Three years ago, on 25 November 2019, at 15:35 (UTC+1), the world ran out of IPv4 addresses....and nothing happened.
RIPE NCC (the institution overseeing global internet resources) have announced that they made a final IPv4 allocationfrom the last remaining addresses in their available pool.
This was supposed to be a big deal. It was the end of an era. Or so we thought.
The truth is, the IPv4 address depletion was not nearly as catastrophic as many thought it would be.
The birth of IPv6
The top-level exhaustion occurred as far as 31 January 2011. That's when the last /8 address blocks were allocated.
So in June 2012, the world-leading Internet service providers (ISPs), home networking equipment manufacturers, and Web companies came together to save the Internet.
The problem they were solving was the impending exhaustion of the IPv4 addresses. IPv4 has only 4.3 billion addresses. You can see how in the world of over 7.5 billion humans and countless internet-connected devices, each requiring a unique IPv4 address to connect to the Internet, that might be a problem.
The solution the industry came up with was to switch to a new version of the Internet Protocol, IPv6, which has over 340 undecillion addresses, or 340,282,366,920,938,463,463,374,607,431,768,211,456 addresses. (That's enough for every person to have 67 million trillion addresses.)
In an inspiring effort, the industry giants have committed to making sure that their products and services would work with both IPv4 and IPv6. This was no small feat, as it required a lot of coordination and hard work. And it will eventually pay off, with a future-proof Internet that can keep growing for many years to come.
By 2019, all five Regional Internet Registries (RIRs) had run out of unallocated address space to hand out to ISPs, who would then distribute it to end users. This should have been the end of IPv4.
Yet, 10 years later, we still haven't transitioned to IPv6. Why?
I can think of several reasons why we haven't transitioned to IPv6 yet:
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CGNAT is working well enough that there is no immediate need to switch.
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IPv6 is not backward-compatible with IPv4.
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Reuse and reallocation of IPv4 addresses prolonged the time before we needed to switch
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NAT provides security benefits that would be lost in a transition to IPv6.
CGNAT is working well enough that there is no incentive to switch.
The solution that was supposed to be temporary, Carrier-Grade NAT (CGN), or Large-Scale NAT (LSN) is working so well that there is no immediate need to switch to IPv6.
In 1994, when the problem of IPv4 exhaustion loomed on the horizon, a new, "temporary" technology was proposed to keep the Internet growing without depleting IP addresses as quickly. To keep the Internet running, a stopgap measure carrier-grade
NAT allows multiple devices on a network to share a single public IPv4 address. It takes a small pool of public IPv4 addresses and shares them among a large number of users on internal network. It does this by translating the private addresses of devices on a network to a single public address and then back again when it receives data from the Internet. It's kind of like an apartment complex where everyone has their own apartment, but they share a single front door (a public IPv4 address). As a result, a single public IPv4 address can be shared among many devices on a local network.
NAT was intended as a temporary fix before a better alternative - the later developed IPv6 - could be implemented. However, this "temporary patch" has been so successful that this stopgap has become a semi-permanent solution lasting for over two decades and counting.
IPv6 is not backward-compatible with IPv4
Many devices only work with IPv4, so a transition would require replacing a lot of hardware.
So to make the transition from IPv4 to IPv6, everyone would need to upgrade their devices and software to be compatible with IPv6. Today, only about 40% of devices are IPv6-compatible. This presents a big challenge for companies that want to transition, as they need to support both IPv4 and IPv6 devices during the transition period.
IPv6 adoption is also not equal worldwide, with some countries trailing behind. This creates a "digital divide" where some users can access certain content and services that others can't. This presents a challenge for companies trying to transition, as they need to support both IPv4 and IPv6 devices during the transition period.
Source: https://www.google.com/intl/en/ipv6/statistics.html#tab=per-country-ipv6-adoption
NAT provides security benefits that would be lost in a transition to IPv6
Another reason NAT has been so successful is that it provides some security benefits. As an unintended consequence, NAT makes it more difficult for attackers to target specific devices on a network.
For example, if an attacker wants to launch a denial of service attack against a web server, they would need to know the public IP address of that server. With NAT, the attacker would only be able to see the router's public IP address and not the IP addresses of devices behind the router. So, to launch an attack, the attacker would need to target the router itself, which is much more difficult.
Reuse and reallocation of IPv4 addresses
Another reason for the delay in transitioning to IPv6 is that there are secondary markets for IPv4 addresses. IP address blocks turned into a commodity.
For example, an ISP might have a /16 address block, which contains 65,536 addresses. But the ISP might only use a small fraction of those addresses - say, 1,000. The rest of the addresses in that block can be sold or leased to other companies. As a result, the same IPv4 address might be used by multiple companies at different times.
ISPs can also reallocate their IPv4 addresses, for example, when a customer with a /24 address block (256 addresses) cancels their service. The ISP can then give that /24 address block to another customer.
This address reuse and reallocation has helped to prolong the time before we need to switch to IPv6.
The bottom line - it works well enough still
Taken together, these factors - the difficulty of transitioning, the need to support both IPv4 and IPv6, the security benefits of NAT, and address reuse and reallocation - have all contributed to a delay in the transition to IPv6.
So while IPv6 will eventually become the new standard, for now, IPv4 is here to stay. It's working well enough. Maybe our kids and grandkids will actually use IPv6 addresses.