Equally significant is the participation by content delivery networks such as Akamai and Limelight. Akamai carries between 20 percent and 30 percent of the Internet's Web traffic on any given day, so its support of IPv6 is a boon for the new protocol. Among Akamai's customers are Apple, Lands' End, Ticketmaster, and Travelocity.
World IPv6 Launch Day is designed to "send enough IPv6 traffic toward content providers to give them confidence that the big access providers are serious about IPv6 and that they should leave it on at their front doors," Daigle says.
Thousands of popular websites have agreed to permanently enable IPv6 by Wednesday. Some, including Facebook, have already turned on IPv6 in production mode. Other World IPv6 Launch Day participants include: consumer-oriented websites such as Bing and Netflix; U.S. government agencies including NASA and the Census Bureau; universities such as Indiana University and the University of Pennsylvania; and network vendors such as Cisco and Check Point.
"World IPv6 Launch Day is a lot larger than people understand," says John Curran, president and CEO of the American Registry for Internet Numbers (ARIN), which doles out IPv4 and IPv6 addresses to network operators in North America. "It's not a small decision for the major content providers to turn on IPv6 and leave it on. From now on, everything they roll out will be on IPv4 and IPv6."
Additionally, four home networking equipment manufacturers -- Cisco, D-Link, NDM Systems and ZyXel Communications -- have agreed to enable IPv6 by default on their home router products by the June 6 deadline.
"There are other home router vendors that are mostly there [with IPv6 support] but for one reason or another haven't gone through the certification process," Daigle says. "We have definitely met our mark in terms of raising awareness with the CPE equipment vendors that IPv6 is real."
Created in 1998 by the Internet Engineering Task Force, IPv6 offers an expanded addressing scheme but is not backward compatible with IPv4. While IPv4 uses 32-bit addresses and can support 4.3 billion devices connected directly to the Internet, IPv6 uses 128-bit addresses and can connect up a virtually unlimited number of devices: 2 to the 128th power.
The Internet needs IPv6 because it is running out of IPv4 address space. The free pool of unassigned IPv4 addresses expired in February 2011, and in April 2011 the Asia-Pacific region ran out of all but a few IPv4 addresses being held in reserve for startups. The European registry is expected to deplete its supply of IPv4 addresses in August, and ARIN next summer.
Network and website operators have two choices when it comes to IPv6: They can either support both protocols in what's called dual-stack mode, or translate between IPv4 and IPv6. Until now, most have been unwilling to make the upgrades required to support IPv6 because IPv6 traffic has been so scarce.
That's expected to change after June 6, when IPv6 traffic is expected to surge. While the most recent estimates are that IPv6 represents less than 0.5 percent of all Internet traffic, participants in World IPv6 Launch Day are hoping to drive IPv6 up to 1 percent or more of Internet traffic.