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Re: [DNA] [Issue 15] [Issue 16] DAD and MLD Interaction
James Kempf wrote:
> Draft-pentland in Section 5.2.3 says this:
>
> Hosts MUST include a tentative source link layer address option
> (TSLLAO) in the RS message [13]. The router solicitation message is
> sent to the All_Routers_Multicast address and the source address MUST
> be the link local address of the host.
>
> The router uses the TSLLAO to route back to the host, and the definition of
> the TSLLAO means that it won't pollute the neighbor cache if there's a
> duplicate. So there should be no effect on the router neighbor cache even if
> there is a duplicate, and the router shouldn't send the RS to any other node
> even if there is a duplicate because the TSLLAO will allow link routing to
> work correctly.
This handles the RS not overwriting a previous entry in the routers
neighbor cache, but doesn't prevent other hosts on the link (which send
a NS for instance) from being polluted.
> I considered that, but the problem is that if the addresses are switched to
> "Optimistic" . Section 3.3 of draft-ietf-ipv6-optimistic-dad says this about
> the "Optimistic" state:
>
> * (modifies 5.4) As soon as the initial Neighbor Solicitation is
> sent, the Optimistic Address is configured on the interface and
> available for use immediately. The address MUST be flagged as
> 'Optimistic'.
>
> so what this means to me is that the node would have to send NSes on the
> link prior to switching its addresses to Optimistic, even if it is on the
> same link, because it doesn't find out that it is on the same link until
> after the RA returns. I'm not sure whether the extra traffic overhead on
> each move is really necessary or beneficial.
There is no technical reason for optimistic DAD to require that the NS
be sent before or even after state change AFAIK. Do you see a technical
reason?
AFAIK The state change says "don't pollute" and the NS is there to find
out whether there is a duplicate.
Erik