[address-policy-wg] Re: IPv6 addresses really are scarce after all

--On Saturday, 25 August, 2007 12:28 -0400 Keith Moore
<moore at cs.utk.edu> wrote:

> /64 is too small for a home network.  It might indeed turn out
> that it's possible to bridge several different kinds of media
> on a single subnet, but it's bad planning to assume that this
> will be the case and overly constrain home users.  In
> addition, part of the popularity of NAT has resulted from its
> allowing a consumer to simply "plug in" a new network to an
> existing network.  But the popularity of NAT in IPv4 has also
> greatly limited the ability of the IPv4 network to support new
> applications, and increased the expense required to support
> others.  A lot of the value add in IPv6 results from its
> having enough address bits that NAT is no longer necessary.
> But if we constrain home users to the point that they see a
> benefit from NATting, we will have destroyed much of the
> additional value of IPv6.

Keith,

Will all due respect, even if you assume a "home" with ten
occupants, a few hundred subnets based on functions, and enough
sensor-type devices to estimate several thousand of them per
occupant and a few thousand more per room, 2**64 is still a
_lot_ of addresses.   Now that number goes down significantly
--and I would agree with your assertion-- if we were still
assuming the use of hardware-assigned MAC addresses to populate
that space.  But we largely are not.

The use of NAT to expand address space in residential use of
IPv4 has been largely to expand one or two addresses into around
2**16.  Even those of us who run several subnets with different
security policies don't often use that much space up.  While we
clearly could in the future, and I don't like NATs much more
than you do, a /64 gives 48 bits of headroom -- over a dozen
decimal orders of magnitude if my mental arithmetic is correct
-- above any regularly-demonstrated current need.   That is a
lot of headroom, enough that the assertions above are not
obviously true, at least without a lot more rationale.

That doesn't mean I'm convinced that shifting the boundary is
either necessary or desirable.  But I don't think hyperbole
helps the discussion.

     john