Le 7 juil. 09 à 21:56, Dave Thaler a écrit :
-----Original Message-----
From: Rémi Després [mailto:remi.desp...@free.fr]
Sent: Tuesday, July 07, 2009 3:03 AM
To: Christian Huitema
Cc: Brian E Carpenter; Xing Li; 6man; Behave WG; Dave Thaler
Subject: Re: Perils of structured host identifiers (was: Modified
EUI-
64 format)
Christian,
Thanks for this analysis.
Caution is indeed a must before any amendment of a basic document.
As my proposal is, its relationship with cryptographically generated
addresses (and with secure neighbor discovery which uses it) should
however not be a problem.
The proposal is, in short:
Point-1: u and g rules apply ONLY to IPv6 addresses that may be used
on IPv6 links (real or virtual).
Disagree on multiple accounts.
First, as I stated in other threads the "g" rule doesn't apply to
IPv6 addresses. It only applies to IEEE EUI-64's (not Modified
EUI-64's
or interface identifiers).
Second, it's not true that they only apply to addresses used on
IPv6 links.
The u/l bit is reserved for global use as Brian Carpenter also noted.
Well, it gets complex.
Discussing the point offline in Stockholm might be better than by mail.
Point-2: in IIDs, the only escape combination of u and g bits MAY be
used for ALL possible new IID formats (having universal OR local
scopes).
I can't parse the above sentence.
As mentioned in a previous mail, the point started from this sentence
of RFC 4291: "The use of the universal/local bit in the Modified
EUI-64 format identifier is to allow development of future technology
that can take advantage of interface identifiers with universal scope."
I am not sure myself I sparse this sentence as intended by authors;
It seems to restrict development of future technology that will be
concerned with the u bit to a technology where IIDs must have
universal scope.
If it should not be interpreted this way, that's good.
What is important here IMHO is only that u=1 and g=1, the only
combination that remains available, can be used to "develop new
technology" without an a priori limitation to universal scope IIDs.
- Since CGAs are to be used on IPv6 links, they are not concerned
with Point-1.
Disagree, see above.
The point was ambiguous, I have to agree.
Christian apparently also interpreted it as meaning that CGAs must be
used on IPv6 links. Sorry for this.
An hopefully better way to express the point could be:
"Since at least some CGAs have be used on IPv6 links, their format,
being defined in RFC 3972 for all uses, is subject to
u and g rules. Point-1 consequently doesn't concern CGAs: its
purpose is to permit u and g rules to be ignored in formats defined
for addresses that cannot appear on an IPv6 links."
IPv6 addresses of an IPv4-only hosts that are accessed via SIIT are,
unlike CGAs, concerned with Point-1.
I understand however that a majority may prefer to ignore this fact,
and submit also these addresses to u and g rules. (IMHO unfortunate,
but of course possible.)
Regards,
RD
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