What is IPv6?

The time for testing is over, as Facebook, Cisco, Comcast and others will soon permanently enable next-generation internet technology with vastly more elbow room. So what does it all mean?

What began as a 24-hour test a year ago will become business as usual today, as a range of big-name internet companies permanently switch on the next-generation Internet Protocol version 6 (IPv6) networking technology.

And now, there's no turning back.

"IPv6 is being enabled and kept on by more than 1500 websites and ISPs in 22 countries," said Arbor Networks, a company that monitors global internet traffic.

IPv6 has one big improvement over the prevailing IPv4 standard that it's designed to supplant: room to grow. However, moving to IPv6 isn't simple, which is why many organisations on the internet have banded together for a World IPv6 Launch event overseen by standards and advocacy group the Internet Society.

In practice, IPv6 has been gradually arriving on the net already, and there's a long way to go after the event, but today's launch day is a real milestone. Here's a look at some of the issues involved.

Why all the fuss?

The internet is running out of room.

IPv4 was used to describe the network address to almost all smartphones, PCs, servers and internet-enabled refrigerators, so that other devices could exchange data. For example, your computer needs to know the IP address of CNET Australia to read this story, and CNET Australia's server needs to know your computer's IP address in order to send said web pages.

IPv4, though, offers only 4.3 billion addresses — 2 to the power of 32, or 4,294,967,296, to be precise). That may sound like a lot, but there are ever more devices to connect to the internet, and many of the IPv4 addresses are inaccessibly squirreled away by organisations that got large tracts of them earlier in the history of the internet.

The upshot is that the problem called "IPv4 address exhaustion" is real; the pipeline of new ones is emptying out. That's a problem for businesses that want to set up new internet services, or for carriers wanting to sell another few million smartphones.

IPv6 to the rescue! It offers 340 undecillion addresses — 2 to the 128th power, or 340,282,366,920,938,463,463,374,607,431,768,211,456, to be precise.

There's only one problem: upgrading the internet to IPv6 — and that means the entire internet — is expensive, requires a lot of work and is something most of the computing industry has been putting off until absolutely necessary. There are still procrastinators, but its time has now come.

IPv6 addressing

(Credit: FCC)

How real is IPv6?

You've been able to create IPv6 networks since 1999, but there's been little point until relatively recently. Many people didn't have computers, home networking equipment or internet service providers (ISPs) that could reach IPv6 sites on the net, and websites had little incentive to make their sites available over IPv6.

But that's changing now.

Today, somebody with an IPv6 connection will be able to get data from an IPv6 internet site. The fraction of internet traffic will be small, but it will grow fast. Yahoo properties that will become IPv6 enabled today include the main Yahoo website, My Yahoo and OMG.

"For the IPv6-enabled sites, I expect to see roughly half a per cent," said Jason Fesler, Yahoo's IPv6 evangelist. "In a year, in the realm of 10 to 15 per cent."

Through a partnership called Atlas, Arbor Networks scrutinises anonymous data from 253 ISPs, 125 of which carry IPv6 traffic today. Arbor has measured a flow of 10 gigabits per second of IPv6 traffic flowing, said product manager Scott Iekel-Johnson. That's 0.04 per cent of the total internet traffic on Atlas, and 0.09 per cent of the traffic on the IPv6-carrying ISPs, he said.

Hurricane Electric, a networking company that's been pushing IPv6 technology and services for more than a decade, is seeing the evidence that the shift to IPv6 is real. "Hurricane Electric's professional services group has seen a more than five-fold increase in people wanting us to provide courses and consulting to help them plan and deploy IPv6 over the last two months," said Owen DeLong, the company's IPv6 evangelist and director of professional services.

And based on its internet monitoring, Cisco predicts that "there will be 8 billion IPv6-capable fixed and mobile devices in 2016, up from 1 billion in 2011", it said this week. "Globally, 40 per cent of all fixed and mobile networked devices will be IPv6 capable in 2016, up from 10 per cent in 2011."

