at the interim meeting, there was a discussion on DAD (whether
it is mandatory for all address, or we can do it just for link-local
and omit for globals that share the same interface id).
the original text is in the second bullet. i believe it is a bit
confusing at best. the first sentence recommends (SHOULD)
running DAD on every address you have, and then the following sentences
say that you MAY omit it in certain conditions. my suggestion is to
keep the first sentence and remove the exception sentences.
it still leaves me a bit fuzzy feeling as DAD works only if everyone
does it - so MUST sounds necessary to me for DAD to be useful.
DAD does not always work anyways, due to network partition or ethernet
chip initialization delays. so i'm okay with SHOULD on the first line.
in was mentioned that TAHI test files "FAILED" if people omits DAD.
first of all I would like to comment that we cannot take test result
in binary form - when we see "FAILED", we need to diagnose result
carefully. it may be an implementation choice, it may be TAHI's
interpretation, whatever. when TAHI guys run their test on KAME stack,
they give detailed interpretation on why they marked some test "FAIL"
(if they have enough time). i guess the result "FAILED" for the DAD
test is based on the following interpretation on "SHOULD" the first
sentence.
RFC2119
>3. SHOULD This word, or the adjective "RECOMMENDED", mean that there
> may exist valid reasons in particular circumstances to ignore a
> particular item, but the full implications must be understood and
> carefully weighed before choosing a different course.
itojun
5.4. Duplicate Address Detection
Duplicate Address Detection is performed on unicast addresses prior
to assigning them to an interface whose DupAddrDetectTransmits
variable is greater than zero. Duplicate Address Detection MUST take
place on all unicast addresses, regardless of whether they are
obtained through stateful, stateless or manual configuration, with
the exception of the following cases:
- Duplicate Address Detection MUST NOT be performed on anycast
addresses.
- Each individual unicast address SHOULD be tested for uniqueness.
However, when stateless address autoconfiguration is used,
address uniqueness is determined solely by the interface
identifier, assuming that subnet prefixes are assigned correctly
(i.e., if all of an interface's addresses are generated from the
same identifier, either all addresses or none of them will be
duplicates). Thus, for a set of addresses formed from the same
interface identifier, it is sufficient to check that the link-
local address generated from the identifier is unique on the
link. In such cases, the link-local address MUST be tested for
uniqueness, and if no duplicate address is detected, an
implementation MAY choose to skip Duplicate Address Detection
for additional addresses derived from the same interface
identifier.
(snip)
--------------------------------------------------------------------
IETF IPng Working Group Mailing List
IPng Home Page: http://playground.sun.com/ipng
FTP archive: ftp://playground.sun.com/pub/ipng
Direct all administrative requests to [EMAIL PROTECTED]
--------------------------------------------------------------------
