Subject: [2462bis] IAB recommendation on prefix lengths

From: JINMEI Tatuya / 神明達哉<[email-masked]>
Date: Mon, 12 Jul 2004 21:15:06 +0900

Hello,

I'd like to know opinions on the following IAB recommendation
regarding rfc2462bis (the latter part):

 e) We recommend that, via a recommendation to the IESG, that the IPv6
    Working Group expeditiously revise RFC-2461 to:

    * specifically note that it is not valid to configure an IPv6
      router such that the 'autonomous configuration' bit is set to
      TRUE AND the advertised IPv6 prefix length exceeds 64 bits AND
      the advertised IPv6 prefix does not start with binary 000,

    and also expeditiously revise RFC-2462 to:

    * specifically require that a host ignore a Prefix Advertisement
      Option when the first three bits of the advertised IPv6 prefix
      do not start with binary 000 AND the advertised IPv6
      prefix-length exceeds 64-bits.

(The entire message including the recommendation is available at:
http://www.iab.org/appeals/kre-ipng-address-arch-draft-standard-response.html)

The latest revision of the rfc2462bis draft does not contain this
particular change.  In particular, it does not contain the hard-coded
constants of binary 000 and 64-bits.

Instead, the draft specifies a prefix (with the A flag being set) must
be ignored if the sum of the advertised prefix length and the length
of the interface identifier is not identical to 128.  This requirement
is actually already included in RFC2452.

The rfc2462bis draft also clarifies that the length of the interface
identifier is defined in link-specific documents which should be
consistent with the IPv6 address architecture.

The above IAB recommendation is therefore a logical consequence from
what are described in the draft because the IPv6 address architecture
specifies the interface ID length is 64 for addresses beginning with
binary 000.

We could still add the specific recommendation to rfc2462bis.
However, I personally hesitate to do that since I basically prefer
not hard-coding particular constants in general rules as long as the
specification is clear (and, in fact, I believe the specification is
already pretty clear on this point).

What do others think?  Any opinions or suggestions will be highly
appreciated.

					JINMEI, Tatuya
					Communication Platform Lab.
					Corporate R&D Center, Toshiba Corp.
					[email-masked]

--------------------------------------------------------------------
IETF IPv6 working group mailing list
[email-masked]
Administrative Requests: https://www1.ietf.org/mailman/listinfo/ipv6
--------------------------------------------------------------------

---

From: "James Kempf" <[email-masked]>
Date: Mon, 12 Jul 2004 09:37:38 -0700

Why not send this email message to the IAB and ask?

            jak

---

From: JINMEI Tatuya / 神明達哉<[email-masked]>
Date: Tue, 13 Jul 2004 16:20:02 +0900 (JST)

>>>>> On Mon, 12 Jul 2004 09:37:38 -0700, 
>>>>> "James Kempf" <[email-masked]> said:

> Why not send this email message to the IAB and ask?

OK, will do (with ccing to this list).

					JINMEI, Tatuya

---

From: JINMEI Tatuya / 神明達哉<[email-masked]>
Date: Tue, 13 Jul 2004 16:21:01 +0900

JINMEI, Tatuya

---

From: JINMEI Tatuya / 神明達哉<[email-masked]>
Date: Tue, 13 Jul 2004 18:50:55 +0900

Dear IAB members,

I'm currently working on revising RFC2462 (IPv6 Stateless Address
Autoconfiguration), and am wondering how to deal with the IAB
recommendation described in Section 2.3 of the following message:
http://www.iab.org/appeals/kre-ipng-address-arch-draft-standard-response.html

The current version of the revised draft
(draft-ietf-ipv6-rfc2462bis-02.txt) does not contain the specific
recommended change, but I personally think the current draft is
already pretty clear to reflect the sense of the recommendation (see
the attached message below for more details).

It would be nice if someone in the IAB could tell me whether the
current version is enough or we still need to add the explicit change.

Thanks,

					JINMEI, Tatuya

Subject: [2462bis] IAB recommendation on prefix lengths
From: JINMEI Tatuya / 神明達哉<[email-masked]>
To: [email-masked]
Date: Mon, 12 Jul 2004 21:15:06 +0900
List-Id: "IP Version 6 Working Group \(ipv6\)" <ipv6.ietf.org>

Hello,

					JINMEI, Tatuya

---

From: Erik Nordmark <[email-masked]>
Date: Wed, 28 Jul 2004 06:15:51 -0700 (PDT)

> What do others think?  Any opinions or suggestions will be highly

I think what you have in 2462bis is the best approach; I agree with
you that hard-coding the 000 prefix and /64 in 2462bis would be worse
since it would add complexity to implementations and probably make it
harder to evolve the IPv6 addressing architecture over time.

  Erik