Re: New Version Notification for draft-chakrabarti-nordmark-6man-efficient-nd-05.txt

神明達哉 <> Mon, 03 March 2014 17:58 UTC

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Date: Mon, 03 Mar 2014 17:57:55 +0000
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Subject: Re: New Version Notification for draft-chakrabarti-nordmark-6man-efficient-nd-05.txt
From: 神明達哉 <>
To: Erik Nordmark <>
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At Mon, 03 Mar 2014 15:01:55 +0000,
Erik Nordmark <> wrote:

> >> To have a unicast RA prior to having registered the link-local address,
> >> the router needs to use the SLLA option in the RS - this would be the
> >> same mechanism as in the draft for sending errors to NS/AROs.
> > What if the link-local address is a duplicate and that's because the
> > link-layer address is a duplicate?  If the unicast RA is supposed to
> > include an ARO whose status field is 1 and be sent to the (duplicate)
> > link-local address, it's not guaranteed the RA is delivered to the
> > node that sent the RS.
> We can not detect and handle duplicate MAC addresses using DAD in general.
> Even back when we first defined DAD we knew it could handle MAC address
> duplicates for Ethernet (assuming certain device driver behavior), but
> probably not on FDDI and Token Ring (due to how the ring maintenance
> worked).
> More recent work like dad-proxy assumes that the MAC addresses  are not
> duplicate, and the loopback case needs special care even when MAC
> addresses are unique.
> Using explicit registrations doesn't really change that. The
> registration needs some unique id (be it an EUI-64 or DCHP DUID) that is
> unique to tell apart a duplicate and a registration refresh. If your MAC
> address is not unique then your EUI-64 (or MAC address based DUID) is
> likely to also not be unique.

I'm not sure if I follow your logic.  Probably as you noted above
yourself, the original DAD took into account handling MAC address
duplicates, even if it may not always work.  On the other hand,
efficient-nd can never handle MAC address duplicates.  Since
efficient-nd seems to cover more general (even if not all) networks,
claiming it eliminates the need for multicast in specific cases
including DAD, I think it's important to clarify what it trades for it
(which is, in this case, the inability of handling MAC duplicates).

JINMEI, Tatuya