We're almost out of IPv4 addresses, yet IPv6 deployment is still very, very slow. This is a recipe for disaster. I'm talking End of Internet predicted, film at 11 scale disaster. Something must be done. Steps must be taken.
I humbly suggest that the solution is really quite simple: re-use IPv4 addresses. I don't mean reclaiming IP addresses which have been allocated but are not actually being used. That is the kind of solution which sounds good and righteous to say but is completely unworkable in practice. Instead, I mean to simply issue the same IP address to multiple people.
"How could that possibly work?" people might ask. Go ahead, ask it... I'm glad that you asked, because I have a ready-made explanation waiting. We will leverage a solution to a similar problem which has scaled tremendously well over the last several decades: email addresses.
On early email systems like AOL, addresses had to be unique. This led to such ridiculous conventions as appending a number to the end of a popular address, like CompuGuy112673 (because really, everybody wants to have an email address like CompuGuy). The beauty of Internet email addressing is in breaking them up into a federated system, so firstname.lastname@example.org and email@example.com can simultaneously exist.
Therefore I propose to use this same solution for IP addressing. We will allow each Autonomous System to maintain its own IP address space. The same IP address can simultaneously exist within multiple ASNs. We are effectively adding a level of indirection to the destination in the IP header. Disambiguating the actual destination will be done via a new IP option.
Binary encoding of protocol headers is now passé. Therefore our new IP option is ASCII encoded, which also allows us to avoid the discussion about how Little Endian CPUs have won and all headers should be LE instead of BE. The content of the option is the destination IP address, followed by the '@' sign, followed by the decimal Autonomous System Number where the recipient can be reached. For example, a destination of 188.8.131.52 within the Level 3 network space would be "184.108.40.206@3356" using Level3's primary ASN of 3356.
By my reading of the IP spec the option field can be up to 40 bytes, while an IP@ASN encoding could require up to 15 bytes for the IP address, 1 byte for the @ symbol, and could handle billions of IP namespaces using only 13 more bytes to encode a 32 bit ASN. So, we should be good to go.
Updates to the DNS A record and all the application code which looks up IP addresses is left as an exercise for the reader.
For historical reasons, this new option is referred to as the BangIP option. An earlier version of this system used bang-separated IP addresses as a source routing path. That portion of the proposal has been deprecated, but we retain the name for its sentimental value.