Re: [DNA-BOF] BoF Last Call on DNA WG Charter.

[JinHyeock Choi <athene@sait.samsung.co.kr>]

Hi Alper

Alper Yegin wrote: 
> > The same problem occurs with IPv4 Link-Local addresses.  Since the
> > probability of conflict is relatively high, we had to recommend that a
> > host awakening from sleep, attaching, etc. had to do DADv4 again.
> > 
> > The chance of conflict is much lower in the case of IPv6, so I'd ask
> > whether we think that the same approach is still necessary.  It's quite
> > costly, of course, so if it can be avoided that is a good thing.
> 
> This is a hard question. The probability of collision (p1) is somewhat not
> low enough, hence the RFC 2462 requires use of DAD. Now we are talking about
> the possibility of an address collision sometime after the address was
> checked out to be unique (p2). This is even a lower probabibility, yet how
> do we determine it is low enough to be negligible? Also, note that the p2 is
> a function of the number of new IP addresses configured while the host was
> not defending its IP address. This is higher in a network where the number
> of hosts joining the network (i.e., mobility) is high.

It also is a function of the time during which the host is absent. It will be 
difficult to set a criterion for 'to DAD or not to DAD'. :-) 

The possible solution may be not to set the criterion but to simply use 
'Optimistic DAD' after reattachment. 

Best regards

JinHyeock