Re: [BEHAVE] Comments on draft-bagnulo-behave-nat64-00

Brian E Carpenter escribió:
> On 2008-07-21 08:33, marcelo bagnulo braun wrote:
>   
>> Iljitsch van Beijnum escribió:
>>     
>>> On 20 jul 2008, at 21:42, Jari Arkko wrote:
>>>
>>>       
>>>> However, I'd be interested in learning more about what Iljitsch
>>>> mentioned about current devices not allowing v4-mapped addresses on
>>>> the wire. As Dave mentioned, RFC 2765 uses them, and a quick test on
>>>> the Linux box that I'm writing this e-mail on shows that I can use
>>>> these addresses on the wire. Can you be more specific about what
>>>> problems you expect, and where, Iljitsch?
>>>>         
>>> IIRC, Itojun was _extremely_ vocal about not allowing these on the
>>> wire, and I think he got some traction in this area from at least some
>>> of the *BSD people.
>>>
>>> Also, stacks implement special case logic for these addresses as they
>>> must result in IPv4 packets when the host is dual stack, I don't know
>>> if this logic is still applied if the host is running IPv6-only, or
>>> normal IPv6 packets are generated.
>>>
>>>       
>> see http://tools.ietf.org/html/draft-itojun-v6ops-v4mapped-harmful-02
>>     
>
> Exactly. This prefix has implied semantics, and worse, it has
> *ambiguous* implied semantics: one version for NAT[-PT|64]
> and another for the dual-stack socket API.
>
> For NAT64, I think we're reducing topological flexibility by using this
> prefix, as well as ignoring the ambiguity. If an arbitrary prefix is
> allowed, the NAT64 doesn't have to be in the same administrative domain
> as the host.
>   

why would it have to be in the same domain as the host if we use the 
v4-mapped prefix?
> I suggest therefore having a default prefix plus the option to discover
> or configure an alternative.
>
>   
but if we use other prefix than the v4-mapped prefix, it is not in the 
default policy table and then we loose the capability mentioned by Dave 
of automatically preffering native connectivity in dual stack hosts, 
which i find very attractive

OTOH, an additional fear that i have using a single globa prefix for 
respresenting the whole v4 address space is that we may end up needing 
to use more specifics, if we want to reach different parts of the v4 
internet through different routes, hence importing the v4 routing table 
to v6, but i don't know if you think there is any ground for this 
concern...?

Regards, marcelo

>     Brian
>
>
>
>   

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