Over the last 50 years, we’ve made a lot of progress in developing the Internet from a tiny interconnection of a handful of computers to a worldwide fabric with billions of nodes. During that journey, we’ve learned an enormous amount about how to build networks and the routers that interconnect them. The mistakes that we all made generated some important lessons along the way, for those that chose to learn them. In the beginning, routers were simply generic computers, with Network Interface Cards (NICs) attached to a bus. Figure 1 — Network interface cards attached to a bus. This works ...