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Re: [netmod] Comment on draft-clacla-netmod-yang-model-update-02

Ladislav Lhotka <lhotka@nic.cz> Wed, 15 November 2017 13:05 UTC

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From: Ladislav Lhotka <lhotka@nic.cz>
To: netmod@ietf.org
Date: Wed, 15 Nov 2017 21:06:35 +0800
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Archived-At: <https://mailarchive.ietf.org/arch/msg/netmod/NdyrkdPIBPfN5Ek7aZPlsBHq6bA>
Subject: Re: [netmod] Comment on draft-clacla-netmod-yang-model-update-02
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On Wed, 2017-11-15 at 12:17 +0100, Martin Bjorklund wrote:
> Balazs Lengyel <balazs.lengyel@ericsson.com> wrote:
> > The server MAY implement obsoleted nodes or MAY NOT. This may or may
> > not  is not good enough as a contract for the management client.  My
> > problem is that the current solution is just not good enough. IMHO we
> > need to change it.
> 
> Note that if a server implements version 1 of a module, and then the
> module doesn't change, but the server in the next sw version drops
> support for the module, the client will also be unhappy.  We (the
> IETF) can't have rules for these kinds of things.

If the server drops support for a module, then that module has to disappear from
YANG library, so it is a priori known that it happened. With deprecated/obsolete
nodes, a server may drop their support without any notice, within the same
module&revision. 

> 
> > Even after semver you can still obsolete the old stuff and provide the
> > new stuff with a new name, although that might not be the common
> > practice.  Which is a good thing, as I believe it is sometimes better
> > to correct existing definitions then to replace them.
> 
> But you still want to require servers to implement even obsolete
> nodes?

I think with semver support there will be no need for the "status" statement -
the nodes just get removed and version number bumped.

Lada

> 
> 
> /martin
> 
> 
> > 
> > regards Balazs
> > 
> > 
> > On 2017-11-15 16:53, Martin Bjorklund wrote:
> > > Exactly.  With the current solution, the sever can still implement the
> > > deprecated or obsolete nodes in order to support old clients.
> > > 
> > > With a MAJOR update in a semver world, it means that the old nodes are
> > > removed (or rather, possibly, that the old nodes have new syntax
> > > and/or semantics).
> > > 
> > > 
> > > 
> > 
> > -- 
> > Balazs Lengyel                       Ericsson Hungary Ltd.
> > Senior Specialist
> > Mobile: +36-70-330-7909 email: Balazs.Lengyel@ericsson.com
> > 
> 
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-- 
Ladislav Lhotka
Head, CZ.NIC Labs
PGP Key ID: 0xB8F92B08A9F76C67

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