[address-policy-wg] IPv6 allocations for 6RD

Hi,

On Mon, Feb 28, 2011 at 10:13:51AM +0100, Kurt Smolderen wrote:
> I strongly support the idea of assigning a smaller prefix to ISPs
> which are in a state of deploying IPv6 but need to use transitional
> mechanism for (some of) their customers. Mark has described one of
> the problems very clear in his email: if an ISP has only a /32
> prefix and needs to use all 32 IPv4 bits in the 6rd configuration,
> only a /64 can be delivered to the home instead of the desired /56
> or /48. Needing all 32 bits is for instance the case when an ISP
> offers internet connectivity to some of its customers via a partnership
> with another ISP.

Without commenting on the general idea of allocating a larger chunk of
addresses to ISPs, I want to make sure that the underlying facts are
presented correctly.

While RFC 5569 (the 6rd RFC) takes the "naive" approach of blindly mapping
IPv4 <-> IPv6 using the whole 32bits, it doesn't *have* to be that way - 
the current 6rd work in the IETF (draft-ietf-softwire-ipv6-6rd-10.txt)
uses a more flexible approach:

---- quote ----
   6rd allows the SP to adjust the size of the 6rd prefix, 
   how many bits used by the 6rd mechanism, and how many bits are left
   to be delegated to customer sites.
...
   For example, if the 6rd prefix is /32 and 24 bits of the CE IPv4
   address is used (e.g all CE IPv4 addresses can be aggregated by a 
   10.0.0.0/8), then the size of the 6rd delegated prefix for each CE is
   automatically calculated to be /56 (32 + 24 = 56).
---- quote ----

so, depending on the size and fragmentation of the IPv4 address allocations 
an ISP might have available, he could run fully-functional 6rd with "/60 to 
end users" in a /36 IPv6 space (by only mapping 24 bits).


So what I would like to see added to this discussion is:

 - what 6rd implementations are there "out in the market" today?
   (both provider and CPE side)

 - what approach do they take?  "always use 32 bits for mapping" or 
   the configurable approach from the i-d quoted above (IPv4MaskLen > 0)?


Gert Doering
        -- APWG chair
-- 
did you enable IPv6 on something today...?

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