[ih] IPv8...

[Andrew Sullivan]

Hi,

On Mon, Apr 20, 2026 at 02:15:11PM -0500, Michael Grant via Internet-history wrote:

>thing I never understood was why there never was or could not be in 
>the near future a sort of flag day that ipv4 became deprecated and you 
>continue to use it at your own peril as it slowly became less 
>connected and the default was a fully connected and working ipv6 
>internet from some day forward?

I largely agree with the points others have made in this subthread, but I think there's something missing in those points too.  On the Internet, there isn't anyone with the de facto control to tell people, "Now!"  It's the Internet.  Nobody can effectively tell people to use this or that address (or to stop).

When NCP was retired in favour of TCP/IP, everyone connected to the nascent Internet had some kind of contractual relationship to a single entity: [D]ARPA.  It was possible for someone in the world to say, "Everyone shall make this change on 1 January 1983," and have the authority to ensure that would happen.  But, whenever you think the "flag day" should have been (or should be in future) for a cutover from v4 to v6, how could you possibly compel every network in the world to follow the instruction?  Since the Internet is a network of networks, there is no place in the architecture for anyone to force your network to follow some central decision-maker. By the same token, there is no way for you to demand that everyone else continues to talk to you over IPv4, and as v4 begins to wither some networks will find that it is more worth it to switch to v6 because it is operationally simpler, and the performance turns out to be better without all the sludge in the way.  But this way of understanding things means that there simply won't be "a date" and, as Dave Crocker and others say elsewhere in the thread, that's probably a fine thing.

Best regards,

A

-- 
Andrew Sullivan
ajs at crankycanuck.ca