Re: Why has RFC 4941 been designed in such a way, that it might cause address conflicts?

[james woodyatt <[e-mail]>]

On Mar 15, 2011, at 12:11 , Markus Hanauska wrote:
> 
> [...] but making a tiny change to existing RFCs to make it impossible will always be better IMHO

Let me try again... there is no "tiny change" to existing RFCs that can make it *impossible* for address conflicts to arise.  The best we can do is to reduce the probability of address conflicts from arising inadvertently under normal usage scenarios.

You seem to think that by reserving certain IID patterns for use with different address configuration schemes, we could have more than *optimism* that DAD will succeed, c.f. RFC 4429, that we could be *certain*.  No such determinism is possible.  EUI-48 and EUI-64 addresses with global uniqueness flags are not always globally unique because factories make errors.  Cryptographic and privacy addresses can collide in rare circumstances.  Most importantly, because it's the most frequent cause of error, manual configuration procedures are-- sing it with me-- prone to manual error, including but not limited to humans inappropriately loading addresses that conflict with otherwise automatically configured addresses on the network.

No certainty is possible.  Duplicate Address Detection (DAD) is your last best hope for civilization.


--
james woodyatt <[e-mail]>
member of technical staff, core os networking