What is IPv6, and why is adoption taking so long?

IPv6 has been in the works since 1998 to address the shortfall of IP addresses available under IPv4, yet despite its efficiency and security advantages, enterprise uptake is slow

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For the most part the dire warnings about running out of internet addresses have ceased because, slowly but surely, migration from the world of Internet Protocol Version 4 (IPv4) to IPv6 has begun, and software is in place to prevent the address apocalypse that many were predicting.

But before we see where are and where we’re going with IPv6, let’s go back to the early days of internet addressing.

What is IPv6 and why is it important?

IPv6 is the latest version of the Internet Protocol, which identifies devices across the internet so they can be located. Every device that uses the internet is identified through its own IP address in order for internet communication to work. In that respect, it’s just like the street addresses and zip codes you need to know in order to mail a letter.

The previous version, IPv4, uses a 32-bit addressing scheme to support 4.3 billion devices, which was thought to be enough at the time it was implemented. However, with the growth of the internet, personal computers, smartphones and now Internet of Things, it became clear that the world needed more addresses.

Fortunately, the Internet Engineering Task Force (IETF) recognized this nearly 25 years ago. In 1998, it created IPv6, which instead uses 128-bit addressing to support approximately 340 trillion trillion (or 2 to the 128th power). Instead of the IPv4 address method of four sets of one- to three-digit numbers, IPv6 uses eight groups of four hexadecimal digits, separated by colons.

What are the benefits of IPv6?

In its work, the IETF not only added more address space, it included enhancements to IPv6 compared with IPv4. The IPv6 protocol can handle packets more efficiently, improve performance and increase security. It enables internet service providers to reduce the size of their routing tables by making them more hierarchical.

What do IPv6 addresses look like

You're probably familiar with IPv4 addresses, which are written in four parts separated by dots like this: 45.48.241.198. Each part written in conventional Base 10 numerals represents an eight-bit binary number from 0 to 255 (000000 to 1111111, written in binary).

An IPv6 address looks like this: 2620:cc:8000:1c82:544c:cc2e:f2fa:5a9b.  Instead of four numbers, there are eight, and they’re separated by colons rather than commas. And yes, they are all numbers. There are letters in there because IPv6 addresses are written in hexadecimal (Base 16) notation, which means 16 different symbols are required to uniquely represent the Base 10 numbers 1-16. The ones used are numerals 0-9 plus letters A-F. Each of these numbers represents a 16-bit binary number ranging from 000000000000 to 11111111111111.

Network address translation (NAT) and IPv6

Adoption of IPv6 has been delayed in part due to network address translation (NAT), which takes private IP addresses and turns them into public IP addresses. That way a corporate machine with a private IP address can send and receive packets from machines located outside the private network that have public IP addresses.

Without NAT, large corporations with thousands or tens of thousands of computers would devour enormous quantities of public IPv4 addresses if they wanted to communicate with the outside world. But those IPv4 addresses are limited and nearing exhaustion to the point of having to be rationed.

NAT helps alleviate the problem. With NAT, thousands of privately addressed computers can be presented to the public internet by a NAT machine such as a firewall or router.

The way NAT works is when a corporate computer with a private IP address sends a packet to a public IP address outside the corporate network, it first goes to the NAT device. The NAT notes the packet’s source and destination addresses in a translation table.

The NAT changes the source address of the packet to the public-facing address of the NAT device and sends it along to the external destination. When a packet replies, the NAT translates the destination address to the private IP address of the computer that initiated the communication. This can be done so that a single public IP address can represent multiple privately addressed computers.

Who is deploying IPv6?

As of March 2022, according to Google, the IPv6 adoption rate globally is around 34%, but in the U.S. it’s at about 46%.

Carrier networks and ISPs have been the first group to start deploying IPv6 on their networks, with mobile networks leading the charge. For example, T-Mobile USA has more than 90% of its traffic going over IPv6 as of March 2002, with Verizon Wireless close behind at 82.63%. Comcast and AT&T have their networks at 70% and 73%, respectively, according to the industry group World Ipv6 Launch. The past few years have seen broader IPv6 adoption in Asia and South America, with India currently standing at about 62% and the Indian wireless carrier Reliance Jio Infocomm topping World Ipv6 Launch's network adoption charts with more than 93%.

Just under 30% of the Alexa Top 1000 websites are currently reachable over IPv6, World IPv6 Launch says, a number that has remained stubbornly stagnant over recent years.

Enterprises are trailing in deployment. For instance, a RIPE Labs report on IPv6 adoption noted that U.S. use of IPv6 actually dropped from 2020 to 2021, and speculated that the reason might be that people who had worked at home early in the COVID-19 pandemic were returning to the office and IPv4-based corporate networks.

Complexity, costs, and time needed to complete a transition are all reasons that corporate IT is gun-shy over migration projects. In addition, many medium-sized and small enterprises outsource their networking needs to service providers, who themselves don't have a strong incentive to migrate in the absence of a push from their customers.

When will more deployments occur?

Enterprise resistance to large-scale IPv6 migration is slowing adoption overall. Patrick Hunter, Charter Communications' director of IT enterprise network and telecom, lays out many of the factors in play, noting that while most network administrators know migration is inevitable, nobody wants to necessarily wants to be a pioneer if the risk is causing problems for their own networks and applications.

As he puts it, admins have the attitude of "I’m not going to break things and make life difficult just because some insist everyone should hurry to the new protocol." Not all companies are resisting—Amazon is migrating its serverless and container AWS workloads to IPv6. But inertia, plus the fact that, as noted, widespread NAT use has staved off an IPv4 apocalypse, have reduced the incentives to make the move. The transition may not be complete until 2030 or later.

Nevertheless, as the price of IPv4 addresses begin to drop, the Internet Society suggests that enterprises sell off their existing IPv4 addresses to help fund IPv6 deployment. The Massachusetts Institute of Technology has done this, according to a note posted on GitHub. The university concluded that 8 million of its IPv4 addresses were “excess” and could be sold without impacting current or future needs since it also holds 20 nonillion IPv6 addresses. (A nonillion is the numeral one followed by 30 zeroes.)

In addition, as more deployments occur, more companies will start charging for the use of IPv4 addresses, while providing IPv6 services for free. UK-based ISP Mythic Beasts says “IPv6 connectivity comes as standard,” while “IPv4 connectivity is an optional extra.”

Pushing for a faster transition will take government action, though many Western governments don't have this on their to-do list. One country moving to IPv6 in a big way is China. In 2021, the Cyberspace Administration of China unveiled an ambitious roadmap, aiming to have 800 million active IPv6 users by the end of 2025.

When will IPv4 be “shut off”?

Most of the world “ran out” of new IPv4 addresses between 2011 and 2018 – but we won’t completely be out of them as IPv4 addresses get sold and re-used, and any leftover addresses will be used for IPv6 transitions.

There’s no official switch-off date, so people shouldn’t be worried that their internet access will suddenly go away one day. As more networks transition, more content sites support IPv6 and more end users upgrade their equipment for IPv6 capabilities, the world will slowly move away from IPv4.

Why is there no IPv5?

There was an IPv5 that was also known as Internet Stream Protocol, abbreviated simply as ST. It was designed for connection-oriented communications across IP networks with the intent of supporting voice and video.

It was successful at that task, and was used experimentally. One shortcoming that undermined its popular use was its 32-bit address scheme – the same scheme used by IPv4. As a result, it had the same problem that IPv4 had – a limited number of possible IP addresses. That led to the development and eventual adoption of IPv6. Even though IPv5 was never adopted publicly, it had used up the name IPv5.

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