As with IPv6 deployment among access providers, deployment among content providers is growing. Among websites, according to Roberts, the five top sites as measured by Alexa all support IPv6, and they account for a substantial portion of total IP traffic. One of those sites, Google, continually collects statistics about IPv6 adoption and shares them in a graph whose curve shows a steady upward trend.
However, while the shape of the curve is encouraging, in absolute terms the number of users accessing Google via IPv6 is barely above 3% of all users. Still, "that's more than double what it was a year ago," Roberts says, and IPv6 traffic is growing at a faster rate than IPv4, which Roberts sees as a promising sign.
The Internet Society also makes ongoing measurements of IPv6 deployment on its World IPv6 Launch site. It shows that 13 percent of the Alexa Top 1,000 websites are currently reachable over IPv6. "That number was 10 percent a year ago," Roberts said. In addition, the Internet Society checks the number of network operators who are turning on IPv6. "The first time [we reported on the statistics] we had about 70 networks," Roberts says. "Now we're up to 226."
With endpoint hardware providers, IPv6 readiness is a mixed bag. "A lot of devices in the home don't use it yet," Roberts says. However, the fast-growing cell phone market is a different story. Cell carriers are making progress supporting IPv6-enabled devices. For instance, Roberts points to Verizon Wireless. "All of its new smartphones have IPv6 enabled," he says, and T-Mobile recently announced that its Android 4.4 phones will default to IPv6 only for connecting to its mobile network.
Some gaming console manufacturers too are jumping on the bandwagon. In October, Microsoft's Chris Palmer announced at NANOG 59 that the Xbox One gaming console will use IPv6 with IPsec for peer-to-peer communication between gamers, and said that performance will be best when end-to-end communication is over IPv6.
That end-to-end, IPv6 connection may be elusive when content delivery networks are involved. Some CDNs, such as Limelight, turn on IPv6 by default for their customers, but others, such as Akamai, do not. Akamai's Erik Nygren says, "Most of our customers have very rich environments that still require end-to-end testing prior to dual-stacking."
One problem is that customer-premises equipment (CPE) has to be capable of supporting IPv6 and properly configured to do so, and not all CPE currently in production can claim that. Nevertheless, Akamai reported in June that roughly 1.5 percent of the content requests it sees come in over IPv6 -- a rate that is about double what it saw a year previously.
Over the entire network ecosystem, including carrier hardware and networks, CDNs, corporate networks, home electronics, mobile devices, and content providers, there is steady progress in IPv6 implementation.
Unallocated IPv4 address blocks are gone forever. However, carriers still have IPv4 addresses available for allocation, so IPv4 addresses will remain in use for some time to come. And though there may be no immediate crisis for service providers, businesses, or customers, there is steady pressure to enable IPv6 in every segment of the network ecosystem as the best way to address IPv4 address scarcity.