Hi everybody,

I'm not connected with this presentation (other than having talked to Ben about it prior to his giving it, and I guess supplying some of the information on software that accepts 240/4) but I am one of the people working on the project that he describes/criticizes.

Here is our current proposal.

https://www.ietf.org/archive/id/draft-schoen-intarea-unicast...

People have been reacting to this with different forms of "just do IPv6" for many years. I guess we need an official statement about that somewhere. [Edit: other than these quick thoughts below...!]

I personally think IPv6 is great (I was excited about it in the late 1990s when it was standardized, and gave some talks to promote it, and am happy to see it getting deployed and happy to find myself using it sometimes). I hope people will keep working on it and networks and services will keep adopting it.

However, people's need for IPv4 address space depends enormously on other people's behavior. IPv6 addresses are not a good substitute for IPv4 addresses when you're providing a public service, if many of your users don't have IPv6. A high fraction of demand for IPv4 address resources appears to come from organizations and networks that already support IPv6, because they need dual-stack support for compatibility with other people.

Even though IPv6 adoption has been happening, it's easy to imagine that it's "almost done" where that really doesn't seem to be the case. (This is complicated by having very different statistics in different countries: some countries are now almost all IPv6 traffic, while others have almost no IPv6 -- so people in different parts of the world often have rather different intuitions about it.) We still see enormous economic demand for IPv4 address space and projections that IPv6 adoption to a point where IPv4 would somehow no longer be useful or important is likely still decades away. If that's correct¹, we can still get a benefit from making 240/4 usable because that process can be substantially complete during a time when IPv4 is still extremely important.

One thing that Ben (and one of the questioners at the end) argued in his presentation is that even if the adoption of IPv6 is unreliable or erratic, it might be more reliable than useful adoption of 240/4. (This was kind of phrased in the converse direction.) I'll have to think about models of that issue.

Edit: We have been sad when seeing how proposals to make 240/4 usable were made in 2008, but not adopted at IETF. Among things that people said in 2008 was that IPv6 would make this irrelevant quickly. That turned out not to be right, but we lost years of opportunity to make 240/4 more useful in the meantime, where billions of devices shipped in the interim could easily have supported it by default. So, we still have the opportunity not to have the same sense of regret in 2035.

¹ I'm also aware that there are other projections here; I recently interviewed a prominent Internet greybeard figure who theorized that Internet infrastructure growth as a whole has slowed so much that IPv4 demand may be satisfied in the future out of gradual conversion of residential ISPs to using primarily carrier-grade NAT for IPv4, and then selling off their number resources. In this account, IPv4 will remain important on the Internet for a long time, but economic demand for addresses will decline because most users won't have native IPv4 at home or on their mobile devices (the latter already the case in many networks). The economic demand for IPv4 resources is something that has made reclaiming 240/4 appear worthwhile, so in this model it would become less exciting, even without having IPv4 "go away".