The Internet needs IPv6 because it is running out of IPv4 address space. The free pool of unassigned IPv4 addresses expired in February, and in April the Asia Pacific region ran out of all but a few IPv4 addresses being held in reserve for startups. The American Registry for Internet Numbers (ARIN), which doles out IP addresses to network operators in North America, says it will deplete its supply of IPv4 addresses this fall.
DETAILS: Asia out of IPv4 addresses
But as necessary as IPv6 seems, there is a major stumbling block to its deployment: It's not backward compatible with IPv4. That means website operators have to upgrade their network equipment and software to support IPv6 traffic. So far, most have been unwilling to do so because IPv6 traffic has been so scarce.
One of the only regular surveys of Internet traffic is compiled by Arbor Networks, which recently reported that IPv6 represented less than 0.2 percent of all Internet traffic. Arbor said IPv6 traffic -- both tunneled and native -- had declined 12 percent in the last six months, even as momentum for World IPv6 Day was building. Arbor gathered this data by surveying six carriers in North America and Europe.
Not everyone believes Arbor's assertion that IPv6 traffic is declining while so many website operators are preparing for World IPv6 Day.
"I did not see this [data], and I am also very surprised if it is accurate," says Russ Housley, chairman of the Internet Engineering Task Force, a standards body that created IPv6. "I am aware of many organizations preparing for World IPv6 Day."
Martin Levy, director of IPv6 strategy at Hurricane Electric, a Fremont, Calif., ISP that claims to have the world's most interconnected IPv6 backbone, says he is struggling with how the Arbor Networks data can be true given the network industry momentum behind IPv6. "Where Arbor measures is not where the predominant IPv6 usage is," Levy says.
BACKGROUND: The 6 biggest misconceptions about IPv6
What's preventing the Internet engineering community from coming up with more complete IPv6 traffic statistics is the fact that few ISPs or their hardware suppliers have deployed a network management tool called NetFlow 9. This industry standard export protocol sends data about traffic flows through the router to an external collection host so that the flow information can be analyzed. NetFlow 9 can be used to separate out and measure IPv6 and IPv4 traffic flows.
NTT America, a leading provider of IPv6 transit services, concedes that it doesn't measure the IPv6 traffic it is carrying separate from overall Internet traffic, so it doesn't know the rate at which its IPv6 traffic is growing.