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Ah, but you could do things like put logic in routers like this: "I see you're giving me a 32 bit address. I'm just gonna interpret that as a 64 address padded

Ah, but you could do things like put logic in routers like this: "I see you're giving me a 32 bit address. I'm just gonna interpret that as a 64 address padded left with zeroes." Now router firmware, network stacks, kernel modules -- It's not a full rewrite, just an extension. Now all the bugfixes and workarounds we've written over 50 years still apply. If it were made truly backwards compatible, you'd instantly have tons of adoption because anyone that runs IPv4 is supported and works without any changes. That's way more adoption than IPv6. You wouldn't instantly have to fix all the software again. It would work with old software. This is why hacks like UTF-8 exists. Old systems that understand only ASCII still work fine and communicate well with the systems that deal in UTF-8.

Dagger2 6y ago
You haven't given that anywhere near enough thought. You can't just slap some zeros onto the start of a v4 address and come up with a bigger address space that somehow works with v4 networking code. The problem isn't backwards compatibility, it's forwards compatibility: v4 isn't forwards compatible with larger address spaces, so it's not possible to do what you're suggesting. There are various ways of making a bigger address space with backwards compatibility to v4 though -- and all of the ways which are actually possible and work are already implemented by v6.
CountSessine 6y ago
It's not a full rewrite, just an extension The majority of packets on the internet pass through fairly hard-coded switching chips that probably couldn't be updated to handle this. They can handle IPv6, though. If it were made truly backwards compatible It can't be made backward compatible. Every switch on the internet needs to understand your new extended address scheme otherwise they'll send your packets to a dead-zone somewhere in Uzbekistan. Backward compatibility was never an option. As soon as you add new bits to the address, old routers won't send them to the right place.

Dagger2 6y ago

You haven't given that anywhere near enough thought. You can't just slap some zeros onto the start of a v4 address and come up with a bigger address space that somehow works with v4 networking code. The problem isn't backwards compatibility, it's forwards compatibility: v4 isn't forwards compatible with larger address spaces, so it's not possible to do what you're suggesting. There are various ways of making a bigger address space with backwards compatibility to v4 though -- and all of the ways which are actually possible and work are already implemented by v6.

CountSessine 6y ago

It's not a full rewrite, just an extension The majority of packets on the internet pass through fairly hard-coded switching chips that probably couldn't be updated to handle this. They can handle IPv6, though. If it were made truly backwards compatible It can't be made backward compatible. Every switch on the internet needs to understand your new extended address scheme otherwise they'll send your packets to a dead-zone somewhere in Uzbekistan. Backward compatibility was never an option. As soon as you add new bits to the address, old routers won't send them to the right place.