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Still Waiting for IPv6

It’s now been a decade since the world officially ran out of blocks of IP addresses. In early 2011 the Internet Assigned Numbers Authority (IANA) announced that it had allocated the last block of IPv4 addresses and warned ISPs to start using the new IPv6 addresses. But here we are a decade later and not one of my clients has converted to IPv6.

Networks widely use IP addresses for devices in the network. Every cellphone, computer, network router, and modem is assigned an IP address so that ISPs can route traffic to the right device. The world adopted IPv4 in 1982. This is a 32-bit address and provided almost 4.3 billion IP addresses. That was enough addresses until 2011. IPv6 uses a 128-bit IP address. This provides for 3.4 trillion trillion IP addresses, which ought to carry mankind for centuries to come. Like most of us, I hadn’t thought about this in a long time and recently went to look to see how much of the world has converted to IPv6.

At the end of 2020, around 30% of all web traffic was being routed using IPv6. A lot of the biggest US ISPs have converted to IPv6 inside of networks. At the end of 2020, Comcast had converted 74% of its traffic to IPv6; Charter was at 54%. In the cellular world, both Verizon and AT&T are routing over 80% of traffic on IPv6 while T-Mobile is close to 100%. Around the world, some of the biggest ISPs have converted to IPv6. India leads the world with over 62% countrywide adoption at the end of 2020, with the US in fourth at over 47% adoption.

But the big caveat with the above statistics is that many big ISPs are using IPv6 inside the networks but are still communicating with the outside world using IPv4. After all of the alarms were sounded in 2011, why haven’t we made the transition?

First, carriers have gotten clever in finding ways to preserve IPv4 IP addresses. For example, small ISPs and corporations are using a single external IP address to identify the entire network. This allows for the assignment of imaginary IP addresses inside the network to reach individual customers and devices, much like CLECs have reduced the number of telephone numbers needed by switching internally with imaginary numbers.

There is an extra cost for any ISP that wants to convert to IPv6 fully. IPv6 is not backward compatible with IPv4, and any company that wants to route externally with IPv6 needs to maintain what is called a dual-stack, meaning that every transaction in and out of the network has to route using both protocols. This adds expense but, more importantly, slows down the routing.

It’s also impossible to convert a network to IPv6 until all devices using the network are IPv6 compatible. This becomes less and less of an issue every year, but every ISP network still has customers and devices on the network that are not IPv6 compatible. Those customers still using a 12-year old WiFi router would go dead with a full conversion to IPv6. This is one of the primary reasons that the big ISPs and cellular carriers aren’t at 100% IPv6. There are still a million folks using old flip phones that can’t be addressed with IPv6.

There is a definite cost for not converting to IPv6. There is a grey market for buying IPv4 IP addresses, and the cost per IP address has climbed in recent years. The typical price to buy an IPv4 address ranged from $24 to $29 during 2020. With all of the grant money being handed out, I expect the creation of a number of new ISPs in the next year. Many of them are going to be surprised that they need to spend that much to get IP addresses.

The main reason that the conversion hasn’t happened is that nobody is pushing it. The world keeps functioning using IPv4, and no ISP feels threatened by not considering the conversion. The first small ISPs that take the plunge to IPv6 will pay the price of being first with the technology—and nobody wants to be that guinea pig. Network purists everywhere are somewhat disgusted that their employers won’t take the big plunge—but even a decade after we ran out of IP numbers, it’s still not the right time to tackle the conversion.

I have no idea what will finally set off a rush to convert because it inevitably will happen. But until then, this will be a topic that you’ll barely hear about.

By Doug Dawson, President at CCG Consulting

Dawson has worked in the telecom industry since 1978 and has both a consulting and operational background. He and CCG specialize in helping clients launch new broadband markets, develop new products, and finance new ventures.

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Not a grey market Mike Burns  –  May 7, 2021 3:15 PM

Thanks for the article but I resist the colorization of the Ipv4 transfer market as “grey”, which implies unauthorized transfers. On the contrary, buyers of these increasingly expensive assets uniformly insist on their registration in one of the authoritative Whois databases run by the five Regional Internet Registries. These RIRs record the transfers publicly and require that the transfers be both legally and policy-compliant.  There is nothing shady about the market that turns it grey, and many of the world’s largest companies openly participate in it.

I think the big driver will be Todd Knarr  –  May 8, 2021 3:13 AM

I think the big driver will be when the largest providers (AWS, Azure, Google, Akamai, CloudFlare, etc.) find it hard enough and expensive enough to acquire public IPv4 address space that they start charging customers extra for IPv4 addresses on instances. When it starts impacting budgets, that’s going to be the “oh crap” moment for companies.

Refreshing Perspectives Abraham Chen  –  May 12, 2021 3:03 AM

Mr. Dawson:

0) Thanks for your unique observations.

1) The two comments so far represent the “main stream” opinions and positions. However, since our team ventured into this space by accident from telecom background a few years ago, we have come upon many aspects that may resonant with your thoughts. I will share a couple to start with.

2) In terms of the IPv4 resale market referenced by the comments, one puzzling situation is that most of the available IPv4 addresses appear to have been gobbled up through auction events by businesses that have been promoting IPv6. For example, you can Google search this subject and will come up with results like:



It is hard to visualize the rationale behind.

3) In terms of the IPv6 web traffic mentioned in your article, what you found probably is the equipment “Adoption Rate”. It is quite different from the actual Internet “Traffic Volume”. For example, the best that Google has been reporting is only up to roughly 32.5%. Even such appears to have benefited by the COVID-19 forcing more residential usage of the Internet:


4) If you look closer to more general situations, the most consistent data on this topic is from AMS-IX (AMSterdam Internet eXchange) which gives an even lower number of less than 4%. Note that because the peering arrangement among ISPs is more mature for IPv4 than IPv6, the percentage of IPv6 diverted into IXs should be higher than that of IPv4.


5) The questions that you posted at the closing are quite involved. I would bring your attention to an overview about our work, “Revamp the Internet”. It references provide additional discoveries through our study. I will be glad to dig into the details if you are so inclined.



Abe (2021-05-11 23:02 EDT)

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