Subject: WG ACTION: 2 weeks to discuss [LL70] DNAv4 normative or informative?

From: Erik Guttman <[email-masked]>
Date: Wed, 5 May 2004 01:26:14 +0200

Please post discussion of this issue to the mailing list over the 
next two weeks
ending May 18, 2004.  In order to accept this issued, we will need a strong WG
consensus given that this is very late in the process.

Please see http://www.drizzle.org/~aboba/ZEROCONF/issues.html for a list of
current issues and their status.

[ll70]

Description of Issue:		DNAv4 normative or informative?
Submitter Name:                 Stuart Cheshire
Submitter Email Address:        [email-masked]
Date first submitted:           04 May 04
Reference:
Comment Type ['t'ech|'e'dit]:	t
Prio ['S' Must|1 should|2 may]:	S
Section:			References
Rationale/Explanation:
Lengthy Description:

[Stuart]

>[DNAv4]   Aboba, B., "Detection of Network Attachment (DNA) in IPv4",
>           draft-ietf-dhc-dna-ipv4-06.txt, Internet draft (work in
>           progress), March 2004.

Is this normative or informative?

If ICMP is normative, this should be too.

Or neither should be.

[Erik]

Why do you say that?  The only places we mention DNAv4 is in connection
with DHCPv4.  If the IESG is happy with the informative reference
categorization, so am I.  Adding this to the Normative reference section
would delay publication of IPv4LL till DNAv4 is done.  I do not believe
DNAv4 will complete within a year.

[Stuart]

I disagee.

    For these
    reasons, a host SHOULD NOT have both a valid routable address and an
    IPv4 Link-Local address configured on the same interface.

    A "valid routable address" is a routable address that passes the
    reachability test described in section 2 of "Detection of Network
    Attachment (DNA) in IPv4" [DNAv4].

To implement this "SHOULD NOT" requirement, an implementation has to also
implement [DNAv4] to determine what's a "valid routable address".

Hence, normative reference (or the "SHOULD NOT" prohibition could be
removed or refined to not depend on DNAv4).

[Erik]

Hmmm.  Do you realize you want to raise the bar for the publishing
of this document beyond what the IESG has called for.  This change
of category may well result in tens of months delay of publication of this RFC.

Can we change the 'is' verb in the second cited sentence to one
that reads 'may be determined' and add some text from DNAv4 with
an informative reference 'for further information'?  That is the
way specific citations to 'upcoming work' are usually handled in
order to avoid creating document dependencies.

Requested Change:

Move DNAv4 from informative to normative.

---

From: Ralph Droms <[email-masked]>
Date: Tue, 04 May 2004 22:44:49 -0400

Well, I notice there's a difference in usage between
draft-ietf-dhc-dna-ipv4-07.txt and draft-ietf-zeroconf-ipv4-linklocal-14.txt:

draft-ietf-dhc-dna-ipv4-07.txt:

2.2.  Reachability Test

    If the host has a valid routable IPv4 address on the "most likely"
    point of attachment, the host will typically perform a reachability
    test, as described in this section.  The purpose of the reachability
    test is to confirm whether the host is connected to a network on
    which it has a valid routable IPv4 address.

draft-ietf-zeroconf-ipv4-linklocal-14.txt:

1.9.  When to configure a Link-Local IPv4 address

    [...]

I read a subtle difference in meaning between these two text snippets: in
draft-ietf-dhc-dna-ipv4-07.txt, a valid routable address need not pass the
reachability test, while in draft-ietf-zeroconf-ipv4-linklocal-14.txt, a
routable address becomes a valid routable address once it has passed the
reachability test.  And, it's not clear draft-ietf-dhc-dna-ipv4-07.txt is
consistent in its use of the phrase "valid routable address".

Now, back to the real problem.  Unfortunately, it appears
draft-ietf-dhc-dna-ipv4-07.txt truly is a normative reference in
draft-ietf-zeroconf-ipv4-linklocal-14.txt as the text currently stands.  An
implementor has to read and understand draft-ietf-dhc-dna-ipv4-07.txt to
implement draft-ietf-zeroconf-ipv4-linklocal-14.txt.

We could try to finesse the problem as Erik suggests, by changing the
reference to the reachability test in draft-ietf-dhc-dna-ipv4-07.txt to be
advisory rather than mandatory.

Another way around the problem would be to copy the text about reachability
testing into draft-ietf-zeroconf-ipv4-linklocal-14.txt.  Seems like a lot of
text to insert that would cause yet another delay, but I don't have a better
suggestion.

I don't think removing the restriction against selecting a link-local
address when a usable routable address is available shold be removed.

- Ralph

At 01:26 AM 5/5/2004 +0200, Erik Guttman wrote:
>Please post discussion of this issue to the mailing list over the next two 
>weeks

---

From: Robert Elz <[email-masked]>
Date: Wed, 05 May 2004 08:11:30 +0700

Date:        Wed, 5 May 2004 01:26:14 +0200
    From:        Erik Guttman <[email-masked]>
    Message-ID:  <a05200f07bcbdce62e305@[80.139.178.51]>

[Stuart]

  | To implement this "SHOULD NOT" requirement, an implementation has to also
  | implement [DNAv4] to determine what's a "valid routable address".
  | 
  | Hence, normative reference (or the "SHOULD NOT" prohibition could be
  | removed or refined to not depend on DNAv4).

I agree with that, it is clearly a normative reference as the text
currently stands.

  | [Erik]
  | 
  | Hmmm.  Do you realize you want to raise the bar for the publishing
  | of this document beyond what the IESG has called for.

Yes, we could cheat, but then if the DNA doc never appears, the LL spec
will be useless.

The best way to fix this is to rewrite the reference so that it is
no longer normative -- the easy way to do that would be to simply
copy the text from the DNA draft that describes what is a valid routable
address, and include it in this doc (and then add an informative
reference to note the source of the text).

Do that we get exactly the meaning the doc currently has, no indefinite
delay waiting for another WG's doc to appear, and no cheating of the
process (with everyone just looking the other way) either.

[Aside: even if the IESG allow this through, because of negligence or
collusion, the RFC editor may spot it, and hold up publication anyway,
so it needs to be fixed, one way or another].

kre

---

From: "Philip Nye" <[email-masked]>
Date: Fri, 7 May 2004 12:53:18 -0000

I agree that as it stands the reference is normative.

We could get around this by making the definition more vague:

Change:

to:
   "valid routable address": The determination of whether a routable
   address is valid will vary with the network infrastructure and
   system context. A useful guide is provided by the reachability
   test described in section 2 of "Detection of Network
   Attachment (DNA) in IPv4" [DNAv4] which is performed by attempting
   to verify reachability of the default gateway(s).

Philip