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Comment by hippyup | Hacker News Reader

I'd love to read an honest post from somebody from Twitter (or GitHub or...) on why they don't support IPv6. Not a shaming thing, it's something I don't quite get. Like I get why an old school bank wouldn't: their infrastructure predates IPv6 and it's a project that has to be financially justified and I can understand how that can be hard. But presumably something like Twitter had an experienced networking team, who surely know all the advantages here and want to somewhat future-proof, build up their infrastructure and they decided not to support IPv6 and I would love to understand the reasoning. Is the extra cost really that high?

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I have no special insight, but it's probably something like "we're working on it, but there are lots of legacy things that expect v4 (including non-obvious like anti-abuse systems) and since all our users have some sort of v4 connectivity it's not urgent".

I am guessing the reasoning goes like this: if we only support IPv4, then it's on all these ISPs with IPv6-to-IPv4 CGNAT to make sure their stuff works properly (and chances are they will notice if it doesn't). But if we support IPv6, it will be on us to make sure people behind those ISPs can still reach us (because hardly anyone goes via this IPv6 route and if it doesn't work it's likely nobody at the ISP will notice).

35% (by number of users) isn't "hardly any".

It should be a greater proportion by bandwidth, cause several huge sites support IPv6 (Netflix, Youtube, Facebook etc), but I can't find figures.

reminds me how MS defended Visual Studio being 32-bit (until VS2022)

Why would they?

- IPv6 is basically an abandoned standard. I wouldn't expect them to support gopher either.

- Residential ISP support for ipv6 is spotty, and anyone who does offer ipv6 offers ipv4 as well.

- When it is supported, ipv6 tends to be substantially slower than ipv4 in practice.

- The addresses are a pain to look at and work with.

- You now have twice as many things to fail.

ipv6 is hardly an abandoned standard, 35% of google users access google over ipv6, and it continues to grow every year.

https://www.google.com/intl/en/ipv6/statistics.html

IPv6 is also usually faster than ipv4 these days, because the overhead of fragmented ipv4 routing is large. In the past it was slower because of lack of understanding/support for it from larger ISPs, and consequently poor routes, or really suboptimal tunneling setups.

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