A few key ideas make the Internet and other communication networks possible. This tutorial reviews these ideas that are sometimes cluttered by the numerous implementation details.

The notes are loosely based on an introductory course that I had the pleasure to teach at Berkeley for more than twenty years. On occasions, I taught the course with Kevin Fall, Abhay Parekh, and Shyam Parekh.  I thank them for their input over the years. Special thanks to Shyam for constructive comments on this tutorial.

The intended reader for this tutorial is someone who wants to get a quick sense of how the Internet works but does not want to delve into technical stuff.

We focus on first order ideas: Internet transmits data as packets; the addressing is geographically based; the routing is hierarchical and roughly shortest path; the protocols are arranged in layers; the transport layer supervises the transmissions end to end; the directory service DNS finds the addresses; peer-to-peer makes every user into a server; quality of service could be improved by simple schemes; finally, Wi-Fi devices use a clever scheme to share a common radio channel.

Enjoy! Your comments are welcome.          Berkeley, 3/2007.