>>>>> On Thu, 17 Jun 2004 11:25:03 -0400,
>>>>> "Soliman Hesham" <[EMAIL PROTECTED]> said:
> I guess I'm confused by something here. The way you make your point
> makes me think that there are two prefixes being advertised, one for on-link
> determination and one for address configuration.
In theory, yes, two prefixes being advertised in a single
prefix-information option if both the A and L flags are set. In fact,
RFC2461 says in 6.3.4 as follows:
Note: Implementations can choose to process the on-link aspects of
the prefixes separately from the address autoconfiguration aspects
of the prefixes by, e.g., passing a copy of each valid Router
Advertisement message to both an "on-link" and an "addrconf"
function. Each function can then operate independently on the
prefixes that have the appropriate flag set.
(I think I cited this part before in this thread, but please excuse me
repeating this. I think this part is important to discuss the
original intention of the RFC.)
> I've questioned the
> practicality
> of this before and I think we can say that this is an atypical scenario based
> on
> our knowledge today. Given this, I don't see a big benefit in spending a lot
> of
> text on this scenario, because it's an unusual case and I think a reader
> would
> find this quite confusing.
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.
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.
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-standard-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 PROTECTED]
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