RE: Review of draft-ietf-v6ops-nap-02.txt

["Christian Huitema" <huitema@windows.microsoft.com>]

> On May 31, 2006, at 8:48 AM, Fred Baker wrote:
> > Yes, we support about 3 * 10^38 addresses in the address space.
> > That is a mathematically accurate statement.
> 
> No.  A mathematically correct statement would be that IPv6 can, in
> theory, address up to about 3*10^38 objects.  The number of objects
> that can actually be supported is, of course, far, far less.

The HD ratio equations predict that with 64 bit prefixes, we can number
N = 2^(hd*64) subnets. The current RIR policy assumes hd >= 80%, which
leads to N > 2.59 E+15 subnets. Make that 1E+15 for simplicity. 

In theory, 64 bits and DAD easily accommodate 2^32 hosts, but in
practice the number of hosts in a subnet is dictated by economics and
technology. The average subnet may well contain barely more than one
node, and is unlikely to have much more than 10 today, leading to 1E+15
to 1E+16 nodes. 

In the future, we can imagine personal networks containing hundreds of
devices, so 1E+17 nodes looks plausible.

I cannot really imagine a scenario in which we use 1E+38 addresses.

-- Christian Huitema