BBC News - 'Fresh proposals' planned over cyber-monitoring

[Ian Batten]

On 11 May 2013, at 17:26, Roland Perry <lists at internetpolicyagency.com> wrote:

> In article <EADEBDCB-9FBA-4EAA-ADC8-444B93CAD478 at batten.eu.org>, Ian Batten <igb at batten.eu.org> writes
>>> Basically, the people who specified IPv6 screwed up, big time, in not making it backwards compatible. They've got all sorts of excuses, that
>>> only geeks who understand products, but not product management, would relate to.
>> 
>> It would be interesting to understand what such a protocol would look like.  The basic problem surely is that if you have two address spaces,
>> one larger than the other, you can't have a 1:1 mapping between the two (and to do so would defeat the object of making the address space
>> larger).
> 
> All that was necessary was making the bottom 0.1% (or whatever) of IPv6 map onto the old IPv4 space.

If only someone had thought to insert a paragraph into RFC 2373, fifteen years ago, defining an IPv6 address whose first 80 bits is zero, following by 16 bits of one, as being an IPv4 address mapping into the IPv6 space, and thought to call them, oh, I don't know, an "IPv4-mapped IPv6 address".  They could have inserted it between sections 2.5.3 and 2.5.5, perhaps, and made things much easier.

ian