Re: [DNA] [Issue 15] [Issue 16] DAD and MLD Interaction

[Erik Nordmark <erik.nordmark@sun.com>]

James Kempf wrote:

>>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?
>>
> 
> 
> No, but unfortunately the oDAD document doesn't say anything about this.

I suspect the oDAD document has no need to say anything. It isn't until 
one tries to combine oDAD with DNA that the issue of separating the 
optimistic state change and the sending of the NS appears.

> Most implementors of oDAD will probably send it out when the state change to
> Optimistic happens, because the draft says that, but when combined with DNA,
> I suspect there may be some confusion unless we make it clear.

Agreed.

> How about: the node SHOULD avoid sending the NS until after the RS is
> returned?

Or. more generally, until it has determined that it has moved to a new 
link. If an RS is returned which indicates that it didn't move, then 
there is no need to send an RS.

> Note that even if we do change the state to Optimistic, there is still the
> issue I raised about the node originating packets with a topologically
> incorrect source address if it has moved to a new IP link. The only way to
> prevent that from happening is to make the addresses Tentative (and suppress
> the DAD NS until after the RA returns) until the node actually finds out in
> the RA whether it actually has moved to a new IP link or not.

Originating such packets is ok I think. If the host has moved to a new 
link it will not receive any "replies". It might make sense and assume 
that it didn't move in this case until it's discovered that it did move.

   Erik