Re: [netmod] submodules the hidden benefits

Juergen Schoenwaelder <j.schoenwaelder@jacobs-university.de> Wed, 05 August 2020 16:48 UTC

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Date: Wed, 5 Aug 2020 18:48:20 +0200
From: Juergen Schoenwaelder <j.schoenwaelder@jacobs-university.de>
To: tom petch <ietfc@btconnect.com>
Cc: "netmod@ietf.org" <netmod@ietf.org>
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Subject: Re: [netmod] submodules the hidden benefits
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As a data point, RFC 7407 uses sub-modules. The sub-modules more or
less reflect SNMPv3's modular architecture, the different transports
are for example separated out as sub-modules. I guess we also used
sub-modules back then because we wanted to see how this works in an
IETF context (RFC 7407 was approved/published 6 years ago, we were
still learning how to use YANG at that time).

I personally meanwhile believe that sub-modules add complexity with
little extra value but this view surely is not shared by others.
Anyway, people using them should have a good reason for using them.
Since SNMPv3 has a great modular architecture, it makes sense to
structure the YANG modules accordingly and instead of having many
ietf-snmp-<foo> modules, sub-modules came in handy to have everything
in a single namespace. For technologies that do not have a modular
architecture that can be followed, creating modular sub-modules is
likely not worth the effort.

/js

PS: I am not sure that sub-modules are necessarily harder to
    review. For the crypto YANG modules, we have several intertwined
    modules, they are likely as complex to review as if they were all
    sub-modules sharing a single namespace - or a single module with
    all definitions in one big module.

On Wed, Aug 05, 2020 at 04:20:17PM +0000, tom petch wrote:
> Looking at an I-D with endless submodules, I am left thinking
> 
> Costs
> 
> greater in size
> more complex to understand
> harder to review
> more likely to have undetected errors
> 
> Benefits
> 
> 
> 
> What am I missing?  I have only ever seen one such module in the IETF that I can recall and it is draft-ietf-idr-bgp-model and AFAICT it would be smaller, simpler, easier to understand if it were done with grouping instead of submodule.
> 
> Tom Petch
> 
> _______________________________________________
> netmod mailing list
> netmod@ietf.org
> https://www.ietf.org/mailman/listinfo/netmod

-- 
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/>