So much of what “everyone knows” about network protocols is actually false. For instance, why do we need both Ethernet and IP? The “obvious” answer is that IP is “layer 3” and Ethernet is “layer 2”, but in fact, once Ethernet stopped being a way for a few hundred nodes to share a single wire, and instead became a network of point-to-point links with switches forwarding between the links, “Ethernet” today should really be called a layer 3 protocol. So, why can’t we get rid of switches and connect all links with IP? Or why can’t we replace IP routers with Ethernet switches? Another topic is whether IP was the best layer 3 protocol, and whether IPv6 is simply a new version of IP, whereas, if the world had converted to CLNP (a 20-byte layer 3 protocol) in 1992, it would have been a major disruption to the Internet.