Earlier quoted context omitted.
IPv6 is a recursive WTF. It might _look_ like a conservative expansion of IPv4, but it's really not. A lot of operational experience and practices from IPv4 don't apply to IPv6. For example, in IPv4 each host has one local net address, and the gateway uses NAT to let it speak with the Internet. Simple and clean. In IPv6 each host has multiple global addresses. But if your global connection goes down, these addresses…
> Then there's IP fragmentation and PMTU that are a burning trash fire. It's not significantly worse on v6 compared to v4. Yes, in theory, you can send v4 packets without DF and helpful routers will fragment for you. In practice, nobody wants that: end points don't like reassembling and may drop fragments; routers have limited cpu budget off the fast path and segment too big is off the fast path, so too big may be dr…
The IPv6 failing was not taking advantage of the new protocol to properly engineer fragmentation handling. But wait, there's more! IPv6 also has braindead extension headers that require routers to do expensive pointer chasing, so packets with them are just dropped in the public Net. So we are stuck with the current mess without any way to fix it.
People are trying: https://datatracker.ietf.org/doc/rfc9268/ but it's futile. It's waaaay too late and too fundamental.