Cisco fellow Mark Townsley said that IPv6 support is arriving at the two ends of the network connection, and that will push ISPs and other network companies to add their own support, so the IPv6 connection can actually be made.

"On the content side, we're seeing 50, 60 or 70 per cent of content available over IPv6 ... by year end," he said. And though Windows XP doesn't have IPv6 support enabled by default, Townsley said, it'll fade from the scene. "The good news is, while 30 to 40 per cent of PCs ... don't have IPv6 by default, in the next two years that's dropping down to fractional numbers — 1 to 2 per cent." Android and iOS devices, along with newer versions of Windows and OS X, already have IPv6 support.

IPv6 traffic

(Credit: Hurricane Electric)

Do we need this World IPv6 Launch event?

It'll add some pretty high-profile commitments to the transition, making it abundantly clear to laggards that they'd better get with the program. Among the changes coming today:

  • Some ISPs will turn on IPv6 and leave it on, so at least 1 per cent of their customers will have IPv6 access. These ISPs include AT&T, Comcast, Time Warner Cable, Free Telecom, Australia's Internode, KDDI and XS4ALL

  • Home network device makers Cisco and D-Link will enable IPv6 by default for their home network devices; Cisco makes the Linksys line of home routers

  • Google, Microsoft, Facebook and Yahoo will enable IPv6 access to their main websites and keep it available. Yahoo also committed to offer Yahoo Sports, Yahoo Mail and Yahoo Finance over IPv6 in the coming months. Several services are already available over IPv6 today, but people must go to a specific and different web address, such as ipv6.google.com. From launch day, just going to google.com will return results over IPv6, if your device and ISP are IPv6 enabled.

In practice, though, the IPv6 launch — a transition that's been underway for years, and that will take years more to complete — has already begun.

Indeed, even the immediate run-up to the IPv6 launch event has increased IPv6 content and corresponding network traffic, Hurricane Electric statistics have shown.

"The trend leading up to launch day [today] is more likely people turning it on for launch day a little early in order to test and verify things and really be ready for leaving it on as of launch day," DeLong said. "There's no penalty on launch day for having turned it on early, so I think you're seeing people run tests in preparation for launch day. Since they aren't encountering problems when they test, they go ahead and leave the test running."

Can't we just fix IPv4?

There are crutches to ease the problem. The biggest one is sharing a single IP address among several devices. If you have a home Wi-Fi network, chances are it's sharing its IP address with your computers, mobile phones, game consoles, net-connected TVs and set-top boxes, and other network-savvy electronics.

This approach is called network address translation (NAT). It's your Wi-Fi router's job to be the traffic cop that oversees outgoing data sent from all of these devices and directs incoming traffic to the appropriate device.

One real-world analogy to NAT is a street with 10 addresses. When somebody builds a six-unit apartment building at 8 Elm Street, that street address can be shared by the residents of 8A, 8B, 8C, 8D, 8E and 8F Elm Street. Another analogy is phone extensions: a company can have a single phone number that leads to 10,000 extensions for individual employees.

On a grander scale, a similar concept exists called carrier-grade NAT (CGN). This takes place at the ISP level, rather than the house level, and it's a lot more complicated.

Great — with NAT, problem solved, right?

Yes and no. NAT has been a huge help in extending the life of IPv4 while the industry gets its IPv6 act together, but it brings its own problems.

Chief among them is that NAT breaks the ideal network model that a device has an actual address that naturally makes it easy to locate on the net. NAT obscures addresses, which, for some security purposes, can be convenient, but for data transfer is a pain.

Here's how John Curran, chief executive of the American Registry for Internet Numbers (ARIN), put it:

The internet is built on the "end-to-end" principle; that is, the ability of one device to directly reach the other end of the connection. Network address gateways, while functional, do not preserve this property, and as a result some applications have problems working reliably through them. This has been proven in the use of NAT in the home marketplace, which has resulted in numerous workarounds being deployed to make games and always-on internet devices (like cameras and picture frames) work reliably.

Basically, NAT means that there are first-class citizens on the network with their own addresses, and second-class citizens that are harder to reach. That creates a hierarchy in which services must be designed around a relatively small number of central servers, rather than enabling direct communication between any device.

