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

From: JINMEI Tatuya / 神明達哉<[email-masked]>
Date: Wed, 27 Apr 2005 17:21:22 +0900

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-masked]

Subject: Re: IPv6 WG Last Call:draft-ietf-ipv6-2461bis-01.txt
From: JINMEI Tatuya / 神明達哉<[email-masked]>
To: Erik Nordmark <[email-masked]>
Cc: [email-masked], IPv6 WG <[email-masked]>, Pekka Savola <[email-masked]>
Date: Sat, 12 Feb 2005 05:10:42 +0900
List-Id: "IP Version 6 Working Group \(ipv6\)" <ipv6.ietf.org>

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: "Soliman, Hesham" <[email-masked]>
Date: Wed, 27 Apr 2005 11:29:37 -0400

Sure, this is fine with me. Will add it to the next rev.

Hesham

 > -----Original Message-----
 > From: [email-masked] 
 > [mailto:[email-masked]]
 > Sent: Wednesday, April 27, 2005 4:21 AM
 > To: Soliman, Hesham
 > Cc: [email-masked]
 > Subject: Forward: Re: IPv6 WG Last 
 > Call:draft-ietf-ipv6-2461bis-01.txt
 > 
 > 
 > Hello,
 > 

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