 'superseded' since 2022 at
https://ieeexplore.ieee.org/document/9212765 apparently by
https://ieeexplore.ieee.org/document/10004498.

[Don] Thanks -  will update.   

## Appendix B

Thank you for using IPv6 examples and very nice SVG diagrams.

Albeit using flows 2001:db8::1/128 <-> 2001:db8::8/128 seems a little
unrealistic as both nodes are probably in the same layer-2 link. But, DTN also
work on a layer-2 link w/o actual layer-3 routing. Same for the IPv4 examples.
[Don] We ran into using non-ietf document addresses earlier - so the numbers are within IETF doc standard ranges but yes, the examples might somewhat unrealistic. I hesitate to change and make another mistake.

You may also want to refresh the dates to 2024 rather than 2020 ;-
[Don] Sure. 

Having some examples is really a good thing, I am just slighlty concerned by
the large amount of them in this document. It is a matter of taste, so no need
to reply.
[Don] it was WG consensus that a PowerPoint presentation of examples from a meeting would be good to capture in the document. Little did I know a picture is worth some 3000 xml tags. 



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