There was a proposal called SIP that mostly focused on increasing address length (it got published as a historic RFC eventually): https://www.rfc-editor.org/rfc

There was a proposal called SIP that mostly focused on increasing address length (it got published as a historic RFC eventually): https://www.rfc-editor.org/rfc/rfc8507 https://www.rfc-editor.org/rfc/rfc8507 It still had the problem that it made it harder for middleboxen (compared to IPv4) to look at port numbers.