Re: [YANG] default values

Andy Bierman píše v St 16. 01. 2008 v 06:08 -0800:

> YANG has the "DEFVAL with teeth" that SMIv2 never had.
> In YANG the default MUST be supported by the agent.
> It is not just a suggestion.  This means the manager can
> actually pay attention to the default defined in the data model,
> and change it only if needed.

I understand this but, as a matter of fact, most defaults in protocol
standards are of the SHOULD class at most. In a vendor-neutral
environment, it would be much safer if each device fills all the blanks.

> 
> On large NE devices, it is common practice to keep the CLI config file
> as small as possible by only including non-default values.  NETCONF
> needs to support this feature as well, and YANG leaf/typedef default does that.

Yes, but this is only possible because the CLIs are vendor-specific. It
is quite common that different vendors use different defaults. If you
try to enforce a single default in the data model, the vendor that
thinks otherwise will come up with an entirely new data model (namespace
URI) which is IMO much worse for interoperability.

Lada

-- 
Ladislav Lhotka, CESNET
PGP Key ID: E74E8C0C

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