[netmod] convert it and not throw an error was Re: 6021 ipv4-prefix

----- Original Message -----
From: "Mikael Abrahamsson" <swmike@swm.pp.se>
To: "Randy Presuhn" <randy_presuhn@alumni.stanford.edu>
Cc: <netmod@ietf.org>
Sent: Thursday, May 02, 2019 12:35 PM

> On Wed, 1 May 2019, Randy Presuhn wrote:
>
> > Hi -
> >
> > On 5/1/2019 12:46 PM, Mikael Abrahamsson wrote:
> > ....
> >> Where is the text that tells the server implementor whether to
throw an
> >> error when client commits non-zero bits, or to just throw the bits
away
> >> and store the value in the canonical format?
> >
> > Such text would be an inappropriate constraint the server's
> > internal representation.  We should only specify
> > the externally-visible behaviour: that the reported value
> > will be in the canonical format.  Whether an implementation
> > preserves extraneous cruft in its internal representation is
> > purely an implementation decision, and not subject to
standardization.
>
> I am talking about what goes on the wire. If the client does an
> edit-config with ipv6-prefix 2001:db8::1/64, should the server convert
> this into 2001:db8::/64 or throw an error on the edit-config
operation.
>
> Jurgen seems to say it should convert it and not throw an error, and
I'd
> like text to say that indeed, this is proper behaviour. Nobody has so
far
> been able to tell me where this text currently is, so that's why I'm
> asking for it to be added. Either this should go into an update to
> https://tools.ietf.org/html/rfc7950#section-9.1 or it should go into
each
> and every definition of types (or both of them).

Mikael

How about RFC791, still much quoted in all aspects of the work of the
IETF?

" In general, an implementation must be conservative
  in its sending behavior, and liberal in its receiving behavior.  That
  is, it must be careful to send well-formed datagrams, but must accept
  any datagram that it can interpret (e.g., not object to technical
  errors where the meaning is still clear)."

We did not have MUST in those days, but had we, this would have been one
IMHO.

Tom Petch

> >> It seems it should "fix it", so we should
> >> have text that reflects this.
> >
> > False dichotomy.  An implementation might actually preserve
> > those bits, though of course they'd never be seen again (at
> > least not on a netconf interface) since the netconf server
> > will always behave as though the value were in its canonical
> > form, regardless of the internal representation.
>
> Again, I am talking about what goes on the wire, what is seen when
issuing
> "get" or "edit-config" etc.
>
> --
> Mikael Abrahamsson    email: swmike@swm.pp.se
>
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