Why would ARIN specifically provide such a list? ARIN is not responsible
for the unallocated space, and there is more in the world than just ARIN.
There are liability issues with that, not to mention the fact that it is
more an IANA function (if for the sake of argument someone would
I consider this to be more of a minor technical issue. ARIN can certain
provide an authoritative directory for the unallocated portions of its own
allocations. And to answer your why question; because only ARIN has an
authoritative and up-to-date view of exactly which addresses are and are
not allocated. Rob Thomas is doing some fine work but he is just plugging
a gap created by inaction on the part of the RIRs.
I'd like to see RIPE, APNIC and LACNIC also set up authoritative LDAP
directories for unallocated IP space at the largest aggregate level. I'd
also like to see them all dump the quirky and antiquated whois protocol
and move to LDAP as the standard way of querying their directories. The
details of which data goes in which directory and whether or not to use
referral LDAP or mirrored databases is something which I'm not concerned
about. We know a lot about running a distributed directory from experience
with DNS so I'm sure that a distributed LDAP hierarchy for the IP address
space won't raise any major issues. There is a lot of LDAP expertise out
there in the world, lots of books, multiple implementations with years of
production experience and people running LDAP directories on a much larger
scale than we need. There is no question that it would work, we just need
the will to prevail against these problems instead of throwing up our
hands and claiming it's too hard, it's impossible and it's not my problem.