Re: [netmod] [Netconf] magic leaf 'type' in IETF interfaces

Andy Bierman <> Tue, 18 December 2018 18:14 UTC

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From: Andy Bierman <>
Date: Tue, 18 Dec 2018 10:14:36 -0800
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To: Jan Lindblad <>
Cc: Balázs Lengyel <>, "" <>, "" <>
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Subject: Re: [netmod] [Netconf] magic leaf 'type' in IETF interfaces
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On Tue, Dec 18, 2018 at 5:37 AM Jan Lindblad <> wrote:

> Hi,
> While I agree with Martin, in our systems we have a number of places,
> where the system does create configuration in running, due to
>    - different levels of automation and autonomous algorithms kick-in
>    - the created config needs to be possible to be further modified by
>    the operator
>    - the created config needs to be referenced from operator created
>    config
>    - the created config is not always ephemeral, it might need to be part
>    of backup/restore
> This is only a sampling from "the list of excuses". I have heard many
> more. The road to hell is paved with good intentions, however. If we want
> to build automation based on sound theory, clearly separating the orders
> from managers from a system's own operational view is key, IMO.
> Reliability, security, accountability are growing in importance, and they
> all play in this direction.
> We may not need to standardize rules to outlaw the above; the market will
> take care of that. What we need to ensure is that it is possible to be
> standards compliant without having to implement design excuses like these.
NMDA has a lot of room for proprietary mechanisms for converting <running>
to <intended>.
Many times the features desired by engineers exceed the capabilities of
YANG, such as
a dynamic default leaf.  YANG allows a simple constant, and no business
logic to pick the default.
This is a very valid use of "server auto-magic".

Maybe a future version of YANG can improve the client visibility into this

Best Regards,
> /jan


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