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RE: [DNA] DNA meeting at IETF71



Comments below.

> When updating the draft, kindly describe DNA procedure, especially the
> link identification mechanism, more thoroughly. From the previous
> discussion with Bernard, I got the impression that there are a few
> things in the current draft which no longer holds such as
>
> o All routers on the link advertise the same subnet prefixes.
>
> Also Bernard informed that 'NS/NA exchange with a router confirms only
> the information from that router and does not guarantee the validity
> of information from other routers'. I assume this is also missing in
> the draft.

I agree that the document needs to more clearly describe the simple
DNA mechanism. 

> I think there should be a way to indicate a DNA link.

One question for simple DNA is whether we are attempting to determine
a "link" or just connectivity to a particular router interface.  This is a subtle,
but potentially important difference.  My impression had been that the goal
was the latter.

> In a DNA link, a host should be informed that simple DNA is supported
> in the link.

If the goal is only to determine whether a given router interface is reachable,
then I don't think this is needed. 

> Otherwise the host has no way to determine whether to use
> simple DNA or ordinary ND.

Given that NUD uses unicast packets, would there be situations in
which "simple DNA" is not supported on a link, but "ordinary ND" is?

One of the design principles of "simple DNA" is that it is never slower than
normal IPv6 address acquisition process (e.g. RS./RA + DHCPv6 if necessary).
If that is true, then should not be a need to make this determination.  Simple
DNA is attempted, and if it fails, it fails. 

> The simplest way may be `when advertising
> an RA, a simple DNA router should indicate that the RA is from a
> simple DNA router with, for example, a DNA bit'

If we start with the assumption that simple DNA should work with existing
routers, then modifications like this are precluded.