I'm reading Comer's TCP/IP book, where (page 107 of the 4th edition, if you're interested) he states: "The IP checksum is formed by treating the header as a sequence of 16-bit integers (in network ...

The current IP address scheme of 32-bit words is fast becoming inadequate. It would appear that 2 32 = 4 294 967 296 combinations of addresses should be enough for everybody, but in practice this is ...