Subject: [netmod] Quirky YANG

From: tom petch <[email-masked]>
Date: Wed, 3 Oct 2018 16:11:13 +0000

I wonder if anyone else on this list has looked at
 https://datatracker.ietf.org/doc/draft-ietf-softwire-yang/
currently in IETF Last Call.

It provides management for three tunnel types, Lw4o6, MAP-E and MAP-T
betweeen CPE and Border Relay.  It defines a CPE module, a BR module and
a module of common definitions.

It does not provide identities for the three tunnel types; rather, where
it augments "/if:interfaces/if:interface" it specifies
    when "if:type = 'ianaift:tunnel'";
which to me says that a MAP-E (e.g.) specific object will get added to
each and every tunnel of whatever type, which seems excessive.

Second, it defines four features, softwire-ce:algorithm (i.e.
MAP-E/MAP-T) and softwire-ce:binding (i.e. Lw4o6) in the CPE module and
then again softwire-br:algorithm and softwire-br:binding in the BR
module.  It is unclear to me, from the I-D, whether support is for MAP-T
and MAP-E; or either MAP-T or MAP-E - I find the I-D ambiguous on that
point - but I would have expected there to be either two - Lw4o6 and
MAP-ET - or three - Lw4o6, MAP-E and MAP-T features, not four; and for
the features to be defined, along with tunnel identities, in the common
module.

Odd, IMHO.

Tom Petch

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From: Juergen Schoenwaelder <[email-masked]>
Date: Wed, 3 Oct 2018 18:43:29 +0200

Well, make sure you send your comments to softwire since they have to
sort this out.

/js

On Wed, Oct 03, 2018 at 04:11:13PM +0000, tom petch wrote:
> _______________________________________________
> netmod mailing list
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-- 
Juergen Schoenwaelder           Jacobs University Bremen gGmbH
Phone: +49 421 200 3587         Campus Ring 1 | 28759 Bremen | Germany
Fax:   +49 421 200 3103         <https://www.jacobs-university.de/>

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From: tom petch <[email-masked]>
Date: Thu, 4 Oct 2018 17:26:17 +0000

----- Original Message -----
From: "Juergen Schoenwaelder" <[email-masked]>
Sent: Wednesday, October 03, 2018 5:43 PM

> Well, make sure you send your comments to softwire since they have to

Indeed.

The subtext to my query was that if this had had aYANG doctor review,
which I assumed it would have had by now, then there was something I was
misunderstanding about YANG identities and features, but perhaps it is
my understanding of when YANG doctor reviews take place that I was
missing:-)

Tom Petch

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From: Juergen Schoenwaelder <[email-masked]>
Date: Thu, 4 Oct 2018 21:03:49 +0200

> my understanding of when YANG doctor reviews take place that I was

Just to be clear: YANG doctors won't catch everything and hence YANG
doctor reviews complement other reviews, they do not replace the need
for other people's reviews. In particular, YANG doctors usually do not
understand what is being modeled. Getting the semantics of lets say
identities right remains the job of the working group. And the working
group is ultimately responsible for what it produces.

/js