John Levine writes:
FWIW, I also don't think that repurposing 240/4 is a good idea.
As people will be aware, we have a different draft on this issue, so
I'm also going to pipe up here.
(Our draft offers no specific plan for exactly how to use the address
space, arguing that the most important short-term priority is to ensure
that implementations stop rejecting it, rather than to decide on a policy
for how or when it can be allocated. For example, it might turn out that
debogonization appears too daunting a task, in which case there might be
a consensus to make it into official private address space in the future.)
To be useful it would require that every host on the Internet update
its network stack,
Most hosts other than Windows already made this change following the
previous proposal in 2008. So we mostly have to get Windows to make the
Routers are a more complicated question, and we would love people to help
us obtain some concrete data about this.
which would take on the order of a decade, to free up some space that
would likely be depleted in a year or two.
When I presented about this at NANOG 84 and APRICOT recently, I noted
that a lot of people's intuitions about rapid exhaustion of IPv4
resources come from RIR allocations that were done with nominal fees.
But blocks that became available and were sold for market rates seemed
to last longer. We think that, if it does become feasible to allocate
historically-reserved space for public Internet use, market-based
allocations like auction mechanisms (which can potentially also be done
by RIRs) will make people more cautious in their appetite for number
resources, while also preventing the price of those resources from rising
as quickly as it otherwise would.
Someone asked a question about how long we thought it would take for
that depletion to occur, and I passed it on to Lee Howard (on account
of his experience in the IPv4 secondary markets). I think I remember
that his answer was "about seven years" -- I should double-check that
it wasn't six years or eight years. I understood the question I was
passing on to be something like "how long will these resources last,
assuming RIRs allocate them by selling them in a series of auctions or
selling them into existing address space markets as though they were
newly-recovered previously-allocated address space?".
It's basically the same amount of work as getting everything to work
That's challenging to quantify, but in any case it doesn't appear to be
_the same work_ or, necessarily, _work by the same people_. For
example, Windows already supports IPv6 quite well, but doesn't support
unicast 240/4 at all. My Linux laptop supports both well, but my ISP
doesn't give me native IPv6. (I don't know yet whether or not my ISP
would have to make changes to support native 240/4, although I look
forward to finding out!)
I don't want people to work to support 240/4 (and other address ranges
we've proposed unreserving) at the expense of supporting IPv6. I agree
with the consensus that implementers and operators ought to support
IPv6. Still, I haven't seen why one can be expected to substitute for
or compete with the other, unless one envisions a very direct conflict
between improving IPv4 support or services and improving IPv6 support
We also have a new draft (published yesterday) more directly on point
about that issue...