World IPv6 Day and Windows

The Internet Assigned Numbers Authority (IANA), the international body responsible for distributing Internet addresses, completed their last allocation of Internet Protocol version 4 (IPv4) address blocks on February 3, 2011 2010.  IPv4 addresses are the "phone numbers" of the Internet and are responsible for identifying computers so they can communicate with each other. IPv4 has around 4 billion addresses. Considering the number of people and businesses that use the Internet, many of whom have multiple Internet devices, it’s easy to see why we’ve run out.

Right now, many households in the United States are given what’s called a “unique” or “public” IPv4 address, like your phone number. You can call people, people can call you, and both parties have unique and routable identifiers. The most immediate effect of a shortage of IPv4 addresses is that Internet Service Providers (ISPs) will have to be more frugal when giving IPv4 addresses to customers. Many households may have to share addresses using network address translators (NATs).

It is critical to understand that IPv4 scarcity shouldn't impact your standard Internet browsing experience in the near-term. However in the long-term, there is concern about the following issues:

  • Large Scale Network Address Translation (LSN) can cause performance and reliability issues, especially in peer-to-peer scenarios. Multiplayer computer games might experience issues.
  • Websites often use IP addresses to locate services relevant to you and your location. An example would be a website automatically finding the pizza place nearest your computer. If many people across disperse geographies are sharing IP addresses, it could make location-aware services very difficult.
  • Many security tools used to keep websites safe from denial of service attacks use IP addresses to identify and analyze attacks. As IPv4 scarcity worsens, it is possible that such tools may accidentally disable access to users who are doing nothing wrong.
  • Businesses may face difficulties expanding their online presence, as IPv4 addresses will grow increasingly hard to secure.

The Solution: IPv6

To ensure that these issues are avoided, the Internet is transitioning to the new protocol, Internet Protocol version 6 (IPv6). IPv6 offers a tremendous number of unique addresses – more than a billion per person! We’ll hopefully never run out. Websites and Internet experiences will gradually transition to this new system of communication, and we’re confident that prudent IPv6 migration will ensure that the Internet continues to function and grow. 

On June 8, 2011,,, along with Internet properties from a host of technology companies, will be participating in World IPv6 Day. Most websites today only support IPv4, but on World IPv6 Day participating Internet properties will additionally enable connectivity via IPv6, going "dual-stack.”

This one-day test will enable the Internet community to evaluate the general state of IPv6 preparedness. We want to validate that all of the hardware and software that participates in Internet communication is able to transition smoothly. Laptops, home routers, web servers, network load balancers - there are a lot of things that need to checked for robust and scalable IPv6 support.

Most people won't even notice World IPv6 Day. If you have no IPv6 connectivity, then you will continue to work as before.  If you happen to have IPv6 connectivity, then your connectivity to participating websites will automatically shift over to IPv6.  Here at Windows, we’ve been working on IPv6 support since Windows XP. Windows Vista and Windows 7 are automatically enabled to use IPv6 when it is provided by your ISP and your local network.

IPv6 "Brokenness"

Again, most people will be fine on IPv6 Day. But not necessarily everyone - one thing that we hope to assess and isolate is how many users might lose network connectivity when accessing web sites that support dual IPv4 and IPv6 connectivity, a situation called "IPv6 Brokenness." For example, it is possible that a misconfiguration of your Internet connection can make it hard for your computer and browser to pick the right IP address to contact. This problem might require usage of the IPv6 Brokenness fix that we have made available on Knowledge Base.

Current indications show that this affects less than 0.1% of Internet users. The below test can help you understand whether you will be negatively affected, as well as whether you have IPv6 web access.

It’s important to note that this is a basic test of your computer, its configuration, its local network, and the connectivity provided by your ISP. A negative test at a coffee shop isn't necessarily informative of the experience at your home.  

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Comments (6)
  1. Anonymous says:

    Unfortunately Silverlight isn’t working for me on this page, in any browser, however it does work on the…/visual%20Studio%20Control%20TourTestPage.html test page.

    I have ipv6 through a HE tunnel and all is working as it should be.

  2. Anonymous says:

    I agree with "Some Guy" – even if we have IPv6 enabled on our internet connection, we still can't get to those websites. I'm now looking at alternatives to Forefront TMG, which is a shame, because it's generally a good product.

  3. Railmeat says:

    You have a type-o at the end of the first sentence. IANA allocated their last IPv4 addresses in 2011, not 2010 as you have it above.

  4. Some Guy says:

    "Here at Windows, we’ve been working on IPv6 support since Windows XP…."

    Maybe somebody should tell the ISA/TMG team! It is incredibly frustrating that the OS part of Microsoft is increasingly pushing IPv6 upon us, yet Microsoft's edge gateway product has absolutely zero support for IPv6 and MS won't even give any clues on when they plan to add support.

  5. Cement Sack says:

    ahhhhh… my cpu isnt muscle enough to install Slivertight, I mean Silverwrite (hi ho Silverlite).just no hope for slowpokes, back to NetTamer for DOS.

  6. Todd W says:

    When is the "Product Key" (get key) web page going to be available?

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