[DNA-BOF] Using addresses optimistically and optimizing DAD

[Pekka Nikander <pekka.nikander@nomadiclab.com>]

Greg and Youn-Hee,

[Changed the subject to match the topic discussed.]

Greg Daley wrote:
> I'm not sure if we can use the global addres optimistically
> or not (I haven't finished thinking about it).

I wish we could, i.e., I see certain needs for such functionality.
Consequently, I think that we should produce an analysis of the
potentially adverse effects of sending packets, destined to
a global address and therefore a stale router link layer address,
and sourced from a global address.  My current understanding is
that in most cases the link layer drops those packets, and no
real harm is done.  In the improbable but possible case where there
happens to be a node whose link layer address is the same
as the router link layer address from the previous link, that
node will get some traffic not destined to it, and the IP layer
will drop it.

Hence, to me it looks like the only result of using such
addresses is some unnecessary traffic.  If we rate limit
the use of such addresses, I don't see much problem.
But I probably fail to see something.

> I'm pretty sure that we shouldn't do DAD for a global
> address unless the link had changed (and the global address
> wasn't valid). This implies DNA completion (although
> configuring a new address may be applicable as soon as a new
> prefix is received).

I think I agree, but I am not sure (still thinking).

> For the link-local address, I think we can say that we don't
> need to wait to hear what DNA says, since I may want to use an
> Optimized DAD procedure so I have a link-local address for use
> in DNA (for neighbour discovery for example).

Yes.

--Pekka Nikander