Re: [DNA] DNA Goals Issue List

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

> I am not sure you need to detect the identity of currently attached link for
> quick configuration either. For example, considering the CPL as the link
> identity, you don't  need to detect the identity of currently attached link
> (the COMPLETE prefix list) to ascertain the validity of the existing IP
> configuration or to quickly re-configure  yourself. You only need one prefix
> - right? So, making "detecting the identity of  the currently attached link"
> part of the goal is kinda misleading.

If the host is on the same link as before, it needs at least on prefix which
was part of the known set of prefixes for the link.
(Note that due to packet loss of RAs a host might not know all the
prefixes on the attached link.)

If the host has moved to a different different link, it needs to see
enough RAs and prefixes to have a pretty good probability that the
prefix sets is disjoint.
If it knows the complete prefix list from the old link with high probability,
then one RA might be sufficient.

There is a very unlikely case where this isn't sufficient, which is when the
host moves between APs (i.e. receives a 'link up' indication from the device
driver) and *at the same time* a new router is added on the link and a new
prefix is added, and the new router only announced the new prefix, and the RA
from this new router arrives at the host first after the host has sent the RS.
In that case, from the single RA with the single prefix, it will look
like a different link because the prefix sets are disjoint.
But this is very unlikely.

  Erik