The most popular Web sites are under increasing pressure to add support for IPv6, a long-anticipated upgrade to IPv4, the Internet's main communications protocol.

IPv6: The Essential Guide  

That pressure was ratcheted up a notch this week, with the news that Google has IPv6-enabed YouTube, its video streaming site. Google already offers IPv6 access on its main search service and many other popular Web services. (For details on how seven of the largest sites are doing, see our list below.)

IPv6-enabled Web content is "one of the things we need to have," says Timothy Winters, a senior manager at the University of New Hampshire Interoperability Laboratory (UNH-IOL), which provides IPv6 product testing. "As all of these LTE and wireless broadband networks go to IPv6, the content providers have no choice but to create mobile content and make it IPv6 aware."

Winters said Comcast's recent announcement that it is running IPv6 trials is another sign that it's time for popular Web sites to support IPv6.

"We are starting to see these major Web sites embracing IPv6," Winters says, pointing out that Netflix demonstrated IPv6 access last year. "It's pretty easy to turn a basic Web server on to support IPv6…The biggest problem is the client software. That's why a lot of Web sites create separate IPv6 sites like Google and Netflix where you go if you have an IPv6 address because they don't want the site to [be slow.]"

For example, eBay is running IPv6 in its lab and plans to deploy the new protocol on its internal corporate network this year. The public-facing eBay Web site will be upgraded for what's called dual-stack IPv4 and IPv6 access in 2011.

"IPv6 is the next generation. It's the future of the Internet, at least for those people who want to see the Internet continue to grow and continue to be part of the infrastructure," says Peter Manzella, senior director of global network services for eBay. "We are obviously on board with that."

Manzella says eBay's network services team has experienced no problems with its IPv6 testing so far.

"We do not expect any difficulties," he says. "We need to understand it. We need to make sure when we transition to it, it's seamless. … There are security concerns that we need to test … .We need to take the precautions that are necessary to ensure our community has a safe experience on the site."

IPv6 solves the problem that ISPs and other network operators face as the Internet runs out of IPv4 addresses, which is expected to happen in 2012. Less than 10% of IPv4 addresses remain unallocated as of January.

IPv4 uses 32-bit addresses and can support approximately 4.3 billion individually addressable devices on the Internet. IPv6, on the other hand, uses 128-bit addresses and can support so many devices that only a mathematical expression -- 2 to the 128th power -- can quantify its size.

John Curran, president and CEO of the American Registry for Internet Numbers, is urging Web sites to enable IPv6 access to their Web sites by Jan. 1, 2012. ARIN doles out IPv4 and IPv6 address space to ISPs in North America.