There are multiple LAN protocols below the IP layer and multiple transport protocols above, but IP itself stands alone. The Internet is essentially the IP Internet. If you want to run your own LAN protocol somewhere, or if you want to run your own transport protocol, the Internet backbone will still work just fine for you. But if you want to change the IP layer, you will encounter difficulty. (Just talk to the IPv6 people, or the IP-multicasting or IP-reservations groups.)