IPv6 just turned 30 and still hasn’t taken over the world, but don't call it a failure
- Reference: 1767186072
- News link: https://www.theregister.co.uk/2025/12/31/ipv6_at_30/
- Source link:
A possible fix arrived in December 1995 in the form of [1]RFC 1883 , the first definition of IPv6, the planned successor to IPv4.
The most important change from IPv4 to IPv6 was moving from 32-bit to 128-bit addresses, a decision that increased the available pool of IP addresses from around 4.3 billion to over 340 undecillion – a 39-digit number. IPv6 was therefore thought to have future-proofed the internet, because nobody could imagine humanity would ever need more than a handful of undecillion IP addresses, never mind the entire range available under IPv6.
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As billions of devices and people came online, first using PCs and then wielding smartphones, conventional wisdom assumed that network operators would move to IPv6 rather than persist with IPv4.
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Yet according to data from [5]Google , [6]the Asia Pacific Network Information Center (APNIC) , and [7]Cloudflare , less than half of all netizens use IPv6 today.
To understand why, know that IPv6 also suggested other, rather modest, changes to the way networks operate.
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"IPv6 was an extremely conservative protocol that changed as little as possible," APNIC chief scientist Geoff Huston told The Register . "It was a classic case of mis-design by committee."
And that notional committee made one more critical choice: IPv6 was not backward-compatible with IPv4, meaning users had to choose one or the other – or decide to run both in parallel.
For many, the decision of which protocol to use was easy because IPv6 didn't add features that represented major improvements.
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"One big surprise to me was how few features went into IPv6 in the end, aside from the massive expansion of address space," said Bruce Davie, a veteran computer scientist recently honored with a [10]lifetime achievement award by the Association for Computing Machinery's Special Interest Group on Data Communications, which lauded him for "fundamental contributions in networking systems through design, standardization, and commercialization of network protocols and systems."
Davie said many of the security, plug-and-play, and quality of service features that didn't make it into IPv6 were eventually implemented in IPv4, further reducing the incentive to adopt the new protocol. "Given the small amount of new functionality in v6, it's not so surprising that deployment has been a 30 year struggle," he said.
Another innovation that meant IPv6 made less sense was network address translation (NAT), which allows many devices to share a single public IPv4 address. NAT meant IPv4 network operators could connect thousands of devices with a single IP address, meaning their existing IP addresses became more useful.
"These solutions were relatively easy to deploy, aligned with existing expertise, and avoided large-scale infrastructure changes," said Alvaro Vives, manager of the learning and development team at RIPE NCC, the regional internet registry for 76 nations across Europe, the Middle East, and Central Asia.
Because NAT stalled IPv6 adoption, vendors didn't rally behind the new protocol.
"Migration costs, complexity, and training requirements remain high, while short-term ROI is low," Gartner distinguished VP analyst Andrew Lerner told The Register . "Performance parity across applications and devices is inconsistent, and some organizations even disable IPv6 for better performance. Lack of dual-stack support in legacy infrastructure is another barrier," he added.
A misunderstood protocol
While IPv6 didn't take off as expected, it's not fair to say it failed.
"IPv6 wasn't about turning IPv4 off, but about ensuring the internet could continue to grow without breaking," said John Curran, president and CEO of the American Registry for Internet Numbers (ARIN).
"In fact, IPv4's continued viability is largely because IPv6 absorbed that growth pressure elsewhere – particularly in mobile, broadband, and cloud environments," he added. "In that sense, IPv6 succeeded where it was needed most, and must be regarded as a success."
RIPE NCC's Alvaro Vives agrees. "What IPv6 got right was its long-term design," he told The Register . "It provides a vast address space that allows networks to be planned more simply and consistently. This has enabled innovation, from large mobile networks to the Internet of Things and advanced routing techniques such as Segment Routing over IPv6."
[11]Unofficial IETF draft calls for grant of five nonillion IPv6 addresses to ham radio operators
[12]IETF Draft suggests making IPv6 standard on DNS resolvers - partly to destroy IPv4
[13]China's IPv6 adoption takes a decent leap forward, especially on fixed networks
[14]Asia reaches 50 percent IPv6 capability and leads the world in user numbers
Gartner's Lerner thinks the time has come for organizations to develop detailed IPv6 migration plans.
