They have the resources, the expertise and, though they may not realize it, the need -- but it turns out that enterprises are often the ones that don't yet have IPv6.

That's the finding of the Internet Society its latest report on IPv6 deployment, published five years after the organization began a worldwide push to deploy the new addressing protocol and almost 20 years after the protocol was defined.

Around 13 percent of the top one million websites is inviting IPv6 traffic today, it said, citing a Hurricane Electric analysis of data provided by Amazon.com. That figure rises to around 22 percent for the top 1,000 websites.

In 37 countries, IPv6 is used for over 5 percent of internet traffic, according to Google, which bases its estimate on traffic hitting its load-balancers.

In India the figure is over 20 percent. That's largely thanks to mobile network operator Reliance JIO, which uses native IPv6 in its LTE network and accounts for around 70 percent of all India's IPv6 traffic.

One area with massive adoption of IPv6 is the internet of things. "The standards for that are based on IPv6," said Fred Baker, a consultant for the Internet Society and author of the report.

"The bad news in IPv6 deployment is enterprise networks. Residential networks are moving along quite well. Mobile networks are approaching 100 percent utilisation of IPv6, or moving pretty strongly in that direction," Baker said.

In the enterprise, a big brake on deployment of IPv6 -- or anything new, for that matter -- is the installed base.

"They've been running IPv4 for 20, 30, 40 years, and they have something that works. Their inclination tends to be to say, if it isn't broken, why fix it?" he said. "It doesn't solve a problem they think they have, so they don't see a reason to go to the expense and effort."

But there are problems that a move to IPv6 can solve for enterprises, whether they realize they have them or not.

One is network performance. Facebook has found that IPv6 is 15 percent faster on average than IPv4 on U.S. mobile networks, and according to the Asia Pacific Network Information Centre (APNIC) IPv6 seems to mostly have better performance.

As IPv6 deployment increases, the tipping point is approaching at which IPv4 traffic is tunneled over IPv6 rather than the other way around. Past that point, IPv6's performance advantage over IPv4 can only increase.

Another is return on the capital tied up in IPv4 addresses. These addresses are worth around $10 each today, although this is forecast to rise towards a peak in the medium term, as demand from IPv4 hold-outs increases, before falling as they become largely irrelevant post-migration. Enterprises that move before the peak can cover some of their migration costs by selling off their IPv4 addresses.

"A company that holds a Class-B address, which used to be fairly common, would have US$640,000 right there," said Baker.

Businesses with more hosts than IPv4 addresses have to resort to tricks like NAT (network address translation) to share them around. Those most feeling the pinch here are ISPs (internet service providers), which may face additional legal constraints requiring them to be able to identify to law enforcement officers which subscriber held which IP address at a given time. Moving to IPv6 would eliminate the need for a whole layer fo logging.

That's not to say that moving to IPv6 is simple. Businesses need to take it step by step.

"The first thing they have to do is to think about what hardware, what software, what applications they have and do they work with IPv6?" Baker said.



They may find they need to replace some aging equipment, which is a budgetary issue.

Baker used to work at Cisco Systems where, he said, it took about a year of talking with customers about IPv6 deployment to get it into the budget cycle.

Older networking devices are the most likely to need replacing. They're likely to already be causing network managers headaches unrelated to IPv6, though, so they are probably looking for excuses to replace them, he said. That in itself might be enough to push a company to migrate.

When looking for new, IPv6-capable equipment and services, "The first place I would go is wherever I bought the previous one, unless I've had complaints about it. They probably have an upgrade for it," Baker said.

The Internet Society's Technology Programme Manager, Mat Ford, warned not to take "no" for an answer.

"If you have specific vendor that tells you, 'None of our customers are asking for this,' then you can say, 'That's curious: there are a lot of IPv6 deployments out there. Maybe I should ask them what they're using and buy that instead," he said.

Businesses that do make the move to IPv6 rarely migrate everything in one go.

"They do it first with their customer-facing interfaces, email, web, that kind of thing," said Baker. Adding an IPv6 address to the existing IPv4-capable service is often done through a hosting provider such as Akamai, he said. The business needn't take the next step, turning on IPv6 internally, until it needs to perform some other application or network deployment internally.

What generally drives companies to take the final step of turning off IPv4 internally is when they realize they are effectively running two networks.

"Microsoft has recently come to the conclusion that IPv4 is causing a lot of problems and doing dual-stack is more trouble than it's worth," he said.

If nothing else, Baker suggests, enterprises should consider deploying IPv6 at their own pace, while they still have the choice.

Analysts at network operator Swisscom thinks their customer base is going to be mostly IPv6-capable by 2019, according to Baker.

"By 2024, they think there will be a low enough IPv4 density that there won't really be a business case carrying it on."