Cheap ass ISP-managed routers. Got to be lucky for these rubbish bins to even somewhat reliably provide IPv6 connectivity to clients at all, or you run into bullshit like new /64's being assigned every 24 hours, or they may provide IPv6 but not provide any firewall control...
It'd be nice if DNS servers supported this. Save the 64 host bits in the zone and just use whatever 64 prefix bits happen to be issued right now.
Otherwise it makes a strong case for the continued use of "private networks" and the IPv6 ULA mechanism.
Let's please not. Even without inbound reachability, hole punching is significantly easier given globally routeable addresses.
Nor can everyone control whether their connection supports v6, unfortunately.
I’ve also never seen it work for TCP in practice, and not everybody should have to roll their own UDP wrapper for their TCP-expecting application.
The complexity makes sense if you need to transport a lot of data peer-to-peer or the lowest possible latency, but if you don't, you might as well use that coordination server (which outbound-only clients are connecting to) for payload communication as well.
I can't see my neighbors opening ports on their switch. What's a switch, to start with. And what happens when they change provider and switch next month?
It's much easier to tell them: I install two boxes. One is the camera (or whatever), the other one is necessary to make the camera work properly, keep it online, don't switch it off.
