[governance] IPv4 - IPv6 incompatiblity (was Re: Towards Singapore)

[Paul Wilson]

Norbert, Izumi, all,

Unfortunately, this "backwards compatibility" issue has been widely 
misunderstood and misrepresented.  Personally, I'm tired of dealing with 
journalists who have been told that v4 and v6 are like "oil and water" and 
don't mix, and who ask if IPv6 users need to buy different services, 
different cables, different equipment, different email address, etc etc to 
stay online.  It takes quite some explaining to undo that bundle of 
misconceptions!

Yes, at one level v4 and v6 are incompatible, naturally, because they are 
Different Protocols; but above and below the IP protocol level, they are 
perfectly "compatible" - they run side by side on the same wires, through 
the same equipment, and on the same services as each other; and they 
support the same applications, which work in the same way, to the extent 
that users don't even need to know.

I've promoted an analogy between the v4-v6 transition and the transition 
from oil to electricity in our transport system.  And it works for this 
discussion as well:  you don't try to plug your volkswagon beetle into the 
mains - because oil and electrons certainly don't mix - but that old car is 
still perfectly "compatible" with the latest electric one: it drives on the 
same roads, uses the same rules and the same controls; and carries the same 
passengers in the same way.

As for "backward compatibility" I suggest to be careful what you ask for 
here, because that is always a temporary benefit, and often a long-term 
curse. MS Windows users have suffered vast costs and complexities for many 
years, just so that a few MS-DOS applications could keep running; and then 
there's the old  QWERTY keyboard.

On the other hand, we might remember the complaints surrounding Apple's 
change to OSX, a completely new and incompatible operating system (well, 
being based on Unix, a completely OLD operating system).  But does anyone 
care about that any more?  No, it's been properly forgotten, just as IPv4 
will be when the big transition is done.

I admit to blissful ignorance of the blow-by-blow disputes and politics of 
the development of IPNG in its various early flavours; and I don't care 
much to go back there.  But I can certainly imagine that if IPv6 were 
shackled with tricks to have it interconnect directly with IPv4, at the IP 
level, then in a few years time, and for decades afterwards, we'd all be 
cursing the developers for their shortsightedness.

My view is that the only significant sin of the IPv6 developers, at least 
the only one which is relevant here, is to have underestimated the coming 
success of the Internet.  It is that success which allowed the Internet to 
grow so vast and to become so very cheap, the major factors which conspire 
to make the IPv6 transition much harder than anyone thought.

Thanks.



________________________________________________________________________
Paul Wilson, Director-General, APNIC                      <dg at apnic.net>
http://www.apnic.net                                     +61 7 3858 3100




--On 16 June 2011 6:30:25 PM +0900 Izumi AIZU <iza at anr.org> wrote:

> Or, what was the biggest reason/rationale not to make IPv6 compatible
> with IPv4. Was there good assumption that IPv6 will
> "take over" that of IPv4 - I mean replacing IPv4 rather than
> co-existing with IPv4 for a considerable period of time which
> is, in my view, the situation today. The full, immediate "transition"
> model.
>
> izumi
>
>
>
> 2011/5/27 Norbert Bollow <nb at bollow.ch>:
>> McTim <dogwallah at gmail.com> wrote:
>>
>>> Certainly the IETF could have made the v6 compatible with v4, but they
>>> didn't.
>>
>> In what way would it have been technically possible to make IPv6
>> compatible with IPv4?
>>
>> Greetings,
>> Norbert
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________________________________________________________________________
Paul Wilson, Director-General, APNIC                      <dg at apnic.net>
http://www.apnic.net                                     +61 7 3858 3100

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