Re: [YANG] default values

Juergen Schoenwaelder píše v Čt 17. 01. 2008 v 14:57 +0100:
> Regarding defaults, the question boils down to whether a NETCONF
> client can assume that specified defaults are used or whether to be on
> the safe side the client has to either set defaults itself or check
> what was set by the server.

At the start of a NETCONF session, the values in the
running/startup/whatever configuration may be different even if the
server's factory defaults follow the standards. The client can't IMO
safely avoid checking or setting all variables in server's
configuration. 

> 
> The alternative would be to have a mechanism allowing implementations
> to post the defaults they are going to use rather than hard wiring
> defaults in the specification. So a vendor can augment a standard with
> the defaults that the vendor's implementation is using. This surely
> adds some complexity. An even further reaching mechanism would be to
> make the defaults being used by an implementation itself writable,
> e.g. by introducing a template mechanism which adds defaults for stuff
> not defined explicitely by a NETCONF client.
> 
> Our goal was to start with something simple, allowing us to add more
> powerful mechanism via extensions over time once we see that they are
> really needed (that is there is enough uptake of NETCONF / YANG).

I think this applies to the default statement, too. I am arguing it's
not needed for NETCONF operation and may complicate things.

Lada

-- 
Ladislav Lhotka, CESNET
PGP Key ID: E74E8C0C

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