Re: [DNA] Re: Reclassification of DNA Protocol and new Simple DNAprotocol

[Bernard Aboba <bernard_aboba@hotmail.com>]

>>      o  As a performance optimization, it must not sacrifice
>>         correctness.  In other words, false positives are not
>>         acceptable.  DNAv6 must not conclude that a host has returned
>>         to a previously visited link where it has an operable IP
>>         address if this is not in fact the case.
>
>Simple DNA will not produce false positives unless two routers on two 
>different links happen to have the same link local address and MAC address. 
>Is this a likely scenario that needs to be addressed?

The combination of same link local address *and* MAC address is unlikely, 
assuming that the MAC address is globally unique.  However, not all link 
layers will have a globally unique MAC address, so that there may be a need 
to restrict applicability to those that do.

>I think Simple DNA works as quick as RFC4861 in the worst case (false 
>negative) scenarios.

>This is why we send the RS and the NSs in parallel as you suggested. This 
>ensures that the simple DNA procedure does not run slower than just using 
>RSs.

Right.

>The heuristic in use for simple dna is to store and use the previous 'n' 
>link configurations. Thus it satisfies (a). It we use a sufficiently large 
>value of 'n' we can ensure that (b) is met. We recommend n to be 2 but if 
>you think that the number is too low we can increase it.

A previous link configuration should only be tried if it is still 
corresponds to a valid address.  Otherwise, confirming presence of the 
corresponding router could result in installation of a configuration which 
is no longer valid, which would create a false positive. In practice this 
will restrict the DNAv6 traffic substantially so I'm not clear that it is 
necessary to recommend a value of "n".