Subject: Re: 2461bis update

From: Sebastien Roy <[email-masked]>
Date: Wed, 01 Jun 2005 11:48:55 -0400

On Tue, 2005-05-24 at 10:04, Soliman, Hesham wrote:
> I think this draft is now ready for the IESG. 

I have one issue with APPENDIX A.  The direct mention of the on-link
assumption was removed from the appendix (from the second bullet item
1), but it is still implied by the text that remains.  The text is:

     1) If no Router Advertisement is received on any interfaces, a
        multihomed host will have no way of knowing which interface to
        send packets out on, even for on-link destinations.
        One possible approach for a multihomed node would be to attempt
        to perform address resolution on all interfaces, a step
        involving significant complexity.

Why would a multihomed host ever attempt to perform any address
resolution on any interface unless it assumed that the destination was
on-link on one of those interfaces?  It should not make this assumption
at all.  While the text is accurate in stating that this involves
significant complexity, it should not suggest that doing on-link address
resolution for a node to which it has no route is a "possible
approach".  If you're multihomed and you have no route to a destination,
then send back an ICMP destination unreachable.  It should be as simple
as that.

If the destination is a link-local address, then that's a different
matter entirely.  In that case, it's a matter of scope ambiguity.  The
text may have been addressing this particular case, but it's not clear
to me.

-Seb

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From: Tim Hartrick <[email-masked]>
Date: 01 Jun 2005 11:37:18 -0700

On Wed, 2005-06-01 at 11:29, Soliman, Hesham wrote:
>  > It would be better than what's there now, but ideally, the 
>  > text should
>  > just be removed entirely.  
> 
>    Doing address resolution on multiple links
>  > can lead to ambiguous results.  There could be multiple destinations
>  > responding to the same address, and you don't know which one you're
>  > talking to.  This hasn't been studied enough to even be 
>  > mentioned. 
> 
> => Agreed. That's why it's in an appendix. Anyway, if no one has a problem
> with removing this text I'm fine with removing it. 
> 

I agree that it should be removed.  It seems completely out of place
given that the on-link assumption has been removed from the
specification.

tim