Even if we accept that NAT is the right solution, it still is pretty limited in how far it has been able to extend the address space, since port numbers only give you two extra bytes of address space. And there are no further extra bytes to stuff somehwere else in a TCP or UDP packet header.
Of course, we could extend the address space by further breaking the layering of routes, and baking in support for higher layer protocols into routers. We can certainly stuff more address information in HTTP headers, so the web could be extended to essentially arbitrary size by simply requiring routers to look not just at source and destination IPs and source/dest TCP/UDP port numbers, but also client and server HTTP headers. SIP looks a lot like HTTP, so the same solution could work there. TLS already has support for additional headers, so we could also do extra NAT at that layer.
Hell, AWS could then use a single IPv4, and just rely on HTTP/SIP headers or TLS extension headers to know the actual destination! Of course, if you want to run another L7 protocol, tough luck - tunneling it is for you.
Yes I agree you would need to tunnel because the headers aren’t big enough.
If I had to guess the futur, the industry will most likely go towards something like few expensive IPv4 owned by major cloud and internet providers and crazy recursive NAT setups everywhere. Because that works without breaking stuff.
Of course, we could extend the address space by further breaking the layering of routes, and baking in support for higher layer protocols into routers. We can certainly stuff more address information in HTTP headers, so the web could be extended to essentially arbitrary size by simply requiring routers to look not just at source and destination IPs and source/dest TCP/UDP port numbers, but also client and server HTTP headers. SIP looks a lot like HTTP, so the same solution could work there. TLS already has support for additional headers, so we could also do extra NAT at that layer.
Hell, AWS could then use a single IPv4, and just rely on HTTP/SIP headers or TLS extension headers to know the actual destination! Of course, if you want to run another L7 protocol, tough luck - tunneling it is for you.