Teredo is one of a handful of protocols used to help IPv6 packets traverse IPv4 networks. Others include 6to4 and 6in4. They use tunneling techniques, such as encapsulating IPv6 packets in IPv4 packets, to get through the routers and other equipment on a network that don't support the new protocol. For example, U.S. cable operator Comcast is introducing dual-stack services, which support both versions of IP, but hasn't yet rolled them out to all its subscribers. Those who don't have the full dual-stack services have to use a transitional protocol to reach an IPv6 resource, according to Scott Iekel-Johnson, a current product manager at Arbor, which provides network security software to Comcast.
Teredo dominates the test results probably because it is included with Microsoft Windows Vista and Windows 7, Labovitz said. If a user is running one of those OSes on a PC, the OS might connect with the IPv6 version of a website if it is available, he said.
Because Teredo and other tunneling protocols use both an IPv4 and an IPv6 address, they don't diminish the need for the older type of address, several experts said. However, they are necessary on the road to IPv6, said Martin Levy, director of IP strategy at Hurricane Electric, an Internet service provider with a focus on IPv6.
"They enable you to take this fundamental step of enabling IPv6 on a content website and know that people can still access it in the transitional time when they are not provided a real IPv6 connection," Levy said. "In order to get from here to there, you have to rely on these. But these technologies are not the 'there.'"
There are some transitional technologies that can help to preserve IPv4 addresses, including carrier-grade network address translation, which lets many endpoints share a single IPv4 address, Levy said. However, this type of address translation has some limits in scaling up, according to some experts.
In addition, the special IPv6 Web pages that users were accessing on Wednesday didn't offer any special features or even higher performance than the IPv4 versions, participants in the event said. In fact, engineers were watching to see whether going to an IPv6 site via one of the tunneling protocols would make the experience worse than normal, according to Labovitz.
Yahoo made the HTML components of its Yahoo.com front page available via IPv6 and made the experience the same as for the IPv4 version, said Yahoo IPv6 Evangelist Jason Fesler. The company does not see IPv6 leading to new user experiences in the future, he said. "IPv6 is just a preservation of what we enjoy today," Fesler said.
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