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A Big Test for New Internet Addresses

Why Google, Facebook, and others are taking part in World IPv6 Day this week.

What is World IPv6 Day?

At 8 p.m. EST on Tuesday, more than 300 organizations, including Google, Facebook, and Yahoo, will test a new way of routing information around the Internet: Internet Protocol version 6 (IPv6). Though the test run will only last 24 hours, participants may learn valuable lessons about how transitioning to IPv6 could affect their sites and their users. Spearheaded by the Internet Society (ISOC), World IPv6 Day is an international, coordinated effort to test this transition. ISOC hopes the effort will also encourage other organizations to adopt IPv6.

What is IPv6?

Each URL has its own Internet Protocol (IP) address. When you type a URL into a browser, a domain name server provides the corresponding IP address. (The IP address for is IP addresses are assigned to devices such as Web servers, PCs, cell phones, and printers so that these devices can be located and contacted. IPv6 enables many more devices to connect over the Internet.

Safari, Internet Explorer, Chrome, and Firefox browsers support IPv6 and have done so for several years, but some devices, including many popular home routers, aren’t yet IPv6-enabled. Devices released as recently as February lack IPv6 support, and some devices need firmware updates to access IPv6-enabled sites.

Why is IPv6 needed?

The Internet has simply outgrown IPv4—the last few addresses were allotted this past February. IPv4 uses 32-bit addresses, which allow about 4.3 billion unique addresses. IPv6 uses 128-bit addresses, which make possible around 340 trillion trillion trillion unique addresses.

Some unused IPv4 addresses still exist, but they have been claimed by large companies and organizations. Other IPv4 addresses have been pooled by five regional Internet registries (RIRs) worldwide. While these can be reassigned, the process is expensive and akin to treading water as the IPv6 transition approaches.

How will participants enable IPv6?

Participants will run IPv4 and IPv6 simultaneously, by “stacking” two types of address records—“A” records and “AAAA” (or Quad-A) records. The A records pair an IPv4 address with a domain name so that, for instance, a user who types into a browser is taken to the correct IP address. Quad-A records do the same, but with IPv6 addresses.

Google has been running IPv6 for several years, but on different URLs ( and By stacking A and Quad-A records, the URL will access both IPv6 and IPv4 versions of the home page. Users who can’t connect to the IPv6 site will be redirected to the IPv4 site.

One potential technical challenge is “IPv6 brokenness”: problems in IPv6 connectivity that prevent users from accessing websites using the newer protocol. When a website such as Google runs two versions of its site for IPv4 and IPv6, it can’t properly monitor for brokenness, because users must specifically type in the IPv6 URL to access it. On World IPv6 Day, traffic will be automatically directed to the IPv6 version, which will highlight brokenness and help organizations fix problems.

Global network: A map of the 2005 Internet shows IPv4 addresses connected by colored lines. The different colors represent domain types such as .com, .net, .gov, and .jp.

How will this affect you?

You probably won’t notice any difference. ISOC estimates that only 0.05 percent of users will have difficulty accessing websites such as Facebook, Google, or Yahoo on World IPv6 Day. For those unlucky few, the problem may lie with incompatible browsers, routers, or operating systems. Home networks, says ISOC, are likely to cause most connectivity problems. Internet service providers (ISPs) generally have not provided IPv6-capable routers, partly because demand simply hasn’t surfaced.

ISOC recommends that users prepare for World IPv6 Day by testing their connectivity via this link. The test tells users whether their browsers are capable of accessing the IPv6 Internet and whether they should anticipate trouble during World IPv6 Day. To further minimize problems, ISOC also urges users to keep current with browser, operating system, and firmware updates, especially for routers and other network equipment.

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