Use cases for optimized DAD (was Re: [DNA-BOF] Do we need a separateDAD Problem Statement?)

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

Soohong Daniel Park wrote:

> Optimized DAD procedure;
> 1) optimized DAD for link-local address before DNA
> 2) obtaining link-local address and completing DNA
> 3) obtaining global address informations (prefix...)
> 4) composing global address
> 5) optimized DAD for global address ( or skipping)
> 
> Am I missing something ?

I am thinking about a situation where a moving node can
anticipate, with high probability, the prefix that
it is likely to use on the new link.  For example, you could
say that the prefixes used on a given wide are WLAN network
were

   <common prefix>:hash(base station link layer address)::

If that was the case, the node could optimistically assume
what its prefix is likely to be, and optimistically
configure a global address even before it has sent any
IP packets on the new link.

This more or less falls withing your framework, but with
the twist that 1) and 5) can happen at the same time, i.e.,
before DNA has completed.

Summary:  I would rather not see any unnecessary design
barriers for optimized DAD.  I merely see the two distinct
cases of more or less random addresses (which can use an
optimistic DAD procedure) and stateful addresses (which
can use a procedure based on pre-allocation).

--Pekka Nikander