Re: [DNA] RE: Review of draft-krishnan-dna-simple-01.txt

[JinHyeock Choi <jinchoe@gmail.com>]

Bernard

> > Multiple NSs won't correct the wrong DNA decision from RAs with
> > disjoint prefix lists. An NS/NA based DNA decision is overruled by RA
> > based DNA decision. Upon receiving an RA with no known prefix, a host
> > will assume a link change even if NS/ NA exchange indicates no link
> > change.
>
>  [BA] Why?

From the below, I had assumed that RA based decision always takes precedent.

  > > > 4) When 2 & 3 give conflicting answers, 3's decision is definite.
  > >
  > >  [BA] Correct -- except for DHCPv6 case, where 2) may confirm
  > >  the validity of a previously assigned address, but 3) may indicate
  > >  the need to send a DHCPv6 request.   As before if the DHCPv6
  > >  assigned address conflicts with the address determined in 2),
  > >  then DHCPv6 wins.

However, from your remarks below, it seems that sometimes NS/ NA based
decision overrules RA based decision.

>  If a NUD exchange suceeds, the host should merely assume
>  that the information it got from that particular router is still valid, not
>  that
>  it has confirmed *all* the information from *all* the routers.   So if it
>  assigned a still-valid address based on a particular prefix announcement,
>  it need only confirm reachability to the router that sent that prefix
>  announcement.  Receiving an RA with no known prefix from some other
>  router is immaterial.

ok. However this necessitates hosts to maintain the state of pairs, (a
prefix, a router which advertise the prefix). Also if an RA with no
known prefix arrives before a solicited NA, I assume the host
immediately decides a link change, instead of waiting for the NA.

I have difficulty discerning the above mechanism from the draft.
That's why I first tried to clarify DNA operation lest we should
discuss over irrelevant items.

>  And of course, if that same router updates its
>  prefix list,
>  then the previously cached DNA configuration information is invalidated.

ND allows a router to omits some prefixes when it advertises an RA. So
from a prefix list in an RA, a host has difficulty discerning whether
a missing prefix is invalidated or simply omitted.

>  As an example, if a host previously recieved an RA with no known prefix,
>  and as a result got a valid address assigned via DHCPv6, it should be able
>  to confirm the validity of that address based on a NUD exchange with the
>  router (while doing a DHCPv6 configuration exchange in the background).

This is not clear. With which router a host should perform NUD to
validate a DHCP based address? No router has specific relation with
the DHCP based address. Any router will do? If that's the case, why
can't we use that criterion for non-DHCP based address.

Now I come to wonder why RA based decision is assumed definite. Maybe
it's better to make NS/NA based decision takes precedents over RA
based decision.

Thanks for your kind consideration.

Best Regards

JinHyeock