Randy Bush wrote on 13/09/2021 19:22:
the specs as originally RFCed by the ietf is very telling. for your amusement, take a look at rfc 2450. it took five years of war to get rid of the tla/sla crap. and look at the /64 religion today[0].
architectural decisions were made because of a mixture of actual and perceived problems at the time, but several of the outcomes make little sense now or in some cases, actively cause problems. E.g. using mcast for address resolution because large flat l2 networks were the order of the day, that "privacy addresses" would give privacy, that client self-selected addresses should be the only game in town for auto-addressing (it took years to get any form of dhcp through), that extension headers were a great idea, that "transition mechanisms" would be viable for fundamentally incompatible protocols, etc. That said, it's easy to be critical of design decisions with 25y of hindsight, and even easier to understate how difficult it is to dislodge ipv4 which took 40 years of evolution to cement itself into its current position. Nick