Subject: draft-ietf-v6ops-nat64-pb-statement-req-0: native connectivity withdual stack hosts

From: marcelo bagnulo braun <[email-masked]>
Date: Fri, 25 Jul 2008 17:47:28 +0200

Hi

This is follow up on the previous message about dual stack being susceptible to modification or not.
As i mentioned earlier, Dave and Jari have expressed that nodes must 
be able to use native connectivity, in order to avoid apps that are not 
nat compatible to crash.
However, in our current set of requirements, we have 

   R3: Interaction with dual-stack hosts

   Translation mechanism MUST allow using native connectivity when it is
   available.  This means that if a v6-only nodes wants to communicate
   with a dual stack, it must use native v6 connectivity and if a v4-
   only nodes wants to communicate with a dual stack, it must use native
   v4 connectivity.(In this case, dual stack means a host with both IPv6
   and IPv4 stacks, wich are both active, i.e. they have v4 and v6
   connectivity).

whcih in conjuction with R1:

   R1: Changes in the hosts

   The translation mechanism MUST NOT require changes in the v4-only
   nodes to support the Basic requirements described in this section,
   unless explicitly stated in the particular requirement.  The
   translation mechanism MAY require changes to v6-only nodes.

results that IPv6 only nodes, (which in our document must be interpreted 
as a node without a v4 address irrespectively whether it has a v4 stack or
not) MAY require modifications to satisfy this requirement.
So, this means that unmodified ipv6 only hosts may not be able to 
use prefer the native connectivity and hence the apps that are not
nat compatible would not work in these unmodified v6 only hosts.

Do people are ok with this, or people think that we should be stronger 
on this and try that unmodified v6 only hosts can prefer native
connectivity?

One more comment: Imposing this requirement for unmodified v4
only hosts may be impossible to reach... comments?

Regards, marcelo

---

From: Brian E Carpenter <[email-masked]>
Date: Sun, 27 Jul 2008 04:51:00 +1200

Marcelo,

On 2008-07-26 03:47, marcelo bagnulo braun wrote:
> As i mentioned earlier, Dave and Jari have expressed that nodes must be
> able to use native connectivity, in order to avoid apps that are not nat
> compatible to crash.

It seems to me that a dual stack node with no (valid) IPv4
address is going to have to do something today, even in the
absence of nat64, so we can ask what existing stacks already
do in that situation - and once again, it's a good start if
nothing gets worse when nat64 exists.

> So, this means that unmodified ipv6 only hosts may not be able to use
> prefer the native connectivity and hence the apps that are not

And if so, we have not made things worse. And isn't this a defect
that stack maintainers will need to fix in any case?

> on this and try that unmodified v6 only hosts can prefer native

Sorry, I don't really understand what you are suggesting.

> only hosts may be impossible to reach... comments?

You mean that the above MUST NOT may be impossible? Well,
then we can all go home ;-)

    Brian