Subject: Re: IPv6 WG Last Call:draft-ietf-ipv6-2461bis-01.txt

From: JINMEI Tatuya / 神明達哉<[email-masked]>
Date: Sat, 12 Feb 2005 05:10:42 +0900

Catching up a possibly minor point of an old thread...

>>>>> On Thu, 13 Jan 2005 10:39:15 -0800 (PST), 
>>>>> Erik Nordmark <[email-masked]> 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-masked]

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From: Radhakrishnan Suryanarayanan <[email-masked]>
Date: Mon, 14 Feb 2005 16:26:08 +0530

Hi Erik,
I agree with Jinmei's rephrasing. Both in RFC 2461 and 2461bis the wordings
were sounding little bit confused.
I would request the changing of 2461bis wording as suggested by Jinmei.

Regards
Radhakrishnan
----- Original Message ----- 
From: <JINMEI Tatuya / $B?@L@C#:H (B <[email-masked]>)>
To: "Erik Nordmark" <[email-masked]>
Cc: <[email-masked]>; "IPv6 WG" <[email-masked]>; "Pekka Savola"
<[email-masked]>
Sent: Saturday, February 12, 2005 1:40 AM
Subject: Re: IPv6 WG Last Call:draft-ietf-ipv6-2461bis-01.txt