To use your example:
> If I want my game console to allow incoming traffic for game matchmaking, I can then do that
My point is that because of the fact that even in IPv6, consumer firewalls will block traffic by default, the company that makes the game would not have designed it to require your console to have special configuration on your firewall. Because this is not something a typical gamer knows how to do.
Instead, companies use UPnP for matchmaking, and UPnP works in both NAT and GUA environments, so what exactly does GUA give you?
You'll have even more problems if you're on CGNAT networks. You're not going to be able to get any of that traffic.
None of this is a problem if each device has its own IP address and its own range of ports to deal with. Every device can have its own :5000, it can know it's public IP address without having to have something see from outside, and with how big assignments usually are it can have dozens of things all listening on a public :5000 all at the same time.
In fact, in IPv6, privacy addresses mean that the address the gaming service observes from my device shouldn’t be assumed to work for other peers, because my device may only be using that address for communication to the gaming service itself. Instead, authors of this software ought to understand that the console itself needs to tell the service “this is the address peers can use to communicate with me”, and thus you may as well just include the port in that call, and then you don’t need to assume port 5000 will work (because if I have 2 XBox’s, they could decide on a different port if another console already has one used.)
It’s just I’m disillusioned with the idea of GUA’s for every device actually solving anything. It solves like 10% of the difficulty of writing good p2p software. All the other problems are still there: firewall config, dynamic IP’s, mobile IP’s, security best practices, shitty middleware boxes not doing the right thing, etc etc etc.
Does IPv6 solve it all? No. Does it solve some of it better than IPv4? Yep. Does it just completely eliminate the need for CGNAT? Yep. It is not a silver bullet to solve all problems, but it does solve some, and for that I'd much rather use it. Because I'd rather just be able to host whatever at home and not need to remember what port is what or rely on proxies looking at other info in the request.
> shitty middleware boxes not doing the right thing
You reduce the need for shitty middleware boxes. I don't need a reverse proxy. I don't need to have a STUN/TURN server. I don't need to randomize ports or worry about running out of ports.
Why solve a problem once properly in the network stack when you can add an ad-hoc workaround to each individual protocol instead?
> the console itself needs to tell the service “this is the address peers can use to communicate with me”, and thus you may as well just include the port in that call, and then you don’t need to assume port 5000 will work
And if you're behind CGNAT so your home router doesn't know what the address and port are, what then?
Not to mention the case of a multiplayer game between two people who live in the same house and a third person who doesn't. That's one that's trivial with IPv6 but difficult with every IPv4-based system I've seen.
> It solves like 10% of the difficulty of writing good p2p software. All the other problems are still there
It all helps. I mean, people mostly manage to play games with each other today, they just get disconnects or random lag every so often. Cutting down on that, even if it was only 10%, would make a lot of lives better.
> Within the port range, enter the starting port and the ending port to forward. For the Nintendo Switch console, this is port 1024 through 65535.
https://en-americas-support.nintendo.com/app/answers/detail/...
Nintendo tells me to forward all high numbered ports to my console. Because obviously we're only going to have a single one in the house.
You do what has already been done for decades. You ship a client premises router that does deny by default inbound and allow all outbound and things behave pretty much the same as they do today with these exact same rules in IPv4.
Network firewalls still exist in a publicly routable network. If I want my game console to allow incoming traffic for game matchmaking, I can then do that. Or have systems that auto configure that. But then I don't have to have multiple devices fighting for a limited port range, each device has more IPs and ports than they could know what to do with.