Re: 6MAN WG Last Call:draft-ietf-6man-ipv6-subnet-model-00.txt

Erik Nordmark <> Mon, 14 July 2008 10:23 UTC

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Date: Mon, 14 Jul 2008 03:21:15 -0700
From: Erik Nordmark <>
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To: Thomas Narten <>
Subject: Re: 6MAN WG Last Call:draft-ietf-6man-ipv6-subnet-model-00.txt
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Thomas Narten wrote:

> It is clear to me that bullet four in RFC 4861:
>>    on-link     - an address that is assigned to an interface on a
>>                  specified link.  A node considers an address to be on-
>>                  link if:
>>                     - it is covered by one of the link's prefixes (e.g.,
>>                       as indicated by the on-link flag in the Prefix
>>                       Information option), or
>>                     - a neighboring router specifies the address as the
>>                       target of a Redirect message, or
>>                     - a Neighbor Advertisement message is received for
>>                       the (target) address, or
>>                     - any Neighbor Discovery message is received from
>>                       the address.
> Is wrong and needs tweaking. We should fix that on the next update of
> the ND spec. :-)

I agree that bullet four doesn't seem useful.
But I think the same thing applies to the third bullet above; I know of 
no case where it is necessary or useful, and I think it is a potential 
security issue if implemented on multi-interfaced nodes, since the 
receipt of an NA on interface B could conflict with the fact that the 
while prefix is on-link on interface A.

Popping up a level, we set out to clarify the subnet model in this 
draft. Until recently I considered David's on-link issues to be separate 
from the subnet model. But after catching up on this whole thread it 
seems the two issues are closely related.

Hence my question for the WG. Should we expand the scope of 
draft-ietf-6man-ipv6-subnet-model to also clarify/change the on-link 
handling in RFC 4861?


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