Re: 6man w.g. last call for <draft-ietf-6man-default-iids-11.txt>

[神明達哉 <[e-mail]>]

At Wed, 18 May 2016 22:19:57 -0700,
Alissa Cooper <[e-mail]> wrote:

> >> Let's call a lemon a lemon: Asking to embed a layer-2 identifier/address
> >> in a layer-3 address is extremely bad.
> >
> > I don't have a strong position on this matter itself, but my
> > understanding of the sense of the wg is that this is controversial,
> > and at least far from a clear consensus.  To repeat myself, *my*
> > concern on this last call is that it's not even clear, at least to me,
> > if this draft tries to say embedding a link-layer address is, whether
> > it's randomized or not, "extremely bad" (and must therefore be
> > prohibited).  If that's the intent, it should be clearly stated
>
> The draft makes just about a clear a statement in this vein as is possible:
>
> "By default, nodes SHOULD NOT employ IPv6 address generation schemes
>    that embed the underlying link-layer address in the IID.”
>
> Note that this statement does not prohibit anything, nor does it
> make a normative (in the moral sense) judgment. It just states the
> recommendation, which is the point of the document.

I've heard phrases like "it does not prohibit anything", and it always
confused me.  So let me ask essentially the same question again.
Assume there's an implementation that uses randomized link-layer
addresses and that implementation builds the IID for IPv6 address by
embedding that link-layer addresses by default.  Would that
implementation be considered to be non-compliant to the above SHOULD
NOT?  Without any qualifier to the link-layer address, I would
interpret it as such implementation is non-compliant.  But if so, that
contradicts statements like "it doesn't prohibit anything".  Hence my
confusion.  So, what's the author's intent?  Would such an
implementation be considered non-compliant to this SHOULD NOT?

> I appreciate that not everyone on the list agrees with this
> recommendation. But I find the claim that this recommendation is
> unclear to be difficult to understand. That is, I can’t think of a
> way to convey the same recommendation that would be clearer. If you
> can, please suggest text.

See above, it's not about agree or disagree with a recommendation.  I
didn't even know a particular type of implementation would be
considered non-compliant to a specific normative text of this draft.
Once I understand the intent, then I can agree or disagree with it,
or, if we agree with the intent but the text isn't clear enough I'm
willing to suggest alternative text.

--
JINMEI, Tatuya