On 10-okt-2007, at 15:31, Thomas Narten wrote:
If there was a magic "trivial" transition/upgrade strategy, we would
have done it years ago.
How about this: we magically go back 10 years in time and define
"IPv4.6" which is the first 32 bits of the IPv6 address in the IPv4
address fields and the other 96 bits in a new header that sits
between the IPv4 header and the upper layer protocol (TCP/UDP/etc).
IPv4 stacks are updated to copy back the extra header with the lower
96 bits whenever sending packets in reponse to ones with those 96
bits in them.
I'm pretty sure we'd still have issues with unupgraded TCP stacks and
firewalls, but just implementing the simple copyback mechanism and
adjusting firewalls accordingly would be a much simpler way for
existing IPv4 users to be able to talk to IPv6 users than adding IPv6
to their networks. Applications on the IPv4 host that are unaware of
the fact that they're talking to an IPv6 host would still have NAT
issues, but it would also be possible to run applications that know
about the IPv6 address of the correspondent so the communication
would be end-to-end clean.
(Ok there would have to be some extra bit shuffling to avoid using up
the IPv6 address space as fast as the IPv4 space but that's just
details. Maybe copy bits 4 - 31 and set bits 0 - 3 to 1111 in the
IPv4 address if they are 0010 in the IPv6 address.)
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