Hello,
I've noticed that the latter of Section 7.2.5 of 2461bis was improved
very much in the 02 version:
=======================================================================
If the target's Neighbor Cache entry is in any state other than
INCOMPLETE when the advertisement is received, the following actions
take place:
I. If the Override flag is clear and the supplied link-layer address
differs from that in the cache, then one of two actions takes
place:
a. If the state of the entry is REACHABLE, set it to STALE, but
do not update the entry in any other way.
b. Otherwise, the received advertisement should be ignored and MUST
NOT update the cache.
II. If the Override flag is set, or, both the Override flag is clear
and the supplied link-layer address is the same as that in the
cache, or no Target Link-layer address option was supplied,
the received advertisement MUST update the Neighbor Cache entry as
follows:
[...]
=======================================================================
I'm basically happy with this, but it does not seem to catch the
original point Pekka raised (see the attached message below).
Based on that point, we could simplify item II further as follows:
II. If the Override flag is set, or the supplied link-layer address
is the same as that in the cache, or no Target Link-layer address
option was supplied, the received advertisement MUST update the
Neighbor Cache entry as follows:
[...]
JINMEI, Tatuya
Communication Platform Lab.
Corporate R&D Center, Toshiba Corp.
[EMAIL PROTECTED]
--- Begin Message ---
Catching up a possibly minor point of an old thread...
>>>>> On Thu, 13 Jan 2005 10:39:15 -0800 (PST),
>>>>> Erik Nordmark <[EMAIL PROTECTED]> said:
>> ==> AFAICS, you can remove 'both the Override flag is clear and' here,
>> because the same result happens if the Override flag is set.
> No. The "but do not update the entry in any other way" does not apply when the
> O flag is set, since in that case the recorded link layer address is updated.
I'm not sure if this really rejects Pekka's point. In fact, it seems
to me Pekka is correct here. To make it sure, I've cited the related
part from the draft:
If the Override flag is clear and the
supplied link-layer address differs from that in the cache, then one
of two actions takes place: if the state of the entry is REACHABLE,
set it to STALE, but do not update the entry in any other way;
otherwise, the received advertisement should be ignored and MUST NOT
update the cache. If the Override flag is set, both the Override
flag is clear and the supplied link-layer address is the same as that
in the cache, or no Target Link-layer address option was supplied,
the received advertisement MUST update the Neighbor Cache entry as
follows:
(Section 7.2.5 of draft-ietf-ipv6-2461bis-01.txt)
This awfully complicated block would be clarified as follows (BTW,
regardless of the result of this small discussion, it would be nice if
we could make this part more understandable in the 2461bis work):
1. If the Override flag is clear and the supplied link-layer address
differs from that in the cache, then:
- if the state of the entry is REACHABLE, set it to STALE, but
do not update the entry in any other way;
- otherwise, the received advertisement should be ignored and
MUST NOT update the cache.
2. (else) If
- the Override flag is set,
- both the Override flag is clear and the supplied link-layer
address is the same as that in the cache, or
- no Target Link-layer address option was supplied,
then
the received advertisement MUST update the Neighbor Cache entry
as follows:
[snip]
Pekka talked about the second bullet of case 2, whereas you referred
to (a part of) the 1st bullet of case 1. And, in my understanding,
cases 1 and 2 are mutually exclusive.
JINMEI, Tatuya
Communication Platform Lab.
Corporate R&D Center, Toshiba Corp.
[EMAIL PROTECTED]
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