Industry observers say YouTube appeared to be supporting IPv6 in production mode, as opposed to running a test of the next-generation internet protocol.
"On Thursday, midday California time, we saw a large amount of inbound IPv6 traffic, which we knew came from Google," says Martin Levy, Director of IPv6 Strategy at Hurricane Electric, a US ISP that runs one of the world's largest IPv6 backbone networks.
"IPv6 traffic came into ISPs from all over the world when Google turned up its IPv6 traffic on YouTube," Levy says.
"IPv6 is being supported at many different Google data centres. We're talking about a traffic spike that is 30-to-1 type ratios. In other words, 30 times more IPv6 traffic is coming out of Google's data centres than before."
Levy says the YouTube IPv6 traffic appears to be production-quality traffic because it has remained steady since last Thursday and is following normal usage patterns.
"This IPv6 traffic is mimicking classic end-user bandwidth shaping," Levy says. "It's not machine driven; it's human eyeball driven."
Industry observers hailed YouTube's upgrade as a sign of the growing momentum for IPv6, a long-anticipated replacement for the internet's main communications protocol, which is known as IPv4.
"One of the biggest issues with IPv6 is the chicken-and-egg argument. The fact is that content such as this is being moved over to IPv6," Levy says.
"This is not some IPv6-enabled scientific site... This is the mainstream media."
A growing number of websites such as YouTube are adding support for IPv6 because the internet is running out of IPv4 address space.
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.
Experts predict IPv4 addresses will be gone in 2012. Indeed, the Regional Internet Registries announced in January that less than 10 percent of IPv4 addresses remain unallocated.
John Curran, president and CEO of the American Registry for Internet Numbers (arin), is urging Websites like YouTube to add IPv6 support.
ARIN doles out IPv4 and IPv6 addresses to network operators including ISPs, government agencies and corporations in North America.
Google is one of the internet's most aggressive adopters of IPv6.
Google already supports IPv6 with its Search, Alerts, Docs, Finance, Gmail, Health, iGoogle, News, Reader, Picasa, Maps, Wave, Chrome and Android products.
Google engineers said in November that adding IPv6 to its YouTube site was the top priority of its IPv6 development team.
The engineers say IPv6 deployment is not as difficult nor is it as expensive as they thought it would be.