[arin-ppml] Draft Policy 2011-5: Shared Transition Space for IPv4 Address Extension - IAB comment

[William Herrin]

On Tue, Jun 28, 2011 at 10:50 AM, Joel Jaeggli <joelja at bogus.com> wrote:
> On Jun 28, 2011, at 5:50 AM, Jimmy Hess wrote:
>> On Tue, Jun 28, 2011 at 1:43 AM, Joel Jaeggli <joelja at bogus.com> wrote:
>>> On Jun 27, 2011, at 11:24 PM, Benson Schliesser wrote:
>>>> On Jun 28, 2011, at 0:25, David Kessens <david.kessens at nsn.com> wrote:
>>> It's new private scope v4 address space carved out of ipv4 unicast space. by definition it breaks assumptions that existing hosts and applications make about non-rfc-1918 space.
>>>
>> [snip]
>>
>> What assumptions would those be?
>
> That a port mapped to a the outside of a cpe which does not
> have an rfc 1918 address will in fact be reachable (example
> by upnp or nat pmp)

That's ASS-U-ME assumption. Lots of places uses non-RFC1918 addresses
inside their NATs and those which don't often have other forms of
filtering and firewalling which obstruct global reachability inbound.

You can only assume the opposite - that a port mapped on an RFC1918
address won't be globally reachable. Nothing in proposal 2011-5 breaks
that assumption.

> That an ipv4 unicast address can be used as source or
> destination for an auto-tunneling mechanism.

And again.


> Aa specific example of the later with an rfc-1918 address
>assignment an existing implmentation of 6to4 will simply
>fail, which is the desired behavior

No, actually, it is not the desired behavior, at least not by me. In
fact, it obstructs the use of 6to4 on private networks where it could
otherwise facilitate a staged IPv6 rollout. I ran in to this, much to
my frustration, back when I was tinkering with 6to4.

If there's a case where a device or protocol should make positive
assumptions about global reachability based on its assigned IP
address, I haven't heard it yet.

Regards,
Bill Herrin


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