[growse]

This is the most hilarious "I don't understand anything about the problem, therefore I don't understand how it's hard" comment I've seen this week.

> perhaps we could look at the 240.0.0.0/4 reserved for future use block

What's the current rate of v4 address space consumption? How long will this block last?

> and add more address bytes in the payload or something.

This is, by definition, not backward compatible.

[speedgoose]

I may not have been clear enough in my suggestion. The idea would be to use this unused block as a special block. Not to fill it up with normal IPv4 allocations.

See my suggestion as some kind of NAT-PT at scale. With a better marketing name and user experience.

The problem is indeed hard because no one manage to find a solution at scale since 3 decades.

[shawabawa3]

No matter what change you make, or how you make it, if you are making more than 4B addresses routable then any existing IPv4 device will not be able to route some addresses, so you will have caused a split in the internet

This is a fundamental and unresolvable problem with "making it backwards compatible"

[speedgoose]

Wouldn't NAT be an existing and well used solution to this problem?

[simiones]

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.

[speedgoose]

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.

[superluserdo]

NAT is the problem that IPv6 fixes. Think about the parent comment

>if you are making more than 4B addresses routable then any existing IPv4 device will not be able to route some addresses, so you will have caused a split in the internet

This has basically already happened. We've massively extended IPv4 by stuffing extra address bits into the router's port number, and it means that any two devices behind NATs can't directly route to each other.

[speedgoose]

NAT has been more successful than IPv6 at fixing the same issue, the shortage of IPv4 adresses, but without breaking compatibility (well at the cost of crazy hacks for weird protocols such as FTP).

Not being able to route directly doesn’t seem to be a major issue to me. It for sure require more computing power in routers but also adds some safety and privacy by design.

[growse]

> Not being able to route directly doesn’t seem to be a major issue to me.

Look at the bigger world around you.

I am, right now, involved in a major cloud migration. Having overlapping, constrained RFC1918 space and also having to NAT everything is presenting an enormous set of constraints and risks. It adds literally zero benefit.

Life would be infinitely easier, and we could provide so many more capabilities if everything could just have a routable IP address. Unfortunately, I'm not in charge of our addressing policy.

NAT is an awful, short-sighted hack that causes many more problems than it solves.

[Qwertious]

NAT doesn't fix the issue, it works around it. It means that hosting a home server costs extra money to get a static IP.

[growse]

> The problem is indeed hard because no one manage to find a solution at scale since 3 decades.

The problem is hard because despite everyone's wishes, it's got nothing to do with technology. All migrations are about economics and incentives, IPv6's qualities as a design (it's a long, long way from perfect, but I'd argue that it's good enough) are irrelevant.