legacy /8

George Bonser gbonser at seven.com
Sat Apr 3 14:09:51 CDT 2010

> -----Original Message-----
> From: marka at isc.org [mailto:marka at isc.org]
> Sent: Saturday, April 03, 2010 11:42 AM
> To: George Bonser
> Cc: Larry Sheldon; nanog at nanog.org
> Subject: Re: legacy /8
> And we would have still had the same problem of intercommunicating.
> We know how to talk from IPv6 to IPv4 and get the reply traffic back.
> The hard part is how to initiate connection from IPv4 to IPv6.  The
> same problem would exist in your "just expand the address bits world".
> Mark

Actually, Mark, I hadn't said "just expand the address", I said to
tunnel v4 in v4 which we already know how to do and most routers are
already capable of doing.  But yes, in the case of legacy devices that
don't "speak" the new protocol, some sort of state for the flow would
have to be maintained in that unit's first hop (or close to first hop)
gateway. Simply increasing the address header on v4 to 128 bits would
have fixed this problem years ago and got rid of such problems as NAT
and we wouldn't be having this issue (and it would have been completely
backwards compatible as 0s would be inserted into the new expanded
address bits to put the legacy space in a special address range.

I wouldn't expect to work out all the details over email on a weekend
but I don't think it would take 10 years, either.

The fundamental issue to me is that v6 solves a lot of problems that
aren't really problems for most people and to get the fix that solves
the problem you do have, you must accept a bunch of additional "fixes"
for problems you don't have that makes the whole thing some big unwieldy

That having been said, once the world has migrated to v6, we should have
an easier go of it in the future as v6 is more easily extensible.  But
in the meantime, we are stuck with both protocols for probably the next
20 years or so as there are going to be places that are going to run v4
internally even if they communicate v6 externally.

So ... "we are going to mandate that everyone use this new and better
car but it will take different fuel, use different tires, won't fit in
your garage and oh, it is incompatible with all existing roads unless
you load it up on one of the old style vehicles piggy-back, but new
roads are being built (here's a picture of one) and might someday be
available where you live. And two years from now there will be none of
the old cars left."  But my daughter will need a car in three years and
there are no such roads here. "Oh well! The new way is much better, it
is for your own good, you will see.  Trust me".

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