Subject: [RFC 4861] upper-layer reachability confirmation

From: Yukiyo Akisada <[email-masked]>
Date: Tue, 24 Jun 2008 18:06:17 +0900

Hi, all.

I have a question about upper-layer reachability confirmation defined in RFC 4861.

When the neighbor cache state for the default router is STALE
and the host sends a packet to off-link,
the default router sends redirect packet to the host.

Can the host considers that the default router is REACHABLE?

Personally, I didn't expected this behavior.
But I found that an implementation behaves like this
when I'm developping the conformance tester.

How do you think about this behavior?

Thanks,

-- 
Yukiyo Akisada <[email-masked]>
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From: Sebastien Roy <[email-masked]>
Date: Tue, 24 Jun 2008 10:32:08 -0400

> How do you think about this behavior?

That seems reasonable to me.  The host sent a packet to the router, and
the router responded with one of its own which was received by the host.
This is bi-directional reachability.

In general though, I cringe at the mention of the word "conformance" in
the context of IPv6 neighbor discovery, and your question is an example
of why.  That's probably a separate discussions though, and one which
has already been masticated over numerous times before in the distant
past. :-)

-Seb

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From: Vlad Yasevich <[email-masked]>
Date: Tue, 24 Jun 2008 11:57:57 -0400

> This is bi-directional reachability.

It's reasonable as long as the implementation doing so can correctly identify
that it sent the packet triggering the redirect.  If the implementation
can do so, it can assume bi-directional communication.

Personally, I wouldn't consider this upper layer indication, since Redirect
is not strictly upper layer.

-vlad

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From: Yukiyo Akisada <[email-masked]>
Date: Wed, 25 Jun 2008 14:54:49 +0900

Hi, Sebastien and Vlad.

Thanks for your inputs.

Well, I will get in flexibility of ND.

But having said that,
my concern was also that the Redirect is the same layer in ND,
as Vlad said.

Regards,

On Tue, 24 Jun 2008 11:57:57 -0400