Today is World IPv6 Day, a day when major content providers have agreed to furnish service over IPv6 for a 24-hour test period. Hopefully, you didn't notice anything different about your Internet experience today, but providers will have gained valuable experience with the technology and any technical hurdles that remain to be overcome. In this blog, we'll report on how far into the IPv4-to-IPv6 transition we actually are and, more importantly, just how far we have to go. There is no denying that there has been a tremendous amount of progress in the last decade or so, but much remains to be done and we are only at the very beginning of a long process.
As has been reported by Renesys and endlessly in the press, the world is running out of usable IPv4 addresses, which are 32-bit numbers and hence limited to 4 billion distinct values. With every mobile device, desktop, server and (maybe soon) light bulb needing an IP address for connectivity, we simply don't have enough. The only long term game in town is IPv6, a new system with 128-bit addresses or 340,282,366,920,938,463,463,374,607,431,768,211,456 distinct values. (We aren't going to make that mistake again!) Unfortunately, these different addressing schemes are not compatible. If you want to provide content on both "Internets", you need IPv4 and IPv6 addresses for your servers and you need all the infrastructure that goes along with both approaches.
What is World IPv6 Day anyway?
When it comes to upgrading the Internet in place, there are a lot of moving parts to consider: end-user operating systems, home networks, routers, firewalls, servers, Internet service providers, applications, and so on. Despite all the transition planning that has been carried out to date, a lot can go wrong. If a content provider suddenly started supporting both IPv4 and IPv6 on the same domain, that action alone could prevent some customers from gaining access. World IPv6 Day gives the major providers cover to make this change at the same time to see what happens. In other words, if you couldn't reach Google today since they turned on IPv6 support, well you couldn't reach Yahoo or Microsoft either. For domains participating in this experiment, DNS should return IPv4 and IPv6 addresses. What your computer ends up doing with the very different answers depends on all the factors mentioned above. And from this experience, the providers hopefully gain valuable insight into what needs to happen next.
Are the Internet service providers ready for IPv6?
Only somewhat. A lot has been accomplished, but much of it has been limited to the largest global and regional players on the Internet and the most developed countries. On either "Internet", connectivity requires blocks of IP addresses (prefixes) and Autonomous Systems (ASes) to handle the routing of traffic. So it's natural to compare both Internets relative to these quantities. In IPv4, we currently see over 360,000 routed prefixes, distributed (unevenly) to pretty much every country on earth. In IPv6, we only have around 6,500 prefixes with a concentration in the developed world as shown in the following map.
(Note: IP address geo-location is a tricky business and only more so with respect to IPv6, where tunnels are often employed. We've made our best approximations here, but if you feel there are inaccuracies, please let us know.)
As for ASes that originate IPv6 prefixes, only 13% of those seen in the IPv4 world are also seen in IPv6, although there has been a recent slight up-tick in interest as shown in the following graph. And it is clear that the IPv4 Internet is still growing at consistent rate.
Another way to visualize IPv6 adoption is to consider those ASes that transit only IPv4 compared to those that transit both IPv4 and IPv6. In the next image, ASes transiting IPv4 only are shown as red dots and those transiting both as blue dots. Dots in the outer ring correspond to ASes with no customers. As you move toward the center, inner rings depict ASes with more and more customers. The barely visible dots near the center correspond to the so-call Tier-1 providers. (Each dot representing an AS is placed at a distance from the center that is inversely log-proportional to the number of downstream customers the AS has.) As you can see, the largest providers are ready for IPv6, as it is becoming a competitive differentiation, however, much of the rest of the world is sitting on the sidelines.
Are the content providers ready for IPv6?
No. As expected, the major players are there, but keep in mind that there are over 108 million .com and .net domains alone. From our estimates, much fewer than 0.1% of these domains also have some sort of IPv6 presence. So even if you do have IPv6 connectivity today, the IPv6 Internet is quite barren compared to the IPv4 Internet. Basically, there isn't much to see on the IPv6 Internet and, whatever is there, is almost certainly replicated in the IPv4 world.
Are consumers ready for IPv6?
In general, consumers simply want Internet access and don't think in terms of IP addresses or the underlying technology. Fortunately, modern operating systems generally have mature IPv6 support. Where consumers might run into difficultly is with their access devices (e.g., DSL/cable modems) or the fact that their provider is one of the many lacking IPv6 support. If you want to test out your own IPv6 connectivity, you can go here and, if all is well, you might see output of the following form.
Presumably, the end user equipment will take care of itself as technology is refreshed. Currently, busy DNS servers worldwide show that about 20-25% of clients are making IPv6 queries. This adoption rate is slowly increasing over time.
Impediments to Adoption
The IPv6 Internet lacks two critical ingredients for success: users and content. In this chicken-and-egg dilemma, many organizations have no interest preparing for a largely barren IPv6 Internet and content providers aren't going to waste resources on an Internet with no users. The economic driver is currently absent for many.
But there is another large barrier to progress that is not getting much publicity. The IPv6 Internet is not fully connected. That's right, even if you have IPv6 connectivity today, you might not be able to reach the entire IPv6 Internet, as small as it might be. The IPv6 Internet lacks a fully connected mesh of "Tier-1" providers. Our data supports the information about this partitioning found here. As one example, if you have IPv6 connectivity solely from Level 3, you cannot reach those who are solely dependent on Hurricane Electric. This is very different than the IPv4 world, where any single provider will generally take you everywhere you want to go (ignoring issues of government censorship).
We'll close out this blog with more questions than answers. Future growth in IPv6 deployments could very well depend on how the following are answered.
- Will the growth of mobile devices and their need for address space finally spur businesses to seriously invest in an IPv6 presence?
- Will developing world demands on IP space boost global IPv6 adoption rates?
- Will a robust secondary market develop for IPv4 addresses that will further delay IPv6 adoption? With or without the blessing of the registrars?
- Will scarcity of IPv4 addresses erode cooperation on the Internet?
- Will an alternative technology, such as carrier grade NAT, reduce the need for routable IPv4 addresses?
- Will a fully connected set of IPv6 Tier-1s finally emerge, allowing end users to reach the entire IPv6 Internet via any single IPv6 carrier?
- Will any future government mandates encourage IPv6 adoption?
- Will interoperable and ubiquitous support for IPv6 eventually exist in all devices?