"Validate application compatibility, and ensure new infrastructure supports IPv6," he advised. "Pilot deployments and lab testing with DNS64/NAT64 are recommended. Over time, IPv6 adoption will accelerate as private IPv4 space depletes and cloud providers introduce pricing models that favor IPv6."
APNIC's Huston, however, thinks that IPv6 has become less relevant to the wider internet.
"I would argue that we actually found a far better outcome along the way," he told The Register . "NATS forced us to think about network architectures in an entirely different way."
That new way is encapsulated in a new technology called Quick UDP Internet Connections (QUIC), that doesn't require client devices to always have access to a public IP address.
"We are proving to ourselves that clients don't need permanent assignment of IP address, which makes the client side of network far cheaper, more flexible, and scalable," he said.
Huston thinks IPv6 has also become less relevant to servers.
"These days the Domain Name Service (DNS) is the service selector, not the IP address," Huston told The Register . "The entire security framework of today's Internet is name based and the world of authentication and channel encryption is based on service names, not IP addresses."
"So folk use IPv6 these days based on cost: If the cost of obtaining more IPv4 addresses to fuel bigger NATs is too high, then they deploy IPv6. Not because it's better, but if they are confident that they can work around IPv6's weaknesses then in a largely name based world there is no real issue in using one addressing protocol or another as the transport underlay."
But there are plenty of organizations that still see a need for IPv6. [15]Huawei sought 2.56 decillion IPv6 addresses and Starlink appears to have acquired [16]150 sextillion , which is helping to [17]push more countries past 50 percent IPv6 adoption. ®
Get our [18]Tech Resources
[1] https://datatracker.ietf.org/doc/html/rfc1883
[2] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_onprem/networks&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=2&c=2aVVWrXTX7jwD_MtPnvbADwAAAIQ&t=ct%3Dns%26unitnum%3D2%26raptor%3Dcondor%26pos%3Dtop%26test%3D0
[3] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_onprem/networks&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=4&c=44aVVWrXTX7jwD_MtPnvbADwAAAIQ&t=ct%3Dns%26unitnum%3D4%26raptor%3Dfalcon%26pos%3Dmid%26test%3D0
[4] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_onprem/networks&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=3&c=33aVVWrXTX7jwD_MtPnvbADwAAAIQ&t=ct%3Dns%26unitnum%3D3%26raptor%3Deagle%26pos%3Dmid%26test%3D0
[5] https://www.google.com/intl/en/ipv6/statistics.html#tab=ipv6-adoption
[6] https://stats.labs.apnic.net/ipv6/XA
[7] https://radar.cloudflare.com/adoption-and-usage
[8] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_onprem/networks&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=4&c=44aVVWrXTX7jwD_MtPnvbADwAAAIQ&t=ct%3Dns%26unitnum%3D4%26raptor%3Dfalcon%26pos%3Dmid%26test%3D0
[9] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_onprem/networks&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=3&c=33aVVWrXTX7jwD_MtPnvbADwAAAIQ&t=ct%3Dns%26unitnum%3D3%26raptor%3Deagle%26pos%3Dmid%26test%3D0
[10] https://www.sigcomm.org/awards/sigcomm-award-recipients
[11] https://www.theregister.com/2025/12/02/ham_radio_ipv6_ietf_draft/
[12] https://www.theregister.com/2025/08/20/ietf_dnsop_3901bis_ipv4_ipv6/
[13] https://www.theregister.com/2025/08/04/asia_in_brief/
[14] https://www.theregister.com/2025/04/23/apnic_half_ipv6_capable/
[15] https://www.theregister.com/2024/12/06/apnic_huawei_ipv6/
[16] https://www.theregister.com/2025/10/29/nded/
[17] https://www.theregister.com/2025/06/27/ipv6_adoption_statistics/
[18] https://whitepapers.theregister.com/
Re: The real reason nobody wants to use it
My god you've basically typed my exact intended comment word for word....
Re: The real reason nobody wants to use it
Amen. IPv6 is hard to read.
I propose IPv5: an additional dotted quad. That would have added 256 * 4 billion IPs. Instead we have this utterly cumbersome collection of colons. Even the word 'colon' takes up an extra syllable than 'dot'.
