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[ih] Could it have been different? [was Re: vm vs. memory]

On 10/25/2017 12:10 PM, Brian E Carpenter wrote:
> On 26/10/2017 02:13, Noel Chiappa wrote:
> ...
>> Needless to say, had I still been on the IESG
>> at the time of the IPv6 process, that design would _never_ have been accepted
>> - 'over my dead body'.
> Counterfactuals are always fun. However, I believe that the sad fact is that
> *no* IPng solution of any kind whatever could in practice have been deployed
> smoothly. Why? Because of Tim Berners-Lee, Marc Andreessen and a few other
> people. By the time any IPng code could have been available (the first
> commercial release of IPv6 code was in 1996), the growth rate of IPv4 and
> the inevitability of NAT44 made deployment very hard indeed; the incentives
> were all for deploying more and more IPv4, and remained that way for 15+
> years.
> Now that IPv4 is truly hitting its limits, the main operational complaint
> against IPv6 is that it's too different from IPv4. But the incentives are
> finally shifting in IPv6's favour, like it or not.
> The reason that there is still thrashing in IPv6 transition discussions
> is that the original IPv6 transition plan was designed for a different world.
> I suspect that the root cause of the IPv6 issues that John Levine mentioned
> lies there.

Certitude about hypothetical pasts also is fun, but possibly 
distracting.  In this case, the premise is that nothing could have 
dislodged IPv4.  Yet we have quite a few examples of other major 
infrastructure upgrades -- and at different levels -- that worked well, 
or at least that worked.  There should be some respect for those 
accompishments and some attempt to understand why they succeeded when 
others -- such as IPv6 -- has not.

To work, an upgrade must either have no effect on the rest of the 
installed base, or it must have strong adoption incentives for those 
doing the adopting.  IPv6 has always suffered from more idealism in its 
incentives than immediate, operational pragmatics.

By way of reiterating a hypothetical alternative IPv6 approach that I've 
offered a number of times:

If Deering's original, simple IPv6 -- which only did exactly what was 
needed and did it cleanly, with a hook for /future/ enhancements -- had 
been adopted pretty much as is, the core IPv6 code would be very nearly 
identical to IPv4 code.

If the initial administration of address space were to apply the 
/existing/ IPv4 addresses -- reserving the remainder for later -- then 
v4/v6 interoperability would have required trivial gatewaying.  By the 
time more address space was actually needed, there would be a 
non-trivial amount of IPv6 code in operation.

The hand-wave, here, is for the application interfaces to IPv6 and, yes, 
that's additional, essential detail.  But my real point is that careful, 
focused attention to adoption as an incremental enhancement to the 
existing IPv4 infrastructure -- rather than inventing a completely 
independent, parallel stack -- then we could have started getting IPv6 
operational experience long before the end of the 1990s.


Dave Crocker
Brandenburg InternetWorking