Subject: Re: RFC 2462 DAD optimization

From: JINMEI Tatuya / 神明達哉<[email-masked]>
Date: Sat, 01 Jun 2002 16:40:00 +0900

>>>>> On Fri, 31 May 2002 10:39:18 -0700, 
>>>>> "Richard Draves" <[email-masked]> said:

> I'm curious about the implementation status. I know the Windows
> implementation does not implement the RFC 2462 optimization - it
> performs DAD on every address independently. What about other
> implementations?

KAME (*BSDs) does not implement the optimization either.  That's
intentional - we once implemented the optimization, but then we
changed our mind because doing DAD for every (unicast) address is a
SHOULD in RFC 2462 and we did not have any strong reason not to follow
the SHOULD (at least at that moment).

					JINMEI, Tatuya
					Communication Platform Lab.
					Corporate R&D Center, Toshiba Corp.
					[email-masked]
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From: YOSHIFUJI Hideaki / 吉藤英明 <[email-masked]>
Date: Sat, 01 Jun 2002 17:03:44 +0900

> performs DAD on every address independently. What about other

Linux / USAGI does not support DAD optimization
and I don't think DAD optimization is a good idea.

--yoshfuji

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From: Francis Dupont <[email-masked]>
Date: Sun, 02 Jun 2002 15:56:54 +0200

In your previous mail you wrote:

   I disagree. I think the problem is in the RFC 2462 optimization. The RFC
   2462 optimization also can fail with manually-configured addresses -
   it's not just a problem with RFC 3041 temporary addresses.
   
=> I agree: the RFC 2462 optimization is based on many implicit
assumptions... We have to drop it or to respecify it clearly/cleanly.

=> in my implementation, DAD was done on every address with an user
control to disable it (default was to enable DAD) but the autoconfig
client tool didn't perform DAD (it was considered as a bug).

Regards

[email-masked]

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From: Erik Nordmark <[email-masked]>
Date: Mon, 3 Jun 2002 22:05:46 +0200 (CEST)

> performs DAD on every address independently. What about other

FWIW The Solaris implementation does supress DAD on addresses configured
using the stateless mechanism except the link local address.
It does perform DAD on all manually configured addresses.

My person opinion is that we should fix that implementation and
other implementations that have this behavior.
Forcing implementations to have more than one link-local address
due to RFC 3041 (and potentially lots of them - one for every valid
RFC 3041 address) since quite odd both conceptually and messy to deal
with from an implementation perspective (need to track which is the "real"
link-local address.)

  Erik