For reasons beyond the scope of this entry, I wound up thinking about thinking about the (potential) transition to IPv6 again today. In the past I've been solidly gloomy on the prospects for a transition to IPv6, in large part because IPv6 doesn't benefit the people who have to do the work; the people who benefit from a transition are the people who don't already have IPv4 addresses, not the people who do. But today a potential path out of this occurred to me.

First off, let's assume that people start running out of assignable IPv4 addresses, as seems quite likely. When this happens, what we'll probably start seeing (and what has apparently started in some places) is consumer IPv6-only deployments that talk to the IPv4 world through large 'carrier grade' NAT systems. This only really allows outgoing connections (at least for IPv4 stuff), but for many ISPs that's a feature; if you want to run a server you can pay them for the privilege.

(If all of the software works fine most consumers won't care or notice.)

Of course even carrier grade NAT is not perfect or completely transparent. This is likely to result in an experience that's worse than directly accessing the same web site or other resource over native IPv6. With a worse experience for IPv4 than IPv6, if you want to do a good job serving these consumers you have an incentive (possibly a big one) to provide native IPv6 connectivity for your own services.

In other words, now you have a positive economic incentive to add native IPv6 support to your systems. Positive economic incentives (aka 'making more money') make the world go around, because they give organizations a concrete reward for the work they do.

(I will note in passing that the consumer ISPs involved have their own economic incentive to encourage IPv6 connectivity; the more native IPv6 their customers do, the less they need those expensive carrier grade NAT boxes.)

Where are these consumers? I think they're likely to be in what we today consider somewhat the peripheries of Internet usage, the places where it is only a recent development. North America generally has plenty of IPv4 addresses for its population, while places like Asia, Africa, and the Middle East are probably under-supplied. If this path to IPv6 is accurate, I'd expect to see serious IPv6 usage first show up in companies that are targeting these 'peripheral' users. And I wouldn't expect these companies to be based in North America.

(In fact I wouldn't be surprised if North America and western Europe wind up lagging the rest of the world in any IPv6 transition. The bigger question is if that will matter much.)

(All of this was in part sparked by (re)reading Avery Pennarun's entry on IPv6 from early 2011, due to reading this more recent entry of his.)