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

From: "Christian Huitema" <[email-masked]>
Date: Thu, 1 Jun 2006 00:23:39 -0700

> 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

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From: "Eric Klein" <[email-masked]>
Date: Thu, 1 Jun 2006 12:36:22 +0200

> From: "Christian Huitema"

I appreciate this effort for mathmaticial accuracy, but I think we have lost 
sight of the originl issue:
How many is not an issue in this draft, but the fact that IPv6 < > infinate 
pool numbers and NAT is not the solution recommended for this reality.

---

From: "Tony Hain" <[email-masked]>
Date: Thu, 1 Jun 2006 08:45:59 -0700

> pool numbers and NAT is not the solution recommended for this reality.

Responding to those who believe that cascaded NAT provides an even greater
amount of space than IPv6 I have added the following in the middle of the
second paragraph of 2.6:

... This happens even though the private use address-space is strictly
limited in size. Some deployments have already outgrown that space and have
begun cascading NAT to continue expanding. Unfortunately, the number of and
types of applications that can be deployed by these ISPs and their customers
is restricted by the ability to overload the port range on the public side
of the most public NAT in the path. The result is something substantially
less than 2^48 possible active application endpoints, rather than the
perception of arbitrary utility from the large number of addressable
devices. In addition it is highly likely that nodes will become confused
because they are not topology aware, though as already mentioned NAT
enforces a specific application deployment model.  ...

Tony