Re: IPv6 traffic stats - limitations of 6to4

[Pekka Savola <[e-mail]>]

On Thu, 13 Nov 2008, Rémi Després wrote:
>>  If an implementation implements RFC3484 and the user is not using custom
>>  address selection policy, all compliant RFC3484 implementations should
>>  prefer v4 when connecting to native from 6to4 (rule 5 of destination
>>  address selection AFAIR).

Actually, my above statement is incomplete.  Thanks for your eagle 
eyes :-)

In case the user has a RFC1918 IPv4 address and the destination is 
global v4 address, you'd use 6to4.  In case IPv4 address is global and 
destination is global, or both are RFC1918, you would use IPv4.

As such:

> Can we derive from this that Google's IPv6 address is necessarily 
> 6to4 (most of its US customers using it are 6to4), and that Google 
> has therefore a guaranteed path toward other 6to4 hosts?

I believe Google is using native addresses.  The 6to4 hits are 
probably caused by the users with private v4 addresses or users whose 
implementation does not support rfc3484.

> Besides, isn't this a strong reason in favor of native IPv6 (albeit like Free 
> did it with 6rd on its IPv4 infrastructure) vs 6to4?

Native is in many cases better than 6to4 or Teredo (but in some cases 
6to4 <-> 6to4 is better than native).  But this is something I 
specifically didn't comment on in my mail.

-- 
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings

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