about the coexistance scenarios in draft-ietf-v6ops-nat64-pb-statement-req-01

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

Hi Teemu,

I am trying to intergrate the text you proposed to the draft 
draft-ietf-v6ops-nat64-pb-statement-req-01

the last text we come up with was:

to add a new scenario:

  o  a dual stack system connected to a IPv6 domain that is connecting
     to an IPv4 system.

and to add new text in the tunnel section:

  Another scenario that does not involves translation is the case where
  a dual stack node is connected to an IPv6-only domain and it is
  communicating with a IPv4-only node as depicted in Figure 2.


                                            ,-----.                 ,-----.
                                          ,'       `.             ,'       `.
                                         /           \           /           \
                                        /   IPv6-only \         /   IPv4-only \
                                       /    Domain   +-----------+  Domain     \
                                      ;              |    Tunnel |              :
                                      |              |  endpoint |              |
                                      :     +-----+  +-----------+              ;
                                       \    |Dual |    /       \     +----+    /
                                        \   |Stack|   /         \    |IPv4|   /
                                         \  |Host |  /           \   |Host|  /
                                          `.+-----+,'             `. +----+,'
                                            '-----'                 '-----'

        Figure 2: Dual stack with IPv4 application in IPv6 domain

  In this case, the dual stack host needs to establish a IPv4 in IPv6
  tunnel to the tunnel endpoint.  In addition to that, the dual stack
  needs to obtain a IPv4 address that is valid in the IPv4-only domain.
  The simplest option is for the dual stack to obtain an IPv4 public
  address.  However, this may not be possible due to the shortage of
  IPv4 public addresses.  The other option is to use an IPv4 private
  address (and potentially in conjunction with IPv4 NAT).  The other
  option is for the dual stack to obtain one or more public IPv4
  transport addresses.  In all the cases, the acquisition of the
  address can be performed dynamically.

the problem that i find is that the scenario described above is simply 
too broad to what we mean here.
I think that something you mentioned in your original mail got lost in 
the way, basically that this scenario is about dual stack hosts running 
v4 only apps that are nat aware, that is the main reason why you need 
them to learn the v4 public address. Dan mentioned that for instance 
bittorrent is in this situation.

So, i think we need to express this somehow.
I think that the scenario that we are handling now is

  o  a dual stack system with a NAT-aware IPv4-only application connected to a IPv6 domain that is connecting
     to an IPv4 system.

Now, i am wondering if this is not a bit too far off the simple scenario 


Regards, marcelo