As designer of the multicast extension to the Internet Protocol (IP) and architect of the latest version of IP, IPv6, Stephen Deering's contributions have been crucial to the evolution of the Internet. The multicast feature of IP has enabled robust, automatic configuration of Internet devices, automatic discovery of network resources, and efficient multi-destination delivery of audio, video, and other time-sensitive data. Dr. Deering's design for IP multicast was adopted by the Internet Engineering Task Force (IETF) as a Standard and is a component of all IP implementations today. As a solution to the exhaustion of IP addresses caused by the ongoing growth of the Internet, Dr. Deering designed a “next generation” IP. In addition to providing a much larger address space, the new design incorporated a simpler header structure for higher performance and more compact implementation. It was adopted as IPv6 by the IETF and is now undergoing worldwide deployment. He is currently retired and resides in Vancouver, B.C., Canada.