Date: Mon, 29 Jul 2002 07:25:53 +0300 (EEST)
From: Pekka Savola <[EMAIL PROTECTED]>
Message-ID: <[EMAIL PROTECTED]>
| On Mon, 29 Jul 2002 [EMAIL PROTECTED] wrote:
| > >Wouldn't it be much much simpler just to do DIID? I see zero reason for
| > >e.g. PRFX1::1/64 and PRFX2::1/64 being assigned on two different nodes in
| > >a same subnet.
| >
| > i see zero reason for prohibiting the above configuration.
Nor do I.
| But you agree that the above configuration is very rare, really just a
| "corner case". Someone _might_ want it though.
I don't agree with the first sentence there, I think I'm (a) someone...
| Perhaps this behaviour should be configurable then?
That makes no sense.
| If enabled (default), perform DIID only [and possibly skip for EUI64
| addresses]. This is useful in scenarios where there is a large number of
| addresses assigned in the nodes.
|
| If disabled, perform DAD for every address without any optimizations.
The problem is that you have to know what is enabled/disabled on every other
node on the link as well. So, this would need to be yet another RA
parameter (and there'd have to be some rule on what was permitted when
there is no router in that case).
It really is simpler just to always do DAD.
On optimistic DAD - maybe I misunderstood what Erik was suggesting, but
I assumed the "optimistic" wouldn't be "irrational" .. that is, for
optimistic DAD, which I think I'd certainly not object to (though I'm also
not sure the actual cost of full DAD is enough for it to matter) I'd
assumed the idea would be to send the first DAD NS, and wait for a reply,
and if no reply came to that one, assume the address is OK, while
simultaneously going on and doing the rest of the DAD procedure (killing
the address if it fails). That more or less cuts the DAD delay by 2/3 (but
it doesn't eliminate it).
This relies upon NS/NA failure being very rare (so it might be something that
you'd do on fairly reliable links, and not on ones known to have greater
packet losses). That is, if there is another (operational) user of the
address, they're almost always going to reply to the first NS for their
address (whether or not it is for DAD purposes). That is certainly in
line with my experiences with ARP.
kre
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