Here's an example that DeLong used to show the shortcomings of NAT in the US:

Today, remote scheduling of a recording on Tivo involves putting the scheduling request into the Tivo website, and Tivo's servers wait for your Tivo to "phone home" and pull down that request, so your Tivo box is constantly having to check in with Tivo central and if your request is coming up in the next few minutes. It might not actually get communicated to the box. (There's generally about a two-hour delay in this process, in my experience).

Without NAT, there's no reason that you couldn't use an app to send that request directly to your own Tivo box without even involving Tivo central. Even if it still goes through Tivo central, they could push the request out to the Tivo box, instead of waiting for the Tivo box to "call in".

Richard Jimmerson, the Internet Society's director for deployment and operationalisation, added that CGN is also likely to add delays called latency in internet communications:

IPv4 address sharing through CGN requires additional devices and software to be placed into use between the user and the content that they interact with on the internet. Early testing has shown that this increases latency times for users, slowing down response times between their home and the content they are consuming. In some cases, this degraded performance will be acceptable to the user, but in other cases it may not. Some latency-sensitive applications — such as video streaming, IP-based voice services and online gaming — may be severely impacted.

So NAT, while useful, is in many ways just a technology to tide people over until IPv6 arrives.

Will there be any trouble today, on launch day?

For a small slice of people, yes, but for the vast majority, no.

Last year's World IPv6 Day detailed that there are problems in a few corner cases, but generally showed that enabling IPv6 services didn't break the internet.

Yahoo, which participated in the test and has gargantuan web traffic, has carefully measured the fraction of its visitors who had problems when IPv6 is enabled. "Weeks before the World IPv6 Day 2011, it was roughly 0.055 per cent," Fesler said. "A week after, that number was down to 0.022 per cent, with a great number of people learning their systems were 'broken' and taking steps to fix it."

However, the problems have been creeping back, even though people might not know it. "Since last year, we've seen a steady rise back towards 0.030 per cent. Since few websites have been running IPv6, these users have had no reason to realise anything was wrong."

What's actually going wrong?

For that small fraction, the problem is often within a particular user's grasp, Fesler said.

Most of the issues are local to the user's computer or the user's home network. The problems may be related to the home wireless router they have — a few early IPv6 implementations did things that were ultimately found to be not in the customer's best interest. Many of these early implementations have updates available.

In other cases, it may be related to the home computer. IPv6 might be enabled in the house, but the firewall installed on the home computer may not be aware of IPv6 (and block the traffic). Or the customer may have enabled specific transitional technology that allows IPv4-only users to have an IPv6 address using public gateways. These public gateways have no service-level agreements; it is often impossible for an end user to know there may be a problem.

Other problems outside of a person's control can crop up as IPv6 and IPv4 coexist side by side, with gateway devices trying to bridge the two. That could show up as slow access to some sites.

For example, a person at home whose ISP has assigned an IPv4 address, could try to reach an IPv4-based website. But the route in between might require IPv6, in which case hardware would have to wrap up the IPv4 data in IPv6, deliver it to the other side, then unwrap it for delivery to the other computer. That would have to be repeated for each packet of data sent in either direction, slowing network performance and increasing complexity.

Do I have a problem?

To see if you're affected, try an IPv6 readiness test site. Yahoo's IPv6 help site offers not just a test, but also steps to fix things.

Japan in particular will have some problems, Yahoo said. That's because some ISPs have deployed IPv6 to let their subscribers access particular services, such as phone and television, that aren't part of the broader internet, Fesler said. Traffic to the regular internet uses IPv4.

That's all well and good — except that the design fools browsers into thinking that IPv6 is available for the internet, when in fact it's only available for a walled garden. That means sluggish web performance as browsers attempting to connect over IPv6 wait before falling back to IPv4. "There is a roughly one-second delay for Windows users before giving up on IPv6 and trying IPv4 instead," Fesler said. "This problem is not just for the connection to the website, but also for connections to get images on the page and other resources needed to fully draw the website."


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