Keith Moore writes:
This was shortsighted, just like having the notion of "class" built into
IPv4 addresses was shortsighted.
Just about everything about address allocation has always been
shortsighted.
I have a simple idea: Why not just define the first three /32 chunks of
the IPv6 address space as three IPv4 spaces, and leave the rest of the
IPv6 reserved? This triples the amount of address space available to 12
billion addresses. You put all the existing addresses in the first
chunk, and then expand to the second and third chunks as required once
IPv6 is widespread. You leave all the rest ALONE until these chunks are
exhausted. Simple, no? And it involves no stupid decisions that will
cause the entire address space to be exhausted in twenty years. It buys
you possibly decades of time in which to think of a new and better way
to allocate a bit more address space. You proceed by small increments
like this for the future, never attempting to allocate the entire space
at once. And if you do it that way, there's a good chance that you'll
never run out of space, and rewriting will be minimal or nonexistent.
Fortunately the mistake is easily rectified, so long
as software doesn't get into the habit of expecting the lower 64 bits
of an address to be a unique interface identifier.
Why dedicated /64 to anything? We are getting by just fine on /32 for
the whole world right now. Why is a sudden expansion of 2^32 required
RIGHT NOW?
See, that's the classic mistake: Everyone wants to divide the entire
address space RIGHT NOW, without any clue as to how the world will
evolve in years to come. Nature may abhor a vacuum, but it certainly
also seems that engineers abhor unallocated address space, and will try
to allocate everything even when they are lightyears off the mark, and
even if it means rewriting all the software in the world a few decades
later.