Re: The real reason nobody wants to use it
Yeah, two dotted quads, like it. But you'd mostly only need one at a time, which would be even better, if it was sent via a service which used the other. Now that really would be impossible to dislodge. You could call it, oh, I dunno - NAT or something.
Re: The real reason nobody wants to use it
If only they'd just added a couple more bytes to the address and left it with room to add more as needed
I read somewhere that the committee looking at the successor to IPv4 ruled out variable address lengths as it hurt router performance.
Re: The real reason nobody wants to use it
That along with variable headers, were things ISO OSI CLNS suffered from.
Re: The real reason nobody wants to use it
But also... they did! How many bits do you think there are in "2001:db8:a:1::2"? Sure, there's room to expand to 128 bits in there but in terms of actual used bits it's about the same as the 64 bits you end up with in v4 from effectively having two v4 addresses for every machine. (Or worse, in the case of CGNAT or businesses that remap RFC1918 because they had clashes, where there are more v4 addresses involved.)
I propose IPv5: an additional dotted quad
Adding any number of bits at all requires doing all the work v6 is doing. If you're going to bother, you might as well add enough to avoid needing to do it all over again immediately afterwards.
Re: The real reason nobody wants to use it
>> Adding any number of bits at all requires doing all the work v6 is doing. If you're going to bother, you might as well add enough to avoid needing to do it all over again immediately afterwards.
All the work? I don't think so. Adding one extra dot is a lot less work, and a lot easier to understand.
Re: The real reason nobody wants to use it
The implementation work, getting equipment and software to handle it, getting addresses assigned, getting international routing stable, is all the same. That's the work that's noticeably hard and expensive, whereas the difficulty reading out a string of digits is much smaller if it's relevant at all. What part, other than your memorization or reading, do you think would have been easier with 40-bit instead of 128-bit addresses?
Re: The real reason nobody wants to use it
I'm sure with a bit of creativity the optional headers in v4 could have been made to carry additional address octets. The argument against that is always about speed of routing but If you only use the extra address depth within private networks then that problem is greatly reduced because the core routers would never even look at the additional address depth.
That way instead of my ISP giving me a /29, which is an extremely wasteful way of letting me have 2 or 3 public facing servers, they give me a /32 (or a /40 or a /48) and I figure it out from there on down. Cloud providers could put literally thousands of servers behind each traditional v4 address whilst still having them all directly addressable. Hell, they could even charge more for putting you higher up in the routing strata.
Rule 101 about getting people to migrate to Shiny New Thing is make it completely backwards compatible with Crappy Old Thing so nothing needs to change on day one. I've used v4 almost my entire adult life but I expect to go to my grave without ever touching v6.
disable it
Backwards compatibility
And that notional committee made one more critical choice: IPv6 was not backward-compatible with IPv4, meaning users had to choose one or the other – or decide to run both in parallel.
Uh... what? It is backwards compatible with v4.
Did you mean that they made the choice for v4 to not be forwards compatible? Because that was v4's design committee, not v6's. It's a bit unfair to blame them for decisions made twenty years beforehand by a completely different set of people, isn't it?
Re: Backwards compatibility
Extending things with new capabilities that were not intended to be extended in a seamless fashion is the hallmark of sucessful standards engineering.
Ipv4 NAT achieved this and won.
Re: Backwards compatibility
Except it doesn't actually fix the problem, it just extends life support for v4 to buy us more time to migrate to something that does. I'll grant that it's done a surprisingly decent job of that but it's still just buying time, and at the cost of causing problems of its own.
"These days the Domain Name Service (DNS) is the service selector, not the IP address," Huston told The Register. "The entire security framework of today's Internet is name based and the world of authentication and channel encryption is based on service names, not IP addresses."
My reaction to that statement:
It’s not DNS
There’s no way it’s DNS
It was DNS
IP 42
is how long we'll have to wait for the answer...
The real reason nobody wants to use it
... is that it's easy to remember and read out a dotted quad but essentially impossible to remember or speak ff:12:34:56:78:89:0a:ff ... and it probably really is that simple.
If only they'd just added a couple more bytes to the address and left it with room to add more as needed.