Watching the Waist of IP

The Internet protocol architecture has an hourglass shape: a wide variety of applications and end-to-end (upper-layer) protocols are supported by a single, "narrow" protocol called IP, which in turn rests upon a wide variety of network and datalink (lower-layer) protocols. The Internet's enormous flexibility in accommodating new transmission technologies and new applications, and its ability to serve as the convergence platform for data, telephony, TV, and other media, depend on this hourglass design. However, as the Internet has grown, the waist of the hourglass has spread. In this talk, I review the evolution of the IP layer of the Internet, discuss the consequences of the changes, and speculate on the future shape of IP.