Feature In the early 1990s, internetworking wonks realized the world was not many years away from running out of Internet Protocol version 4 (IPv4) addresses, the numbers needed to identify any device connected to the public internet. Noting booming interest in the internet, the internet community went looking for ways to avoid an IP address shortage that many feared would harm technology adoption and therefore the global economy.
A possible fix arrived in December 1995 in the form of 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.
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.
Yet according to data from Google, the Asia Pacific Network Information Center (APNIC), and 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.
"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.
"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 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."
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