Re: draft-bourbaki-6man-classless-ipv6-00

[David Farmer <[e-mail]>]

On Fri, Jun 9, 2017 at 9:50 AM, Fernando Gont <[e-mail]> wrote:

> On 06/09/2017 05:31 PM, David Farmer wrote:
> >
> >
> > On Fri, Jun 9, 2017 at 1:36 AM, Lorenzo Colitti <[e-mail]
> > <mailto:[e-mail]>> wrote:
> >
> >     On Fri, Jun 9, 2017 at 1:24 PM, Fernando Gont <[e-mail]
> >     <mailto:[e-mail]>> wrote:
> >
> >         > However, I think IPv6 implementations that don't support manual
> >         > configuration must be able to reject non-64 bit IIDs, since
> that is the
> >         > standard. Saying "SHOULD be 64 bits long" means they "MAY be
> /81, /99 or
> >         > /123", and those are against BCP 204 (RFC 7934).
> >
> >         BCP204 talks about multiple addresses. As long as whatever
> prefix is
> >         employed allows for multiple addresses, I don't see how that goes
> >         against BCP204.
> >
> >
> >     That's not true at all. As an example: see if you can build a
> >     network that uses a /99 and satisfies the recommendations in section
> >     8 or BCP 204.
> >
> >
> > Yes, to meet the specific RECOMMENDATIONS in BCP204 /64 is necessary.
>
> I don't see anything in BCP204 where /64 is a MUST or even RECOMMENDED.
>

It's not in the normative language, but it is part of the RFCs
recommendations section, see below.


> > It seems to me that extremely long prefixes like /120 or longer are
> > likely unable to achieve the intent of BCP204 for any significant number
> > of hosts. However, anything in the range /112 or shorter should have
> > plenty of address to achieve the intent of BCP204 for a quite reasonable
> > numbers of hosts, at least many hundreds of hosts.
> >
> > So, of the examples you provided, /123 is unlikely to achieve the intent
> > of BCP204, but /81 or /99, while they don't meet the specific
> > RECOMMENDATIONS of BCP204 there doesn't seem to be any reason they
> > couldn't achieve the fundamental intent of BCP204, granted with without
> > much sparseness or entropy in the assignments, but that's not
> > specifically part of BCP204.
>
> Could you copy&paste the "specific recommendations" you're referring to?
>

Second paragraph, second and third sentences of section 8;

   This can be achieved either by allowing the host
   to form new addresses autonomously (e.g., via SLAAC) or by providing
   the host with a dedicated /64 prefix.  The prefix MAY be provided
   using DHCPv6 PD, SLAAC with per-device VLANs, or any other means.

Furthermore, I would concur that those are the only current standards track
ways to achieve the desired result and they require /64 either per host or
per subnet.

I haven't found any. And I see no reason for which the authors of bcp204
> should have cared about a specific prefix length.
>
> Thanks,
>

Hope that helps!

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