draft-ietf-v6ops-nat64-pb-statement-req-00 - are changes in dualstack hosts acceptable or not?

[marcelo bagnulo braun <marcelo@it.uc3m.es>]

Hi,

both Jari and Dave have expressed during email exchanges that unmodified 
dual stack hosts must work well WITHOUT requiring modifications. In 
particular, they expressed that a dual stack host must be able to 
distinguish between the transalted connectivity and the native 
connectivity allowing them to avoid translated connectivity hence 
avoiding failures in apps that don't work through nats.

However, in the current req doc 
(draft-ietf-v6ops-nat64-pb-statement-req-00) it is stated that:

  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.



In the list of basic requirements there is another requirement:

  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).


Now, the nice thing about requirements is that when you read 
them into detail, they can be interpreted in both ways.

So, the question is: is a dual stack host a v6 host (i.e. changes are 
acceptable) or is it
a v4 host (i.e. changes are not acceptable)?


Regards, marcelo