Subject: RE: [rfc2461bis] Receiving a prefix option with prefix length > 64

From: "Soliman Hesham" <[email-masked]>
Date: Fri, 18 Jun 2004 02:58:44 -0400

> I admit this can be a discussion on an atypical scenario, and I see
 > your frustration.  However, even if this is related to something
 > atypical, I believe it's very helpful to clarify the points in
 > rfc2461bis, since issues regarding prefix lengths have been annoyed
 > readers several times.

=> Ok, I think it can be clarified in relation to the setting of the flags
and the 
prefix length. Even this is a bit shaky but I think I agree with you about
the confusion with things the way they are. 

 > 
 > If you do not have enough time to spend on this, I'm willing to be a
 > volunteer to provide text clarifying the points.  Of course, we need
 > to make a consensus on details before editing the text.

=> It's ok I'll save you the trouble and do the initial proposal, feel free
to
add to it. Thanks for the summary. 

Hesham

 > 
 > Just trying to summarize the points so far,
 > 
 > 1. RFC2461 originally separated prefixes for on-link determination
 >    from prefixes for address configuration clearly.  This is a fact.
 > 
 >    1-1. in my interpretation, the RFC intended arbitrary lengths for
 >    prefixes for on-link determination, though the lengths may be
 >    invalid for prefixes for address configuration.
 > 
 > 2. the IAB made recommended to add a restriction of the length of
 >    prefixes for address configuration for a certain set of prefixes.
 >    This is another fact.
 > 
 >    From 
 > http://www.iab.org/appeals/kre-ipng-address-arch-draft-standa
rd-response.html:

     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
   
3. what I'd like to clarify in rfc2461bis are:

   A. whether we'll still separate prefixes for on-link determination
      from prefix for address configuration, or we'll tie the former
      with the latter more tightly than before.
   B. if we still separate the two types of prefixes, whether there
      should be restriction on the length of a prefix for on-link
      determination.  If yes, what kind of restriction?  Is this
      related to the above recommendation from the IAB?
   C. if we decide to tie on-link prefixes with address-config prefixes
      more tightly, there should be some restriction on the length of
      the prefixes.  Then, what kind of restriction should we take?

I personally prefer "keep separating" for question A, and I prefer
allowing any lengths (between 0 and 128) for the length of an
"on-link" prefix.  The relationship between this and the IAB's
recommendation needs to be discussed.

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

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