[arin-ppml] Use of "reserved" address space.

Eliot Lear lear at cisco.com
Mon Jun 28 04:18:55 EDT 2010

 Hi James,

Thanks for your note and that of others on this topic.

As merely a member of the IETF community, I'm representing a broader set
of views than my own, and I may be doing a poor job of it.  Please ask
others if you like on the int-area mailing list that can be found via

On 6/27/10 8:58 PM, James Hess wrote:
> On Sun, Jun 27, 2010 at 6:10 AM, Eliot Lear <lear at cisco.com> wrote:
> [snip]
>> It would take forever to fix printers, fridges, and other appliances, along
>> with routers, firewalls, and other middle boxes.
> If IP enabled fridges can no longer use the LAN, then so be it..
> It may be hard to convince manufacturers of even new devices to  'fix'
>  it, yes, but
> forever is a long time.   And the time it takes is measured  starting
> _from the time the block is no longer marked as special_.   Currently
> deployed printers, fridges, and other appliances have not even been in
> service using IPv4  forever.

I would suggest you consider a Rogers Innovation Adoption Curve
<http://en.wikipedia.org/wiki/Diffusion_of_innovations>, and consider
that for IPv6 alone, estimates for adoption are very very long periods
of time (many decades) [Elmore08 <#Elmore08>][*], and IPv6 is considered
a substantial improvement to the situation such that, absent a paradigm
shift, we will not see need for larger addresses.  Now consider
something with considerably less draw, like 16 (really 15) /8 blocks,
and the incentive to actually code changes for IPv4 would be limited at
best.  Taking this into account, as well as when we think the first use
would be safe for those who would need it, one could conclude "forever"
may very well be accurate in this case.  One way we can test this is
that I can tell you that to the best of my knowledge (and I was one of
the authors proposing using 240/4) we received very little interest from
customers who might  benefit from this space being used, even after we
put an idea forward.  That's a pretty good indicator that we were on the
wrong path. 

There may yet be a right path for 240/4 that we haven't considered. 
Some of your ideas, James, about specific applicable uses of that space
may yet hold water, but would have to be compared against the costs and
benefits of going to v6 at the microeconomics level, because it seems
likely that v6 would be substitutable for many such cases.  The reverse
is assuredly not so.

All of this having been said, we have what amounts to an image problem
with that space, at least for now.  The above analysis is a cursory
summary, and even so is not easily digested.  This leaves the community
open to attacks by those who haven't seriously considered the problem
and may wish to make hay of it.  My only answer to that is that such
open public discussions as the one we are engaged in are very VERY
useful to assure there's not an angle we have missed.


[Elmore08]    Diffusion and Adoption of IPv6 in the ARIN Region, Elmore,
H., Camp., LJ, Stephens, S, Workshop on the Economics of Information
Security, June 2008.
[*] The above paper was an early estimate with limited information.  I
would welcome additional work along the same lines with updated information.

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