[bArray]

Would have been awfully nice to have a reserved bit in hindsight. 7 bit ASCII was an amazing accident. (Maybe it wasn't, time to brush up on my history...)

[dogecoinbase]

We do/did! Class E space (240.0.0.0/4) exists and is entirely unused. There was a proposal in 2008-ish to try and convert it to regular IP space for allocation, but the agreement was that it would be too much work (many stacks default drop class E packets) and we should focus on transitioning to IPv6.

[bArray]

Thanks, I wasn't really aware of this. Class E wouldn't add too much to the IP address space if I understand this correctly?

I was thinking more along the lines of a bit being flipped would mean the next 8 bytes are an IP and not four, for example.

From my limited understanding, I don't think they reserved a bit in the address space?

[DaiPlusPlus]

If you're advocating for the introduction of variable-length IP addresses then it would have been a nightmare - packet-switching is often done in hardware and that level of complexity would have only added trouble.

[bArray]

Any harder than implementing IPv6 in hardware? I'm talking about an adjustment that would keep older machines talking to older addresses, whilst newer machines could implement extended IPv4, for example. From my potential ignorance, I'm not sure how that would be more difficult?

I think it's theoretical of course, I don't believe there is a reserved bit in the IPv4 range.