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

--On Saturday, 25 August, 2007 13:08 -0400 Keith Moore
<moore at cs.utk.edu> wrote:

> John C Klensin wrote:
>> --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
>...
>> 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. 

> And 2**45 prefixes under 2000:/3 is a _lot_ of prefixes.  But
> the sheer number of addresses in a subnet or prefixes
> available to be assigned doesn't seem to be the limiting
> factor in either address block assignment or subnetting of
> leaf networks.  Every level of delegation seems to eat a
> couple of address bits.  

Yes.  Of course.  Again, I'm not convinced that this is a good
idea, just trying to keep the discussion focused and real.

> What bothers me about a /64 is not the scarcity of addresses,
> but the inability to subnet it.  (and that, IMHO, was a poor
> design choice in IPv6, but I think it's rather late to revisit
> that choice, just like I think it's late to revisit /48.)

This gets to one of the issues I _am_ concerned about.  While I
didn't call it out explicitly in my response to Thomas, I
believe that, if the RIRs start saying "give out /64s unless
someone can prove to your satisfaction that they need a lot of
subnets" to ISPs, we have ample evidence that some, perhaps
many, ISPs serving the residential market will construe "prove
to our satisfaction" as "pay us a lot of extra money".  If that
happens, our experience with IPv4 and NATs suggests to me that
it will be a _very_ short period of time before devices hit the
consumer market that either do subnetting on longer-than-/64
prefixes, are set up to handle some other model of address
pools, or NAT (I'd predict all three and would find the middle
one interesting) along with patches to stacks that support them
as needed.  

Since we probably won't revisit the /64 subnetting choice, those
patches will be made independent of any standard or IETF advice
which suggests that there may be interoperability problems if
there is any opportunity for them.

And _that_ is bad news.  It is also news that reinforces my
response to Thomas: there really are architectural issues in
this sort of decision and no one I know of has chartered the
RIRs to make those types of architectural decisions.

      john