Re: a draft about on-link and submit prefixes

[神明達哉 <[e-mail]>]

At Tue, 14 Mar 2017 13:06:50 +0900,
Lorenzo Colitti <[e-mail]> wrote:

> > I've submitted a new individual draft on the separation between
> > on-link and (SLAAC) subnet prefixes, at the risk of stating the
> > obvious: https://datatracker.ietf.org/doc/draft-jinmei-6man-prefix-
> > clarify/
>
>
> Thanks for attempting to clarify the topic. I think it is useful to do so,
> since the distinctions here are very subtle and even many in the WG (not to
> mention in the IETF or in the industry) are not fully aware of their
> implications.

Thanks for reading the draft and for the prompt feedback.

> If possible, I would suggest making this document even more general. It's
> mostly geared to how implementations treat PIOs, and refers to RFC 4861 and
> RFC 4862, but really I think the clarifications it makes have much broader
> impact. As I see it, the core issues here are:

I see the possibility of generalization.  In particular, we could
generalize the term/concept of "subnet prefix" so that it doesn't
limit the context to SLAAC.  At least in the initial version of the
draft, however, I intentionally focused on the prefixes advertised via
PIOs in order to avoid distraction or unnecessary controversy from the
primary clarification I wanted to make first (which itself was deemed
to be sufficiently subtle).  If others also think it helpful to
generalize the discussion as a continuation of this draft, I'm happy
to revise the draft that way.

A few quick comments on the specific points:

>    - IPv6 addresses don't specify any on-link information

This one actually seems to be covered by RFC5942 (although it's a
different question whether it's well understood and/or whether a
further clarification attempts help).

>    - For most (but not all) unicast addresses, subnet prefixes are 64 bits
>    per RFC 4291.

I'm not sure if this is directly relevant to the separation of on-link
and subnet prefixes.

>    - A given subnet prefix can be spread across multiple links, and a given
>    link can support multiple subnet prefixes.

Same for the latter.  I see the former is related to the fact that
on-link prefixes are independent from subnet prefixes, but I'm not so
sure if this will be in the scope of "generalized clarification".

--
JINMEI, Tatuya