Biggest mistake for IPv6: It's not backwards compatible, developers admit

[Fred Baker]

Also, I think it is only fair to point out that they didn't have the  
option of making it backwards compatible with IPv4; it's not that they  
didn't, it's that they couldn't. How, precisely, would you make an  
IPv4 packet that has longer addresses? IPv4 forces any change to the  
header to become a new protocol.

I could imagine making a protocol (IPv17 if you like) that was a  
different protocol than IPv4 but had a variable length address: for  
example, it might be a tuple that contained the length of the tuple,  
the length of the network part, the length of the host part, the  
network part, and the host part. If the other fields were the same as  
IPv4, one could imagine deploying the new protocol in such a way that  
a translator could go between them, and put IPv17 in the backbone. We  
would be in a position much like we are now, however; from 1995 until  
now nobody would see a business justification for deployment, and  
folks who deployed would find that they had a hard time talking with  
folks who had not. It would be essentially the same issue we face now.

On Mar 26, 2009, at 2:07 PM, Scott Beuker wrote:

>>> I don't see the point of raking over history.
>>
>> The value would be in recognizing the mistakes that were made and
>> learning from them in order to avoid making them again. Unfortunately
>> I don't see any willingness to take an honest look at the mistakes
>> that were made, so you're right, there is no value in rehashing the
>> history.
>
>
> Furthermore, I think it's highly debatable whether the big mistake
> was technical (a lack of backwards compatibility), or business (the
> industries lack of timely action). Or both.
>
> It seems to be fashionable this month to point the finger at IPv6 for
> having failed us, but dual-stack could have been a solid transition
> mechanism if started earlier. But, you know, something about leading
> a horse to water and then he doesn't drink.
>
> - Scott Beuker