alt Hacker News> What I don’t understand is why coexistence was so important.
Military, corporate, tech... it isn't. (If your people like flag day migrations. It's… "a choice".) But if you have to explain to an end user why some things work and some don't, you're just f'd.
And note "coexistence" here means that an end host can implement IPv4 and IPv6 at the same time, without them interacting at all. Imagine if you had to choose between IPv4 and IPv6 on your devices, maybe something like "you need a 2nd network card". Can you imagine anyone switching to the less popular protocol?
The article describes coexistence as both dual-stack and connectivity between single-stack IPv6 and single-stack IPv4 host. And that in the autor's opinion all the complexity is in the latter, not in the dual-stack
You raise a good point that we also should't take dual- stack for granted. But I think the more precise question 'why not dual-stack as the only coexistence option' also seems like a good one, and one the article does not explore or even acknowledge