[arin-ppml] V6 address allocation policy

William Herrin bill at herrin.us
Sun Jan 17 10:46:03 EST 2010

On Sat, Jan 16, 2010 at 7:55 PM, Owen DeLong <owen at delong.com> wrote:
> On Jan 16, 2010, at 4:28 PM, Michael Richardson wrote:
>>  If techies need to get their managers to approve a checque to ARIN,
>> the manager tells them to use IPv4 + NAT.  If the techies do not have to
>> ask, then they will deploy IPv6 for internal use.

No joke on that. Three years ago my boss turned me down on deploying
IPv6 in my spare time at work on the grounds that there were wiser
ways to spend the $1250.

>>  (ULA buys you nothing compared to net-10)
> 1.      ULA buys you a great deal more than RFC-1918.  ULA is statistically,
>        if not globally unique.

Not exactly... The analysis in RFC 4193 (ULA addressing) section 3.2.3
is technically correct but it may be an example of "lies, damn lies
and statistics."

First, though de-emphasized in the RFC, the probability of collision
has a phenomenal growth rate: two orders of magnitude for ever one
order of magnitude increase in the number of ULA IDs. So you close in
on a 100% chance of collision not at 2^40 IDs as you'd expect but at
merely 2^20.

Second, consider the way folks tend to behave. Each private network
built for whatever purpose in a particular company will consume one or
several ULA IDs. That's each private network in each project at each
branch of a company. A large company may well have consumed hundreds
if not thousands of ULA IDs introducing another four to six orders of
magnitude increase in the probability of collision when two such
companies want to connect.

Practically speaking, we should start to see anecdotes about ULA
collisions as folks try to connect 100 to 1000 organizations together,
still a usefully large number but far fewer than RFC 4193 implies.

Bill Herrin

William D. Herrin ................ herrin at dirtside.com  bill at herrin.us
3005 Crane Dr. ...................... Web: <http://bill.herrin.us/>
Falls Church, VA 22042-3004

More information about the ARIN-PPML mailing list