I guess RFC 4861 doesn't go so far as to require that: "Because unicast Neighbor Solicitations are not required to include a Source Link-Layer Address, it is possible that a node sending a solicited Neighbor Advertisement does not have a corresponding link- layer address for its neighbor in its Neighbor Cache. In such situations, a node will first have to use Neighbor Discovery to determine the link-layer address of its neighbor (i.e., send out a multicast Neighbor Solicitation)."
Which gives us three ways to solve this problem: 1) Amend "A host only performs address resolution for IPv6 addresses that are on-link." to say "A host only performs address resolution for IPv6 addresses that are on-link or possibly in response to an NUD message without a link-layer address option with an L2 source address that is unavailable to the ND stack." 2) Require hosts to extract the L2 header of the NS when sending the NA (which goes beyond RFC 4861) when the link-layer address option is not supplied in unicast NS messages. 3) Drop incoming NS's for addresses which are not already deemed to be on-link. The advantage of #1 over #3 is that #1 allows a node to receive traffic from a source that is not deemed on-link by the node whereas #3 discourages such traffic. - Wes -----Original Message----- From: JINMEI Tatuya / 神明達哉 [mailto:jinmei_tat...@isc.org] Sent: Tuesday, May 05, 2009 12:34 PM To: Wes Beebee (wbeebee) Cc: Hemant Singh (shemant); erik.nordm...@sun.com; ipv6@ietf.org Subject: Re: comments on draft-ietf-6man-ipv6-subnet-model-03 At Tue, 5 May 2009 11:16:02 -0400, "Wes Beebee (wbeebee)" <wbee...@cisco.com> wrote: > > > It's of course unicast (note the "to P::X"). BTW I don't understand > > this part: "the L2 link-layer address of Y is available to X when X > > receives the unicast NUD message." Why is this ensured? For > > example, X may have just been rebooted and its neighbor cache may be > > empty. > That's because the address that you need is contained in the NUD > packet itself. ??? Do you mean the responding host extracts the link-layer address from the L2 header and uses it to send the NA? And if so, are you arguing that the responding node in question must behave that way to keep this rule? : A host only performs address resolution for IPv6 addresses that are : on-link. --- JINMEI, Tatuya Internet Systems Consortium, Inc. -------------------------------------------------------------------- IETF IPv6 working group mailing list ipv6@ietf.org Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
